- (djm) Release 4.6p1

[openssh-git.git] / auth-pam.c

/*-
 * 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 Exp $ */
#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

/* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
#ifdef PAM_SUN_CODEBASE
# define sshpam_const           /* Solaris, HP-UX, AIX */
#else
# define sshpam_const   const   /* LinuxPAM, OpenPAM */
#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 "buffer.h"
#include "key.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 Buffer loginmsg;
extern int compat20;
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;
#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);
                if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)
                    <= 0)
                        return; /* could not wait */
        }
        if (WIFSIGNALED(sshpam_thread_status) &&
            WTERMSIG(sshpam_thread_status) == SIGTERM)
                return; /* terminated by pthread_cancel */
        if (!WIFEXITED(sshpam_thread_status))
                fatal("PAM: authentication thread exited unexpectedly");
        if (WEXITSTATUS(sshpam_thread_status) != 0)
                fatal("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);
        waitpid(thread, &status, 0);
        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 char **sshpam_env = NULL;
static Authctxt *sshpam_authctxt = NULL;
static const char *sshpam_password = NULL;
static char badpw[] = "\b\n\r\177INCORRECT";

/* 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)
{
        debug3("%s %d", __func__, reqd);
        if (sshpam_authctxt == NULL)
                fatal("%s: PAM authctxt not initialized", __func__);
        sshpam_authctxt->force_pwchange = reqd;
        if (reqd) {
                no_port_forwarding_flag |= 2;
                no_agent_forwarding_flag |= 2;
                no_x11_forwarding_flag |= 2;
        } else {
                no_port_forwarding_flag &= ~2;
                no_agent_forwarding_flag &= ~2;
                no_x11_forwarding_flag &= ~2;
        }
}

/* Import regular and PAM environment from subprocess */
static void
import_environments(Buffer *b)
{
        char *env;
        u_int i, num_env;
        int err;

        debug3("PAM: %s entering", __func__);

#ifndef UNSUPPORTED_POSIX_THREADS_HACK
        /* Import variables set by do_pam_account */
        sshpam_account_status = buffer_get_int(b);
        sshpam_password_change_required(buffer_get_int(b));

        /* Import environment from subprocess */
        num_env = buffer_get_int(b);
        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++)
                sshpam_env[i] = buffer_get_string(b, NULL);

        sshpam_env[num_env] = NULL;

        /* Import PAM environment from subprocess */
        num_env = buffer_get_int(b);
        debug("PAM: num PAM env strings %d", num_env);
        for(i = 0; i < num_env; i++) {
                env = buffer_get_string(b, NULL);

#ifdef HAVE_PAM_PUTENV
                /* Errors are not fatal here */
                if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
                        error("PAM: pam_putenv: %s",
                            pam_strerror(sshpam_handle, sshpam_err));
                }
#endif
        }
#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)
{
        Buffer buffer;
        struct pam_ctxt *ctxt;
        struct pam_response *reply;
        int i;

        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);

        buffer_init(&buffer);
        for (i = 0; i < n; ++i) {
                switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
                case PAM_PROMPT_ECHO_OFF:
                        buffer_put_cstring(&buffer,
                            PAM_MSG_MEMBER(msg, i, msg));
                        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 (buffer_get_char(&buffer) != PAM_AUTHTOK)
                                goto fail;
                        reply[i].resp = buffer_get_string(&buffer, NULL);
                        break;
                case PAM_PROMPT_ECHO_ON:
                        buffer_put_cstring(&buffer,
                            PAM_MSG_MEMBER(msg, i, msg));
                        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 (buffer_get_char(&buffer) != PAM_AUTHTOK)
                                goto fail;
                        reply[i].resp = buffer_get_string(&buffer, NULL);
                        break;
                case PAM_ERROR_MSG:
                        buffer_put_cstring(&buffer,
                            PAM_MSG_MEMBER(msg, i, msg));
                        if (ssh_msg_send(ctxt->pam_csock,
                            PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
                                goto fail;
                        break;
                case PAM_TEXT_INFO:
                        buffer_put_cstring(&buffer,
                            PAM_MSG_MEMBER(msg, i, msg));
                        if (ssh_msg_send(ctxt->pam_csock,
                            PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
                                goto fail;
                        break;
                default:
                        goto fail;
                }
                buffer_clear(&buffer);
        }
        buffer_free(&buffer);
        *resp = reply;
        return (PAM_SUCCESS);

 fail:
        for(i = 0; i < n; i++) {
                if (reply[i].resp != NULL)
                        xfree(reply[i].resp);
        }
        xfree(reply);
        buffer_free(&buffer);
        return (PAM_CONV_ERR);
}

/*
 * Authentication thread.
 */
static void *
sshpam_thread(void *ctxtp)
{
        struct pam_ctxt *ctxt = ctxtp;
        Buffer buffer;
        struct pam_conv sshpam_conv;
        int 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");

        pam_get_item(sshpam_handle, PAM_USER,
            (sshpam_const void **)ptr_pam_user);

        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__);

        buffer_init(&buffer);
        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_SUCCESS)
                goto auth_fail;

        if (compat20) {
                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);
                }
        }

        buffer_put_cstring(&buffer, "OK");

#ifndef UNSUPPORTED_POSIX_THREADS_HACK
        /* Export variables set by do_pam_account */
        buffer_put_int(&buffer, sshpam_account_status);
        buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);

        /* Export any environment strings set in child */
        for(i = 0; environ[i] != NULL; i++)
                ; /* Count */
        buffer_put_int(&buffer, i);
        for(i = 0; environ[i] != NULL; i++)
                buffer_put_cstring(&buffer, environ[i]);

        /* 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 */
        buffer_put_int(&buffer, i);
        for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
                buffer_put_cstring(&buffer, env_from_pam[i]);
#endif /* UNSUPPORTED_POSIX_THREADS_HACK */

        /* XXX - can't do much about an error here */
        ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
        buffer_free(&buffer);
        pthread_exit(NULL);

 auth_fail:
        buffer_put_cstring(&buffer,
            pam_strerror(sshpam_handle, sshpam_err));
        /* 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
                ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);
        buffer_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 i;
        size_t len;

        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:
                        len = strlen(PAM_MSG_MEMBER(msg, i, msg));
                        buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len);
                        buffer_append(&loginmsg, "\n", 1 );
                        reply[i].resp_retcode = PAM_SUCCESS;
                        break;
                default:
                        goto fail;
                }
        }
        *resp = reply;
        return (PAM_SUCCESS);

 fail:
        for(i = 0; i < n; i++) {
                if (reply[i].resp != NULL)
                        xfree(reply[i].resp);
        }
        xfree(reply);
        return (PAM_CONV_ERR);
}

static struct pam_conv store_conv = { sshpam_store_conv, NULL };

void
sshpam_cleanup(void)
{
        debug("PAM: cleanup");
        if (sshpam_handle == NULL)
                return;
        pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
        if (sshpam_cred_established) {
                pam_setcred(sshpam_handle, PAM_DELETE_CRED);
                sshpam_cred_established = 0;
        }
        if (sshpam_session_open) {
                pam_close_session(sshpam_handle, PAM_SILENT);
                sshpam_session_open = 0;
        }
        sshpam_authenticated = 0;
        pam_end(sshpam_handle, sshpam_err);
        sshpam_handle = NULL;
}

static int
sshpam_init(Authctxt *authctxt)
{
        extern char *__progname;
        const char *pam_rhost, *pam_user, *user = authctxt->user;
        const char **ptr_pam_user = &pam_user;

        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);
        }
        pam_rhost = get_remote_name_or_ip(utmp_len, options.use_dns);
        debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost);
        sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost);
        if (sshpam_err != PAM_SUCCESS) {
                pam_end(sshpam_handle, sshpam_err);
                sshpam_handle = NULL;
                return (-1);
        }
#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 *
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(authctxt) == -1) {
                error("PAM: initialization failed");
                return (NULL);
        }

        ctxt = xmalloc(sizeof *ctxt);
        memset(ctxt, 0, sizeof(*ctxt));

        /* Start the authentication thread */
        if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
                error("PAM: failed create sockets: %s", strerror(errno));
                xfree(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]);
                xfree(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)
{
        Buffer buffer;
        struct pam_ctxt *ctxt = ctx;
        size_t plen;
        u_char type;
        char *msg;
        size_t len, mlen;

        debug3("PAM: %s entering", __func__);
        buffer_init(&buffer);
        *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) {
                type = buffer_get_char(&buffer);
                msg = buffer_get_string(&buffer, NULL);
                mlen = strlen(msg);
                switch (type) {
                case PAM_PROMPT_ECHO_ON:
                case PAM_PROMPT_ECHO_OFF:
                        *num = 1;
                        len = plen + mlen + 1;
                        **prompts = xrealloc(**prompts, 1, len);
                        strlcpy(**prompts + plen, msg, len - plen);
                        plen += mlen;
                        **echo_on = (type == PAM_PROMPT_ECHO_ON);
                        xfree(msg);
                        return (0);
                case PAM_ERROR_MSG:
                case PAM_TEXT_INFO:
                        /* accumulate messages */
                        len = plen + mlen + 2;
                        **prompts = xrealloc(**prompts, 1, len);
                        strlcpy(**prompts + plen, msg, len - plen);
                        plen += mlen;
                        strlcat(**prompts + plen, "\n", len - plen);
                        plen++;
                        xfree(msg);
                        break;
                case PAM_ACCT_EXPIRED:
                        sshpam_account_status = 0;
                        /* 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;
                                xfree(msg);
                                return 0;
                        }
                        /* FALLTHROUGH */
                case PAM_SUCCESS:
                        if (**prompts != NULL) {
                                /* drain any accumulated messages */
                                debug("PAM: %s", **prompts);
                                buffer_append(&loginmsg, **prompts,
                                    strlen(**prompts));
                                xfree(**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;
                                xfree(msg);
                                return (0);
                        }
                        error("PAM: %s for %s%.100s from %.100s", msg,
                            sshpam_authctxt->valid ? "" : "illegal user ",
                            sshpam_authctxt->user,
                            get_remote_name_or_ip(utmp_len, options.use_dns));
                        /* FALLTHROUGH */
                default:
                        *num = 0;
                        **echo_on = 0;
                        xfree(msg);
                        ctxt->pam_done = -1;
                        return (-1);
                }
        }
        return (-1);
}

/* XXX - see also comment in auth-chall.c:verify_response */
static int
sshpam_respond(void *ctx, u_int num, char **resp)
{
        Buffer buffer;
        struct pam_ctxt *ctxt = ctx;

        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);
        }
        buffer_init(&buffer);
        if (sshpam_authctxt->valid &&
            (sshpam_authctxt->pw->pw_uid != 0 ||
            options.permit_root_login == PERMIT_YES))
                buffer_put_cstring(&buffer, *resp);
        else
                buffer_put_cstring(&buffer, badpw);
        if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
                buffer_free(&buffer);
                return (-1);
        }
        buffer_free(&buffer);
        return (1);
}

static void
sshpam_free_ctx(void *ctxtp)
{
        struct pam_ctxt *ctxt = ctxtp;

        debug3("PAM: %s entering", __func__);
        sshpam_thread_cleanup();
        xfree(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.
         */
}

KbdintDevice sshpam_device = {
        "pam",
        sshpam_init_ctx,
        sshpam_query,
        sshpam_respond,
        sshpam_free_ctx
};

KbdintDevice mm_sshpam_device = {
        "pam",
        mm_sshpam_init_ctx,
        mm_sshpam_query,
        mm_sshpam_respond,
        mm_sshpam_free_ctx
};

/*
 * This replaces auth-pam.c
 */
void
start_pam(Authctxt *authctxt)
{
        if (!options.use_pam)
                fatal("PAM: initialisation requested when UsePAM=no");

        if (sshpam_init(authctxt) == -1)
                fatal("PAM: initialisation failed");
}

void
finish_pam(void)
{
        sshpam_cleanup();
}

u_int
do_pam_account(void)
{
        debug("%s: called", __func__);
        if (sshpam_account_status != -1)
                return (sshpam_account_status);

        sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
        debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
            pam_strerror(sshpam_handle, sshpam_err));

        if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
                sshpam_account_status = 0;
                return (sshpam_account_status);
        }

        if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
                sshpam_password_change_required(1);

        sshpam_account_status = 1;
        return (sshpam_account_status);
}

void
do_pam_set_tty(const char *tty)
{
        if (tty != NULL) {
                debug("PAM: setting PAM_TTY to \"%s\"", tty);
                sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
                if (sshpam_err != PAM_SUCCESS)
                        fatal("PAM: failed to set PAM_TTY: %s",
                            pam_strerror(sshpam_handle, sshpam_err));
        }
}

void
do_pam_setcred(int init)
{
        sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
            (const void *)&store_conv);
        if (sshpam_err != PAM_SUCCESS)
                fatal("PAM: failed to set PAM_CONV: %s",
                    pam_strerror(sshpam_handle, sshpam_err));
        if (init) {
                debug("PAM: establishing credentials");
                sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
        } else {
                debug("PAM: reinitializing credentials");
                sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
        }
        if (sshpam_err == PAM_SUCCESS) {
                sshpam_cred_established = 1;
                return;
        }
        if (sshpam_authenticated)
                fatal("PAM: pam_setcred(): %s",
                    pam_strerror(sshpam_handle, sshpam_err));
        else
                debug("PAM: pam_setcred(): %s",
                    pam_strerror(sshpam_handle, sshpam_err));
}

static int
sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
    struct pam_response **resp, void *data)
{
        char input[PAM_MAX_MSG_SIZE];
        struct pam_response *reply;
        int i;

        debug3("PAM: %s called with %d messages", __func__, n);

        *resp = NULL;

        if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
                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_PROMPT_ECHO_OFF:
                        reply[i].resp =
                            read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
                            RP_ALLOW_STDIN);
                        reply[i].resp_retcode = PAM_SUCCESS;
                        break;
                case PAM_PROMPT_ECHO_ON:
                        fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
                        fgets(input, sizeof input, stdin);
                        if ((reply[i].resp = strdup(input)) == NULL)
                                goto fail;
                        reply[i].resp_retcode = PAM_SUCCESS;
                        break;
                case PAM_ERROR_MSG:
                case PAM_TEXT_INFO:
                        fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
                        reply[i].resp_retcode = PAM_SUCCESS;
                        break;
                default:
                        goto fail;
                }
        }
        *resp = reply;
        return (PAM_SUCCESS);

 fail:
        for(i = 0; i < n; i++) {
                if (reply[i].resp != NULL)
                        xfree(reply[i].resp);
        }
        xfree(reply);
        return (PAM_CONV_ERR);
}

static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };

/*
 * XXX this should be done in the authentication phase, but ssh1 doesn't
 * support that
 */
void
do_pam_chauthtok(void)
{
        if (use_privsep)
                fatal("Password expired (unable to change with privsep)");
        sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
            (const void *)&tty_conv);
        if (sshpam_err != PAM_SUCCESS)
                fatal("PAM: failed to set PAM_CONV: %s",
                    pam_strerror(sshpam_handle, sshpam_err));
        debug("PAM: changing password");
        sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
        if (sshpam_err != PAM_SUCCESS)
                fatal("PAM: pam_chauthtok(): %s",
                    pam_strerror(sshpam_handle, sshpam_err));
}

void
do_pam_session(void)
{
        debug3("PAM: opening session");
        sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
            (const void *)&store_conv);
        if (sshpam_err != PAM_SUCCESS)
                fatal("PAM: failed to set PAM_CONV: %s",
                    pam_strerror(sshpam_handle, sshpam_err));
        sshpam_err = pam_open_session(sshpam_handle, 0);
        if (sshpam_err == PAM_SUCCESS)
                sshpam_session_open = 1;
        else {
                sshpam_session_open = 0;
                disable_forwarding();
                error("PAM: pam_open_session(): %s",
                    pam_strerror(sshpam_handle, sshpam_err));
        }

}

int
is_pam_session_open(void)
{
        return sshpam_session_open;
}

/*
 * Set a PAM environment string. We need to do this so that the session
 * modules can handle things like Kerberos/GSI credentials that appear
 * during the ssh authentication process.
 */
int
do_pam_putenv(char *name, char *value)
{
        int ret = 1;
#ifdef HAVE_PAM_PUTENV
        char *compound;
        size_t len;

        len = strlen(name) + strlen(value) + 2;
        compound = xmalloc(len);

        snprintf(compound, len, "%s=%s", name, value);
        ret = pam_putenv(sshpam_handle, compound);
        xfree(compound);
#endif

        return (ret);
}

char **
fetch_pam_child_environment(void)
{
        return sshpam_env;
}

char **
fetch_pam_environment(void)
{
        return (pam_getenvlist(sshpam_handle));
}

void
free_pam_environment(char **env)
{
        char **envp;

        if (env == NULL)
                return;

        for (envp = env; *envp; envp++)
                xfree(*envp);
        xfree(env);
}

/*
 * "Blind" conversation function for password authentication.  Assumes that
 * echo-off prompts are for the password and stores messages for later
 * display.
 */
static int
sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
    struct pam_response **resp, void *data)
{
        struct pam_response *reply;
        int i;
        size_t len;

        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 = malloc(n * sizeof(*reply))) == NULL)
                return (PAM_CONV_ERR);
        memset(reply, 0, n * sizeof(*reply));

        for (i = 0; i < n; ++i) {
                switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
                case PAM_PROMPT_ECHO_OFF:
                        if (sshpam_password == NULL)
                                goto fail;
                        if ((reply[i].resp = strdup(sshpam_password)) == NULL)
                                goto fail;
                        reply[i].resp_retcode = PAM_SUCCESS;
                        break;
                case PAM_ERROR_MSG:
                case PAM_TEXT_INFO:
                        len = strlen(PAM_MSG_MEMBER(msg, i, msg));
                        if (len > 0) {
                                buffer_append(&loginmsg,
                                    PAM_MSG_MEMBER(msg, i, msg), len);
                                buffer_append(&loginmsg, "\n", 1);
                        }
                        if ((reply[i].resp = strdup("")) == NULL)
                                goto fail;
                        reply[i].resp_retcode = PAM_SUCCESS;
                        break;
                default:
                        goto fail;
                }
        }
        *resp = reply;
        return (PAM_SUCCESS);

 fail:
        for(i = 0; i < n; i++) {
                if (reply[i].resp != NULL)
                        xfree(reply[i].resp);
        }
        xfree(reply);
        return (PAM_CONV_ERR);
}

static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };

/*
 * Attempt password authentication via PAM
 */
int
sshpam_auth_passwd(Authctxt *authctxt, const char *password)
{
        int flags = (options.permit_empty_passwd == 0 ?
            PAM_DISALLOW_NULL_AUTHTOK : 0);

        if (!options.use_pam || sshpam_handle == NULL)
                fatal("PAM: %s called when PAM disabled or failed to "
                    "initialise.", __func__);

        sshpam_password = password;
        sshpam_authctxt = authctxt;

        /*
         * If the user logging in is invalid, or is root but is not permitted
         * by PermitRootLogin, use an invalid password to prevent leaking
         * information via timing (eg if the PAM config has a delay on fail).
         */
        if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
            options.permit_root_login != PERMIT_YES))
                sshpam_password = badpw;

        sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
            (const void *)&passwd_conv);
        if (sshpam_err != PAM_SUCCESS)
                fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
                    pam_strerror(sshpam_handle, sshpam_err));

        sshpam_err = pam_authenticate(sshpam_handle, flags);
        sshpam_password = NULL;
        if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
                debug("PAM: password authentication accepted for %.100s",
                    authctxt->user);
                return 1;
        } else {
                debug("PAM: password authentication failed for %.100s: %s",
                    authctxt->valid ? authctxt->user : "an illegal user",
                    pam_strerror(sshpam_handle, sshpam_err));
                return 0;
        }
}
#endif /* USE_PAM */