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/* $OpenBSD: auth1.c,v 1.76 2012/11/04 11:09:15 djm Exp $ */
/*
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
*
* 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"
#include <sys/types.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <pwd.h>
#include "openbsd-compat/sys-queue.h"
#include "xmalloc.h"
#include "rsa.h"
#include "ssh1.h"
#include "packet.h"
#include "buffer.h"
#include "log.h"
#include "servconf.h"
#include "compat.h"
#include "key.h"
#include "hostfile.h"
#include "auth.h"
#include "channels.h"
#include "session.h"
#include "uidswap.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "buffer.h"
/* import */
extern ServerOptions options;
extern Buffer loginmsg;
static int auth1_process_password(Authctxt *, char *, size_t);
static int auth1_process_rsa(Authctxt *, char *, size_t);
static int auth1_process_rhosts_rsa(Authctxt *, char *, size_t);
static int auth1_process_tis_challenge(Authctxt *, char *, size_t);
static int auth1_process_tis_response(Authctxt *, char *, size_t);
static char *client_user = NULL; /* Used to fill in remote user for PAM */
struct AuthMethod1 {
int type;
char *name;
int *enabled;
int (*method)(Authctxt *, char *, size_t);
};
const struct AuthMethod1 auth1_methods[] = {
{
SSH_CMSG_AUTH_PASSWORD, "password",
&options.password_authentication, auth1_process_password
},
{
SSH_CMSG_AUTH_RSA, "rsa",
&options.rsa_authentication, auth1_process_rsa
},
{
SSH_CMSG_AUTH_RHOSTS_RSA, "rhosts-rsa",
&options.rhosts_rsa_authentication, auth1_process_rhosts_rsa
},
{
SSH_CMSG_AUTH_TIS, "challenge-response",
&options.challenge_response_authentication,
auth1_process_tis_challenge
},
{
SSH_CMSG_AUTH_TIS_RESPONSE, "challenge-response",
&options.challenge_response_authentication,
auth1_process_tis_response
},
{ -1, NULL, NULL, NULL}
};
static const struct AuthMethod1
*lookup_authmethod1(int type)
{
int i;
for (i = 0; auth1_methods[i].name != NULL; i++)
if (auth1_methods[i].type == type)
return (&(auth1_methods[i]));
return (NULL);
}
static char *
get_authname(int type)
{
const struct AuthMethod1 *a;
static char buf[64];
if ((a = lookup_authmethod1(type)) != NULL)
return (a->name);
snprintf(buf, sizeof(buf), "bad-auth-msg-%d", type);
return (buf);
}
/*ARGSUSED*/
static int
auth1_process_password(Authctxt *authctxt, char *info, size_t infolen)
{
int authenticated = 0;
char *password;
u_int dlen;
/*
* Read user password. It is in plain text, but was
* transmitted over the encrypted channel so it is
* not visible to an outside observer.
*/
password = packet_get_string(&dlen);
packet_check_eom();
/* Try authentication with the password. */
authenticated = PRIVSEP(auth_password(authctxt, password));
memset(password, 0, dlen);
xfree(password);
return (authenticated);
}
/*ARGSUSED*/
static int
auth1_process_rsa(Authctxt *authctxt, char *info, size_t infolen)
{
int authenticated = 0;
BIGNUM *n;
/* RSA authentication requested. */
if ((n = BN_new()) == NULL)
fatal("do_authloop: BN_new failed");
packet_get_bignum(n);
packet_check_eom();
authenticated = auth_rsa(authctxt, n);
BN_clear_free(n);
return (authenticated);
}
/*ARGSUSED*/
static int
auth1_process_rhosts_rsa(Authctxt *authctxt, char *info, size_t infolen)
{
int keybits, authenticated = 0;
u_int bits;
Key *client_host_key;
u_int ulen;
/*
* Get client user name. Note that we just have to
* trust the client; root on the client machine can
* claim to be any user.
*/
client_user = packet_get_cstring(&ulen);
/* Get the client host key. */
client_host_key = key_new(KEY_RSA1);
bits = packet_get_int();
packet_get_bignum(client_host_key->rsa->e);
packet_get_bignum(client_host_key->rsa->n);
keybits = BN_num_bits(client_host_key->rsa->n);
if (keybits < 0 || bits != (u_int)keybits) {
verbose("Warning: keysize mismatch for client_host_key: "
"actual %d, announced %d",
BN_num_bits(client_host_key->rsa->n), bits);
}
packet_check_eom();
authenticated = auth_rhosts_rsa(authctxt, client_user,
client_host_key);
key_free(client_host_key);
snprintf(info, infolen, " ruser %.100s", client_user);
return (authenticated);
}
/*ARGSUSED*/
static int
auth1_process_tis_challenge(Authctxt *authctxt, char *info, size_t infolen)
{
char *challenge;
if ((challenge = get_challenge(authctxt)) == NULL)
return (0);
debug("sending challenge '%s'", challenge);
packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
packet_put_cstring(challenge);
xfree(challenge);
packet_send();
packet_write_wait();
return (-1);
}
/*ARGSUSED*/
static int
auth1_process_tis_response(Authctxt *authctxt, char *info, size_t infolen)
{
int authenticated = 0;
char *response;
u_int dlen;
response = packet_get_string(&dlen);
packet_check_eom();
authenticated = verify_response(authctxt, response);
memset(response, 'r', dlen);
xfree(response);
return (authenticated);
}
/*
* read packets, try to authenticate the user and
* return only if authentication is successful
*/
static void
do_authloop(Authctxt *authctxt)
{
int authenticated = 0;
char info[1024];
int prev = 0, type = 0;
const struct AuthMethod1 *meth;
debug("Attempting authentication for %s%.100s.",
authctxt->valid ? "" : "invalid user ", authctxt->user);
/* If the user has no password, accept authentication immediately. */
if (options.permit_empty_passwd && options.password_authentication &&
#ifdef KRB5
(!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
#endif
PRIVSEP(auth_password(authctxt, ""))) {
#ifdef USE_PAM
if (options.use_pam && (PRIVSEP(do_pam_account())))
#endif
{
auth_log(authctxt, 1, "without authentication", "");
return;
}
}
/* Indicate that authentication is needed. */
packet_start(SSH_SMSG_FAILURE);
packet_send();
packet_write_wait();
for (;;) {
/* default to fail */
authenticated = 0;
info[0] = '\0';
/* Get a packet from the client. */
prev = type;
type = packet_read();
/*
* If we started challenge-response authentication but the
* next packet is not a response to our challenge, release
* the resources allocated by get_challenge() (which would
* normally have been released by verify_response() had we
* received such a response)
*/
if (prev == SSH_CMSG_AUTH_TIS &&
type != SSH_CMSG_AUTH_TIS_RESPONSE)
abandon_challenge_response(authctxt);
if (authctxt->failures >= options.max_authtries)
goto skip;
if ((meth = lookup_authmethod1(type)) == NULL) {
logit("Unknown message dur
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