[398] | 1 | /*
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| 2 | * public domain sha256 crypt implementation
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| 3 | *
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| 4 | * original sha crypt design: http://people.redhat.com/drepper/SHA-crypt.txt
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| 5 | * in this implementation at least 32bit int is assumed,
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| 6 | * key length is limited, the $5$ prefix is mandatory, '\n' and ':' is rejected
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| 7 | * in the salt and rounds= setting must contain a valid iteration count,
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| 8 | * on error "*" is returned.
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| 9 | */
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| 10 | #include <ctype.h>
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| 11 | #include <stdlib.h>
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| 12 | #include <stdio.h>
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| 13 | #include <string.h>
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| 14 | #include <stdint.h>
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| 15 |
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| 16 | /* public domain sha256 implementation based on fips180-3 */
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| 17 |
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| 18 | struct sha256 {
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| 19 | uint64_t len; /* processed message length */
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| 20 | uint32_t h[8]; /* hash state */
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| 21 | uint8_t buf[64]; /* message block buffer */
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| 22 | };
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| 23 |
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| 24 | static uint32_t ror(uint32_t n, int k) { return (n >> k) | (n << (32-k)); }
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| 25 | #define Ch(x,y,z) (z ^ (x & (y ^ z)))
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| 26 | #define Maj(x,y,z) ((x & y) | (z & (x | y)))
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| 27 | #define S0(x) (ror(x,2) ^ ror(x,13) ^ ror(x,22))
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| 28 | #define S1(x) (ror(x,6) ^ ror(x,11) ^ ror(x,25))
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| 29 | #define R0(x) (ror(x,7) ^ ror(x,18) ^ (x>>3))
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| 30 | #define R1(x) (ror(x,17) ^ ror(x,19) ^ (x>>10))
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| 31 |
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| 32 | static const uint32_t K[64] = {
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| 33 | 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
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| 34 | 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
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| 35 | 0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
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| 36 | 0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
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| 37 | 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
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| 38 | 0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
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| 39 | 0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
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| 40 | 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
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| 41 | };
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| 42 |
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| 43 | static void processblock(struct sha256 *s, const uint8_t *buf)
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| 44 | {
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| 45 | uint32_t W[64], t1, t2, a, b, c, d, e, f, g, h;
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| 46 | int i;
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| 47 |
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| 48 | for (i = 0; i < 16; i++) {
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| 49 | W[i] = (uint32_t)buf[4*i]<<24;
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| 50 | W[i] |= (uint32_t)buf[4*i+1]<<16;
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| 51 | W[i] |= (uint32_t)buf[4*i+2]<<8;
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| 52 | W[i] |= buf[4*i+3];
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| 53 | }
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| 54 | for (; i < 64; i++)
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| 55 | W[i] = R1(W[i-2]) + W[i-7] + R0(W[i-15]) + W[i-16];
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| 56 | a = s->h[0];
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| 57 | b = s->h[1];
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| 58 | c = s->h[2];
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| 59 | d = s->h[3];
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| 60 | e = s->h[4];
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| 61 | f = s->h[5];
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| 62 | g = s->h[6];
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| 63 | h = s->h[7];
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| 64 | for (i = 0; i < 64; i++) {
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| 65 | t1 = h + S1(e) + Ch(e,f,g) + K[i] + W[i];
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| 66 | t2 = S0(a) + Maj(a,b,c);
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| 67 | h = g;
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| 68 | g = f;
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| 69 | f = e;
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| 70 | e = d + t1;
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| 71 | d = c;
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| 72 | c = b;
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| 73 | b = a;
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| 74 | a = t1 + t2;
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| 75 | }
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| 76 | s->h[0] += a;
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| 77 | s->h[1] += b;
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| 78 | s->h[2] += c;
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| 79 | s->h[3] += d;
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| 80 | s->h[4] += e;
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| 81 | s->h[5] += f;
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| 82 | s->h[6] += g;
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| 83 | s->h[7] += h;
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| 84 | }
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| 85 |
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| 86 | static void pad(struct sha256 *s)
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| 87 | {
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| 88 | unsigned r = s->len % 64;
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| 89 |
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| 90 | s->buf[r++] = 0x80;
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| 91 | if (r > 56) {
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| 92 | memset(s->buf + r, 0, 64 - r);
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| 93 | r = 0;
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| 94 | processblock(s, s->buf);
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| 95 | }
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| 96 | memset(s->buf + r, 0, 56 - r);
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| 97 | s->len *= 8;
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| 98 | s->buf[56] = s->len >> 56;
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| 99 | s->buf[57] = s->len >> 48;
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| 100 | s->buf[58] = s->len >> 40;
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| 101 | s->buf[59] = s->len >> 32;
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| 102 | s->buf[60] = s->len >> 24;
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| 103 | s->buf[61] = s->len >> 16;
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| 104 | s->buf[62] = s->len >> 8;
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| 105 | s->buf[63] = s->len;
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| 106 | processblock(s, s->buf);
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| 107 | }
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| 108 |
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| 109 | static void sha256_init(struct sha256 *s)
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| 110 | {
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| 111 | s->len = 0;
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| 112 | s->h[0] = 0x6a09e667;
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| 113 | s->h[1] = 0xbb67ae85;
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| 114 | s->h[2] = 0x3c6ef372;
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| 115 | s->h[3] = 0xa54ff53a;
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| 116 | s->h[4] = 0x510e527f;
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| 117 | s->h[5] = 0x9b05688c;
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| 118 | s->h[6] = 0x1f83d9ab;
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| 119 | s->h[7] = 0x5be0cd19;
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| 120 | }
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| 121 |
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| 122 | static void sha256_sum(struct sha256 *s, uint8_t *md)
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| 123 | {
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| 124 | int i;
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| 125 |
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| 126 | pad(s);
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| 127 | for (i = 0; i < 8; i++) {
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| 128 | md[4*i] = s->h[i] >> 24;
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| 129 | md[4*i+1] = s->h[i] >> 16;
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| 130 | md[4*i+2] = s->h[i] >> 8;
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| 131 | md[4*i+3] = s->h[i];
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| 132 | }
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| 133 | }
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| 134 |
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| 135 | static void sha256_update(struct sha256 *s, const void *m, unsigned long len)
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| 136 | {
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| 137 | const uint8_t *p = m;
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| 138 | unsigned r = s->len % 64;
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| 139 |
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| 140 | s->len += len;
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| 141 | if (r) {
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| 142 | if (len < 64 - r) {
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| 143 | memcpy(s->buf + r, p, len);
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| 144 | return;
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| 145 | }
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| 146 | memcpy(s->buf + r, p, 64 - r);
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| 147 | len -= 64 - r;
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| 148 | p += 64 - r;
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| 149 | processblock(s, s->buf);
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| 150 | }
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| 151 | for (; len >= 64; len -= 64, p += 64)
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| 152 | processblock(s, p);
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| 153 | memcpy(s->buf, p, len);
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| 154 | }
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| 155 |
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| 156 | static const unsigned char b64[] =
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| 157 | "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
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| 158 |
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| 159 | static char *to64(char *s, unsigned int u, int n)
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| 160 | {
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| 161 | while (--n >= 0) {
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| 162 | *s++ = b64[u % 64];
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| 163 | u /= 64;
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| 164 | }
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| 165 | return s;
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| 166 | }
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| 167 |
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| 168 | /* key limit is not part of the original design, added for DoS protection.
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| 169 | * rounds limit has been lowered (versus the reference/spec), also for DoS
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| 170 | * protection. runtime is O(klen^2 + klen*rounds) */
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| 171 | #define KEY_MAX 256
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| 172 | #define SALT_MAX 16
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| 173 | #define ROUNDS_DEFAULT 5000
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| 174 | #define ROUNDS_MIN 1000
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| 175 | #define ROUNDS_MAX 9999999
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| 176 |
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| 177 | /* hash n bytes of the repeated md message digest */
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| 178 | static void hashmd(struct sha256 *s, unsigned int n, const void *md)
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| 179 | {
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| 180 | unsigned int i;
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| 181 |
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| 182 | for (i = n; i > 32; i -= 32)
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| 183 | sha256_update(s, md, 32);
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| 184 | sha256_update(s, md, i);
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| 185 | }
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| 186 |
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| 187 | static char *sha256crypt(const char *key, const char *setting, char *output)
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| 188 | {
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| 189 | struct sha256 ctx;
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| 190 | unsigned char md[32], kmd[32], smd[32];
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| 191 | unsigned int i, r, klen, slen;
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| 192 | char rounds[20] = "";
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| 193 | const char *salt;
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| 194 | char *p;
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| 195 |
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| 196 | /* reject large keys */
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| 197 | klen = strnlen(key, KEY_MAX+1);
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| 198 | if (klen > KEY_MAX)
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| 199 | return 0;
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| 200 |
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| 201 | /* setting: $5$rounds=n$salt$ (rounds=n$ and closing $ are optional) */
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| 202 | if (strncmp(setting, "$5$", 3) != 0)
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| 203 | return 0;
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| 204 | salt = setting + 3;
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| 205 |
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| 206 | r = ROUNDS_DEFAULT;
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| 207 | if (strncmp(salt, "rounds=", sizeof "rounds=" - 1) == 0) {
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| 208 | unsigned long u;
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| 209 | char *end;
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| 210 |
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| 211 | /*
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| 212 | * this is a deviation from the reference:
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| 213 | * bad rounds setting is rejected if it is
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| 214 | * - empty
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| 215 | * - unterminated (missing '$')
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| 216 | * - begins with anything but a decimal digit
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| 217 | * the reference implementation treats these bad
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| 218 | * rounds as part of the salt or parse them with
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| 219 | * strtoul semantics which may cause problems
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| 220 | * including non-portable hashes that depend on
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| 221 | * the host's value of ULONG_MAX.
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| 222 | */
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| 223 | salt += sizeof "rounds=" - 1;
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| 224 | if (!isdigit(*salt))
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| 225 | return 0;
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| 226 | u = strtoul(salt, &end, 10);
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| 227 | if (*end != '$')
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| 228 | return 0;
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| 229 | salt = end+1;
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| 230 | if (u < ROUNDS_MIN)
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| 231 | r = ROUNDS_MIN;
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| 232 | else if (u > ROUNDS_MAX)
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| 233 | return 0;
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| 234 | else
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| 235 | r = u;
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| 236 | /* needed when rounds is zero prefixed or out of bounds */
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| 237 | sprintf(rounds, "rounds=%u$", r);
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| 238 | }
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| 239 |
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| 240 | for (i = 0; i < SALT_MAX && salt[i] && salt[i] != '$'; i++)
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| 241 | /* reject characters that interfere with /etc/shadow parsing */
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| 242 | if (salt[i] == '\n' || salt[i] == ':')
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| 243 | return 0;
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| 244 | slen = i;
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| 245 |
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| 246 | /* B = sha(key salt key) */
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| 247 | sha256_init(&ctx);
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| 248 | sha256_update(&ctx, key, klen);
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| 249 | sha256_update(&ctx, salt, slen);
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| 250 | sha256_update(&ctx, key, klen);
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| 251 | sha256_sum(&ctx, md);
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| 252 |
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| 253 | /* A = sha(key salt repeat-B alternate-B-key) */
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| 254 | sha256_init(&ctx);
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| 255 | sha256_update(&ctx, key, klen);
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| 256 | sha256_update(&ctx, salt, slen);
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| 257 | hashmd(&ctx, klen, md);
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| 258 | for (i = klen; i > 0; i >>= 1)
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| 259 | if (i & 1)
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| 260 | sha256_update(&ctx, md, sizeof md);
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| 261 | else
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| 262 | sha256_update(&ctx, key, klen);
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| 263 | sha256_sum(&ctx, md);
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| 264 |
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| 265 | /* DP = sha(repeat-key), this step takes O(klen^2) time */
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| 266 | sha256_init(&ctx);
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| 267 | for (i = 0; i < klen; i++)
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| 268 | sha256_update(&ctx, key, klen);
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| 269 | sha256_sum(&ctx, kmd);
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| 270 |
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| 271 | /* DS = sha(repeat-salt) */
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| 272 | sha256_init(&ctx);
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| 273 | for (i = 0; i < 16 + md[0]; i++)
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| 274 | sha256_update(&ctx, salt, slen);
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| 275 | sha256_sum(&ctx, smd);
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| 276 |
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| 277 | /* iterate A = f(A,DP,DS), this step takes O(rounds*klen) time */
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| 278 | for (i = 0; i < r; i++) {
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| 279 | sha256_init(&ctx);
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| 280 | if (i % 2)
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| 281 | hashmd(&ctx, klen, kmd);
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| 282 | else
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| 283 | sha256_update(&ctx, md, sizeof md);
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| 284 | if (i % 3)
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| 285 | sha256_update(&ctx, smd, slen);
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| 286 | if (i % 7)
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| 287 | hashmd(&ctx, klen, kmd);
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| 288 | if (i % 2)
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| 289 | sha256_update(&ctx, md, sizeof md);
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| 290 | else
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| 291 | hashmd(&ctx, klen, kmd);
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| 292 | sha256_sum(&ctx, md);
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| 293 | }
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| 294 |
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| 295 | /* output is $5$rounds=n$salt$hash */
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| 296 | p = output;
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| 297 | p += sprintf(p, "$5$%s%.*s$", rounds, slen, salt);
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| 298 | static const unsigned char perm[][3] = {
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| 299 | 0,10,20,21,1,11,12,22,2,3,13,23,24,4,14,
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| 300 | 15,25,5,6,16,26,27,7,17,18,28,8,9,19,29 };
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| 301 | for (i=0; i<10; i++) p = to64(p,
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| 302 | (md[perm[i][0]]<<16)|(md[perm[i][1]]<<8)|md[perm[i][2]], 4);
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| 303 | p = to64(p, (md[31]<<8)|md[30], 3);
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| 304 | *p = 0;
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| 305 | return output;
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| 306 | }
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| 307 |
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| 308 | char *__crypt_sha256(const char *key, const char *setting, char *output)
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| 309 | {
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| 310 | static const char testkey[] = "Xy01@#\x01\x02\x80\x7f\xff\r\n\x81\t !";
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| 311 | static const char testsetting[] = "$5$rounds=1234$abc0123456789$";
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| 312 | static const char testhash[] = "$5$rounds=1234$abc0123456789$3VfDjPt05VHFn47C/ojFZ6KRPYrOjj1lLbH.dkF3bZ6";
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| 313 | char testbuf[128];
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| 314 | char *p, *q;
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| 315 |
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| 316 | p = sha256crypt(key, setting, output);
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| 317 | /* self test and stack cleanup */
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| 318 | q = sha256crypt(testkey, testsetting, testbuf);
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| 319 | if (!p || q != testbuf || memcmp(testbuf, testhash, sizeof testhash))
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| 320 | return "*";
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| 321 | return p;
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| 322 | }
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