Annotation of src/usr.bin/ssh/kexdhs.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: #include "monitor_wrap.h"
! 36:
! 37: void
! 38: kexdh_server(Kex *kex)
! 39: {
! 40: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
! 41: DH *dh;
! 42: Key *server_host_key;
! 43: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
! 44: u_int sbloblen, klen, kout;
! 45: u_int slen;
! 46:
! 47: /* generate server DH public key */
! 48: dh = dh_new_group1();
! 49: dh_gen_key(dh, kex->we_need * 8);
! 50:
! 51: debug("expecting SSH2_MSG_KEXDH_INIT");
! 52: packet_read_expect(SSH2_MSG_KEXDH_INIT);
! 53:
! 54: if (kex->load_host_key == NULL)
! 55: fatal("Cannot load hostkey");
! 56: server_host_key = kex->load_host_key(kex->hostkey_type);
! 57: if (server_host_key == NULL)
! 58: fatal("Unsupported hostkey type %d", kex->hostkey_type);
! 59:
! 60: /* key, cert */
! 61: if ((dh_client_pub = BN_new()) == NULL)
! 62: fatal("dh_client_pub == NULL");
! 63: packet_get_bignum2(dh_client_pub);
! 64: packet_check_eom();
! 65:
! 66: #ifdef DEBUG_KEXDH
! 67: fprintf(stderr, "dh_client_pub= ");
! 68: BN_print_fp(stderr, dh_client_pub);
! 69: fprintf(stderr, "\n");
! 70: debug("bits %d", BN_num_bits(dh_client_pub));
! 71: #endif
! 72:
! 73: #ifdef DEBUG_KEXDH
! 74: DHparams_print_fp(stderr, dh);
! 75: fprintf(stderr, "pub= ");
! 76: BN_print_fp(stderr, dh->pub_key);
! 77: fprintf(stderr, "\n");
! 78: #endif
! 79: if (!dh_pub_is_valid(dh, dh_client_pub))
! 80: packet_disconnect("bad client public DH value");
! 81:
! 82: klen = DH_size(dh);
! 83: kbuf = xmalloc(klen);
! 84: kout = DH_compute_key(kbuf, dh_client_pub, dh);
! 85: #ifdef DEBUG_KEXDH
! 86: dump_digest("shared secret", kbuf, kout);
! 87: #endif
! 88: if ((shared_secret = BN_new()) == NULL)
! 89: fatal("kexdh_server: BN_new failed");
! 90: BN_bin2bn(kbuf, kout, shared_secret);
! 91: memset(kbuf, 0, klen);
! 92: xfree(kbuf);
! 93:
! 94: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
! 95:
! 96: /* calc H */
! 97: hash = kex_dh_hash(
! 98: kex->client_version_string,
! 99: kex->server_version_string,
! 100: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
! 101: buffer_ptr(&kex->my), buffer_len(&kex->my),
! 102: server_host_key_blob, sbloblen,
! 103: dh_client_pub,
! 104: dh->pub_key,
! 105: shared_secret
! 106: );
! 107: BN_clear_free(dh_client_pub);
! 108:
! 109: /* save session id := H */
! 110: /* XXX hashlen depends on KEX */
! 111: if (kex->session_id == NULL) {
! 112: kex->session_id_len = 20;
! 113: kex->session_id = xmalloc(kex->session_id_len);
! 114: memcpy(kex->session_id, hash, kex->session_id_len);
! 115: }
! 116:
! 117: /* sign H */
! 118: /* XXX hashlen depends on KEX */
! 119: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
! 120:
! 121: /* destroy_sensitive_data(); */
! 122:
! 123: /* send server hostkey, DH pubkey 'f' and singed H */
! 124: packet_start(SSH2_MSG_KEXDH_REPLY);
! 125: packet_put_string(server_host_key_blob, sbloblen);
! 126: packet_put_bignum2(dh->pub_key); /* f */
! 127: packet_put_string(signature, slen);
! 128: packet_send();
! 129:
! 130: xfree(signature);
! 131: xfree(server_host_key_blob);
! 132: /* have keys, free DH */
! 133: DH_free(dh);
! 134:
! 135: kex_derive_keys(kex, hash, shared_secret);
! 136: BN_clear_free(shared_secret);
! 137: kex_finish(kex);
! 138: }