]> git.saurik.com Git - apple/security.git/blobdiff - OSX/sec/SOSCircle/SecureObjectSync/SOSEngine.c
Security-57336.1.9.tar.gz
[apple/security.git] / OSX / sec / SOSCircle / SecureObjectSync / SOSEngine.c
diff --git a/OSX/sec/SOSCircle/SecureObjectSync/SOSEngine.c b/OSX/sec/SOSCircle/SecureObjectSync/SOSEngine.c
new file mode 100644 (file)
index 0000000..efa578a
--- /dev/null
@@ -0,0 +1,2308 @@
+/*
+ * Copyright (c) 2012-2015 Apple Inc. All Rights Reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ * 
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ * 
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ * 
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+
+/*
+ * SOSEngine.c -  Implementation of a secure object syncing engine
+ */
+
+#include <Security/SecureObjectSync/SOSChangeTracker.h>
+#include <Security/SecureObjectSync/SOSEngine.h>
+#include <Security/SecureObjectSync/SOSDigestVector.h>
+#include <Security/SecureObjectSync/SOSInternal.h>
+#include <Security/SecureObjectSync/SOSPeer.h>
+#include <Security/SecureObjectSync/SOSViews.h>
+#include <Security/SecureObjectSync/SOSBackupEvent.h>
+#include <corecrypto/ccder.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <utilities/array_size.h>
+#include <utilities/SecCFCCWrappers.h>
+#include <utilities/SecCFError.h>
+#include <utilities/SecCFRelease.h>
+#include <utilities/SecCFWrappers.h>
+#include <utilities/der_plist.h>
+#include <utilities/der_plist_internal.h>
+#include <utilities/debugging.h>
+#include <utilities/iCloudKeychainTrace.h>
+#include <utilities/SecCoreCrypto.h>
+#include <utilities/SecFileLocations.h>
+#include <AssertMacros.h>
+#include <CoreFoundation/CoreFoundation.h>
+
+#include <securityd/SecItemServer.h>    // TODO: We can't leave this here.
+#include <securityd/SOSCloudCircleServer.h> // TODO: We can't leave this here.
+#include <Security/SecItem.h>           // TODO: We can't leave this here.
+#include <Security/SecItemPriv.h>       // TODO: We can't leave this here.
+#include <securityd/SecItemSchema.h>
+#include <securityd/iCloudTrace.h>
+
+#include <CoreFoundation/CFURL.h>
+
+//
+// MARK: SOSEngine The Keychain database with syncable keychain support.
+//
+
+// Key in dataSource for general engine state file.
+// This file only has digest entries in it, no manifests.
+static const CFStringRef kSOSEngineState = CFSTR("engine-state");
+
+// Keys in state dictionary
+static CFStringRef kSOSEngineManifestCacheKey = CFSTR("manifestCache");
+static CFStringRef kSOSEnginePeerStateKey = CFSTR("peerState");
+static CFStringRef kSOSEnginePeerIDsKey = CFSTR("peerIDs");
+static CFStringRef kSOSEngineIDKey = CFSTR("id");
+static CFStringRef kSOSEngineTraceDateKey = CFSTR("traceDate");
+
+/* SOSEngine implementation. */
+struct __OpaqueSOSEngine {
+    CFRuntimeBase _base;
+    SOSDataSourceRef dataSource;
+    CFStringRef myID;                       // My peerID in the circle
+    // We need to address the issues of corrupt keychain items
+    SOSManifestRef unreadable;              // Possibly by having a set of unreadable items, to which we
+    // add any corrupted items in the db that have yet to be deleted.
+    // This happens if we notce corruption during a (read only) query.
+    // We would also perma-subtract unreadable from manifest whenever
+    // anyone asked for manifest.  This result would be cached in
+    // The manifestCache below, so we just need a key into the cache
+    CFDataRef localMinusUnreadableDigest;   // or a digest (CFDataRef of the right size).
+
+    CFMutableDictionaryRef manifestCache;       // digest -> ( refcount, manifest )
+    //CFMutableDictionaryRef peerState;         // peerId -> mutable array of digests
+    CFMutableDictionaryRef peerMap;             // peerId -> SOSPeerRef
+    CFDictionaryRef viewNameSet2ChangeTracker;  // CFSetRef of CFStringRef -> SOSChangeTrackerRef
+    CFDictionaryRef viewName2ChangeTracker;     // CFStringRef -> SOSChangeTrackerRef
+    CFArrayRef peerIDs;
+    CFDateRef lastTraceDate;                    // Last time we did a CloudKeychainTrace
+
+    dispatch_queue_t queue;                     // Engine queue
+
+    dispatch_queue_t syncCompleteQueue;             // Non-retained queue for async notificaion
+    CFMutableDictionaryRef syncCompleteListeners;   // Map from PeerID->notification block
+};
+
+static bool SOSEngineLoad(SOSEngineRef engine, CFErrorRef *error);
+static CFStringRef SOSPeerIDArrayCreateString(CFArrayRef peerIDs) {
+    return peerIDs ? CFStringCreateByCombiningStrings(kCFAllocatorDefault, peerIDs, CFSTR(" ")) : CFSTR("");
+}
+static CFStringRef SOSEngineCopyFormattingDesc(CFTypeRef cf, CFDictionaryRef formatOptions) {
+    SOSEngineRef engine = (SOSEngineRef)cf;
+    CFStringRef tpDesc = SOSPeerIDArrayCreateString(engine->peerIDs);
+    CFStringRef desc = CFStringCreateWithFormat(kCFAllocatorDefault, formatOptions, CFSTR("<Engine %@ peers %@ MC[%d] PS[%d]>"), engine->myID, tpDesc, engine->manifestCache ? (int)CFDictionaryGetCount(engine->manifestCache) : 0, engine->peerMap ? (int)CFDictionaryGetCount(engine->peerMap) : 0);
+    CFReleaseSafe(tpDesc);
+    return desc;
+ }
+static CFStringRef SOSEngineCopyDebugDesc(CFTypeRef cf) {
+    return SOSEngineCopyFormattingDesc(cf, NULL);
+ }
+static dispatch_queue_t sEngineQueue;
+static CFDictionaryRef sEngineMap;
+CFGiblisWithFunctions(SOSEngine, NULL, NULL, NULL, NULL, NULL, SOSEngineCopyFormattingDesc, SOSEngineCopyDebugDesc, NULL, NULL, ^{
+    sEngineQueue = dispatch_queue_create("SOSEngine queue", DISPATCH_QUEUE_SERIAL);
+    sEngineMap = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+});
+
+#define _LOG_RAW_MESSAGES 0
+void logRawMessage(CFDataRef message, bool sending, uint64_t seqno)
+{
+#if _LOG_RAW_MESSAGES
+    CFStringRef hexMessage = NULL;
+    if (message) {
+        hexMessage = CFDataCopyHexString(message);
+        if (sending)
+            secnoticeq("engine", "%s RAW%1d %@", sending ? "send" : "recv", seqno?2:0, hexMessage);
+        else
+            secnoticeq("engine", "%s RAWx %@", sending ? "send" : "recv", hexMessage);  // we don't know vers of received msg here
+    }
+    CFReleaseSafe(hexMessage);
+#endif
+}
+//
+// Peer state layout.  WRONG! It's an array now
+// The peer state is an array.
+// The first element of the array is a dictionary with any number of keys and
+// values in it (for future expansion) such as changing the digest size or type
+// or remembering boolean flags for a peers sake.
+// The next three are special in that they are manifest digests with special
+// meaning and rules as to how they are treated (These are dynamically updated
+// based on database activity so they have a fully history of all changes made
+// to the local db. The first is the manifest representing the pendingObjects
+// to send to the other peer.  This is normally only ever appending to, and in
+// particular with transactions originating from the Keychain API that affect
+// syncable items will need to add the new objects digests to the pendingObjects list
+// while adding the digests of any tombstones encountered to the extra list.
+
+CFStringRef SOSEngineGetMyID(SOSEngineRef engine) {
+    // TODO: this should not be needed
+    return engine->myID;
+}
+
+// TEMPORARY: Get the list of IDs for cleanup, this shouldn't be used instead it should iterate KVS.
+CFArrayRef SOSEngineGetPeerIDs(SOSEngineRef engine) {
+    return engine->peerIDs;
+}
+
+void SOSEngineClearCache(SOSEngineRef engine){
+    CFReleaseNull(engine->manifestCache);
+    CFReleaseNull(engine->localMinusUnreadableDigest);
+    dispatch_release(engine->queue);                  
+}
+
+static SOSPeerRef SOSEngineCopyPeerWithMapEntry_locked(SOSEngineRef engine, CFStringRef peerID, CFTypeRef mapEntry, CFErrorRef *error) {
+    SOSPeerRef peer = NULL;
+    if (mapEntry && CFGetTypeID(mapEntry) == SOSPeerGetTypeID()) {
+        // The mapEntry is an SOSPeer, so we're done.
+        peer = (SOSPeerRef)CFRetain(mapEntry);
+    } else {
+        // The mapEntry is a peerState, attempt to initialize a new
+        // peer iff peerID is in the set of trusted peerIDs
+        if (engine->peerIDs && CFArrayContainsValue(engine->peerIDs, CFRangeMake(0, CFArrayGetCount(engine->peerIDs)), peerID)) {
+            CFErrorRef localError = NULL;
+            peer = SOSPeerCreateWithState(engine, peerID, mapEntry, &localError);
+            if (!peer) {
+                secerror("error inflating peer: %@: %@ from state: %@", peerID, localError, mapEntry);
+                CFReleaseNull(localError);
+                peer = SOSPeerCreateWithState(engine, peerID, NULL, error);
+            }
+            if (peer) {
+                // Replace the map entry with the inflated peer.
+                CFDictionarySetValue(engine->peerMap, peerID, peer);
+            }
+        } else {
+            SOSErrorCreate(kSOSErrorPeerNotFound, error, NULL, CFSTR("peer: %@ is untrusted inflating not allowed"), peerID);
+        }
+    }
+    return peer;
+}
+
+static SOSPeerRef SOSEngineCopyPeerWithID_locked(SOSEngineRef engine, CFStringRef peerID, CFErrorRef *error) {
+    CFTypeRef mapEntry = CFDictionaryGetValue(engine->peerMap, peerID);
+    SOSPeerRef peer = NULL;
+    if (mapEntry) {
+        peer = SOSEngineCopyPeerWithMapEntry_locked(engine, peerID, mapEntry, error);
+    } else {
+        peer = NULL;
+        SOSErrorCreate(kSOSErrorPeerNotFound, error, NULL, CFSTR("peer: %@ not found"), peerID);
+    }
+    return peer;
+}
+
+struct SOSEngineWithPeerContext {
+    SOSEngineRef engine;
+    void (^with)(SOSPeerRef peer);
+};
+
+static void SOSEngineWithPeerMapEntry_locked(const void *peerID, const void *mapEntry, void *context) {
+    struct SOSEngineWithPeerContext *ewp = context;
+    SOSPeerRef peer = SOSEngineCopyPeerWithMapEntry_locked(ewp->engine, peerID, mapEntry, NULL);
+    if (peer) {
+        ewp->with(peer);
+        CFRelease(peer);
+    }
+}
+
+static void SOSEngineForEachPeer_locked(SOSEngineRef engine, void (^with)(SOSPeerRef peer)) {
+    struct SOSEngineWithPeerContext ewp = { .engine = engine, .with = with };
+    CFDictionaryRef peerMapCopy = CFDictionaryCreateCopy(NULL, engine->peerMap);
+    CFDictionaryApplyFunction(peerMapCopy, SOSEngineWithPeerMapEntry_locked, &ewp);
+    CFRelease(peerMapCopy);
+}
+
+static void SOSEngineWithBackupPeerMapEntry_locked(const void *peerID, const void *mapEntry, void *context) {
+    struct SOSEngineWithPeerContext *ewp = context;
+    // v0 backup peer is always in map but we only consider it a backup peer if it has a keybag.
+    if (SOSPeerMapEntryIsBackup(mapEntry)) {
+        SOSPeerRef peer = SOSEngineCopyPeerWithMapEntry_locked(ewp->engine, peerID, mapEntry, NULL);
+        if (peer) {
+            ewp->with(peer);
+            CFRelease(peer);
+        }
+    }
+}
+
+static void SOSEngineForEachBackupPeer_locked(SOSEngineRef engine, void (^with)(SOSPeerRef peer)) {
+    struct SOSEngineWithPeerContext ewp = { .engine = engine, .with = with };
+    CFDictionaryRef peerMapCopy = CFDictionaryCreateCopy(NULL, engine->peerMap);
+    CFDictionaryApplyFunction(peerMapCopy, SOSEngineWithBackupPeerMapEntry_locked, &ewp);
+    CFRelease(peerMapCopy);
+}
+
+//
+// Manifest cache
+//
+SOSManifestRef SOSEngineGetManifestForDigest(SOSEngineRef engine, CFDataRef digest) {
+    if (!engine->manifestCache || !digest) return NULL;
+    SOSManifestRef manifest = (SOSManifestRef)CFDictionaryGetValue(engine->manifestCache, digest);
+    if (!manifest) return NULL;
+    if (CFGetTypeID(manifest) != SOSManifestGetTypeID()) {
+        secerror("dropping corrupt manifest for %@ from cache", digest);
+        CFDictionaryRemoveValue(engine->manifestCache, digest);
+        return NULL;
+    }
+    
+    return manifest;
+}
+
+void SOSEngineAddManifest(SOSEngineRef engine, SOSManifestRef manifest) {
+    CFDataRef digest = SOSManifestGetDigest(manifest, NULL);
+    if (digest) {
+        if (!engine->manifestCache)
+            engine->manifestCache = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+        CFDictionaryAddValue(engine->manifestCache, digest, manifest);
+    }
+}
+
+CFDataRef SOSEnginePatchRecordAndCopyDigest(SOSEngineRef engine, SOSManifestRef base, SOSManifestRef removals, SOSManifestRef additions, CFErrorRef *error) {
+    CFDataRef digest = NULL;
+    SOSManifestRef manifest = SOSManifestCreateWithPatch(base, removals, additions, error);
+    if (manifest) {
+        SOSEngineAddManifest(engine, manifest);
+        digest = CFRetainSafe(SOSManifestGetDigest(manifest, NULL));
+    }
+    CFReleaseSafe(manifest);
+    return digest;
+}
+
+SOSManifestRef SOSEngineCopyPersistedManifest(SOSEngineRef engine, CFDictionaryRef persisted, CFStringRef key) {
+    return CFRetainSafe(SOSEngineGetManifestForDigest(engine, asData(CFDictionaryGetValue(persisted, key), NULL)));
+}
+
+CFMutableArrayRef SOSEngineCopyPersistedManifestArray(SOSEngineRef engine, CFDictionaryRef persisted, CFStringRef key, CFErrorRef *error) {
+    CFMutableArrayRef manifests = NULL;
+    CFArrayRef digests = NULL;
+    CFDataRef digest;
+    if (asArrayOptional(CFDictionaryGetValue(persisted, key), &digests, error))
+        manifests = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+    if (digests) CFArrayForEachC(digests, digest) {
+        SOSManifestRef manifest = SOSEngineGetManifestForDigest(engine, digest);
+        if (manifest)
+            CFArrayAppendValue(manifests, manifest);
+    }
+    return manifests;
+}
+
+static CFDictionaryRef SOSEngineCopyEncodedManifestCache_locked(SOSEngineRef engine, CFErrorRef *error) {
+    CFMutableDictionaryRef mfc = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    SOSEngineForEachPeer_locked(engine, ^(SOSPeerRef peer) {
+        SOSPeerAddManifestsInUse(peer, mfc);
+    });
+    return mfc;
+}
+
+#if 0
+static bool SOSEngineGCManifests_locked(SOSEngineRef engine, CFErrorRef *error) {
+    __block struct SOSDigestVector mdInCache = SOSDigestVectorInit;
+    __block struct SOSDigestVector mdInUse = SOSDigestVectorInit;
+    struct SOSDigestVector mdUnused = SOSDigestVectorInit;
+    struct SOSDigestVector mdMissing = SOSDigestVectorInit;
+    bool ok = true;
+
+    SOSEngineForEachPeer_locked(engine, ^(SOSPeerRef peer) {
+        SOSPeerMarkDigestsInUse(peer, &mdInUse);
+    });
+
+    if (engine->manifestCache) {
+        CFDictionaryForEach(engine->manifestCache, ^(const void *key, const void *value) {
+            CFDataRef digest = (CFDataRef)key;
+            if (isData(digest))
+                SOSDigestVectorAppend(&mdInCache, CFDataGetBytePtr(digest));
+        });
+        
+        // Delete unused manifests.
+        SOSDigestVectorDiff(&mdInCache, &mdInUse, &mdUnused, &mdMissing);
+        SOSManifestRef unused = SOSManifestCreateWithDigestVector(&mdUnused, NULL);
+        SOSManifestForEach(unused, ^(CFDataRef digest, bool *stop) {
+            if (digest)
+                CFDictionaryRemoveValue(engine->manifestCache, digest);
+        });
+        CFReleaseSafe(unused);
+    }
+
+    SOSDigestVectorFree(&mdInCache);
+    SOSDigestVectorFree(&mdInUse);
+    SOSDigestVectorFree(&mdUnused);
+    SOSDigestVectorFree(&mdMissing);
+    return ok;
+}
+#endif
+
+//
+// End of Manifest cache
+//
+
+static bool SOSEngineGCPeerState_locked(SOSEngineRef engine, CFErrorRef *error) {
+    bool ok = true;
+    
+    //require_quiet(ok = SOSEngineGCManifests_locked(engine, error), exit);
+
+//exit:
+    return ok;
+}
+
+static CFMutableDictionaryRef SOSEngineCopyPeerState_locked(SOSEngineRef engine, CFErrorRef *error) {
+    CFMutableDictionaryRef peerState = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    CFDictionaryForEach(engine->peerMap, ^(const void *key, const void *value) {
+        CFDictionaryRef state = NULL;
+        if (value && CFGetTypeID(value) == SOSPeerGetTypeID()) {
+            CFErrorRef localError = NULL;
+            // Inflated peer
+            state = SOSPeerCopyState((SOSPeerRef)value, &localError);
+            if (!state)
+                secnotice("engine", "%@ failed to encode peer: %@", key, localError);
+            CFReleaseNull(localError);
+            // TODO: Potentially replace inflated peer with deflated peer in peerMap
+        } else if (value) {
+            // We have a deflated peer.
+            state = CFRetainSafe(value);
+        }
+
+        if (state) {
+            CFDictionarySetValue(peerState, key, state);
+            CFReleaseSafe(state);
+        }
+    });
+    return peerState;
+}
+
+static CFDataRef SOSEngineCopyState(SOSEngineRef engine, CFErrorRef *error) {
+    CFDataRef der = NULL;
+    CFMutableDictionaryRef state = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    if (engine->myID) CFDictionarySetValue(state, kSOSEngineIDKey, engine->myID);
+    if (engine->peerIDs) CFDictionarySetValue(state, kSOSEnginePeerIDsKey, engine->peerIDs);
+    if (engine->lastTraceDate) CFDictionarySetValue(state, kSOSEngineTraceDateKey, engine->lastTraceDate);
+    CFTypeRef peerState = SOSEngineCopyPeerState_locked(engine, error);
+    if (peerState) CFDictionarySetValue(state, kSOSEnginePeerStateKey, peerState);
+    CFReleaseSafe(peerState);
+    CFDictionaryRef mfc = SOSEngineCopyEncodedManifestCache_locked(engine, error);
+    if (mfc) {
+        CFDictionarySetValue(state, kSOSEngineManifestCacheKey, mfc);
+        CFReleaseSafe(mfc);
+    }
+    der = CFPropertyListCreateDERData(kCFAllocatorDefault, state, error);
+    CFReleaseSafe(state);
+    secnotice("engine", "%@", engine);
+    return der;
+}
+
+static bool SOSEngineSave(SOSEngineRef engine, SOSTransactionRef txn, CFErrorRef *error) {
+    CFDataRef derState = SOSEngineCopyState(engine, error);
+    bool ok = derState && SOSDataSourceSetStateWithKey(engine->dataSource, txn, kSOSEngineState, kSecAttrAccessibleAlways, derState, error);
+    CFReleaseSafe(derState);
+    return ok;
+}
+
+static SOSManifestRef SOSEngineCreateManifestWithViewNameSet_locked(SOSEngineRef engine, CFSetRef viewNameSet, CFErrorRef *error) {
+    // TODO: Potentially tell all changeTrackers to track manifests (    //forall ct do SOSChangeTrackerSetConcrete(ct, true);
+    // and read the entire dataSource and pass all objects though the filter here, instead of
+    // forcing the datasource to be able to do "smart" queries
+    return SOSDataSourceCopyManifestWithViewNameSet(engine->dataSource, viewNameSet, error);
+}
+
+static SOSChangeTrackerRef SOSEngineCopyChangeTrackerWithViewNameSet_locked(SOSEngineRef engine, CFSetRef viewNameSet, CFErrorRef *error) {
+    SOSChangeTrackerRef ct = (SOSChangeTrackerRef)CFDictionaryGetValue(engine->viewNameSet2ChangeTracker, viewNameSet);
+    if (!ct)
+        SOSErrorCreate(kSOSErrorPeerNotFound, error, NULL, CFSTR("no change tracker for view set %@"), viewNameSet);
+    return CFRetainSafe(ct);
+}
+
+static SOSManifestRef SOSEngineCopyManifestWithViewNameSet_locked(SOSEngineRef engine, CFSetRef viewNameSet, CFErrorRef *error) {
+    SOSChangeTrackerRef ct = SOSEngineCopyChangeTrackerWithViewNameSet_locked(engine, viewNameSet, error);
+    if (!ct)
+        return NULL;
+
+    SOSManifestRef manifest = SOSChangeTrackerCopyManifest(ct, NULL);
+    if (!manifest) {
+        manifest = SOSEngineCreateManifestWithViewNameSet_locked(engine, viewNameSet, error); // Do the SQL query
+        SOSChangeTrackerSetManifest(ct, manifest);
+    }
+    CFReleaseSafe(ct);
+    return manifest;
+}
+
+SOSManifestRef SOSEngineCopyLocalPeerManifest_locked(SOSEngineRef engine, SOSPeerRef peer, CFErrorRef *error) {
+    return SOSEngineCopyManifestWithViewNameSet_locked(engine, SOSPeerGetViewNameSet(peer), error);
+}
+
+#define withViewAndBackup(VIEW)  do { with(VIEW); if (!isTomb) with(VIEW ## _tomb); } while(0)
+
+
+// Invoke with once for each view an object is in.
+// TODO: Move this function into the DataSource
+static void SOSEngineObjectWithView(SOSEngineRef engine, SOSObjectRef object, void (^with)(CFStringRef view)) {
+    // Filter items into v0 only view here
+    SecDbItemRef item = (SecDbItemRef)object; // TODO: Layer violation, breaks tests
+    if (isDictionary(object)) {
+        CFTypeRef isTombValue = CFDictionaryGetValue((CFDictionaryRef)object, kSecAttrTombstone);
+        bool isTomb = isTombValue && CFBooleanGetValue(isTombValue);
+        // We are in the test just assume v0 and v2 views.
+        withViewAndBackup(kSOSViewKeychainV0);
+    } else if (SecDbItemIsSyncableOrCorrupted(item)) {
+        const SecDbClass *iclass = SecDbItemGetClass(item);
+        CFTypeRef pdmn = SecDbItemGetCachedValueWithName(item, kSecAttrAccessible);
+        if ((iclass == &genp_class || iclass == &inet_class || iclass == &keys_class || iclass == &cert_class)
+            && isString(pdmn)
+            && (CFEqual(pdmn, kSecAttrAccessibleWhenUnlocked)
+                || CFEqual(pdmn, kSecAttrAccessibleAfterFirstUnlock)
+                || CFEqual(pdmn, kSecAttrAccessibleAlways)
+                || CFEqual(pdmn, kSecAttrAccessibleWhenUnlockedThisDeviceOnly)
+                || CFEqual(pdmn, kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly)
+                || CFEqual(pdmn, kSecAttrAccessibleAlwaysThisDeviceOnly)))
+        {
+            CFTypeRef tomb = SecDbItemGetCachedValueWithName(item, kSecAttrTombstone);
+            char cvalue = 0;
+            bool isTomb = (isNumber(tomb) && CFNumberGetValue(tomb, kCFNumberCharType, &cvalue) && cvalue == 1);
+            CFTypeRef viewHint = SecDbItemGetCachedValueWithName(item, kSecAttrSyncViewHint);
+            if (viewHint == NULL) {
+                if (iclass == &cert_class) {
+                    withViewAndBackup(kSOSViewOtherSyncable);
+                } else {
+                    if (!SecDbItemGetCachedValueWithName(item, kSecAttrTokenID)) {
+                        withViewAndBackup(kSOSViewKeychainV0);
+                    }
+                    CFTypeRef agrp = SecDbItemGetCachedValueWithName(item, kSecAttrAccessGroup);
+                    if (iclass == &keys_class && CFEqualSafe(agrp, CFSTR("com.apple.security.sos"))) {
+                        withViewAndBackup(kSOSViewiCloudIdentity);
+                    } else if (CFEqualSafe(agrp, CFSTR("com.apple.cfnetwork"))) {
+                        withViewAndBackup(kSOSViewAutofillPasswords);
+                    } else if (CFEqualSafe(agrp, CFSTR("com.apple.safari.credit-cards"))) {
+                        withViewAndBackup(kSOSViewSafariCreditCards);
+                    } else if (iclass == &genp_class) {
+                        if (CFEqualSafe(agrp, CFSTR("apple")) &&
+                            CFEqualSafe(SecDbItemGetCachedValueWithName(item, kSecAttrService), CFSTR("AirPort"))) {
+                            withViewAndBackup(kSOSViewWiFi);
+                        } else if (CFEqualSafe(agrp, CFSTR("com.apple.sbd"))) {
+                            withViewAndBackup(kSOSViewBackupBagV0);
+                        } else {
+                            withViewAndBackup(kSOSViewOtherSyncable); // (genp)
+                        }
+                    } else {
+                        withViewAndBackup(kSOSViewOtherSyncable); // (inet || keys)
+                    }
+                }
+            } else {
+                with(viewHint);
+                if (!isTomb) {
+                    CFStringRef viewHintTomb = CFStringCreateWithFormat(kCFAllocatorDefault, NULL, CFSTR("%@-tomb"), viewHint);
+                    if (viewHintTomb) {
+                        with(viewHintTomb);
+                        CFRelease(viewHintTomb);
+                    }
+                }
+            }
+        }
+    } else {
+        // TODO: general queries
+#if 0
+        SOSViewRef view;
+        CFArrayForEachC(engine->views, view) {
+            bool inView = SOSViewQueryMatchItem(view, item);
+            if (inView) {
+                CFStringRef viewName = SOSViewCopyName(view);
+                with(viewName);
+                CFReleaseSafe(viewName);
+            }
+        }
+#endif
+    }
+}
+
+//
+// SOSChangeMapper - Helper for SOSEngineUpdateChanges_locked
+//
+struct SOSChangeMapper {
+    SOSEngineRef engine;
+    SOSTransactionRef txn;
+    SOSDataSourceTransactionPhase phase;
+    SOSDataSourceTransactionSource source;
+    CFMutableDictionaryRef ct2changes;
+};
+
+static void SOSChangeMapperInit(struct SOSChangeMapper *cm, SOSEngineRef engine, SOSTransactionRef txn, SOSDataSourceTransactionPhase phase, SOSDataSourceTransactionSource source) {
+    cm->engine = engine;
+    cm->txn = txn;
+    cm->phase = phase;
+    cm->source = source;
+    cm->ct2changes = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+}
+
+static void SOSChangeMapperFree(struct SOSChangeMapper *cm) {
+    CFReleaseSafe(cm->ct2changes);
+}
+
+static void SOSChangeMapperAppendObject(struct SOSChangeMapper *cm, SOSChangeTrackerRef ct, bool isAdd, CFTypeRef object) {
+    CFMutableArrayRef changes = (CFMutableArrayRef)CFDictionaryGetValue(cm->ct2changes, ct);
+    if (!changes) {
+        changes = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+        CFDictionarySetValue(cm->ct2changes, ct, changes);
+        CFReleaseSafe(changes);
+    }
+    isAdd ? SOSChangesAppendAdd(changes, object) : SOSChangesAppendDelete(changes, object);
+}
+
+static bool SOSChangeMapperIngestChange(struct SOSChangeMapper *cm, bool isAdd, CFTypeRef change) {
+    bool someoneCares = false;
+    if (isData(change)) {
+        // TODO: Reenable assertion once the tests have been updated
+        //assert(!isAdd);
+        // We got a digest for a deleted object. Our dataSource probably couldn't find
+        // an object with this digest, probably because it went missing, or it was
+        // discovered to be corrupted.
+        // Tell all our changeTrackers about this digest since we don't know who might need it.
+        CFDictionaryForEach(cm->engine->viewNameSet2ChangeTracker, ^(const void *viewNameSet, const void *ct) {
+            SOSChangeMapperAppendObject(cm, (SOSChangeTrackerRef)ct, isAdd, change);
+        });
+        someoneCares = CFDictionaryGetCount(cm->engine->viewNameSet2ChangeTracker);
+    } else {
+        // We got an object let's figure out which views it's in and schedule it for
+        // delivery to all changeTrackers interested in any of those views.
+        SOSObjectRef object = (SOSObjectRef)change;
+        CFMutableSetRef changeTrackerSet = CFSetCreateMutableForCFTypes(kCFAllocatorDefault);
+        // First gather all the changeTrackers interested in this object (eleminating dupes by collecting them in a set)
+        SOSEngineObjectWithView(cm->engine, object, ^(CFStringRef viewName) {
+            const void *ctorset = CFDictionaryGetValue(cm->engine->viewName2ChangeTracker, viewName);
+            if (isSet(ctorset)) {
+                CFSetForEach((CFSetRef)ctorset, ^(const void *ct) { CFSetAddValue(changeTrackerSet, ct); });
+            } else if (ctorset) {
+                CFSetAddValue(changeTrackerSet, ctorset);
+            }
+        });
+        // Then append the object to the changes array in the ct2changes dictionary keyed by viewSet
+        CFSetForEach(changeTrackerSet, ^(const void *ct) {
+            SOSChangeMapperAppendObject(cm, (SOSChangeTrackerRef)ct, isAdd, object);
+        });
+        someoneCares = CFSetGetCount(changeTrackerSet);
+        CFReleaseSafe(changeTrackerSet);
+    }
+    return someoneCares;
+}
+
+static bool SOSChangeMapperSend(struct SOSChangeMapper *cm, CFErrorRef *error) {
+    __block bool ok = true;
+    CFDictionaryForEach(cm->ct2changes, ^(const void *ct, const void *changes) {
+        ok &= SOSChangeTrackerTrackChanges((SOSChangeTrackerRef)ct, cm->engine, cm->txn, cm->source, cm->phase, (CFArrayRef)changes, error);
+    });
+    return ok;
+}
+
+static bool SOSEngineUpdateChanges_locked(SOSEngineRef engine, SOSTransactionRef txn, SOSDataSourceTransactionPhase phase, SOSDataSourceTransactionSource source, CFArrayRef changes, CFErrorRef *error)
+{
+    secnoticeq("engine", "%@: %s %s %ld changes", engine->myID, phase == kSOSDataSourceTransactionWillCommit ? "will-commit" : phase == kSOSDataSourceTransactionDidCommit ? "did-commit" : "did-rollback", source == kSOSDataSourceSOSTransaction ? "sos" : "api", CFArrayGetCount(changes));
+    bool ok = true;
+    switch (phase) {
+        case kSOSDataSourceTransactionDidRollback:
+            ok &= SOSEngineLoad(engine, error);
+            break;
+        case kSOSDataSourceTransactionWillCommit:
+        case kSOSDataSourceTransactionDidCommit:
+        {
+            struct SOSChangeMapper cm;
+            SOSChangeMapperInit(&cm, engine, txn, phase, source);
+            SecDbEventRef event;
+            CFArrayForEachC(changes, event) {
+                CFTypeRef deleted = NULL;
+                CFTypeRef inserted = NULL;
+                SecDbEventGetComponents(event, &deleted, &inserted, error);
+                if (deleted)
+                    SOSChangeMapperIngestChange(&cm, false, deleted);
+                if (inserted) {
+                    bool someoneCares = SOSChangeMapperIngestChange(&cm, true, inserted);
+                    if (!someoneCares && !isData(inserted) && SecDbItemIsTombstone((SecDbItemRef)inserted) && !CFEqualSafe(SecDbItemGetValue((SecDbItemRef)inserted, &v7utomb, NULL), kCFBooleanTrue)) {
+                        CFErrorRef localError = NULL;
+                        // A tombstone was inserted but there is no changetracker that
+                        // cares about it.
+                        if (!SecDbItemDoDeleteSilently((SecDbItemRef)inserted, (SecDbConnectionRef)txn, &localError)) {
+                            secerror("failed to delete tombstone %@ that no one cares about: %@", inserted, localError);
+                            CFReleaseNull(localError);
+                        }
+                    }
+                }
+            }
+
+            ok &= SOSChangeMapperSend(&cm, error);
+            SOSChangeMapperFree(&cm);
+
+            if (phase == kSOSDataSourceTransactionDidCommit) {
+                // We are being called outside a transaction, beware, that any
+                // db changes we attempt to make here will cause deadlock!
+            } else {
+                // Write SOSEngine and SOSPeer state to disk
+                // TODO: Only do this if dirty
+                ok &= SOSEngineSave(engine, txn, error);
+            }
+            break;
+        }
+    }
+    return ok;
+}
+
+static void SOSEngineSetNotifyPhaseBlock(SOSEngineRef engine) {
+    SOSDataSourceSetNotifyPhaseBlock(engine->dataSource, engine->queue, ^(SOSDataSourceRef ds, SOSTransactionRef txn, SOSDataSourceTransactionPhase phase, SOSDataSourceTransactionSource source, CFArrayRef changes) {
+        CFErrorRef localError = NULL;
+        if (!SOSEngineUpdateChanges_locked(engine, txn, phase, source, changes, &localError)) {
+            secerror("updateChanged failed: %@", localError);
+        }
+        CFReleaseSafe(localError);
+    });
+}
+
+#if 0 // TODO: update these checks
+static void SOSEngineCircleChanged_sanitycheck(SOSEngineRef engine, CFStringRef myPeerID, CFArrayRef trustedPeers, CFArrayRef untrustedPeers) {
+    // Logging code
+    CFMutableArrayRef addedPeers = CFArrayCreateDifference(kCFAllocatorDefault, trustedPeers, engine->peerIDs);
+    CFMutableArrayRef deletedPeers = CFArrayCreateDifference(kCFAllocatorDefault, engine->peerIDs, trustedPeers);
+    CFMutableArrayRef addedUntrustedPeers = CFArrayCreateDifference(kCFAllocatorDefault, untrustedPeers, engine->peerIDs);
+    CFMutableArrayRef deletedUntrustedPeers = CFArrayCreateDifference(kCFAllocatorDefault, engine->peerIDs, untrustedPeers);
+
+    CFStringRef tpDesc = SOSPeerIDArrayCreateString(trustedPeers);
+    CFStringRef apDesc = SOSPeerIDArrayCreateString(addedPeers);
+    CFStringRef dpDesc = SOSPeerIDArrayCreateString(deletedPeers);
+    CFStringRef aupDesc = SOSPeerIDArrayCreateString(addedUntrustedPeers);
+    CFStringRef dupDesc = SOSPeerIDArrayCreateString(deletedUntrustedPeers);
+    secnotice("engine", "trusted %@ added %@ removed %@ add ut: %@ rem ut: %@", tpDesc, apDesc, dpDesc, aupDesc, dupDesc);
+    CFReleaseSafe(dupDesc);
+    CFReleaseSafe(aupDesc);
+    CFReleaseSafe(dpDesc);
+    CFReleaseSafe(apDesc);
+    CFReleaseSafe(tpDesc);
+
+    // Assertions:
+    // Ensure SOSAccount isn't giving us the runaround.
+    // Assert that trustedPeers, untrustedPeers and myPeerId are disjoint sets
+    if (trustedPeers) {
+        CFMutableArrayRef allTrustedPeers = CFArrayCreateDifference(kCFAllocatorDefault, trustedPeers, untrustedPeers);
+        assert(CFEqual(trustedPeers, allTrustedPeers));
+        CFReleaseSafe(allTrustedPeers);
+        assert(!CFArrayContainsValue(trustedPeers, CFRangeMake(0, CFArrayGetCount(trustedPeers)), myPeerID));
+    }
+    if (untrustedPeers) {
+        CFMutableArrayRef allUntrustedPeers = CFArrayCreateDifference(kCFAllocatorDefault, untrustedPeers, trustedPeers);
+        assert(CFEqual(untrustedPeers, allUntrustedPeers));
+        CFReleaseSafe(allUntrustedPeers);
+        assert(!CFArrayContainsValue(untrustedPeers, CFRangeMake(0, CFArrayGetCount(trustedPeers)), myPeerID));
+    }
+
+    CFReleaseNull(deletedUntrustedPeers);
+    CFReleaseNull(addedUntrustedPeers);
+    CFReleaseNull(deletedPeers);
+    CFReleaseNull(addedPeers);
+
+    // End of logging and asertions, actual code here.
+}
+#endif
+
+static SOSChangeTrackerRef SOSReferenceAndGetChangeTracker(CFDictionaryRef lookup, CFMutableDictionaryRef referenced, CFSetRef viewNameSet) {
+    SOSChangeTrackerRef ct = (SOSChangeTrackerRef)CFDictionaryGetValue(referenced, viewNameSet);
+    if (!ct) {
+        ct = (SOSChangeTrackerRef)CFDictionaryGetValue(lookup, viewNameSet);
+        if (ct) {
+            SOSChangeTrackerResetRegistration(ct);
+            CFDictionarySetValue(referenced, viewNameSet, ct);
+        } else {
+            ct = SOSChangeTrackerCreate(kCFAllocatorDefault, false, NULL, NULL);
+            CFDictionarySetValue(referenced, viewNameSet, ct);
+            CFReleaseSafe(ct);
+        }
+    }
+    return ct;
+}
+
+static CFStringRef CFStringCreateWithViewNameSet(CFSetRef vns);
+
+static void CFStringAppendPeerIDAndViews(CFMutableStringRef desc, CFStringRef peerID, CFSetRef vns) {
+    if (vns) {
+        CFStringRef vnsDesc = CFStringCreateWithViewNameSet(vns);
+        CFStringAppendFormat(desc, NULL, CFSTR(" %@ (%@)"), peerID, vnsDesc);
+        CFReleaseSafe(vnsDesc);
+    } else {
+        CFStringAppendFormat(desc, NULL, CFSTR(" %@ NULL"), peerID);
+    }
+}
+
+// Must be called after updating viewNameSet2ChangeTracker
+static void SOSEngineUpdateViewName2ChangeTracker(SOSEngineRef engine) {
+    // Create the mapping from viewName -> ChangeTracker used for lookup during change notification
+    CFMutableDictionaryRef newViewName2ChangeTracker = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    CFDictionaryForEach(engine->viewNameSet2ChangeTracker, ^(const void *viewNameSet, const void *ct) {
+        CFSetForEach(viewNameSet, ^(const void *viewName) {
+            const void *ctorset = NULL;
+            if (CFDictionaryGetValueIfPresent(newViewName2ChangeTracker, viewName, &ctorset)) {
+                if (isSet(ctorset)) {
+                    CFSetAddValue((CFMutableSetRef)ctorset, ct);
+                } else if (!CFEqual(ct, ctorset)) {
+                    CFMutableSetRef set = CFSetCreateMutableForCFTypes(kCFAllocatorDefault);
+                    CFSetAddValue(set, ctorset);
+                    CFSetAddValue(set, ct);
+                    CFDictionaryReplaceValue(newViewName2ChangeTracker, viewName, set);
+                    CFRelease(set);
+                }
+            } else {
+                CFDictionarySetValue(newViewName2ChangeTracker, viewName, ct);
+            }
+        });
+    });
+    CFAssignRetained(engine->viewName2ChangeTracker, newViewName2ChangeTracker);
+}
+
+static void SOSEngineSetBackupBag(SOSEngineRef engine, SOSObjectRef bagItem);
+
+// This is called only if we are in a circle and we should listen for keybag changes
+static void SOSEngineRegisterBackupBagV0Tracker(SOSEngineRef engine, CFMutableDictionaryRef newViewNameSet2ChangeTracker, CFMutableStringRef desc) {
+    SOSChangeTrackerRef bbct = SOSReferenceAndGetChangeTracker(engine->viewNameSet2ChangeTracker, newViewNameSet2ChangeTracker, SOSViewsGetV0BackupBagViewSet());
+    SOSChangeTrackerRegisterChangeUpdate(bbct, ^bool(SOSChangeTrackerRef ct, SOSEngineRef engine, SOSTransactionRef txn, SOSDataSourceTransactionSource source, SOSDataSourceTransactionPhase phase, CFArrayRef changes, CFErrorRef *error) {
+        SOSChangeRef change;
+        CFArrayForEachC(changes, change) {
+            CFTypeRef object = NULL;
+            bool isAdd = SOSChangeGetObject(change, &object);
+            SecDbItemRef dbi = (SecDbItemRef)object;
+            if (!isData(object) &&
+                CFEqualSafe(SecDbItemGetCachedValueWithName(dbi, kSecAttrService), CFSTR("SecureBackupService")) &&
+                CFEqualSafe(SecDbItemGetCachedValueWithName(dbi, kSecAttrAccessible), kSecAttrAccessibleWhenUnlocked) &&
+                CFEqualSafe(SecDbItemGetCachedValueWithName(dbi, kSecAttrAccount), CFSTR("SecureBackupPublicKeybag"))) {
+                SOSEngineSetBackupBag(engine, isAdd ? (SOSObjectRef)object : NULL);
+            }
+        }
+        return true;
+    });
+}
+
+static void SOSEngineReferenceBackupPeer(SOSEngineRef engine, CFStringRef peerID, CFSetRef viewNameSet, CFDataRef keyBag, CFMutableDictionaryRef newViewNameSet2ChangeTracker, CFMutableDictionaryRef newPeerMap) {
+    CFTypeRef oldEntry = CFDictionaryGetValue(engine->peerMap, peerID);
+    CFTypeRef newEntry = SOSPeerOrStateSetViewsKeyBagAndCreateCopy(oldEntry, viewNameSet, keyBag);
+    if (newEntry) {
+        if (isDictionary(newEntry)) {
+            // Backup peers, are always inflated
+            CFAssignRetained(newEntry, SOSPeerCreateWithState(engine, peerID, newEntry, NULL));
+            // If !oldEntry this is an edge (first creation of a peer).
+            if (!oldEntry) {
+                SOSPeerKeyBagDidChange((SOSPeerRef)newEntry);
+            }
+        }
+        CFDictionarySetValue(newPeerMap, peerID, newEntry);
+        CFRelease(newEntry);
+
+        if (keyBag) {
+            SOSChangeTrackerRef ct = SOSReferenceAndGetChangeTracker(engine->viewNameSet2ChangeTracker, newViewNameSet2ChangeTracker, viewNameSet);
+            
+            SOSChangeTrackerUpdatesChanges child = Block_copy(^bool(SOSChangeTrackerRef ct, SOSEngineRef engine, SOSTransactionRef txn, SOSDataSourceTransactionSource source, SOSDataSourceTransactionPhase phase, CFArrayRef changes, CFErrorRef *error) {
+                return SOSPeerDataSourceWillChange((SOSPeerRef)newEntry, SOSEngineGetDataSource(engine), source, changes, error);
+            });
+           
+            SOSChangeTrackerRegisterChangeUpdate(ct, child);
+            Block_release(child);
+        }
+    }
+}
+
+static void SOSEngineReferenceSyncPeer(SOSEngineRef engine, CFStringRef peerID, CFSetRef viewNameSet, CFMutableDictionaryRef newViewNameSet2ChangeTracker, CFMutableDictionaryRef newPeerMap) {
+    CFTypeRef newEntry = SOSPeerOrStateSetViewsKeyBagAndCreateCopy(CFDictionaryGetValue(engine->peerMap, peerID), viewNameSet, NULL);
+    if (newEntry) {
+        SOSChangeTrackerRef ct = SOSReferenceAndGetChangeTracker(engine->viewNameSet2ChangeTracker, newViewNameSet2ChangeTracker, viewNameSet);
+        // Standard peer, inflated on demand
+        SOSChangeTrackerUpdatesManifests trackManifest;
+        if (isDictionary(newEntry)) {
+            // Uninflated peer, inflate on first notification.
+            trackManifest = ^bool(SOSChangeTrackerRef ct, SOSEngineRef engine, SOSTransactionRef txn, SOSDataSourceTransactionSource source, SOSDataSourceTransactionPhase phase, SOSManifestRef removals, SOSManifestRef additions, CFErrorRef *error) {
+                CFErrorRef localError = NULL;
+                SOSPeerRef peer = SOSEngineCopyPeerWithID_locked(engine, peerID, &localError);
+                bool ok;
+                if (!peer) {
+                    secerror("%@: peer failed to inflate: %@", peerID, localError);
+                    CFReleaseSafe(localError);
+                    ok = false;
+                } else {
+                    ok = SOSPeerDataSourceWillCommit(peer, source, removals, additions, error);
+                }
+                CFReleaseSafe(peer);
+                return ok;
+            };
+        } else {
+            // Inflated peer, just forward the changes to the peer
+            trackManifest = ^bool(SOSChangeTrackerRef ct, SOSEngineRef engine, SOSTransactionRef txn, SOSDataSourceTransactionSource source, SOSDataSourceTransactionPhase phase, SOSManifestRef removals, SOSManifestRef additions, CFErrorRef *error) {
+                return SOSPeerDataSourceWillCommit((SOSPeerRef)newEntry, source, removals, additions, error);
+            };
+        }
+        SOSChangeTrackerUpdatesManifests trackManifestCopy = Block_copy(trackManifest);
+        SOSChangeTrackerRegisterManifestUpdate(ct, trackManifestCopy);
+        Block_release(trackManifestCopy);
+
+        CFDictionarySetValue(newPeerMap, peerID, newEntry);
+        CFRelease(newEntry);
+    }
+}
+
+
+static void SOSEngineReferenceTrustedPeer(SOSEngineRef engine, SOSPeerMetaRef peerMeta, CFMutableDictionaryRef newViewNameSet2ChangeTracker, CFMutableDictionaryRef newPeerMap, CFMutableArrayRef peerIDs, CFMutableStringRef desc) {
+    CFSetRef viewNameSet = NULL;
+    CFDataRef keyBag = NULL;
+    CFStringRef peerID = SOSPeerMetaGetComponents(peerMeta, &viewNameSet, &keyBag, NULL);
+    // We trust peerID so append it to peerIDs
+    CFArrayAppendValue(peerIDs, peerID);
+    if (desc) CFStringAppendPeerIDAndViews(desc, peerID, viewNameSet);
+    // Update the viewNameSet for this peer, to appease tests, default to a viewset of the V0 view.
+    if (!viewNameSet)
+        viewNameSet = SOSViewsGetV0ViewSet();
+
+    // Always inflate backup peers, since they need to register with their changeTrackers right away.
+    if (keyBag) {
+        SOSEngineReferenceBackupPeer(engine, peerID, viewNameSet, keyBag, newViewNameSet2ChangeTracker, newPeerMap);
+    } else {
+        SOSEngineReferenceSyncPeer(engine, peerID, viewNameSet, newViewNameSet2ChangeTracker, newPeerMap);
+    }
+}
+
+static CFDataRef SOSEngineLoadV0KeyBag(SOSEngineRef engine, CFErrorRef *error) {
+    // Return the keybag for the given peerID.
+    /*
+     Values for V0 are:
+     kSecAttrAccessGroup ==> CFSTR("com.apple.sbd")
+     kSecAttrAccessible  ==> kSecAttrAccessibleWhenUnlocked
+     kSecAttrAccount     ==> CFSTR("SecureBackupPublicKeybag")
+     kSecAttrService     ==> CFSTR("SecureBackupService")
+     */
+
+    CFMutableDictionaryRef keys = CFDictionaryCreateMutableForCFTypesWith(kCFAllocatorDefault,
+                                            kSecAttrAccessGroup, CFSTR("com.apple.sbd"),
+                                            kSecAttrAccount, CFSTR("SecureBackupPublicKeybag"),
+                                            kSecAttrService, CFSTR("SecureBackupService"),
+                                            kSecAttrAccessible, kSecAttrAccessibleWhenUnlocked,
+                                            kSecAttrSynchronizable, kCFBooleanTrue,
+                                            NULL);
+
+    CFDataRef keybag = engine->dataSource->dsCopyItemDataWithKeys(engine->dataSource, keys, error);
+    CFReleaseSafe(keys);
+
+    return keybag;
+}
+
+static void SOSEngineReferenceBackupV0Peer(SOSEngineRef engine, CFMutableDictionaryRef newViewNameSet2ChangeTracker, CFMutableDictionaryRef newPeerMap, CFMutableArrayRef newPeerIDs, CFMutableStringRef desc) {
+    SOSPeerRef backupPeer = (SOSPeerRef)CFDictionaryGetValue(engine->peerMap, kSOSViewKeychainV0_tomb);
+    CFDataRef bag = NULL;
+    if (backupPeer && CFGetTypeID(backupPeer) == SOSPeerGetTypeID()) {
+        bag = SOSPeerGetKeyBag(backupPeer);
+    } else {
+        CFErrorRef localError = NULL;
+        if (!(bag = SOSEngineLoadV0KeyBag(engine, &localError))) {
+            secnotice("engine", "No keybag found for v0 backup peer: %@", localError);
+            CFReleaseSafe(localError);
+        }
+    }
+    SOSEngineReferenceBackupPeer(engine, kSOSViewKeychainV0_tomb, SOSViewsGetV0BackupViewSet(), bag, newViewNameSet2ChangeTracker, newPeerMap);
+}
+
+static void SOSEngineReferenceTrustedPeers(SOSEngineRef engine, CFMutableDictionaryRef newViewNameSet2ChangeTracker, CFMutableDictionaryRef newPeerMap, CFMutableArrayRef newPeerIDs, CFArrayRef trustedPeerMetas, CFMutableStringRef desc) {
+    // Then update the views for all trusted peers and add them to newPeerMap.
+    if (trustedPeerMetas != NULL && CFArrayGetCount(trustedPeerMetas) != 0) {
+        if (desc) CFStringAppend(desc, CFSTR(" trusted"));
+        // Remake engine->peerIDs
+        SOSPeerMetaRef peerMeta;
+        CFArrayForEachC(trustedPeerMetas, peerMeta) {
+            SOSEngineReferenceTrustedPeer(engine, peerMeta, newViewNameSet2ChangeTracker, newPeerMap, newPeerIDs, desc);
+        }
+    }
+}
+
+static void SOSEngineReferenceUntrustedPeers(SOSEngineRef engine, CFMutableDictionaryRef newPeerMap, CFArrayRef untrustedPeerMetas, CFMutableStringRef description) {
+    // Copy any untrustedPeers to newPeerMap as well if we have a state
+    // for them, if not no big deal.  We also serialize all the untrustedPeers
+    // since they don't need to be deserializable
+    if (untrustedPeerMetas != NULL && CFArrayGetCount(untrustedPeerMetas) != 0) {
+        if (description) CFStringAppend(description, CFSTR(" untrusted"));
+        SOSPeerMetaRef peerMeta;
+        CFArrayForEachC(untrustedPeerMetas, peerMeta) {
+            CFSetRef views = NULL;
+            CFStringRef peerID = SOSPeerMetaGetComponents(peerMeta, &views, NULL, NULL);
+            if (description) CFStringAppendPeerIDAndViews(description, peerID, views);
+            CFSetRef nviews = NULL;
+            if (!views)
+                views = nviews = CFSetCreate(kCFAllocatorDefault, NULL, 0, &kCFTypeSetCallBacks);
+            CFTypeRef newEntry = SOSPeerOrStateSetViewsAndCopyState(CFDictionaryGetValue(engine->peerMap, peerID), views);
+            CFReleaseSafe(nviews);
+            if (newEntry) {
+                CFDictionarySetValue(newPeerMap, peerID, newEntry);
+                CFReleaseSafe(newEntry);
+            }
+        }
+    }
+}
+
+static void SOSEngineReferenceChangeTrackers(SOSEngineRef engine, CFArrayRef trustedPeerMetas, CFArrayRef untrustedPeerMetas, CFMutableStringRef desc) {
+    CFMutableArrayRef newPeerIDs = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+    CFMutableDictionaryRef newPeerMap = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    CFMutableDictionaryRef newViewNameSet2ChangeTracker = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+
+    if (engine->myID) {
+        // We have an engineID => in a circle (with 0 or more peers)
+        // Ensure we have a v0 backup peer and it's listening for backup bag changes
+        SOSEngineReferenceBackupV0Peer(engine, newViewNameSet2ChangeTracker, newPeerMap, newPeerIDs, desc);
+        SOSEngineRegisterBackupBagV0Tracker(engine, newViewNameSet2ChangeTracker, desc);
+    }
+    SOSEngineReferenceTrustedPeers(engine, newViewNameSet2ChangeTracker, newPeerMap, newPeerIDs, trustedPeerMetas, desc);
+    SOSEngineReferenceUntrustedPeers(engine, newPeerMap, untrustedPeerMetas, desc);
+
+    CFAssignRetained(engine->peerIDs, newPeerIDs);
+    CFAssignRetained(engine->peerMap, newPeerMap);
+    CFAssignRetained(engine->viewNameSet2ChangeTracker, newViewNameSet2ChangeTracker);
+    SOSEngineUpdateViewName2ChangeTracker(engine);
+}
+
+// Return true iff peers or views changed
+static bool SOSEngineSetPeers_locked(SOSEngineRef engine, SOSPeerMetaRef myPeerMeta, CFArrayRef trustedPeerMetas, CFArrayRef untrustedPeerMetas) {
+    CFErrorRef error = NULL;
+    CFSetRef myViews = NULL;
+    CFDataRef myKeyBag = NULL;
+    CFMutableStringRef desc = CFStringCreateMutableCopy(kCFAllocatorDefault, 0, CFSTR("me"));
+    CFStringRef myPeerID = myPeerMeta ? SOSPeerMetaGetComponents(myPeerMeta, &myViews, &myKeyBag, &error) : NULL;
+    if (desc) CFStringAppendPeerIDAndViews(desc, myPeerID, myViews);
+
+    CFRetainAssign(engine->myID, myPeerID);
+
+    // Remake engine->peerMap from both trusted and untrusted peers
+    SOSEngineReferenceChangeTrackers(engine, trustedPeerMetas, untrustedPeerMetas, desc);
+
+    secnotice("engine", "%@", desc);
+    CFReleaseSafe(desc);
+    return true;
+}
+
+static void SOSEngineApplyPeerState(SOSEngineRef engine, CFDictionaryRef peerStateMap) {
+    if (peerStateMap) CFDictionaryForEach(peerStateMap, ^(const void *peerID, const void *peerState) {
+        CFTypeRef mapEntry = CFDictionaryGetValue(engine->peerMap, peerID);
+        if (mapEntry && CFGetTypeID(mapEntry) == SOSPeerGetTypeID()) {
+            // Update the state of any already inflated peers
+            SOSPeerRef peer = (SOSPeerRef)mapEntry;
+            CFErrorRef localError = NULL;
+            if (!SOSPeerSetState(peer, engine, peerState, &localError)) {
+                CFStringRef stateHex = NULL;
+                stateHex = CFDataCopyHexString(peerState);
+                secerror("peer: %@: bad state: %@ in engine state: %@", peerID, localError, stateHex);
+                CFReleaseSafe(stateHex);
+                CFReleaseNull(localError);
+                // Possibly ask for an ensurePeerRegistration so we have a good list or peers again.
+            }
+        } else {
+            // Just record the state for non inflated peers for now.
+            CFDictionarySetValue(engine->peerMap, peerID, peerState);
+        }
+    });
+}
+
+static void SOSEngineSynthesizePeerMetas(SOSEngineRef engine, CFMutableArrayRef trustedPeersMetas, CFMutableArrayRef untrustedPeers) {
+    CFSetRef trustedPeerSet = engine->peerIDs ? CFSetCreateCopyOfArrayForCFTypes(engine->peerIDs) : NULL;
+    CFDictionaryForEach(engine->peerMap, ^(const void *peerID, const void *peerState) {
+        SOSPeerMetaRef meta = NULL;
+        if (peerState && CFGetTypeID(peerState) == SOSPeerGetTypeID()) {
+            SOSPeerRef peer = (SOSPeerRef)peerState;
+            meta = SOSPeerMetaCreateWithComponents(peerID, SOSPeerGetViewNameSet(peer), SOSPeerGetKeyBag(peer));
+        } else {
+            // We don't need to add the meta for the backup case, since
+            //   SOSEngineReferenceBackupV0Peer will do the right thing
+            if (!CFEqualSafe(peerID, kSOSViewKeychainV0_tomb)) {
+                meta = SOSPeerMetaCreateWithState(peerID, peerState);
+            }
+        }
+        // Any peer in peerStateMap that is not in trustedPeers is an untrustedPeer unless it's the v0 backup peer
+        if ((trustedPeerSet && CFSetContainsValue(trustedPeerSet, peerID)) || CFEqualSafe(peerID, kSOSViewKeychainV0_tomb)) {
+            if (meta) {
+                CFArrayAppendValue(trustedPeersMetas, meta);
+            }
+        } else {
+            CFArrayAppendValue(untrustedPeers, peerID);
+        }
+        CFReleaseNull(meta);
+    });
+    CFReleaseNull(trustedPeerSet);
+}
+
+static void SOSEngineSetBackupBag(SOSEngineRef engine, SOSObjectRef bagItem) {
+    CFMutableStringRef desc = NULL;
+    SOSPeerRef backupPeer = SOSEngineCopyPeerWithID_locked(engine, kSOSViewKeychainV0_tomb, NULL);
+    CFDataRef keybag = NULL;
+    if (bagItem) {
+        keybag = SecDbItemGetValue((SecDbItemRef)bagItem, &v6v_Data, NULL);
+    }
+
+    // Since SOSPeerSetKeyBag() doesn't notify on the edge from NULL->initial keybag, since
+    // that is the right behaviour for non v0 backup peers, we need to do it here for the v0 peer.
+    bool hadBag = SOSPeerGetKeyBag(backupPeer);
+    SOSPeerSetKeyBag(backupPeer, keybag);
+    if (!hadBag)
+        SOSPeerKeyBagDidChange(backupPeer);
+
+    CFReleaseSafe(backupPeer);
+
+    CFMutableArrayRef untrustedPeerMetas = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+    CFMutableArrayRef trustedPeersMetas = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+    SOSEngineSynthesizePeerMetas(engine, trustedPeersMetas, untrustedPeerMetas);
+    SOSEngineReferenceChangeTrackers(engine, trustedPeersMetas, untrustedPeerMetas, desc);
+    CFReleaseSafe(trustedPeersMetas);
+    CFReleaseSafe(untrustedPeerMetas);
+}
+
+#define SECONDS_PER_DAY  (86400.0)
+
+#if (TARGET_OS_MAC && !(TARGET_OS_EMBEDDED || TARGET_OS_IPHONE))
+#define TRACE_INTERVAL (7 * SECONDS_PER_DAY)
+#elif (TARGET_OS_IPHONE && !TARGET_IPHONE_SIMULATOR)
+#define TRACE_INTERVAL (1 * SECONDS_PER_DAY)
+#endif
+
+#ifdef TRACE_INTERVAL
+static void SOSEngineCloudKeychainTrace(SOSEngineRef engine, CFAbsoluteTime now) {
+    CFAssignRetained(engine->lastTraceDate, CFDateCreate(kCFAllocatorDefault, now));
+    CFIndex num_peers = engine->peerIDs ? 1 + CFArrayGetCount(engine->peerIDs) : 1;
+    SOSManifestRef manifest = SOSEngineCopyManifestWithViewNameSet_locked(engine, SOSViewsGetV0ViewSet(), NULL);
+    if (!manifest)
+        manifest = SOSDataSourceCopyManifestWithViewNameSet(engine->dataSource, SOSViewsGetV0ViewSet(), NULL);
+    size_t num_items = SOSManifestGetCount(manifest);
+    CFReleaseSafe(manifest);
+    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+        CloudKeychainTrace(num_peers, num_items);
+    });
+}
+#endif
+
+static void SOSEngineCloudKeychainTraceIfNeeded(SOSEngineRef engine) {
+#ifdef TRACE_INTERVAL
+    if (!engine->myID)
+        return;
+    CFAbsoluteTime now = CFAbsoluteTimeGetCurrent();
+    if (engine->lastTraceDate) {
+        CFAbsoluteTime lastTraceTime = CFDateGetAbsoluteTime(engine->lastTraceDate);
+        if ((now - lastTraceTime) >= TRACE_INTERVAL) {
+            SOSEngineCloudKeychainTrace(engine, now);
+        }
+    } else {
+        SOSEngineCloudKeychainTrace(engine, now);
+    }
+#endif
+}
+
+// Restore the in-memory state of engine from saved state loaded from the db
+static bool SOSEngineSetState(SOSEngineRef engine, CFDataRef state, CFErrorRef *error) {
+    __block bool ok = true;
+    if (state) {
+        CFMutableDictionaryRef dict = NULL;
+        const uint8_t *der = CFDataGetBytePtr(state);
+        const uint8_t *der_end = der + CFDataGetLength(state);
+        ok = der = der_decode_dictionary(kCFAllocatorDefault, kCFPropertyListMutableContainers, (CFDictionaryRef *)&dict, error, der, der_end);
+        if (der && der != der_end) {
+            ok = SOSErrorCreate(kSOSErrorDecodeFailure, error, NULL, CFSTR("trailing %td bytes at end of state"), der_end - der);
+        } else if (ok) {
+            CFReleaseNull(engine->manifestCache);
+            CFMutableDictionaryRef mfc = (CFMutableDictionaryRef)CFDictionaryGetValue(dict, kSOSEngineManifestCacheKey);
+            if (mfc) {
+                engine->manifestCache = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+                CFDictionaryForEach(mfc, ^(const void *key, const void *value) {
+                    CFDataRef data = (CFDataRef)value;
+                    if (isData(data)) {
+                        SOSManifestRef mf = SOSManifestCreateWithData(data, NULL);
+                        if (mf)
+                            CFDictionarySetValue(engine->manifestCache, key, mf);
+                        CFReleaseSafe(mf);
+                    }
+                });
+            }
+            CFMutableArrayRef untrustedPeers = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+            CFMutableArrayRef trustedPeersMetas = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+            CFRetainAssign(engine->peerIDs, asArray(CFDictionaryGetValue(dict, kSOSEnginePeerIDsKey), NULL));
+            CFRetainAssign(engine->lastTraceDate, asDate(CFDictionaryGetValue(dict, kSOSEngineTraceDateKey), NULL));
+            SOSEngineApplyPeerState(engine, asDictionary(CFDictionaryGetValue(dict, kSOSEnginePeerStateKey), NULL));
+            SOSEngineSynthesizePeerMetas(engine, trustedPeersMetas, untrustedPeers);
+            SOSEngineSetPeers_locked(engine, (CFStringRef)CFDictionaryGetValue(dict, kSOSEngineIDKey),
+                                     trustedPeersMetas, untrustedPeers);
+            CFReleaseNull(trustedPeersMetas);
+            CFReleaseNull(untrustedPeers);
+        }
+        CFReleaseNull(dict);
+    }
+    secnotice("engine", "%@", engine);
+    return ok;
+}
+
+static bool SOSEngineLoad(SOSEngineRef engine, CFErrorRef *error) {
+    CFDataRef state = SOSDataSourceCopyStateWithKey(engine->dataSource, kSOSEngineState, kSecAttrAccessibleAlways, error);
+    bool ok = state && SOSEngineSetState(engine, state, error);
+    CFReleaseSafe(state);
+    return ok;
+}
+
+static CFStringRef accountStatusFileName = CFSTR("accountStatus.plist");
+
+static bool SOSEngineCircleChanged_locked(SOSEngineRef engine, SOSPeerMetaRef myPeerMeta, CFArrayRef trustedPeers, CFArrayRef untrustedPeers) {
+    // Sanity check params
+//    SOSEngineCircleChanged_sanitycheck(engine, myPeerID, trustedPeers, untrustedPeers);
+
+    // Transform from SOSPeerInfoRefs to CFDictionaries with the info we want per peer.
+    // Or, Tell the real SOSPeerRef what the SOSPeerInfoRef is and have it copy out the data it needs.
+    bool peersOrViewsChanged = SOSEngineSetPeers_locked(engine, myPeerMeta, trustedPeers, untrustedPeers);
+
+    // Run though all peers and only cache manifests for peers we still have
+    CFErrorRef localError = NULL;
+    if (!SOSEngineGCPeerState_locked(engine, &localError)) {
+        secerror("SOSEngineGCPeerState_locked failed: %@", localError);
+        CFReleaseNull(localError);
+    }
+    return peersOrViewsChanged;
+}
+
+// Initialize the engine if a load fails.  Basically this is our first time setup
+static bool SOSEngineInit(SOSEngineRef engine, CFErrorRef *error) {
+    bool ok = true;
+    secnotice("engine", "new engine for datasource named %@", SOSDataSourceGetName(engine->dataSource));
+    CFAssignRetained(engine->peerMap, CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault));
+    CFAssignRetained(engine->viewNameSet2ChangeTracker, CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault));
+    CFAssignRetained(engine->viewName2ChangeTracker, CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault));
+    CFReleaseNull(engine->manifestCache);
+    CFReleaseNull(engine->peerIDs);
+    // TODO: We shouldn't need to load the backup bag if there was no engine
+    // state (load failed), since that means there was no circle nor were we an applicant.
+
+    // Set up change trackers so we know when a backup peer needs to be created?
+    // no, since myID is not set, we are not in a circle, so no need to back up
+    SOSEngineSetPeers_locked(engine, NULL, NULL, NULL);
+    return ok;
+}
+
+// Called by our DataSource in its constructor
+SOSEngineRef SOSEngineCreate(SOSDataSourceRef dataSource, CFErrorRef *error) {
+    SOSEngineRef engine = NULL;
+    engine = CFTypeAllocate(SOSEngine, struct __OpaqueSOSEngine, kCFAllocatorDefault);
+    engine->dataSource = dataSource;
+    engine->queue = dispatch_queue_create("engine", DISPATCH_QUEUE_SERIAL);
+
+    engine->peerMap = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    engine->viewNameSet2ChangeTracker = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    engine->viewName2ChangeTracker = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    //engine->syncCompleteQueue = NULL;
+    engine->syncCompleteListeners = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    CFErrorRef engineError = NULL;
+    if (!SOSEngineLoad(engine, &engineError)) {
+        secwarning("engine failed load state starting with nothing %@", engineError);
+        CFReleaseNull(engineError);
+        if (!SOSEngineInit(engine, error)) {
+            secerror("engine failed to initialze %@ giving up", error ? *error : NULL);
+        }
+    } else {
+        // Successfully loaded engine state, let's trace if we haven't in a while
+        SOSEngineCloudKeychainTraceIfNeeded(engine);
+    }
+    SOSEngineSetNotifyPhaseBlock(engine);
+    return engine;
+}
+
+// --- Called from off the queue, need to move to on the queue
+
+static void SOSEngineDoOnQueue(SOSEngineRef engine, dispatch_block_t action)
+{
+    dispatch_sync(engine->queue, action);
+}
+
+static bool SOSEngineDoTxnOnQueue(SOSEngineRef engine, CFErrorRef *error, void(^transaction)(SOSTransactionRef txn, bool *commit))
+{
+    return SOSDataSourceWith(engine->dataSource, error, ^(SOSTransactionRef txn, bool *commit) {
+        SOSEngineDoOnQueue(engine, ^{ transaction(txn, commit); });
+    });
+}
+
+//
+// MARK: SOSEngine API
+//
+
+void SOSEngineDispose(SOSEngineRef engine) {
+    // NOOP Engines stick around forever to monitor dataSource changes.
+}
+
+void SOSEngineForEachPeer(SOSEngineRef engine, void (^with)(SOSPeerRef peer)) {
+    SOSEngineDoOnQueue(engine, ^{
+        SOSEngineForEachPeer_locked(engine, with);
+    });
+}
+
+static void SOSEngineForEachBackupPeer(SOSEngineRef engine, void (^with)(SOSPeerRef peer)) {
+    SOSEngineDoOnQueue(engine, ^{
+        SOSEngineForEachBackupPeer_locked(engine, with);
+    });
+}
+
+
+/* Handle incoming message from peer p.  Return false if there was an error, true otherwise. */
+bool SOSEngineHandleMessage_locked(SOSEngineRef engine, CFStringRef peerID, SOSMessageRef message,
+                                   SOSTransactionRef txn, bool *commit, bool *somethingChanged, CFErrorRef *error) {
+    SOSPeerRef peer = SOSEngineCopyPeerWithID_locked(engine, peerID, error);
+    if (!peer) return false;
+    CFStringRef peerDesc = NULL;
+    SOSManifestRef localManifest = NULL;
+    SOSManifestRef allAdditions = NULL;
+    SOSManifestRef unwanted = NULL;
+    SOSManifestRef confirmed = NULL;
+    SOSManifestRef base = NULL;
+    SOSManifestRef confirmedRemovals = NULL, confirmedAdditions = NULL;
+    __block struct SOSDigestVector receivedObjects = SOSDigestVectorInit;
+    __block struct SOSDigestVector unwantedObjects = SOSDigestVectorInit;
+
+    // Check for unknown criticial extensions in the message, and handle
+    // any other extensions we support
+    __block bool ok = true;
+    CFMutableArrayRef changes = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+
+    require_action_quiet(peer, exit, ok = SOSErrorCreate(errSecParam, error, NULL, CFSTR("Couldn't create peer with Engine for %@"), peerID));
+    peerDesc = CFCopyDescription(peer);
+
+    SOSMessageWithExtensions(message, true, ^(CFDataRef oid, bool isCritical, CFDataRef extension, bool *stop) {
+        // OMFG a Critical extension what shall I do!
+        ok = SOSErrorCreate(kSOSErrorNotReady, error, NULL, CFSTR("Unknown criticial extension in peer message"));
+        *stop = true;
+    });
+    require_quiet(ok, exit);
+
+    // Merge Objects from the message into our DataSource.
+    // Should we move the transaction to the SOSAccount level?
+    // TODO: Filter incoming objects
+    //if (!SOSDataSourceForEachObjectInViewSet(engine->dataSource, pendingObjects, SOSPeerGetViewNameSet(peer), error, ^void(CFDataRef key, SOSObjectRef object, bool *stop) {
+    require_quiet(ok &= SOSMessageWithSOSObjects(message, engine->dataSource, error, ^(SOSObjectRef peersObject, bool *stop) {
+        CFDataRef digest = SOSObjectCopyDigest(engine->dataSource, peersObject, error);
+        if (!digest) {
+            *stop = true;
+            *commit = false;
+            secerror("%@ peer sent bad object: %@, rolling back changes", SOSPeerGetID(peer), error ? *error : NULL);
+            return;
+        }
+        SOSDigestVectorAppend(&receivedObjects, CFDataGetBytePtr(digest));
+        SOSObjectRef mergedObject = NULL;
+        SOSMergeResult mr = SOSDataSourceMergeObject(engine->dataSource, txn, peersObject, &mergedObject, error);
+        // TODO: If the mr is kSOSMergeLocalObject most of the time (or all of the time),
+        // consider asking the peer to stop sending us objects, and send it objects instead.
+        ok &= (mr != kSOSMergeFailure);
+        if (!ok) {
+            *stop = true;
+            *commit = false;
+            // TODO: Might want to change to warning since the race of us locking after ckd sends us a message could cause db locked errors here.
+            secerror("%@ SOSDataSourceMergeObject failed %@ rolling back changes", SOSPeerGetID(peer), error ? *error : NULL);
+        } else if (mr==kSOSMergePeersObject || mr==kSOSMergeCreatedObject) {
+            *somethingChanged = true;
+        } else {
+            // mr == kSOSMergeLocalObject
+            if (!CFEqual(mergedObject, peersObject)) {
+                // Record this object as something we don't want peer to ever send us again.  By adding it to
+                // unwantedObjects we'll falsely claim to peer we have it until they tell us they don't have it anymore.
+                SOSDigestVectorAppend(&unwantedObjects, CFDataGetBytePtr(digest));
+            }
+            // Ensure localObject is in local manifest (possible corruption) by posting an update when we are done.
+            SOSChangesAppendAdd(changes, mergedObject);
+        }
+        CFReleaseSafe(mergedObject);
+        CFReleaseSafe(digest);
+    }), exit);
+    struct SOSDigestVector dvunion = SOSDigestVectorInit;
+    SOSDigestVectorSort(&receivedObjects);
+    SOSDigestVectorUnionSorted(SOSManifestGetDigestVector(SOSMessageGetAdditions(message)), &receivedObjects, &dvunion);
+    allAdditions = SOSManifestCreateWithDigestVector(&dvunion, error);
+    SOSDigestVectorFree(&receivedObjects);
+    SOSDigestVectorFree(&dvunion);
+
+    unwanted = SOSManifestCreateWithDigestVector(&unwantedObjects, error);
+    SOSDigestVectorFree(&unwantedObjects);
+
+    if (CFArrayGetCount(changes)) {
+        // NOTE: This is always notifiying of all additions that end up choosing local, which should be rare, since we shouldn't
+        // be receiving objects we already have.   When we do we tell ourselves to add them all again so our views will properly
+        // reflect that we actually have these objects if we didn't already.
+
+        // Ensure any objects that we received and have locally already are actually in our local manifest
+        SOSEngineUpdateChanges_locked(engine, NULL, kSOSDataSourceTransactionDidCommit, kSOSDataSourceSOSTransaction, changes, error);
+    }
+    CFReleaseSafe(changes);
+
+    // ---- Don't use local or peer manifests from above this line,
+    // ---- since commiting the SOSDataSourceWith transaction might change them ---
+
+    // Take a snapshot of our dataSource's local manifest.
+    require_quiet(ok = localManifest = SOSEngineCopyLocalPeerManifest_locked(engine, peer, error), exit);
+
+    CFDataRef baseDigest = SOSMessageGetBaseDigest(message);
+    CFDataRef proposedDigest = SOSMessageGetProposedDigest(message);
+    
+#if 0
+    // I believe this is no longer needed now that we have eliminated extra,
+    // since this is handled below once we get a confirmed manifest from our
+    // peer.
+    
+    // If we just received a L00 reset pendingObjects to localManifest
+    if (!baseDigest && !proposedDigest) {
+        // TODO: This is definitely busted for v0 peers since v0 peers always send a
+        // L00 (ManifestDigestMessage as an ack) whereas in v2 this is a protocol restart
+        // However if we can still find a confirmed manifest below we probably
+        // don't want to do this even for v2.
+        // Also I don't think we will ever send a ManifestMessage right now in
+        // response to a ManifestDigest
+        SOSPeerSetPendingObjects(peer, localManifest);
+        secnoticeq("engine", "%@:%@ SOSPeerSetPendingObjects: %@", engine->myID, peerID, localManifest);
+    }
+#endif
+
+    base = SOSPeerCopyManifestForDigest(peer, baseDigest);
+    confirmed = SOSPeerCopyManifestForDigest(peer, SOSMessageGetSenderDigest(message));
+    if (!confirmed) {
+        if (SOSManifestGetCount(SOSMessageGetRemovals(message)) || SOSManifestGetCount(allAdditions)) {
+            if (base || !baseDigest) {
+                confirmed = SOSManifestCreateWithPatch(base, SOSMessageGetRemovals(message), allAdditions, error);
+            }
+            if (!confirmed) {
+                confirmedRemovals = CFRetainSafe(SOSMessageGetRemovals(message));
+                confirmedAdditions = CFRetainSafe(allAdditions);
+            }
+        } else if (baseDigest) {
+            confirmed = CFRetainSafe(base);
+            secerror("%@:%@ Protocol error send L00 - figure out later base: %@", engine->myID, peerID, base);
+        }
+    }
+    secnoticeq("engine", "%@:%@ confirmed: %@ base: %@", engine->myID, peerID, confirmed, base);
+    if (confirmed) {
+        ok &= SOSManifestDiff(SOSPeerGetConfirmedManifest(peer), confirmed, &confirmedRemovals, &confirmedAdditions, error);
+        if (SOSManifestGetCount(SOSMessageGetRemovals(message)))
+            CFAssignRetained(confirmedRemovals, SOSManifestCreateUnion(confirmedRemovals, SOSMessageGetRemovals(message), error));
+    }
+    if (SOSManifestGetCount(confirmedRemovals) || SOSManifestGetCount(confirmedAdditions) || SOSManifestGetCount(unwanted))
+        ok &= SOSPeerDidReceiveRemovalsAndAdditions(peer, confirmedRemovals, confirmedAdditions, unwanted, localManifest, error);
+    // TODO: We should probably remove the if below and always call SOSPeerSetConfirmedManifest,
+    // since having a NULL confirmed will force us to send a manifest message to get in sync again.
+    if (confirmed)
+        SOSPeerSetConfirmedManifest(peer, confirmed);
+    else if (SOSPeerGetConfirmedManifest(peer)) {
+        secnoticeq("engine", "%@:%@ unable to find confirmed in %@, sync protocol reset", engine->myID, peer, message);
+
+        SOSPeerSetConfirmedManifest(peer, NULL);
+        //SOSPeerSetSendObjects(peer, true);
+    }
+
+    // ---- SendObjects and extra->pendingObjects promotion dance ----
+
+    // The first block of code below sets peer.sendObjects to true when we receive a L00 and the second block
+    // moves extra to pendingObjects once we receive a confirmed manifest in or after the L00.
+    if (!baseDigest && !proposedDigest) {
+        SOSPeerSetSendObjects(peer, true);
+    }
+
+    if (0 /* confirmed && SOSPeerSendObjects(peer) */) {
+        SOSManifestRef allExtra = NULL;
+        ok &= SOSManifestDiff(confirmed, localManifest, NULL, &allExtra, error);
+        secnoticeq("engine", "%@:%@ confirmed %@ (re)setting O:%@", engine->myID, SOSPeerGetID(peer), confirmed, allExtra);
+        SOSPeerSetPendingObjects(peer, allExtra);
+        CFReleaseSafe(allExtra);
+    }
+
+exit:
+    secinfo("engine", "recv %@:%@ %@", engine->myID, SOSPeerGetID(peer), message);
+    secinfo("peer", "recv %@ -> %@", peerDesc, peer);
+
+    CFReleaseNull(base);
+    CFReleaseSafe(confirmed);
+    CFReleaseSafe(localManifest);
+    CFReleaseSafe(peerDesc);
+    CFReleaseSafe(allAdditions);
+    CFReleaseSafe(unwanted);
+    CFReleaseSafe(confirmedRemovals);
+    CFReleaseSafe(confirmedAdditions);
+    CFReleaseSafe(peer);
+    return ok;
+}
+
+static CFDataRef SOSEngineCopyObjectDER(SOSEngineRef engine, SOSObjectRef object, CFErrorRef *error) {
+    CFDataRef der = NULL;
+    CFDictionaryRef plist = SOSObjectCopyPropertyList(engine->dataSource, object, error);
+    if (plist) {
+        der = CFPropertyListCreateDERData(kCFAllocatorDefault, plist, error);
+        CFRelease(plist);
+    }
+    return der;
+}
+
+
+/*
+
+            +-----------------------------+_
+            |            |                | \
+            |      A      |    T          |  \
+            |              |              |   \
+           _+=============================+    } L
+          / |                             |   /
+         /  |              S              |  /
+        /   |                             |_/
+       /    +==============================
+      /     |                             |
+   C {      |                             |
+      \     |        M       +------------|
+       \    |               |             |
+        \   |              |      U       |
+         \  |             |               |
+          \_+-------------+---------------+
+
+A assumed
+T to be sent
+S shared
+M missing
+U unwanted
+L local
+C confirmed
+
+*/
+#if 0
+static bool SOSAppendRemoveToPatch(CFTypeRef remove, CFMutableDictionaryRef patch, CFErrorRef *error) {
+}
+
+static bool SOSAppendAddToPatch(CFTypeRef add, CFMutableDictionaryRef patch, CFErrorRef *error) {
+}
+
+static bool SOSAppendDiffToPatch(CFTypeRef left, CFTypeRef right, CFMutableDictionaryRef patch, CFErrorRef *error) {
+    bool ok = true;
+    if (!left && right) {
+        SOSAppendAddToPatch(right, patch, error);
+    } else if (left && !right) {
+        SOSAppendRemoveToPatch(left, patch, error);
+    } else if (left && right) {
+        CFTypeID ltype = CFGetTypeID(left);
+        CFTypeID rtype = CFGetTypeID(right);
+        if (ltype == rtype) {
+            if (CFArrayGetTypeID() == ltype) {
+                ok = SecError(errSecParam, error, CFSTR("unsupported type array"), ltype);
+            } else if (CFBooleanGetTypeID == ltype) {
+                ok = SecError(errSecParam, error, CFSTR("unsupported type boolean"), ltype);
+            } else if (CFDataGetTypeID == ltype) {
+                ok = SecError(errSecParam, error, CFSTR("unsupported type data"), ltype);
+            } else if (CFDictionaryGetTypeID == ltype) {
+                __block CFMutableDictionaryRef leftnotright = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+                __block CFMutableDictionaryRef rightnotleft = CFDictionaryCreateMutableCopy(kCFAllocatorDefault, 0, right);
+
+                CFDictionaryForEach(left, ^(const void *key, const void *lvalue) {
+                    const void *rvalue = NULL;
+                    if (CFDictionaryGetValueIfPresent(right, key, &rvalue)) {
+                        CFDictionaryRemoveValue(rightnotleft, key);
+
+                        CFMutableDictionaryRef subpatch = CFDictionaryCreateForCFTypes(kCFAllocatorDefault);
+                        CFDictionaryAddValue(patch, key, subpatch);
+                        SOSAppendDiffToPatch(lvalue, rvalue, subpatch, error);
+                        CFReleaseSafe(subpatch);
+                    } else {
+                        CFDictionaryAddValue(leftnotright, key, lvalue);
+                    }
+                });
+                // Proccess leftnotright and rightnotleft
+                CFReleaseSafe(leftnotright);
+                CFReleaseSafe(rightnotleft);
+            } else if (SOSManifestGetTypeID == ltype) {
+                SOSManifestRef removed = NULL, added = NULL;
+                ok &= SOSManifestDiff(left, right, &removed, &added, error);
+                if (SOSManifestGetCount(removed) || SOSManifestGetCount(added)) {
+                    SOSAppendDiffToPatch(lvalue, rvalue, subpatch, error);
+                    CFStringAppend(, <#CFStringRef appendedString#>)
+                }
+                CFReleaseSafe(removed);
+                CFReleaseSafe(added);
+            } else if (CFNumberGetTypeID == ltype) {
+                ok = SecError(errSecParam, error, CFSTR("unsupported type number"), ltype);
+            } else if (CFSetGetTypeID == ltype) {
+                ok = SecError(errSecParam, error, CFSTR("unsupported type set"), ltype);
+            } else if (CFStringGetTypeID == ltype) {
+                ok = SecError(errSecParam, error, CFSTR("unsupported type string"), ltype);
+            } else {
+                ok = SecError(errSecParam, error, CFSTR("unknown type %lu"), ltype);
+            }
+        }
+    } else if (!left && !right) {
+        // NOOP
+    }
+}
+#endif
+
+static __unused bool SOSEngineCheckPeerIntegrity(SOSEngineRef engine, SOSPeerRef peer, CFErrorRef *error) {
+#if 0
+    //static CFMutableDictionaryRef p2amtu;
+    if (!engine->p2amtu)
+        engine->p2amtu = CFDictionaryCreateMutableForCFTypes(kCFAllocatorDefault);
+    CFDictionaryRef amtu = CFDictionaryGetValue(engine->p2amtu, SOSPeerGetID(peer));
+#endif
+
+    // Inputs
+    SOSManifestRef L = SOSEngineCopyLocalPeerManifest_locked(engine, peer, error);
+    SOSManifestRef T = SOSPeerGetPendingObjects(peer);
+    SOSManifestRef C = SOSPeerGetConfirmedManifest(peer);
+    SOSManifestRef U = SOSPeerGetUnwantedManifest(peer);
+
+    // Computed
+    SOSManifestRef CunionU = SOSManifestCreateUnion(C, U, error);
+    SOSManifestRef S = SOSManifestCreateIntersection(L, CunionU, error);
+
+    SOSManifestRef AunionT = NULL, MunionU = NULL;
+    SOSManifestDiff(L, C, &AunionT, &MunionU, error);
+
+    SOSManifestRef A = SOSManifestCreateComplement(T, AunionT, error);
+    SOSManifestRef M = SOSManifestCreateComplement(U, MunionU, error);
+
+    SOSManifestRef SunionAunionT = SOSManifestCreateUnion(S, AunionT, error);
+    SOSManifestRef SunionMunionU = SOSManifestCreateUnion(S, MunionU, error);
+
+    SOSManifestRef AintersectM = SOSManifestCreateIntersection(A, M, error);
+    SOSManifestRef AintersectS = SOSManifestCreateIntersection(A, S, error);
+    SOSManifestRef AintersectT = SOSManifestCreateIntersection(A, T, error);
+    SOSManifestRef AintersectU = SOSManifestCreateIntersection(A, U, error);
+    SOSManifestRef MintersectS = SOSManifestCreateIntersection(M, S, error);
+    SOSManifestRef MintersectT = SOSManifestCreateIntersection(M, T, error);
+    SOSManifestRef MintersectU = SOSManifestCreateIntersection(M, U, error);
+    SOSManifestRef SintersectT = SOSManifestCreateIntersection(S, T, error);
+    SOSManifestRef SintersectU = SOSManifestCreateIntersection(S, U, error);
+    SOSManifestRef TintersectU = SOSManifestCreateIntersection(T, U, error);
+
+#if 0
+    CFDictionaryRef newAmtu = CFDictionaryCreateForCFTypes(kCFAllocatorDefault, CFSTR("A"), A, CFSTR("M"), M, CFSTR("T"), T, CFSTR("U") U, NULL);
+    CFDictionarySetValue(engine->p2amtu, SOSPeerGetID(peer), newAmtu);
+    CFMutableStringRef amtuChanges = CFStringCreateMutable(kCFAllocatorDefault, 0);
+    SOSAppendDiffToString(amtu, newAmtu, amtuChanges);
+    secnotice("engine", "%@: %@", SOSPeerGetID(peer), amtuChanges);
+#endif
+
+#define SOSASSERT(e)      (__builtin_expect(!(e), 0) ? secnotice("engine", "state-assertion %s", #e), assert(e) : (void)0)
+
+    SOSASSERT(L ? CFEqual(L, SunionAunionT) : SOSManifestGetCount(SunionAunionT) == 0);
+    SOSASSERT(C ? CFEqual(C, SunionMunionU) : SOSManifestGetCount(SunionMunionU) == 0);
+
+    SOSASSERT(SOSManifestGetCount(AintersectM) == 0);
+    SOSASSERT(SOSManifestGetCount(AintersectS) == 0);
+    SOSASSERT(SOSManifestGetCount(AintersectT) == 0);
+    SOSASSERT(SOSManifestGetCount(AintersectU) == 0);
+    SOSASSERT(SOSManifestGetCount(MintersectS) == 0);
+    SOSASSERT(SOSManifestGetCount(MintersectT) == 0);
+    SOSASSERT(SOSManifestGetCount(MintersectU) == 0);
+    SOSASSERT(SOSManifestGetCount(SintersectT) == 0);
+    SOSASSERT(SOSManifestGetCount(SintersectU) == 0);
+    SOSASSERT(SOSManifestGetCount(TintersectU) == 0);
+
+    CFReleaseSafe(AintersectM);
+    CFReleaseSafe(AintersectS);
+    CFReleaseSafe(AintersectT);
+    CFReleaseSafe(AintersectU);
+    CFReleaseSafe(MintersectS);
+    CFReleaseSafe(MintersectT);
+    CFReleaseSafe(MintersectU);
+    CFReleaseSafe(SintersectT);
+    CFReleaseSafe(SintersectU);
+    CFReleaseSafe(TintersectU);
+
+    CFReleaseSafe(AunionT);
+    CFReleaseSafe(MunionU);
+
+
+    CFReleaseSafe(A);
+    CFReleaseSafe(M);
+    CFReleaseSafe(S);
+    //CFReleaseSafe(T); // Get
+    //CFReleaseSafe(U); // Get
+    //CFReleaseSafe(C); // Get
+    CFReleaseSafe(L);
+    return true;
+}
+
+void SOSEngineSetSyncCompleteListener(SOSEngineRef engine, CFStringRef peerID, dispatch_block_t notify_block) {
+    dispatch_block_t copy = Block_copy(notify_block);
+    SOSEngineDoOnQueue(engine, ^{
+        if (notify_block) {
+            CFDictionarySetValue(engine->syncCompleteListeners, peerID, copy);
+        } else {
+            CFDictionaryRemoveValue(engine->syncCompleteListeners, peerID);
+        }
+    });
+    CFReleaseNull(copy);
+}
+
+void SOSEngineSetSyncCompleteListenerQueue(SOSEngineRef engine, dispatch_queue_t notify_queue) {
+    SOSEngineDoOnQueue(engine, ^{
+        engine->syncCompleteQueue = notify_queue;
+    });
+}
+
+static void SOSEngineCompletedSyncWithPeer(SOSEngineRef engine, SOSPeerRef peer) {
+    dispatch_block_t notify = CFDictionaryGetValue(engine->syncCompleteListeners, SOSPeerGetID(peer));
+    if (notify && engine->syncCompleteQueue)
+        dispatch_async(engine->syncCompleteQueue, notify);
+
+    // Delete dictionary entry?
+}
+
+
+CFDataRef SOSEngineCreateMessage_locked(SOSEngineRef engine, SOSPeerRef peer,
+                                        CFErrorRef *error, SOSEnginePeerMessageSentBlock *sent) {
+    SOSManifestRef local = SOSEngineCopyLocalPeerManifest_locked(engine, peer, error);
+    __block SOSMessageRef message = SOSMessageCreate(kCFAllocatorDefault, SOSPeerGetMessageVersion(peer), error);
+    SOSManifestRef confirmed = SOSPeerGetConfirmedManifest(peer);
+    SOSManifestRef pendingObjects = SOSPeerGetPendingObjects(peer);
+    SOSManifestRef objectsSent = NULL;
+    SOSManifestRef proposed = NULL;
+    SOSManifestRef allMissing = NULL;
+    SOSManifestRef allExtra = NULL;
+    SOSManifestRef extra = NULL;
+    SOSManifestRef excessPending = NULL;
+    SOSManifestRef missing = NULL;
+    SOSManifestRef unwanted = SOSPeerGetUnwantedManifest(peer);
+    SOSManifestRef excessUnwanted = NULL;
+    CFDataRef result = NULL;
+
+    // Given (C, L, T, U) compute (T, U, M, A)
+    // (C \ L) \ U => M
+    // (L \ C) \ T => A
+    // we also compute
+    // U \ (C \ L) => EU
+    // T \ (L \ C) => ET
+    // And assert that both EU and ET are empty and if not remove them from U and T respectively
+    SOSManifestDiff(confirmed, local, &allMissing, &allExtra, error);
+    SOSManifestDiff(allExtra, pendingObjects, &extra, &excessPending, error);
+    if (SOSManifestGetCount(excessPending)) {
+        // T \ (L \ C) => excessPending (items both in L and C or in neither that are still pending)
+        // Can only happen if a member of T was removed from L without us having a chance to update T
+        secerror("%@ ASSERTION FAILURE purging excess pendingObjects: %@", peer, excessPending);
+        SOSManifestRef newPendingObjects = SOSManifestCreateComplement(excessPending, pendingObjects, error);
+        SOSPeerSetPendingObjects(peer, newPendingObjects);
+        CFReleaseSafe(newPendingObjects);
+        pendingObjects = SOSPeerGetPendingObjects(peer);
+    }
+    SOSManifestDiff(allMissing, unwanted, &missing, &excessUnwanted, error);
+    if (SOSManifestGetCount(excessUnwanted)) {
+        // U \ (C \ L) => excessUnwanted (items both in L and C or in neither that are still unwanted)
+        // Can only happen if a member of U was added to L without us having a chance to update U.
+        // Since U only contains items the conflict resolver rejected, this implies L somehow got rolled back
+        // The other option (and more likely) is a member of U was removed from C and not from U.
+        secerror("%@ ASSERTION FAILURE purging excess unwanted: %@", peer, excessUnwanted);
+        SOSManifestRef newUnwanted = SOSManifestCreateComplement(excessUnwanted, unwanted, error);
+        SOSPeerSetUnwantedManifest(peer, newUnwanted);
+        CFReleaseSafe(newUnwanted);
+        unwanted = SOSPeerGetUnwantedManifest(peer);
+    }
+
+    CFReleaseNull(allExtra);
+    CFReleaseNull(excessPending);
+    CFReleaseNull(allMissing);
+    CFReleaseNull(excessUnwanted);
+
+    secnoticeq("engine", "%@:%@: send state for peer [%s%s%s][%s%s] P:%zu, E:%zu, M:%zu U:%zu", engine->myID, SOSPeerGetID(peer),
+               local ? "L":"l",
+               confirmed ? "C":"0",
+               pendingObjects ? "P":"0",
+               SOSPeerSendObjects(peer) ? "O":"o",
+               SOSPeerMustSendMessage(peer) ? "S":"s",
+               SOSManifestGetCount(pendingObjects),
+               SOSManifestGetCount(extra),
+               SOSManifestGetCount(missing),
+               SOSManifestGetCount(unwanted)
+               );
+
+    if (confirmed) {
+        // TODO: Because of not letting things terminate while we have extra left
+        // we might send objects when we didn't need to, but there is always an
+        // extra roundtrip required for objects that we assume the other peer
+        // should have already.
+        // TODO: If there are extra objects left, calling this function is not
+        // idempotent we should check if pending is what we are about to send and not send anything in this case.
+        if (SOSManifestGetCount(pendingObjects) == 0 && SOSManifestGetCount(extra) == 0)
+            SOSPeerSetSendObjects(peer, false);
+
+        if (CFEqualSafe(local, SOSPeerGetProposedManifest(peer)) && !SOSPeerMustSendMessage(peer)) {
+            bool send = false;
+            if (CFEqual(confirmed, local)) {
+                SOSEngineCompletedSyncWithPeer(engine, peer);
+                secnoticeq("engine", "synced <No MSG> %@:%@", engine->myID,  peer);
+            } else if (SOSManifestGetCount(pendingObjects) == 0 /* TODO: No entries moved from extra to pendingObjects. */
+                       && SOSManifestGetCount(missing) == 0) {
+                secnoticeq("engine", "waiting <MSG not resent> %@:%@ extra: %@", engine->myID, peer, extra);
+            } else {
+                send = true;
+            }
+            if (!send) {
+                CFReleaseSafe(local);
+                CFReleaseSafe(message);
+                CFReleaseNull(extra);
+                CFReleaseNull(missing);
+                return CFDataCreate(kCFAllocatorDefault, NULL, 0);
+            }
+        }
+
+        if (SOSManifestGetCount(pendingObjects)) {
+            // If we have additions and we need to send objects, do so.
+            __block size_t objectsSize = 0;
+            __block struct SOSDigestVector dv = SOSDigestVectorInit;
+            CFMutableArrayRef changes = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+            if (!SOSDataSourceForEachObject(engine->dataSource, pendingObjects, error, ^void(CFDataRef key, SOSObjectRef object, bool *stop) {
+                CFErrorRef localError = NULL;
+                CFDataRef digest = NULL;
+                CFDataRef der = NULL;
+                if (!object) {
+                    const uint8_t *d = CFDataGetBytePtr(key);
+                    secnoticeq("engine", "%@:%@ object %02X%02X%02X%02X dropping from manifest: not found in datasource",
+                               engine->myID, SOSPeerGetID(peer), d[0], d[1], d[2], d[3]);
+                    SOSChangesAppendDelete(changes, key);
+                } else if (!(der = SOSEngineCopyObjectDER(engine, object, &localError))
+                           || !(digest = SOSObjectCopyDigest(engine->dataSource, object, &localError))) {
+                    if (SecErrorGetOSStatus(localError) == errSecDecode) {
+                        // Decode error, we need to drop these objects from our manifests
+                        const uint8_t *d = CFDataGetBytePtr(key);
+                        secnoticeq("engine", "%@:%@ object %02X%02X%02X%02X dropping from manifest: %@",
+                            engine->myID, SOSPeerGetID(peer), d[0], d[1], d[2], d[3], localError);
+                        SOSChangesAppendDelete(changes, key);
+                        CFRelease(localError);
+                    } else {
+                        // Stop iterating and propagate out all other errors.
+                        const uint8_t *d = CFDataGetBytePtr(key);
+                        secnoticeq("engine", "%@:%@ object %02X%02X%02X%02X in SOSDataSourceForEachObject: %@",
+                            engine->myID, SOSPeerGetID(peer), d[0], d[1], d[2], d[3], localError);
+                        *stop = true;
+                        CFErrorPropagate(localError, error);
+                        CFReleaseNull(message);
+                    }
+                } else {
+                    if (!CFEqual(key, digest)) {
+                        const uint8_t *d = CFDataGetBytePtr(key);
+                        const uint8_t *e = CFDataGetBytePtr(digest);
+                        secnoticeq("engine", "%@:%@ object %02X%02X%02X%02X is really %02X%02X%02X%02X dropping from local manifest",
+                                   engine->myID, SOSPeerGetID(peer), d[0], d[1], d[2], d[3], e[0], e[1], e[2], e[3]);
+                        SOSChangesAppendDelete(changes, key);
+                        SOSChangesAppendAdd(changes, object); // This is new behaviour but we think it's more correct
+                    }
+
+                    size_t objectLen = (size_t)CFDataGetLength(der);
+                    if (SOSMessageAppendObject(message, der, &localError)) {
+                        SOSDigestVectorAppend(&dv, CFDataGetBytePtr(digest));
+                    } else {
+                        const uint8_t *d = CFDataGetBytePtr(digest);
+                        CFStringRef hexder = CFDataCopyHexString(der);
+                        secnoticeq("engine", "%@:%@ object %02X%02X%02X%02X der: %@ dropping from manifest: %@",
+                                  engine->myID, SOSPeerGetID(peer), d[0], d[1], d[2], d[3], hexder, localError);
+                        CFReleaseNull(hexder);
+                        CFReleaseNull(message);
+                        // Since we can't send these objects let's assume they are bad too?
+                        SOSChangesAppendDelete(changes, digest);
+                    }
+                    objectsSize += objectLen;
+                    if (objectsSize > kSOSMessageMaxObjectsSize)
+                        *stop = true;
+                }
+                CFReleaseSafe(der);
+                CFReleaseSafe(digest);
+            })) {
+                CFReleaseNull(message);
+            }
+            if (dv.count)
+                objectsSent = SOSManifestCreateWithDigestVector(&dv, error);
+            if (CFArrayGetCount(changes)) {
+                CFErrorRef localError = NULL;
+                if (!SOSEngineUpdateChanges_locked(engine, NULL, kSOSDataSourceTransactionDidCommit, kSOSDataSourceSOSTransaction, changes, &localError))
+                    secerror("SOSEngineUpdateChanges_locked: %@ failed: %@", changes, localError);
+                CFReleaseSafe(localError);
+                CFAssignRetained(local, SOSEngineCopyLocalPeerManifest_locked(engine, peer, error));
+            }
+            CFReleaseSafe(changes);
+        }
+    } else {
+        // If we have no confirmed manifest, we want all pendedObjects going out as a manifest
+        objectsSent = CFRetainSafe(pendingObjects);
+    }
+
+    if (confirmed || SOSManifestGetCount(missing) || SOSManifestGetCount(extra) || objectsSent) {
+        SOSManifestRef allExtra = SOSManifestCreateUnion(extra, objectsSent, error);
+        proposed = SOSManifestCreateWithPatch(confirmed, missing, allExtra, error);
+        CFReleaseNull(allExtra);
+    }
+
+    if (!SOSMessageSetManifests(message, local, confirmed, proposed, proposed, confirmed ? objectsSent : NULL, error))
+        CFReleaseNull(message);
+
+    CFReleaseNull(objectsSent);
+
+    if (message) {
+        result = SOSMessageCreateData(message, SOSPeerNextSequenceNumber(peer), error);
+    }
+    
+    if (result) {
+        // Capture the peer in our block (SOSEnginePeerMessageSentBlock)
+        CFRetainSafe(peer);
+        *sent = Block_copy(^(bool success) {
+            dispatch_async(engine->queue, ^{
+            if (success) {
+                SOSPeerSetMustSendMessage(peer, false);
+                if (!confirmed && !proposed) {
+                    SOSPeerSetSendObjects(peer, true);
+                    secnoticeq("engine", "%@:%@ sendObjects=true L:%@", engine->myID, SOSPeerGetID(peer), local);
+                }
+                SOSPeerAddLocalManifest(peer, local);
+                SOSPeerAddProposedManifest(peer, proposed);
+                secnoticeq("engine", "send %@:%@ %@", engine->myID, SOSPeerGetID(peer), message);
+                //SOSEngineCheckPeerIntegrity(engine, peer, NULL);
+            } else {
+                secerror("%@:%@ failed to send %@", engine->myID, SOSPeerGetID(peer), message);
+            }
+            CFReleaseSafe(peer);
+            CFReleaseSafe(local);
+            CFReleaseSafe(proposed);
+            CFReleaseSafe(message);
+            });
+        });
+    } else {
+        CFReleaseSafe(local);
+        CFReleaseSafe(proposed);
+        CFReleaseSafe(message);
+    }
+    CFReleaseNull(extra);
+    CFReleaseNull(missing);
+    if (error && *error)
+        secerror("%@:%@ error in send: %@", engine->myID, SOSPeerGetID(peer), *error);
+
+    return result;
+}
+
+static void SOSEngineLogItemError(SOSEngineRef engine, CFStringRef peerID, CFDataRef key, CFDataRef optionalDigest, const char *where, CFErrorRef error) {
+    if (!optionalDigest) {
+        const uint8_t *d = CFDataGetBytePtr(key);
+        secwarning("%@:%@ object %02X%02X%02X%02X %s: %@", engine->myID, peerID, d[0], d[1], d[2], d[3], where, error ? (CFTypeRef)error : CFSTR(""));
+    } else {
+        const uint8_t *d = CFDataGetBytePtr(key);
+        const uint8_t *e = CFDataGetBytePtr(optionalDigest);
+        secwarning("%@:%@ object %02X%02X%02X%02X is really %02X%02X%02X%02X dropping from local manifest", engine->myID, peerID, d[0], d[1], d[2], d[3], e[0], e[1], e[2], e[3]);
+    }
+}
+
+static bool SOSEngineWriteToBackup_locked(SOSEngineRef engine, SOSPeerRef peer, bool rewriteComplete, bool *didWrite, bool *incomplete, CFErrorRef *error) {
+    __block bool ok = SOSPeerWritePendingReset(peer, error);
+    if (!ok || !SOSPeerGetKeyBag(peer))
+        return ok;
+    __block SOSManifestRef local = SOSEngineCopyLocalPeerManifest_locked(engine, peer, error);
+    __block SOSManifestRef proposed = SOSPeerGetProposedManifest(peer);
+    __block bool notify = true;
+    SOSManifestRef pendingObjects = NULL;
+    SOSManifestRef missing = NULL;
+    CFStringRef peerID = SOSPeerGetID(peer);
+
+    ok &= SOSManifestDiff(proposed, local, &missing, &pendingObjects, error);
+
+    secnoticeq("engine", "%@:%@: Send state for peer [%s%s%s] O: %zu, M: %zu", engine->myID, peerID,
+               local ? "L":"l",
+               proposed ? "P":"0",
+               pendingObjects ? "O":"0",
+               SOSManifestGetCount(pendingObjects),
+               SOSManifestGetCount(missing));
+
+    if (SOSManifestGetCount(missing) == 0 && SOSManifestGetCount(pendingObjects) == 0) {
+        // proposed == local (faster test than CFEqualSafe above), since we
+        // already did the SOSManifestDiff
+        if (rewriteComplete) {
+            notify = false;
+        } else {
+            secnoticeq("engine", "%@:%@ backup still done", engine->myID, peer);
+            goto done;
+        }
+    }
+    ok &= SOSPeerAppendToJournal(peer, error, ^(FILE *journalFile, keybag_handle_t kbhandle) {
+        SOSManifestRef objectsSent = NULL;
+        __block struct SOSDigestVector dvdel = SOSDigestVectorInit;
+        __block struct SOSDigestVector dvadd = SOSDigestVectorInit;
+        SOSManifestForEach(missing, ^(CFDataRef key, bool *stop) {
+            CFErrorRef localError = NULL;
+            if (ftello(journalFile) > kSOSBackupMaxFileSize) {
+                // Highwatermark hit on file.
+                *stop = true;
+            } else if (SOSBackupEventWriteDelete(journalFile, key, &localError)) {
+                SOSDigestVectorAppend(&dvdel, CFDataGetBytePtr(key));
+            } else {
+                SOSEngineLogItemError(engine, peerID, key, NULL, "in SOSPeerWriteDelete", localError);
+                CFErrorPropagate(localError, error);
+                // TODO: Update of missing so proposed is updated properly
+                *stop = true; // Disk full?
+                ok = false;
+            }
+        });
+        if (ok && SOSManifestGetCount(pendingObjects)) {
+            CFMutableArrayRef changes = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+            ok &= SOSDataSourceForEachObject(engine->dataSource, pendingObjects, error, ^void(CFDataRef key, SOSObjectRef object, bool *stop) {
+                CFErrorRef localError = NULL;
+                CFDataRef digest = NULL;
+                CFDictionaryRef backupItem = NULL;
+                if (ftello(journalFile) > kSOSBackupMaxFileSize) {
+                    // Highwatermark hit on file.
+                    *stop = true;
+                } else if (!object) {
+                    SOSEngineLogItemError(engine, peerID, key, NULL, "dropping from manifest: not found in datasource", localError);
+                    SOSChangesAppendDelete(changes, key);
+                } else if (!(backupItem = SOSObjectCopyBackup(engine->dataSource, object, kbhandle, &localError))
+                           || !(digest = SOSObjectCopyDigest(engine->dataSource, object, &localError))) {
+                    if (SecErrorGetOSStatus(localError) == errSecDecode) {
+                        // Decode error, we need to drop these objects from our manifests
+                        SOSEngineLogItemError(engine, peerID, key, NULL, "dropping from manifest", localError);
+                        SOSChangesAppendDelete(changes, key);
+                        CFRelease(localError);
+                    } else {
+                        // Stop iterating and propagate out all other errors.
+                        SOSEngineLogItemError(engine, peerID, key, NULL, "in SOSDataSourceForEachObject", localError);
+                        *stop = true;
+                        CFErrorPropagate(localError, error);
+                        ok = false;
+                    }
+                } else {
+                    if (!CFEqual(key, digest)) {
+                        SOSEngineLogItemError(engine, peerID, key, digest, "", NULL);
+                        SOSChangesAppendDelete(changes, key);
+                        SOSChangesAppendAdd(changes, object); // This is new behaviour but we think it's more correct
+                    }
+
+                    if (SOSBackupEventWriteAdd(journalFile, backupItem, &localError)) {
+                        SOSDigestVectorAppend(&dvadd, CFDataGetBytePtr(digest));
+                    } else {
+                        SOSEngineLogItemError(engine, peerID, key, NULL, "in SOSPeerWriteAdd", localError);
+                        *stop = true; // Disk full?
+                        CFErrorPropagate(localError, error);
+                        ok = false;
+                    }
+                }
+                CFReleaseSafe(backupItem);
+                CFReleaseSafe(digest);
+            });
+            if (CFArrayGetCount(changes)) {
+                CFErrorRef localError = NULL;
+                if (!SOSEngineUpdateChanges_locked(engine, NULL, kSOSDataSourceTransactionDidCommit, kSOSDataSourceSOSTransaction, changes, &localError))
+                    secerror("SOSEngineUpdateChanges_locked: %@ failed: %@", changes, localError);
+                CFReleaseSafe(localError);
+                // Since calling SOSEngineUpdateChanges_locked might cause local to change and might cause the backup peer to update proposed, refetch them here.
+                CFAssignRetained(local, SOSEngineCopyLocalPeerManifest_locked(engine, peer, error));
+                proposed = SOSPeerGetProposedManifest(peer);
+            }
+            CFReleaseSafe(changes);
+        }
+
+        if (dvadd.count || (proposed && dvdel.count)) {
+            *didWrite = true;
+            SOSManifestRef deleted = SOSManifestCreateWithDigestVector(&dvdel, error);
+            SOSManifestRef objectsSent = SOSManifestCreateWithDigestVector(&dvadd, error);
+            SOSManifestRef newProposed = SOSManifestCreateWithPatch(proposed, deleted, objectsSent, error);
+            CFReleaseSafe(deleted);
+            CFReleaseSafe(objectsSent);
+            SOSPeerSetProposedManifest(peer, newProposed);
+            CFReleaseSafe(newProposed);
+            proposed = SOSPeerGetProposedManifest(peer);
+        }
+        SOSDigestVectorFree(&dvdel);
+        SOSDigestVectorFree(&dvadd);
+
+        // TODO: If proposed is NULL, and local is empty we should still consider ourselves done.
+        // It so happens this can't happen in practice today since there is at least a backupbag
+        // in the backup, but this is a bug waiting to rear its head in the future.
+        if (ok && CFEqualSafe(local, proposed)) {
+            CFErrorRef localError = NULL;
+            if (SOSBackupEventWriteCompleteMarker(journalFile, 899, &localError)) {
+                SOSPeerSetSendObjects(peer, true);
+                *didWrite = true;
+                secnoticeq("backup", "%@:%@ backup done%s", engine->myID, peerID, notify ? " notifying sbd" : "");
+                // TODO: Now switch to changes based writing to backup sync.
+                // Currently we leave changes enabled but we probably shouldn't
+            } else {
+                secwarning("%@:%@ in SOSBackupPeerWriteCompleteMarker: %@", engine->myID, peerID, localError);
+                ok = false;
+                *incomplete = true;
+                CFErrorPropagate(localError, error);
+            }
+        } else {
+            secnoticeq("backup", "%@:%@ backup incomplete [%zu/%zu]%s", engine->myID, peerID, SOSManifestGetCount(local), SOSManifestGetCount(proposed), notify ? " notifying sbd" : "");
+            *incomplete = true;
+        }
+        CFReleaseNull(objectsSent);
+    });
+    if (notify)
+        SOSBackupPeerPostNotification("writing changes to backup");
+
+done:
+    CFReleaseSafe(local);
+    CFReleaseNull(pendingObjects);
+    CFReleaseNull(missing);
+
+    return ok;
+}
+
+bool SOSEngineSyncWithPeers(SOSEngineRef engine, CFTypeRef idsTransport, CFTypeRef kvsTransport, CFErrorRef *error) {
+    __block bool ok = true;
+    __block bool incomplete = false;
+    ok &= SOSEngineDoTxnOnQueue(engine, error, ^(SOSTransactionRef txn, bool *commit) {
+        __block bool dirty = false;
+        SOSEngineForEachBackupPeer_locked(engine, ^(SOSPeerRef peer) {
+            ok = SOSEngineWriteToBackup_locked(engine, peer, false, &dirty, &incomplete, error);
+        });
+
+        if (dirty)
+            ok = SOSEngineSave(engine, txn, error);
+    });
+    if (incomplete) {
+        // Ensure we get called again in a while (after a backup timeout)
+        // sbd will do this since we never wrote a complete marker.
+        // TODO: This relies on us not writing complete marker for update
+        // event while we havn't finished a full backup, which we currently still do.
+    }
+    return ok;
+}
+
+bool SOSEngineHandleMessage(SOSEngineRef engine, CFStringRef peerID,
+                            CFDataRef raw_message, CFErrorRef *error)
+{
+    __block bool result = true;
+    __block bool somethingChanged = false;
+    SOSMessageRef message = SOSMessageCreateWithData(kCFAllocatorDefault, raw_message, error);
+    result &= message && SOSEngineDoTxnOnQueue(engine, error, ^(SOSTransactionRef txn, bool *commit) {
+        result = SOSEngineHandleMessage_locked(engine, peerID, message, txn, commit, &somethingChanged, error);
+    });
+    CFReleaseSafe(message);
+    if (somethingChanged)
+        SecKeychainChanged(false);
+    return result;
+}
+
+void SOSEngineCircleChanged(SOSEngineRef engine, CFStringRef myPeerID, CFArrayRef trustedPeers, CFArrayRef untrustedPeers) {
+    __block bool peersOrViewsChanged = false;
+    SOSEngineDoOnQueue(engine, ^{
+        peersOrViewsChanged = SOSEngineCircleChanged_locked(engine, myPeerID, trustedPeers, untrustedPeers);
+    });
+
+    __block bool ok = true;
+    __block CFErrorRef localError = NULL;
+    ok &= SOSEngineDoTxnOnQueue(engine, &localError, ^(SOSTransactionRef txn, bool *commit) {
+        ok = *commit = SOSEngineSave(engine, txn, &localError);
+    });
+    if (!ok) {
+        secerror("failed to save engine state: %@", localError);
+        CFReleaseSafe(localError);
+    }
+
+    if (peersOrViewsChanged)
+        SOSCCSyncWithAllPeers();
+}
+
+SOSManifestRef SOSEngineCopyManifest(SOSEngineRef engine, CFErrorRef *error) {
+    __block SOSManifestRef result = NULL;
+    SOSEngineDoOnQueue(engine, ^{
+        result = SOSEngineCopyManifestWithViewNameSet_locked(engine, SOSViewsGetV0ViewSet(), error);
+    });
+    return result;
+}
+
+SOSManifestRef SOSEngineCopyLocalPeerManifest(SOSEngineRef engine, SOSPeerRef peer, CFErrorRef *error) {
+    __block SOSManifestRef result = NULL;
+    SOSEngineDoOnQueue(engine, ^{
+        result = SOSEngineCopyLocalPeerManifest_locked(engine, peer, error);
+    });
+    return result;
+}
+
+bool SOSEngineUpdateChanges(SOSEngineRef engine, SOSDataSourceTransactionSource source, CFArrayRef changes, CFErrorRef *error) {
+    __block bool result = true;
+    SOSEngineDoOnQueue(engine, ^{
+        result = SOSEngineUpdateChanges_locked(engine, NULL, kSOSDataSourceTransactionDidCommit, source, changes, error);
+    });
+    return result;
+}
+
+//
+// Peer state layout.  WRONG! It's an array now
+// The peer state is an array.
+// The first element of the array is a dictionary with any number of keys and
+// values in it (for future expansion) such as changing the digest size or type
+// or remebering boolean flags for a peers sake.
+// The next three are special in that they are manifest digests with special
+// meaning and rules as to how they are treated (These are dynamically updated
+// based on database activity so they have a fully history of all changes made
+// to the local db. The first is the manifest representing the pendingObjects
+// to send to the other peer.  This is normally only ever appending to, and in
+// particular with transactions originating from the Keychain API that affect
+// syncable items will need to add the new objects digests to the pendingObjects list
+// while adding the digests of any tombstones encountered to the extra list.
+
+SOSPeerRef SOSEngineCopyPeerWithID(SOSEngineRef engine, CFStringRef peer_id, CFErrorRef *error) {
+    __block SOSPeerRef peer = NULL;
+    SOSEngineDoOnQueue(engine, ^{
+        peer = SOSEngineCopyPeerWithID_locked(engine, peer_id, error);
+    });
+    return peer;
+}
+
+bool SOSEngineForPeerID(SOSEngineRef engine, CFStringRef peerID, CFErrorRef *error, void (^forPeer)(SOSPeerRef peer)) {
+    __block bool ok = true;
+    SOSEngineDoOnQueue(engine, ^{
+        SOSPeerRef peer = SOSEngineCopyPeerWithID_locked(engine, peerID, error);
+        if (peer) {
+            forPeer(peer);
+            CFRelease(peer);
+        } else {
+            ok = false;
+        }
+    });
+    return ok;
+}
+
+bool SOSEngineWithPeerID(SOSEngineRef engine, CFStringRef peerID, CFErrorRef *error, void (^with)(SOSPeerRef peer, SOSDataSourceRef dataSource, SOSTransactionRef txn, bool *forceSaveState)) {
+    __block bool result = true;
+    result &= SOSEngineDoTxnOnQueue(engine, error, ^(SOSTransactionRef txn, bool *commit) {
+        SOSPeerRef peer = SOSEngineCopyPeerWithID_locked(engine, peerID, error);
+        if (!peer) {
+            result = SOSErrorCreate(kSOSErrorPeerNotFound, error, NULL, CFSTR("Engine has no peer for %@"), peerID);
+        } else {
+            bool saveState = false;
+            with(peer, engine->dataSource, txn, &saveState);
+            CFReleaseSafe(peer);
+            if (saveState)
+                result = SOSEngineSave(engine, txn, error);
+            // TODO: Don't commit if engineSave fails?
+        }
+    });
+
+    return result;
+}
+
+CFDataRef SOSEngineCreateMessageToSyncToPeer(SOSEngineRef engine, CFStringRef peerID, SOSEnginePeerMessageSentBlock *sentBlock, CFErrorRef *error) {
+    __block CFDataRef message = NULL;
+    SOSEngineForPeerID(engine, peerID, error, ^(SOSPeerRef peer) {
+        message = SOSEngineCreateMessage_locked(engine, peer, error, sentBlock);
+    });
+    return message;
+}
+
+bool SOSEnginePeerDidConnect(SOSEngineRef engine, CFStringRef peerID, CFErrorRef *error) {
+    return SOSEngineWithPeerID(engine, peerID, error, ^(SOSPeerRef peer, SOSDataSourceRef dataSource, SOSTransactionRef txn, bool *saveState) {
+        *saveState = SOSPeerDidConnect(peer);
+    });
+}
+
+bool SOSEngineSetPeerConfirmedManifest(SOSEngineRef engine, CFStringRef backupName,
+                                       CFDataRef keybagDigest, CFDataRef manifestData, CFErrorRef *error) {
+    __block bool ok = true;
+
+    ok &= SOSEngineForPeerID(engine, backupName, error, ^(SOSPeerRef peer) {
+        bool dirty = false;
+        bool incomplete = false;
+        SOSManifestRef confirmed = NULL;
+        CFDataRef keybag = SOSPeerGetKeyBag(peer);
+        CFDataRef computedKeybagDigest = keybag ? CFDataCopySHA1Digest(keybag, NULL) : NULL;
+        if (CFEqualSafe(keybagDigest, computedKeybagDigest)) {
+            ok = confirmed = SOSManifestCreateWithData(manifestData, error);
+            if (ok) {
+                // Set both confirmed and proposed (confirmed is just
+                // for debug status, proposed is actually what's used
+                // by the backup peer).
+                SOSPeerSetConfirmedManifest(peer, confirmed);
+                SOSPeerSetProposedManifest(peer, confirmed);
+            }
+        } else {
+            // sbd missed a reset event, send it again
+            // Force SOSEngineWriteToBackup_locked to call SOSPeerWriteReset, which clears
+            // confirmed and proposed manifests and writes the keybag to the journal.
+            SOSPeerSetMustSendMessage(peer, true);
+        }
+
+        // Stop changes from writing complete markers, unless SOSEngineWriteToBackup_locked() detects we are in sync
+        SOSPeerSetSendObjects(peer, false);
+        // Write data for this peer if we can, technically not needed for non legacy protocol support all the time.
+        ok = SOSEngineWriteToBackup_locked(engine, peer, true, &dirty, &incomplete, error);
+
+        CFReleaseSafe(confirmed);
+        CFReleaseSafe(computedKeybagDigest);
+    });
+    return ok;
+}
+
+CFArrayRef SOSEngineCopyBackupPeerNames(SOSEngineRef engine, CFErrorRef *error) {
+    __block CFMutableArrayRef backupNames = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+    SOSEngineForEachBackupPeer(engine, ^(SOSPeerRef peer) {
+        CFArrayAppendValue(backupNames, SOSPeerGetID(peer));
+    });
+    return backupNames;
+}
+
+static CFStringRef CFStringCreateWithViewNameSet(CFSetRef vns) {
+    CFIndex count = CFSetGetCount(vns);
+    CFMutableArrayRef mvn = CFArrayCreateMutableForCFTypesWithCapacity(kCFAllocatorDefault, count);
+    CFSetForEach(vns, ^(const void *value) {
+        CFArrayAppendValue(mvn, value);
+    });
+    CFArraySortValues(mvn, CFRangeMake(0, count), (CFComparatorFunction)CFStringCompare, 0);
+    CFStringRef string = CFStringCreateByCombiningStrings(kCFAllocatorDefault, mvn, CFSTR(":"));
+    CFRelease(mvn);
+    return string;
+}
+
+static CFStringRef CFStringCreateWithLabelAndViewNameSetDescription(CFStringRef label, CFStringRef peerID, CFSetRef vns, SOSManifestRef manifest) {
+    CFStringRef vnsDesc = CFStringCreateWithViewNameSet(vns);
+    CFStringRef desc;
+    if (manifest)
+        desc = CFStringCreateWithFormat(kCFAllocatorDefault, NULL, CFSTR("%@ %@ (%@) [%lu]"), label, peerID, vnsDesc, SOSManifestGetCount(manifest));
+    else
+        desc = CFStringCreateWithFormat(kCFAllocatorDefault, NULL, CFSTR("%@ %@ (%@)"), label, peerID, vnsDesc);
+    CFReleaseSafe(vnsDesc);
+    return desc;
+}
+
+static void CFArrayAppendConfirmedDigestsEntry(CFMutableArrayRef array, CFStringRef label, CFStringRef peerID, CFSetRef vns, SOSManifestRef manifest) {
+    CFStringRef desc = CFStringCreateWithLabelAndViewNameSetDescription(label, peerID, vns, manifest);
+    CFArrayAppendValue(array, desc);
+    CFReleaseSafe(desc);
+    CFDataRef digest = SOSManifestGetDigest(manifest, NULL);
+    if (digest) {
+        CFArrayAppendValue(array, digest);
+    } else {
+        CFDataRef nullDigest = CFDataCreate(kCFAllocatorDefault, NULL, 0);
+        CFArrayAppendValue(array, nullDigest);
+        CFReleaseSafe(nullDigest);
+    }
+}
+
+static CFArrayRef SOSEngineCopyPeerConfirmedDigests_locked(SOSEngineRef engine, CFErrorRef *error) {
+    CFMutableArrayRef result = CFArrayCreateMutableForCFTypes(kCFAllocatorDefault);
+    CFDictionaryForEach(engine->viewNameSet2ChangeTracker, ^(const void *vns, const void *ct) {
+        SOSManifestRef manifest = SOSEngineCopyManifestWithViewNameSet_locked(engine, vns, error);
+        CFArrayAppendConfirmedDigestsEntry(result, CFSTR("local "), engine->myID, (CFSetRef)vns, manifest);
+        CFReleaseSafe(manifest);
+    });
+
+    // Copy other peers even if we aren't in the circle, since we're observing it.
+    SOSEngineForEachPeer_locked(engine, ^(SOSPeerRef peer) {
+        CFArrayAppendConfirmedDigestsEntry(result, CFSTR("remote"), SOSPeerGetID(peer), SOSPeerGetViewNameSet(peer),
+                                           SOSPeerGetConfirmedManifest(peer));
+    });
+    return result;
+}
+
+CFArrayRef SOSEngineCopyPeerConfirmedDigests(SOSEngineRef engine, CFErrorRef *error) {
+    __block CFArrayRef result = NULL;
+    SOSEngineDoOnQueue(engine, ^{
+        result = SOSEngineCopyPeerConfirmedDigests_locked(engine, error);
+    });
+    return result;
+}
+
+SOSDataSourceRef SOSEngineGetDataSource(SOSEngineRef engine) {
+    return engine->dataSource;
+}