libsecurity_cryptkit/lib/HmacSha1Legacy.c

   1 /*
   2  * Copyright (c) 2000-2001 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18
  19 /*
  20         File:           HmacSha1Legacy.c
  21         Contains:       HMAC/SHA1, bug-for-bug compatible with BSAFE 4.0.
  22         Copyright:      (C) 2001 by Apple Computer, Inc., all rights reserved
  23         Written by:     Doug Mitchell
  24 */
  25
  26 #include "ckconfig.h"
  27
  28 #if     CRYPTKIT_HMAC_LEGACY
  29
  30 #include "HmacSha1Legacy.h"
  31 #include "ckSHA1.h"
  32 #include <string.h>
  33 #include <stdlib.h>
  34 #include <Security/SecBase.h>
  35 #define kHMACSHA1DigestSize  20
  36
  37 /* XXX These should really be in ckSHA1.h */
  38 #define kSHA1DigestSize         20
  39 #define kSHA1BlockSize          64
  40
  41 /*
  42  * bug-for-bug compatible with BSAFE 4.0. See
  43  * BSafe/bsource/algs/ahchhmac.c.
  44  *
  45  * This implementation, and the BSAFE implementation it emulates, work fine
  46  * when calculating a MAC in a single update (init, update, final). They
  47  * generate nonconforming MACs when performing multiple updates because
  48  * the entire algorithm - both inner and outer digests - are performed
  49  * in the update() step. As a result, if one e.g. calculates a MAC of
  50  * a block of text with one update, and then calculates the MAC over the
  51  * same block of text via two updates, different results will obtain.ÊThe
  52  * incorrect result from the multiple-update scenario is repeatable if and
  53  * only if the same boundaries (same update sizes) are observed on each operation.
  54  *
  55  * Because all of the data to be MAC'd is in fact protected by both levels of
  56  * SHA1, and all of the key bits are used, this nonconforming implementation is
  57  * believed to be as strong, cryptographically, as a conforming SHA1HMAC
  58  * implementation.
  59  */
  60 struct hmacLegacyContext {
  61         sha1Obj sha1Context;
  62         UInt8   k_ipad[kSHA1BlockSize];
  63         UInt8   k_opad[kSHA1BlockSize];
  64 };
  65
  66 hmacLegacyContextRef hmacLegacyAlloc(void)
  67 {
  68         hmacLegacyContextRef hmac =
  69                 (hmacLegacyContextRef)malloc(sizeof(struct hmacLegacyContext));
  70         memset(hmac, 0, sizeof(struct hmacLegacyContext));
  71         return hmac;
  72 }
  73
  74 void hmacLegacyFree(
  75         hmacLegacyContextRef hmac)
  76 {
  77         if(hmac != NULL) {
  78                 if(hmac->sha1Context != NULL) {
  79                         sha1Free (hmac->sha1Context);
  80                 }
  81                 memset(hmac, 0, sizeof(struct hmacLegacyContext));
  82                 free(hmac);
  83         }
  84 }
  85
  86 /* reusable init */
  87 OSStatus hmacLegacyInit(
  88         hmacLegacyContextRef hmac,
  89         const void *keyPtr,
  90         UInt32 keyLen)
  91 {
  92         UInt8   *key;
  93         UInt32  byte;
  94
  95         if(hmac->sha1Context == NULL) {
  96                 hmac->sha1Context = sha1Alloc();
  97                 if(hmac->sha1Context == NULL) {
  98                         return errSecAllocate;
  99                 }
 100         }
 101         else {
 102                 sha1Reinit(hmac->sha1Context);
 103         }
 104         /* this implementation requires a 20-byte key */
 105         if (keyLen != kSHA1DigestSize) {
 106                 /* FIXME */
 107                 return errSecParam;
 108         }
 109         key = (UInt8*)keyPtr;
 110
 111         /* The HMAC_SHA_1 transform looks like:
 112            SHA1 (K XOR opad || SHA1 (K XOR ipad || text))
 113            Where K is a n byte key
 114            ipad is the byte 0x36 repeated 64 times.
 115            opad is the byte 0x5c repeated 64 times.
 116            text is the data being protected.
 117           */
 118         /* Copy the key into k_ipad and k_opad while doing the XOR. */
 119         for (byte = 0; byte < keyLen; byte++)
 120         {
 121                 hmac->k_ipad[byte] = key[byte] ^ 0x36;
 122                 hmac->k_opad[byte] = key[byte] ^ 0x5c;
 123         }
 124
 125         /* Fill the remainder of k_ipad and k_opad with 0 XORed with
 126          * appropriate value. */
 127         memset (hmac->k_ipad + keyLen, 0x36, kSHA1BlockSize - keyLen);
 128         memset (hmac->k_opad + keyLen, 0x5c, kSHA1BlockSize - keyLen);
 129
 130         /* remainder happens in update */
 131         return errSecSuccess;
 132 }
 133
 134 OSStatus hmacLegacyUpdate(
 135         hmacLegacyContextRef hmac,
 136         const void *textPtr,
 137         UInt32 textLen)
 138 {
 139         UInt8 innerDigest[kSHA1DigestSize];
 140
 141         /* compute SHA1(k_ipad || data) ==> innerDigest */
 142         sha1AddData (hmac->sha1Context, hmac->k_ipad, kSHA1BlockSize);
 143         sha1AddData (hmac->sha1Context, (UInt8*)textPtr, textLen);
 144         memcpy (innerDigest, sha1Digest(hmac->sha1Context), kSHA1DigestSize);
 145
 146         /* reset context (BSAFE does this implicitly in a final() call) */
 147         sha1Reinit(hmac->sha1Context);
 148
 149         /* compute SHA1(k_opad || innerDigest) */
 150         sha1AddData (hmac->sha1Context, hmac->k_opad, kSHA1BlockSize);
 151         sha1AddData (hmac->sha1Context, innerDigest, kSHA1DigestSize);
 152
 153         /* if there is another update coming, it gets added in to existing
 154          * context; if the next step is a final, the current digest state is used. */
 155         return errSecSuccess;
 156 }
 157
 158 OSStatus hmacLegacyFinal(
 159         hmacLegacyContextRef hmac,
 160         void *resultPtr)                // caller mallocs, must be HMACSHA1_OUT_SIZE bytes
 161 {
 162         memcpy (resultPtr, sha1Digest (hmac->sha1Context), kSHA1DigestSize);
 163         return errSecSuccess;
 164 }
 165
 166 #endif  /* CRYPTKIT_HMAC_LEGACY */