Annotation of src/usr.bin/ssh/kexdhc.c, Revision 1.1
1.1 ! markus 1: /*
! 2: * Copyright (c) 2001 Markus Friedl. All rights reserved.
! 3: *
! 4: * Redistribution and use in source and binary forms, with or without
! 5: * modification, are permitted provided that the following conditions
! 6: * are met:
! 7: * 1. Redistributions of source code must retain the above copyright
! 8: * notice, this list of conditions and the following disclaimer.
! 9: * 2. Redistributions in binary form must reproduce the above copyright
! 10: * notice, this list of conditions and the following disclaimer in the
! 11: * documentation and/or other materials provided with the distribution.
! 12: *
! 13: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
! 14: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
! 15: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
! 16: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
! 17: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
! 18: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
! 19: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
! 20: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
! 21: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
! 22: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
! 23: */
! 24:
! 25: #include "includes.h"
! 26: RCSID("$OpenBSD: kexdh.c,v 1.18 2002/03/18 17:50:31 provos Exp $");
! 27:
! 28: #include "xmalloc.h"
! 29: #include "key.h"
! 30: #include "kex.h"
! 31: #include "log.h"
! 32: #include "packet.h"
! 33: #include "dh.h"
! 34: #include "ssh2.h"
! 35:
! 36: void
! 37: kexdh_client(Kex *kex)
! 38: {
! 39: BIGNUM *dh_server_pub = NULL, *shared_secret = NULL;
! 40: DH *dh;
! 41: Key *server_host_key;
! 42: u_char *server_host_key_blob = NULL, *signature = NULL;
! 43: u_char *kbuf, *hash;
! 44: u_int klen, kout, slen, sbloblen;
! 45:
! 46: /* generate and send 'e', client DH public key */
! 47: dh = dh_new_group1();
! 48: dh_gen_key(dh, kex->we_need * 8);
! 49: packet_start(SSH2_MSG_KEXDH_INIT);
! 50: packet_put_bignum2(dh->pub_key);
! 51: packet_send();
! 52:
! 53: debug("sending SSH2_MSG_KEXDH_INIT");
! 54: #ifdef DEBUG_KEXDH
! 55: DHparams_print_fp(stderr, dh);
! 56: fprintf(stderr, "pub= ");
! 57: BN_print_fp(stderr, dh->pub_key);
! 58: fprintf(stderr, "\n");
! 59: #endif
! 60:
! 61: debug("expecting SSH2_MSG_KEXDH_REPLY");
! 62: packet_read_expect(SSH2_MSG_KEXDH_REPLY);
! 63:
! 64: /* key, cert */
! 65: server_host_key_blob = packet_get_string(&sbloblen);
! 66: server_host_key = key_from_blob(server_host_key_blob, sbloblen);
! 67: if (server_host_key == NULL)
! 68: fatal("cannot decode server_host_key_blob");
! 69: if (server_host_key->type != kex->hostkey_type)
! 70: fatal("type mismatch for decoded server_host_key_blob");
! 71: if (kex->verify_host_key == NULL)
! 72: fatal("cannot verify server_host_key");
! 73: if (kex->verify_host_key(server_host_key) == -1)
! 74: fatal("server_host_key verification failed");
! 75:
! 76: /* DH paramter f, server public DH key */
! 77: if ((dh_server_pub = BN_new()) == NULL)
! 78: fatal("dh_server_pub == NULL");
! 79: packet_get_bignum2(dh_server_pub);
! 80:
! 81: #ifdef DEBUG_KEXDH
! 82: fprintf(stderr, "dh_server_pub= ");
! 83: BN_print_fp(stderr, dh_server_pub);
! 84: fprintf(stderr, "\n");
! 85: debug("bits %d", BN_num_bits(dh_server_pub));
! 86: #endif
! 87:
! 88: /* signed H */
! 89: signature = packet_get_string(&slen);
! 90: packet_check_eom();
! 91:
! 92: if (!dh_pub_is_valid(dh, dh_server_pub))
! 93: packet_disconnect("bad server public DH value");
! 94:
! 95: klen = DH_size(dh);
! 96: kbuf = xmalloc(klen);
! 97: kout = DH_compute_key(kbuf, dh_server_pub, dh);
! 98: #ifdef DEBUG_KEXDH
! 99: dump_digest("shared secret", kbuf, kout);
! 100: #endif
! 101: if ((shared_secret = BN_new()) == NULL)
! 102: fatal("kexdh_client: BN_new failed");
! 103: BN_bin2bn(kbuf, kout, shared_secret);
! 104: memset(kbuf, 0, klen);
! 105: xfree(kbuf);
! 106:
! 107: /* calc and verify H */
! 108: hash = kex_dh_hash(
! 109: kex->client_version_string,
! 110: kex->server_version_string,
! 111: buffer_ptr(&kex->my), buffer_len(&kex->my),
! 112: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
! 113: server_host_key_blob, sbloblen,
! 114: dh->pub_key,
! 115: dh_server_pub,
! 116: shared_secret
! 117: );
! 118: xfree(server_host_key_blob);
! 119: BN_clear_free(dh_server_pub);
! 120: DH_free(dh);
! 121:
! 122: if (key_verify(server_host_key, signature, slen, hash, 20) != 1)
! 123: fatal("key_verify failed for server_host_key");
! 124: key_free(server_host_key);
! 125: xfree(signature);
! 126:
! 127: /* save session id */
! 128: if (kex->session_id == NULL) {
! 129: kex->session_id_len = 20;
! 130: kex->session_id = xmalloc(kex->session_id_len);
! 131: memcpy(kex->session_id, hash, kex->session_id_len);
! 132: }
! 133:
! 134: kex_derive_keys(kex, hash, shared_secret);
! 135: BN_clear_free(shared_secret);
! 136: kex_finish(kex);
! 137: }
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