void
kexgex_client(Kex *kex)
{
BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
BIGNUM *p = NULL, *g = NULL;
Key *server_host_key;
u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
u_int klen, kout, slen, sbloblen;
int min, max, nbits;
DH *dh;
nbits = dh_estimate(kex->we_need * 8);
if (datafellows & SSH_OLD_DHGEX) {
debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");
/* Old GEX request */
packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
packet_put_int(nbits);
min = DH_GRP_MIN;
max = DH_GRP_MAX;
} else {
debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");
/* New GEX request */
min = DH_GRP_MIN;
max = DH_GRP_MAX;
packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
packet_put_int(min);
packet_put_int(nbits);
packet_put_int(max);
}
#ifdef DEBUG_KEXDH
fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
min, nbits, max);
#endif
packet_send();
debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
if ((p = BN_new()) == NULL)
fatal("BN_new");
packet_get_bignum2(p);
if ((g = BN_new()) == NULL)
fatal("BN_new");
packet_get_bignum2(g);
packet_check_eom();
if (BN_num_bits(p) < min || BN_num_bits(p) > max)
fatal("DH_GEX group out of range: %d !< %d !< %d",
min, BN_num_bits(p), max);
dh = dh_new_group(g, p);
dh_gen_key(dh, kex->we_need * 8);
#ifdef DEBUG_KEXDH
DHparams_print_fp(stderr, dh);
fprintf(stderr, "pub= ");
BN_print_fp(stderr, dh->pub_key);
fprintf(stderr, "\n");
#endif
debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
/* generate and send 'e', client DH public key */
packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
packet_put_bignum2(dh->pub_key);
packet_send();
debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
/* key, cert */
server_host_key_blob = packet_get_string(&sbloblen);
server_host_key = key_from_blob(server_host_key_blob, sbloblen);
if (server_host_key == NULL)
fatal("cannot decode server_host_key_blob");
if (server_host_key->type != kex->hostkey_type)
fatal("type mismatch for decoded server_host_key_blob");
if (kex->verify_host_key == NULL)
fatal("cannot verify server_host_key");
if (kex->verify_host_key(server_host_key) == -1)
fatal("server_host_key verification failed");
/* DH paramter f, server public DH key */
if ((dh_server_pub = BN_new()) == NULL)
fatal("dh_server_pub == NULL");
packet_get_bignum2(dh_server_pub);
#ifdef DEBUG_KEXDH
fprintf(stderr, "dh_server_pub= ");
BN_print_fp(stderr, dh_server_pub);
fprintf(stderr, "\n");
debug("bits %d", BN_num_bits(dh_server_pub));
#endif
/* signed H */
signature = packet_get_string(&slen);
packet_check_eom();
if (!dh_pub_is_valid(dh, dh_server_pub))
packet_disconnect("bad server public DH value");
klen = DH_size(dh);
kbuf = xmalloc(klen);
kout = DH_compute_key(kbuf, dh_server_pub, dh);
#ifdef DEBUG_KEXDH
dump_digest("shared secret", kbuf, kout);
#endif
if ((shared_secret = BN_new()) == NULL)
fatal("kexgex_client: BN_new failed");
BN_bin2bn(kbuf, kout, shared_secret);
memset(kbuf, 0, klen);
xfree(kbuf);
if (datafellows & SSH_OLD_DHGEX)
min = max = -1;
/* calc and verify H */
hash = kexgex_hash(
kex->client_version_string,
kex->server_version_string,
buffer_ptr(&kex->my), buffer_len(&kex->my),
buffer_ptr(&kex->peer), buffer_len(&kex->peer),
server_host_key_blob, sbloblen,
min, nbits, max,
dh->p, dh->g,
dh->pub_key,
dh_server_pub,
shared_secret
);
/* have keys, free DH */
DH_free(dh);
xfree(server_host_key_blob);
BN_clear_free(dh_server_pub);
if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
fatal("key_verify failed for server_host_key");
key_free(server_host_key);
xfree(signature);
/* save session id */
if (kex->session_id == NULL) {
kex->session_id_len = 20;
kex->session_id = xmalloc(kex->session_id_len);
memcpy(kex->session_id, hash, kex->session_id_len);
}
kex_derive_keys(kex, hash, shared_secret);
BN_clear_free(shared_secret);
kex_finish(kex);
}
void
kexgex_server(Kex *kex)
{
BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
Key *server_host_public, *server_host_private;
DH *dh;
u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
u_int sbloblen, klen, slen, hashlen;
int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
int type, kout;
if (kex->load_host_public_key == NULL ||
kex->load_host_private_key == NULL)
fatal("Cannot load hostkey");
server_host_public = kex->load_host_public_key(kex->hostkey_type);
if (server_host_public == NULL)
fatal("Unsupported hostkey type %d", kex->hostkey_type);
server_host_private = kex->load_host_private_key(kex->hostkey_type);
if (server_host_private == NULL)
fatal("Missing private key for hostkey type %d",
kex->hostkey_type);
type = packet_read();
switch (type) {
case SSH2_MSG_KEX_DH_GEX_REQUEST:
debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
omin = min = packet_get_int();
onbits = nbits = packet_get_int();
omax = max = packet_get_int();
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");
onbits = nbits = packet_get_int();
/* unused for old GEX */
omin = min = DH_GRP_MIN;
omax = max = DH_GRP_MAX;
break;
default:
fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
}
packet_check_eom();
if (omax < omin || onbits < omin || omax < onbits)
fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
omin, onbits, omax);
/* Contact privileged parent */
dh = PRIVSEP(choose_dh(min, nbits, max));
if (dh == NULL)
packet_disconnect("Protocol error: no matching DH grp found");
debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
packet_put_bignum2(dh->p);
packet_put_bignum2(dh->g);
packet_send();
/* flush */
packet_write_wait();
/* Compute our exchange value in parallel with the client */
dh_gen_key(dh, kex->we_need * 8);
debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
/* key, cert */
if ((dh_client_pub = BN_new()) == NULL)
fatal("dh_client_pub == NULL");
packet_get_bignum2(dh_client_pub);
packet_check_eom();
#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, dh);
fprintf(stderr, "pub= ");
BN_print_fp(stderr, dh->pub_key);
fprintf(stderr, "\n");
#endif
if (!dh_pub_is_valid(dh, dh_client_pub))
packet_disconnect("bad client public DH value");
klen = DH_size(dh);
kbuf = xmalloc(klen);
if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
fatal("DH_compute_key: failed");
#ifdef DEBUG_KEXDH
dump_digest("shared secret", kbuf, kout);
#endif
if ((shared_secret = BN_new()) == NULL)
fatal("kexgex_server: BN_new failed");
if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
fatal("kexgex_server: BN_bin2bn failed");
memset(kbuf, 0, klen);
xfree(kbuf);
key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
omin = min = omax = max = -1;
/* calc H */
kexgex_hash(
kex->evp_md,
kex->client_version_string,
kex->server_version_string,
buffer_ptr(&kex->peer), buffer_len(&kex->peer),
buffer_ptr(&kex->my), buffer_len(&kex->my),
server_host_key_blob, sbloblen,
omin, onbits, omax,
dh->p, dh->g,
dh_client_pub,
dh->pub_key,
shared_secret,
&hash, &hashlen
);
BN_clear_free(dh_client_pub);
/* save session id := H */
if (kex->session_id == NULL) {
kex->session_id_len = hashlen;
kex->session_id = xmalloc(kex->session_id_len);
memcpy(kex->session_id, hash, kex->session_id_len);
}
/* sign H */
if (PRIVSEP(key_sign(server_host_private, &signature, &slen, hash,
hashlen)) < 0)
fatal("kexgex_server: key_sign failed");
/* destroy_sensitive_data(); */
/* send server hostkey, DH pubkey 'f' and singed H */
debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
packet_put_string(server_host_key_blob, sbloblen);
packet_put_bignum2(dh->pub_key); /* f */
packet_put_string(signature, slen);
packet_send();
xfree(signature);
xfree(server_host_key_blob);
/* have keys, free DH */
DH_free(dh);
kex_derive_keys(kex, hash, hashlen, shared_secret);
BN_clear_free(shared_secret);
kex_finish(kex);
}
void
kexdh_server(Kex *kex)
{
BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
DH *dh;
Key *server_host_public, *server_host_private;
u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
u_int sbloblen, klen, hashlen, slen;
int kout;
/* generate server DH public key */
switch (kex->kex_type) {
case KEX_DH_GRP1_SHA1:
dh = dh_new_group1();
break;
case KEX_DH_GRP14_SHA1:
dh = dh_new_group14();
break;
default:
fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type);
}
dh_gen_key(dh, kex->we_need * 8);
debug("expecting SSH2_MSG_KEXDH_INIT");
packet_read_expect(SSH2_MSG_KEXDH_INIT);
if (kex->load_host_public_key == NULL ||
kex->load_host_private_key == NULL)
fatal("Cannot load hostkey");
server_host_public = kex->load_host_public_key(kex->hostkey_type);
if (server_host_public == NULL)
fatal("Unsupported hostkey type %d", kex->hostkey_type);
server_host_private = kex->load_host_private_key(kex->hostkey_type);
/* key, cert */
if ((dh_client_pub = BN_new()) == NULL)
fatal("dh_client_pub == NULL");
packet_get_bignum2(dh_client_pub);
packet_check_eom();
#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, dh);
fprintf(stderr, "pub= ");
BN_print_fp(stderr, dh->pub_key);
fprintf(stderr, "\n");
#endif
if (!dh_pub_is_valid(dh, dh_client_pub))
packet_disconnect("bad client public DH value");
klen = DH_size(dh);
kbuf = xmalloc(klen);
if ((kout = DH_compute_key(kbuf, dh_client_pub, dh)) < 0)
fatal("DH_compute_key: failed");
#ifdef DEBUG_KEXDH
dump_digest("shared secret", kbuf, kout);
#endif
if ((shared_secret = BN_new()) == NULL)
fatal("kexdh_server: BN_new failed");
if (BN_bin2bn(kbuf, kout, shared_secret) == NULL)
fatal("kexdh_server: BN_bin2bn failed");
memset(kbuf, 0, klen);
free(kbuf);
key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
/* calc H */
kex_dh_hash(
kex->client_version_string,
kex->server_version_string,
buffer_ptr(&kex->peer), buffer_len(&kex->peer),
buffer_ptr(&kex->my), buffer_len(&kex->my),
server_host_key_blob, sbloblen,
dh_client_pub,
dh->pub_key,
shared_secret,
&hash, &hashlen
);
BN_clear_free(dh_client_pub);
/* save session id := H */
if (kex->session_id == NULL) {
kex->session_id_len = hashlen;
kex->session_id = xmalloc(kex->session_id_len);
memcpy(kex->session_id, hash, kex->session_id_len);
}
/* sign H */
kex->sign(server_host_private, server_host_public, &signature, &slen,
hash, hashlen);
/* destroy_sensitive_data(); */
/* send server hostkey, DH pubkey 'f' and singed H */
packet_start(SSH2_MSG_KEXDH_REPLY);
packet_put_string(server_host_key_blob, sbloblen);
packet_put_bignum2(dh->pub_key); /* f */
packet_put_string(signature, slen);
packet_send();
free(signature);
free(server_host_key_blob);
/* have keys, free DH */
DH_free(dh);
kex_derive_keys_bn(kex, hash, hashlen, shared_secret);
BN_clear_free(shared_secret);
kex_finish(kex);
}
