LXR busybox/libbb/pw_encrypt

   1/* SHA256 and SHA512-based Unix crypt implementation.
   2 * Released into the Public Domain by Ulrich Drepper <drepper@redhat.com>.
   3 */
   4
   5/* Prefix for optional rounds specification.  */
   6static const char str_rounds[] ALIGN1 = "rounds=%u$";
   7
   8/* Maximum salt string length.  */
   9#define SALT_LEN_MAX 16
  10/* Default number of rounds if not explicitly specified.  */
  11#define ROUNDS_DEFAULT 5000
  12/* Minimum number of rounds.  */
  13#define ROUNDS_MIN 1000
  14/* Maximum number of rounds.  */
  15#define ROUNDS_MAX 999999999
  16
  17static char *
  18NOINLINE
  19sha_crypt(/*const*/ char *key_data, /*const*/ char *salt_data)
  20{
  21#undef sha_end
  22        void (*sha_begin)(void *ctx) FAST_FUNC;
  23        void (*sha_hash)(void *ctx, const void *buffer, size_t len) FAST_FUNC;
  24        unsigned (*sha_end)(void *ctx, void *resbuf) FAST_FUNC;
  25        int _32or64;
  26
  27        char *result, *resptr;
  28
  29        /* btw, sha256 needs [32] and uint32_t only */
  30        struct {
  31                unsigned char alt_result[64];
  32                unsigned char temp_result[64];
  33                union {
  34                        sha256_ctx_t x;
  35                        sha512_ctx_t y;
  36                } ctx;
  37                union {
  38                        sha256_ctx_t x;
  39                        sha512_ctx_t y;
  40                } alt_ctx;
  41        } L __attribute__((__aligned__(__alignof__(uint64_t))));
  42#define alt_result  (L.alt_result )
  43#define temp_result (L.temp_result)
  44#define ctx         (L.ctx        )
  45#define alt_ctx     (L.alt_ctx    )
  46        unsigned salt_len;
  47        unsigned key_len;
  48        unsigned cnt;
  49        unsigned rounds;
  50        char *cp;
  51
  52        /* Analyze salt, construct already known part of result */
  53        cnt = strlen(salt_data) + 1 + 43 + 1;
  54        _32or64 = 32;
  55        if (salt_data[1] == '6') { /* sha512 */
  56                _32or64 *= 2; /*64*/
  57                cnt += 43;
  58        }
  59        result = resptr = xzalloc(cnt); /* will provide NUL terminator */
  60        *resptr++ = '$';
  61        *resptr++ = salt_data[1];
  62        *resptr++ = '$';
  63        rounds = ROUNDS_DEFAULT;
  64        salt_data += 3;
  65        if (strncmp(salt_data, str_rounds, 7) == 0) {
  66                /* 7 == strlen("rounds=") */
  67                char *endp;
  68                cnt = bb_strtou(salt_data + 7, &endp, 10);
  69                if (*endp == '$') {
  70                        salt_data = endp + 1;
  71                        rounds = cnt;
  72                        if (rounds < ROUNDS_MIN)
  73                                rounds = ROUNDS_MIN;
  74                        if (rounds > ROUNDS_MAX)
  75                                rounds = ROUNDS_MAX;
  76                        /* add "rounds=NNNNN$" to result */
  77                        resptr += sprintf(resptr, str_rounds, rounds);
  78                }
  79        }
  80        salt_len = strchrnul(salt_data, '$') - salt_data;
  81        if (salt_len > SALT_LEN_MAX)
  82                salt_len = SALT_LEN_MAX;
  83        /* xstrdup assures suitable alignment; also we will use it
  84           as a scratch space later. */
  85        salt_data = xstrndup(salt_data, salt_len);
  86        /* add "salt$" to result */
  87        strcpy(resptr, salt_data);
  88        resptr += salt_len;
  89        *resptr++ = '$';
  90        /* key data doesn't need much processing */
  91        key_len = strlen(key_data);
  92        key_data = xstrdup(key_data);
  93
  94        /* Which flavor of SHAnnn ops to use? */
  95        sha_begin = (void*)sha256_begin;
  96        sha_hash = (void*)sha256_hash;
  97        sha_end = (void*)sha256_end;
  98        if (_32or64 != 32) {
  99                sha_begin = (void*)sha512_begin;
 100                sha_hash = (void*)sha512_hash;
 101                sha_end = (void*)sha512_end;
 102        }
 103
 104        /* Add KEY, SALT.  */
 105        sha_begin(&ctx);
 106        sha_hash(&ctx, key_data, key_len);
 107        sha_hash(&ctx, salt_data, salt_len);
 108
 109        /* Compute alternate SHA sum with input KEY, SALT, and KEY.
 110           The final result will be added to the first context.  */
 111        sha_begin(&alt_ctx);
 112        sha_hash(&alt_ctx, key_data, key_len);
 113        sha_hash(&alt_ctx, salt_data, salt_len);
 114        sha_hash(&alt_ctx, key_data, key_len);
 115        sha_end(&alt_ctx, alt_result);
 116
 117        /* Add result of this to the other context.  */
 118        /* Add for any character in the key one byte of the alternate sum.  */
 119        for (cnt = key_len; cnt > _32or64; cnt -= _32or64)
 120                sha_hash(&ctx, alt_result, _32or64);
 121        sha_hash(&ctx, alt_result, cnt);
 122
 123        /* Take the binary representation of the length of the key and for every
 124           1 add the alternate sum, for every 0 the key.  */
 125        for (cnt = key_len; cnt != 0; cnt >>= 1)
 126                if ((cnt & 1) != 0)
 127                        sha_hash(&ctx, alt_result, _32or64);
 128                else
 129                        sha_hash(&ctx, key_data, key_len);
 130
 131        /* Create intermediate result.  */
 132        sha_end(&ctx, alt_result);
 133
 134        /* Start computation of P byte sequence.  */
 135        /* For every character in the password add the entire password.  */
 136        sha_begin(&alt_ctx);
 137        for (cnt = 0; cnt < key_len; ++cnt)
 138                sha_hash(&alt_ctx, key_data, key_len);
 139        sha_end(&alt_ctx, temp_result);
 140
 141        /* NB: past this point, raw key_data is not used anymore */
 142
 143        /* Create byte sequence P.  */
 144#define p_bytes key_data /* reuse the buffer as it is of the key_len size */
 145        cp = p_bytes; /* was: ... = alloca(key_len); */
 146        for (cnt = key_len; cnt >= _32or64; cnt -= _32or64) {
 147                cp = memcpy(cp, temp_result, _32or64);
 148                cp += _32or64;
 149        }
 150        memcpy(cp, temp_result, cnt);
 151
 152        /* Start computation of S byte sequence.  */
 153        /* For every character in the password add the entire password.  */
 154        sha_begin(&alt_ctx);
 155        for (cnt = 0; cnt < 16 + alt_result[0]; ++cnt)
 156                sha_hash(&alt_ctx, salt_data, salt_len);
 157        sha_end(&alt_ctx, temp_result);
 158
 159        /* NB: past this point, raw salt_data is not used anymore */
 160
 161        /* Create byte sequence S.  */
 162#define s_bytes salt_data /* reuse the buffer as it is of the salt_len size */
 163        cp = s_bytes; /* was: ... = alloca(salt_len); */
 164        for (cnt = salt_len; cnt >= _32or64; cnt -= _32or64) {
 165                cp = memcpy(cp, temp_result, _32or64);
 166                cp += _32or64;
 167        }
 168        memcpy(cp, temp_result, cnt);
 169
 170        /* Repeatedly run the collected hash value through SHA to burn
 171           CPU cycles.  */
 172        for (cnt = 0; cnt < rounds; ++cnt) {
 173                sha_begin(&ctx);
 174
 175                /* Add key or last result.  */
 176                if ((cnt & 1) != 0)
 177                        sha_hash(&ctx, p_bytes, key_len);
 178                else
 179                        sha_hash(&ctx, alt_result, _32or64);
 180                /* Add salt for numbers not divisible by 3.  */
 181                if (cnt % 3 != 0)
 182                        sha_hash(&ctx, s_bytes, salt_len);
 183                /* Add key for numbers not divisible by 7.  */
 184                if (cnt % 7 != 0)
 185                        sha_hash(&ctx, p_bytes, key_len);
 186                /* Add key or last result.  */
 187                if ((cnt & 1) != 0)
 188                        sha_hash(&ctx, alt_result, _32or64);
 189                else
 190                        sha_hash(&ctx, p_bytes, key_len);
 191
 192                sha_end(&ctx, alt_result);
 193        }
 194
 195        /* Append encrypted password to result buffer */
 196//TODO: replace with something like
 197//      bb_uuencode(cp, src, length, bb_uuenc_tbl_XXXbase64);
 198#define b64_from_24bit(B2, B1, B0, N) \
 199do { \
 200        unsigned w = ((B2) << 16) | ((B1) << 8) | (B0); \
 201        resptr = to64(resptr, w, N); \
 202} while (0)
 203        if (_32or64 == 32) { /* sha256 */
 204                unsigned i = 0;
 205                while (1) {
 206                        unsigned j = i + 10;
 207                        unsigned k = i + 20;
 208                        if (j >= 30) j -= 30;
 209                        if (k >= 30) k -= 30;
 210                        b64_from_24bit(alt_result[i], alt_result[j], alt_result[k], 4);
 211                        if (k == 29)
 212                                break;
 213                        i = k + 1;
 214                }
 215                b64_from_24bit(0, alt_result[31], alt_result[30], 3);
 216                /* was:
 217                b64_from_24bit(alt_result[0], alt_result[10], alt_result[20], 4);
 218                b64_from_24bit(alt_result[21], alt_result[1], alt_result[11], 4);
 219                b64_from_24bit(alt_result[12], alt_result[22], alt_result[2], 4);
 220                b64_from_24bit(alt_result[3], alt_result[13], alt_result[23], 4);
 221                b64_from_24bit(alt_result[24], alt_result[4], alt_result[14], 4);
 222                b64_from_24bit(alt_result[15], alt_result[25], alt_result[5], 4);
 223                b64_from_24bit(alt_result[6], alt_result[16], alt_result[26], 4);
 224                b64_from_24bit(alt_result[27], alt_result[7], alt_result[17], 4);
 225                b64_from_24bit(alt_result[18], alt_result[28], alt_result[8], 4);
 226                b64_from_24bit(alt_result[9], alt_result[19], alt_result[29], 4);
 227                b64_from_24bit(0, alt_result[31], alt_result[30], 3);
 228                */
 229        } else {
 230                unsigned i = 0;
 231                while (1) {
 232                        unsigned j = i + 21;
 233                        unsigned k = i + 42;
 234                        if (j >= 63) j -= 63;
 235                        if (k >= 63) k -= 63;
 236                        b64_from_24bit(alt_result[i], alt_result[j], alt_result[k], 4);
 237                        if (j == 20)
 238                                break;
 239                        i = j + 1;
 240                }
 241                b64_from_24bit(0, 0, alt_result[63], 2);
 242                /* was:
 243                b64_from_24bit(alt_result[0], alt_result[21], alt_result[42], 4);
 244                b64_from_24bit(alt_result[22], alt_result[43], alt_result[1], 4);
 245                b64_from_24bit(alt_result[44], alt_result[2], alt_result[23], 4);
 246                b64_from_24bit(alt_result[3], alt_result[24], alt_result[45], 4);
 247                b64_from_24bit(alt_result[25], alt_result[46], alt_result[4], 4);
 248                b64_from_24bit(alt_result[47], alt_result[5], alt_result[26], 4);
 249                b64_from_24bit(alt_result[6], alt_result[27], alt_result[48], 4);
 250                b64_from_24bit(alt_result[28], alt_result[49], alt_result[7], 4);
 251                b64_from_24bit(alt_result[50], alt_result[8], alt_result[29], 4);
 252                b64_from_24bit(alt_result[9], alt_result[30], alt_result[51], 4);
 253                b64_from_24bit(alt_result[31], alt_result[52], alt_result[10], 4);
 254                b64_from_24bit(alt_result[53], alt_result[11], alt_result[32], 4);
 255                b64_from_24bit(alt_result[12], alt_result[33], alt_result[54], 4);
 256                b64_from_24bit(alt_result[34], alt_result[55], alt_result[13], 4);
 257                b64_from_24bit(alt_result[56], alt_result[14], alt_result[35], 4);
 258                b64_from_24bit(alt_result[15], alt_result[36], alt_result[57], 4);
 259                b64_from_24bit(alt_result[37], alt_result[58], alt_result[16], 4);
 260                b64_from_24bit(alt_result[59], alt_result[17], alt_result[38], 4);
 261                b64_from_24bit(alt_result[18], alt_result[39], alt_result[60], 4);
 262                b64_from_24bit(alt_result[40], alt_result[61], alt_result[19], 4);
 263                b64_from_24bit(alt_result[62], alt_result[20], alt_result[41], 4);
 264                b64_from_24bit(0, 0, alt_result[63], 2);
 265                */
 266        }
 267        /* *resptr = '\0'; - xzalloc did it */
 268#undef b64_from_24bit
 269
 270        /* Clear the buffer for the intermediate result so that people
 271           attaching to processes or reading core dumps cannot get any
 272           information.  */
 273        memset(&L, 0, sizeof(L)); /* [alt]_ctx and XXX_result buffers */
 274        memset(key_data, 0, key_len); /* also p_bytes */
 275        memset(salt_data, 0, salt_len); /* also s_bytes */
 276        free(key_data);
 277        free(salt_data);
 278#undef p_bytes
 279#undef s_bytes
 280
 281        return result;
 282#undef alt_result
 283#undef temp_result
 284#undef ctx
 285#undef alt_ctx
 286}
 287