Annotation of src/usr.bin/ssh/kexecdhs.c, Revision 1.1
1.1 ! djm 1: /* $OpenBSD$ */
! 2: /*
! 3: * Copyright (c) 2001 Markus Friedl. All rights reserved.
! 4: * Copyright (c) 2010 Damien Miller. All rights reserved.
! 5: *
! 6: * Redistribution and use in source and binary forms, with or without
! 7: * modification, are permitted provided that the following conditions
! 8: * are met:
! 9: * 1. Redistributions of source code must retain the above copyright
! 10: * notice, this list of conditions and the following disclaimer.
! 11: * 2. Redistributions in binary form must reproduce the above copyright
! 12: * notice, this list of conditions and the following disclaimer in the
! 13: * documentation and/or other materials provided with the distribution.
! 14: *
! 15: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
! 16: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
! 17: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
! 18: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
! 19: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
! 20: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
! 21: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
! 22: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
! 23: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
! 24: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
! 25: */
! 26:
! 27: #include <sys/types.h>
! 28: #include <string.h>
! 29: #include <signal.h>
! 30:
! 31: #include <openssl/ecdh.h>
! 32:
! 33: #include "xmalloc.h"
! 34: #include "buffer.h"
! 35: #include "key.h"
! 36: #include "cipher.h"
! 37: #include "kex.h"
! 38: #include "log.h"
! 39: #include "packet.h"
! 40: #include "dh.h"
! 41: #include "ssh2.h"
! 42: #ifdef GSSAPI
! 43: #include "ssh-gss.h"
! 44: #endif
! 45: #include "monitor_wrap.h"
! 46:
! 47: void
! 48: kexecdh_server(Kex *kex)
! 49: {
! 50: EC_POINT *client_public;
! 51: EC_KEY *server_key;
! 52: const EC_GROUP *group;
! 53: BIGNUM *shared_secret;
! 54: Key *server_host_private, *server_host_public;
! 55: u_char *server_host_key_blob = NULL, *signature = NULL;
! 56: u_char *kbuf, *hash;
! 57: u_int klen, slen, sbloblen, hashlen;
! 58: int curve_nid;
! 59:
! 60: curve_nid = kex_ecdh_name_to_nid(kex->name);
! 61: if ((server_key = EC_KEY_new_by_curve_name(curve_nid)) == NULL)
! 62: fatal("%s: EC_KEY_new_by_curve_name failed", __func__);
! 63: if (EC_KEY_generate_key(server_key) != 1)
! 64: fatal("%s: EC_KEY_generate_key failed", __func__);
! 65: group = EC_KEY_get0_group(server_key);
! 66:
! 67: #ifdef DEBUG_KEXECDH
! 68: fputs("server private key:\n", stderr);
! 69: key_dump_ec_key(server_key);
! 70: #endif
! 71:
! 72: if (kex->load_host_public_key == NULL ||
! 73: kex->load_host_private_key == NULL)
! 74: fatal("Cannot load hostkey");
! 75: server_host_public = kex->load_host_public_key(kex->hostkey_type);
! 76: if (server_host_public == NULL)
! 77: fatal("Unsupported hostkey type %d", kex->hostkey_type);
! 78: server_host_private = kex->load_host_private_key(kex->hostkey_type);
! 79: if (server_host_private == NULL)
! 80: fatal("Missing private key for hostkey type %d",
! 81: kex->hostkey_type);
! 82:
! 83: debug("expecting SSH2_MSG_KEX_ECDH_INIT");
! 84: packet_read_expect(SSH2_MSG_KEX_ECDH_INIT);
! 85: if ((client_public = EC_POINT_new(group)) == NULL)
! 86: fatal("%s: EC_POINT_new failed", __func__);
! 87: packet_get_ecpoint(group, client_public);
! 88: packet_check_eom();
! 89:
! 90: if (key_ec_validate_public(group, client_public) != 0)
! 91: fatal("%s: invalid client public key", __func__);
! 92:
! 93: #ifdef DEBUG_KEXECDH
! 94: fputs("client public key:\n", stderr);
! 95: key_dump_ec_point(group, client_public);
! 96: #endif
! 97:
! 98: /* Calculate shared_secret */
! 99: klen = (EC_GROUP_get_degree(group) + 7) / 8;
! 100: kbuf = xmalloc(klen);
! 101: if (ECDH_compute_key(kbuf, klen, client_public,
! 102: server_key, NULL) != (int)klen)
! 103: fatal("%s: ECDH_compute_key failed", __func__);
! 104:
! 105: #ifdef DEBUG_KEXDH
! 106: dump_digest("shared secret", kbuf, klen);
! 107: #endif
! 108: if ((shared_secret = BN_new()) == NULL)
! 109: fatal("%s: BN_new failed", __func__);
! 110: if (BN_bin2bn(kbuf, klen, shared_secret) == NULL)
! 111: fatal("%s: BN_bin2bn failed", __func__);
! 112: memset(kbuf, 0, klen);
! 113: xfree(kbuf);
! 114:
! 115: /* calc H */
! 116: key_to_blob(server_host_public, &server_host_key_blob, &sbloblen);
! 117: kex_ecdh_hash(
! 118: kex->evp_md,
! 119: group,
! 120: kex->client_version_string,
! 121: kex->server_version_string,
! 122: buffer_ptr(&kex->peer), buffer_len(&kex->peer),
! 123: buffer_ptr(&kex->my), buffer_len(&kex->my),
! 124: server_host_key_blob, sbloblen,
! 125: client_public,
! 126: EC_KEY_get0_public_key(server_key),
! 127: shared_secret,
! 128: &hash, &hashlen
! 129: );
! 130: EC_POINT_clear_free(client_public);
! 131:
! 132: /* save session id := H */
! 133: if (kex->session_id == NULL) {
! 134: kex->session_id_len = hashlen;
! 135: kex->session_id = xmalloc(kex->session_id_len);
! 136: memcpy(kex->session_id, hash, kex->session_id_len);
! 137: }
! 138:
! 139: /* sign H */
! 140: if (PRIVSEP(key_sign(server_host_private, &signature, &slen,
! 141: hash, hashlen)) < 0)
! 142: fatal("kexdh_server: key_sign failed");
! 143:
! 144: /* destroy_sensitive_data(); */
! 145:
! 146: /* send server hostkey, ECDH pubkey 'Q_S' and signed H */
! 147: packet_start(SSH2_MSG_KEX_ECDH_REPLY);
! 148: packet_put_string(server_host_key_blob, sbloblen);
! 149: packet_put_ecpoint(group, EC_KEY_get0_public_key(server_key));
! 150: packet_put_string(signature, slen);
! 151: packet_send();
! 152:
! 153: xfree(signature);
! 154: xfree(server_host_key_blob);
! 155: /* have keys, free server key */
! 156: EC_KEY_free(server_key);
! 157:
! 158: kex_derive_keys(kex, hash, hashlen, shared_secret);
! 159: BN_clear_free(shared_secret);
! 160: kex_finish(kex);
! 161: }
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