Security/libsecurity_codesigning/lib/opaquewhitelist.cpp

   1 /*
   2  * Copyright (c) 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 #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         SQLite::Statement lookup(*this, "SELECT opaque FROM whitelist WHERE current=:current"
 111                 " AND opaque != 'disable override'");
 112         lookup.bind(":current") = current.get();
 113         while (lookup.nextRow()) {
 114                 CFRef<CFDataRef> expected = lookup[0].data();
 115                 if (CFEqual(opaque, expected)) {
 116                         match = true;   // actual opaque cdhash matches expected
 117                         break;
 118                 }
 119         }
 120
 121         // prepare strings for use inside block
 122         std::string currentHash = hashString(current);
 123         std::string opaqueHash = hashString(opaque);
 124         std::string identifier = code->identifier();
 125         std::string longVersion = cfString(cfShortVersion) + " (" + cfString(cfVersion) + ")";
 126
 127         // check override killswitch
 128         bool enableOverride = true;
 129         SQLite::Statement killswitch(*this,
 130                 "SELECT 1 FROM whitelist"
 131                 " WHERE current='disable override'"
 132                 " OR (current=:current AND opaque='disable override')"
 133                 " LIMIT 1");
 134         killswitch.bind(":current") = current.get();
 135         if (killswitch.nextRow())
 136                 enableOverride = false;
 137
 138         // allow external program to override decision
 139         __block bool override = false;
 140         if (!match && enableOverride) {
 141                 dispatch_group_t group = dispatch_group_create();
 142                 dispatch_group_async(group, mOverrideQueue, ^{
 143                         const char *argv[] = {
 144                                 "/usr/libexec/gkoverride",
 145                                 currentHash.c_str(),
 146                                 opaqueHash.c_str(),
 147                                 identifier.c_str(),
 148                                 longVersion.c_str(),
 149                                 NULL    // sentinel
 150                         };
 151                         int pid, status = 0;
 152                         if (posix_spawn(&pid, argv[0], NULL, NULL, (char **)argv, NULL) == 0)
 153                                 if (waitpid(pid, &status, 0) == pid && WIFEXITED(status) && WEXITSTATUS(status) == 42)
 154                                         override = true;
 155                 });
 156                 dispatch_group_wait(group, dispatch_walltime(DISPATCH_TIME_NOW, 5 * NSEC_PER_SEC));
 157                 dispatch_release(group);
 158                 if (override)
 159                         match = true;
 160         }
 161
 162         // send a trace indicating the result
 163         MessageTrace trace("com.apple.security.assessment.whitelist2", code->identifier().c_str());
 164         trace.add("signature2", "%s", currentHash.c_str());
 165         trace.add("signature3", "%s", opaqueHash.c_str());
 166         trace.add("result", match ? "pass" : "fail");
 167         trace.add("reason", "%d", reason);
 168         trace.add("override", "%d", override);
 169         if (!team.empty())
 170                 trace.add("teamid", "%s", team.c_str());
 171         if (cfVersion)
 172                 trace.add("version", "%s", cfString(cfVersion).c_str());
 173         if (cfShortVersion)
 174                 trace.add("version2", "%s", cfString(cfShortVersion).c_str());
 175         if (cfExecutable)
 176                 trace.add("execname", "%s", cfString(cfExecutable).c_str());
 177         trace.send("");
 178
 179         return match;
 180 }
 181
 182
 183 //
 184 // Obtain special validation conditions for a static code, based on database configuration.
 185 //
 186 CFDictionaryRef OpaqueWhitelist::validationConditionsFor(SecStaticCodeRef code)
 187 {
 188         // figure out which team key to use
 189         std::string team = "UNKNOWN";
 190         CFStringRef cfId = NULL;
 191         CFStringRef cfVersion = NULL;
 192         CFRef<CFDictionaryRef> info;    // holds lifetimes for the above
 193         if (errSecSuccess == SecCodeCopySigningInformation(code, kSecCSSigningInformation, &info.aref())) {
 194                 if (CFStringRef cfTeam = CFStringRef(CFDictionaryGetValue(info, kSecCodeInfoTeamIdentifier)))
 195                         team = cfString(cfTeam);
 196                 cfId = CFStringRef(CFDictionaryGetValue(info, kSecCodeInfoIdentifier));
 197                 if (CFDictionaryRef infoPlist = CFDictionaryRef(CFDictionaryGetValue(info, kSecCodeInfoPList)))
 198                         if (CFTypeRef version = CFDictionaryGetValue(infoPlist, _kCFBundleShortVersionStringKey))
 199                                 if (CFGetTypeID(version) == CFStringGetTypeID())
 200                                         cfVersion = CFStringRef(version);
 201         }
 202         if (cfId == NULL)       // unsigned; punt
 203                 return NULL;
 204
 205         // find the highest weight matching condition. We perform no merging and the heaviest rule wins
 206         SQLite::Statement matches(*this,
 207                 "SELECT conditions FROM conditions"
 208                 " WHERE (source = :source or source IS NULL)"
 209                 " AND (identifier = :identifier or identifier is NULL)"
 210                 " AND ((:version IS NULL AND version IS NULL) OR (version = :version OR version IS NULL))"
 211                 " ORDER BY weight DESC"
 212                 " LIMIT 1"
 213         );
 214         matches.bind(":source") = team;
 215         matches.bind(":identifier") = cfString(cfId);
 216         if (cfVersion)
 217                 matches.bind(":version") = cfString(cfVersion);
 218         if (matches.nextRow()) {
 219                 CFTemp<CFDictionaryRef> conditions((const char*)matches[0]);
 220                 return conditions.yield();
 221         }
 222         // no matches
 223         return NULL;
 224 }
 225
 226
 227 //
 228 // Convert a SHA1 hash to a hex string
 229 //
 230 static std::string hashString(CFDataRef hash)
 231 {
 232         if (CFDataGetLength(hash) != sizeof(SHA1::Digest)) {
 233                 return std::string();
 234         } else {
 235                 const UInt8 *bytes = CFDataGetBytePtr(hash);
 236                 char s[2 * SHA1::digestLength + 1];
 237                 for (unsigned n = 0; n < SHA1::digestLength; n++)
 238                         sprintf(&s[2*n], "%2.2x", bytes[n]);
 239                 return std::string(s);
 240         }
 241 }
 242
 243
 244 //
 245 // Add a code object to the whitelist
 246 //
 247 void OpaqueWhitelist::add(SecStaticCodeRef codeRef)
 248 {
 249         // make our own copy of the code object
 250         SecPointer<SecStaticCode> code = new SecStaticCode(SecStaticCode::requiredStatic(codeRef)->diskRep());
 251
 252         CFCopyRef<CFDataRef> current = code->cdHash();
 253         attachOpaque(code->handle(false), NULL);        // compute and attach an opaque signature
 254         CFDataRef opaque = code->cdHash();
 255
 256         SQLite::Statement insert(*this, "INSERT OR REPLACE INTO whitelist (current,opaque) VALUES (:current, :opaque)");
 257         insert.bind(":current") = current.get();
 258         insert.bind(":opaque") = opaque;
 259         insert.execute();
 260 }
 261
 262
 263 //
 264 // Generate and attach an ad-hoc opaque signature
 265 //
 266 static void attachOpaque(SecStaticCodeRef code, SecAssessmentFeedback feedback)
 267 {
 268         CFTemp<CFDictionaryRef> rules("{"       // same resource rules as used for collection
 269                 "rules={"
 270                         "'^.*' = #T"
 271                         "'^Info\\.plist$' = {omit=#T,weight=10}"
 272                 "},rules2={"
 273                         "'^(Frameworks|SharedFrameworks|Plugins|Plug-ins|XPCServices|Helpers|MacOS)/' = {nested=#T, weight=0}"
 274                         "'^.*' = #T"
 275                         "'^Info\\.plist$' = {omit=#T,weight=10}"
 276                         "'^[^/]+$' = {top=#T, weight=0}"
 277                 "}"
 278         "}");
 279
 280         CFRef<CFDataRef> signature = CFDataCreateMutable(NULL, 0);
 281         CFTemp<CFDictionaryRef> arguments("{%O=%O, %O=#N, %O=%O}",
 282                 kSecCodeSignerDetached, signature.get(),
 283                 kSecCodeSignerIdentity, /* kCFNull, */
 284                 kSecCodeSignerResourceRules, rules.get());
 285         CFRef<SecCodeSignerRef> signer;
 286         SecCSFlags creationFlags = kSecCSSignOpaque | kSecCSSignNoV1 | kSecCSSignBundleRoot;
 287         SecCSFlags operationFlags = 0;
 288
 289         if (feedback)
 290                 operationFlags |= kSecCSReportProgress;
 291         MacOSError::check(SecStaticCodeSetCallback(code, kSecCSDefaultFlags, NULL, ^CFTypeRef(SecStaticCodeRef code, CFStringRef stage, CFDictionaryRef info) {
 292                 if (CFEqual(stage, CFSTR("progress"))) {
 293                         bool proceed = feedback(kSecAssessmentFeedbackProgress, info);
 294                         if (!proceed)
 295                                 SecStaticCodeCancelValidation(code, kSecCSDefaultFlags);
 296                 }
 297                 return NULL;
 298         }));
 299
 300         MacOSError::check(SecCodeSignerCreate(arguments, creationFlags, &signer.aref()));
 301         MacOSError::check(SecCodeSignerAddSignature(signer, code, operationFlags));
 302         MacOSError::check(SecCodeSetDetachedSignature(code, signature, kSecCSDefaultFlags));
 303 }
 304
 305
 306 } // end namespace CodeSigning
 307 } // end namespace Security