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Implement MD5 MAC for the benefit of old SSH2 servers

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[originally from svn r709]
This commit is contained in:
Simon Tatham 2000-10-12 14:24:58 +00:00
parent fd3e15f328
commit 95697270b5
2 changed files with 88 additions and 11 deletions
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25
ssh.c
View File

@ -167,7 +167,7 @@ const static struct ssh_kex *kex_algs[] = { &ssh_diffiehellman };
extern const struct ssh_hostkey ssh_dss;
const static struct ssh_hostkey *hostkey_algs[] = { &ssh_dss };
extern const struct ssh_mac ssh_sha1, ssh_sha1_buggy;
extern const struct ssh_mac ssh_md5, ssh_sha1, ssh_sha1_buggy;
static void nullmac_key(unsigned char *key) { }
static void nullmac_generate(unsigned char *blk, int len, unsigned long seq) { }
@ -175,8 +175,10 @@ static int nullmac_verify(unsigned char *blk, int len, unsigned long seq) { retu
const static struct ssh_mac ssh_mac_none = {
nullmac_key, nullmac_key, nullmac_generate, nullmac_verify, "none", 0
};
const static struct ssh_mac *macs[] = { &ssh_sha1, &ssh_mac_none };
const static struct ssh_mac *buggymacs[] = { &ssh_sha1_buggy, &ssh_mac_none };
const static struct ssh_mac *macs[] = {
&ssh_sha1, &ssh_md5, &ssh_mac_none };
const static struct ssh_mac *buggymacs[] = {
&ssh_sha1_buggy, &ssh_md5, &ssh_mac_none };
const static struct ssh_compress ssh_comp_none = {
"none"
@ -1830,6 +1832,7 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
static char *str;
static Bignum e, f, K;
static const struct ssh_mac **maclist;
static int nmacs;
static const struct ssh_cipher *cscipher_tobe = NULL;
static const struct ssh_cipher *sccipher_tobe = NULL;
static const struct ssh_mac *csmac_tobe = NULL;
@ -1864,9 +1867,9 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
* Be prepared to work around the buggy MAC problem.
*/
if (cfg.buggymac)
maclist = buggymacs;
maclist = buggymacs, nmacs = lenof(buggymacs);
else
maclist = macs;
maclist = macs, nmacs = lenof(macs);
begin_key_exchange:
/*
@ -1907,16 +1910,16 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
}
/* List client->server MAC algorithms. */
ssh2_pkt_addstring_start();
for (i = 0; i < lenof(maclist); i++) {
for (i = 0; i < nmacs; i++) {
ssh2_pkt_addstring_str(maclist[i]->name);
if (i < lenof(maclist)-1)
if (i < nmacs-1)
ssh2_pkt_addstring_str(",");
}
/* List server->client MAC algorithms. */
ssh2_pkt_addstring_start();
for (i = 0; i < lenof(maclist); i++) {
for (i = 0; i < nmacs; i++) {
ssh2_pkt_addstring_str(maclist[i]->name);
if (i < lenof(maclist)-1)
if (i < nmacs-1)
ssh2_pkt_addstring_str(",");
}
/* List client->server compression algorithms. */
@ -1989,14 +1992,14 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
}
}
ssh2_pkt_getstring(&str, &len); /* client->server mac */
for (i = 0; i < lenof(maclist); i++) {
for (i = 0; i < nmacs; i++) {
if (in_commasep_string(maclist[i]->name, str, len)) {
csmac_tobe = maclist[i];
break;
}
}
ssh2_pkt_getstring(&str, &len); /* server->client mac */
for (i = 0; i < lenof(maclist); i++) {
for (i = 0; i < nmacs; i++) {
if (in_commasep_string(maclist[i]->name, str, len)) {
scmac_tobe = maclist[i];
break;

74
sshmd5.c
View File

@ -192,3 +192,77 @@ void MD5Final(unsigned char output[16], struct MD5Context *s) {
output[4*i+0] = (s->core.h[i] >> 0) & 0xFF;
}
}
/* ----------------------------------------------------------------------
* The above is the MD5 algorithm itself. Now we implement the
* HMAC wrapper on it.
*/
static struct MD5Context md5_cs_mac_s1, md5_cs_mac_s2;
static struct MD5Context md5_sc_mac_s1, md5_sc_mac_s2;
static void md5_key(struct MD5Context *s1, struct MD5Context *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];
MD5Init(s1);
MD5Update(s1, foo, 64);
memset(foo, 0x5C, 64);
for (i = 0; i < len && i < 64; i++)
foo[i] ^= key[i];
MD5Init(s2);
MD5Update(s2, foo, 64);
memset(foo, 0, 64); /* burn the evidence */
}
static void md5_cskey(unsigned char *key) {
md5_key(&md5_cs_mac_s1, &md5_cs_mac_s2, key, 16);
}
static void md5_sckey(unsigned char *key) {
md5_key(&md5_sc_mac_s1, &md5_sc_mac_s2, key, 16);
}
static void md5_do_hmac(struct MD5Context *s1, struct MD5Context *s2,
unsigned char *blk, int len, unsigned long seq,
unsigned char *hmac) {
struct MD5Context s;
unsigned char intermediate[16];
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 */
MD5Update(&s, intermediate, 4);
MD5Update(&s, blk, len);
MD5Final(intermediate, &s);
s = *s2; /* structure copy */
MD5Update(&s, intermediate, 16);
MD5Final(hmac, &s);
}
static void md5_generate(unsigned char *blk, int len, unsigned long seq) {
md5_do_hmac(&md5_cs_mac_s1, &md5_cs_mac_s2, blk, len, seq, blk+len);
}
static int md5_verify(unsigned char *blk, int len, unsigned long seq) {
unsigned char correct[16];
md5_do_hmac(&md5_sc_mac_s1, &md5_sc_mac_s2, blk, len, seq, correct);
return !memcmp(correct, blk+len, 16);
}
struct ssh_mac ssh_md5 = {
md5_cskey, md5_sckey,
md5_generate,
md5_verify,
"hmac-md5",
16
};