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 /* ----------------------------------------------------------------------
  11  * Core SHA algorithm: processes 16-word blocks into a message digest.
  12  */
  13
  14 #define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) )
  15
  16 void SHA_Core_Init(uint32 h[5])
  17 {
  18     h[0] = 0x67452301;
  19     h[1] = 0xefcdab89;
  20     h[2] = 0x98badcfe;
  21     h[3] = 0x10325476;
  22     h[4] = 0xc3d2e1f0;
  23 }
  24
  25 void SHATransform(word32 * digest, word32 * block)
  26 {
  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 =
  47             rol(a, 5) + ((b & c) | (d & ~b)) + e + w[t] + 0x5a827999;
  48         e = d;
  49         d = c;
  50         c = rol(b, 30);
  51         b = a;
  52         a = tmp;
  53     }
  54     for (t = 20; t < 40; t++) {
  55         word32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0x6ed9eba1;
  56         e = d;
  57         d = c;
  58         c = rol(b, 30);
  59         b = a;
  60         a = tmp;
  61     }
  62     for (t = 40; t < 60; t++) {
  63         word32 tmp = rol(a,
  64                          5) + ((b & c) | (b & d) | (c & d)) + e + w[t] +
  65             0x8f1bbcdc;
  66         e = d;
  67         d = c;
  68         c = rol(b, 30);
  69         b = a;
  70         a = tmp;
  71     }
  72     for (t = 60; t < 80; t++) {
  73         word32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0xca62c1d6;
  74         e = d;
  75         d = c;
  76         c = rol(b, 30);
  77         b = a;
  78         a = tmp;
  79     }
  80
  81     digest[0] += a;
  82     digest[1] += b;
  83     digest[2] += c;
  84     digest[3] += d;
  85     digest[4] += e;
  86 }
  87
  88 /* ----------------------------------------------------------------------
  89  * Outer SHA algorithm: take an arbitrary length byte string,
  90  * convert it into 16-word blocks with the prescribed padding at
  91  * the end, and pass those blocks to the core SHA algorithm.
  92  */
  93
  94 void SHA_Init(SHA_State * s)
  95 {
  96     SHA_Core_Init(s->h);
  97     s->blkused = 0;
  98     s->lenhi = s->lenlo = 0;
  99 }
 100
 101 void SHA_Bytes(SHA_State * s, void *p, int len)
 102 {
 103     unsigned char *q = (unsigned char *) p;
 104     uint32 wordblock[16];
 105     uint32 lenw = len;
 106     int i;
 107
 108     /*
 109      * Update the length field.
 110      */
 111     s->lenlo += lenw;
 112     s->lenhi += (s->lenlo < lenw);
 113
 114     if (s->blkused && s->blkused + len < 64) {
 115         /*
 116          * Trivial case: just add to the block.
 117          */
 118         memcpy(s->block + s->blkused, q, len);
 119         s->blkused += len;
 120     } else {
 121         /*
 122          * We must complete and process at least one block.
 123          */
 124         while (s->blkused + len >= 64) {
 125             memcpy(s->block + s->blkused, q, 64 - s->blkused);
 126             q += 64 - s->blkused;
 127             len -= 64 - s->blkused;
 128             /* Now process the block. Gather bytes big-endian into words */
 129             for (i = 0; i < 16; i++) {
 130                 wordblock[i] =
 131                     (((uint32) s->block[i * 4 + 0]) << 24) |
 132                     (((uint32) s->block[i * 4 + 1]) << 16) |
 133                     (((uint32) s->block[i * 4 + 2]) << 8) |
 134                     (((uint32) s->block[i * 4 + 3]) << 0);
 135             }
 136             SHATransform(s->h, wordblock);
 137             s->blkused = 0;
 138         }
 139         memcpy(s->block, q, len);
 140         s->blkused = len;
 141     }
 142 }
 143
 144 void SHA_Final(SHA_State * s, unsigned char *output)
 145 {
 146     int i;
 147     int pad;
 148     unsigned char c[64];
 149     uint32 lenhi, lenlo;
 150
 151     if (s->blkused >= 56)
 152         pad = 56 + 64 - s->blkused;
 153     else
 154         pad = 56 - s->blkused;
 155
 156     lenhi = (s->lenhi << 3) | (s->lenlo >> (32 - 3));
 157     lenlo = (s->lenlo << 3);
 158
 159     memset(c, 0, pad);
 160     c[0] = 0x80;
 161     SHA_Bytes(s, &c, pad);
 162
 163     c[0] = (lenhi >> 24) & 0xFF;
 164     c[1] = (lenhi >> 16) & 0xFF;
 165     c[2] = (lenhi >> 8) & 0xFF;
 166     c[3] = (lenhi >> 0) & 0xFF;
 167     c[4] = (lenlo >> 24) & 0xFF;
 168     c[5] = (lenlo >> 16) & 0xFF;
 169     c[6] = (lenlo >> 8) & 0xFF;
 170     c[7] = (lenlo >> 0) & 0xFF;
 171
 172     SHA_Bytes(s, &c, 8);
 173
 174     for (i = 0; i < 5; i++) {
 175         output[i * 4] = (s->h[i] >> 24) & 0xFF;
 176         output[i * 4 + 1] = (s->h[i] >> 16) & 0xFF;
 177         output[i * 4 + 2] = (s->h[i] >> 8) & 0xFF;
 178         output[i * 4 + 3] = (s->h[i]) & 0xFF;
 179     }
 180 }
 181
 182 void SHA_Simple(void *p, int len, unsigned char *output)
 183 {
 184     SHA_State s;
 185
 186     SHA_Init(&s);
 187     SHA_Bytes(&s, p, len);
 188     SHA_Final(&s, output);
 189 }
 190
 191 /* ----------------------------------------------------------------------
 192  * The above is the SHA-1 algorithm itself. Now we implement the
 193  * HMAC wrapper on it.
 194  */
 195
 196 static SHA_State sha1_cs_mac_s1, sha1_cs_mac_s2;
 197 static SHA_State sha1_sc_mac_s1, sha1_sc_mac_s2;
 198
 199 static void sha1_key(SHA_State * s1, SHA_State * s2,
 200                      unsigned char *key, int len)
 201 {
 202     unsigned char foo[64];
 203     int i;
 204
 205     memset(foo, 0x36, 64);
 206     for (i = 0; i < len && i < 64; i++)
 207         foo[i] ^= key[i];
 208     SHA_Init(s1);
 209     SHA_Bytes(s1, foo, 64);
 210
 211     memset(foo, 0x5C, 64);
 212     for (i = 0; i < len && i < 64; i++)
 213         foo[i] ^= key[i];
 214     SHA_Init(s2);
 215     SHA_Bytes(s2, foo, 64);
 216
 217     memset(foo, 0, 64);                /* burn the evidence */
 218 }
 219
 220 static void sha1_cskey(unsigned char *key)
 221 {
 222     sha1_key(&sha1_cs_mac_s1, &sha1_cs_mac_s2, key, 20);
 223 }
 224
 225 static void sha1_sckey(unsigned char *key)
 226 {
 227     sha1_key(&sha1_sc_mac_s1, &sha1_sc_mac_s2, key, 20);
 228 }
 229
 230 static void sha1_cskey_buggy(unsigned char *key)
 231 {
 232     sha1_key(&sha1_cs_mac_s1, &sha1_cs_mac_s2, key, 16);
 233 }
 234
 235 static void sha1_sckey_buggy(unsigned char *key)
 236 {
 237     sha1_key(&sha1_sc_mac_s1, &sha1_sc_mac_s2, key, 16);
 238 }
 239
 240 static void sha1_do_hmac(SHA_State * s1, SHA_State * s2,
 241                          unsigned char *blk, int len, unsigned long seq,
 242                          unsigned char *hmac)
 243 {
 244     SHA_State s;
 245     unsigned char intermediate[20];
 246
 247     intermediate[0] = (unsigned char) ((seq >> 24) & 0xFF);
 248     intermediate[1] = (unsigned char) ((seq >> 16) & 0xFF);
 249     intermediate[2] = (unsigned char) ((seq >> 8) & 0xFF);
 250     intermediate[3] = (unsigned char) ((seq) & 0xFF);
 251
 252     s = *s1;                           /* structure copy */
 253     SHA_Bytes(&s, intermediate, 4);
 254     SHA_Bytes(&s, blk, len);
 255     SHA_Final(&s, intermediate);
 256     s = *s2;                           /* structure copy */
 257     SHA_Bytes(&s, intermediate, 20);
 258     SHA_Final(&s, hmac);
 259 }
 260
 261 static void sha1_generate(unsigned char *blk, int len, unsigned long seq)
 262 {
 263     sha1_do_hmac(&sha1_cs_mac_s1, &sha1_cs_mac_s2, blk, len, seq,
 264                  blk + len);
 265 }
 266
 267 static int sha1_verify(unsigned char *blk, int len, unsigned long seq)
 268 {
 269     unsigned char correct[20];
 270     sha1_do_hmac(&sha1_sc_mac_s1, &sha1_sc_mac_s2, blk, len, seq, correct);
 271     return !memcmp(correct, blk + len, 20);
 272 }
 273
 274 void hmac_sha1_simple(void *key, int keylen, void *data, int datalen,
 275                       unsigned char *output) {
 276     SHA_State s1, s2;
 277     unsigned char intermediate[20];
 278
 279     sha1_key(&s1, &s2, key, keylen);
 280     SHA_Bytes(&s1, data, datalen);
 281     SHA_Final(&s1, intermediate);
 282
 283     SHA_Bytes(&s2, intermediate, 20);
 284     SHA_Final(&s2, output);
 285 }
 286
 287 const struct ssh_mac ssh_sha1 = {
 288     sha1_cskey, sha1_sckey,
 289     sha1_generate,
 290     sha1_verify,
 291     "hmac-sha1",
 292     20
 293 };
 294
 295 const struct ssh_mac ssh_sha1_buggy = {
 296     sha1_cskey_buggy, sha1_sckey_buggy,
 297     sha1_generate,
 298     sha1_verify,
 299     "hmac-sha1",
 300     20
 301 };