OSX/sec/Security/SecOTRMath.c

   1 /*
   2  * Copyright (c) 2011-2012,2014 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 #include "SecOTRMath.h"
  26
  27 #include "SecOTRPacketData.h"
  28
  29 #include <utilities/SecCFWrappers.h>
  30 #include <AssertMacros.h>
  31
  32 #include <pthread.h>
  33
  34 #include <Security/SecRandom.h>
  35
  36 #include <corecrypto/ccsha2.h>
  37 #include <corecrypto/cczp.h>
  38 #include <corecrypto/ccdh_gp.h>
  39
  40 #include <limits.h>
  41
  42 //
  43 // Random Number Generation
  44 //
  45
  46 OSStatus GetRandomBytesInLSBs(size_t bytesOfRandomness, size_t n, cc_unit* place)
  47 {
  48     OSStatus result = errSecParam;
  49     require(bytesOfRandomness * 8 <= ccn_bitsof_n(n), fail);
  50     {
  51         uint8_t randomBytes[bytesOfRandomness];
  52
  53         result = SecRandomCopyBytes(kSecRandomDefault, sizeof(randomBytes), randomBytes);
  54
  55         require_noerr(result, fail);
  56
  57         ccn_read_uint(n, place, sizeof(randomBytes), randomBytes);
  58
  59         bzero(randomBytes, bytesOfRandomness);
  60     }
  61 fail:
  62     return result;
  63 }
  64
  65 OSStatus FillWithRandomBytes(size_t n, cc_unit* place)
  66 {
  67     return GetRandomBytesInLSBs(ccn_sizeof(n), n, place);
  68 }
  69
  70
  71 static const uint8_t kIVZero[16] = { };
  72
  73 static void AES_CTR_Transform(size_t keySize, const uint8_t* key,
  74                        const uint8_t iv[16],
  75                        size_t howMuch, const uint8_t* from, uint8_t* to)
  76 {
  77     const struct ccmode_ctr* ctr_encrypt = ccaes_ctr_crypt_mode();
  78     ccctr_ctx_decl(ctr_encrypt->size, ctr_ctx);
  79     ctr_encrypt->init(ctr_encrypt, ctr_ctx, keySize, key, iv);
  80
  81     ctr_encrypt->ctr(ctr_ctx, howMuch, from, to);
  82 }
  83
  84 void AES_CTR_HighHalf_Transform(size_t keySize, const uint8_t* key,
  85                                 uint64_t highHalf,
  86                                 size_t howMuch, const uint8_t* from, uint8_t* to)
  87 {
  88     uint8_t iv[16] = { highHalf >> 56, highHalf >> 48, highHalf >> 40, highHalf >> 32,
  89                        highHalf >> 24, highHalf >> 16, highHalf >> 8 , highHalf >> 0,
  90                                     0,              0,             0,              0,
  91                                     0,              0,             0,              0 };
  92     AES_CTR_Transform(keySize, key, iv, howMuch, from, to);
  93 }
  94
  95 void AES_CTR_IV0_Transform(size_t keySize, const uint8_t* key,
  96                            size_t howMuch, const uint8_t* from, uint8_t* to)
  97 {
  98     AES_CTR_Transform(keySize, key, kIVZero, howMuch, from, to);
  99 }
 100
 101
 102 //
 103 // Key Derivation
 104 //
 105
 106 static void HashMPIWithPrefix(uint8_t byte, cc_size sN, const cc_unit* s, uint8_t* buffer)
 107 {
 108     CFMutableDataRef dataToHash = CFDataCreateMutable(kCFAllocatorDefault, 0);
 109     CFDataAppendBytes(dataToHash, &byte, 1);
 110
 111     AppendMPI(dataToHash, sN, s);
 112
 113     uint8_t *bytesToHash = CFDataGetMutableBytePtr(dataToHash);
 114     CFIndex  amountToHash = CFDataGetLength(dataToHash);
 115
 116     /* 64 bits cast: amountToHash is the size of an identity +1 , which is currently hardcoded and never more than 2^32 bytes */
 117     assert((unsigned long)amountToHash<UINT32_MAX); /* Debug check, Correct as long as CFIndex is a signed long and CC_LONG is a uint32_t */
 118
 119     (void) CC_SHA256(bytesToHash, (CC_LONG)amountToHash, buffer);
 120
 121     bzero(bytesToHash, (size_t)amountToHash);
 122     CFReleaseNull(dataToHash);
 123 }
 124
 125 void DeriveOTR256BitsFromS(KeyType whichKey, cc_size sN, const cc_unit* s, size_t keySize, uint8_t* key)
 126 {
 127     HashMPIWithPrefix(whichKey, sN, s, key);
 128 }
 129
 130 void DeriveOTR128BitPairFromS(KeyType whichKey, size_t sSize, const cc_unit* s,
 131                               size_t firstKeySize, uint8_t* firstKey,
 132                               size_t secondKeySize, uint8_t* secondKey)
 133 {
 134     uint8_t hashBuffer[CCSHA256_OUTPUT_SIZE];
 135
 136     HashMPIWithPrefix(whichKey, sSize, s, hashBuffer);
 137
 138     if (firstKey) {
 139         firstKeySize = firstKeySize > CCSHA256_OUTPUT_SIZE/2 ? CCSHA256_OUTPUT_SIZE/2 : firstKeySize;
 140         memcpy(firstKey, hashBuffer, firstKeySize);
 141     }
 142     if (secondKey) {
 143         secondKeySize = secondKeySize > CCSHA256_OUTPUT_SIZE/2 ? CCSHA256_OUTPUT_SIZE/2 : secondKeySize;
 144         memcpy(secondKey, hashBuffer, secondKeySize);
 145     }
 146
 147     bzero(hashBuffer, CCSHA256_OUTPUT_SIZE);
 148
 149 }
 150
 151 void DeriveOTR64BitsFromS(KeyType whichKey, size_t sn, const cc_unit* s,
 152                           size_t topKeySize, uint8_t* topKey)
 153 {
 154     uint8_t hashBuffer[CCSHA256_OUTPUT_SIZE];
 155
 156     HashMPIWithPrefix(whichKey, sn, s, hashBuffer);
 157
 158     topKeySize = topKeySize > CCSHA256_OUTPUT_SIZE/2 ? CCSHA256_OUTPUT_SIZE/2 : topKeySize;
 159     memcpy(topKey, hashBuffer, topKeySize);
 160
 161     bzero(hashBuffer, CCSHA256_OUTPUT_SIZE);
 162 }
 163