static int
input_kex_dh_gex_request(int type, u_int32_t seq, void *ctxt)
{
struct ssh *ssh = ctxt;
struct kex *kex = ssh->kex;
int r;
u_int min = 0, max = 0, nbits = 0;
debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
(r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
(r = sshpkt_get_u32(ssh, &max)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
kex->nbits = nbits;
kex->min = min;
kex->max = max;
min = MAX(DH_GRP_MIN, min);
max = MIN(DH_GRP_MAX, max);
nbits = MAX(DH_GRP_MIN, nbits);
nbits = MIN(DH_GRP_MAX, nbits);
if (kex->max < kex->min || kex->nbits < kex->min ||
kex->max < kex->nbits) {
r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
goto out;
}
/* Contact privileged parent */
kex->dh = PRIVSEP(choose_dh(min, nbits, max));
if (kex->dh == NULL) {
sshpkt_disconnect(ssh, "no matching DH grp found");
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
(r = sshpkt_put_bignum2(ssh, kex->dh->p)) != 0 ||
(r = sshpkt_put_bignum2(ssh, kex->dh->g)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
/* Compute our exchange value in parallel with the client */
if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
goto out;
debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
r = 0;
out:
return r;
}
void
ssh_packet_put_bignum2(struct ssh *ssh, BIGNUM * value)
{
int r;
if ((r = sshpkt_put_bignum2(ssh, value)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
}
static int
input_kex_dh_gex_group(int type, u_int32_t seq, void *ctxt)
{
struct ssh *ssh = ctxt;
struct kex *kex = ssh->kex;
BIGNUM *p = NULL, *g = NULL;
int r, bits;
debug("got SSH2_MSG_KEX_DH_GEX_GROUP");
if ((p = BN_new()) == NULL ||
(g = BN_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((r = sshpkt_get_bignum2(ssh, p)) != 0 ||
(r = sshpkt_get_bignum2(ssh, g)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
if ((bits = BN_num_bits(p)) < 0 ||
(u_int)bits < kex->min || (u_int)bits > kex->max) {
r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
goto out;
}
if ((kex->dh = dh_new_group(g, p)) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
p = g = NULL; /* belong to kex->dh now */
/* generate and send 'e', client DH public key */
if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
(r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_INIT)) != 0 ||
(r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
#ifdef DEBUG_KEXDH
DHparams_print_fp(stderr, kex->dh);
fprintf(stderr, "pub= ");
BN_print_fp(stderr, kex->dh->pub_key);
fprintf(stderr, "\n");
#endif
ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_GROUP, NULL);
ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REPLY, &input_kex_dh_gex_reply);
r = 0;
out:
if (p)
BN_clear_free(p);
if (g)
BN_clear_free(g);
return r;
}
int
kexdh_client(struct ssh *ssh)
{
struct kex *kex = ssh->kex;
int r;
/* generate and send 'e', client DH public key */
switch (kex->kex_type) {
case KEX_DH_GRP1_SHA1:
kex->dh = dh_new_group1();
break;
case KEX_DH_GRP14_SHA1:
case KEX_DH_GRP14_SHA256:
kex->dh = dh_new_group14();
break;
case KEX_DH_GRP16_SHA512:
kex->dh = dh_new_group16();
break;
case KEX_DH_GRP18_SHA512:
kex->dh = dh_new_group18();
break;
default:
r = SSH_ERR_INVALID_ARGUMENT;
goto out;
}
if (kex->dh == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
debug("sending SSH2_MSG_KEXDH_INIT");
if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0 ||
(r = sshpkt_start(ssh, SSH2_MSG_KEXDH_INIT)) != 0 ||
(r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
#ifdef DEBUG_KEXDH
DHparams_print_fp(stderr, kex->dh);
fprintf(stderr, "pub= ");
BN_print_fp(stderr, kex->dh->pub_key);
fprintf(stderr, "\n");
#endif
debug("expecting SSH2_MSG_KEXDH_REPLY");
ssh_dispatch_set(ssh, SSH2_MSG_KEXDH_REPLY, &input_kex_dh);
r = 0;
out:
return r;
}
int
input_kex_dh_init(int type, u_int32_t seq, void *ctxt)
{
struct ssh *ssh = ctxt;
struct kex *kex = ssh->kex;
BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
struct sshkey *server_host_public, *server_host_private;
u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
u_char hash[SSH_DIGEST_MAX_LENGTH];
size_t sbloblen, slen;
size_t klen = 0, hashlen;
int kout, r;
if (kex->load_host_public_key == NULL ||
kex->load_host_private_key == NULL) {
r = SSH_ERR_INVALID_ARGUMENT;
goto out;
}
server_host_public = kex->load_host_public_key(kex->hostkey_type,
kex->hostkey_nid, ssh);
server_host_private = kex->load_host_private_key(kex->hostkey_type,
kex->hostkey_nid, ssh);
if (server_host_public == NULL) {
r = SSH_ERR_NO_HOSTKEY_LOADED;
goto out;
}
/* key, cert */
if ((dh_client_pub = BN_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
#ifdef DEBUG_KEXDH
fprintf(stderr, "dh_client_pub= ");
BN_print_fp(stderr, dh_client_pub);
fprintf(stderr, "\n");
debug("bits %d", BN_num_bits(dh_client_pub));
#endif
#ifdef DEBUG_KEXDH
DHparams_print_fp(stderr, kex->dh);
fprintf(stderr, "pub= ");
BN_print_fp(stderr, kex->dh->pub_key);
fprintf(stderr, "\n");
#endif
if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
sshpkt_disconnect(ssh, "bad client public DH value");
r = SSH_ERR_MESSAGE_INCOMPLETE;
goto out;
}
klen = DH_size(kex->dh);
if ((kbuf = malloc(klen)) == NULL ||
(shared_secret = BN_new()) == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
r = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
#ifdef DEBUG_KEXDH
dump_digest("shared secret", kbuf, kout);
#endif
if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
&sbloblen)) != 0)
goto out;
/* calc H */
hashlen = sizeof(hash);
if ((r = kex_dh_hash(
kex->client_version_string,
kex->server_version_string,
sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
sshbuf_ptr(kex->my), sshbuf_len(kex->my),
server_host_key_blob, sbloblen,
dh_client_pub,
kex->dh->pub_key,
shared_secret,
hash, &hashlen)) != 0)
goto out;
/* save session id := H */
if (kex->session_id == NULL) {
kex->session_id_len = hashlen;
kex->session_id = malloc(kex->session_id_len);
if (kex->session_id == NULL) {
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
memcpy(kex->session_id, hash, kex->session_id_len);
}
/* sign H */
if ((r = kex->sign(server_host_private, server_host_public, &signature,
&slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
goto out;
/* destroy_sensitive_data(); */
/* send server hostkey, DH pubkey 'f' and singed H */
if ((r = sshpkt_start(ssh, SSH2_MSG_KEXDH_REPLY)) != 0 ||
(r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
(r = sshpkt_put_bignum2(ssh, kex->dh->pub_key)) != 0 || /* f */
(r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
r = kex_send_newkeys(ssh);
out:
explicit_bzero(hash, sizeof(hash));
DH_free(kex->dh);
kex->dh = NULL;
if (dh_client_pub)
BN_clear_free(dh_client_pub);
if (kbuf) {
explicit_bzero(kbuf, klen);
free(kbuf);
}
if (shared_secret)
BN_clear_free(shared_secret);
free(server_host_key_blob);
free(signature);
return r;
}
static int
input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh)
{
Kex *kex = ssh->kex;
int r, min = -1, max = -1, nbits = -1;
switch (type) {
case SSH2_MSG_KEX_DH_GEX_REQUEST:
debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
(r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
(r = sshpkt_get_u32(ssh, &max)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
kex->nbits = nbits;
kex->min = min;
kex->max = max;
min = MAX(DH_GRP_MIN, min);
max = MIN(DH_GRP_MAX, max);
nbits = MAX(DH_GRP_MIN, nbits);
nbits = MIN(DH_GRP_MAX, nbits);
break;
case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
if ((r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
goto out;
kex->nbits = nbits;
/* unused for old GEX */
kex->min = min = DH_GRP_MIN;
kex->max = max = DH_GRP_MAX;
break;
default:
r = SSH_ERR_INVALID_ARGUMENT;
goto out;
}
if (kex->max < kex->min || kex->nbits < kex->min ||
kex->max < kex->nbits) {
r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
goto out;
}
/* Contact privileged parent */
kex->dh = PRIVSEP(choose_dh(min, nbits, max));
if (kex->dh == NULL) {
sshpkt_disconnect(ssh, "no matching DH grp found");
r = SSH_ERR_ALLOC_FAIL;
goto out;
}
debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
(r = sshpkt_put_bignum2(ssh, kex->dh->p)) != 0 ||
(r = sshpkt_put_bignum2(ssh, kex->dh->g)) != 0 ||
(r = sshpkt_send(ssh)) != 0)
goto out;
/* Compute our exchange value in parallel with the client */
if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
goto out;
/* old KEX does not use min/max in kexgex_hash() */
if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
kex->min = kex->max = -1;
debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
r = 0;
out:
return r;
}
