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auth-pam.c
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auth-pam.c
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/*-
* Copyright (c) 2002 Networks Associates Technology, Inc.
* All rights reserved.
*
* This software was developed for the FreeBSD Project by ThinkSec AS and
* NAI Labs, the Security Research Division of Network Associates, Inc.
* under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
* DARPA CHATS research program.
*
* 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
*/
/*
* Copyright (c) 2003,2004 Damien Miller <djm@mindrot.org>
* Copyright (c) 2003,2004 Darren Tucker <dtucker@zip.com.au>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* Based on FreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:18 des */
#include "includes.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <errno.h>
#include <signal.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#ifdef USE_PAM
#if defined(HAVE_SECURITY_PAM_APPL_H)
#include <security/pam_appl.h>
#elif defined (HAVE_PAM_PAM_APPL_H)
#include <pam/pam_appl.h>
#endif
#if !defined(SSHD_PAM_SERVICE)
extern char *__progname;
# define SSHD_PAM_SERVICE __progname
#endif
/* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
#ifdef PAM_SUN_CODEBASE
# define sshpam_const /* Solaris, HP-UX, SunOS */
#else
# define sshpam_const const /* LinuxPAM, OpenPAM, AIX */
#endif
/* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
#ifdef PAM_SUN_CODEBASE
# define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member)
#else
# define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member)
#endif
#include "xmalloc.h"
#include "sshbuf.h"
#include "ssherr.h"
#include "hostfile.h"
#include "auth.h"
#include "auth-pam.h"
#include "canohost.h"
#include "log.h"
#include "msg.h"
#include "packet.h"
#include "misc.h"
#include "servconf.h"
#include "ssh2.h"
#include "auth-options.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
extern ServerOptions options;
extern struct sshbuf *loginmsg;
extern u_int utmp_len;
/* so we don't silently change behaviour */
#ifdef USE_POSIX_THREADS
# error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
#endif
/*
* Formerly known as USE_POSIX_THREADS, using this is completely unsupported
* and generally a bad idea. Use at own risk and do not expect support if
* this breaks.
*/
#ifdef UNSUPPORTED_POSIX_THREADS_HACK
#include <pthread.h>
/*
* Avoid namespace clash when *not* using pthreads for systems *with*
* pthreads, which unconditionally define pthread_t via sys/types.h
* (e.g. Linux)
*/
typedef pthread_t sp_pthread_t;
#else
typedef pid_t sp_pthread_t;
#define pthread_exit fake_pthread_exit
#define pthread_create fake_pthread_create
#define pthread_cancel fake_pthread_cancel
#define pthread_join fake_pthread_join
#endif
struct pam_ctxt {
sp_pthread_t pam_thread;
int pam_psock;
int pam_csock;
int pam_done;
};
static void sshpam_free_ctx(void *);
static struct pam_ctxt *cleanup_ctxt;
#ifndef UNSUPPORTED_POSIX_THREADS_HACK
/*
* Simulate threads with processes.
*/
static int sshpam_thread_status = -1;
static mysig_t sshpam_oldsig;
static void
sshpam_sigchld_handler(int sig)
{
signal(SIGCHLD, SIG_DFL);
if (cleanup_ctxt == NULL)
return; /* handler called after PAM cleanup, shouldn't happen */
if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
<= 0) {
/* PAM thread has not exitted, privsep slave must have */
kill(cleanup_ctxt->pam_thread, SIGTERM);
while (waitpid(cleanup_ctxt->pam_thread,
&sshpam_thread_status, 0) == -1) {
if (errno == EINTR)
continue;
return;
}
}
if (WIFSIGNALED(sshpam_thread_status) &&
WTERMSIG(sshpam_thread_status) == SIGTERM)
return; /* terminated by pthread_cancel */
if (!WIFEXITED(sshpam_thread_status))
sigdie("PAM: authentication thread exited unexpectedly");
if (WEXITSTATUS(sshpam_thread_status) != 0)
sigdie("PAM: authentication thread exited uncleanly");
}
/* ARGSUSED */
static void
pthread_exit(void *value)
{
_exit(0);
}
/* ARGSUSED */
static int
pthread_create(sp_pthread_t *thread, const void *attr,
void *(*thread_start)(void *), void *arg)
{
pid_t pid;
struct pam_ctxt *ctx = arg;
sshpam_thread_status = -1;
switch ((pid = fork())) {
case -1:
error("fork(): %s", strerror(errno));
return (-1);
case 0:
close(ctx->pam_psock);
ctx->pam_psock = -1;
thread_start(arg);
_exit(1);
default:
*thread = pid;
close(ctx->pam_csock);
ctx->pam_csock = -1;
sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);
return (0);
}
}
static int
pthread_cancel(sp_pthread_t thread)
{
signal(SIGCHLD, sshpam_oldsig);
return (kill(thread, SIGTERM));
}
/* ARGSUSED */
static int
pthread_join(sp_pthread_t thread, void **value)
{
int status;
if (sshpam_thread_status != -1)
return (sshpam_thread_status);
signal(SIGCHLD, sshpam_oldsig);
while (waitpid(thread, &status, 0) == -1) {
if (errno == EINTR)
continue;
fatal("%s: waitpid: %s", __func__, strerror(errno));
}
return (status);
}
#endif
static pam_handle_t *sshpam_handle = NULL;
static int sshpam_err = 0;
static int sshpam_authenticated = 0;
static int sshpam_session_open = 0;
static int sshpam_cred_established = 0;
static int sshpam_account_status = -1;
static int sshpam_maxtries_reached = 0;
static char **sshpam_env = NULL;
static Authctxt *sshpam_authctxt = NULL;
static const char *sshpam_password = NULL;
static char *sshpam_rhost = NULL;
static char *sshpam_laddr = NULL;
static char *sshpam_conninfo = NULL;
/* Some PAM implementations don't implement this */
#ifndef HAVE_PAM_GETENVLIST
static char **
pam_getenvlist(pam_handle_t *pamh)
{
/*
* XXX - If necessary, we can still support envrionment passing
* for platforms without pam_getenvlist by searching for known
* env vars (e.g. KRB5CCNAME) from the PAM environment.
*/
return NULL;
}
#endif
/*
* Some platforms, notably Solaris, do not enforce password complexity
* rules during pam_chauthtok() if the real uid of the calling process
* is 0, on the assumption that it's being called by "passwd" run by root.
* This wraps pam_chauthtok and sets/restore the real uid so PAM will do
* the right thing.
*/
#ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
static int
sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
{
int result;
if (sshpam_authctxt == NULL)
fatal("PAM: sshpam_authctxt not initialized");
if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
fatal("%s: setreuid failed: %s", __func__, strerror(errno));
result = pam_chauthtok(pamh, flags);
if (setreuid(0, -1) == -1)
fatal("%s: setreuid failed: %s", __func__, strerror(errno));
return result;
}
# define pam_chauthtok(a,b) (sshpam_chauthtok_ruid((a), (b)))
#endif
void
sshpam_password_change_required(int reqd)
{
extern struct sshauthopt *auth_opts;
static int saved_port, saved_agent, saved_x11;
debug3("%s %d", __func__, reqd);
if (sshpam_authctxt == NULL)
fatal("%s: PAM authctxt not initialized", __func__);
sshpam_authctxt->force_pwchange = reqd;
if (reqd) {
saved_port = auth_opts->permit_port_forwarding_flag;
saved_agent = auth_opts->permit_agent_forwarding_flag;
saved_x11 = auth_opts->permit_x11_forwarding_flag;
auth_opts->permit_port_forwarding_flag = 0;
auth_opts->permit_agent_forwarding_flag = 0;
auth_opts->permit_x11_forwarding_flag = 0;
} else {
if (saved_port)
auth_opts->permit_port_forwarding_flag = saved_port;
if (saved_agent)
auth_opts->permit_agent_forwarding_flag = saved_agent;
if (saved_x11)
auth_opts->permit_x11_forwarding_flag = saved_x11;
}
}
/* Import regular and PAM environment from subprocess */
static void
import_environments(struct sshbuf *b)
{
char *env;
u_int n, i, num_env;
int r;
debug3("PAM: %s entering", __func__);
#ifndef UNSUPPORTED_POSIX_THREADS_HACK
/* Import variables set by do_pam_account */
if ((r = sshbuf_get_u32(b, &n)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
if (n > INT_MAX)
fatal("%s: invalid PAM account status %u", __func__, n);
sshpam_account_status = (int)n;
if ((r = sshbuf_get_u32(b, &n)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
sshpam_password_change_required(n != 0);
/* Import environment from subprocess */
if ((r = sshbuf_get_u32(b, &num_env)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
if (num_env > 1024)
fatal("%s: received %u environment variables, expected <= 1024",
__func__, num_env);
sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
debug3("PAM: num env strings %d", num_env);
for(i = 0; i < num_env; i++) {
if ((r = sshbuf_get_cstring(b, &(sshpam_env[i]), NULL)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
}
sshpam_env[num_env] = NULL;
/* Import PAM environment from subprocess */
if ((r = sshbuf_get_u32(b, &num_env)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
debug("PAM: num PAM env strings %d", num_env);
for (i = 0; i < num_env; i++) {
if ((r = sshbuf_get_cstring(b, &env, NULL)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
#ifdef HAVE_PAM_PUTENV
/* Errors are not fatal here */
if ((r = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
error("PAM: pam_putenv: %s",
pam_strerror(sshpam_handle, r));
}
#endif
/* XXX leak env? */
}
#endif
}
/*
* Conversation function for authentication thread.
*/
static int
sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
struct pam_response **resp, void *data)
{
struct sshbuf *buffer;
struct pam_ctxt *ctxt;
struct pam_response *reply;
int r, i;
u_char status;
debug3("PAM: %s entering, %d messages", __func__, n);
*resp = NULL;
if (data == NULL) {
error("PAM: conversation function passed a null context");
return (PAM_CONV_ERR);
}
ctxt = data;
if (n <= 0 || n > PAM_MAX_NUM_MSG)
return (PAM_CONV_ERR);
if ((reply = calloc(n, sizeof(*reply))) == NULL)
return PAM_CONV_ERR;
if ((buffer = sshbuf_new()) == NULL) {
free(reply);
return PAM_CONV_ERR;
}
for (i = 0; i < n; ++i) {
switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
case PAM_PROMPT_ECHO_OFF:
case PAM_PROMPT_ECHO_ON:
if ((r = sshbuf_put_cstring(buffer,
PAM_MSG_MEMBER(msg, i, msg))) != 0)
fatal("%s: buffer error: %s",
__func__, ssh_err(r));
if (ssh_msg_send(ctxt->pam_csock,
PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1)
goto fail;
if (ssh_msg_recv(ctxt->pam_csock, buffer) == -1)
goto fail;
if ((r = sshbuf_get_u8(buffer, &status)) != 0)
fatal("%s: buffer error: %s",
__func__, ssh_err(r));
if (status != PAM_AUTHTOK)
goto fail;
if ((r = sshbuf_get_cstring(buffer,
&reply[i].resp, NULL)) != 0)
fatal("%s: buffer error: %s",
__func__, ssh_err(r));
break;
case PAM_ERROR_MSG:
case PAM_TEXT_INFO:
if ((r = sshbuf_put_cstring(buffer,
PAM_MSG_MEMBER(msg, i, msg))) != 0)
fatal("%s: buffer error: %s",
__func__, ssh_err(r));
if (ssh_msg_send(ctxt->pam_csock,
PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1)
goto fail;
break;
default:
goto fail;
}
sshbuf_reset(buffer);
}
sshbuf_free(buffer);
*resp = reply;
return (PAM_SUCCESS);
fail:
for(i = 0; i < n; i++) {
free(reply[i].resp);
}
free(reply);
sshbuf_free(buffer);
return (PAM_CONV_ERR);
}
/*
* Authentication thread.
*/
static void *
sshpam_thread(void *ctxtp)
{
struct pam_ctxt *ctxt = ctxtp;
struct sshbuf *buffer = NULL;
struct pam_conv sshpam_conv;
int r, flags = (options.permit_empty_passwd == 0 ?
PAM_DISALLOW_NULL_AUTHTOK : 0);
#ifndef UNSUPPORTED_POSIX_THREADS_HACK
extern char **environ;
char **env_from_pam;
u_int i;
const char *pam_user;
const char **ptr_pam_user = &pam_user;
char *tz = getenv("TZ");
sshpam_err = pam_get_item(sshpam_handle, PAM_USER,
(sshpam_const void **)ptr_pam_user);
if (sshpam_err != PAM_SUCCESS)
goto auth_fail;
environ[0] = NULL;
if (tz != NULL)
if (setenv("TZ", tz, 1) == -1)
error("PAM: could not set TZ environment: %s",
strerror(errno));
if (sshpam_authctxt != NULL) {
setproctitle("%s [pam]",
sshpam_authctxt->valid ? pam_user : "unknown");
}
#endif
sshpam_conv.conv = sshpam_thread_conv;
sshpam_conv.appdata_ptr = ctxt;
if (sshpam_authctxt == NULL)
fatal("%s: PAM authctxt not initialized", __func__);
if ((buffer = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
(const void *)&sshpam_conv);
if (sshpam_err != PAM_SUCCESS)
goto auth_fail;
sshpam_err = pam_authenticate(sshpam_handle, flags);
if (sshpam_err == PAM_MAXTRIES)
sshpam_set_maxtries_reached(1);
if (sshpam_err != PAM_SUCCESS)
goto auth_fail;
if (!do_pam_account()) {
sshpam_err = PAM_ACCT_EXPIRED;
goto auth_fail;
}
if (sshpam_authctxt->force_pwchange) {
sshpam_err = pam_chauthtok(sshpam_handle,
PAM_CHANGE_EXPIRED_AUTHTOK);
if (sshpam_err != PAM_SUCCESS)
goto auth_fail;
sshpam_password_change_required(0);
}
if ((r = sshbuf_put_cstring(buffer, "OK")) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
#ifndef UNSUPPORTED_POSIX_THREADS_HACK
/* Export variables set by do_pam_account */
if ((r = sshbuf_put_u32(buffer, sshpam_account_status)) != 0 ||
(r = sshbuf_put_u32(buffer, sshpam_authctxt->force_pwchange)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
/* Export any environment strings set in child */
for (i = 0; environ[i] != NULL; i++) {
/* Count */
if (i > INT_MAX)
fatal("%s: too many enviornment strings", __func__);
}
if ((r = sshbuf_put_u32(buffer, i)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
for (i = 0; environ[i] != NULL; i++) {
if ((r = sshbuf_put_cstring(buffer, environ[i])) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
}
/* Export any environment strings set by PAM in child */
env_from_pam = pam_getenvlist(sshpam_handle);
for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) {
/* Count */
if (i > INT_MAX)
fatal("%s: too many PAM enviornment strings", __func__);
}
if ((r = sshbuf_put_u32(buffer, i)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) {
if ((r = sshbuf_put_cstring(buffer, env_from_pam[i])) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
}
#endif /* UNSUPPORTED_POSIX_THREADS_HACK */
/* XXX - can't do much about an error here */
ssh_msg_send(ctxt->pam_csock, sshpam_err, buffer);
sshbuf_free(buffer);
pthread_exit(NULL);
auth_fail:
if ((r = sshbuf_put_cstring(buffer,
pam_strerror(sshpam_handle, sshpam_err))) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
/* XXX - can't do much about an error here */
if (sshpam_err == PAM_ACCT_EXPIRED)
ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, buffer);
else if (sshpam_maxtries_reached)
ssh_msg_send(ctxt->pam_csock, PAM_MAXTRIES, buffer);
else
ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, buffer);
sshbuf_free(buffer);
pthread_exit(NULL);
return (NULL); /* Avoid warning for non-pthread case */
}
void
sshpam_thread_cleanup(void)
{
struct pam_ctxt *ctxt = cleanup_ctxt;
debug3("PAM: %s entering", __func__);
if (ctxt != NULL && ctxt->pam_thread != 0) {
pthread_cancel(ctxt->pam_thread);
pthread_join(ctxt->pam_thread, NULL);
close(ctxt->pam_psock);
close(ctxt->pam_csock);
memset(ctxt, 0, sizeof(*ctxt));
cleanup_ctxt = NULL;
}
}
static int
sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
struct pam_response **resp, void *data)
{
debug3("PAM: %s entering, %d messages", __func__, n);
return (PAM_CONV_ERR);
}
static struct pam_conv null_conv = { sshpam_null_conv, NULL };
static int
sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
struct pam_response **resp, void *data)
{
struct pam_response *reply;
int r, i;
debug3("PAM: %s called with %d messages", __func__, n);
*resp = NULL;
if (n <= 0 || n > PAM_MAX_NUM_MSG)
return (PAM_CONV_ERR);
if ((reply = calloc(n, sizeof(*reply))) == NULL)
return (PAM_CONV_ERR);
for (i = 0; i < n; ++i) {
switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
case PAM_ERROR_MSG:
case PAM_TEXT_INFO:
if ((r = sshbuf_putf(loginmsg, "%s\n",
PAM_MSG_MEMBER(msg, i, msg))) != 0)
fatal("%s: buffer error: %s",
__func__, ssh_err(r));
reply[i].resp_retcode = PAM_SUCCESS;
break;
default:
goto fail;
}
}
*resp = reply;
return (PAM_SUCCESS);
fail:
for(i = 0; i < n; i++) {
free(reply[i].resp);
}
free(reply);
return (PAM_CONV_ERR);
}
static struct pam_conv store_conv = { sshpam_store_conv, NULL };
void
sshpam_cleanup(void)
{
if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor()))
return;
debug("PAM: cleanup");
pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
if (sshpam_session_open) {
debug("PAM: closing session");
pam_close_session(sshpam_handle, PAM_SILENT);
sshpam_session_open = 0;
}
if (sshpam_cred_established) {
debug("PAM: deleting credentials");
pam_setcred(sshpam_handle, PAM_DELETE_CRED);
sshpam_cred_established = 0;
}
sshpam_authenticated = 0;
pam_end(sshpam_handle, sshpam_err);
sshpam_handle = NULL;
}
static int
sshpam_init(struct ssh *ssh, Authctxt *authctxt)
{
const char *pam_user, *user = authctxt->user;
const char **ptr_pam_user = &pam_user;
if (sshpam_handle == NULL) {
if (ssh == NULL) {
fatal("%s: called initially with no "
"packet context", __func__);
}
} if (sshpam_handle != NULL) {
/* We already have a PAM context; check if the user matches */
sshpam_err = pam_get_item(sshpam_handle,
PAM_USER, (sshpam_const void **)ptr_pam_user);
if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
return (0);
pam_end(sshpam_handle, sshpam_err);
sshpam_handle = NULL;
}
debug("PAM: initializing for \"%s\"", user);
sshpam_err =
pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
sshpam_authctxt = authctxt;
if (sshpam_err != PAM_SUCCESS) {
pam_end(sshpam_handle, sshpam_err);
sshpam_handle = NULL;
return (-1);
}
if (ssh != NULL && sshpam_rhost == NULL) {
/*
* We need to cache these as we don't have packet context
* during the kbdint flow.
*/
sshpam_rhost = xstrdup(auth_get_canonical_hostname(ssh,
options.use_dns));
sshpam_laddr = get_local_ipaddr(
ssh_packet_get_connection_in(ssh));
xasprintf(&sshpam_conninfo, "SSH_CONNECTION=%.50s %d %.50s %d",
ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
sshpam_laddr, ssh_local_port(ssh));
}
if (sshpam_rhost != NULL) {
debug("PAM: setting PAM_RHOST to \"%s\"", sshpam_rhost);
sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST,
sshpam_rhost);
if (sshpam_err != PAM_SUCCESS) {
pam_end(sshpam_handle, sshpam_err);
sshpam_handle = NULL;
return (-1);
}
/* Put SSH_CONNECTION in the PAM environment too */
pam_putenv(sshpam_handle, sshpam_conninfo);
}
#ifdef PAM_TTY_KLUDGE
/*
* Some silly PAM modules (e.g. pam_time) require a TTY to operate.
* sshd doesn't set the tty until too late in the auth process and
* may not even set one (for tty-less connections)
*/
debug("PAM: setting PAM_TTY to \"ssh\"");
sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
if (sshpam_err != PAM_SUCCESS) {
pam_end(sshpam_handle, sshpam_err);
sshpam_handle = NULL;
return (-1);
}
#endif
return (0);
}
static void
expose_authinfo(const char *caller)
{
char *auth_info;
/*
* Expose authentication information to PAM.
* The environment variable is versioned. Please increment the
* version suffix if the format of session_info changes.
*/
if (sshpam_authctxt->session_info == NULL)
auth_info = xstrdup("");
else if ((auth_info = sshbuf_dup_string(
sshpam_authctxt->session_info)) == NULL)
fatal("%s: sshbuf_dup_string failed", __func__);
debug2("%s: auth information in SSH_AUTH_INFO_0", caller);
do_pam_putenv("SSH_AUTH_INFO_0", auth_info);
free(auth_info);
}
static void *
sshpam_init_ctx(Authctxt *authctxt)
{
struct pam_ctxt *ctxt;
int socks[2];
debug3("PAM: %s entering", __func__);
/*
* Refuse to start if we don't have PAM enabled or do_pam_account
* has previously failed.
*/
if (!options.use_pam || sshpam_account_status == 0)
return NULL;
/* Initialize PAM */
if (sshpam_init(NULL, authctxt) == -1) {
error("PAM: initialization failed");
return (NULL);
}
expose_authinfo(__func__);
ctxt = xcalloc(1, sizeof *ctxt);
/* Start the authentication thread */
if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
error("PAM: failed create sockets: %s", strerror(errno));
free(ctxt);
return (NULL);
}
ctxt->pam_psock = socks[0];
ctxt->pam_csock = socks[1];
if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {
error("PAM: failed to start authentication thread: %s",
strerror(errno));
close(socks[0]);
close(socks[1]);
free(ctxt);
return (NULL);
}
cleanup_ctxt = ctxt;
return (ctxt);
}
static int
sshpam_query(void *ctx, char **name, char **info,
u_int *num, char ***prompts, u_int **echo_on)
{
struct sshbuf *buffer;
struct pam_ctxt *ctxt = ctx;
size_t plen;
u_char type;
char *msg;
size_t len, mlen;
int r;
debug3("PAM: %s entering", __func__);
if ((buffer = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
*name = xstrdup("");
*info = xstrdup("");
*prompts = xmalloc(sizeof(char *));
**prompts = NULL;
plen = 0;
*echo_on = xmalloc(sizeof(u_int));
while (ssh_msg_recv(ctxt->pam_psock, buffer) == 0) {
if ((r = sshbuf_get_u8(buffer, &type)) != 0 ||
(r = sshbuf_get_cstring(buffer, &msg, &mlen)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
switch (type) {
case PAM_PROMPT_ECHO_ON:
case PAM_PROMPT_ECHO_OFF:
*num = 1;
len = plen + mlen + 1;
**prompts = xreallocarray(**prompts, 1, len);
strlcpy(**prompts + plen, msg, len - plen);
plen += mlen;
**echo_on = (type == PAM_PROMPT_ECHO_ON);
free(msg);
return (0);
case PAM_ERROR_MSG:
case PAM_TEXT_INFO:
/* accumulate messages */
len = plen + mlen + 2;
**prompts = xreallocarray(**prompts, 1, len);
strlcpy(**prompts + plen, msg, len - plen);
plen += mlen;
strlcat(**prompts + plen, "\n", len - plen);
plen++;
free(msg);
break;
case PAM_ACCT_EXPIRED:
case PAM_MAXTRIES:
if (type == PAM_ACCT_EXPIRED)
sshpam_account_status = 0;
if (type == PAM_MAXTRIES)
sshpam_set_maxtries_reached(1);
/* FALLTHROUGH */
case PAM_AUTH_ERR:
debug3("PAM: %s", pam_strerror(sshpam_handle, type));
if (**prompts != NULL && strlen(**prompts) != 0) {
*info = **prompts;
**prompts = NULL;
*num = 0;
**echo_on = 0;
ctxt->pam_done = -1;
free(msg);
return 0;
}
/* FALLTHROUGH */
case PAM_SUCCESS:
if (**prompts != NULL) {
/* drain any accumulated messages */
debug("PAM: %s", **prompts);
if ((r = sshbuf_put(loginmsg, **prompts,
strlen(**prompts))) != 0)
fatal("%s: buffer error: %s",
__func__, ssh_err(r));
free(**prompts);
**prompts = NULL;
}
if (type == PAM_SUCCESS) {
if (!sshpam_authctxt->valid ||
(sshpam_authctxt->pw->pw_uid == 0 &&
options.permit_root_login != PERMIT_YES))
fatal("Internal error: PAM auth "
"succeeded when it should have "
"failed");
import_environments(buffer);
*num = 0;
**echo_on = 0;
ctxt->pam_done = 1;
free(msg);
return (0);
}
error("PAM: %s for %s%.100s from %.100s", msg,
sshpam_authctxt->valid ? "" : "illegal user ",
sshpam_authctxt->user, sshpam_rhost);
/* FALLTHROUGH */
default:
*num = 0;
**echo_on = 0;
free(msg);
ctxt->pam_done = -1;
return (-1);
}
}
return (-1);
}
/*
* Returns a junk password of identical length to that the user supplied.
* Used to mitigate timing attacks against crypt(3)/PAM stacks that
* vary processing time in proportion to password length.
*/
static char *
fake_password(const char *wire_password)
{
const char junk[] = "\b\n\r\177INCORRECT";
char *ret = NULL;
size_t i, l = wire_password != NULL ? strlen(wire_password) : 0;
if (l >= INT_MAX)
fatal("%s: password length too long: %zu", __func__, l);
ret = malloc(l + 1);
if (ret == NULL)
return NULL;
for (i = 0; i < l; i++)
ret[i] = junk[i % (sizeof(junk) - 1)];
ret[i] = '\0';
return ret;
}
/* XXX - see also comment in auth-chall.c:verify_response */
static int
sshpam_respond(void *ctx, u_int num, char **resp)
{
struct sshbuf *buffer;
struct pam_ctxt *ctxt = ctx;
char *fake;
int r;
debug2("PAM: %s entering, %u responses", __func__, num);
switch (ctxt->pam_done) {
case 1:
sshpam_authenticated = 1;
return (0);
case 0:
break;
default:
return (-1);
}
if (num != 1) {
error("PAM: expected one response, got %u", num);
return (-1);
}
if ((buffer = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
if (sshpam_authctxt->valid &&
(sshpam_authctxt->pw->pw_uid != 0 ||
options.permit_root_login == PERMIT_YES)) {
if ((r = sshbuf_put_cstring(buffer, *resp)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
} else {
fake = fake_password(*resp);
if ((r = sshbuf_put_cstring(buffer, fake)) != 0)
fatal("%s: buffer error: %s", __func__, ssh_err(r));
free(fake);
}
if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, buffer) == -1) {
sshbuf_free(buffer);
return (-1);
}
sshbuf_free(buffer);
return (1);
}
static void
sshpam_free_ctx(void *ctxtp)
{
struct pam_ctxt *ctxt = ctxtp;
debug3("PAM: %s entering", __func__);
sshpam_thread_cleanup();
free(ctxt);
/*
* We don't call sshpam_cleanup() here because we may need the PAM
* handle at a later stage, e.g. when setting up a session. It's
* still on the cleanup list, so pam_end() *will* be called before
* the server process terminates.
*/
}