OSX/sec/Security/SecRecoveryKey.m

   1 //
   2 //  SecRecoveryKey.c
   3 //
   4
   5 #import "SecRecoveryKey.h"
   6 #import <dispatch/dispatch.h>
   7
   8
   9 #import <corecrypto/cchkdf.h>
  10 #import <corecrypto/ccsha2.h>
  11 #import <corecrypto/ccec.h>
  12 #import <corecrypto/ccrng.h>
  13
  14 #import <utilities/SecCFWrappers.h>
  15 #import <AssertMacros.h>
  16
  17
  18 #import <Security/SecureObjectSync/SOSCloudCircle.h>
  19 #import "keychain/SecureObjectSync/SOSInternal.h"
  20
  21 #if !TARGET_OS_BRIDGE
  22 #include <dlfcn.h>
  23 #include <AppleIDAuthSupport/AppleIDAuthSupport.h>
  24 #define PATH_FOR_APPLEIDAUTHSUPPORTFRAMEWORK "/System/Library/PrivateFrameworks/AppleIDAuthSupport.framework/AppleIDAuthSupport"
  25 #endif
  26
  27 #import "SecCFAllocator.h"
  28 #import "SecPasswordGenerate.h"
  29 #import "SecBase64.h"
  30
  31 typedef struct _CFSecRecoveryKey *CFSecRecoveryKeyRef;
  32
  33
  34 static uint8_t backupPublicKey[] = { 'B', 'a', 'c', 'k', 'u', ' ', 'P', 'u', 'b', 'l', 'i', 'c', 'k', 'e', 'y' };
  35 static uint8_t passwordInfoKey[] = { 'p', 'a', 's', 's', 'w', 'o', 'r', 'd', ' ', 's', 'e', 'c', 'r', 'e', 't' };
  36 #if !(defined(__i386__) || TARGET_OS_SIMULATOR || TARGET_OS_BRIDGE)
  37 static uint8_t masterkeyIDSalt[] = { 'M', 'a', 's', 't', 'e', 'r', ' ', 'K', 'e', 'y', ' ', 'I', 'd', 'e', 't' };
  38 #endif
  39
  40 #define RK_BACKUP_HKDF_SIZE    128
  41 #define RK_PASSWORD_HKDF_SIZE  32
  42
  43 CFGiblisFor(CFSecRecoveryKey);
  44
  45 struct _CFSecRecoveryKey {
  46     CFRuntimeBase _base;
  47     CFDataRef basecode;
  48 };
  49
  50 static void
  51 CFSecRecoveryKeyDestroy(CFTypeRef cf)
  52 {
  53     CFSecRecoveryKeyRef rk = (CFSecRecoveryKeyRef)cf;
  54     CFReleaseNull(rk->basecode);
  55 }
  56
  57
  58 static CFStringRef
  59 CFSecRecoveryKeyCopyFormatDescription(CFTypeRef cf, CFDictionaryRef formatOptions)
  60 {
  61     return CFStringCreateWithFormat(NULL, NULL, CFSTR("<SecRecoveryKey: %p>"), cf);
  62 }
  63
  64
  65 static bool
  66 ValidateRecoveryKey(CFStringRef masterkey, NSError **error)
  67 {
  68     CFErrorRef cferror = NULL;
  69     bool res = SecPasswordValidatePasswordFormat(kSecPasswordTypeiCloudRecoveryKey, masterkey, &cferror);
  70     if (!res) {
  71         if (error) {
  72             *error = CFBridgingRelease(cferror);
  73         } else {
  74             CFReleaseNull(cferror);
  75         }
  76     }
  77     return res;
  78 }
  79
  80 NSString *
  81 SecRKCreateRecoveryKeyString(NSError **error)
  82 {
  83     CFErrorRef cferror = NULL;
  84
  85     CFStringRef recoveryKey = SecPasswordGenerate(kSecPasswordTypeiCloudRecoveryKey, &cferror, NULL);
  86     if (recoveryKey == NULL) {
  87         if (error) {
  88             *error = CFBridgingRelease(cferror);
  89         } else {
  90             CFReleaseNull(cferror);
  91         }
  92         return NULL;
  93     }
  94     if (!ValidateRecoveryKey(recoveryKey, error)) {
  95         CFRelease(recoveryKey);
  96         return NULL;
  97     }
  98     return (__bridge NSString *)recoveryKey;
  99 }
 100
 101 SecRecoveryKey *
 102 SecRKCreateRecoveryKey(NSString *masterKey)
 103 {
 104     return SecRKCreateRecoveryKeyWithError(masterKey, NULL);
 105 }
 106
 107 SecRecoveryKey *
 108 SecRKCreateRecoveryKeyWithError(NSString *masterKey, NSError **error)
 109 {
 110     if (!ValidateRecoveryKey((__bridge CFStringRef)masterKey, error)) {
 111         return NULL;
 112     }
 113
 114     CFSecRecoveryKeyRef rk = CFTypeAllocate(CFSecRecoveryKey, struct _CFSecRecoveryKey, NULL);
 115     if (rk == NULL)
 116         return NULL;
 117
 118     rk->basecode = CFStringCreateExternalRepresentation(SecCFAllocatorZeroize(),
 119                                                         (__bridge CFStringRef)masterKey,
 120                                                         kCFStringEncodingUTF8, 0);
 121     if (rk->basecode == NULL) {
 122         CFRelease(rk);
 123         return NULL;
 124     }
 125     return (SecRecoveryKey *) CFBridgingRelease(rk);
 126 }
 127
 128 static CFDataRef
 129 SecRKCreateDerivedSecret(CFSecRecoveryKeyRef rk, CFIndex outputLength,
 130                          const uint8_t *variant, size_t variantLength)
 131 {
 132     CFMutableDataRef derived;
 133     int status;
 134
 135     derived = CFDataCreateMutableWithScratch(SecCFAllocatorZeroize(), outputLength);
 136     if (derived == NULL)
 137         return NULL;
 138
 139     status = cchkdf(ccsha256_di(),
 140                     CFDataGetLength(rk->basecode), CFDataGetBytePtr(rk->basecode),
 141                     4, "salt",
 142                     variantLength, variant,
 143                     CFDataGetLength(derived), CFDataGetMutableBytePtr(derived));
 144     if (status) {
 145         CFReleaseNull(derived);
 146     }
 147     return derived;
 148 }
 149
 150
 151 NSString *
 152 SecRKCopyAccountRecoveryPassword(SecRecoveryKey *rk)
 153 {
 154     CFStringRef base64Data = NULL;
 155     CFDataRef derived = NULL;
 156     void *b64string = NULL;
 157     size_t base64Len = 0;
 158
 159     derived = SecRKCreateDerivedSecret((__bridge CFSecRecoveryKeyRef)rk,
 160                                        RK_PASSWORD_HKDF_SIZE,
 161                                        passwordInfoKey, sizeof(passwordInfoKey));
 162     require(derived, fail);
 163
 164     base64Len = SecBase64Encode(CFDataGetBytePtr(derived), CFDataGetLength(derived), NULL, 0);
 165     assert(base64Len < 1024);
 166
 167     b64string = malloc(base64Len);
 168     require(b64string, fail);
 169
 170     SecBase64Encode(CFDataGetBytePtr(derived), CFDataGetLength(derived), b64string, base64Len);
 171
 172     base64Data = CFStringCreateWithBytes(SecCFAllocatorZeroize(),
 173                                          (const UInt8 *)b64string, base64Len,
 174                                          kCFStringEncodingUTF8, false);
 175     require(base64Data, fail);
 176
 177 fail:
 178     if (b64string) {
 179         cc_clear(base64Len, b64string);
 180         free(b64string);
 181     }
 182     CFReleaseNull(derived);
 183
 184     return (__bridge NSString *)base64Data;
 185 }
 186
 187 // We should gen salt/iteration - use S2K for kdf for the time being
 188 // Pass back a dictionary of the parms
 189 //
 190 // Need companion call to respond with MRK on the "iforgot" sequence.
 191
 192 NSString *const kSecRVSalt = @"s";
 193 NSString *const kSecRVIterations = @"i";
 194 NSString *const kSecRVProtocol = @"p";
 195 NSString *const kSecRVVerifier = @"v";
 196 NSString *const kSecRVMasterID = @"mkid";
 197
 198 #if !TARGET_OS_BRIDGE
 199
 200 CFStringRef localProtocolSRPGROUP;
 201 CFDataRef (*localAppleIDauthSupportCreateVerifierPtr) (CFStringRef proto,
 202                                                 CFStringRef username,
 203                                                 CFDataRef salt,
 204                                                 CFNumberRef iter,
 205                                                 CFStringRef password,
 206                                                 CFErrorRef *error);
 207
 208 #if !(defined(__i386__) || TARGET_OS_SIMULATOR)
 209 static CFStringRef getdlsymforString(void *framework, const char *symbol) {
 210     CFStringRef retval = NULL;
 211     void *tmpptr = dlsym(framework, symbol);
 212     if(tmpptr) {
 213         retval = *(CFStringRef*) tmpptr;
 214     }
 215     return retval;
 216 }
 217
 218 static bool connectAppleIDFrameworkSymbols(void) {
 219     static dispatch_once_t onceToken;
 220     static void* framework = NULL;
 221     dispatch_once(&onceToken, ^{
 222         localAppleIDauthSupportCreateVerifierPtr = NULL;
 223         localProtocolSRPGROUP = NULL;
 224         framework = dlopen(PATH_FOR_APPLEIDAUTHSUPPORTFRAMEWORK, RTLD_NOW);
 225         if(framework) {
 226             localProtocolSRPGROUP = getdlsymforString(framework,
 227                 "kAppleIDAuthSupportProtocolSRPGROUP2048SHA256PBKDF");
 228             localAppleIDauthSupportCreateVerifierPtr =
 229                 dlsym(framework, "AppleIDAuthSupportCreateVerifier");
 230         }
 231     });
 232     return (framework != NULL && localProtocolSRPGROUP != NULL &&
 233             localAppleIDauthSupportCreateVerifierPtr != NULL);
 234 }
 235 #endif
 236 #endif
 237
 238 NSDictionary *
 239 SecRKCopyAccountRecoveryVerifier(NSString *recoveryKey,
 240                                  NSError **error) {
 241
 242 #if defined(__i386__) || TARGET_OS_SIMULATOR || TARGET_OS_BRIDGE
 243     abort();
 244     return NULL;
 245 #else
 246     CFErrorRef localError = NULL;
 247     CFStringRef username = CFSTR("foo");
 248     NSDictionary *retval = nil;
 249     if(!connectAppleIDFrameworkSymbols()) {
 250         SOSCreateError(kSOSErrorUnsupported, CFSTR("Recovery Key Creation Not Supported on this platform"), NULL, &localError);
 251         if(error) *error = (__bridge_transfer NSError *) localError;
 252         return NULL;
 253     }
 254
 255     NSData *salt = (__bridge_transfer NSData*) CFDataCreateWithRandomBytes(32);
 256     NSNumber *iterations = @40000;
 257     NSString *protocol = (__bridge NSString*) localProtocolSRPGROUP;
 258     NSData *verifier = (__bridge_transfer NSData*) localAppleIDauthSupportCreateVerifierPtr(
 259                                     localProtocolSRPGROUP,
 260                                     username,
 261                                     (__bridge CFDataRef) salt,
 262                                     (__bridge CFNumberRef) iterations,
 263                                     (__bridge CFStringRef) (recoveryKey),
 264                                     &localError);
 265     SecRecoveryKey *srk = SecRKCreateRecoveryKey(recoveryKey);
 266     NSData *masterKeyID = (__bridge_transfer NSData*) SecRKCreateDerivedSecret(
 267                                     (__bridge CFSecRecoveryKeyRef) srk,
 268                                     RK_PASSWORD_HKDF_SIZE,
 269                                     masterkeyIDSalt,
 270                                     sizeof(masterkeyIDSalt));
 271     if(verifier && masterKeyID) {
 272         retval = @{ kSecRVSalt: salt,
 273                     kSecRVIterations: iterations,
 274                     kSecRVProtocol: protocol,
 275                     kSecRVVerifier: verifier,
 276                     kSecRVMasterID: masterKeyID };
 277
 278     } else {
 279         if(error && localError) *error = (__bridge NSError *) localError;
 280     }
 281     return retval;
 282 #endif
 283
 284 }
 285
 286 // This recreates the key pair using the recovery key string.
 287 static NSData *
 288 RKBackupCreateECKey(SecRecoveryKey *rk, bool returnFullkey)
 289 {
 290     CFMutableDataRef keyData = NULL;
 291     CFDataRef derivedSecret = NULL;
 292     ccec_const_cp_t cp = ccec_cp_256();
 293     CFDataRef result = NULL;
 294     int status;
 295
 296     ccec_full_ctx_decl_cp(cp, fullKey);
 297
 298     derivedSecret = SecRKCreateDerivedSecret((__bridge CFSecRecoveryKeyRef)rk, RK_BACKUP_HKDF_SIZE,
 299                                              backupPublicKey, sizeof(backupPublicKey));
 300     require(derivedSecret, fail);
 301
 302     status = ccec_generate_key_deterministic(cp,
 303                                              CFDataGetLength(derivedSecret), CFDataGetBytePtr(derivedSecret),
 304                                              ccrng(NULL),
 305                                              CCEC_GENKEY_DETERMINISTIC_COMPACT,
 306                                              fullKey);
 307     require_noerr(status, fail);
 308
 309     size_t space = ccec_compact_export_size(returnFullkey, ccec_ctx_pub(fullKey));
 310     keyData = CFDataCreateMutableWithScratch(SecCFAllocatorZeroize(), space);
 311     require_quiet(keyData, fail);
 312
 313     ccec_compact_export(returnFullkey, CFDataGetMutableBytePtr(keyData), fullKey);
 314
 315     CFTransferRetained(result, keyData);
 316 fail:
 317     CFReleaseNull(derivedSecret);
 318     CFReleaseNull(keyData);
 319
 320     return (__bridge NSData *)result;
 321 }
 322
 323 NSData *
 324 SecRKCopyBackupFullKey(SecRecoveryKey *rk)
 325 {
 326     return RKBackupCreateECKey(rk, true);
 327 }
 328
 329
 330 NSData *
 331 SecRKCopyBackupPublicKey(SecRecoveryKey *rk)
 332 {
 333     return RKBackupCreateECKey(rk, false);
 334 }
 335
 336 bool
 337 SecRKRegisterBackupPublicKey(SecRecoveryKey *rk, CFErrorRef *error)
 338 {
 339     CFDataRef backupKey = (__bridge CFDataRef)SecRKCopyBackupPublicKey(rk);
 340     bool res = false;
 341
 342     require_action_quiet(backupKey, fail, SOSCreateError(kSOSErrorBadKey, CFSTR("Failed to create key from rk"), NULL, error));
 343
 344     res = SOSCCRegisterRecoveryPublicKey(backupKey, error);
 345
 346 fail:
 347     CFReleaseNull(backupKey);
 348
 349     return res;
 350 }