keychain/SecureObjectSync/SOSMessage.c

   1 /*
   2  * Copyright (c) 2013-2014 Apple Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25 /*
  26  * SOSMessage.c -  Creation and decoding of SOSMessage objects.
  27  */
  28
  29 #include "keychain/SecureObjectSync/SOSMessage.h"
  30
  31 #include <AssertMacros.h>
  32 #include <CoreFoundation/CoreFoundation.h>
  33 #include "keychain/SecureObjectSync/SOSDigestVector.h"
  34 #include "keychain/SecureObjectSync/SOSManifest.h"
  35 #include "keychain/SecureObjectSync/SOSInternal.h"
  36 #include <corecrypto/ccder.h>
  37 #include <stdlib.h>
  38 #include <stdbool.h>
  39 #include <utilities/SecCFError.h>
  40 #include <utilities/SecCFRelease.h>
  41 #include <utilities/SecCFWrappers.h>
  42 #include <utilities/array_size.h>
  43 #include <utilities/der_date.h>
  44 #include <utilities/der_plist.h>
  45 #include <utilities/der_plist_internal.h>
  46 #include <utilities/debugging.h>
  47 #include <utilities/iCloudKeychainTrace.h>
  48
  49 // TODO: This is a layer violation, we need a better way to do this
  50 // Currently it's only used for logging.
  51 #include "keychain/securityd/SecItemDataSource.h"
  52
  53 #if defined(SOSMessageFormatSpecification) && 0
  54
  55 -- Secure Object Syncing Peer to Peer Message format ASN.1 definition
  56 -- Everything MUST be DER encoded unless otherwise noted.  These exceptions
  57 -- Allow us to stream messages on a streamy network, without loading more
  58 -- than one object into memory at once.
  59
  60 SOSMessage := SEQUENCE {
  61     CHOICE {
  62         v0          V0-MESSAGE-BODY-CLASS
  63         v2          SOSV2MessageBody
  64     }
  65 }
  66
  67 -- v0 Message
  68
  69 V0-MESSAGE-BODY-CLASS ::= CLASS
  70     {
  71      &messageType    INTEGER (manifestDigest, manifest, manifestDeltaAndObjects)
  72      &version        INTEGER OPTIONAL default v0
  73      &Type
  74     }
  75     WITH SYNTAX {&Type IDENTIFIED BY &messageType}
  76
  77 ManifestDigest ::= OCTECT STRING (length 20)
  78
  79 Manifest ::= OCTECT STRING -- (length 20 * number of entries)
  80
  81 manifestDigestBody ::=
  82     { ManifestDigest IDENTIFIED BY {manifestDigest}}
  83
  84 manifestBody ::=
  85     { Manifest IDENTIFIED BY {manifest}}
  86
  87  manifestDeltaAndObjectsBody ::=
  88     { ManifestDeltaAndObjects IDENTIFIED BY {manifestDeltaAndObjects}}
  89
  90 SOSV1MessageBody ::= MESSAGE-BODY-CLASS
  91
  92 ManifestDeltaAndObjects ::= SEQUENCE {
  93      manfestDigest ManifestDigest
  94      removals Manifest
  95      additions Manifest
  96      addedObjects SEQUENCE OF SOSObject
  97 }
  98
  99 -- v2 Message
 100
 101 SOSMessageBody := {
 102     -- top level SEQUENCE may be Constructed, indefinite-length BER encoded
 103     header         SOSMessageHeader,
 104     deltas         [0] IMPLICIT SOSManifestDeltas OPTIONAL,
 105     extensions     [1] IMPLICIT SOSExtensions OPTIONAL,
 106     objects        [2] IMPLICIT SEQUENCE OF SOSObject OPTIONAL
 107         -- [2] IMPLICIT SEQUENCE OF SOSObject may be Constructed,
 108         -- indefinite-length BER encoded -- }
 109
 110 SOSMessageHeader ::= SEQUENCE {
 111     version         [0] IMPLICIT SOSMessageVersion DEFAULT v2,
 112     creationTime    GeneralizedTime OPTIONAL,
 113         -- When this message was created by the sender for tracking latency
 114     sequenceNumber  SOSSequenceNumber OPTIONAL,
 115         -- Message Sequence Number for tracking packet loss in transport
 116     digestTypes     SOSDigestTypes OPTIONAL,
 117         -- Determines the size and format of each SOSManifestDigest and the
 118         -- elements of each SOSManifest.
 119         -- We send the intersection our desired SOSDigestTypes and our peers
 120         -- last received SOSDigestType. If we never received a message from our
 121         -- peer we send our entire desired set and set the digestTypesProposed
 122         -- messageFlag.
 123         -- If the intersection is the empty set we fallback to sha1
 124         -- Each digest and manifest entry is constructed by appending the
 125         -- agreed upon digests in the order they are listed in the DER encoded
 126         -- digestTypes.
 127     messageFlags    BIT STRING {
 128         getObjects                          (0),
 129         joinRequest                         (1),
 130         partial                             (2),
 131         digestTypesProposed                 (3),
 132             -- This is a partial update and might not contain accurate manifest deltas (check this against spec --mb), only objects
 133         clearGetObjects                     (4), -- WIP mb ignore
 134             -- Stop sending me objects for this delta update, I will send you mine instead if you give me a full manifest delta
 135         didClearGetObjectsSinceLastDelta    (5)  -- WIP mb ignore
 136             -- clearGetObjects was set during this delta update, do not
 137             -- set it again (STICKY until either peer clears delta) -- }
 138         skipHello                           (6)  -- Respond with at least a manifest
 139     senderDigest    SOSManifestDigest,
 140         -- The senders manifest digest at the time of sending this message.
 141     baseDigest      [0] IMPLICIT SOSManifestDigest,
 142         -- What this message is based on, if it contains deltas.  If missing we assume the empty set
 143     proposedDigest  [1] IMPLICIT SOSManifestDigest,
 144         -- What the receiver should have after patching baseDigest with
 145         -- additions and removals -- }
 146
 147 SOSMessageVersion ::= INTEGER { v0(0), v2(2), v3(3) }
 148
 149 SOSSequenceNumber ::= INTEGER
 150
 151 -- Note this is not implemented in v2 it only supports sha1
 152 SOSDigestTypes ::= SEQUENCE {
 153     messageFlags    BIT STRING {
 154         sha1(0) -- implied if SOSDigestTypes is not present
 155             sha224(1)
 156             sha256(2)
 157             sha384(3)
 158             sha512(4)
 159             digestAlgorithms SET OF AlgorithmIdentifier
 160             -- Same as AlgorithmIdentifier from X.509 -- } }
 161
 162 SOSManifestDeltas ::= SEQUENCE {
 163     removals    SOSManifest
 164     additions   SOSManifest }
 165
 166 SOSExtensions ::= SEQUENCE SIZE (1..MAX) OF SOSExtension
 167
 168 SOSExtension ::= SEQUENCE {
 169     extnID      OBJECT IDENTIFIER,
 170     critical    BOOLEAN DEFAULT FALSE,
 171     extnValue   OCTET STRING }
 172
 173 SOSManifest ::= OCTET STRING
 174     -- DER encoding is sorted and ready to merge.
 175     -- All SOSDigest entries in a SOSManifest /must/ be the same size
 176     -- As the negotiated SOSManifestEntry.  Se comment in SOSMessageBody
 177     -- on digestTypes
 178
 179 SOSManifestDigest  ::= OCTET STRING
 180
 181 SOSObject ::= SEQUENCE {
 182     [0] conflict OCTECT STRING OPTIONAL
 183     [1] change OCTECT STRING OPTIONAL
 184     object SecDictionary }
 185
 186 SecDictionary ::= SET of SecKVPair
 187
 188 SecKVPair ::= SEQUENCE {
 189     key UTF8String
 190     value Value }
 191
 192 SecValue ::= CHOICE {
 193     bool Boolean
 194     number INTEGER
 195     string UTF8String
 196     data OCTECT STRING
 197     date GENERAL TIME
 198     dictionary Object
 199     array Array }
 200
 201 SecArray ::= SEQUENCE of SecValue
 202
 203 -- For reference:
 204 AlgorithmIdentifier ::= SEQUENCE {
 205 algorithm        OBJECT IDENTIFIER,
 206 parameters       ANY DEFINED BY algorithm OPTIONAL }
 207 -- contains a value of the type
 208 -- registered for use with the
 209 -- algorithm object identifier value
 210
 211 #endif // defined(SOSMessageFormatSpecification) && 0
 212
 213
 214 //
 215 // MARK: SOSMessage implementation.
 216 //
 217
 218 // Legacy v1 message type numbers
 219 enum SOSMessageType {
 220     SOSManifestInvalidMessageType = 0,
 221     SOSManifestDigestMessageType = 1,
 222     SOSManifestMessageType = 2,
 223     SOSManifestDeltaAndObjectsMessageType = 3,
 224 };
 225
 226 struct __OpaqueSOSMessage {
 227     CFRuntimeBase _base;
 228
 229     CFDataRef der;
 230     const uint8_t *objectsDer;
 231     size_t objectsLen;
 232
 233     CFDataRef senderDigest;
 234     CFDataRef baseDigest;
 235     CFDataRef proposedDigest;
 236     SOSManifestRef removals;
 237     SOSManifestRef additions;
 238
 239     CFMutableArrayRef objects;
 240
 241     SOSMessageFlags flags;
 242     uint64_t sequenceNumber;
 243     CFAbsoluteTime creationTime;
 244     uint64_t version;               // Message version (currently always 2)
 245     bool indefiniteLength;          // If set to true the top SEQUENCE and the OBJECTS SEQUENCE are written indefinite length.
 246 };
 247
 248 CFGiblisWithCompareFor(SOSMessage)
 249
 250 static Boolean SOSMessageCompare(CFTypeRef cf1, CFTypeRef cf2) {
 251     SOSMessageRef M = (SOSMessageRef)cf1;
 252     SOSMessageRef P = (SOSMessageRef)cf2;
 253     if (M->flags != P->flags) return false;
 254     if (M->sequenceNumber != P->sequenceNumber) return false;
 255     if (M->creationTime != P->creationTime) return false;
 256     //if (!CFEqualSafe(M->der, P->der)) return false;
 257     if (!CFEqualSafe(M->senderDigest, P->senderDigest)) return false;
 258     if (!CFEqualSafe(M->baseDigest, P->baseDigest)) return false;
 259     if (!CFEqualSafe(M->proposedDigest, P->proposedDigest)) return false;
 260     if (!CFEqualSafe(M->removals, P->removals)) return false;
 261     if (!CFEqualSafe(M->additions, P->additions)) return false;
 262
 263     // TODO Compare Objects if present.
 264
 265     return true;
 266 }
 267
 268 static void SOSMessageDestroy(CFTypeRef cf) {
 269     SOSMessageRef message = (SOSMessageRef)cf;
 270     CFReleaseNull(message->der);
 271     CFReleaseNull(message->senderDigest);
 272     CFReleaseNull(message->baseDigest);
 273     CFReleaseNull(message->proposedDigest);
 274     CFReleaseNull(message->additions);
 275     CFReleaseNull(message->removals);
 276     CFReleaseNull(message->objects);
 277 }
 278
 279 // TODO: Remove this layer violation!
 280 #include "keychain/securityd/SecItemServer.h"
 281
 282 static uint64_t SOSMessageInferType(SOSMessageRef message, CFErrorRef *error);
 283
 284 static CFStringRef SOSMessageCopyFormatDescription(CFTypeRef cf, CFDictionaryRef formatOptions) {
 285     SOSMessageRef message = (SOSMessageRef)cf;
 286     static const uint8_t zero[4] = {};
 287     const uint8_t *S = message->senderDigest ? CFDataGetBytePtr(message->senderDigest) : zero;
 288     const uint8_t *B = message->baseDigest ? CFDataGetBytePtr(message->baseDigest) : zero;
 289     const uint8_t *P = message->proposedDigest ? CFDataGetBytePtr(message->proposedDigest) : zero;
 290     CFDateRef creationDate = CFDateCreate(CFGetAllocator(message), message->creationTime);
 291
 292     CFMutableStringRef objects = CFStringCreateMutable(kCFAllocatorDefault, 0);
 293
 294     // TODO: Remove this layer violation!
 295     SOSDataSourceFactoryRef dsf = SecItemDataSourceFactoryGetDefault();
 296     SOSDataSourceRef ds = SOSDataSourceFactoryCreateDataSource(dsf, kSecAttrAccessibleWhenUnlocked, NULL);
 297
 298     if (ds) {
 299         __block size_t maxEntries = 16;
 300         CFStringAppendFormat(objects, NULL, CFSTR("{[%zu]"), SOSMessageCountObjects(message));
 301         SOSMessageWithSOSObjects(message, ds, NULL, ^(SOSObjectRef object, bool *stop) {
 302             CFDataRef digest = SOSObjectCopyDigest(ds, object, NULL);
 303             const uint8_t *O = CFDataGetBytePtr(digest);
 304             CFStringAppendFormat(objects, NULL, CFSTR(" %02X%02X%02X%02X"), O[0],O[1],O[2],O[3]);
 305             CFReleaseSafe(digest);
 306             if (!--maxEntries) {
 307                 CFStringAppend(objects, CFSTR("..."));
 308                 *stop = true;
 309             }
 310         });
 311         CFStringAppend(objects, CFSTR("}"));
 312     } else {
 313         CFStringAppend(objects, CFSTR("{NO DATASOURCE}"));
 314     }
 315
 316     CFStringRef desc = NULL;
 317     if (message->version == 0) {
 318         switch (SOSMessageInferType(message, NULL)) {
 319             case SOSManifestInvalidMessageType:
 320                 desc = CFStringCreateWithFormat(CFGetAllocator(message), NULL, CFSTR("<MSGInvalid %"PRIu64" >"), message->sequenceNumber);
 321                 break;
 322             case SOSManifestDigestMessageType:
 323                 desc = CFStringCreateWithFormat(CFGetAllocator(message), NULL, CFSTR("<MSGDigest %"PRIu64" %02X%02X%02X%02X>"), message->sequenceNumber, S[0],S[1],S[2],S[3]);
 324                 break;
 325             case SOSManifestMessageType:
 326                 desc = CFStringCreateWithFormat(CFGetAllocator(message), NULL, CFSTR("<MSGManifest %"PRIu64" %@>"), message->sequenceNumber, message->additions);
 327                 break;
 328             case SOSManifestDeltaAndObjectsMessageType:
 329                 desc = CFStringCreateWithFormat(CFGetAllocator(message), NULL, CFSTR("<MSGObjects %"PRIu64" %02X%02X%02X%02X %@ %@ %@"),
 330                                                 message->sequenceNumber,
 331                                                 B[0],B[1],B[2],B[3],
 332                                                 message->removals, message->additions,
 333                                                 objects);
 334                 break;
 335         }
 336     } else {
 337         desc = CFStringCreateWithFormat
 338         (CFGetAllocator(message), NULL, CFSTR("<MSG %"PRIu64" %@ %02X%02X%02X%02X %02X%02X%02X%02X %02X%02X%02X%02X %@ %@ %@ %s%s%s%s%s%s%s>"),
 339         message->sequenceNumber,
 340         creationDate,
 341         S[0],S[1],S[2],S[3],
 342         B[0],B[1],B[2],B[3],
 343         P[0],P[1],P[2],P[3],
 344         message->removals, message->additions,
 345         objects,
 346         (message->flags & kSOSMessageGetObjects) ? "G" : "g",
 347         (message->flags & kSOSMessageJoinRequest) ? "J" : "j",
 348         (message->flags & kSOSMessagePartial) ? "P" : "p",
 349         (message->flags & kSOSMessageDigestTypesProposed) ? "D" : "d",
 350         (message->flags & kSOSMessageClearGetObjects) ? "K" : "k",
 351         (message->flags & kSOSMessageDidClearGetObjectsSinceLastDelta) ? "Z" : "z",
 352         (message->flags & kSOSMessageSkipHello) ? "H" : "h");
 353     }
 354     CFReleaseSafe(creationDate);
 355     CFReleaseSafe(objects);
 356     return desc;
 357 }
 358
 359 //
 360 // MARK: SOSMessage encoding
 361 //
 362
 363 // Create an SOSMessage ready to be encoded.
 364 SOSMessageRef SOSMessageCreate(CFAllocatorRef allocator, uint64_t version, CFErrorRef *error) {
 365     SOSMessageRef message = CFTypeAllocate(SOSMessage, struct __OpaqueSOSMessage, allocator);
 366     message->version = version;
 367     return message;
 368 }
 369
 370 // TODO: Remove me this is for testing only, tests should use the real thing.
 371 SOSMessageRef SOSMessageCreateWithManifests(CFAllocatorRef allocator, SOSManifestRef sender,
 372                                             SOSManifestRef base, SOSManifestRef proposed,
 373                                             bool includeManifestDeltas, CFErrorRef *error) {
 374     SOSMessageRef message = SOSMessageCreate(allocator, kEngineMessageProtocolVersion, error);
 375     if (!SOSMessageSetManifests(message, sender, base, proposed, includeManifestDeltas, NULL, error))
 376         CFReleaseNull(message);
 377     return message;
 378 }
 379
 380 bool SOSMessageSetManifests(SOSMessageRef message, SOSManifestRef sender,
 381                             SOSManifestRef base, SOSManifestRef proposed,
 382                             bool includeManifestDeltas, SOSManifestRef objectsSent,
 383                             CFErrorRef *error) {
 384     if (!message) return true;
 385     bool ok = true;
 386     // TODO: Check at v2 encoding time
 387     // if (!sender) return (SOSMessageRef)SOSErrorCreate(kSOSErrorProcessingFailure, error, NULL, CFSTR("no sender manifest specified for SOSMessage"));
 388     message->baseDigest = CFRetainSafe(SOSManifestGetDigest(base, NULL));
 389     secinfo("engine", "SOSMessageSetManifests: setting base digest to %@ %zu", message->baseDigest, SOSManifestGetCount(base));
 390     message->proposedDigest = CFRetainSafe(SOSManifestGetDigest(proposed, NULL));
 391     secinfo("engine", "SOSMessageSetManifests: setting proposed digest to %@ %zu", message->proposedDigest, SOSManifestGetCount(proposed));
 392     message->senderDigest = CFRetainSafe(SOSManifestGetDigest(sender, NULL));
 393     secinfo("engine", "SOSMessageSetManifests: setting sender digest to %@ %zu", message->senderDigest, SOSManifestGetCount(sender));
 394
 395     if (includeManifestDeltas) {
 396         SOSManifestRef additions = NULL;
 397         ok = SOSManifestDiff(base, proposed, &message->removals, &additions, error);
 398         if (message->version == 0) {
 399             message->additions = additions;
 400         } else {
 401             message->additions = SOSManifestCreateComplement(objectsSent, additions, error);
 402             CFReleaseSafe(additions);
 403         }
 404     }
 405     return ok;
 406 }
 407
 408 void SOSMessageSetFlags(SOSMessageRef message, SOSMessageFlags flags) {
 409     message->flags = flags;
 410 }
 411
 412 // Add an extension to this message
 413 void SOSMessageAddExtension(SOSMessageRef message, CFDataRef oid, bool isCritical, CFDataRef extension) {
 414     // TODO: Implement
 415     secerror("not implemented yet!");
 416 }
 417
 418 static bool SecMessageIsObjectValid(CFDataRef object, CFErrorRef *error) {
 419     const uint8_t *der = CFDataGetBytePtr(object);
 420     const uint8_t *der_end = der + CFDataGetLength(object);
 421     ccder_tag tag = 0;
 422     size_t len = 0;
 423     der = ccder_decode_tag(&tag, der, der_end);
 424     if (!der )
 425         return SOSErrorCreate(kSOSErrorBadFormat, error, NULL, CFSTR("Invalid DER, no tag found"));
 426     if (tag == CCDER_EOL)
 427         return SOSErrorCreate(kSOSErrorBadFormat, error, NULL, CFSTR("Object has EOL tag"));
 428     der = ccder_decode_len(&len, der, der_end);
 429     if (!der)
 430         return SOSErrorCreate(kSOSErrorBadFormat, error, NULL, CFSTR("Object with tag %lu has no valid DER length"), tag);
 431     der += len;
 432      if (der_end - der)
 433         return SOSErrorCreate(kSOSErrorBadFormat, error, NULL, CFSTR("Object has %td trailing unused bytes"), der_end - der);
 434     return true;
 435 }
 436
 437 bool SOSMessageAppendObject(SOSMessageRef message, CFDataRef object, CFErrorRef *error) {
 438     if (!SecMessageIsObjectValid(object, error)) return false;
 439     if (!message->objects)
 440         message->objects = CFArrayCreateMutableForCFTypes(CFGetAllocator(message));
 441     if (message->objects)
 442         CFArrayAppendValue(message->objects, object);
 443     return true;
 444 }
 445
 446 static CC_NONNULL_ALL
 447 size_t ccder_sizeof_bit_string(cc_size n, const cc_unit *s) {
 448     return ccder_sizeof(CCDER_BIT_STRING, ccn_sizeof(ccn_bitlen(n, s)) + 1);
 449 }
 450
 451 static CC_NONNULL_ALL
 452 uint8_t *ccder_encode_bit_string(cc_size n, const cc_unit *s, const uint8_t *der, uint8_t *der_end) {
 453     size_t bits = ccn_bitlen(n, s);
 454     size_t out_size = ccn_sizeof(bits) + 1;
 455     der_end = ccder_encode_body_nocopy(out_size, der, der_end);
 456     if (der_end)
 457         ccn_write_uint_padded(n, s, out_size, der_end);
 458     return ccder_encode_tl(CCDER_BIT_STRING, out_size, der, der_end);
 459 }
 460
 461
 462 static
 463 size_t der_sizeof_implicit_data(ccder_tag tag, CFDataRef data) {
 464     if (!data)
 465         return 0;
 466     return ccder_sizeof_implicit_raw_octet_string(tag, CFDataGetLength(data));
 467 }
 468
 469
 470 static CC_NONNULL((3, 4))
 471 uint8_t *der_encode_implicit_data(ccder_tag tag, CFDataRef data, const uint8_t *der, uint8_t *der_end) {
 472     if (!data)
 473         return der_end;
 474     return ccder_encode_implicit_raw_octet_string(tag, CFDataGetLength(data), CFDataGetBytePtr(data), der, der_end);
 475 }
 476
 477 static size_t der_sizeof_message_header(SOSMessageRef message, CFErrorRef *error) {
 478     if (!message->senderDigest) {
 479         // TODO: Create Error.
 480         return 0;
 481     }
 482     cc_unit flags[1];
 483     flags[0] = (cc_unit)message->flags; // TODO Fix cast or something
 484
 485     return ccder_sizeof(CCDER_CONSTRUCTED_SEQUENCE,
 486         der_sizeof_generalizedtime(message->creationTime, error) +
 487         ccder_sizeof_uint64(message->sequenceNumber) +
 488         ccder_sizeof_bit_string(array_size(flags), flags) +
 489         der_sizeof_implicit_data(CCDER_OCTET_STRING, message->senderDigest) +
 490         der_sizeof_implicit_data(0 | CCDER_CONTEXT_SPECIFIC, message->baseDigest) +
 491         der_sizeof_implicit_data(1 | CCDER_CONTEXT_SPECIFIC, message->proposedDigest));
 492 }
 493
 494 static uint8_t *der_encode_message_header(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, uint8_t *der_end) {
 495     if (!message->senderDigest) {
 496         // TODO: Create Error.
 497         return NULL;
 498     }
 499     cc_unit flags[1];
 500     flags[0] = (cc_unit)message->flags; // TODO Fix cast or something
 501     return ccder_encode_constructed_tl(CCDER_CONSTRUCTED_SEQUENCE, der_end, der,
 502         der_encode_generalizedtime(message->creationTime, error, der,
 503         ccder_encode_uint64(message->sequenceNumber, der,
 504         ccder_encode_bit_string(array_size(flags), flags, der,
 505         der_encode_implicit_data(CCDER_OCTET_STRING, message->senderDigest, der,
 506         der_encode_implicit_data(0 | CCDER_CONTEXT_SPECIFIC, message->baseDigest, der,
 507         der_encode_implicit_data(1 | CCDER_CONTEXT_SPECIFIC, message->proposedDigest, der, der_end)))))));
 508 }
 509
 510 static size_t der_sizeof_deltas(SOSMessageRef message) {
 511     if (!message->additions && !message->removals) return 0;
 512     if (message->version == 0) {
 513         return ccder_sizeof(CCDER_OCTET_STRING, SOSManifestGetSize(message->removals))+
 514                ccder_sizeof(CCDER_OCTET_STRING, SOSManifestGetSize(message->additions));
 515     } else {
 516         return ccder_sizeof(0 | CCDER_CONTEXT_SPECIFIC | CCDER_CONSTRUCTED,
 517                             ccder_sizeof(CCDER_OCTET_STRING, SOSManifestGetSize(message->removals))+
 518                             ccder_sizeof(CCDER_OCTET_STRING, SOSManifestGetSize(message->additions)));
 519     }
 520 }
 521
 522 static uint8_t *der_encode_deltas(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, uint8_t *der_end) {
 523     if (!message->additions && !message->removals) return der_end;
 524     if (message->version == 0) {
 525         return der_encode_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->removals), der,
 526             der_encode_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->additions), der, der_end));
 527     } else {
 528         return ccder_encode_constructed_tl(0 | CCDER_CONTEXT_SPECIFIC | CCDER_CONSTRUCTED, der_end, der,
 529             der_encode_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->removals), der,
 530             der_encode_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->additions), der, der_end)));
 531     }
 532 }
 533
 534 static size_t der_sizeof_extensions(SOSMessageRef message) {
 535     // We don't support any yet.
 536     return 0;
 537 }
 538
 539 static uint8_t *der_encode_extensions(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, uint8_t *der_end) {
 540     // We don't support any yet.
 541     return der_end;
 542 }
 543
 544 static size_t der_sizeof_objects(SOSMessageRef message) {
 545     size_t len = 0;
 546     if (message->objects) {
 547         CFDataRef data;
 548         CFArrayForEachC(message->objects, data) {
 549             len += (size_t)CFDataGetLength(data);
 550         }
 551     } else if (message->version != 0)
 552         return 0;
 553
 554     if (message->indefiniteLength)
 555         return len + 4;
 556     else
 557         return ccder_sizeof(2 | CCDER_CONTEXT_SPECIFIC | CCDER_CONSTRUCTED, len);
 558 }
 559
 560 static uint8_t *der_encode_objects(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, uint8_t *der_end) {
 561     if (!message->objects && message->version != 0) return der_end;
 562     const uint8_t *original_der_end = der_end;
 563     if (message->indefiniteLength)
 564         der_end = ccder_encode_tl(CCDER_EOL, 0, der, der_end);
 565
 566     for (CFIndex position = (message->objects ? CFArrayGetCount(message->objects) : 0) - 1; position >= 0; --position) {
 567         CFDataRef object = CFArrayGetValueAtIndex(message->objects, position);
 568         der_end = ccder_encode_body(CFDataGetLength(object), CFDataGetBytePtr(object), der, der_end);
 569     }
 570     if (message->indefiniteLength) {
 571         return ccder_encode_tag(2 | CCDER_CONTEXT_SPECIFIC | CCDER_CONSTRUCTED, der,
 572                ccder_encode_len(0, der, der_end));
 573     } else {
 574         ccder_tag otag = message->version == 0 ? CCDER_CONSTRUCTED_SEQUENCE : 2 | CCDER_CONTEXT_SPECIFIC | CCDER_CONSTRUCTED;
 575         return ccder_encode_constructed_tl(otag, original_der_end, der, der_end);
 576     }
 577 }
 578
 579 static size_t der_sizeof_v2_message(SOSMessageRef message, CFErrorRef *error) {
 580     size_t body_size = (der_sizeof_message_header(message, error) +
 581                         der_sizeof_deltas(message) +
 582                         der_sizeof_extensions(message) +
 583                         der_sizeof_objects(message));
 584     if (message->indefiniteLength)
 585         return body_size + 4;
 586     else
 587         return ccder_sizeof(CCDER_CONSTRUCTED_SEQUENCE, body_size);
 588 }
 589
 590
 591 static uint8_t *der_encode_v2_message(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, uint8_t *der_end) {
 592     const uint8_t *original_der_end = der_end;
 593     if (message->indefiniteLength)
 594         der_end = ccder_encode_tl(CCDER_EOL, 0, der, der_end);
 595
 596     der_end = der_encode_message_header(message, error, der,
 597         der_encode_deltas(message, error, der,
 598         der_encode_extensions(message, error, der,
 599         der_encode_objects(message, error, der, der_end))));
 600
 601     if (message->indefiniteLength) {
 602         return ccder_encode_tag(CCDER_CONSTRUCTED_SEQUENCE, der,
 603                ccder_encode_len(0, der, der_end));
 604     } else {
 605         return ccder_encode_constructed_tl(CCDER_CONSTRUCTED_SEQUENCE, original_der_end, der, der_end);
 606     }
 607 }
 608
 609 //------------------------------------------------------------------------------------------------------------------------------------
 610 //      V1 support
 611 //------------------------------------------------------------------------------------------------------------------------------------
 612
 613 /* ManifestDigest message */
 614 static size_t der_sizeof_manifest_digest_message(SOSMessageRef message, CFErrorRef *error) {
 615     if (!message->senderDigest || CFDataGetLength(message->senderDigest) != SOSDigestSize) {
 616         SOSErrorCreate(kSOSErrorProcessingFailure, error, NULL, CFSTR("digest length mismatch"));
 617         return 0;
 618     }
 619     return ccder_sizeof(CCDER_CONSTRUCTED_SEQUENCE,
 620                         (ccder_sizeof_uint64(SOSManifestDigestMessageType) +
 621                          ccder_sizeof_raw_octet_string(SOSDigestSize)));
 622 }
 623
 624 static uint8_t *der_encode_manifest_digest_message(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, uint8_t *der_end) {
 625     secinfo("engine", "der_encode_manifest_digest_message: encoded sender digest as %@", message->senderDigest);
 626     return ccder_encode_constructed_tl(CCDER_CONSTRUCTED_SEQUENCE, der_end, der,
 627            ccder_encode_uint64(SOSManifestDigestMessageType, der,
 628            ccder_encode_raw_octet_string(SOSDigestSize, CFDataGetBytePtr(message->senderDigest), der, der_end)));
 629 }
 630
 631 /* Manifest message */
 632 static size_t der_sizeof_manifest_message(SOSMessageRef message, CFErrorRef *error) {
 633     if (!message->additions) {
 634         SOSErrorCreate(kSOSErrorProcessingFailure, error, NULL, CFSTR("no manifest for manifest message"));
 635         return 0;
 636     }
 637     return ccder_sizeof(CCDER_CONSTRUCTED_SEQUENCE,
 638         (ccder_sizeof_uint64(SOSManifestMessageType) +
 639          der_sizeof_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->additions))));
 640 }
 641
 642 static uint8_t *der_encode_manifest_message(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, uint8_t *der_end) {
 643     secinfo("engine", "der_encode_manifest_message: encoded message additions as (%zu, %@)", SOSManifestGetCount(message->additions), SOSManifestGetDigest(message->additions, NULL));
 644     return ccder_encode_constructed_tl(CCDER_CONSTRUCTED_SEQUENCE, der_end, der,
 645                ccder_encode_uint64(SOSManifestMessageType, der,
 646                der_encode_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->additions), der, der_end)));
 647 }
 648
 649 /* ManifestDeltaAndObjects message */
 650 static size_t der_sizeof_manifest_and_objects_message(SOSMessageRef message, CFErrorRef *error) {
 651     if (!message->baseDigest || CFDataGetLength(message->baseDigest) != SOSDigestSize) {
 652         SOSErrorCreate(kSOSErrorProcessingFailure, error, NULL, CFSTR("digest length mismatch"));
 653         return 0;
 654     }
 655
 656     return ccder_sizeof(CCDER_CONSTRUCTED_SEQUENCE,
 657         (ccder_sizeof_uint64(SOSManifestDeltaAndObjectsMessageType) +
 658          ccder_sizeof(CCDER_CONSTRUCTED_SEQUENCE,
 659              (ccder_sizeof_raw_octet_string(SOSDigestSize) +
 660               der_sizeof_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->removals)) +
 661               der_sizeof_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->additions)) +
 662               der_sizeof_objects(message)))));
 663 }
 664
 665 static uint8_t *der_encode_manifest_and_objects_message(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, uint8_t *der_end) {
 666     secinfo("engine", "der_encode_manifest_and_objects_message: encoded base digest as %@", message->baseDigest);
 667     return ccder_encode_constructed_tl(CCDER_CONSTRUCTED_SEQUENCE, der_end, der,
 668                ccder_encode_uint64(SOSManifestDeltaAndObjectsMessageType, der,
 669                ccder_encode_constructed_tl(CCDER_CONSTRUCTED_SEQUENCE, der_end, der,
 670                    ccder_encode_raw_octet_string(SOSDigestSize, CFDataGetBytePtr(message->baseDigest), der,
 671                    der_encode_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->removals), der,
 672                    der_encode_implicit_data(CCDER_OCTET_STRING, SOSManifestGetData(message->additions), der,
 673                    der_encode_objects(message, error, der, der_end)))))));
 674 }
 675
 676 static uint64_t SOSMessageInferType(SOSMessageRef message, CFErrorRef *error) {
 677     if (message->baseDigest) {
 678         // TODO: Assert that we don't have senderDigest or proposedDigest
 679         if (SOSManifestGetCount(message->removals) || SOSManifestGetCount(message->additions) || SOSMessageCountObjects(message)) {
 680             return SOSManifestDeltaAndObjectsMessageType;
 681         } else {
 682             // NOTE: If we force a SOSManifestDeltaAndObjectsMessageType instead then
 683             // true v0 peers will overwrite their last objects message to us.  However this
 684             // implements the current v0 behaviour
 685             return SOSManifestDigestMessageType;
 686         }
 687     } else if (message->additions) {
 688         // TODO: Assert that we don't have senderDigest, proposedDigest, additions, removals or objects
 689         return SOSManifestMessageType;
 690     } else if (message->senderDigest) {
 691         // TODO: Assert that we don't have proposedDigest, removals or objects
 692         return SOSManifestDigestMessageType;
 693     }
 694     // TODO: Create error.
 695     return SOSManifestInvalidMessageType;
 696 }
 697
 698 static size_t der_sizeof_message(SOSMessageRef message, uint64_t messageType, CFErrorRef *error) {
 699     switch (messageType) {
 700         case SOSManifestInvalidMessageType:
 701             return der_sizeof_v2_message(message, error);
 702         case SOSManifestDigestMessageType:
 703             return der_sizeof_manifest_digest_message(message, error);
 704         case SOSManifestMessageType:
 705             return der_sizeof_manifest_message(message, error);
 706         case SOSManifestDeltaAndObjectsMessageType:
 707             return der_sizeof_manifest_and_objects_message(message, error);
 708     }
 709     return 0;
 710 }
 711
 712 static uint8_t *der_encode_message(SOSMessageRef message, uint64_t messageType, CFErrorRef *error, const uint8_t *der, uint8_t *der_end) {
 713     switch (messageType) {
 714         case SOSManifestInvalidMessageType:
 715             return der_encode_v2_message(message, error, der, der_end);
 716         case SOSManifestDigestMessageType:
 717             return der_encode_manifest_digest_message(message, error, der, der_end);
 718         case SOSManifestMessageType:
 719             return der_encode_manifest_message(message, error, der, der_end);
 720         case SOSManifestDeltaAndObjectsMessageType:
 721             return der_encode_manifest_and_objects_message(message, error, der, der_end);
 722     }
 723     return der_end;
 724 }
 725
 726 // Encode an SOSMessage, calls addObject callback and appends returned objects
 727 // one by one, until addObject returns NULL.
 728 CFDataRef SOSMessageCreateData(SOSMessageRef message, uint64_t sequenceNumber, CFErrorRef *error) {
 729     // Version 2 message have sequence numbers, version 0 messages do not.
 730     uint64_t messageType = SOSManifestInvalidMessageType;
 731     message->sequenceNumber = sequenceNumber;
 732     if (message->version == 0) {
 733         message->indefiniteLength = false;
 734         messageType = SOSMessageInferType(message, error);
 735         if (!messageType) {
 736             // Propagate error
 737             return NULL;
 738         }
 739     } else {
 740         message->creationTime = floor(CFAbsoluteTimeGetCurrent());
 741     }
 742     size_t der_size = der_sizeof_message(message, messageType, error);
 743     CFMutableDataRef data = CFDataCreateMutable(NULL, der_size);
 744     if (data == NULL) {
 745         // TODO Error.
 746         return NULL;
 747     }
 748     CFDataSetLength(data, der_size);
 749     uint8_t *der_end = CFDataGetMutableBytePtr(data);
 750     const uint8_t *der = der_end;
 751     der_end += der_size;
 752
 753     der_end = der_encode_message(message, messageType, error, der, der_end);
 754     if (der != der_end) {
 755         secwarning("internal error %td bytes unused in der buffer", der_end - der);
 756     }
 757     return data;
 758 }
 759
 760 //
 761 // MARK: SOSMessage decoding
 762 //
 763
 764 #define CCBER_LEN_INDEFINITE ((size_t)-1)
 765
 766 // Decode BER length field.  Sets *lenp to ccber_indefinite_len if this is an indefinite length encoded object.
 767 // Behaves like ccder_decode_len in every other way.
 768 static CC_NONNULL((1, 3))
 769 const uint8_t *ccber_decode_len(size_t *lenp, const uint8_t *der, const uint8_t *der_end) {
 770     if (der && der < der_end) {
 771         if (*der == 0x80) {
 772             der++;
 773             *lenp = CCBER_LEN_INDEFINITE;
 774         }
 775         else
 776             der = ccder_decode_len(lenp, der, der_end);
 777     }
 778     return der;
 779 }
 780
 781 static const uint8_t *der_decode_generalizedtime(CFAbsoluteTime *at, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
 782     const uint8_t *times_end = NULL;
 783     der = ccder_decode_constructed_tl(CCDER_GENERALIZED_TIME, &times_end, der, der_end);
 784     der = der_decode_generalizedtime_body(at, error, der, times_end);
 785     if (times_end != der) {
 786         secwarning("internal error %td bytes unused in generalizedtime DER buffer", times_end - der);
 787     }
 788     return der;
 789 }
 790
 791 static const uint8_t *der_decode_optional_generalizedtime(CFAbsoluteTime *at, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
 792     const uint8_t *times_end = der_decode_generalizedtime(at, error, der, der_end);
 793     return times_end ? times_end : der;
 794 }
 795
 796 static CC_NONNULL((2, 4))
 797 const uint8_t *ccder_decode_implicit_uint64(ccder_tag expected_tag, uint64_t* r, const uint8_t *der, const uint8_t *der_end) {
 798     size_t len;
 799     der = ccder_decode_tl(expected_tag, &len, der, der_end);
 800     if (der && len && (*der & 0x80) != 0x80) {
 801         if (ccn_read_uint(ccn_nof_size(sizeof(*r)), (cc_unit*)r, len, der) >= 0)
 802             return der + len;
 803     }
 804     return NULL;
 805 }
 806
 807 static const uint8_t *ccder_decode_optional_implicit_uint64(ccder_tag expected_tag, uint64_t *value, const uint8_t *der, const uint8_t *der_end) {
 808     const uint8_t *ui64_end = ccder_decode_implicit_uint64(expected_tag, value, der, der_end);
 809     return ui64_end ? ui64_end : der;
 810 }
 811
 812
 813 static const uint8_t *ccder_decode_optional_uint64(uint64_t *value, const uint8_t *der, const uint8_t *der_end) {
 814     const uint8_t *ui64_end = ccder_decode_uint64(value, der, der_end);
 815     return ui64_end ? ui64_end : der;
 816 }
 817
 818 static const uint8_t *ccder_decode_digest_types(SOSMessageRef message, const uint8_t *der, const uint8_t *der_end) {
 819     const uint8_t *dt_end;
 820     der = ccder_decode_sequence_tl(&dt_end, der, der_end);
 821     if (!der) return NULL;
 822     // Skip over digestType body for now.
 823     // TODO: Support DigestType
 824     return dt_end;
 825 }
 826
 827 static const uint8_t *ccder_decode_optional_digest_types(SOSMessageRef message, const uint8_t *der, const uint8_t *der_end) {
 828     const uint8_t *dt_end = ccder_decode_digest_types(message, der, der_end);
 829     return dt_end ? dt_end : der;
 830 }
 831
 832 static const uint8_t *ccder_decode_bit_string(cc_size n, size_t *r_bitlen, cc_unit *r, const uint8_t *der, const uint8_t *der_end) {
 833     size_t len;
 834     const uint8_t *body = ccder_decode_tl(CCDER_BIT_STRING, &len, der, der_end);
 835     if (!body || len < 1)
 836         return NULL;
 837
 838     if (r_bitlen) *r_bitlen = (len - 1) * 8 - (body[0] & 7);
 839     ccn_read_uint(1, r, len - 1, body + 1);
 840     return body + len;
 841 }
 842
 843 static const uint8_t *der_decode_implicit_data(ccder_tag expected_tag, CFDataRef *data, const uint8_t *der, const uint8_t *der_end) {
 844     size_t len = 0;
 845     der = ccder_decode_tl(expected_tag, &len, der, der_end);
 846     if (der && data) {
 847         *data = CFDataCreateWithBytesNoCopy(kCFAllocatorDefault, der, len, kCFAllocatorNull);
 848         if (*data)
 849             der += len;
 850         else
 851             der = NULL;
 852     }
 853     return der;
 854 }
 855
 856 static const uint8_t *der_decode_optional_implicit_data(ccder_tag expected_tag, CFDataRef *data, const uint8_t *der, const uint8_t *der_end) {
 857     const uint8_t *data_end = der_decode_implicit_data(expected_tag, data, der, der_end);
 858     return data_end ? data_end : der;
 859 }
 860
 861 static const uint8_t *der_decode_deltas_body(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
 862     CFDataRef removals = NULL, additions = NULL;
 863     der = der_decode_implicit_data(CCDER_OCTET_STRING, &removals, der, der_end);
 864     der = der_decode_implicit_data(CCDER_OCTET_STRING, &additions, der, der_end);
 865     if (der) {
 866         message->removals = SOSManifestCreateWithData(removals, error);
 867         message->additions = SOSManifestCreateWithData(additions, error);
 868         if (!message->removals || !message->additions) {
 869             CFReleaseNull(message->removals);
 870             CFReleaseNull(message->additions);
 871             der = NULL;
 872         }
 873     }
 874     CFReleaseSafe(removals);
 875     CFReleaseSafe(additions);
 876
 877     return der;
 878 }
 879
 880 static const uint8_t *der_decode_deltas(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
 881     const uint8_t *deltas_end = NULL;
 882     der = ccder_decode_constructed_tl(0 | CCDER_CONTEXT_SPECIFIC | CCDER_CONSTRUCTED, &deltas_end, der, der_end);
 883     return der_decode_deltas_body(message, error, der, deltas_end);
 884 }
 885
 886 static const uint8_t *der_decode_optional_deltas(SOSMessageRef message, const uint8_t *der, const uint8_t *der_end) {
 887     const uint8_t *seq_end = der_decode_deltas(message, NULL, der, der_end);
 888     return seq_end ? seq_end : der;
 889 }
 890
 891 static const uint8_t *der_decode_extensions(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
 892     const uint8_t *extensions_end;
 893     der = ccder_decode_constructed_tl(1 | CCDER_CONTEXT_SPECIFIC | CCDER_CONSTRUCTED, &extensions_end, der, der_end);
 894     if (!der) return NULL;
 895     // Skip over extensions for now.
 896     return extensions_end;
 897 }
 898
 899 static const uint8_t *der_decode_optional_extensions(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
 900     const uint8_t *extensions_end = der_decode_extensions(message, NULL, der, der_end);
 901     return extensions_end ? extensions_end : der;
 902 }
 903
 904 static const uint8_t *der_foreach_objects(size_t length, const uint8_t *der, const uint8_t *der_end, CFErrorRef *error, void(^withObject)(CFDataRef object, bool *stop)) {
 905     bool stop = false;
 906     ccder_tag tag;
 907     // Look ahead at the tag
 908     while (!stop && ccder_decode_tag(&tag, der, der_end) && tag != CCDER_EOL) {
 909         const uint8_t *object_end = NULL;
 910         if (!ccder_decode_constructed_tl(tag, &object_end, der, der_end)) {
 911             SOSErrorCreate(kSOSErrorDecodeFailure, error, NULL, CFSTR("failed to decode object header"));
 912             return NULL;
 913         }
 914         if (withObject) {
 915             CFDataRef object = CFDataCreateWithBytesNoCopy(kCFAllocatorDefault, der, object_end - der, kCFAllocatorNull);
 916             withObject(object, &stop);
 917             CFReleaseSafe(object);
 918         }
 919         der = object_end;
 920     }
 921     if (length == CCBER_LEN_INDEFINITE) {
 922         size_t len = 0;
 923         der = ccder_decode_tl(CCDER_EOL, &len, der, der_end);
 924         if (len != 0) {
 925             secwarning("%td length ", der_end - der);
 926         }
 927     }
 928     if (!stop && der != der_end)
 929         secwarning("%td trailing bytes after objects DER", der_end - der);
 930
 931     return der;
 932 }
 933
 934 static const uint8_t *der_decode_objects(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
 935     ccder_tag tag = 0;
 936     size_t objects_len = 0;
 937     der = ccder_decode_tag(&tag, der, der_end);
 938     if (tag != (2 | CCDER_CONTEXT_SPECIFIC | CCDER_CONSTRUCTED)) return NULL;
 939     der = ccber_decode_len(&objects_len, der, der_end);
 940     if (objects_len != CCBER_LEN_INDEFINITE && der_end - der != (ptrdiff_t)objects_len) {
 941         secwarning("%td trailing bytes after SOSMessage DER", (der_end - der) - (ptrdiff_t)objects_len);
 942     }
 943     // Remember a pointer into message->der where objects starts.
 944     message->objectsDer = der;
 945     message->objectsLen = objects_len;
 946
 947     return der + objects_len;
 948 }
 949
 950 static const uint8_t *der_decode_optional_objects(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
 951     const uint8_t *seq_end = der_decode_objects(message, NULL, der, der_end);
 952     return seq_end ? seq_end : der;
 953 }
 954
 955 static const uint8_t *der_decode_message_header(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
 956     cc_unit flags[1] = {};
 957     der = ccder_decode_constructed_tl(CCDER_CONSTRUCTED_SEQUENCE, &der_end, der, der_end);
 958     message->version = 2;
 959     der = ccder_decode_optional_implicit_uint64(0 | CCDER_CONTEXT_SPECIFIC, &message->version, der, der_end);
 960     der = der_decode_optional_generalizedtime(&message->creationTime, error, der, der_end);
 961     der = ccder_decode_optional_uint64(&message->sequenceNumber, der, der_end);
 962     der = ccder_decode_optional_digest_types(message, der, der_end);
 963     der = ccder_decode_bit_string(array_size(flags), NULL, flags, der, der_end);
 964     message->flags = flags[0];
 965
 966     der = der_decode_implicit_data(CCDER_OCTET_STRING, &message->senderDigest, der, der_end);
 967     secinfo("engine", "der_decode_message_header: decoded sender digest as %@", message->senderDigest);
 968
 969     der = der_decode_optional_implicit_data(0 | CCDER_CONTEXT_SPECIFIC, &message->baseDigest, der, der_end);
 970     secinfo("engine", "der_decode_message_header: decoded base digest as %@", message->baseDigest);
 971
 972     der = der_decode_optional_implicit_data(1 | CCDER_CONTEXT_SPECIFIC, &message->proposedDigest, der, der_end);
 973     secinfo("engine", "der_decode_message_header: decoded proposed digest as %@", message->proposedDigest);
 974
 975     return der;
 976 }
 977
 978 static const uint8_t *
 979 der_decode_manifest_and_objects_message(SOSMessageRef message,
 980                                         CFErrorRef *error, const uint8_t *der,
 981                                         const uint8_t *der_end) {
 982     size_t objects_len = 0;
 983     const uint8_t *body_end;
 984     der = ccder_decode_sequence_tl(&body_end, der, der_end);
 985     if (body_end != der_end) {
 986         SOSErrorCreate(kSOSErrorInvalidMessage, error, NULL, CFSTR("Trailing garbage at end of message"));
 987         return NULL;
 988     }
 989     der = der_decode_implicit_data(CCDER_OCTET_STRING, &message->baseDigest, der, body_end);
 990     secinfo("engine", "der_decode_manifest_and_objects_message: decoded base digest as %@", message->baseDigest);
 991
 992     der = der_decode_deltas_body(message, error, der, body_end);
 993     // Remember a pointer into message->der where objects starts.
 994     der = message->objectsDer = ccder_decode_tl(CCDER_CONSTRUCTED_SEQUENCE, &objects_len, der, body_end);
 995     message->objectsLen = objects_len;
 996
 997     return der ? der + objects_len : NULL;
 998 }
 999
1000 static const uint8_t *der_decode_v0_message_body(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
1001     uint64_t messageType = 0;
1002     der = ccder_decode_uint64(&messageType, der, der_end);
1003     if (der) switch (messageType) {
1004         case SOSManifestDigestMessageType:
1005         {
1006             der = der_decode_implicit_data(CCDER_OCTET_STRING, &message->senderDigest, der, der_end);
1007             secinfo("engine", "der_decode_v0_message_body: received a DigestMessage with sender digest: %@", message->senderDigest);
1008             break;
1009         }
1010         case SOSManifestMessageType:
1011         {
1012             CFDataRef manifestBody = NULL;
1013             der = der_decode_implicit_data(CCDER_OCTET_STRING, &manifestBody, der, der_end);
1014             if (!der) return NULL;
1015             if (der != der_end) {
1016                 secwarning("%td trailing bytes after deltas DER", der_end - der);
1017             }
1018             message->additions = SOSManifestCreateWithData(manifestBody, error);
1019             secinfo("engine", "der_decode_v0_message_body: received a ManifestMessage with (%zu, %@)", SOSManifestGetCount(message->additions), SOSManifestGetDigest(message->additions, NULL));
1020             CFReleaseSafe(manifestBody);
1021             break;
1022         }
1023         case SOSManifestDeltaAndObjectsMessageType:
1024         {
1025             der = der_decode_manifest_and_objects_message(message, error, der, der_end);
1026             break;
1027         }
1028         default:
1029             SOSErrorCreate(kSOSErrorInvalidMessage, error, NULL, CFSTR("Invalid message type %llu"), messageType);
1030             break;
1031     }
1032     return der;
1033 }
1034
1035 static const uint8_t *der_decode_message(SOSMessageRef message, CFErrorRef *error, const uint8_t *der, const uint8_t *der_end) {
1036     ccder_tag tag = 0;
1037     size_t body_len = 0;
1038
1039     der = ccder_decode_tag(&tag, der, der_end);
1040     if (tag != CCDER_CONSTRUCTED_SEQUENCE) return NULL;
1041     der = ccber_decode_len(&body_len, der, der_end);
1042     if (der && body_len && body_len != CCBER_LEN_INDEFINITE && (der_end - der) != (ptrdiff_t)body_len) {
1043         secwarning("%td trailing bytes after SOSMessage DER", (der_end - der) - (ptrdiff_t)body_len);
1044         der_end = der + body_len;
1045     }
1046
1047     if (ccder_decode_tag(&tag, der, der_end)) switch (tag) {
1048         case CCDER_INTEGER: // v0
1049             if (body_len == CCBER_LEN_INDEFINITE)
1050                 der = NULL; // Not supported for v0 messages
1051             else
1052                 der = der_decode_v0_message_body(message, error, der, der_end);
1053             break;
1054         case CCDER_CONSTRUCTED_SEQUENCE: //v2
1055             der = der_decode_message_header(message, error, der, der_end);
1056             der = der_decode_optional_deltas(message, der, der_end);
1057             der = der_decode_optional_extensions(message, error, der, der_end);
1058             der = der_decode_optional_objects(message, error, der, der_end);
1059         break;
1060     }
1061     return der;
1062 }
1063
1064 // Decode a SOSMessage
1065 SOSMessageRef SOSMessageCreateWithData(CFAllocatorRef allocator, CFDataRef derData, CFErrorRef *error) {
1066     if (!derData)
1067         return (SOSMessageRef)SOSErrorCreate(kSOSErrorDecodeFailure, error, NULL, CFSTR("NULL data => no SOSMessage"));
1068     SOSMessageRef message = CFTypeAllocate(SOSMessage, struct __OpaqueSOSMessage, allocator);
1069     if (!message)
1070         return (SOSMessageRef)SOSErrorCreate(kSOSErrorAllocationFailure, error, NULL, CFSTR("failed to alloc SOSMessage"));
1071     message->der = CFRetainSafe(derData);
1072     const uint8_t *der = CFDataGetBytePtr(derData);
1073     const uint8_t *der_end = der + CFDataGetLength(derData);
1074     der = der_decode_message(message, error, der, der_end);
1075     if (!der_end || der != der_end) {
1076         if (error && !*error)
1077             SOSErrorCreate(kSOSErrorDecodeFailure, error, NULL, CFSTR("SOSMessage DER decoding failure %td bytes left"), der_end - der);
1078         return CFReleaseSafe(message);
1079     }
1080     return message;
1081 }
1082
1083 // Read values from a decoded messgage
1084
1085 CFDataRef SOSMessageGetBaseDigest(SOSMessageRef message) {
1086     return message->baseDigest;
1087 }
1088
1089 CFDataRef SOSMessageGetProposedDigest(SOSMessageRef message) {
1090     return message->proposedDigest;
1091 }
1092
1093 CFDataRef SOSMessageGetSenderDigest(SOSMessageRef message) {
1094     return message->senderDigest;
1095 }
1096
1097 SOSMessageFlags SOSMessageGetFlags(SOSMessageRef message) {
1098     return message->flags;
1099 }
1100
1101 uint64_t SOSMessageGetSequenceNumber(SOSMessageRef message) {
1102     return message->sequenceNumber;
1103 }
1104
1105 SOSManifestRef SOSMessageGetRemovals(SOSMessageRef message) {
1106     return message->removals;
1107 }
1108
1109 SOSManifestRef SOSMessageGetAdditions(SOSMessageRef message) {
1110     return message->additions;
1111 }
1112
1113 // Iterate though the extensions in a decoded SOSMessage.  If criticalOnly is
1114 // true all non critical extensions are skipped.
1115 void SOSMessageWithExtensions(SOSMessageRef message, bool criticalOnly, void(^withExtension)(CFDataRef oid, bool isCritical, CFDataRef extension, bool *stop)) {
1116     // TODO
1117 }
1118
1119 size_t SOSMessageCountObjects(SOSMessageRef message) {
1120     if (message->objects)
1121         return CFArrayGetCount(message->objects);
1122     if (!message->objectsDer)
1123         return 0;
1124     const uint8_t *der = CFDataGetBytePtr(message->der);
1125     const uint8_t *der_end = der + CFDataGetLength(message->der);
1126     __block size_t count = 0;
1127     der_foreach_objects(message->objectsLen, message->objectsDer, der_end, NULL, ^(CFDataRef object, bool *stop){ ++count; });
1128     return count;
1129 }
1130
1131 // Iterate though the objects in a decoded SOSMessage.
1132 bool SOSMessageWithObjects(SOSMessageRef message, CFErrorRef *error,
1133                            void(^withObject)(CFDataRef object, bool *stop)) {
1134     if (message->objects) {
1135         CFDataRef object;
1136         CFArrayForEachC(message->objects, object) {
1137             bool stop = false;
1138             withObject(object, &stop);
1139             if (stop)
1140                 break;
1141         }
1142         return true;
1143     }
1144     if (!message->objectsDer)
1145         return true;
1146     const uint8_t *der = CFDataGetBytePtr(message->der);
1147     const uint8_t *der_end = der + CFDataGetLength(message->der);
1148     return der_foreach_objects(message->objectsLen, message->objectsDer, der_end, error, withObject);
1149 }
1150
1151 bool SOSMessageWithSOSObjects(SOSMessageRef message, SOSDataSourceRef dataSource, CFErrorRef *error,
1152                            void(^withObject)(SOSObjectRef object, bool *stop)) {
1153     return SOSMessageWithObjects(message, error, ^(CFDataRef object, bool *stop) {
1154         CFDictionaryRef plist = NULL;
1155         const uint8_t *der = CFDataGetBytePtr(object);
1156         const uint8_t *der_end = der + CFDataGetLength(object);
1157         // TODO Remove intermediate plist format
1158         der = der_decode_dictionary(kCFAllocatorDefault, kCFPropertyListImmutable, &plist, error, der, der_end);
1159         if (der) {
1160             SOSObjectRef peersObject = SOSObjectCreateWithPropertyList(dataSource, plist, error);
1161             withObject(peersObject, stop);
1162             CFReleaseSafe(peersObject);
1163         }
1164         CFReleaseSafe(plist);
1165     });
1166 }