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putty-source/sshmd5.c
Simon Tatham 853bd8b284 Turn SSH-2 MACs into a classoid. 
This piece of tidying-up has come out particularly well in terms of
saving tedious repetition and boilerplate. I've managed to remove
three pointless methods from every MAC implementation by means of
writing them once centrally in terms of the implementation-specific
methods; another method (hmacmd5_sink) vanished because I was able to
make the interface type 'ssh2_mac' be directly usable as a BinarySink
by way of a new delegation system; and because all the method
implementations can now find their own vtable, I was even able to
merge a lot of keying and output functions that had previously
differed only in length parameters by having them look up the lengths
in whatever vtable they were passed.
2018-09-19 23:08:07 +01:00

329 lines
9.7 KiB
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#include <assert.h>
#include "ssh.h"
/*
* MD5 implementation for PuTTY. Written directly from the spec by
* Simon Tatham.
*/
/* ----------------------------------------------------------------------
* Core MD5 algorithm: processes 16-word blocks into a message digest.
*/
#define F(x,y,z) ( ((x) & (y)) | ((~(x)) & (z)) )
#define G(x,y,z) ( ((x) & (z)) | ((~(z)) & (y)) )
#define H(x,y,z) ( (x) ^ (y) ^ (z) )
#define I(x,y,z) ( (y) ^ ( (x) | ~(z) ) )
#define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) )
#define subround(f,w,x,y,z,k,s,ti) \
w = x + rol(w + f(x,y,z) + block[k] + ti, s)
static void MD5_Core_Init(MD5_Core_State * s)
{
s->h[0] = 0x67452301;
s->h[1] = 0xefcdab89;
s->h[2] = 0x98badcfe;
s->h[3] = 0x10325476;
}
static void MD5_Block(MD5_Core_State * s, uint32 * block)
{
uint32 a, b, c, d;
a = s->h[0];
b = s->h[1];
c = s->h[2];
d = s->h[3];
subround(F, a, b, c, d, 0, 7, 0xd76aa478);
subround(F, d, a, b, c, 1, 12, 0xe8c7b756);
subround(F, c, d, a, b, 2, 17, 0x242070db);
subround(F, b, c, d, a, 3, 22, 0xc1bdceee);
subround(F, a, b, c, d, 4, 7, 0xf57c0faf);
subround(F, d, a, b, c, 5, 12, 0x4787c62a);
subround(F, c, d, a, b, 6, 17, 0xa8304613);
subround(F, b, c, d, a, 7, 22, 0xfd469501);
subround(F, a, b, c, d, 8, 7, 0x698098d8);
subround(F, d, a, b, c, 9, 12, 0x8b44f7af);
subround(F, c, d, a, b, 10, 17, 0xffff5bb1);
subround(F, b, c, d, a, 11, 22, 0x895cd7be);
subround(F, a, b, c, d, 12, 7, 0x6b901122);
subround(F, d, a, b, c, 13, 12, 0xfd987193);
subround(F, c, d, a, b, 14, 17, 0xa679438e);
subround(F, b, c, d, a, 15, 22, 0x49b40821);
subround(G, a, b, c, d, 1, 5, 0xf61e2562);
subround(G, d, a, b, c, 6, 9, 0xc040b340);
subround(G, c, d, a, b, 11, 14, 0x265e5a51);
subround(G, b, c, d, a, 0, 20, 0xe9b6c7aa);
subround(G, a, b, c, d, 5, 5, 0xd62f105d);
subround(G, d, a, b, c, 10, 9, 0x02441453);
subround(G, c, d, a, b, 15, 14, 0xd8a1e681);
subround(G, b, c, d, a, 4, 20, 0xe7d3fbc8);
subround(G, a, b, c, d, 9, 5, 0x21e1cde6);
subround(G, d, a, b, c, 14, 9, 0xc33707d6);
subround(G, c, d, a, b, 3, 14, 0xf4d50d87);
subround(G, b, c, d, a, 8, 20, 0x455a14ed);
subround(G, a, b, c, d, 13, 5, 0xa9e3e905);
subround(G, d, a, b, c, 2, 9, 0xfcefa3f8);
subround(G, c, d, a, b, 7, 14, 0x676f02d9);
subround(G, b, c, d, a, 12, 20, 0x8d2a4c8a);
subround(H, a, b, c, d, 5, 4, 0xfffa3942);
subround(H, d, a, b, c, 8, 11, 0x8771f681);
subround(H, c, d, a, b, 11, 16, 0x6d9d6122);
subround(H, b, c, d, a, 14, 23, 0xfde5380c);
subround(H, a, b, c, d, 1, 4, 0xa4beea44);
subround(H, d, a, b, c, 4, 11, 0x4bdecfa9);
subround(H, c, d, a, b, 7, 16, 0xf6bb4b60);
subround(H, b, c, d, a, 10, 23, 0xbebfbc70);
subround(H, a, b, c, d, 13, 4, 0x289b7ec6);
subround(H, d, a, b, c, 0, 11, 0xeaa127fa);
subround(H, c, d, a, b, 3, 16, 0xd4ef3085);
subround(H, b, c, d, a, 6, 23, 0x04881d05);
subround(H, a, b, c, d, 9, 4, 0xd9d4d039);
subround(H, d, a, b, c, 12, 11, 0xe6db99e5);
subround(H, c, d, a, b, 15, 16, 0x1fa27cf8);
subround(H, b, c, d, a, 2, 23, 0xc4ac5665);
subround(I, a, b, c, d, 0, 6, 0xf4292244);
subround(I, d, a, b, c, 7, 10, 0x432aff97);
subround(I, c, d, a, b, 14, 15, 0xab9423a7);
subround(I, b, c, d, a, 5, 21, 0xfc93a039);
subround(I, a, b, c, d, 12, 6, 0x655b59c3);
subround(I, d, a, b, c, 3, 10, 0x8f0ccc92);
subround(I, c, d, a, b, 10, 15, 0xffeff47d);
subround(I, b, c, d, a, 1, 21, 0x85845dd1);
subround(I, a, b, c, d, 8, 6, 0x6fa87e4f);
subround(I, d, a, b, c, 15, 10, 0xfe2ce6e0);
subround(I, c, d, a, b, 6, 15, 0xa3014314);
subround(I, b, c, d, a, 13, 21, 0x4e0811a1);
subround(I, a, b, c, d, 4, 6, 0xf7537e82);
subround(I, d, a, b, c, 11, 10, 0xbd3af235);
subround(I, c, d, a, b, 2, 15, 0x2ad7d2bb);
subround(I, b, c, d, a, 9, 21, 0xeb86d391);
s->h[0] += a;
s->h[1] += b;
s->h[2] += c;
s->h[3] += d;
}
/* ----------------------------------------------------------------------
* Outer MD5 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 MD5 algorithm.
*/
#define BLKSIZE 64
static void MD5_BinarySink_write(BinarySink *bs, const void *data, size_t len);
void MD5Init(struct MD5Context *s)
{
MD5_Core_Init(&s->core);
s->blkused = 0;
s->lenhi = s->lenlo = 0;
BinarySink_INIT(s, MD5_BinarySink_write);
}
static void MD5_BinarySink_write(BinarySink *bs, const void *data, size_t len)
{
struct MD5Context *s = BinarySink_DOWNCAST(bs, struct MD5Context);
const unsigned char *q = (const unsigned char *)data;
uint32 wordblock[16];
uint32 lenw = len;
int i;
assert(lenw == len);
/*
* Update the length field.
*/
s->lenlo += lenw;
s->lenhi += (s->lenlo < lenw);
if (s->blkused + len < BLKSIZE) {
/*
* 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 >= BLKSIZE) {
memcpy(s->block + s->blkused, q, BLKSIZE - s->blkused);
q += BLKSIZE - s->blkused;
len -= BLKSIZE - s->blkused;
/* Now process the block. Gather bytes little-endian into words */
for (i = 0; i < 16; i++) {
wordblock[i] =
(((uint32) s->block[i * 4 + 3]) << 24) |
(((uint32) s->block[i * 4 + 2]) << 16) |
(((uint32) s->block[i * 4 + 1]) << 8) |
(((uint32) s->block[i * 4 + 0]) << 0);
}
MD5_Block(&s->core, wordblock);
s->blkused = 0;
}
memcpy(s->block, q, len);
s->blkused = len;
}
}
void MD5Final(unsigned char output[16], struct MD5Context *s)
{
int i;
unsigned 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;
put_data(s, c, pad);
c[7] = (lenhi >> 24) & 0xFF;
c[6] = (lenhi >> 16) & 0xFF;
c[5] = (lenhi >> 8) & 0xFF;
c[4] = (lenhi >> 0) & 0xFF;
c[3] = (lenlo >> 24) & 0xFF;
c[2] = (lenlo >> 16) & 0xFF;
c[1] = (lenlo >> 8) & 0xFF;
c[0] = (lenlo >> 0) & 0xFF;
put_data(s, c, 8);
for (i = 0; i < 4; i++) {
output[4 * i + 3] = (s->core.h[i] >> 24) & 0xFF;
output[4 * i + 2] = (s->core.h[i] >> 16) & 0xFF;
output[4 * i + 1] = (s->core.h[i] >> 8) & 0xFF;
output[4 * i + 0] = (s->core.h[i] >> 0) & 0xFF;
}
}
void MD5Simple(void const *p, unsigned len, unsigned char output[16])
{
struct MD5Context s;
MD5Init(&s);
put_data(&s, (unsigned char const *)p, len);
MD5Final(output, &s);
smemclr(&s, sizeof(s));
}
/* ----------------------------------------------------------------------
* The above is the MD5 algorithm itself. Now we implement the
* HMAC wrapper on it.
*
* Some of these functions are exported directly, because they are
* useful elsewhere (SOCKS5 CHAP authentication uses HMAC-MD5).
*/
struct hmacmd5_context {
struct MD5Context md5[3];
ssh2_mac mac;
};
struct hmacmd5_context *hmacmd5_make_context(void)
{
struct hmacmd5_context *ctx = snew(struct hmacmd5_context);
BinarySink_DELEGATE_INIT(&ctx->mac, &ctx->md5[2]);
return ctx;
}
static ssh2_mac *hmacmd5_ssh2_new(const struct ssh2_macalg *alg,
ssh2_cipher *cipher)
{
struct hmacmd5_context *ctx = hmacmd5_make_context();
ctx->mac.vt = alg;
return &ctx->mac;
}
void hmacmd5_free_context(struct hmacmd5_context *ctx)
{
smemclr(ctx, sizeof(*ctx));
sfree(ctx);
}
static void hmacmd5_ssh2_free(ssh2_mac *mac)
{
struct hmacmd5_context *ctx = FROMFIELD(mac, struct hmacmd5_context, mac);
hmacmd5_free_context(ctx);
}
void hmacmd5_key(struct hmacmd5_context *ctx, void const *keyv, int len)
{
unsigned char foo[64];
unsigned char const *key = (unsigned char const *)keyv;
int i;
memset(foo, 0x36, 64);
for (i = 0; i < len && i < 64; i++)
foo[i] ^= key[i];
MD5Init(&ctx->md5[0]);
put_data(&ctx->md5[0], foo, 64);
memset(foo, 0x5C, 64);
for (i = 0; i < len && i < 64; i++)
foo[i] ^= key[i];
MD5Init(&ctx->md5[1]);
put_data(&ctx->md5[1], foo, 64);
smemclr(foo, 64); /* burn the evidence */
}
static void hmacmd5_ssh2_setkey(ssh2_mac *mac, const void *key)
{
struct hmacmd5_context *ctx = FROMFIELD(mac, struct hmacmd5_context, mac);
hmacmd5_key(ctx, key, ctx->mac.vt->keylen);
}
static void hmacmd5_start(ssh2_mac *mac)
{
struct hmacmd5_context *ctx = FROMFIELD(mac, struct hmacmd5_context, mac);
ctx->md5[2] = ctx->md5[0]; /* structure copy */
BinarySink_COPIED(&ctx->md5[2]);
}
static void hmacmd5_genresult(ssh2_mac *mac, unsigned char *hmac)
{
struct hmacmd5_context *ctx = FROMFIELD(mac, struct hmacmd5_context, mac);
struct MD5Context s;
unsigned char intermediate[16];
s = ctx->md5[2]; /* structure copy */
BinarySink_COPIED(&s);
MD5Final(intermediate, &s);
s = ctx->md5[1]; /* structure copy */
BinarySink_COPIED(&s);
put_data(&s, intermediate, 16);
MD5Final(hmac, &s);
smemclr(intermediate, sizeof(intermediate));
}
void hmacmd5_do_hmac(struct hmacmd5_context *ctx,
unsigned char const *blk, int len, unsigned char *hmac)
{
ssh2_mac_start(&ctx->mac);
put_data(&ctx->mac, blk, len);
return ssh2_mac_genresult(&ctx->mac, hmac);
}
const struct ssh2_macalg ssh_hmac_md5 = {
hmacmd5_ssh2_new, hmacmd5_ssh2_free, hmacmd5_ssh2_setkey,
hmacmd5_start, hmacmd5_genresult,
"hmac-md5", "hmac-md5-etm@openssh.com",
16, 16,
"HMAC-MD5"
};
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