git.distorted.org.uk Git - u/mdw/putty/blob - sshsha.c

   1 /*
   2  * SHA1 hash algorithm. Used in SSH2 as a MAC, and the transform is
   3  * also used as a `stirring' function for the PuTTY random number
   4  * pool. Implemented directly from the specification by Simon
   5  * Tatham.
   6  */
   7
   8 #include "ssh.h"
   9
  10 typedef unsigned int uint32;
  11
  12 /* ----------------------------------------------------------------------
  13  * Core SHA algorithm: processes 16-word blocks into a message digest.
  14  */
  15
  16 #define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) )
  17
  18 void SHA_Core_Init(uint32 h[5]) {
  19     h[0] = 0x67452301;
  20     h[1] = 0xefcdab89;
  21     h[2] = 0x98badcfe;
  22     h[3] = 0x10325476;
  23     h[4] = 0xc3d2e1f0;
  24 }
  25
  26 void SHATransform(word32 *digest, word32 *block) {
  27     word32 w[80];
  28     word32 a,b,c,d,e;
  29     int t;
  30
  31     for (t = 0; t < 16; t++)
  32         w[t] = block[t];
  33
  34     for (t = 16; t < 80; t++) {
  35         word32 tmp = w[t-3] ^ w[t-8] ^ w[t-14] ^ w[t-16];
  36         w[t] = rol(tmp, 1);
  37     }
  38
  39     a = digest[0];
  40     b = digest[1];
  41     c = digest[2];
  42     d = digest[3];
  43     e = digest[4];
  44
  45     for (t = 0; t < 20; t++) {
  46         word32 tmp = rol(a, 5) + ( (b&c) | (d&~b) ) + e + w[t] + 0x5a827999;
  47         e = d; d = c; c = rol(b, 30); b = a; a = tmp;
  48     }
  49     for (t = 20; t < 40; t++) {
  50         word32 tmp = rol(a, 5) + (b^c^d) + e + w[t] + 0x6ed9eba1;
  51         e = d; d = c; c = rol(b, 30); b = a; a = tmp;
  52     }
  53     for (t = 40; t < 60; t++) {
  54         word32 tmp = rol(a, 5) + ( (b&c) | (b&d) | (c&d) ) + e + w[t] + 0x8f1bbcdc;
  55         e = d; d = c; c = rol(b, 30); b = a; a = tmp;
  56     }
  57     for (t = 60; t < 80; t++) {
  58         word32 tmp = rol(a, 5) + (b^c^d) + e + w[t] + 0xca62c1d6;
  59         e = d; d = c; c = rol(b, 30); b = a; a = tmp;
  60     }
  61
  62     digest[0] += a;
  63     digest[1] += b;
  64     digest[2] += c;
  65     digest[3] += d;
  66     digest[4] += e;
  67 }
  68
  69 /* ----------------------------------------------------------------------
  70  * Outer SHA algorithm: take an arbitrary length byte string,
  71  * convert it into 16-word blocks with the prescribed padding at
  72  * the end, and pass those blocks to the core SHA algorithm.
  73  */
  74
  75 void SHA_Init(SHA_State *s) {
  76     SHA_Core_Init(s->h);
  77     s->blkused = 0;
  78     s->lenhi = s->lenlo = 0;
  79 }
  80
  81 void SHA_Bytes(SHA_State *s, void *p, int len) {
  82     unsigned char *q = (unsigned char *)p;
  83     uint32 wordblock[16];
  84     uint32 lenw = len;
  85     int i;
  86
  87     /*
  88      * Update the length field.
  89      */
  90     s->lenlo += lenw;
  91     s->lenhi += (s->lenlo < lenw);
  92
  93     if (s->blkused && s->blkused+len < 64) {
  94         /*
  95          * Trivial case: just add to the block.
  96          */
  97         memcpy(s->block + s->blkused, q, len);
  98         s->blkused += len;
  99     } else {
 100         /*
 101          * We must complete and process at least one block.
 102          */
 103         while (s->blkused + len >= 64) {
 104             memcpy(s->block + s->blkused, q, 64 - s->blkused);
 105             q += 64 - s->blkused;
 106             len -= 64 - s->blkused;
 107             /* Now process the block. Gather bytes big-endian into words */
 108             for (i = 0; i < 16; i++) {
 109                 wordblock[i] =
 110                     ( ((uint32)s->block[i*4+0]) << 24 ) |
 111                     ( ((uint32)s->block[i*4+1]) << 16 ) |
 112                     ( ((uint32)s->block[i*4+2]) <<  8 ) |
 113                     ( ((uint32)s->block[i*4+3]) <<  0 );
 114             }
 115             SHATransform(s->h, wordblock);
 116             s->blkused = 0;
 117         }
 118         memcpy(s->block, q, len);
 119         s->blkused = len;
 120     }
 121 }
 122
 123 void SHA_Final(SHA_State *s, unsigned char *output) {
 124     int i;
 125     int pad;
 126     unsigned char c[64];
 127     uint32 lenhi, lenlo;
 128
 129     if (s->blkused >= 56)
 130         pad = 56 + 64 - s->blkused;
 131     else
 132         pad = 56 - s->blkused;
 133
 134     lenhi = (s->lenhi << 3) | (s->lenlo >> (32-3));
 135     lenlo = (s->lenlo << 3);
 136
 137     memset(c, 0, pad);
 138     c[0] = 0x80;
 139     SHA_Bytes(s, &c, pad);
 140
 141     c[0] = (lenhi >> 24) & 0xFF;
 142     c[1] = (lenhi >> 16) & 0xFF;
 143     c[2] = (lenhi >>  8) & 0xFF;
 144     c[3] = (lenhi >>  0) & 0xFF;
 145     c[4] = (lenlo >> 24) & 0xFF;
 146     c[5] = (lenlo >> 16) & 0xFF;
 147     c[6] = (lenlo >>  8) & 0xFF;
 148     c[7] = (lenlo >>  0) & 0xFF;
 149
 150     SHA_Bytes(s, &c, 8);
 151
 152     for (i = 0; i < 5; i++) {
 153         output[i*4  ] = (s->h[i] >> 24) & 0xFF;
 154         output[i*4+1] = (s->h[i] >> 16) & 0xFF;
 155         output[i*4+2] = (s->h[i] >>  8) & 0xFF;
 156         output[i*4+3] = (s->h[i]      ) & 0xFF;
 157     }
 158 }
 159
 160 void SHA_Simple(void *p, int len, unsigned char *output) {
 161     SHA_State s;
 162
 163     SHA_Init(&s);
 164     SHA_Bytes(&s, p, len);
 165     SHA_Final(&s, output);
 166 }
 167
 168 /* ----------------------------------------------------------------------
 169  * The above is the SHA-1 algorithm itself. Now we implement the
 170  * HMAC wrapper on it.
 171  */
 172
 173 static SHA_State sha1_mac_s1, sha1_mac_s2;
 174
 175 static void sha1_sesskey(unsigned char *key, int len) {
 176     unsigned char foo[64];
 177     int i;
 178
 179     memset(foo, 0x36, 64);
 180     for (i = 0; i < len && i < 64; i++)
 181         foo[i] ^= key[i];
 182     SHA_Init(&sha1_mac_s1);
 183     SHA_Bytes(&sha1_mac_s1, foo, 64);
 184
 185     memset(foo, 0x5C, 64);
 186     for (i = 0; i < len && i < 64; i++)
 187         foo[i] ^= key[i];
 188     SHA_Init(&sha1_mac_s2);
 189     SHA_Bytes(&sha1_mac_s2, foo, 64);
 190
 191     memset(foo, 0, 64);                /* burn the evidence */
 192 }
 193
 194 static void sha1_do_hmac(unsigned char *blk, int len, unsigned long seq,
 195                          unsigned char *hmac) {
 196     SHA_State s;
 197     unsigned char intermediate[20];
 198
 199     intermediate[0] = (unsigned char)((seq >> 24) & 0xFF);
 200     intermediate[1] = (unsigned char)((seq >> 16) & 0xFF);
 201     intermediate[2] = (unsigned char)((seq >>  8) & 0xFF);
 202     intermediate[3] = (unsigned char)((seq      ) & 0xFF);
 203
 204     s = sha1_mac_s1;                   /* structure copy */
 205     SHA_Bytes(&s, intermediate, 4);
 206     SHA_Bytes(&s, blk, len);
 207     SHA_Final(&s, intermediate);
 208     s = sha1_mac_s2;                   /* structure copy */
 209     SHA_Bytes(&s, intermediate, 20);
 210     SHA_Final(&s, hmac);
 211 }
 212
 213 static void sha1_generate(unsigned char *blk, int len, unsigned long seq) {
 214     sha1_do_hmac(blk, len, seq, blk+len);
 215 }
 216
 217 static int sha1_verify(unsigned char *blk, int len, unsigned long seq) {
 218     unsigned char correct[20];
 219     sha1_do_hmac(blk, len, seq, correct);
 220     return !memcmp(correct, blk+len, 20);
 221 }
 222
 223 struct ssh_mac ssh_sha1 = {
 224     sha1_sesskey,
 225     sha1_generate,
 226     sha1_verify,
 227     "hmac-sha1",
 228     20
 229 };