/*
* 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 <ctype.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
/* 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)
r = ROUNDS_MAX;
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;
}
