475 lines
13 KiB
C
475 lines
13 KiB
C
/*
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* Copyright (c) 2000 Markus Friedl. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Markus Friedl.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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RCSID("$OpenBSD: sshconnect2.c,v 1.10 2000/05/08 17:42:25 markus Exp $");
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#include <openssl/bn.h>
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#include <openssl/rsa.h>
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#include <openssl/dsa.h>
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#include <openssl/md5.h>
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#include <openssl/dh.h>
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#include <openssl/hmac.h>
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#include "ssh.h"
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#include "xmalloc.h"
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#include "rsa.h"
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#include "buffer.h"
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#include "packet.h"
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#include "cipher.h"
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#include "uidswap.h"
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#include "compat.h"
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#include "readconf.h"
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#include "bufaux.h"
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#include "ssh2.h"
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#include "kex.h"
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#include "myproposal.h"
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#include "key.h"
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#include "dsa.h"
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#include "sshconnect.h"
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#include "authfile.h"
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/* import */
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extern char *client_version_string;
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extern char *server_version_string;
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extern Options options;
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/*
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* SSH2 key exchange
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*/
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unsigned char *session_id2 = NULL;
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int session_id2_len = 0;
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void
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ssh_kex2(char *host, struct sockaddr *hostaddr)
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{
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Kex *kex;
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char *cprop[PROPOSAL_MAX];
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char *sprop[PROPOSAL_MAX];
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Buffer *client_kexinit;
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Buffer *server_kexinit;
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int payload_len, dlen;
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unsigned int klen, kout;
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char *ptr;
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char *signature = NULL;
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unsigned int slen;
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char *server_host_key_blob = NULL;
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Key *server_host_key;
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unsigned int sbloblen;
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DH *dh;
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BIGNUM *dh_server_pub = 0;
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BIGNUM *shared_secret = 0;
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int i;
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unsigned char *kbuf;
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unsigned char *hash;
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/* KEXINIT */
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debug("Sending KEX init.");
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if (options.ciphers != NULL) {
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myproposal[PROPOSAL_ENC_ALGS_CTOS] =
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myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
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} else if (options.cipher == SSH_CIPHER_3DES) {
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myproposal[PROPOSAL_ENC_ALGS_CTOS] =
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myproposal[PROPOSAL_ENC_ALGS_STOC] =
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cipher_name(SSH_CIPHER_3DES_CBC);
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} else if (options.cipher == SSH_CIPHER_BLOWFISH) {
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myproposal[PROPOSAL_ENC_ALGS_CTOS] =
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myproposal[PROPOSAL_ENC_ALGS_STOC] =
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cipher_name(SSH_CIPHER_BLOWFISH_CBC);
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}
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if (options.compression) {
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myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib";
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myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
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} else {
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myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none";
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myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
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}
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for (i = 0; i < PROPOSAL_MAX; i++)
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cprop[i] = xstrdup(myproposal[i]);
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client_kexinit = kex_init(cprop);
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packet_start(SSH2_MSG_KEXINIT);
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packet_put_raw(buffer_ptr(client_kexinit), buffer_len(client_kexinit));
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packet_send();
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packet_write_wait();
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debug("done");
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packet_read_expect(&payload_len, SSH2_MSG_KEXINIT);
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/* save payload for session_id */
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server_kexinit = xmalloc(sizeof(*server_kexinit));
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buffer_init(server_kexinit);
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ptr = packet_get_raw(&payload_len);
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buffer_append(server_kexinit, ptr, payload_len);
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/* skip cookie */
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for (i = 0; i < 16; i++)
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(void) packet_get_char();
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/* kex init proposal strings */
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for (i = 0; i < PROPOSAL_MAX; i++) {
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sprop[i] = packet_get_string(NULL);
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debug("got kexinit string: %s", sprop[i]);
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}
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i = (int) packet_get_char();
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debug("first kex follow == %d", i);
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i = packet_get_int();
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debug("reserved == %d", i);
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packet_done();
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debug("done read kexinit");
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kex = kex_choose_conf(cprop, sprop, 0);
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/* KEXDH */
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debug("Sending SSH2_MSG_KEXDH_INIT.");
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/* generate and send 'e', client DH public key */
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dh = dh_new_group1();
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packet_start(SSH2_MSG_KEXDH_INIT);
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packet_put_bignum2(dh->pub_key);
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packet_send();
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packet_write_wait();
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#ifdef DEBUG_KEXDH
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fprintf(stderr, "\np= ");
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bignum_print(dh->p);
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fprintf(stderr, "\ng= ");
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bignum_print(dh->g);
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fprintf(stderr, "\npub= ");
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bignum_print(dh->pub_key);
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fprintf(stderr, "\n");
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DHparams_print_fp(stderr, dh);
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#endif
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debug("Wait SSH2_MSG_KEXDH_REPLY.");
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packet_read_expect(&payload_len, SSH2_MSG_KEXDH_REPLY);
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debug("Got SSH2_MSG_KEXDH_REPLY.");
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/* key, cert */
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server_host_key_blob = packet_get_string(&sbloblen);
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server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen);
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if (server_host_key == NULL)
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fatal("cannot decode server_host_key_blob");
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check_host_key(host, hostaddr, server_host_key,
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options.user_hostfile2, options.system_hostfile2);
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/* DH paramter f, server public DH key */
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dh_server_pub = BN_new();
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if (dh_server_pub == NULL)
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fatal("dh_server_pub == NULL");
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packet_get_bignum2(dh_server_pub, &dlen);
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#ifdef DEBUG_KEXDH
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fprintf(stderr, "\ndh_server_pub= ");
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bignum_print(dh_server_pub);
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fprintf(stderr, "\n");
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debug("bits %d", BN_num_bits(dh_server_pub));
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#endif
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/* signed H */
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signature = packet_get_string(&slen);
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packet_done();
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if (!dh_pub_is_valid(dh, dh_server_pub))
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packet_disconnect("bad server public DH value");
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klen = DH_size(dh);
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kbuf = xmalloc(klen);
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kout = DH_compute_key(kbuf, dh_server_pub, dh);
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#ifdef DEBUG_KEXDH
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debug("shared secret: len %d/%d", klen, kout);
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fprintf(stderr, "shared secret == ");
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for (i = 0; i< kout; i++)
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fprintf(stderr, "%02x", (kbuf[i])&0xff);
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fprintf(stderr, "\n");
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#endif
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shared_secret = BN_new();
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BN_bin2bn(kbuf, kout, shared_secret);
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memset(kbuf, 0, klen);
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xfree(kbuf);
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/* calc and verify H */
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hash = kex_hash(
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client_version_string,
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server_version_string,
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buffer_ptr(client_kexinit), buffer_len(client_kexinit),
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buffer_ptr(server_kexinit), buffer_len(server_kexinit),
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server_host_key_blob, sbloblen,
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dh->pub_key,
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dh_server_pub,
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shared_secret
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);
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xfree(server_host_key_blob);
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buffer_free(client_kexinit);
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buffer_free(server_kexinit);
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xfree(client_kexinit);
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xfree(server_kexinit);
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#ifdef DEBUG_KEXDH
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fprintf(stderr, "hash == ");
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for (i = 0; i< 20; i++)
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fprintf(stderr, "%02x", (hash[i])&0xff);
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fprintf(stderr, "\n");
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#endif
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if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1)
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fatal("dsa_verify failed for server_host_key");
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key_free(server_host_key);
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kex_derive_keys(kex, hash, shared_secret);
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packet_set_kex(kex);
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/* have keys, free DH */
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DH_free(dh);
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/* save session id */
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session_id2_len = 20;
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session_id2 = xmalloc(session_id2_len);
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memcpy(session_id2, hash, session_id2_len);
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debug("Wait SSH2_MSG_NEWKEYS.");
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packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
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packet_done();
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debug("GOT SSH2_MSG_NEWKEYS.");
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debug("send SSH2_MSG_NEWKEYS.");
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packet_start(SSH2_MSG_NEWKEYS);
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packet_send();
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packet_write_wait();
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debug("done: send SSH2_MSG_NEWKEYS.");
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#ifdef DEBUG_KEXDH
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/* send 1st encrypted/maced/compressed message */
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packet_start(SSH2_MSG_IGNORE);
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packet_put_cstring("markus");
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packet_send();
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packet_write_wait();
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#endif
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debug("done: KEX2.");
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}
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/*
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* Authenticate user
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*/
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int
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ssh2_try_passwd(const char *server_user, const char *host, const char *service)
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{
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static int attempt = 0;
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char prompt[80];
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char *password;
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if (attempt++ > options.number_of_password_prompts)
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return 0;
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snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
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server_user, host);
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password = read_passphrase(prompt, 0);
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packet_start(SSH2_MSG_USERAUTH_REQUEST);
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packet_put_cstring(server_user);
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packet_put_cstring(service);
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packet_put_cstring("password");
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packet_put_char(0);
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packet_put_cstring(password);
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memset(password, 0, strlen(password));
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xfree(password);
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packet_send();
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packet_write_wait();
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return 1;
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}
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int
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ssh2_try_pubkey(char *filename,
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const char *server_user, const char *host, const char *service)
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{
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Buffer b;
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Key *k;
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unsigned char *blob, *signature;
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int bloblen, slen;
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struct stat st;
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if (stat(filename, &st) != 0) {
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debug("key does not exist: %s", filename);
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return 0;
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}
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debug("try pubkey: %s", filename);
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k = key_new(KEY_DSA);
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if (!load_private_key(filename, "", k, NULL)) {
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int success = 0;
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char *passphrase;
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char prompt[300];
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snprintf(prompt, sizeof prompt,
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"Enter passphrase for DSA key '%.100s': ",
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filename);
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passphrase = read_passphrase(prompt, 0);
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success = load_private_key(filename, passphrase, k, NULL);
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memset(passphrase, 0, strlen(passphrase));
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xfree(passphrase);
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if (!success)
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return 0;
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}
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dsa_make_key_blob(k, &blob, &bloblen);
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/* data to be signed */
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buffer_init(&b);
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buffer_append(&b, session_id2, session_id2_len);
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buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
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buffer_put_cstring(&b, server_user);
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buffer_put_cstring(&b,
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datafellows & SSH_BUG_PUBKEYAUTH ?
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"ssh-userauth" :
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service);
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buffer_put_cstring(&b, "publickey");
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buffer_put_char(&b, 1);
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buffer_put_cstring(&b, KEX_DSS);
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buffer_put_string(&b, blob, bloblen);
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/* generate signature */
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dsa_sign(k, &signature, &slen, buffer_ptr(&b), buffer_len(&b));
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key_free(k);
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#ifdef DEBUG_DSS
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buffer_dump(&b);
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#endif
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if (datafellows & SSH_BUG_PUBKEYAUTH) {
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/* e.g. ssh-2.0.13: data-to-be-signed != data-on-the-wire */
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buffer_clear(&b);
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buffer_append(&b, session_id2, session_id2_len);
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buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
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buffer_put_cstring(&b, server_user);
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buffer_put_cstring(&b, service);
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buffer_put_cstring(&b, "publickey");
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buffer_put_char(&b, 1);
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buffer_put_cstring(&b, KEX_DSS);
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buffer_put_string(&b, blob, bloblen);
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}
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xfree(blob);
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/* append signature */
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buffer_put_string(&b, signature, slen);
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xfree(signature);
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/* skip session id and packet type */
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if (buffer_len(&b) < session_id2_len + 1)
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fatal("ssh2_try_pubkey: internal error");
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buffer_consume(&b, session_id2_len + 1);
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/* put remaining data from buffer into packet */
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packet_start(SSH2_MSG_USERAUTH_REQUEST);
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packet_put_raw(buffer_ptr(&b), buffer_len(&b));
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buffer_free(&b);
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/* send */
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packet_send();
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packet_write_wait();
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return 1;
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}
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void
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ssh_userauth2(const char *server_user, char *host)
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{
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int type;
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int plen;
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int sent;
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unsigned int dlen;
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int partial;
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int i = 0;
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char *auths;
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char *service = "ssh-connection"; /* service name */
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debug("send SSH2_MSG_SERVICE_REQUEST");
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packet_start(SSH2_MSG_SERVICE_REQUEST);
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packet_put_cstring("ssh-userauth");
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packet_send();
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packet_write_wait();
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type = packet_read(&plen);
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if (type != SSH2_MSG_SERVICE_ACCEPT) {
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fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
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}
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if (packet_remaining() > 0) {
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char *reply = packet_get_string(&plen);
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debug("service_accept: %s", reply);
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xfree(reply);
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} else {
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/* payload empty for ssh-2.0.13 ?? */
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debug("buggy server: service_accept w/o service");
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}
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packet_done();
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debug("got SSH2_MSG_SERVICE_ACCEPT");
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/* INITIAL request for auth */
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packet_start(SSH2_MSG_USERAUTH_REQUEST);
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packet_put_cstring(server_user);
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packet_put_cstring(service);
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packet_put_cstring("none");
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packet_send();
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packet_write_wait();
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for (;;) {
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sent = 0;
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type = packet_read(&plen);
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if (type == SSH2_MSG_USERAUTH_SUCCESS)
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break;
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if (type != SSH2_MSG_USERAUTH_FAILURE)
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fatal("access denied: %d", type);
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/* SSH2_MSG_USERAUTH_FAILURE means: try again */
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auths = packet_get_string(&dlen);
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debug("authentications that can continue: %s", auths);
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partial = packet_get_char();
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packet_done();
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if (partial)
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debug("partial success");
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if (options.dsa_authentication &&
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strstr(auths, "publickey") != NULL) {
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while (i < options.num_identity_files2) {
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sent = ssh2_try_pubkey(
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options.identity_files2[i++],
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server_user, host, service);
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if (sent)
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break;
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}
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}
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if (!sent) {
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if (options.password_authentication &&
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!options.batch_mode &&
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strstr(auths, "password") != NULL) {
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sent = ssh2_try_passwd(server_user, host, service);
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}
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}
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if (!sent)
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fatal("Permission denied (%s).", auths);
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xfree(auths);
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}
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packet_done();
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debug("ssh-userauth2 successfull");
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}
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