Annotation of src/usr.bin/ssh/kexgexc.c, Revision 1.1
1.1 ! markus 1: /*
! 2: * Copyright (c) 2000 Niels Provos. All rights reserved.
! 3: * Copyright (c) 2001 Markus Friedl. All rights reserved.
! 4: *
! 5: * Redistribution and use in source and binary forms, with or without
! 6: * modification, are permitted provided that the following conditions
! 7: * are met:
! 8: * 1. Redistributions of source code must retain the above copyright
! 9: * notice, this list of conditions and the following disclaimer.
! 10: * 2. Redistributions in binary form must reproduce the above copyright
! 11: * notice, this list of conditions and the following disclaimer in the
! 12: * documentation and/or other materials provided with the distribution.
! 13: *
! 14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
! 15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
! 16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
! 17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
! 18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
! 19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
! 20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
! 21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
! 22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
! 23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
! 24: */
! 25:
! 26: #include "includes.h"
! 27: RCSID("$OpenBSD: kexgex.c,v 1.22 2002/03/24 17:27:03 stevesk Exp $");
! 28:
! 29: #include "xmalloc.h"
! 30: #include "key.h"
! 31: #include "kex.h"
! 32: #include "log.h"
! 33: #include "packet.h"
! 34: #include "dh.h"
! 35: #include "ssh2.h"
! 36: #include "compat.h"
! 37:
! 38: void
! 39: kexgex_client(Kex *kex)
! 40: {
! 41: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
! 42: BIGNUM *p = NULL, *g = NULL;
! 43: Key *server_host_key;
! 44: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
! 45: u_int klen, kout, slen, sbloblen;
! 46: int min, max, nbits;
! 47: DH *dh;
! 48:
! 49: nbits = dh_estimate(kex->we_need * 8);
! 50:
! 51: if (datafellows & SSH_OLD_DHGEX) {
! 52: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD sent");
! 53:
! 54: /* Old GEX request */
! 55: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
! 56: packet_put_int(nbits);
! 57: min = DH_GRP_MIN;
! 58: max = DH_GRP_MAX;
! 59: } else {
! 60: debug("SSH2_MSG_KEX_DH_GEX_REQUEST sent");
! 61:
! 62: /* New GEX request */
! 63: min = DH_GRP_MIN;
! 64: max = DH_GRP_MAX;
! 65: packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
! 66: packet_put_int(min);
! 67: packet_put_int(nbits);
! 68: packet_put_int(max);
! 69: }
! 70: #ifdef DEBUG_KEXDH
! 71: fprintf(stderr, "\nmin = %d, nbits = %d, max = %d\n",
! 72: min, nbits, max);
! 73: #endif
! 74: packet_send();
! 75:
! 76: debug("expecting SSH2_MSG_KEX_DH_GEX_GROUP");
! 77: packet_read_expect(SSH2_MSG_KEX_DH_GEX_GROUP);
! 78:
! 79: if ((p = BN_new()) == NULL)
! 80: fatal("BN_new");
! 81: packet_get_bignum2(p);
! 82: if ((g = BN_new()) == NULL)
! 83: fatal("BN_new");
! 84: packet_get_bignum2(g);
! 85: packet_check_eom();
! 86:
! 87: if (BN_num_bits(p) < min || BN_num_bits(p) > max)
! 88: fatal("DH_GEX group out of range: %d !< %d !< %d",
! 89: min, BN_num_bits(p), max);
! 90:
! 91: dh = dh_new_group(g, p);
! 92: dh_gen_key(dh, kex->we_need * 8);
! 93:
! 94: #ifdef DEBUG_KEXDH
! 95: DHparams_print_fp(stderr, dh);
! 96: fprintf(stderr, "pub= ");
! 97: BN_print_fp(stderr, dh->pub_key);
! 98: fprintf(stderr, "\n");
! 99: #endif
! 100:
! 101: debug("SSH2_MSG_KEX_DH_GEX_INIT sent");
! 102: /* generate and send 'e', client DH public key */
! 103: packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
! 104: packet_put_bignum2(dh->pub_key);
! 105: packet_send();
! 106:
! 107: debug("expecting SSH2_MSG_KEX_DH_GEX_REPLY");
! 108: packet_read_expect(SSH2_MSG_KEX_DH_GEX_REPLY);
! 109:
! 110: /* key, cert */
! 111: server_host_key_blob = packet_get_string(&sbloblen);
! 112: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
! 113: if (server_host_key == NULL)
! 114: fatal("cannot decode server_host_key_blob");
! 115: if (server_host_key->type != kex->hostkey_type)
! 116: fatal("type mismatch for decoded server_host_key_blob");
! 117: if (kex->verify_host_key == NULL)
! 118: fatal("cannot verify server_host_key");
! 119: if (kex->verify_host_key(server_host_key) == -1)
! 120: fatal("server_host_key verification failed");
! 121:
! 122: /* DH paramter f, server public DH key */
! 123: if ((dh_server_pub = BN_new()) == NULL)
! 124: fatal("dh_server_pub == NULL");
! 125: packet_get_bignum2(dh_server_pub);
! 126:
! 127: #ifdef DEBUG_KEXDH
! 128: fprintf(stderr, "dh_server_pub= ");
! 129: BN_print_fp(stderr, dh_server_pub);
! 130: fprintf(stderr, "\n");
! 131: debug("bits %d", BN_num_bits(dh_server_pub));
! 132: #endif
! 133:
! 134: /* signed H */
! 135: signature = packet_get_string(&slen);
! 136: packet_check_eom();
! 137:
! 138: if (!dh_pub_is_valid(dh, dh_server_pub))
! 139: packet_disconnect("bad server public DH value");
! 140:
! 141: klen = DH_size(dh);
! 142: kbuf = xmalloc(klen);
! 143: kout = DH_compute_key(kbuf, dh_server_pub, dh);
! 144: #ifdef DEBUG_KEXDH
! 145: dump_digest("shared secret", kbuf, kout);
! 146: #endif
! 147: if ((shared_secret = BN_new()) == NULL)
! 148: fatal("kexgex_client: BN_new failed");
! 149: BN_bin2bn(kbuf, kout, shared_secret);
! 150: memset(kbuf, 0, klen);
! 151: xfree(kbuf);
! 152:
! 153: if (datafellows & SSH_OLD_DHGEX)
! 154: min = max = -1;
! 155:
! 156: /* calc and verify H */
! 157: hash = kexgex_hash(
! 158: kex->client_version_string,
! 159: kex->server_version_string,
! 160: buffer_ptr(&kex->my), buffer_len(&kex->my),
! 161: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
! 162: server_host_key_blob, sbloblen,
! 163: min, nbits, max,
! 164: dh->p, dh->g,
! 165: dh->pub_key,
! 166: dh_server_pub,
! 167: shared_secret
! 168: );
! 169: /* have keys, free DH */
! 170: DH_free(dh);
! 171: xfree(server_host_key_blob);
! 172: BN_clear_free(dh_server_pub);
! 173:
! 174: if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
! 175: fatal("key_verify failed for server_host_key");
! 176: key_free(server_host_key);
! 177: xfree(signature);
! 178:
! 179: /* save session id */
! 180: if (kex->session_id == NULL) {
! 181: kex->session_id_len = 20;
! 182: kex->session_id = xmalloc(kex->session_id_len);
! 183: memcpy(kex->session_id, hash, kex->session_id_len);
! 184: }
! 185: kex_derive_keys(kex, hash, shared_secret);
! 186: BN_clear_free(shared_secret);
! 187:
! 188: kex_finish(kex);
! 189: }
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