NetBSD/crypto/dist/ssh/sshconnect1.c
dyoung 4758291178 Fix the checkflist for builds without Kerberos 4 (MKKERBEROS4=no)
and without Kerberos 4 & 5 (MKKERBEROS=no). Previously checkflist
complained of missing files.

* move kerberos- and kerberos 4-only files into new flists,
  distrib/sets/lists/*/krb.*

* make the flist generators grok MKKERBEROS{,4} variables

* fix Makefiles which treat MKKERBEROS=no as MKKERBEROS5=no.
  9 out of 10 experts agree that it is ludicrous to build w/
  KERBEROS4 and w/o KERBEROS5.

* fix header files, also, which treat MKKERBEROS=no as MKKERBEROS5=no.

* omit some Kerberos-only subdirectories from the build as
  MKKERBEROS{,4} indicate

(I acknowledge the sentiment that flists are the wrong way to go,
and that the makefiles should produce the metalog directly.  That
sounds to me like the right way to go, but I am not prepared to do
revamp all the makefiles.  While my approach is expedient, it fits
painlessly within the current build architecture until we are
delivered from flist purgatory, and it does not postpone our
delivery. Fair enough?)
2003-12-11 09:46:26 +00:00

1267 lines
34 KiB
C

/* $NetBSD: sshconnect1.c,v 1.27 2003/12/11 09:46:26 dyoung Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* Code to connect to a remote host, and to perform the client side of the
* login (authentication) dialog.
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*/
#include "includes.h"
RCSID("$OpenBSD: sshconnect1.c,v 1.52 2002/08/08 13:50:23 aaron Exp $");
__RCSID("$NetBSD: sshconnect1.c,v 1.27 2003/12/11 09:46:26 dyoung Exp $");
#include <openssl/bn.h>
#include <openssl/md5.h>
#ifdef KRB4
#include <krb.h>
#ifdef AFS
#include <kafs.h>
#include "radix.h"
#endif
#endif
#ifdef KRB5
#include <krb5.h>
#endif
#include "ssh.h"
#include "ssh1.h"
#include "xmalloc.h"
#include "rsa.h"
#include "buffer.h"
#include "packet.h"
#include "mpaux.h"
#include "uidswap.h"
#include "log.h"
#include "readconf.h"
#include "key.h"
#include "authfd.h"
#include "sshconnect.h"
#include "authfile.h"
#include "readpass.h"
#include "cipher.h"
#include "canohost.h"
#include "auth.h"
/* Session id for the current session. */
u_char session_id[16];
u_int supported_authentications = 0;
extern Options options;
extern char *__progname;
/*
* Checks if the user has an authentication agent, and if so, tries to
* authenticate using the agent.
*/
static int
try_agent_authentication(void)
{
int type;
char *comment;
AuthenticationConnection *auth;
u_char response[16];
u_int i;
Key *key;
BIGNUM *challenge;
/* Get connection to the agent. */
auth = ssh_get_authentication_connection();
if (!auth)
return 0;
if ((challenge = BN_new()) == NULL)
fatal("try_agent_authentication: BN_new failed");
/* Loop through identities served by the agent. */
for (key = ssh_get_first_identity(auth, &comment, 1);
key != NULL;
key = ssh_get_next_identity(auth, &comment, 1)) {
/* Try this identity. */
debug("Trying RSA authentication via agent with '%.100s'", comment);
xfree(comment);
/* Tell the server that we are willing to authenticate using this key. */
packet_start(SSH_CMSG_AUTH_RSA);
packet_put_bignum(key->rsa->n);
packet_send();
packet_write_wait();
/* Wait for server's response. */
type = packet_read();
/* The server sends failure if it doesn\'t like our key or
does not support RSA authentication. */
if (type == SSH_SMSG_FAILURE) {
debug("Server refused our key.");
key_free(key);
continue;
}
/* Otherwise it should have sent a challenge. */
if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
packet_disconnect("Protocol error during RSA authentication: %d",
type);
packet_get_bignum(challenge);
packet_check_eom();
debug("Received RSA challenge from server.");
/* Ask the agent to decrypt the challenge. */
if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) {
/*
* The agent failed to authenticate this identifier
* although it advertised it supports this. Just
* return a wrong value.
*/
logit("Authentication agent failed to decrypt challenge.");
memset(response, 0, sizeof(response));
}
key_free(key);
debug("Sending response to RSA challenge.");
/* Send the decrypted challenge back to the server. */
packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
for (i = 0; i < 16; i++)
packet_put_char(response[i]);
packet_send();
packet_write_wait();
/* Wait for response from the server. */
type = packet_read();
/* The server returns success if it accepted the authentication. */
if (type == SSH_SMSG_SUCCESS) {
ssh_close_authentication_connection(auth);
BN_clear_free(challenge);
debug("RSA authentication accepted by server.");
return 1;
}
/* Otherwise it should return failure. */
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error waiting RSA auth response: %d",
type);
}
ssh_close_authentication_connection(auth);
BN_clear_free(challenge);
debug("RSA authentication using agent refused.");
return 0;
}
/*
* Computes the proper response to a RSA challenge, and sends the response to
* the server.
*/
static void
respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
{
u_char buf[32], response[16];
MD5_CTX md;
int i, len;
/* Decrypt the challenge using the private key. */
/* XXX think about Bleichenbacher, too */
if (rsa_private_decrypt(challenge, challenge, prv) <= 0)
packet_disconnect(
"respond_to_rsa_challenge: rsa_private_decrypt failed");
/* Compute the response. */
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
if (len <= 0 || len > sizeof(buf))
packet_disconnect(
"respond_to_rsa_challenge: bad challenge length %d", len);
memset(buf, 0, sizeof(buf));
BN_bn2bin(challenge, buf + sizeof(buf) - len);
MD5_Init(&md);
MD5_Update(&md, buf, 32);
MD5_Update(&md, session_id, 16);
MD5_Final(response, &md);
debug("Sending response to host key RSA challenge.");
/* Send the response back to the server. */
packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
for (i = 0; i < 16; i++)
packet_put_char(response[i]);
packet_send();
packet_write_wait();
memset(buf, 0, sizeof(buf));
memset(response, 0, sizeof(response));
memset(&md, 0, sizeof(md));
}
/*
* Checks if the user has authentication file, and if so, tries to authenticate
* the user using it.
*/
static int
try_rsa_authentication(int idx)
{
BIGNUM *challenge;
Key *public, *private;
char buf[300], *passphrase, *comment, *authfile;
int i, type, quit;
public = options.identity_keys[idx];
authfile = options.identity_files[idx];
comment = xstrdup(authfile);
debug("Trying RSA authentication with key '%.100s'", comment);
/* Tell the server that we are willing to authenticate using this key. */
packet_start(SSH_CMSG_AUTH_RSA);
packet_put_bignum(public->rsa->n);
packet_send();
packet_write_wait();
/* Wait for server's response. */
type = packet_read();
/*
* The server responds with failure if it doesn\'t like our key or
* doesn\'t support RSA authentication.
*/
if (type == SSH_SMSG_FAILURE) {
debug("Server refused our key.");
xfree(comment);
return 0;
}
/* Otherwise, the server should respond with a challenge. */
if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
packet_disconnect("Protocol error during RSA authentication: %d", type);
/* Get the challenge from the packet. */
if ((challenge = BN_new()) == NULL)
fatal("try_rsa_authentication: BN_new failed");
packet_get_bignum(challenge);
packet_check_eom();
debug("Received RSA challenge from server.");
/*
* If the key is not stored in external hardware, we have to
* load the private key. Try first with empty passphrase; if it
* fails, ask for a passphrase.
*/
if (public->flags & KEY_FLAG_EXT)
private = public;
else
private = key_load_private_type(KEY_RSA1, authfile, "", NULL);
if (private == NULL && !options.batch_mode) {
snprintf(buf, sizeof(buf),
"Enter passphrase for RSA key '%.100s': ", comment);
for (i = 0; i < options.number_of_password_prompts; i++) {
passphrase = read_passphrase(buf, 0);
if (strcmp(passphrase, "") != 0) {
private = key_load_private_type(KEY_RSA1,
authfile, passphrase, NULL);
quit = 0;
} else {
debug2("no passphrase given, try next key");
quit = 1;
}
memset(passphrase, 0, strlen(passphrase));
xfree(passphrase);
if (private != NULL || quit)
break;
debug2("bad passphrase given, try again...");
}
}
/* We no longer need the comment. */
xfree(comment);
if (private == NULL) {
if (!options.batch_mode)
error("Bad passphrase.");
/* Send a dummy response packet to avoid protocol error. */
packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
for (i = 0; i < 16; i++)
packet_put_char(0);
packet_send();
packet_write_wait();
/* Expect the server to reject it... */
packet_read_expect(SSH_SMSG_FAILURE);
BN_clear_free(challenge);
return 0;
}
/* Compute and send a response to the challenge. */
respond_to_rsa_challenge(challenge, private->rsa);
/* Destroy the private key unless it in external hardware. */
if (!(private->flags & KEY_FLAG_EXT))
key_free(private);
/* We no longer need the challenge. */
BN_clear_free(challenge);
/* Wait for response from the server. */
type = packet_read();
if (type == SSH_SMSG_SUCCESS) {
debug("RSA authentication accepted by server.");
return 1;
}
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error waiting RSA auth response: %d", type);
debug("RSA authentication refused.");
return 0;
}
/*
* Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
* authentication and RSA host authentication.
*/
static int
try_rhosts_rsa_authentication(const char *local_user, Key * host_key)
{
int type;
BIGNUM *challenge;
debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
/* Tell the server that we are willing to authenticate using this key. */
packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
packet_put_cstring(local_user);
packet_put_int(BN_num_bits(host_key->rsa->n));
packet_put_bignum(host_key->rsa->e);
packet_put_bignum(host_key->rsa->n);
packet_send();
packet_write_wait();
/* Wait for server's response. */
type = packet_read();
/* The server responds with failure if it doesn't admit our
.rhosts authentication or doesn't know our host key. */
if (type == SSH_SMSG_FAILURE) {
debug("Server refused our rhosts authentication or host key.");
return 0;
}
/* Otherwise, the server should respond with a challenge. */
if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
packet_disconnect("Protocol error during RSA authentication: %d", type);
/* Get the challenge from the packet. */
if ((challenge = BN_new()) == NULL)
fatal("try_rhosts_rsa_authentication: BN_new failed");
packet_get_bignum(challenge);
packet_check_eom();
debug("Received RSA challenge for host key from server.");
/* Compute a response to the challenge. */
respond_to_rsa_challenge(challenge, host_key->rsa);
/* We no longer need the challenge. */
BN_clear_free(challenge);
/* Wait for response from the server. */
type = packet_read();
if (type == SSH_SMSG_SUCCESS) {
debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
return 1;
}
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error waiting RSA auth response: %d", type);
debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
return 0;
}
#ifdef KRB4
static int
try_krb4_authentication(void)
{
KTEXT_ST auth; /* Kerberos data */
char *reply;
char inst[INST_SZ];
char *realm;
CREDENTIALS cred;
int r, type;
socklen_t slen;
Key_schedule schedule;
u_long checksum, cksum;
MSG_DAT msg_data;
struct sockaddr_in local, foreign;
struct stat st;
/* Don't do anything if we don't have any tickets. */
if (stat(tkt_string(), &st) < 0)
return 0;
strlcpy(inst, (char *)krb_get_phost(get_canonical_hostname(1)),
INST_SZ);
realm = (char *)krb_realmofhost(get_canonical_hostname(1));
if (!realm) {
debug("Kerberos v4: no realm for %s", get_canonical_hostname(1));
return 0;
}
/* This can really be anything. */
checksum = (u_long)getpid();
r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
if (r != KSUCCESS) {
debug("Kerberos v4 krb_mk_req failed: %s", krb_err_txt[r]);
return 0;
}
/* Get session key to decrypt the server's reply with. */
r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
if (r != KSUCCESS) {
debug("get_cred failed: %s", krb_err_txt[r]);
return 0;
}
des_key_sched((des_cblock *) cred.session, schedule);
/* Send authentication info to server. */
packet_start(SSH_CMSG_AUTH_KERBEROS);
packet_put_string((char *) auth.dat, auth.length);
packet_send();
packet_write_wait();
/* Zero the buffer. */
(void) memset(auth.dat, 0, MAX_KTXT_LEN);
slen = sizeof(local);
memset(&local, 0, sizeof(local));
if (getsockname(packet_get_connection_in(),
(struct sockaddr *)&local, &slen) < 0)
debug("getsockname failed: %s", strerror(errno));
slen = sizeof(foreign);
memset(&foreign, 0, sizeof(foreign));
if (getpeername(packet_get_connection_in(),
(struct sockaddr *)&foreign, &slen) < 0) {
debug("getpeername failed: %s", strerror(errno));
fatal_cleanup();
}
/* Get server reply. */
type = packet_read();
switch (type) {
case SSH_SMSG_FAILURE:
/* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
debug("Kerberos v4 authentication failed.");
return 0;
break;
case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
/* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
debug("Kerberos v4 authentication accepted.");
/* Get server's response. */
reply = packet_get_string((u_int *) &auth.length);
if (auth.length >= MAX_KTXT_LEN)
fatal("Kerberos v4: Malformed response from server");
memcpy(auth.dat, reply, auth.length);
xfree(reply);
packet_check_eom();
/*
* If his response isn't properly encrypted with the session
* key, and the decrypted checksum fails to match, he's
* bogus. Bail out.
*/
r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
&foreign, &local, &msg_data);
if (r != KSUCCESS) {
debug("Kerberos v4 krb_rd_priv failed: %s",
krb_err_txt[r]);
packet_disconnect("Kerberos v4 challenge failed!");
}
/* Fetch the (incremented) checksum that we supplied in the request. */
memcpy((char *)&cksum, (char *)msg_data.app_data,
sizeof(cksum));
cksum = ntohl(cksum);
/* If it matches, we're golden. */
if (cksum == checksum + 1) {
debug("Kerberos v4 challenge successful.");
return 1;
} else
packet_disconnect("Kerberos v4 challenge failed!");
break;
default:
packet_disconnect("Protocol error on Kerberos v4 response: %d", type);
}
return 0;
}
#endif /* KRB4 */
#ifdef KRB5
static int
try_krb5_authentication(krb5_context *context, krb5_auth_context *auth_context)
{
krb5_error_code problem;
const char *tkfile;
struct stat buf;
krb5_ccache ccache = NULL;
const char *remotehost;
krb5_data ap;
int type;
krb5_ap_rep_enc_part *reply = NULL;
int ret;
memset(&ap, 0, sizeof(ap));
problem = krb5_init_context(context);
if (problem) {
debug("Kerberos v5: krb5_init_context failed");
ret = 0;
goto out;
}
tkfile = krb5_cc_default_name(*context);
if (strncmp(tkfile, "FILE:", 5) == 0)
tkfile += 5;
if (stat(tkfile, &buf) == 0 && getuid() != buf.st_uid) {
debug("Kerberos v5: could not get default ccache (permission denied).");
ret = 0;
goto out;
}
problem = krb5_cc_default(*context, &ccache);
if (problem) {
debug("Kerberos v5: krb5_cc_default failed: %s",
krb5_get_err_text(*context, problem));
ret = 0;
goto out;
}
remotehost = get_canonical_hostname(1);
problem = krb5_mk_req(*context, auth_context, AP_OPTS_MUTUAL_REQUIRED,
"host", remotehost, NULL, ccache, &ap);
if (problem) {
debug("Kerberos v5: krb5_mk_req failed: %s",
krb5_get_err_text(*context, problem));
ret = 0;
goto out;
}
packet_start(SSH_CMSG_AUTH_KERBEROS);
packet_put_string((char *) ap.data, ap.length);
packet_send();
packet_write_wait();
xfree(ap.data);
ap.length = 0;
type = packet_read();
switch (type) {
case SSH_SMSG_FAILURE:
/* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
debug("Kerberos v5 authentication failed.");
ret = 0;
break;
case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
/* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
debug("Kerberos v5 authentication accepted.");
/* Get server's response. */
ap.data = packet_get_string((unsigned int *) &ap.length);
packet_check_eom();
/* XXX je to dobre? */
problem = krb5_rd_rep(*context, *auth_context, &ap, &reply);
if (problem) {
ret = 0;
}
ret = 1;
break;
default:
packet_disconnect("Protocol error on Kerberos v5 response: %d",
type);
ret = 0;
break;
}
out:
if (ccache != NULL)
krb5_cc_close(*context, ccache);
if (reply != NULL)
krb5_free_ap_rep_enc_part(*context, reply);
if (ap.length > 0)
krb5_data_free(&ap);
return (ret);
}
static void
send_krb5_tgt(krb5_context context, krb5_auth_context auth_context)
{
int fd, type;
krb5_error_code problem;
krb5_data outbuf;
krb5_ccache ccache = NULL;
krb5_creds creds;
krb5_kdc_flags flags;
const char *remotehost;
memset(&creds, 0, sizeof(creds));
memset(&outbuf, 0, sizeof(outbuf));
fd = packet_get_connection_in();
problem = krb5_auth_con_setaddrs_from_fd(context, auth_context, &fd);
if (problem)
goto out;
problem = krb5_cc_default(context, &ccache);
if (problem)
goto out;
problem = krb5_cc_get_principal(context, ccache, &creds.client);
if (problem)
goto out;
problem = krb5_build_principal(context, &creds.server,
strlen(creds.client->realm), creds.client->realm,
"krbtgt", creds.client->realm, NULL);
if (problem)
goto out;
creds.times.endtime = 0;
flags.i = 0;
flags.b.forwarded = 1;
flags.b.forwardable = krb5_config_get_bool(context, NULL,
"libdefaults", "forwardable", NULL);
remotehost = get_canonical_hostname(1);
problem = krb5_get_forwarded_creds(context, auth_context,
ccache, flags.i, remotehost, &creds, &outbuf);
if (problem)
goto out;
packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
packet_put_string((char *)outbuf.data, outbuf.length);
packet_send();
packet_write_wait();
type = packet_read();
if (type == SSH_SMSG_SUCCESS) {
char *pname;
krb5_unparse_name(context, creds.client, &pname);
debug("Kerberos v5 TGT forwarded (%s).", pname);
xfree(pname);
} else
debug("Kerberos v5 TGT forwarding failed.");
return;
out:
if (problem)
debug("Kerberos v5 TGT forwarding failed: %s",
krb5_get_err_text(context, problem));
if (creds.client)
krb5_free_principal(context, creds.client);
if (creds.server)
krb5_free_principal(context, creds.server);
if (ccache)
krb5_cc_close(context, ccache);
if (outbuf.data)
xfree(outbuf.data);
}
#endif /* KRB5 */
#ifdef KRB4
#ifdef AFS
static void
send_krb4_tgt(void)
{
CREDENTIALS *creds;
struct stat st;
char buffer[4096], pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
int problem, type;
/* Don't do anything if we don't have any tickets. */
if (stat(tkt_string(), &st) < 0)
return;
creds = xmalloc(sizeof(*creds));
problem = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm);
if (problem)
goto out;
problem = krb_get_cred("krbtgt", prealm, prealm, creds);
if (problem)
goto out;
if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
problem = RD_AP_EXP;
goto out;
}
creds_to_radix(creds, (u_char *)buffer, sizeof(buffer));
packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
packet_put_cstring(buffer);
packet_send();
packet_write_wait();
type = packet_read();
if (type == SSH_SMSG_SUCCESS)
debug("Kerberos v4 TGT forwarded (%s%s%s@%s).",
creds->pname, creds->pinst[0] ? "." : "",
creds->pinst, creds->realm);
else
debug("Kerberos v4 TGT rejected.");
xfree(creds);
return;
out:
debug("Kerberos v4 TGT passing failed: %s", krb_err_txt[problem]);
xfree(creds);
}
static void
send_afs_tokens(void)
{
CREDENTIALS creds;
struct ViceIoctl parms;
struct ClearToken ct;
int i, type, len;
char buf[2048], *p, *server_cell;
char buffer[8192];
/* Move over ktc_GetToken, here's something leaner. */
for (i = 0; i < 100; i++) { /* just in case */
parms.in = (char *) &i;
parms.in_size = sizeof(i);
parms.out = buf;
parms.out_size = sizeof(buf);
if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0)
break;
p = buf;
/* Get secret token. */
memcpy(&creds.ticket_st.length, p, sizeof(u_int));
if (creds.ticket_st.length > MAX_KTXT_LEN)
break;
p += sizeof(u_int);
memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
p += creds.ticket_st.length;
/* Get clear token. */
memcpy(&len, p, sizeof(len));
if (len != sizeof(struct ClearToken))
break;
p += sizeof(len);
memcpy(&ct, p, len);
p += len;
p += sizeof(len); /* primary flag */
server_cell = p;
/* Flesh out our credentials. */
strlcpy(creds.service, "afs", sizeof(creds.service));
creds.instance[0] = '\0';
strlcpy(creds.realm, server_cell, REALM_SZ);
memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
creds.issue_date = ct.BeginTimestamp;
creds.lifetime = krb_time_to_life(creds.issue_date,
ct.EndTimestamp);
creds.kvno = ct.AuthHandle;
snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
creds.pinst[0] = '\0';
/* Encode token, ship it off. */
if (creds_to_radix(&creds, (u_char *)buffer,
sizeof(buffer)) <= 0)
break;
packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
packet_put_cstring(buffer);
packet_send();
packet_write_wait();
/* Roger, Roger. Clearance, Clarence. What's your vector,
Victor? */
type = packet_read();
if (type == SSH_SMSG_FAILURE)
debug("AFS token for cell %s rejected.", server_cell);
else if (type != SSH_SMSG_SUCCESS)
packet_disconnect("Protocol error on AFS token response: %d", type);
}
}
#endif /* AFS */
#endif /* KRB4 */
/*
* Tries to authenticate with any string-based challenge/response system.
* Note that the client code is not tied to s/key or TIS.
*/
static int
try_challenge_response_authentication(void)
{
int type, i;
u_int clen;
char prompt[1024];
char *challenge, *response;
debug("Doing challenge response authentication.");
for (i = 0; i < options.number_of_password_prompts; i++) {
/* request a challenge */
packet_start(SSH_CMSG_AUTH_TIS);
packet_send();
packet_write_wait();
type = packet_read();
if (type != SSH_SMSG_FAILURE &&
type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
packet_disconnect("Protocol error: got %d in response "
"to SSH_CMSG_AUTH_TIS", type);
}
if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
debug("No challenge.");
return 0;
}
challenge = packet_get_string(&clen);
packet_check_eom();
snprintf(prompt, sizeof prompt, "%s%s", challenge,
strchr(challenge, '\n') ? "" : "\nResponse: ");
xfree(challenge);
if (i != 0)
error("Permission denied, please try again.");
if (options.cipher == SSH_CIPHER_NONE)
logit("WARNING: Encryption is disabled! "
"Response will be transmitted in clear text.");
response = read_passphrase(prompt, 0);
if (strcmp(response, "") == 0) {
xfree(response);
break;
}
packet_start(SSH_CMSG_AUTH_TIS_RESPONSE);
ssh_put_password(response);
memset(response, 0, strlen(response));
xfree(response);
packet_send();
packet_write_wait();
type = packet_read();
if (type == SSH_SMSG_SUCCESS)
return 1;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response "
"to SSH_CMSG_AUTH_TIS_RESPONSE", type);
}
/* failure */
return 0;
}
/*
* Tries to authenticate with plain passwd authentication.
*/
static int
try_password_authentication(char *prompt)
{
int type, i;
char *password;
debug("Doing password authentication.");
if (options.cipher == SSH_CIPHER_NONE)
logit("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
for (i = 0; i < options.number_of_password_prompts; i++) {
if (i != 0)
error("Permission denied, please try again.");
password = read_passphrase(prompt, 0);
packet_start(SSH_CMSG_AUTH_PASSWORD);
ssh_put_password(password);
memset(password, 0, strlen(password));
xfree(password);
packet_send();
packet_write_wait();
type = packet_read();
if (type == SSH_SMSG_SUCCESS)
return 1;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to passwd auth", type);
}
/* failure */
return 0;
}
/*
* SSH1 key exchange
*/
void
ssh_kex(char *host, struct sockaddr *hostaddr)
{
int i;
BIGNUM *key;
Key *host_key, *server_key;
int bits, rbits;
int ssh_cipher_default = SSH_CIPHER_3DES;
u_char session_key[SSH_SESSION_KEY_LENGTH];
u_char cookie[8];
u_int supported_ciphers;
u_int server_flags, client_flags;
u_int32_t rand = 0;
debug("Waiting for server public key.");
/* Wait for a public key packet from the server. */
packet_read_expect(SSH_SMSG_PUBLIC_KEY);
/* Get cookie from the packet. */
for (i = 0; i < 8; i++)
cookie[i] = packet_get_char();
/* Get the public key. */
server_key = key_new(KEY_RSA1);
bits = packet_get_int();
packet_get_bignum(server_key->rsa->e);
packet_get_bignum(server_key->rsa->n);
rbits = BN_num_bits(server_key->rsa->n);
if (bits != rbits) {
logit("Warning: Server lies about size of server public key: "
"actual size is %d bits vs. announced %d.", rbits, bits);
logit("Warning: This may be due to an old implementation of ssh.");
}
/* Get the host key. */
host_key = key_new(KEY_RSA1);
bits = packet_get_int();
packet_get_bignum(host_key->rsa->e);
packet_get_bignum(host_key->rsa->n);
rbits = BN_num_bits(host_key->rsa->n);
if (bits != rbits) {
logit("Warning: Server lies about size of server host key: "
"actual size is %d bits vs. announced %d.", rbits, bits);
logit("Warning: This may be due to an old implementation of ssh.");
}
/* Get protocol flags. */
server_flags = packet_get_int();
packet_set_protocol_flags(server_flags);
supported_ciphers = packet_get_int();
supported_authentications = packet_get_int();
packet_check_eom();
debug("Received server public key (%d bits) and host key (%d bits).",
BN_num_bits(server_key->rsa->n), BN_num_bits(host_key->rsa->n));
if (verify_host_key(host, hostaddr, host_key) == -1)
fatal("Host key verification failed.");
client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN;
compute_session_id(session_id, cookie, host_key->rsa->n, server_key->rsa->n);
/* Generate a session key. */
arc4random_stir();
/*
* Generate an encryption key for the session. The key is a 256 bit
* random number, interpreted as a 32-byte key, with the least
* significant 8 bits being the first byte of the key.
*/
for (i = 0; i < 32; i++) {
if (i % 4 == 0)
rand = arc4random();
session_key[i] = rand & 0xff;
rand >>= 8;
}
/*
* According to the protocol spec, the first byte of the session key
* is the highest byte of the integer. The session key is xored with
* the first 16 bytes of the session id.
*/
if ((key = BN_new()) == NULL)
fatal("respond_to_rsa_challenge: BN_new failed");
BN_set_word(key, 0);
for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
BN_lshift(key, key, 8);
if (i < 16)
BN_add_word(key, session_key[i] ^ session_id[i]);
else
BN_add_word(key, session_key[i]);
}
/*
* Encrypt the integer using the public key and host key of the
* server (key with smaller modulus first).
*/
if (BN_cmp(server_key->rsa->n, host_key->rsa->n) < 0) {
/* Public key has smaller modulus. */
if (BN_num_bits(host_key->rsa->n) <
BN_num_bits(server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
fatal("respond_to_rsa_challenge: host_key %d < server_key %d + "
"SSH_KEY_BITS_RESERVED %d",
BN_num_bits(host_key->rsa->n),
BN_num_bits(server_key->rsa->n),
SSH_KEY_BITS_RESERVED);
}
rsa_public_encrypt(key, key, server_key->rsa);
rsa_public_encrypt(key, key, host_key->rsa);
} else {
/* Host key has smaller modulus (or they are equal). */
if (BN_num_bits(server_key->rsa->n) <
BN_num_bits(host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
fatal("respond_to_rsa_challenge: server_key %d < host_key %d + "
"SSH_KEY_BITS_RESERVED %d",
BN_num_bits(server_key->rsa->n),
BN_num_bits(host_key->rsa->n),
SSH_KEY_BITS_RESERVED);
}
rsa_public_encrypt(key, key, host_key->rsa);
rsa_public_encrypt(key, key, server_key->rsa);
}
/* Destroy the public keys since we no longer need them. */
key_free(server_key);
key_free(host_key);
if (options.cipher == SSH_CIPHER_NOT_SET) {
if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default))
options.cipher = ssh_cipher_default;
} else if (options.cipher == SSH_CIPHER_ILLEGAL ||
!(cipher_mask_ssh1(1) & (1 << options.cipher))) {
logit("No valid SSH1 cipher, using %.100s instead.",
cipher_name(ssh_cipher_default));
options.cipher = ssh_cipher_default;
}
/* Check that the selected cipher is supported. */
if (!(supported_ciphers & (1 << options.cipher)))
fatal("Selected cipher type %.100s not supported by server.",
cipher_name(options.cipher));
debug("Encryption type: %.100s", cipher_name(options.cipher));
/* Send the encrypted session key to the server. */
packet_start(SSH_CMSG_SESSION_KEY);
packet_put_char(options.cipher);
/* Send the cookie back to the server. */
for (i = 0; i < 8; i++)
packet_put_char(cookie[i]);
/* Send and destroy the encrypted encryption key integer. */
packet_put_bignum(key);
BN_clear_free(key);
/* Send protocol flags. */
packet_put_int(client_flags);
/* Send the packet now. */
packet_send();
packet_write_wait();
debug("Sent encrypted session key.");
/* Set the encryption key. */
packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher);
/* We will no longer need the session key here. Destroy any extra copies. */
memset(session_key, 0, sizeof(session_key));
/*
* Expect a success message from the server. Note that this message
* will be received in encrypted form.
*/
packet_read_expect(SSH_SMSG_SUCCESS);
debug("Received encrypted confirmation.");
}
/*
* Authenticate user
*/
void
ssh_userauth1(const char *local_user, const char *server_user, char *host,
Sensitive *sensitive)
{
#ifdef KRB5
krb5_context context = NULL;
krb5_auth_context auth_context = NULL;
#endif
int i, type;
if (supported_authentications == 0)
fatal("ssh_userauth1: server supports no auth methods");
/* Send the name of the user to log in as on the server. */
packet_start(SSH_CMSG_USER);
packet_put_cstring(server_user);
packet_send();
packet_write_wait();
/*
* The server should respond with success if no authentication is
* needed (the user has no password). Otherwise the server responds
* with failure.
*/
type = packet_read();
/* check whether the connection was accepted without authentication. */
if (type == SSH_SMSG_SUCCESS)
goto success;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", type);
#ifdef KRB5
if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
options.kerberos_authentication) {
debug("Trying Kerberos v5 authentication.");
if (try_krb5_authentication(&context, &auth_context)) {
type = packet_read();
if (type == SSH_SMSG_SUCCESS)
goto success;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to Kerberos v5 auth", type);
}
}
#endif /* KRB5 */
#ifdef KRB4
if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
options.kerberos_authentication) {
debug("Trying Kerberos v4 authentication.");
if (try_krb4_authentication()) {
type = packet_read();
if (type == SSH_SMSG_SUCCESS)
goto success;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to Kerberos v4 auth", type);
}
}
#endif /* KRB4 */
/*
* Use rhosts authentication if running in privileged socket and we
* do not wish to remain anonymous.
*/
if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
options.rhosts_authentication) {
debug("Trying rhosts authentication.");
packet_start(SSH_CMSG_AUTH_RHOSTS);
packet_put_cstring(local_user);
packet_send();
packet_write_wait();
/* The server should respond with success or failure. */
type = packet_read();
if (type == SSH_SMSG_SUCCESS)
goto success;
if (type != SSH_SMSG_FAILURE)
packet_disconnect("Protocol error: got %d in response to rhosts auth",
type);
}
/*
* Try .rhosts or /etc/hosts.equiv authentication with RSA host
* authentication.
*/
if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
options.rhosts_rsa_authentication) {
for (i = 0; i < sensitive->nkeys; i++) {
if (sensitive->keys[i] != NULL &&
sensitive->keys[i]->type == KEY_RSA1 &&
try_rhosts_rsa_authentication(local_user,
sensitive->keys[i]))
goto success;
}
}
/* Try RSA authentication if the server supports it. */
if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
options.rsa_authentication) {
/*
* Try RSA authentication using the authentication agent. The
* agent is tried first because no passphrase is needed for
* it, whereas identity files may require passphrases.
*/
if (try_agent_authentication())
goto success;
/* Try RSA authentication for each identity. */
for (i = 0; i < options.num_identity_files; i++)
if (options.identity_keys[i] != NULL &&
options.identity_keys[i]->type == KEY_RSA1 &&
try_rsa_authentication(i))
goto success;
}
/* Try challenge response authentication if the server supports it. */
if ((supported_authentications & (1 << SSH_AUTH_TIS)) &&
options.challenge_response_authentication && !options.batch_mode) {
if (try_challenge_response_authentication())
goto success;
}
/* Try password authentication if the server supports it. */
if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
options.password_authentication && !options.batch_mode) {
char prompt[80];
snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ",
server_user, host);
if (try_password_authentication(prompt))
goto success;
}
/* All authentication methods have failed. Exit with an error message. */
fatal("Permission denied.");
/* NOTREACHED */
success:
#ifdef KRB5
/* Try Kerberos v5 TGT passing. */
if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
options.kerberos_tgt_passing && context && auth_context) {
if (options.cipher == SSH_CIPHER_NONE)
logit("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
send_krb5_tgt(context, auth_context);
}
if (auth_context)
krb5_auth_con_free(context, auth_context);
if (context)
krb5_free_context(context);
#endif
#ifdef KRB4
#ifdef AFS
/* Try Kerberos v4 TGT passing if the server supports it. */
if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
options.kerberos_tgt_passing) {
if (options.cipher == SSH_CIPHER_NONE)
logit("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
send_krb4_tgt();
}
/* Try AFS token passing if the server supports it. */
if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
options.afs_token_passing && k_hasafs()) {
if (options.cipher == SSH_CIPHER_NONE)
logit("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
send_afs_tokens();
}
#endif /* AFS */
#endif /* KRB4 */
return; /* need statement after label */
}