OSX/libsecurity_codesigning/lib/opaquewhitelist.cpp

   1 /*
   2  * Copyright (c) 2014-2016 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 #include "opaquewhitelist.h"
  24 #include "csutilities.h"
  25 #include "StaticCode.h"
  26 #include <CoreFoundation/CoreFoundation.h>
  27 #include <Security/SecCodePriv.h>
  28 #include <Security/SecCodeSigner.h>
  29 #include <Security/SecStaticCode.h>
  30 #include <security_utilities/cfutilities.h>
  31 #include <security_utilities/cfmunge.h>
  32 #include <CoreFoundation/CFBundlePriv.h>
  33 #include <spawn.h>
  34
  35 namespace Security {
  36 namespace CodeSigning {
  37
  38 using namespace SQLite;
  39
  40
  41 static std::string hashString(CFDataRef hash);
  42 static void attachOpaque(SecStaticCodeRef code, SecAssessmentFeedback feedback);
  43
  44
  45 //
  46 // Open the database
  47 //
  48 OpaqueWhitelist::OpaqueWhitelist(const char *path, int flags)
  49         : SQLite::Database(path ? path : opaqueDatabase, flags)
  50 {
  51         SQLite::Statement createConditions(*this,
  52                 "CREATE TABLE IF NOT EXISTS conditions ("
  53                 " label text,"
  54            " weight real not null unique,"
  55            " source text,"
  56            " identifier text,"
  57            " version text,"
  58            " conditions text not null);"
  59         );
  60         createConditions.execute();
  61         mOverrideQueue = dispatch_queue_create("com.apple.security.assessment.whitelist-override", DISPATCH_QUEUE_SERIAL);
  62 }
  63
  64 OpaqueWhitelist::~OpaqueWhitelist()
  65 {
  66         dispatch_release(mOverrideQueue);
  67 }
  68
  69
  70 //
  71 // Check if a code object is whitelisted
  72 //
  73 bool OpaqueWhitelist::contains(SecStaticCodeRef codeRef, SecAssessmentFeedback feedback, OSStatus reason)
  74 {
  75         // make our own copy of the code object, so we can poke at it without disturbing the original
  76         SecPointer<SecStaticCode> code = new SecStaticCode(SecStaticCode::requiredStatic(codeRef)->diskRep());
  77
  78         CFCopyRef<CFDataRef> current = code->cdHash();  // current cdhash
  79         CFDataRef opaque = NULL;        // holds computed opaque cdhash
  80         bool match = false;     // holds final result
  81
  82         if (!current)
  83                 return false;   // unsigned
  84
  85         // collect auxiliary information for trace
  86         CFRef<CFDictionaryRef> info;
  87         std::string team = "";
  88         CFStringRef cfVersion = NULL, cfShortVersion = NULL, cfExecutable = NULL;
  89         if (errSecSuccess == SecCodeCopySigningInformation(code->handle(false), kSecCSSigningInformation, &info.aref())) {
  90                 if (CFStringRef cfTeam = CFStringRef(CFDictionaryGetValue(info, kSecCodeInfoTeamIdentifier)))
  91                         team = cfString(cfTeam);
  92                 if (CFDictionaryRef infoPlist = CFDictionaryRef(CFDictionaryGetValue(info, kSecCodeInfoPList))) {
  93                         if (CFTypeRef version = CFDictionaryGetValue(infoPlist, kCFBundleVersionKey))
  94                                 if (CFGetTypeID(version) == CFStringGetTypeID())
  95                                         cfVersion = CFStringRef(version);
  96                         if (CFTypeRef shortVersion = CFDictionaryGetValue(infoPlist, _kCFBundleShortVersionStringKey))
  97                                 if (CFGetTypeID(shortVersion) == CFStringGetTypeID())
  98                                         cfShortVersion = CFStringRef(shortVersion);
  99                         if (CFTypeRef executable = CFDictionaryGetValue(infoPlist, kCFBundleExecutableKey))
 100                                 if (CFGetTypeID(executable) == CFStringGetTypeID())
 101                                         cfExecutable = CFStringRef(executable);
 102                 }
 103         }
 104
 105         // compute and attach opaque signature
 106         attachOpaque(code->handle(false), feedback);
 107         opaque = code->cdHash();
 108
 109         // lookup current cdhash in whitelist
 110         if (opaque) {
 111                 SQLite::Statement lookup(*this, "SELECT opaque FROM whitelist WHERE current=:current"
 112                         " AND opaque != 'disable override'");
 113                 lookup.bind(":current") = current.get();
 114                 while (lookup.nextRow()) {
 115                         CFRef<CFDataRef> expected = lookup[0].data();
 116                         if (CFEqual(opaque, expected)) {
 117                                 match = true;   // actual opaque cdhash matches expected
 118                                 break;
 119                         }
 120                 }
 121         }
 122
 123         // prepare strings for use inside block
 124         std::string currentHash = hashString(current);
 125         std::string opaqueHash = opaque ? hashString(opaque) : "none";
 126
 127         // send a trace indicating the result
 128         MessageTrace trace("com.apple.security.assessment.whitelist2", code->identifier().c_str());
 129         trace.add("signature2", "%s", currentHash.c_str());
 130         trace.add("signature3", "%s", opaqueHash.c_str());
 131         trace.add("result", match ? "pass" : "fail");
 132         trace.add("reason", "%d", (int)reason);
 133         if (!team.empty())
 134                 trace.add("teamid", "%s", team.c_str());
 135         if (cfVersion)
 136                 trace.add("version", "%s", cfString(cfVersion).c_str());
 137         if (cfShortVersion)
 138                 trace.add("version2", "%s", cfString(cfShortVersion).c_str());
 139         if (cfExecutable)
 140                 trace.add("execname", "%s", cfString(cfExecutable).c_str());
 141         trace.send("");
 142
 143         return match;
 144 }
 145
 146
 147 //
 148 // Obtain special validation conditions for a static code, based on database configuration.
 149 //
 150 CFDictionaryRef OpaqueWhitelist::validationConditionsFor(SecStaticCodeRef code)
 151 {
 152         // figure out which team key to use
 153         std::string team = "UNKNOWN";
 154         CFStringRef cfId = NULL;
 155         CFStringRef cfVersion = NULL;
 156         CFRef<CFDictionaryRef> info;    // holds lifetimes for the above
 157         if (errSecSuccess == SecCodeCopySigningInformation(code, kSecCSSigningInformation, &info.aref())) {
 158                 if (CFStringRef cfTeam = CFStringRef(CFDictionaryGetValue(info, kSecCodeInfoTeamIdentifier)))
 159                         team = cfString(cfTeam);
 160                 cfId = CFStringRef(CFDictionaryGetValue(info, kSecCodeInfoIdentifier));
 161                 if (CFDictionaryRef infoPlist = CFDictionaryRef(CFDictionaryGetValue(info, kSecCodeInfoPList)))
 162                         if (CFTypeRef version = CFDictionaryGetValue(infoPlist, _kCFBundleShortVersionStringKey))
 163                                 if (CFGetTypeID(version) == CFStringGetTypeID())
 164                                         cfVersion = CFStringRef(version);
 165         }
 166         if (cfId == NULL)       // unsigned; punt
 167                 return NULL;
 168
 169         // find the highest weight matching condition. We perform no merging and the heaviest rule wins
 170         SQLite::Statement matches(*this,
 171                 "SELECT conditions FROM conditions"
 172                 " WHERE (source = :source or source IS NULL)"
 173                 " AND (identifier = :identifier or identifier is NULL)"
 174                 " AND ((:version IS NULL AND version IS NULL) OR (version = :version OR version IS NULL))"
 175                 " ORDER BY weight DESC"
 176                 " LIMIT 1"
 177         );
 178         matches.bind(":source") = team;
 179         matches.bind(":identifier") = cfString(cfId);
 180         if (cfVersion)
 181                 matches.bind(":version") = cfString(cfVersion);
 182         if (matches.nextRow()) {
 183                 CFTemp<CFDictionaryRef> conditions((const char*)matches[0]);
 184                 return conditions.yield();
 185         }
 186         // no matches
 187         return NULL;
 188 }
 189
 190
 191 //
 192 // Convert a SHA1 hash to a hex string
 193 //
 194 static std::string hashString(CFDataRef hash)
 195 {
 196         if (CFDataGetLength(hash) != sizeof(SHA1::Digest)) {
 197                 return std::string();
 198         } else {
 199                 const UInt8 *bytes = CFDataGetBytePtr(hash);
 200                 char s[2 * SHA1::digestLength + 1];
 201                 for (unsigned n = 0; n < SHA1::digestLength; n++)
 202                         sprintf(&s[2*n], "%2.2x", bytes[n]);
 203                 return std::string(s);
 204         }
 205 }
 206
 207
 208 //
 209 // Add a code object to the whitelist
 210 //
 211 void OpaqueWhitelist::add(SecStaticCodeRef codeRef)
 212 {
 213         // make our own copy of the code object
 214         SecPointer<SecStaticCode> code = new SecStaticCode(SecStaticCode::requiredStatic(codeRef)->diskRep());
 215
 216         CFCopyRef<CFDataRef> current = code->cdHash();
 217         attachOpaque(code->handle(false), NULL);        // compute and attach an opaque signature
 218         CFDataRef opaque = code->cdHash();
 219
 220         SQLite::Statement insert(*this, "INSERT OR REPLACE INTO whitelist (current,opaque) VALUES (:current, :opaque)");
 221         insert.bind(":current") = current.get();
 222         insert.bind(":opaque") = opaque;
 223         insert.execute();
 224 }
 225
 226
 227 //
 228 // Generate and attach an ad-hoc opaque signature
 229 // Use SHA-1 digests because that's what the whitelist is made with
 230 //
 231 static void attachOpaque(SecStaticCodeRef code, SecAssessmentFeedback feedback)
 232 {
 233         CFTemp<CFDictionaryRef> rules("{"       // same resource rules as used for collection
 234                 "rules={"
 235                         "'^.*' = #T"
 236                         "'^Info\\.plist$' = {omit=#T,weight=10}"
 237                 "},rules2={"
 238                         "'^(Frameworks|SharedFrameworks|Plugins|Plug-ins|XPCServices|Helpers|MacOS)/' = {nested=#T, weight=0}"
 239                         "'^.*' = #T"
 240                         "'^Info\\.plist$' = {omit=#T,weight=10}"
 241                         "'^[^/]+$' = {top=#T, weight=0}"
 242                 "}"
 243         "}");
 244
 245         CFRef<CFDataRef> signature = CFDataCreateMutable(NULL, 0);
 246         CFTemp<CFDictionaryRef> arguments("{%O=%O, %O=#N, %O=%d, %O=%O}",
 247                 kSecCodeSignerDetached, signature.get(),
 248                 kSecCodeSignerIdentity, /* kCFNull, */
 249                 kSecCodeSignerDigestAlgorithm, kSecCodeSignatureHashSHA1,
 250                 kSecCodeSignerResourceRules, rules.get());
 251         CFRef<SecCodeSignerRef> signer;
 252         SecCSFlags creationFlags = kSecCSSignOpaque | kSecCSSignNoV1 | kSecCSSignBundleRoot;
 253         SecCSFlags operationFlags = 0;
 254
 255         if (feedback)
 256                 operationFlags |= kSecCSReportProgress;
 257         MacOSError::check(SecStaticCodeSetCallback(code, kSecCSDefaultFlags, NULL, ^CFTypeRef(SecStaticCodeRef code, CFStringRef stage, CFDictionaryRef info) {
 258                 if (CFEqual(stage, CFSTR("progress"))) {
 259                         bool proceed = feedback(kSecAssessmentFeedbackProgress, info);
 260                         if (!proceed)
 261                                 SecStaticCodeCancelValidation(code, kSecCSDefaultFlags);
 262                 }
 263                 return NULL;
 264         }));
 265
 266         MacOSError::check(SecCodeSignerCreate(arguments, creationFlags, &signer.aref()));
 267         MacOSError::check(SecCodeSignerAddSignature(signer, code, operationFlags));
 268         MacOSError::check(SecCodeSetDetachedSignature(code, signature, kSecCSDefaultFlags));
 269 }
 270
 271
 272 } // end namespace CodeSigning
 273 } // end namespace Security