version 1.22, 2002/03/24 17:27:03 |
version 1.23, 2003/02/16 17:09:57 |
|
|
#include "includes.h" |
#include "includes.h" |
RCSID("$OpenBSD$"); |
RCSID("$OpenBSD$"); |
|
|
#include <openssl/bn.h> |
#include <openssl/evp.h> |
|
|
#include "xmalloc.h" |
|
#include "buffer.h" |
#include "buffer.h" |
#include "bufaux.h" |
#include "bufaux.h" |
#include "key.h" |
|
#include "kex.h" |
#include "kex.h" |
#include "log.h" |
|
#include "packet.h" |
|
#include "dh.h" |
|
#include "ssh2.h" |
#include "ssh2.h" |
#include "compat.h" |
|
#include "monitor_wrap.h" |
|
|
|
static u_char * |
u_char * |
kexgex_hash( |
kexgex_hash( |
char *client_version_string, |
char *client_version_string, |
char *server_version_string, |
char *server_version_string, |
|
|
dump_digest("hash", digest, EVP_MD_size(evp_md)); |
dump_digest("hash", digest, EVP_MD_size(evp_md)); |
#endif |
#endif |
return digest; |
return digest; |
} |
|
|
|
/* client */ |
|
|
|
static 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); |
|
} |
|
|
|
/* server */ |
|
|
|
static void |
|
kexgex_server(Kex *kex) |
|
{ |
|
BIGNUM *shared_secret = NULL, *dh_client_pub = NULL; |
|
Key *server_host_key; |
|
DH *dh; |
|
u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL; |
|
u_int sbloblen, klen, kout, slen; |
|
int min = -1, max = -1, nbits = -1, type; |
|
|
|
if (kex->load_host_key == NULL) |
|
fatal("Cannot load hostkey"); |
|
server_host_key = kex->load_host_key(kex->hostkey_type); |
|
if (server_host_key == NULL) |
|
fatal("Unsupported 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"); |
|
min = packet_get_int(); |
|
nbits = packet_get_int(); |
|
max = packet_get_int(); |
|
min = MAX(DH_GRP_MIN, min); |
|
max = MIN(DH_GRP_MAX, max); |
|
break; |
|
case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD: |
|
debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received"); |
|
nbits = packet_get_int(); |
|
min = DH_GRP_MIN; |
|
max = DH_GRP_MAX; |
|
/* unused for old GEX */ |
|
break; |
|
default: |
|
fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type); |
|
} |
|
packet_check_eom(); |
|
|
|
if (max < min || nbits < min || max < nbits) |
|
fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d", |
|
min, nbits, max); |
|
|
|
/* 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); |
|
kout = DH_compute_key(kbuf, dh_client_pub, dh); |
|
#ifdef DEBUG_KEXDH |
|
dump_digest("shared secret", kbuf, kout); |
|
#endif |
|
if ((shared_secret = BN_new()) == NULL) |
|
fatal("kexgex_server: BN_new failed"); |
|
BN_bin2bn(kbuf, kout, shared_secret); |
|
memset(kbuf, 0, klen); |
|
xfree(kbuf); |
|
|
|
key_to_blob(server_host_key, &server_host_key_blob, &sbloblen); |
|
|
|
if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD) |
|
min = max = -1; |
|
|
|
/* calc H */ /* XXX depends on 'kex' */ |
|
hash = kexgex_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, |
|
min, nbits, max, |
|
dh->p, dh->g, |
|
dh_client_pub, |
|
dh->pub_key, |
|
shared_secret |
|
); |
|
BN_clear_free(dh_client_pub); |
|
|
|
/* save session id := H */ |
|
/* XXX hashlen depends on KEX */ |
|
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); |
|
} |
|
|
|
/* sign H */ |
|
/* XXX hashlen depends on KEX */ |
|
PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20)); |
|
|
|
/* 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, shared_secret); |
|
BN_clear_free(shared_secret); |
|
|
|
kex_finish(kex); |
|
} |
|
|
|
void |
|
kexgex(Kex *kex) |
|
{ |
|
if (kex->server) |
|
kexgex_server(kex); |
|
else |
|
kexgex_client(kex); |
|
} |
} |