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Add support for RFC 4432 RSA key exchange, the patch for which has been

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lying around in my home directory for _years_.

[originally from svn r7496]
This commit is contained in:
Ben Harris
2007-04-30 22:09:26 +00:00
parent 9f7f5157fe
commit dad558a1e5
9 changed files with 314 additions and 29 deletions
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138
ssh.c
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@ -83,6 +83,9 @@
#define SSH2_MSG_KEX_DH_GEX_GROUP 31 /* 0x1f */
#define SSH2_MSG_KEX_DH_GEX_INIT 32 /* 0x20 */
#define SSH2_MSG_KEX_DH_GEX_REPLY 33 /* 0x21 */
#define SSH2_MSG_KEXRSA_PUBKEY 30 /* 0x1e */
#define SSH2_MSG_KEXRSA_SECRET 31 /* 0x1f */
#define SSH2_MSG_KEXRSA_DONE 32 /* 0x20 */
#define SSH2_MSG_USERAUTH_REQUEST 50 /* 0x32 */
#define SSH2_MSG_USERAUTH_FAILURE 51 /* 0x33 */
#define SSH2_MSG_USERAUTH_SUCCESS 52 /* 0x34 */
@ -112,6 +115,7 @@
*/
#define SSH2_PKTCTX_DHGROUP 0x0001
#define SSH2_PKTCTX_DHGEX 0x0002
#define SSH2_PKTCTX_RSAKEX 0x0004
#define SSH2_PKTCTX_KEX_MASK 0x000F
#define SSH2_PKTCTX_PUBLICKEY 0x0010
#define SSH2_PKTCTX_PASSWORD 0x0020
@ -339,6 +343,9 @@ static char *ssh2_pkt_type(int pkt_ctx, int type)
translatec(SSH2_MSG_KEX_DH_GEX_GROUP, SSH2_PKTCTX_DHGEX);
translatec(SSH2_MSG_KEX_DH_GEX_INIT, SSH2_PKTCTX_DHGEX);
translatec(SSH2_MSG_KEX_DH_GEX_REPLY, SSH2_PKTCTX_DHGEX);
translatec(SSH2_MSG_KEXRSA_PUBKEY, SSH2_PKTCTX_RSAKEX);
translatec(SSH2_MSG_KEXRSA_SECRET, SSH2_PKTCTX_RSAKEX);
translatec(SSH2_MSG_KEXRSA_DONE, SSH2_PKTCTX_RSAKEX);
translate(SSH2_MSG_USERAUTH_REQUEST);
translate(SSH2_MSG_USERAUTH_FAILURE);
translate(SSH2_MSG_USERAUTH_SUCCESS);
@ -5105,9 +5112,10 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
const struct ssh_mac *scmac_tobe;
const struct ssh_compress *cscomp_tobe;
const struct ssh_compress *sccomp_tobe;
char *hostkeydata, *sigdata, *keystr, *fingerprint;
int hostkeylen, siglen;
char *hostkeydata, *sigdata, *rsakeydata, *keystr, *fingerprint;
int hostkeylen, siglen, rsakeylen;
void *hkey; /* actual host key */
void *rsakey; /* for RSA kex */
unsigned char exchange_hash[SSH2_KEX_MAX_HASH_LEN];
int n_preferred_kex;
const struct ssh_kexes *preferred_kex[KEX_MAX];
@ -5161,6 +5169,10 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
s->preferred_kex[s->n_preferred_kex++] =
&ssh_diffiehellman_group1;
break;
case KEX_RSA:
s->preferred_kex[s->n_preferred_kex++] =
&ssh_rsa_kex;
break;
case KEX_WARN:
/* Flag for later. Don't bother if it's the last in
* the list. */
@ -5560,6 +5572,8 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
crWaitUntil(pktin); /* Ignore packet */
}
if (ssh->kex->main_type == KEXTYPE_DH) {
/* XXX The lines below should be reindented before this is committed.*/
/*
* Work out the number of bits of key we will need from the key
* exchange. We start with the maximum key length of either
@ -5635,6 +5649,7 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
}
set_busy_status(ssh->frontend, BUSY_CPU); /* cogitate */
ssh_pkt_getstring(pktin, &s->hostkeydata, &s->hostkeylen);
s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
s->f = ssh2_pkt_getmp(pktin);
if (!s->f) {
bombout(("unable to parse key exchange reply packet"));
@ -5656,11 +5671,120 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
}
hash_mpint(ssh->kex->hash, ssh->exhash, s->e);
hash_mpint(ssh->kex->hash, ssh->exhash, s->f);
dh_cleanup(ssh->kex_ctx);
freebn(s->f);
if (!ssh->kex->pdata) {
freebn(s->g);
freebn(s->p);
}
/* XXX end incorrectly-indented section */
} else {
logeventf(ssh, "Doing RSA key exchange with hash %s",
ssh->kex->hash->text_name);
ssh->pkt_ctx |= SSH2_PKTCTX_RSAKEX;
/*
* RSA key exchange. First expect a KEXRSA_PUBKEY packet
* from the server.
*/
crWaitUntil(pktin);
if (pktin->type != SSH2_MSG_KEXRSA_PUBKEY) {
bombout(("expected RSA public key packet from server"));
crStop(0);
}
ssh_pkt_getstring(pktin, &s->hostkeydata, &s->hostkeylen);
hash_string(ssh->kex->hash, ssh->exhash,
s->hostkeydata, s->hostkeylen);
s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
{
char *keydata;
ssh_pkt_getstring(pktin, &keydata, &s->rsakeylen);
s->rsakeydata = snewn(s->rsakeylen, char);
memcpy(s->rsakeydata, keydata, s->rsakeylen);
}
s->rsakey = ssh_rsakex_newkey(s->rsakeydata, s->rsakeylen);
if (!s->rsakey) {
sfree(s->rsakeydata);
bombout(("unable to parse RSA public key from server"));
crStop(0);
}
hash_string(ssh->kex->hash, ssh->exhash, s->rsakeydata, s->rsakeylen);
/*
* Next, set up a shared secret K, of precisely KLEN -
* 2*HLEN - 49 bits, where KLEN is the bit length of the
* RSA key modulus and HLEN is the bit length of the hash
* we're using.
*/
{
int klen = ssh_rsakex_klen(s->rsakey);
int nbits = klen - (2*ssh->kex->hash->hlen*8 + 49);
int i, byte = 0;
unsigned char *kstr1, *kstr2, *outstr;
int kstr1len, kstr2len, outstrlen;
s->K = bn_power_2(nbits - 1);
for (i = 0; i < nbits; i++) {
if ((i & 7) == 0) {
byte = random_byte();
}
bignum_set_bit(s->K, i, (byte >> (i & 7)) & 1);
}
/*
* Encode this as an mpint.
*/
kstr1 = ssh2_mpint_fmt(s->K, &kstr1len);
kstr2 = snewn(kstr2len = 4 + kstr1len, unsigned char);
PUT_32BIT(kstr2, kstr1len);
memcpy(kstr2 + 4, kstr1, kstr1len);
/*
* Encrypt it with the given RSA key.
*/
outstrlen = (klen + 7) / 8;
outstr = snewn(outstrlen, unsigned char);
ssh_rsakex_encrypt(ssh->kex->hash, kstr2, kstr2len,
outstr, outstrlen, s->rsakey);
/*
* And send it off in a return packet.
*/
s->pktout = ssh2_pkt_init(SSH2_MSG_KEXRSA_SECRET);
ssh2_pkt_addstring_start(s->pktout);
ssh2_pkt_addstring_data(s->pktout, outstr, outstrlen);
ssh2_pkt_send_noqueue(ssh, s->pktout);
hash_string(ssh->kex->hash, ssh->exhash, outstr, outstrlen);
sfree(kstr2);
sfree(kstr1);
sfree(outstr);
}
ssh_rsakex_freekey(s->rsakey);
crWaitUntil(pktin);
if (pktin->type != SSH2_MSG_KEXRSA_DONE) {
sfree(s->rsakeydata);
bombout(("expected signature packet from server"));
crStop(0);
}
ssh_pkt_getstring(pktin, &s->sigdata, &s->siglen);
sfree(s->rsakeydata);
}
hash_mpint(ssh->kex->hash, ssh->exhash, s->K);
assert(ssh->kex->hash->hlen <= sizeof(s->exchange_hash));
ssh->kex->hash->final(ssh->exhash, s->exchange_hash);
dh_cleanup(ssh->kex_ctx);
ssh->kex_ctx = NULL;
#if 0
@ -5668,7 +5792,6 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
dmemdump(s->exchange_hash, ssh->kex->hash->hlen);
#endif
s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
if (!s->hkey ||
!ssh->hostkey->verifysig(s->hkey, s->sigdata, s->siglen,
(char *)s->exchange_hash,
@ -5850,14 +5973,9 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
ssh->sccomp->text_name);
/*
* Free key exchange data.
* Free shared secret.
*/
freebn(s->f);
freebn(s->K);
if (!ssh->kex->pdata) {
freebn(s->g);
freebn(s->p);
}
/*
* Key exchange is over. Loop straight back round if we have a