Annotation of src/usr.bin/ssh/kexgexs.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: #include "monitor_wrap.h"
! 38:
! 39: void
! 40: kexgex_server(Kex *kex)
! 41: {
! 42: BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
! 43: Key *server_host_key;
! 44: DH *dh;
! 45: u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
! 46: u_int sbloblen, klen, kout, slen;
! 47: int min = -1, max = -1, nbits = -1, type;
! 48:
! 49: if (kex->load_host_key == NULL)
! 50: fatal("Cannot load hostkey");
! 51: server_host_key = kex->load_host_key(kex->hostkey_type);
! 52: if (server_host_key == NULL)
! 53: fatal("Unsupported hostkey type %d", kex->hostkey_type);
! 54:
! 55: type = packet_read();
! 56: switch (type) {
! 57: case SSH2_MSG_KEX_DH_GEX_REQUEST:
! 58: debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
! 59: min = packet_get_int();
! 60: nbits = packet_get_int();
! 61: max = packet_get_int();
! 62: min = MAX(DH_GRP_MIN, min);
! 63: max = MIN(DH_GRP_MAX, max);
! 64: break;
! 65: case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
! 66: debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
! 67: nbits = packet_get_int();
! 68: min = DH_GRP_MIN;
! 69: max = DH_GRP_MAX;
! 70: /* unused for old GEX */
! 71: break;
! 72: default:
! 73: fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
! 74: }
! 75: packet_check_eom();
! 76:
! 77: if (max < min || nbits < min || max < nbits)
! 78: fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
! 79: min, nbits, max);
! 80:
! 81: /* Contact privileged parent */
! 82: dh = PRIVSEP(choose_dh(min, nbits, max));
! 83: if (dh == NULL)
! 84: packet_disconnect("Protocol error: no matching DH grp found");
! 85:
! 86: debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
! 87: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
! 88: packet_put_bignum2(dh->p);
! 89: packet_put_bignum2(dh->g);
! 90: packet_send();
! 91:
! 92: /* flush */
! 93: packet_write_wait();
! 94:
! 95: /* Compute our exchange value in parallel with the client */
! 96: dh_gen_key(dh, kex->we_need * 8);
! 97:
! 98: debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
! 99: packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
! 100:
! 101: /* key, cert */
! 102: if ((dh_client_pub = BN_new()) == NULL)
! 103: fatal("dh_client_pub == NULL");
! 104: packet_get_bignum2(dh_client_pub);
! 105: packet_check_eom();
! 106:
! 107: #ifdef DEBUG_KEXDH
! 108: fprintf(stderr, "dh_client_pub= ");
! 109: BN_print_fp(stderr, dh_client_pub);
! 110: fprintf(stderr, "\n");
! 111: debug("bits %d", BN_num_bits(dh_client_pub));
! 112: #endif
! 113:
! 114: #ifdef DEBUG_KEXDH
! 115: DHparams_print_fp(stderr, dh);
! 116: fprintf(stderr, "pub= ");
! 117: BN_print_fp(stderr, dh->pub_key);
! 118: fprintf(stderr, "\n");
! 119: #endif
! 120: if (!dh_pub_is_valid(dh, dh_client_pub))
! 121: packet_disconnect("bad client public DH value");
! 122:
! 123: klen = DH_size(dh);
! 124: kbuf = xmalloc(klen);
! 125: kout = DH_compute_key(kbuf, dh_client_pub, dh);
! 126: #ifdef DEBUG_KEXDH
! 127: dump_digest("shared secret", kbuf, kout);
! 128: #endif
! 129: if ((shared_secret = BN_new()) == NULL)
! 130: fatal("kexgex_server: BN_new failed");
! 131: BN_bin2bn(kbuf, kout, shared_secret);
! 132: memset(kbuf, 0, klen);
! 133: xfree(kbuf);
! 134:
! 135: key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
! 136:
! 137: if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
! 138: min = max = -1;
! 139:
! 140: /* calc H */ /* XXX depends on 'kex' */
! 141: hash = kexgex_hash(
! 142: kex->client_version_string,
! 143: kex->server_version_string,
! 144: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
! 145: buffer_ptr(&kex->my), buffer_len(&kex->my),
! 146: server_host_key_blob, sbloblen,
! 147: min, nbits, max,
! 148: dh->p, dh->g,
! 149: dh_client_pub,
! 150: dh->pub_key,
! 151: shared_secret
! 152: );
! 153: BN_clear_free(dh_client_pub);
! 154:
! 155: /* save session id := H */
! 156: /* XXX hashlen depends on KEX */
! 157: if (kex->session_id == NULL) {
! 158: kex->session_id_len = 20;
! 159: kex->session_id = xmalloc(kex->session_id_len);
! 160: memcpy(kex->session_id, hash, kex->session_id_len);
! 161: }
! 162:
! 163: /* sign H */
! 164: /* XXX hashlen depends on KEX */
! 165: PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
! 166:
! 167: /* destroy_sensitive_data(); */
! 168:
! 169: /* send server hostkey, DH pubkey 'f' and singed H */
! 170: debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
! 171: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
! 172: packet_put_string(server_host_key_blob, sbloblen);
! 173: packet_put_bignum2(dh->pub_key); /* f */
! 174: packet_put_string(signature, slen);
! 175: packet_send();
! 176:
! 177: xfree(signature);
! 178: xfree(server_host_key_blob);
! 179: /* have keys, free DH */
! 180: DH_free(dh);
! 181:
! 182: kex_derive_keys(kex, hash, shared_secret);
! 183: BN_clear_free(shared_secret);
! 184:
! 185: kex_finish(kex);
! 186: }
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