/* * public domain sha256 crypt implementation * * original sha crypt design: http://people.redhat.com/drepper/SHA-crypt.txt * in this implementation at least 32bit int is assumed, * key length is limited, the $5$ prefix is mandatory, '\n' and ':' is rejected * in the salt and rounds= setting must contain a valid iteration count, * on error "*" is returned. */ #include #include #include #include #include /* public domain sha256 implementation based on fips180-3 */ struct sha256 { uint64_t len; /* processed message length */ uint32_t h[8]; /* hash state */ uint8_t buf[64]; /* message block buffer */ }; static uint32_t ror(uint32_t n, int k) { return (n >> k) | (n << (32-k)); } #define Ch(x,y,z) (z ^ (x & (y ^ z))) #define Maj(x,y,z) ((x & y) | (z & (x | y))) #define S0(x) (ror(x,2) ^ ror(x,13) ^ ror(x,22)) #define S1(x) (ror(x,6) ^ ror(x,11) ^ ror(x,25)) #define R0(x) (ror(x,7) ^ ror(x,18) ^ (x>>3)) #define R1(x) (ror(x,17) ^ ror(x,19) ^ (x>>10)) static const uint32_t K[64] = { 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da, 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070, 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2 }; static void processblock(struct sha256 *s, const uint8_t *buf) { uint32_t W[64], t1, t2, a, b, c, d, e, f, g, h; int i; for (i = 0; i < 16; i++) { W[i] = (uint32_t)buf[4*i]<<24; W[i] |= (uint32_t)buf[4*i+1]<<16; W[i] |= (uint32_t)buf[4*i+2]<<8; W[i] |= buf[4*i+3]; } for (; i < 64; i++) W[i] = R1(W[i-2]) + W[i-7] + R0(W[i-15]) + W[i-16]; a = s->h[0]; b = s->h[1]; c = s->h[2]; d = s->h[3]; e = s->h[4]; f = s->h[5]; g = s->h[6]; h = s->h[7]; for (i = 0; i < 64; i++) { t1 = h + S1(e) + Ch(e,f,g) + K[i] + W[i]; t2 = S0(a) + Maj(a,b,c); h = g; g = f; f = e; e = d + t1; d = c; c = b; b = a; a = t1 + t2; } s->h[0] += a; s->h[1] += b; s->h[2] += c; s->h[3] += d; s->h[4] += e; s->h[5] += f; s->h[6] += g; s->h[7] += h; } static void pad(struct sha256 *s) { unsigned r = s->len % 64; s->buf[r++] = 0x80; if (r > 56) { memset(s->buf + r, 0, 64 - r); r = 0; processblock(s, s->buf); } memset(s->buf + r, 0, 56 - r); s->len *= 8; s->buf[56] = s->len >> 56; s->buf[57] = s->len >> 48; s->buf[58] = s->len >> 40; s->buf[59] = s->len >> 32; s->buf[60] = s->len >> 24; s->buf[61] = s->len >> 16; s->buf[62] = s->len >> 8; s->buf[63] = s->len; processblock(s, s->buf); } static void sha256_init(struct sha256 *s) { s->len = 0; s->h[0] = 0x6a09e667; s->h[1] = 0xbb67ae85; s->h[2] = 0x3c6ef372; s->h[3] = 0xa54ff53a; s->h[4] = 0x510e527f; s->h[5] = 0x9b05688c; s->h[6] = 0x1f83d9ab; s->h[7] = 0x5be0cd19; } static void sha256_sum(struct sha256 *s, uint8_t *md) { int i; pad(s); for (i = 0; i < 8; i++) { md[4*i] = s->h[i] >> 24; md[4*i+1] = s->h[i] >> 16; md[4*i+2] = s->h[i] >> 8; md[4*i+3] = s->h[i]; } } static void sha256_update(struct sha256 *s, const void *m, unsigned long len) { const uint8_t *p = m; unsigned r = s->len % 64; s->len += len; if (r) { if (len < 64 - r) { memcpy(s->buf + r, p, len); return; } memcpy(s->buf + r, p, 64 - r); len -= 64 - r; p += 64 - r; processblock(s, s->buf); } for (; len >= 64; len -= 64, p += 64) processblock(s, p); memcpy(s->buf, p, len); } static const unsigned char b64[] = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"; static char *to64(char *s, unsigned int u, int n) { while (--n >= 0) { *s++ = b64[u % 64]; u /= 64; } return s; } /* key limit is not part of the original design, added for DoS protection. * rounds limit has been lowered (versus the reference/spec), also for DoS * protection. runtime is O(klen^2 + klen*rounds) */ #define KEY_MAX 256 #define SALT_MAX 16 #define ROUNDS_DEFAULT 5000 #define ROUNDS_MIN 1000 #define ROUNDS_MAX 9999999 /* hash n bytes of the repeated md message digest */ static void hashmd(struct sha256 *s, unsigned int n, const void *md) { unsigned int i; for (i = n; i > 32; i -= 32) sha256_update(s, md, 32); sha256_update(s, md, i); } static char *sha256crypt(const char *key, const char *setting, char *output) { struct sha256 ctx; unsigned char md[32], kmd[32], smd[32]; unsigned int i, r, klen, slen; char rounds[20] = ""; const char *salt; char *p; /* reject large keys */ klen = strnlen(key, KEY_MAX+1); if (klen > KEY_MAX) return 0; /* setting: $5$rounds=n$salt$ (rounds=n$ and closing $ are optional) */ if (strncmp(setting, "$5$", 3) != 0) return 0; salt = setting + 3; r = ROUNDS_DEFAULT; if (strncmp(salt, "rounds=", sizeof "rounds=" - 1) == 0) { unsigned long u; char *end; /* * this is a deviation from the reference: * bad rounds setting is rejected if it is * - empty * - unterminated (missing '$') * - begins with anything but a decimal digit * the reference implementation treats these bad * rounds as part of the salt or parse them with * strtoul semantics which may cause problems * including non-portable hashes that depend on * the host's value of ULONG_MAX. */ salt += sizeof "rounds=" - 1; if (!isdigit(*salt)) return 0; u = strtoul(salt, &end, 10); if (*end != '$') return 0; salt = end+1; if (u < ROUNDS_MIN) r = ROUNDS_MIN; else if (u > ROUNDS_MAX) return 0; else r = u; /* needed when rounds is zero prefixed or out of bounds */ sprintf(rounds, "rounds=%u$", r); } for (i = 0; i < SALT_MAX && salt[i] && salt[i] != '$'; i++) /* reject characters that interfere with /etc/shadow parsing */ if (salt[i] == '\n' || salt[i] == ':') return 0; slen = i; /* B = sha(key salt key) */ sha256_init(&ctx); sha256_update(&ctx, key, klen); sha256_update(&ctx, salt, slen); sha256_update(&ctx, key, klen); sha256_sum(&ctx, md); /* A = sha(key salt repeat-B alternate-B-key) */ sha256_init(&ctx); sha256_update(&ctx, key, klen); sha256_update(&ctx, salt, slen); hashmd(&ctx, klen, md); for (i = klen; i > 0; i >>= 1) if (i & 1) sha256_update(&ctx, md, sizeof md); else sha256_update(&ctx, key, klen); sha256_sum(&ctx, md); /* DP = sha(repeat-key), this step takes O(klen^2) time */ sha256_init(&ctx); for (i = 0; i < klen; i++) sha256_update(&ctx, key, klen); sha256_sum(&ctx, kmd); /* DS = sha(repeat-salt) */ sha256_init(&ctx); for (i = 0; i < 16 + md[0]; i++) sha256_update(&ctx, salt, slen); sha256_sum(&ctx, smd); /* iterate A = f(A,DP,DS), this step takes O(rounds*klen) time */ for (i = 0; i < r; i++) { sha256_init(&ctx); if (i % 2) hashmd(&ctx, klen, kmd); else sha256_update(&ctx, md, sizeof md); if (i % 3) sha256_update(&ctx, smd, slen); if (i % 7) hashmd(&ctx, klen, kmd); if (i % 2) sha256_update(&ctx, md, sizeof md); else hashmd(&ctx, klen, kmd); sha256_sum(&ctx, md); } /* output is $5$rounds=n$salt$hash */ p = output; p += sprintf(p, "$5$%s%.*s$", rounds, slen, salt); static const unsigned char perm[][3] = { 0,10,20,21,1,11,12,22,2,3,13,23,24,4,14, 15,25,5,6,16,26,27,7,17,18,28,8,9,19,29 }; for (i=0; i<10; i++) p = to64(p, (md[perm[i][0]]<<16)|(md[perm[i][1]]<<8)|md[perm[i][2]], 4); p = to64(p, (md[31]<<8)|md[30], 3); *p = 0; return output; } char *__crypt_sha256(const char *key, const char *setting, char *output) { static const char testkey[] = "Xy01@#\x01\x02\x80\x7f\xff\r\n\x81\t !"; static const char testsetting[] = "$5$rounds=1234$abc0123456789$"; static const char testhash[] = "$5$rounds=1234$abc0123456789$3VfDjPt05VHFn47C/ojFZ6KRPYrOjj1lLbH.dkF3bZ6"; char testbuf[128]; char *p, *q; p = sha256crypt(key, setting, output); /* self test and stack cleanup */ q = sha256crypt(testkey, testsetting, testbuf); if (!p || q != testbuf || memcmp(testbuf, testhash, sizeof testhash)) return "*"; return p; }