static int
server_input_hostkeys_prove(struct sshbuf **respp)
{
struct ssh *ssh = active_state; /* XXX */
struct sshbuf *resp = NULL;
struct sshbuf *sigbuf = NULL;
struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
int r, ndx, success = 0;
const u_char *blob;
u_char *sig = 0;
size_t blen, slen;
if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new", __func__);
while (ssh_packet_remaining(ssh) > 0) {
sshkey_free(key);
key = NULL;
if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
(r = sshkey_from_blob(blob, blen, &key)) != 0) {
error("%s: couldn't parse key: %s",
__func__, ssh_err(r));
goto out;
}
/*
* Better check that this is actually one of our hostkeys
* before attempting to sign anything with it.
*/
if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
error("%s: unknown host %s key",
__func__, sshkey_type(key));
goto out;
}
/*
* XXX refactor: make kex->sign just use an index rather
* than passing in public and private keys
*/
if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
(key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
error("%s: can't retrieve hostkey %d", __func__, ndx);
goto out;
}
sshbuf_reset(sigbuf);
free(sig);
sig = NULL;
if ((r = sshbuf_put_cstring(sigbuf,
"*****@*****.**")) != 0 ||
(r = sshbuf_put_string(sigbuf,
ssh->kex->session_id, ssh->kex->session_id_len)) != 0 ||
(r = sshkey_puts(key, sigbuf)) != 0 ||
(r = ssh->kex->sign(key_prv, key_pub, &sig, &slen,
sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), 0)) != 0 ||
(r = sshbuf_put_string(resp, sig, slen)) != 0) {
error("%s: couldn't prepare signature: %s",
__func__, ssh_err(r));
goto out;
}
}
/* Success */
*respp = resp;
resp = NULL; /* don't free it */
success = 1;
out:
free(sig);
sshbuf_free(resp);
sshbuf_free(sigbuf);
sshkey_free(key);
return success;
}
int
mm_answer_sign(int sock, Buffer *m)
{
struct ssh *ssh = active_state; /* XXX */
extern int auth_sock; /* XXX move to state struct? */
struct sshkey *key;
struct sshbuf *sigbuf = NULL;
u_char *p = NULL, *signature = NULL;
char *alg = NULL;
size_t datlen, siglen, alglen;
int r, is_proof = 0;
u_int keyid;
const char proof_req[] = "*****@*****.**";
debug3("%s", __func__);
if ((r = sshbuf_get_u32(m, &keyid)) != 0 ||
(r = sshbuf_get_string(m, &p, &datlen)) != 0 ||
(r = sshbuf_get_cstring(m, &alg, &alglen)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
if (keyid > INT_MAX)
fatal("%s: invalid key ID", __func__);
/*
* Supported KEX types use SHA1 (20 bytes), SHA256 (32 bytes),
* SHA384 (48 bytes) and SHA512 (64 bytes).
*
* Otherwise, verify the signature request is for a hostkey
* proof.
*
* XXX perform similar check for KEX signature requests too?
* it's not trivial, since what is signed is the hash, rather
* than the full kex structure...
*/
if (datlen != 20 && datlen != 32 && datlen != 48 && datlen != 64) {
/*
* Construct expected hostkey proof and compare it to what
* the client sent us.
*/
if (session_id2_len == 0) /* hostkeys is never first */
fatal("%s: bad data length: %zu", __func__, datlen);
if ((key = get_hostkey_public_by_index(keyid, ssh)) == NULL)
fatal("%s: no hostkey for index %d", __func__, keyid);
if ((sigbuf = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new", __func__);
if ((r = sshbuf_put_cstring(sigbuf, proof_req)) != 0 ||
(r = sshbuf_put_string(sigbuf, session_id2,
session_id2_len)) != 0 ||
(r = sshkey_puts(key, sigbuf)) != 0)
fatal("%s: couldn't prepare private key "
"proof buffer: %s", __func__, ssh_err(r));
if (datlen != sshbuf_len(sigbuf) ||
memcmp(p, sshbuf_ptr(sigbuf), sshbuf_len(sigbuf)) != 0)
fatal("%s: bad data length: %zu, hostkey proof len %zu",
__func__, datlen, sshbuf_len(sigbuf));
sshbuf_free(sigbuf);
is_proof = 1;
}
/* save session id, it will be passed on the first call */
if (session_id2_len == 0) {
session_id2_len = datlen;
session_id2 = xmalloc(session_id2_len);
memcpy(session_id2, p, session_id2_len);
}
if ((key = get_hostkey_by_index(keyid)) != NULL) {
if ((r = sshkey_sign(key, &signature, &siglen, p, datlen, alg,
datafellows)) != 0)
fatal("%s: sshkey_sign failed: %s",
__func__, ssh_err(r));
} else if ((key = get_hostkey_public_by_index(keyid, ssh)) != NULL &&
auth_sock > 0) {
if ((r = ssh_agent_sign(auth_sock, key, &signature, &siglen,
p, datlen, alg, datafellows)) != 0) {
fatal("%s: ssh_agent_sign failed: %s",
__func__, ssh_err(r));
}
} else
fatal("%s: no hostkey from index %d", __func__, keyid);
debug3("%s: %s signature %p(%zu)", __func__,
is_proof ? "KEX" : "hostkey proof", signature, siglen);
sshbuf_reset(m);
if ((r = sshbuf_put_string(m, signature, siglen)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
free(alg);
free(p);
free(signature);
mm_request_send(sock, MONITOR_ANS_SIGN, m);
/* Turn on permissions for getpwnam */
monitor_permit(mon_dispatch, MONITOR_REQ_PWNAM, 1);
return (0);
}