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openssh/sshconnect2.c

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/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Markus Friedl.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
RCSID("$OpenBSD: sshconnect2.c,v 1.11 2000/05/25 20:45:20 markus Exp $");
#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/dsa.h>
#include <openssl/md5.h>
#include <openssl/dh.h>
#include <openssl/hmac.h>
#include "ssh.h"
#include "xmalloc.h"
#include "rsa.h"
#include "buffer.h"
#include "packet.h"
#include "cipher.h"
#include "uidswap.h"
#include "compat.h"
#include "readconf.h"
#include "bufaux.h"
#include "ssh2.h"
#include "kex.h"
#include "myproposal.h"
#include "key.h"
#include "dsa.h"
#include "sshconnect.h"
#include "authfile.h"
/* import */
extern char *client_version_string;
extern char *server_version_string;
extern Options options;
/*
* SSH2 key exchange
*/
unsigned char *session_id2 = NULL;
int session_id2_len = 0;
void
ssh_kex_dh(Kex *kex, char *host, struct sockaddr *hostaddr,
Buffer *client_kexinit, Buffer *server_kexinit)
{
int i;
int plen, dlen;
unsigned int klen, kout;
char *signature = NULL;
unsigned int slen;
char *server_host_key_blob = NULL;
Key *server_host_key;
unsigned int sbloblen;
DH *dh;
BIGNUM *dh_server_pub = 0;
BIGNUM *shared_secret = 0;
unsigned char *kbuf;
unsigned char *hash;
debug("Sending SSH2_MSG_KEXDH_INIT.");
/* generate and send 'e', client DH public key */
dh = dh_new_group1();
packet_start(SSH2_MSG_KEXDH_INIT);
packet_put_bignum2(dh->pub_key);
packet_send();
packet_write_wait();
#ifdef DEBUG_KEXDH
fprintf(stderr, "\np= ");
bignum_print(dh->p);
fprintf(stderr, "\ng= ");
bignum_print(dh->g);
fprintf(stderr, "\npub= ");
bignum_print(dh->pub_key);
fprintf(stderr, "\n");
DHparams_print_fp(stderr, dh);
#endif
debug("Wait SSH2_MSG_KEXDH_REPLY.");
packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);
debug("Got SSH2_MSG_KEXDH_REPLY.");
/* key, cert */
server_host_key_blob = packet_get_string(&sbloblen);
server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen);
if (server_host_key == NULL)
fatal("cannot decode server_host_key_blob");
check_host_key(host, hostaddr, server_host_key,
options.user_hostfile2, options.system_hostfile2);
/* DH paramter f, server public DH key */
dh_server_pub = BN_new();
if (dh_server_pub == NULL)
fatal("dh_server_pub == NULL");
packet_get_bignum2(dh_server_pub, &dlen);
#ifdef DEBUG_KEXDH
fprintf(stderr, "\ndh_server_pub= ");
bignum_print(dh_server_pub);
fprintf(stderr, "\n");
debug("bits %d", BN_num_bits(dh_server_pub));
#endif
/* signed H */
signature = packet_get_string(&slen);
packet_done();
if (!dh_pub_is_valid(dh, dh_server_pub))
packet_disconnect("bad server public DH value");
klen = DH_size(dh);
kbuf = xmalloc(klen);
kout = DH_compute_key(kbuf, dh_server_pub, dh);
#ifdef DEBUG_KEXDH
debug("shared secret: len %d/%d", klen, kout);
fprintf(stderr, "shared secret == ");
for (i = 0; i< kout; i++)
fprintf(stderr, "%02x", (kbuf[i])&0xff);
fprintf(stderr, "\n");
#endif
shared_secret = BN_new();
BN_bin2bn(kbuf, kout, shared_secret);
memset(kbuf, 0, klen);
xfree(kbuf);
/* calc and verify H */
hash = kex_hash(
client_version_string,
server_version_string,
buffer_ptr(client_kexinit), buffer_len(client_kexinit),
buffer_ptr(server_kexinit), buffer_len(server_kexinit),
server_host_key_blob, sbloblen,
dh->pub_key,
dh_server_pub,
shared_secret
);
xfree(server_host_key_blob);
DH_free(dh);
#ifdef DEBUG_KEXDH
fprintf(stderr, "hash == ");
for (i = 0; i< 20; i++)
fprintf(stderr, "%02x", (hash[i])&0xff);
fprintf(stderr, "\n");
#endif
if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1)
fatal("dsa_verify failed for server_host_key");
key_free(server_host_key);
kex_derive_keys(kex, hash, shared_secret);
packet_set_kex(kex);
/* save session id */
session_id2_len = 20;
session_id2 = xmalloc(session_id2_len);
memcpy(session_id2, hash, session_id2_len);
}
void
ssh_kex2(char *host, struct sockaddr *hostaddr)
{
int i, plen;
Kex *kex;
Buffer *client_kexinit, *server_kexinit;
char *sprop[PROPOSAL_MAX];
if (options.ciphers != NULL) {
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
} else if (options.cipher == SSH_CIPHER_3DES) {
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
myproposal[PROPOSAL_ENC_ALGS_STOC] =
(char *) cipher_name(SSH_CIPHER_3DES_CBC);
} else if (options.cipher == SSH_CIPHER_BLOWFISH) {
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
myproposal[PROPOSAL_ENC_ALGS_STOC] =
(char *) cipher_name(SSH_CIPHER_BLOWFISH_CBC);
}
if (options.compression) {
myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib";
myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
} else {
myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none";
myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
}
/* buffers with raw kexinit messages */
server_kexinit = xmalloc(sizeof(*server_kexinit));
buffer_init(server_kexinit);
client_kexinit = kex_init(myproposal);
/* algorithm negotiation */
kex_exchange_kexinit(client_kexinit, server_kexinit, sprop);
kex = kex_choose_conf(myproposal, sprop, 0);
for (i = 0; i < PROPOSAL_MAX; i++)
xfree(sprop[i]);
/* server authentication and session key agreement */
ssh_kex_dh(kex, host, hostaddr, client_kexinit, server_kexinit);
buffer_free(client_kexinit);
buffer_free(server_kexinit);
xfree(client_kexinit);
xfree(server_kexinit);
debug("Wait SSH2_MSG_NEWKEYS.");
packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
packet_done();
debug("GOT SSH2_MSG_NEWKEYS.");
debug("send SSH2_MSG_NEWKEYS.");
packet_start(SSH2_MSG_NEWKEYS);
packet_send();
packet_write_wait();
debug("done: send SSH2_MSG_NEWKEYS.");
#ifdef DEBUG_KEXDH
/* send 1st encrypted/maced/compressed message */
packet_start(SSH2_MSG_IGNORE);
packet_put_cstring("markus");
packet_send();
packet_write_wait();
#endif
debug("done: KEX2.");
}
/*
* Authenticate user
*/
int
ssh2_try_passwd(const char *server_user, const char *host, const char *service)
{
static int attempt = 0;
char prompt[80];
char *password;
if (attempt++ > options.number_of_password_prompts)
return 0;
snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
server_user, host);
password = read_passphrase(prompt, 0);
packet_start(SSH2_MSG_USERAUTH_REQUEST);
packet_put_cstring(server_user);
packet_put_cstring(service);
packet_put_cstring("password");
packet_put_char(0);
packet_put_cstring(password);
memset(password, 0, strlen(password));
xfree(password);
packet_send();
packet_write_wait();
return 1;
}
int
ssh2_try_pubkey(char *filename,
const char *server_user, const char *host, const char *service)
{
Buffer b;
Key *k;
unsigned char *blob, *signature;
int bloblen, slen;
struct stat st;
if (stat(filename, &st) != 0) {
debug("key does not exist: %s", filename);
return 0;
}
debug("try pubkey: %s", filename);
k = key_new(KEY_DSA);
if (!load_private_key(filename, "", k, NULL)) {
int success = 0;
char *passphrase;
char prompt[300];
snprintf(prompt, sizeof prompt,
"Enter passphrase for DSA key '%.100s': ",
filename);
passphrase = read_passphrase(prompt, 0);
success = load_private_key(filename, passphrase, k, NULL);
memset(passphrase, 0, strlen(passphrase));
xfree(passphrase);
if (!success)
return 0;
}
dsa_make_key_blob(k, &blob, &bloblen);
/* data to be signed */
buffer_init(&b);
buffer_append(&b, session_id2, session_id2_len);
buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
buffer_put_cstring(&b, server_user);
buffer_put_cstring(&b,
datafellows & SSH_BUG_PUBKEYAUTH ?
"ssh-userauth" :
service);
buffer_put_cstring(&b, "publickey");
buffer_put_char(&b, 1);
buffer_put_cstring(&b, KEX_DSS);
buffer_put_string(&b, blob, bloblen);
/* generate signature */
dsa_sign(k, &signature, &slen, buffer_ptr(&b), buffer_len(&b));
key_free(k);
#ifdef DEBUG_DSS
buffer_dump(&b);
#endif
if (datafellows & SSH_BUG_PUBKEYAUTH) {
/* e.g. ssh-2.0.13: data-to-be-signed != data-on-the-wire */
buffer_clear(&b);
buffer_append(&b, session_id2, session_id2_len);
buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
buffer_put_cstring(&b, server_user);
buffer_put_cstring(&b, service);
buffer_put_cstring(&b, "publickey");
buffer_put_char(&b, 1);
buffer_put_cstring(&b, KEX_DSS);
buffer_put_string(&b, blob, bloblen);
}
xfree(blob);
/* append signature */
buffer_put_string(&b, signature, slen);
xfree(signature);
/* skip session id and packet type */
if (buffer_len(&b) < session_id2_len + 1)
fatal("ssh2_try_pubkey: internal error");
buffer_consume(&b, session_id2_len + 1);
/* put remaining data from buffer into packet */
packet_start(SSH2_MSG_USERAUTH_REQUEST);
packet_put_raw(buffer_ptr(&b), buffer_len(&b));
buffer_free(&b);
/* send */
packet_send();
packet_write_wait();
return 1;
}
void
ssh_userauth2(const char *server_user, char *host)
{
int type;
int plen;
int sent;
unsigned int dlen;
int partial;
int i = 0;
char *auths;
char *service = "ssh-connection"; /* service name */
debug("send SSH2_MSG_SERVICE_REQUEST");
packet_start(SSH2_MSG_SERVICE_REQUEST);
packet_put_cstring("ssh-userauth");
packet_send();
packet_write_wait();
type = packet_read(&plen);
if (type != SSH2_MSG_SERVICE_ACCEPT) {
fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
}
if (packet_remaining() > 0) {
char *reply = packet_get_string(&plen);
debug("service_accept: %s", reply);
xfree(reply);
} else {
/* payload empty for ssh-2.0.13 ?? */
debug("buggy server: service_accept w/o service");
}
packet_done();
debug("got SSH2_MSG_SERVICE_ACCEPT");
/* INITIAL request for auth */
packet_start(SSH2_MSG_USERAUTH_REQUEST);
packet_put_cstring(server_user);
packet_put_cstring(service);
packet_put_cstring("none");
packet_send();
packet_write_wait();
for (;;) {
sent = 0;
type = packet_read(&plen);
if (type == SSH2_MSG_USERAUTH_SUCCESS)
break;
if (type != SSH2_MSG_USERAUTH_FAILURE)
fatal("access denied: %d", type);
/* SSH2_MSG_USERAUTH_FAILURE means: try again */
auths = packet_get_string(&dlen);
debug("authentications that can continue: %s", auths);
partial = packet_get_char();
packet_done();
if (partial)
debug("partial success");
if (options.dsa_authentication &&
strstr(auths, "publickey") != NULL) {
while (i < options.num_identity_files2) {
sent = ssh2_try_pubkey(
options.identity_files2[i++],
server_user, host, service);
if (sent)
break;
}
}
if (!sent) {
if (options.password_authentication &&
!options.batch_mode &&
strstr(auths, "password") != NULL) {
sent = ssh2_try_passwd(server_user, host, service);
}
}
if (!sent)
fatal("Permission denied (%s).", auths);
xfree(auths);
}
packet_done();
debug("ssh-userauth2 successfull");
}
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