diff options
Diffstat (limited to 'usr.bin/ssh/sshconnect2.c')
| -rw-r--r-- | usr.bin/ssh/sshconnect2.c | 299 |
1 files changed, 243 insertions, 56 deletions
diff --git a/usr.bin/ssh/sshconnect2.c b/usr.bin/ssh/sshconnect2.c index eee09a19ca8..455850eebc6 100644 --- a/usr.bin/ssh/sshconnect2.c +++ b/usr.bin/ssh/sshconnect2.c @@ -23,7 +23,7 @@ */ #include "includes.h" -RCSID("$OpenBSD: sshconnect2.c,v 1.21 2000/09/27 21:41:34 markus Exp $"); +RCSID("$OpenBSD: sshconnect2.c,v 1.22 2000/10/11 04:02:17 provos Exp $"); #include <openssl/bn.h> #include <openssl/rsa.h> @@ -52,6 +52,9 @@ RCSID("$OpenBSD: sshconnect2.c,v 1.21 2000/09/27 21:41:34 markus Exp $"); #include "dispatch.h" #include "authfd.h" +void ssh_dh1_client(Kex *, char *, struct sockaddr *, Buffer *, Buffer *); +void ssh_dhgex_client(Kex *, char *, struct sockaddr *, Buffer *, Buffer *); + /* import */ extern char *client_version_string; extern char *server_version_string; @@ -65,8 +68,89 @@ unsigned char *session_id2 = NULL; int session_id2_len = 0; void -ssh_kex_dh(Kex *kex, char *host, struct sockaddr *hostaddr, - Buffer *client_kexinit, Buffer *server_kexinit) +ssh_kex2(char *host, struct sockaddr *hostaddr) +{ + int i, plen; + Kex *kex; + Buffer *client_kexinit, *server_kexinit; + char *sprop[PROPOSAL_MAX]; + + if (options.ciphers != NULL) { + myproposal[PROPOSAL_ENC_ALGS_CTOS] = + myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; + } else if (options.cipher == SSH_CIPHER_3DES) { + myproposal[PROPOSAL_ENC_ALGS_CTOS] = + myproposal[PROPOSAL_ENC_ALGS_STOC] = + (char *) cipher_name(SSH_CIPHER_3DES_CBC); + } else if (options.cipher == SSH_CIPHER_BLOWFISH) { + myproposal[PROPOSAL_ENC_ALGS_CTOS] = + myproposal[PROPOSAL_ENC_ALGS_STOC] = + (char *) cipher_name(SSH_CIPHER_BLOWFISH_CBC); + } + if (options.compression) { + myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib"; + myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib"; + } else { + myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none"; + myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; + } + + /* buffers with raw kexinit messages */ + server_kexinit = xmalloc(sizeof(*server_kexinit)); + buffer_init(server_kexinit); + client_kexinit = kex_init(myproposal); + + /* algorithm negotiation */ + kex_exchange_kexinit(client_kexinit, server_kexinit, sprop); + kex = kex_choose_conf(myproposal, sprop, 0); + for (i = 0; i < PROPOSAL_MAX; i++) + xfree(sprop[i]); + + /* server authentication and session key agreement */ + switch(kex->kex_type) { + case DH_GRP1_SHA1: + ssh_dh1_client(kex, host, hostaddr, + client_kexinit, server_kexinit); + break; + case DH_GEX_SHA1: + ssh_dhgex_client(kex, host, hostaddr, client_kexinit, + server_kexinit); + break; + default: + fatal("Unsupported key exchange %d", kex->kex_type); + } + + buffer_free(client_kexinit); + buffer_free(server_kexinit); + xfree(client_kexinit); + xfree(server_kexinit); + + debug("Wait SSH2_MSG_NEWKEYS."); + packet_read_expect(&plen, SSH2_MSG_NEWKEYS); + packet_done(); + debug("GOT SSH2_MSG_NEWKEYS."); + + debug("send SSH2_MSG_NEWKEYS."); + packet_start(SSH2_MSG_NEWKEYS); + packet_send(); + packet_write_wait(); + debug("done: send SSH2_MSG_NEWKEYS."); + +#ifdef DEBUG_KEXDH + /* send 1st encrypted/maced/compressed message */ + packet_start(SSH2_MSG_IGNORE); + packet_put_cstring("markus"); + packet_send(); + packet_write_wait(); +#endif + debug("done: KEX2."); +} + +/* diffie-hellman-group1-sha1 */ + +void +ssh_dh1_client(Kex *kex, char *host, struct sockaddr *hostaddr, + Buffer *client_kexinit, Buffer *server_kexinit) { #ifdef DEBUG_KEXDH int i; @@ -116,7 +200,7 @@ ssh_kex_dh(Kex *kex, char *host, struct sockaddr *hostaddr, fatal("cannot decode server_host_key_blob"); check_host_key(host, hostaddr, server_host_key, - options.user_hostfile2, options.system_hostfile2); + options.user_hostfile2, options.system_hostfile2); /* DH paramter f, server public DH key */ dh_server_pub = BN_new(); @@ -186,72 +270,175 @@ ssh_kex_dh(Kex *kex, char *host, struct sockaddr *hostaddr, memcpy(session_id2, hash, session_id2_len); } +/* diffie-hellman-group-exchange-sha1 */ + +/* + * Estimates the group order for a Diffie-Hellman group that has an + * attack complexity approximately the same as O(2**bits). Estimate + * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3))) + */ + +int +dh_estimate(int bits) +{ + + if (bits < 64) + return (512); /* O(2**63) */ + if (bits < 128) + return (1024); /* O(2**86) */ + if (bits < 192) + return (2048); /* O(2**116) */ + return (4096); /* O(2**156) */ +} + void -ssh_kex2(char *host, struct sockaddr *hostaddr) +ssh_dhgex_client(Kex *kex, char *host, struct sockaddr *hostaddr, + Buffer *client_kexinit, Buffer *server_kexinit) { - int i, plen; - Kex *kex; - Buffer *client_kexinit, *server_kexinit; - char *sprop[PROPOSAL_MAX]; +#ifdef DEBUG_KEXDH + int i; +#endif + int plen, dlen; + unsigned int klen, kout; + char *signature = NULL; + unsigned int slen, nbits; + char *server_host_key_blob = NULL; + Key *server_host_key; + unsigned int sbloblen; + DH *dh; + BIGNUM *dh_server_pub = 0; + BIGNUM *shared_secret = 0; + BIGNUM *p = 0, *g = 0; + unsigned char *kbuf; + unsigned char *hash; - if (options.ciphers != NULL) { - myproposal[PROPOSAL_ENC_ALGS_CTOS] = - myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; - } else if (options.cipher == SSH_CIPHER_3DES) { - myproposal[PROPOSAL_ENC_ALGS_CTOS] = - myproposal[PROPOSAL_ENC_ALGS_STOC] = - (char *) cipher_name(SSH_CIPHER_3DES_CBC); - } else if (options.cipher == SSH_CIPHER_BLOWFISH) { - myproposal[PROPOSAL_ENC_ALGS_CTOS] = - myproposal[PROPOSAL_ENC_ALGS_STOC] = - (char *) cipher_name(SSH_CIPHER_BLOWFISH_CBC); - } - if (options.compression) { - myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib"; - myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib"; - } else { - myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none"; - myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; - } + nbits = dh_estimate(kex->enc[MODE_OUT].key_len * 8); - /* buffers with raw kexinit messages */ - server_kexinit = xmalloc(sizeof(*server_kexinit)); - buffer_init(server_kexinit); - client_kexinit = kex_init(myproposal); + debug("Sending SSH2_MSG_KEX_DH_GEX_REQUEST."); + packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST); + packet_put_int(nbits); + packet_send(); + packet_write_wait(); - /* algorithm negotiation */ - kex_exchange_kexinit(client_kexinit, server_kexinit, sprop); - kex = kex_choose_conf(myproposal, sprop, 0); - for (i = 0; i < PROPOSAL_MAX; i++) - xfree(sprop[i]); +#ifdef DEBUG_KEXDH + fprintf(stderr, "\nnbits = %d", nbits); +#endif - /* server authentication and session key agreement */ - ssh_kex_dh(kex, host, hostaddr, client_kexinit, server_kexinit); + debug("Wait SSH2_MSG_KEX_DH_GEX_GROUP."); - buffer_free(client_kexinit); - buffer_free(server_kexinit); - xfree(client_kexinit); - xfree(server_kexinit); + packet_read_expect(&plen, SSH2_MSG_KEX_DH_GEX_GROUP); - debug("Wait SSH2_MSG_NEWKEYS."); - packet_read_expect(&plen, SSH2_MSG_NEWKEYS); - packet_done(); - debug("GOT SSH2_MSG_NEWKEYS."); + debug("Got SSH2_MSG_KEX_DH_GEX_GROUP."); - debug("send SSH2_MSG_NEWKEYS."); - packet_start(SSH2_MSG_NEWKEYS); - packet_send(); - packet_write_wait(); - debug("done: send SSH2_MSG_NEWKEYS."); + if ((p = BN_new()) == NULL) + fatal("BN_new"); + packet_get_bignum2(p, &dlen); + if ((g = BN_new()) == NULL) + fatal("BN_new"); + packet_get_bignum2(g, &dlen); + if ((dh = dh_new_group(g, p)) == NULL) + fatal("dh_new_group"); #ifdef DEBUG_KEXDH - /* send 1st encrypted/maced/compressed message */ - packet_start(SSH2_MSG_IGNORE); - packet_put_cstring("markus"); + fprintf(stderr, "\np= "); + BN_print_fp(stderr, dh->p); + fprintf(stderr, "\ng= "); + BN_print_fp(stderr, dh->g); + fprintf(stderr, "\npub= "); + BN_print_fp(stderr, dh->pub_key); + fprintf(stderr, "\n"); + DHparams_print_fp(stderr, dh); +#endif + + debug("Sending SSH2_MSG_KEX_DH_GEX_INIT."); + /* generate and send 'e', client DH public key */ + packet_start(SSH2_MSG_KEX_DH_GEX_INIT); + packet_put_bignum2(dh->pub_key); packet_send(); packet_write_wait(); + + debug("Wait SSH2_MSG_KEX_DH_GEX_REPLY."); + + packet_read_expect(&plen, SSH2_MSG_KEX_DH_GEX_REPLY); + + debug("Got SSH2_MSG_KEXDH_REPLY."); + + /* key, cert */ + server_host_key_blob = packet_get_string(&sbloblen); + server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen); + if (server_host_key == NULL) + fatal("cannot decode server_host_key_blob"); + + check_host_key(host, hostaddr, server_host_key, + options.user_hostfile2, options.system_hostfile2); + + /* DH paramter f, server public DH key */ + dh_server_pub = BN_new(); + if (dh_server_pub == NULL) + fatal("dh_server_pub == NULL"); + packet_get_bignum2(dh_server_pub, &dlen); + +#ifdef DEBUG_KEXDH + fprintf(stderr, "\ndh_server_pub= "); + BN_print_fp(stderr, dh_server_pub); + fprintf(stderr, "\n"); + debug("bits %d", BN_num_bits(dh_server_pub)); #endif - debug("done: KEX2."); + + /* signed H */ + signature = packet_get_string(&slen); + packet_done(); + + 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 + debug("shared secret: len %d/%d", klen, kout); + fprintf(stderr, "shared secret == "); + for (i = 0; i< kout; i++) + fprintf(stderr, "%02x", (kbuf[i])&0xff); + fprintf(stderr, "\n"); +#endif + shared_secret = BN_new(); + + BN_bin2bn(kbuf, kout, shared_secret); + memset(kbuf, 0, klen); + xfree(kbuf); + + /* calc and verify H */ + hash = kex_hash_gex( + client_version_string, + server_version_string, + buffer_ptr(client_kexinit), buffer_len(client_kexinit), + buffer_ptr(server_kexinit), buffer_len(server_kexinit), + server_host_key_blob, sbloblen, + nbits, dh->p, dh->g, + dh->pub_key, + dh_server_pub, + shared_secret + ); + xfree(server_host_key_blob); + DH_free(dh); +#ifdef DEBUG_KEXDH + fprintf(stderr, "hash == "); + for (i = 0; i< 20; i++) + fprintf(stderr, "%02x", (hash[i])&0xff); + fprintf(stderr, "\n"); +#endif + if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1) + fatal("dsa_verify failed for server_host_key"); + key_free(server_host_key); + + kex_derive_keys(kex, hash, shared_secret); + packet_set_kex(kex); + + /* save session id */ + session_id2_len = 20; + session_id2 = xmalloc(session_id2_len); + memcpy(session_id2, hash, session_id2_len); } /* |