engines/ccgost/gost_keywrap.c

   1 /**********************************************************************
   2  *                          keywrap.c                                 *
   3  *             Copyright (c) 2005-2006 Cryptocom LTD                  *
   4  *         This file is distributed under the same license as OpenSSL *
   5  *                                                                    *
   6  * Implementation of CryptoPro key wrap algorithm, as defined in      *
   7  *               RFC 4357 p 6.3 and 6.4                               *
   8  *                  Doesn't need OpenSSL                              *
   9  **********************************************************************/
  10 #include <string.h>
  11 #include "gost89.h"
  12 #include "gost_keywrap.h"
  13
  14 /*-
  15  * Diversifies key using random UserKey Material
  16  * Implements RFC 4357 p 6.5 key diversification algorithm
  17  *
  18  * inputKey - 32byte key to be diversified
  19  * ukm - 8byte user key material
  20  * outputKey - 32byte buffer to store diversified key
  21  *
  22  */
  23 void keyDiversifyCryptoPro(gost_ctx *ctx,const unsigned char *inputKey, const unsigned char *ukm, unsigned char *outputKey)
  24         {
  25
  26         u4 k,s1,s2;
  27         int i,j,mask;
  28         unsigned char S[8];
  29         memcpy(outputKey,inputKey,32);
  30         for (i=0;i<8;i++)
  31                 {
  32                 /* Make array of integers from key */
  33                 /* Compute IV S*/
  34                 s1=0,s2=0;
  35                 for (j=0,mask=1;j<8;j++,mask<<=1)
  36                         {
  37                         k=((u4)outputKey[4*j])|(outputKey[4*j+1]<<8)|
  38                                 (outputKey[4*j+2]<<16)|(outputKey[4*j+3]<<24);
  39                         if (mask & ukm[i])
  40                                 {
  41                                 s1+=k;
  42                                 }
  43                         else
  44                                 {
  45                                 s2+=k;
  46                                 }
  47                         }
  48                 S[0]=(unsigned char)(s1&0xff);
  49                 S[1]=(unsigned char)((s1>>8)&0xff);
  50                 S[2]=(unsigned char)((s1>>16)&0xff);
  51                 S[3]=(unsigned char)((s1>>24)&0xff);
  52                 S[4]=(unsigned char)(s2&0xff);
  53                 S[5]=(unsigned char)((s2>>8)&0xff);
  54                 S[6]=(unsigned char)((s2>>16)&0xff);
  55                 S[7]=(unsigned char)((s2>>24)&0xff);
  56                 gost_key(ctx,outputKey);
  57                 gost_enc_cfb(ctx,S,outputKey,outputKey,4);
  58                 }
  59         }
  60
  61
  62 /*-
  63  * Wraps key using RFC 4357 6.3
  64  * ctx - gost encryption context, initialized with some S-boxes
  65  * keyExchangeKey (KEK) 32-byte (256-bit) shared key
  66  * ukm - 8 byte (64 bit) user key material,
  67  * sessionKey - 32-byte (256-bit) key to be wrapped
  68  * wrappedKey - 44-byte buffer to store wrapped key
  69  */
  70
  71 int keyWrapCryptoPro(gost_ctx *ctx,const unsigned char *keyExchangeKey, const unsigned char *ukm,
  72         const   unsigned char *sessionKey, unsigned char *wrappedKey)
  73         {
  74         unsigned char kek_ukm[32];
  75         keyDiversifyCryptoPro(ctx,keyExchangeKey,ukm,kek_ukm);
  76         gost_key(ctx,kek_ukm);
  77         memcpy(wrappedKey,ukm,8);
  78         gost_enc(ctx,sessionKey,wrappedKey+8,4);
  79         gost_mac_iv(ctx,32,ukm,sessionKey,32,wrappedKey+40);
  80         return 1;
  81         }
  82 /*-
  83  * Unwraps key using RFC 4357 6.4
  84  * ctx - gost encryption context, initialized with some S-boxes
  85  * keyExchangeKey 32-byte shared key
  86  * wrappedKey  44 byte key to be unwrapped (concatenation of 8-byte UKM,
  87  * 32 byte  encrypted key and 4 byte MAC
  88  *
  89  * sessionKEy - 32byte buffer to store sessionKey in
  90  * Returns 1 if key is decrypted successfully, and 0 if MAC doesn't match
  91  */
  92
  93 int keyUnwrapCryptoPro(gost_ctx *ctx,const unsigned char *keyExchangeKey,
  94         const unsigned char *wrappedKey, unsigned char *sessionKey)
  95         {
  96         unsigned char kek_ukm[32],cek_mac[4];
  97         keyDiversifyCryptoPro(ctx,keyExchangeKey,wrappedKey
  98                 /* First 8 bytes of wrapped Key is ukm */
  99                 ,kek_ukm);
 100         gost_key(ctx,kek_ukm);
 101         gost_dec(ctx,wrappedKey+8,sessionKey,4);
 102         gost_mac_iv(ctx,32,wrappedKey,sessionKey,32,cek_mac);
 103         if (memcmp(cek_mac,wrappedKey+40,4))
 104                 {
 105                 return 0;
 106                 }
 107         return 1;
 108         }
 109
 110