openssh/auth2.c
Damien Miller 856f0be669 - markus@cvs.openbsd.org 2003/08/26 09:58:43
[auth-passwd.c auth.c auth.h auth1.c auth2-none.c auth2-passwd.c]
     [auth2.c monitor.c]
     fix passwd auth for 'username leaks via timing'; with djm@, original
     patches from solar
2003-09-03 07:32:45 +10:00

317 lines
8.3 KiB
C

/*
* 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.
*
* 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: auth2.c,v 1.102 2003/08/26 09:58:43 markus Exp $");
#include "ssh2.h"
#include "xmalloc.h"
#include "packet.h"
#include "log.h"
#include "servconf.h"
#include "compat.h"
#include "auth.h"
#include "dispatch.h"
#include "pathnames.h"
#include "monitor_wrap.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
/* import */
extern ServerOptions options;
extern u_char *session_id2;
extern u_int session_id2_len;
Authctxt *x_authctxt = NULL;
/* methods */
extern Authmethod method_none;
extern Authmethod method_pubkey;
extern Authmethod method_passwd;
extern Authmethod method_kbdint;
extern Authmethod method_hostbased;
#ifdef GSSAPI
extern Authmethod method_gssapi;
#endif
Authmethod *authmethods[] = {
&method_none,
&method_pubkey,
#ifdef GSSAPI
&method_gssapi,
#endif
&method_passwd,
&method_kbdint,
&method_hostbased,
NULL
};
/* protocol */
static void input_service_request(int, u_int32_t, void *);
static void input_userauth_request(int, u_int32_t, void *);
/* helper */
static Authmethod *authmethod_lookup(const char *);
static char *authmethods_get(void);
int user_key_allowed(struct passwd *, Key *);
int hostbased_key_allowed(struct passwd *, const char *, char *, Key *);
/*
* loop until authctxt->success == TRUE
*/
Authctxt *
do_authentication2(void)
{
Authctxt *authctxt = authctxt_new();
x_authctxt = authctxt; /*XXX*/
/* challenge-response is implemented via keyboard interactive */
if (options.challenge_response_authentication)
options.kbd_interactive_authentication = 1;
dispatch_init(&dispatch_protocol_error);
dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
return (authctxt);
}
static void
input_service_request(int type, u_int32_t seq, void *ctxt)
{
Authctxt *authctxt = ctxt;
u_int len;
int acceptit = 0;
char *service = packet_get_string(&len);
packet_check_eom();
if (authctxt == NULL)
fatal("input_service_request: no authctxt");
if (strcmp(service, "ssh-userauth") == 0) {
if (!authctxt->success) {
acceptit = 1;
/* now we can handle user-auth requests */
dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
}
}
/* XXX all other service requests are denied */
if (acceptit) {
packet_start(SSH2_MSG_SERVICE_ACCEPT);
packet_put_cstring(service);
packet_send();
packet_write_wait();
} else {
debug("bad service request %s", service);
packet_disconnect("bad service request %s", service);
}
xfree(service);
}
static void
input_userauth_request(int type, u_int32_t seq, void *ctxt)
{
Authctxt *authctxt = ctxt;
Authmethod *m = NULL;
char *user, *service, *method, *style = NULL;
int authenticated = 0;
if (authctxt == NULL)
fatal("input_userauth_request: no authctxt");
user = packet_get_string(NULL);
service = packet_get_string(NULL);
method = packet_get_string(NULL);
debug("userauth-request for user %s service %s method %s", user, service, method);
debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
if ((style = strchr(user, ':')) != NULL)
*style++ = 0;
if (authctxt->attempt++ == 0) {
/* setup auth context */
authctxt->pw = PRIVSEP(getpwnamallow(user));
if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
authctxt->valid = 1;
debug2("input_userauth_request: setting up authctxt for %s", user);
#ifdef USE_PAM
if (options.use_pam)
PRIVSEP(start_pam(authctxt->pw->pw_name));
#endif
} else {
logit("input_userauth_request: illegal user %s", user);
authctxt->pw = fakepw();
#ifdef USE_PAM
if (options.use_pam)
PRIVSEP(start_pam(user));
#endif
}
setproctitle("%s%s", authctxt->pw ? user : "unknown",
use_privsep ? " [net]" : "");
authctxt->user = xstrdup(user);
authctxt->service = xstrdup(service);
authctxt->style = style ? xstrdup(style) : NULL;
if (use_privsep)
mm_inform_authserv(service, style);
} else if (strcmp(user, authctxt->user) != 0 ||
strcmp(service, authctxt->service) != 0) {
packet_disconnect("Change of username or service not allowed: "
"(%s,%s) -> (%s,%s)",
authctxt->user, authctxt->service, user, service);
}
/* reset state */
auth2_challenge_stop(authctxt);
#ifdef GSSAPI
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
#endif
authctxt->postponed = 0;
/* try to authenticate user */
m = authmethod_lookup(method);
if (m != NULL) {
debug2("input_userauth_request: try method %s", method);
authenticated = m->userauth(authctxt);
}
userauth_finish(authctxt, authenticated, method);
xfree(service);
xfree(user);
xfree(method);
}
void
userauth_finish(Authctxt *authctxt, int authenticated, char *method)
{
char *methods;
if (!authctxt->valid && authenticated)
fatal("INTERNAL ERROR: authenticated invalid user %s",
authctxt->user);
/* Special handling for root */
if (authenticated && authctxt->pw->pw_uid == 0 &&
!auth_root_allowed(method))
authenticated = 0;
#ifdef USE_PAM
if (options.use_pam && authenticated && !PRIVSEP(do_pam_account()))
authenticated = 0;
#endif
#ifdef _UNICOS
if (authenticated && cray_access_denied(authctxt->user)) {
authenticated = 0;
fatal("Access denied for user %s.",authctxt->user);
}
#endif /* _UNICOS */
/* Log before sending the reply */
auth_log(authctxt, authenticated, method, " ssh2");
if (authctxt->postponed)
return;
/* XXX todo: check if multiple auth methods are needed */
if (authenticated == 1) {
/* turn off userauth */
dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
packet_start(SSH2_MSG_USERAUTH_SUCCESS);
packet_send();
packet_write_wait();
/* now we can break out */
authctxt->success = 1;
} else {
if (authctxt->failures++ > AUTH_FAIL_MAX)
packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
methods = authmethods_get();
packet_start(SSH2_MSG_USERAUTH_FAILURE);
packet_put_cstring(methods);
packet_put_char(0); /* XXX partial success, unused */
packet_send();
packet_write_wait();
xfree(methods);
}
}
/* get current user */
struct passwd*
auth_get_user(void)
{
return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL;
}
#define DELIM ","
static char *
authmethods_get(void)
{
Buffer b;
char *list;
int i;
buffer_init(&b);
for (i = 0; authmethods[i] != NULL; i++) {
if (strcmp(authmethods[i]->name, "none") == 0)
continue;
if (authmethods[i]->enabled != NULL &&
*(authmethods[i]->enabled) != 0) {
if (buffer_len(&b) > 0)
buffer_append(&b, ",", 1);
buffer_append(&b, authmethods[i]->name,
strlen(authmethods[i]->name));
}
}
buffer_append(&b, "\0", 1);
list = xstrdup(buffer_ptr(&b));
buffer_free(&b);
return list;
}
static Authmethod *
authmethod_lookup(const char *name)
{
int i;
if (name != NULL)
for (i = 0; authmethods[i] != NULL; i++)
if (authmethods[i]->enabled != NULL &&
*(authmethods[i]->enabled) != 0 &&
strcmp(name, authmethods[i]->name) == 0)
return authmethods[i];
debug2("Unrecognized authentication method name: %s",
name ? name : "NULL");
return NULL;
}