/*
* SHA1 hash algorithm. Used in SSH2 as a MAC, and the transform is
* also used as a `stirring' function for the PuTTY random number
* pool. Implemented directly from the specification by Simon
* Tatham.
*/
#include "ssh.h"
/* ----------------------------------------------------------------------
* Core SHA algorithm: processes 16-word blocks into a message digest.
*/
#define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) )
void SHA_Core_Init(uint32 h[5]) {
h[0] = 0x67452301;
h[1] = 0xefcdab89;
h[2] = 0x98badcfe;
h[3] = 0x10325476;
h[4] = 0xc3d2e1f0;
}
void SHATransform(word32 *digest, word32 *block) {
word32 w[80];
word32 a,b,c,d,e;
int t;
for (t = 0; t < 16; t++)
w[t] = block[t];
for (t = 16; t < 80; t++) {
word32 tmp = w[t-3] ^ w[t-8] ^ w[t-14] ^ w[t-16];
w[t] = rol(tmp, 1);
}
a = digest[0];
b = digest[1];
c = digest[2];
d = digest[3];
e = digest[4];
for (t = 0; t < 20; t++) {
word32 tmp = rol(a, 5) + ( (b&c) | (d&~b) ) + e + w[t] + 0x5a827999;
e = d; d = c; c = rol(b, 30); b = a; a = tmp;
}
for (t = 20; t < 40; t++) {
word32 tmp = rol(a, 5) + (b^c^d) + e + w[t] + 0x6ed9eba1;
e = d; d = c; c = rol(b, 30); b = a; a = tmp;
}
for (t = 40; t < 60; t++) {
word32 tmp = rol(a, 5) + ( (b&c) | (b&d) | (c&d) ) + e + w[t] + 0x8f1bbcdc;
e = d; d = c; c = rol(b, 30); b = a; a = tmp;
}
for (t = 60; t < 80; t++) {
word32 tmp = rol(a, 5) + (b^c^d) + e + w[t] + 0xca62c1d6;
e = d; d = c; c = rol(b, 30); b = a; a = tmp;
}
digest[0] += a;
digest[1] += b;
digest[2] += c;
digest[3] += d;
digest[4] += e;
}
/* ----------------------------------------------------------------------
* Outer SHA algorithm: take an arbitrary length byte string,
* convert it into 16-word blocks with the prescribed padding at
* the end, and pass those blocks to the core SHA algorithm.
*/
void SHA_Init(SHA_State *s) {
SHA_Core_Init(s->h);
s->blkused = 0;
s->lenhi = s->lenlo = 0;
}
void SHA_Bytes(SHA_State *s, void *p, int len) {
unsigned char *q = (unsigned char *)p;
uint32 wordblock[16];
uint32 lenw = len;
int i;
/*
* Update the length field.
*/
s->lenlo += lenw;
s->lenhi += (s->lenlo < lenw);
if (s->blkused && s->blkused+len < 64) {
/*
* Trivial case: just add to the block.
*/
memcpy(s->block + s->blkused, q, len);
s->blkused += len;
} else {
/*
* We must complete and process at least one block.
*/
while (s->blkused + len >= 64) {
memcpy(s->block + s->blkused, q, 64 - s->blkused);
q += 64 - s->blkused;
len -= 64 - s->blkused;
/* Now process the block. Gather bytes big-endian into words */
for (i = 0; i < 16; i++) {
wordblock[i] =
( ((uint32)s->block[i*4+0]) << 24 ) |
( ((uint32)s->block[i*4+1]) << 16 ) |
( ((uint32)s->block[i*4+2]) << 8 ) |
( ((uint32)s->block[i*4+3]) << 0 );
}
SHATransform(s->h, wordblock);
s->blkused = 0;
}
memcpy(s->block, q, len);
s->blkused = len;
}
}
void SHA_Final(SHA_State *s, unsigned char *output) {
int i;
int pad;
unsigned char c[64];
uint32 lenhi, lenlo;
if (s->blkused >= 56)
pad = 56 + 64 - s->blkused;
else
pad = 56 - s->blkused;
lenhi = (s->lenhi << 3) | (s->lenlo >> (32-3));
lenlo = (s->lenlo << 3);
memset(c, 0, pad);
c[0] = 0x80;
SHA_Bytes(s, &c, pad);
c[0] = (lenhi >> 24) & 0xFF;
c[1] = (lenhi >> 16) & 0xFF;
c[2] = (lenhi >> 8) & 0xFF;
c[3] = (lenhi >> 0) & 0xFF;
c[4] = (lenlo >> 24) & 0xFF;
c[5] = (lenlo >> 16) & 0xFF;
c[6] = (lenlo >> 8) & 0xFF;
c[7] = (lenlo >> 0) & 0xFF;
SHA_Bytes(s, &c, 8);
for (i = 0; i < 5; i++) {
output[i*4 ] = (s->h[i] >> 24) & 0xFF;
output[i*4+1] = (s->h[i] >> 16) & 0xFF;
output[i*4+2] = (s->h[i] >> 8) & 0xFF;
output[i*4+3] = (s->h[i] ) & 0xFF;
}
}
void SHA_Simple(void *p, int len, unsigned char *output) {
SHA_State s;
SHA_Init(&s);
SHA_Bytes(&s, p, len);
SHA_Final(&s, output);
}
/* ----------------------------------------------------------------------
* The above is the SHA-1 algorithm itself. Now we implement the
* HMAC wrapper on it.
*/
static SHA_State sha1_cs_mac_s1, sha1_cs_mac_s2;
static SHA_State sha1_sc_mac_s1, sha1_sc_mac_s2;
static void sha1_key(SHA_State *s1, SHA_State *s2,
unsigned char *key, int len) {
unsigned char foo[64];
int i;
memset(foo, 0x36, 64);
for (i = 0; i < len && i < 64; i++)
foo[i] ^= key[i];
SHA_Init(s1);
SHA_Bytes(s1, foo, 64);
memset(foo, 0x5C, 64);
for (i = 0; i < len && i < 64; i++)
foo[i] ^= key[i];
SHA_Init(s2);
SHA_Bytes(s2, foo, 64);
memset(foo, 0, 64); /* burn the evidence */
}
static void sha1_cskey(unsigned char *key) {
sha1_key(&sha1_cs_mac_s1, &sha1_cs_mac_s2, key, 20);
}
static void sha1_sckey(unsigned char *key) {
sha1_key(&sha1_sc_mac_s1, &sha1_sc_mac_s2, key, 20);
}
static void sha1_do_hmac(SHA_State *s1, SHA_State *s2,
unsigned char *blk, int len, unsigned long seq,
unsigned char *hmac) {
SHA_State s;
unsigned char intermediate[20];
intermediate[0] = (unsigned char)((seq >> 24) & 0xFF);
intermediate[1] = (unsigned char)((seq >> 16) & 0xFF);
intermediate[2] = (unsigned char)((seq >> 8) & 0xFF);
intermediate[3] = (unsigned char)((seq ) & 0xFF);
s = *s1; /* structure copy */
SHA_Bytes(&s, intermediate, 4);
SHA_Bytes(&s, blk, len);
SHA_Final(&s, intermediate);
s = *s2; /* structure copy */
SHA_Bytes(&s, intermediate, 20);
SHA_Final(&s, hmac);
}
static void sha1_generate(unsigned char *blk, int len, unsigned long seq) {
sha1_do_hmac(&sha1_cs_mac_s1, &sha1_cs_mac_s2, blk, len, seq, blk+len);
}
static int sha1_verify(unsigned char *blk, int len, unsigned long seq) {
unsigned char correct[20];
sha1_do_hmac(&sha1_sc_mac_s1, &sha1_sc_mac_s2, blk, len, seq, correct);
return !memcmp(correct, blk+len, 20);
}
struct ssh_mac ssh_sha1 = {
sha1_cskey, sha1_sckey,
sha1_generate,
sha1_verify,
"hmac-sha1",
20
};