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