/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (c) 1980, 1987, 1988, 1991, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 * Copyright (c) 2002 Networks Associates Technologies, Inc.
 * All rights reserved.
 *
 * Portions of this software were 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

#include <sys/cdefs.h>
/*
 * login [ name ]
 * login -h hostname    (for telnetd, etc.)
 * login -f name        (for pre-authenticated login: datakit, xterm, etc.)
 */

#include <sys/param.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/wait.h>

#include <err.h>
#include <errno.h>
#include <grp.h>
#include <login_cap.h>
#include <pwd.h>
#include <setjmp.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <ttyent.h>
#include <unistd.h>

#include <security/pam_appl.h>
#include <security/openpam.h>

#include "login.h"
#include "pathnames.h"

static int               auth_pam(void);
static void              bail(int, int);
static void              bail_internal(int, int, int);
static int               export(const char *);
static void              export_pam_environment(void);
static int               motd(const char *);
static void              badlogin(char *);
static char             *getloginname(void);
static void              pam_syslog(const char *);
static void              pam_cleanup(void);
static void              refused(const char *, const char *, int);
static const char       *stypeof(char *);
static void              sigint(int);
static void              timedout(int);
static void              bail_sig(int);
static void              usage(void);

#define TTYGRPNAME              "tty"                   /* group to own ttys */
#define DEFAULT_BACKOFF         3
#define DEFAULT_RETRIES         10
#define DEFAULT_PROMPT          "login: "
#define DEFAULT_PASSWD_PROMPT   "Password:"
#define TERM_UNKNOWN            "su"
#define DEFAULT_WARN            (2L * 7L * 86400L)      /* Two weeks */
#define NO_SLEEP_EXIT           0
#define SLEEP_EXIT              5

/*
 * This bounds the time given to login.  Not a define so it can
 * be patched on machines where it's too small.
 */
static u_int            timeout = 300;

/* Buffer for signal handling of timeout */
static jmp_buf           timeout_buf;

char                     pwbuf[1024];
struct passwd            pwres;
struct passwd           *pwd;
static int               failures;

static char             *envinit[1];    /* empty environment list */

/*
 * Command line flags and arguments
 */
static int               fflag;         /* -f: do not perform authentication */
static int               hflag;         /* -h: login from remote host */
static char             *hostname;      /* hostname from command line */
static int               pflag;         /* -p: preserve environment */

/*
 * User name
 */
static char             *username;      /* user name */
static char             *olduser;       /* previous user name */

/*
 * Prompts
 */
static char              default_prompt[] = DEFAULT_PROMPT;
static const char       *prompt;
static char              default_passwd_prompt[] = DEFAULT_PASSWD_PROMPT;
static const char       *passwd_prompt;

static char             *tty;

/*
 * PAM data
 */
static pam_handle_t     *pamh = NULL;
static struct pam_conv   pamc = { openpam_ttyconv, NULL };
static int               pam_err;
static int               pam_silent = PAM_SILENT;
static int               pam_cred_established;
static int               pam_session_established;

int
main(int argc, char *argv[])
{
        struct group *gr;
        struct stat st;
        int retries, backoff;
        int ask, ch, cnt, quietlog, rootlogin, rval;
        uid_t uid, euid;
        gid_t egid;
        char *term;
        char *p, *ttyn;
        char tname[sizeof(_PATH_TTY) + 10];
        char *arg0;
        const char *tp;
        const char *shell = NULL;
        login_cap_t *lc = NULL;
        login_cap_t *lc_user = NULL;
        pid_t pid;
        sigset_t mask, omask;
        struct sigaction sa;
#ifdef USE_BSM_AUDIT
        char auditsuccess = 1;
#endif

        sa.sa_flags = SA_RESTART;
        (void)sigfillset(&sa.sa_mask);
        sa.sa_handler = SIG_IGN;
        (void)sigaction(SIGQUIT, &sa, NULL);
        (void)sigaction(SIGINT, &sa, NULL);
        (void)sigaction(SIGHUP, &sa, NULL);
        if (setjmp(timeout_buf)) {
                if (failures)
                        badlogin(username);
                (void)fprintf(stderr, "Login timed out after %d seconds\n",
                    timeout);
                bail(NO_SLEEP_EXIT, 0);
        }
        sa.sa_handler = timedout;
        (void)sigaction(SIGALRM, &sa, NULL);
        (void)alarm(timeout);
        (void)setpriority(PRIO_PROCESS, 0, 0);

        openlog("login", LOG_CONS, LOG_AUTH);

        uid = getuid();
        euid = geteuid();
        egid = getegid();

        while ((ch = getopt(argc, argv, "fh:p")) != -1)
                switch (ch) {
                case 'f':
                        fflag = 1;
                        break;
                case 'h':
                        if (uid != 0)
                                errx(1, "-h option: %s", strerror(EPERM));
                        if (strlen(optarg) >= MAXHOSTNAMELEN)
                                errx(1, "-h option: %s: exceeds maximum "
                                    "hostname size", optarg);
                        hflag = 1;
                        hostname = optarg;
                        break;
                case 'p':
                        pflag = 1;
                        break;
                case '?':
                default:
                        if (uid == 0)
                                syslog(LOG_ERR, "invalid flag %c", ch);
                        usage();
                }
        argc -= optind;
        argv += optind;

        if (argc > 0) {
                username = strdup(*argv);
                if (username == NULL)
                        err(1, "strdup()");
                ask = 0;
        } else {
                ask = 1;
        }

        setproctitle("-%s", getprogname());

        closefrom(3);

        /*
         * Get current TTY
         */
        ttyn = ttyname(STDIN_FILENO);
        if (ttyn == NULL || *ttyn == '\0') {
                (void)snprintf(tname, sizeof(tname), "%s??", _PATH_TTY);
                ttyn = tname;
        }
        if (strncmp(ttyn, _PATH_DEV, sizeof _PATH_DEV - 1) == 0)
                tty = ttyn + sizeof _PATH_DEV - 1;
        else
                tty = ttyn;

        /*
         * Get "login-retries" & "login-backoff" from default class
         */
        lc = login_getclass(NULL);
        prompt = login_getcapstr(lc, "login_prompt",
            default_prompt, default_prompt);
        passwd_prompt = login_getcapstr(lc, "passwd_prompt",
            default_passwd_prompt, default_passwd_prompt);
        retries = login_getcapnum(lc, "login-retries",
            DEFAULT_RETRIES, DEFAULT_RETRIES);
        backoff = login_getcapnum(lc, "login-backoff",
            DEFAULT_BACKOFF, DEFAULT_BACKOFF);
        login_close(lc);
        lc = NULL;

        /*
         * Try to authenticate the user until we succeed or time out.
         */
        for (cnt = 0;; ask = 1) {
                if (ask) {
                        fflag = 0;
                        if (olduser != NULL)
                                free(olduser);
                        olduser = username;
                        username = getloginname();
                }
                rootlogin = 0;

                /*
                 * Note if trying multiple user names; log failures for
                 * previous user name, but don't bother logging one failure
                 * for nonexistent name (mistyped username).
                 */
                if (failures && strcmp(olduser, username) != 0) {
                        if (failures > (pwd ? 0 : 1))
                                badlogin(olduser);
                }

                /*
                 * Load the PAM policy and set some variables
                 */
                pam_err = pam_start("login", username, &pamc, &pamh);
                if (pam_err != PAM_SUCCESS) {
                        pam_syslog("pam_start()");
#ifdef USE_BSM_AUDIT
                        au_login_fail("PAM Error", 1);
#endif
                        bail(NO_SLEEP_EXIT, 1);
                }
                pam_err = pam_set_item(pamh, PAM_TTY, tty);
                if (pam_err != PAM_SUCCESS) {
                        pam_syslog("pam_set_item(PAM_TTY)");
#ifdef USE_BSM_AUDIT
                        au_login_fail("PAM Error", 1);
#endif
                        bail(NO_SLEEP_EXIT, 1);
                }
                pam_err = pam_set_item(pamh, PAM_RHOST, hostname);
                if (pam_err != PAM_SUCCESS) {
                        pam_syslog("pam_set_item(PAM_RHOST)");
#ifdef USE_BSM_AUDIT
                        au_login_fail("PAM Error", 1);
#endif
                        bail(NO_SLEEP_EXIT, 1);
                }

                (void)getpwnam_r(username, &pwres, pwbuf, sizeof(pwbuf), &pwd);
                if (pwd != NULL && pwd->pw_uid == 0)
                        rootlogin = 1;

                /*
                 * If the -f option was specified and the caller is
                 * root or the caller isn't changing their uid, don't
                 * authenticate.
                 */
                if (pwd != NULL && fflag &&
                    (uid == (uid_t)0 || uid == (uid_t)pwd->pw_uid)) {
                        /* already authenticated */
                        rval = 0;
#ifdef USE_BSM_AUDIT
                        auditsuccess = 0; /* opened a terminal window only */
#endif
                } else {
                        fflag = 0;
                        (void)setpriority(PRIO_PROCESS, 0, -4);
                        rval = auth_pam();
                        (void)setpriority(PRIO_PROCESS, 0, 0);
                }

                if (pwd != NULL && rval == 0)
                        break;

                pam_cleanup();

                /*
                 * We are not exiting here, but this corresponds to a failed
                 * login event, so set exitstatus to 1.
                 */
#ifdef USE_BSM_AUDIT
                au_login_fail("Login incorrect", 1);
#endif

                (void)printf("Login incorrect\n");
                failures++;

                pwd = NULL;

                /*
                 * Allow up to 'retry' (10) attempts, but start
                 * backing off after 'backoff' (3) attempts.
                 */
                if (++cnt > backoff) {
                        if (cnt >= retries) {
                                badlogin(username);
                                bail(SLEEP_EXIT, 1);
                        }
                        sleep((u_int)((cnt - backoff) * 5));
                }
        }

        /* committed to login -- turn off timeout */
        (void)alarm((u_int)0);

        (void)sigemptyset(&mask);
        (void)sigaddset(&mask, SIGHUP);
        (void)sigaddset(&mask, SIGTERM);
        (void)sigprocmask(SIG_BLOCK, &mask, &omask);
        sa.sa_handler = bail_sig;
        (void)sigaction(SIGHUP, &sa, NULL);
        (void)sigaction(SIGTERM, &sa, NULL);

        endpwent();

#ifdef USE_BSM_AUDIT
        /* Audit successful login. */
        if (auditsuccess)
                au_login_success();
#endif

        /*
         * This needs to happen before login_getpwclass to support
         * home directories on GSS-API authenticated NFS where the
         * kerberos credentials need to be saved so that the kernel
         * can authenticate to the NFS server.
         */
        pam_err = pam_setcred(pamh, pam_silent|PAM_ESTABLISH_CRED);
        if (pam_err != PAM_SUCCESS) {
                pam_syslog("pam_setcred()");
                bail(NO_SLEEP_EXIT, 1);
        }
        pam_cred_established = 1;

        /*
         * Establish the login class.
         */
        lc = login_getpwclass(pwd);
        lc_user = login_getuserclass(pwd);

        if (!(quietlog = login_getcapbool(lc_user, "hushlogin", 0)))
                quietlog = login_getcapbool(lc, "hushlogin", 0);

        /*
         * Switching needed for NFS with root access disabled.
         *
         * XXX: This change fails to modify the additional groups for the
         * process, and as such, may restrict rights normally granted
         * through those groups.
         */
        (void)setegid(pwd->pw_gid);
        (void)seteuid(rootlogin ? 0 : pwd->pw_uid);
        if (!*pwd->pw_dir || chdir(pwd->pw_dir) < 0) {
                if (login_getcapbool(lc, "requirehome", 0))
                        refused("Home directory not available", "HOMEDIR", 1);
                if (chdir("/") < 0)
                        refused("Cannot find root directory", "ROOTDIR", 1);
                if (!quietlog || *pwd->pw_dir)
                        printf("No home directory.\nLogging in with home = \"/\".\n");
                pwd->pw_dir = strdup("/");
                if (pwd->pw_dir == NULL) {
                        syslog(LOG_NOTICE, "strdup(): %m");
                        bail(SLEEP_EXIT, 1);
                }
        }
        (void)seteuid(euid);
        (void)setegid(egid);
        if (!quietlog) {
                quietlog = access(_PATH_HUSHLOGIN, F_OK) == 0;
                if (!quietlog)
                        pam_silent = 0;
        }

        shell = login_getcapstr(lc, "shell", pwd->pw_shell, pwd->pw_shell);
        if (*pwd->pw_shell == '\0')
                pwd->pw_shell = strdup(_PATH_BSHELL);
        if (pwd->pw_shell == NULL) {
                syslog(LOG_NOTICE, "strdup(): %m");
                bail(SLEEP_EXIT, 1);
        }
        if (*shell == '\0')   /* Not overridden */
                shell = pwd->pw_shell;
        if ((shell = strdup(shell)) == NULL) {
                syslog(LOG_NOTICE, "strdup(): %m");
                bail(SLEEP_EXIT, 1);
        }

        /*
         * Set device protections, depending on what terminal the
         * user is logged in. This feature is used on Suns to give
         * console users better privacy.
         */
        login_fbtab(tty, pwd->pw_uid, pwd->pw_gid);

        /*
         * Clear flags of the tty.  None should be set, and when the
         * user sets them otherwise, this can cause the chown to fail.
         * Since it isn't clear that flags are useful on character
         * devices, we just clear them.
         *
         * We don't log in the case of EOPNOTSUPP because dev might be
         * on NFS, which doesn't support chflags.
         *
         * We don't log in the EROFS because that means that /dev is on
         * a read only file system and we assume that the permissions there
         * are sane.
         */
        if (ttyn != tname && chflags(ttyn, 0))
                if (errno != EOPNOTSUPP && errno != EROFS)
                        syslog(LOG_ERR, "chflags(%s): %m", ttyn);
        if (ttyn != tname && chown(ttyn, pwd->pw_uid,
            (gr = getgrnam(TTYGRPNAME)) ? gr->gr_gid : pwd->pw_gid))
                if (errno != EROFS)
                        syslog(LOG_ERR, "chown(%s): %m", ttyn);

#ifdef LOGALL
        /*
         * Syslog each successful login, so we don't have to watch
         * hundreds of wtmp or lastlogin files.
         */
        if (hflag)
                syslog(LOG_INFO, "login from %s on %s as %s",
                       hostname, tty, pwd->pw_name);
        else
                syslog(LOG_INFO, "login on %s as %s",
                       tty, pwd->pw_name);
#endif

        /*
         * If fflag is on, assume caller/authenticator has logged root
         * login.
         */
        if (rootlogin && fflag == 0) {
                if (hflag)
                        syslog(LOG_NOTICE, "ROOT LOGIN (%s) ON %s FROM %s",
                            username, tty, hostname);
                else
                        syslog(LOG_NOTICE, "ROOT LOGIN (%s) ON %s",
                            username, tty);
        }

        /*
         * Destroy environment unless user has requested its
         * preservation - but preserve TERM in all cases
         */
        term = getenv("TERM");
        if (!pflag)
                environ = envinit;
        if (term != NULL)
                setenv("TERM", term, 0);

        /*
         * PAM modules might add supplementary groups during pam_setcred().
         */
        if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) != 0) {
                syslog(LOG_ERR, "setusercontext() failed - exiting");
                bail(NO_SLEEP_EXIT, 1);
        }

        pam_err = pam_setcred(pamh, pam_silent|PAM_REINITIALIZE_CRED);
        if (pam_err != PAM_SUCCESS) {
                pam_syslog("pam_setcred()");
                bail(NO_SLEEP_EXIT, 1);
        }

        pam_err = pam_open_session(pamh, pam_silent);
        if (pam_err != PAM_SUCCESS) {
                pam_syslog("pam_open_session()");
                bail(NO_SLEEP_EXIT, 1);
        }
        pam_session_established = 1;

        /*
         * We must fork() before setuid() because we need to call
         * pam_close_session() as root.
         */
        pid = fork();
        if (pid < 0) {
                err(1, "fork");
        } else if (pid != 0) {
                /*
                 * Parent: wait for child to finish, then clean up
                 * session.
                 *
                 * If we get SIGHUP or SIGTERM, clean up the session
                 * and exit right away. This will make the terminal
                 * inaccessible and send SIGHUP to the foreground
                 * process group.
                 */
                int status;
                setproctitle("-%s [pam]", getprogname());
                (void)sigprocmask(SIG_SETMASK, &omask, NULL);
                waitpid(pid, &status, 0);
                (void)sigprocmask(SIG_BLOCK, &mask, NULL);
                bail(NO_SLEEP_EXIT, 0);
        }

        /*
         * NOTICE: We are now in the child process!
         */

        /*
         * Add any environment variables the PAM modules may have set.
         */
        export_pam_environment();

        /*
         * We're done with PAM now; our parent will deal with the rest.
         */
        pam_end(pamh, 0);
        pamh = NULL;

        /*
         * We don't need to be root anymore, so set the login name and
         * the UID.
         */
        if (setlogin(username) != 0) {
                syslog(LOG_ERR, "setlogin(%s): %m - exiting", username);
                bail(NO_SLEEP_EXIT, 1);
        }
        if (setusercontext(lc, pwd, pwd->pw_uid,
            LOGIN_SETALL & ~(LOGIN_SETLOGIN|LOGIN_SETGROUP)) != 0) {
                syslog(LOG_ERR, "setusercontext() failed - exiting");
                exit(1);
        }

        (void)setenv("SHELL", pwd->pw_shell, 1);
        (void)setenv("HOME", pwd->pw_dir, 1);
        /* Overwrite "term" from login.conf(5) for any known TERM */
        if (term == NULL && (tp = stypeof(tty)) != NULL)
                (void)setenv("TERM", tp, 1);
        else
                (void)setenv("TERM", TERM_UNKNOWN, 0);
        (void)setenv("LOGNAME", username, 1);
        (void)setenv("USER", username, 1);
        (void)setenv("PATH", rootlogin ? _PATH_STDPATH : _PATH_DEFPATH, 0);

        if (!quietlog) {
                const char *cw;

                cw = login_getcapstr(lc, "welcome", NULL, NULL);
                if (cw != NULL && access(cw, F_OK) == 0)
                        motd(cw);
                else
                        motd(_PATH_MOTDFILE);

                if (login_getcapbool(lc_user, "nocheckmail", 0) == 0 &&
                    login_getcapbool(lc, "nocheckmail", 0) == 0) {
                        char *cx;

                        /* $MAIL may have been set by class. */
                        cx = getenv("MAIL");
                        if (cx == NULL) {
                                asprintf(&cx, "%s/%s",
                                    _PATH_MAILDIR, pwd->pw_name);
                        }
                        if (cx && stat(cx, &st) == 0 && st.st_size != 0)
                                (void)printf("You have %smail.\n",
                                    (st.st_mtime > st.st_atime) ? "new " : "");
                        if (getenv("MAIL") == NULL)
                                free(cx);
                }
        }

        login_close(lc_user);
        login_close(lc);

        sa.sa_handler = SIG_DFL;
        (void)sigaction(SIGALRM, &sa, NULL);
        (void)sigaction(SIGQUIT, &sa, NULL);
        (void)sigaction(SIGINT, &sa, NULL);
        (void)sigaction(SIGTERM, &sa, NULL);
        (void)sigaction(SIGHUP, &sa, NULL);
        sa.sa_handler = SIG_IGN;
        (void)sigaction(SIGTSTP, &sa, NULL);
        (void)sigprocmask(SIG_SETMASK, &omask, NULL);

        /*
         * Login shells have a leading '-' in front of argv[0]
         */
        p = strrchr(pwd->pw_shell, '/');
        if (asprintf(&arg0, "-%s", p ? p + 1 : pwd->pw_shell) >= MAXPATHLEN) {
                syslog(LOG_ERR, "user: %s: shell exceeds maximum pathname size",
                    username);
                errx(1, "shell exceeds maximum pathname size");
        } else if (arg0 == NULL) {
                err(1, "asprintf()");
        }

        execlp(shell, arg0, (char *)0);
        err(1, "%s", shell);

        /*
         * That's it, folks!
         */
}

/*
 * Attempt to authenticate the user using PAM.  Returns 0 if the user is
 * authenticated, or 1 if not authenticated.  If some sort of PAM system
 * error occurs (e.g., the "/etc/pam.conf" file is missing) then this
 * function returns -1.  This can be used as an indication that we should
 * fall back to a different authentication mechanism.
 */
static int
auth_pam(void)
{
        const char *tmpl_user;
        const void *item;
        int rval;

        pam_err = pam_authenticate(pamh, pam_silent);
        switch (pam_err) {

        case PAM_SUCCESS:
                /*
                 * With PAM we support the concept of a "template"
                 * user.  The user enters a login name which is
                 * authenticated by PAM, usually via a remote service
                 * such as RADIUS or TACACS+.  If authentication
                 * succeeds, a different but related "template" name
                 * is used for setting the credentials, shell, and
                 * home directory.  The name the user enters need only
                 * exist on the remote authentication server, but the
                 * template name must be present in the local password
                 * database.
                 *
                 * This is supported by two various mechanisms in the
                 * individual modules.  However, from the application's
                 * point of view, the template user is always passed
                 * back as a changed value of the PAM_USER item.
                 */
                pam_err = pam_get_item(pamh, PAM_USER, &item);
                if (pam_err == PAM_SUCCESS) {
                        tmpl_user = (const char *)item;
                        if (strcmp(username, tmpl_user) != 0) {
                                (void)getpwnam_r(tmpl_user, &pwres, pwbuf,
                                    sizeof(pwbuf), &pwd);
                        }
                } else {
                        pam_syslog("pam_get_item(PAM_USER)");
                }
                rval = 0;
                break;

        case PAM_AUTH_ERR:
        case PAM_USER_UNKNOWN:
        case PAM_MAXTRIES:
                rval = 1;
                break;

        default:
                pam_syslog("pam_authenticate()");
                rval = -1;
                break;
        }

        if (rval == 0) {
                pam_err = pam_acct_mgmt(pamh, pam_silent);
                switch (pam_err) {
                case PAM_SUCCESS:
                        break;
                case PAM_NEW_AUTHTOK_REQD:
                        pam_err = pam_chauthtok(pamh,
                            pam_silent|PAM_CHANGE_EXPIRED_AUTHTOK);
                        if (pam_err != PAM_SUCCESS) {
                                pam_syslog("pam_chauthtok()");
                                rval = 1;
                        }
                        break;
                default:
                        pam_syslog("pam_acct_mgmt()");
                        rval = 1;
                        break;
                }
        }

        if (rval != 0) {
                pam_end(pamh, pam_err);
                pamh = NULL;
        }
        return (rval);
}

/*
 * Export any environment variables PAM modules may have set
 */
static void
export_pam_environment(void)
{
        char **pam_env;
        char **pp;

        pam_env = pam_getenvlist(pamh);
        if (pam_env != NULL) {
                for (pp = pam_env; *pp != NULL; pp++) {
                        (void)export(*pp);
                        free(*pp);
                }
        }
}

/*
 * Perform sanity checks on an environment variable:
 * - Make sure there is an '=' in the string.
 * - Make sure the string doesn't run on too long.
 * - Do not export certain variables.  This list was taken from the
 *   Solaris pam_putenv(3) man page.
 * Then export it.
 */
static int
export(const char *s)
{
        static const char *noexport[] = {
                "SHELL", "HOME", "LOGNAME", "MAIL", "CDPATH",
                "IFS", "PATH", NULL
        };
        char *p;
        const char **pp;
        size_t n;
        int rv;

        if (strlen(s) > 1024 || (p = strchr(s, '=')) == NULL)
                return (0);
        if (strncmp(s, "LD_", 3) == 0)
                return (0);
        for (pp = noexport; *pp != NULL; pp++) {
                n = strlen(*pp);
                if (s[n] == '=' && strncmp(s, *pp, n) == 0)
                        return (0);
        }
        *p = '\0';
        rv = setenv(s, p + 1, 1);
        *p = '=';
        if (rv == -1)
                return (0);
        return (1);
}

static void
usage(void)
{

        (void)fprintf(stderr, "usage: login [-fp] [-h hostname] [username]\n");
        exit(1);
}

/*
 * Prompt user and read login name from stdin.
 */
static char *
getloginname(void)
{
        char *nbuf, *p;
        int ch;

        nbuf = malloc(MAXLOGNAME);
        if (nbuf == NULL)
                err(1, "malloc()");
        do {
                (void)printf("%s", prompt);
                for (p = nbuf; (ch = getchar()) != '\n'; ) {
                        if (ch == EOF) {
                                badlogin(username);
                                bail(NO_SLEEP_EXIT, 0);
                        }
                        if (p < nbuf + MAXLOGNAME - 1)
                                *p++ = ch;
                }
        } while (p == nbuf);

        *p = '\0';
        if (nbuf[0] == '-') {
                pam_silent = 0;
                memmove(nbuf, nbuf + 1, strlen(nbuf));
        } else {
                pam_silent = PAM_SILENT;
        }
        return nbuf;
}

/*
 * SIGINT handler for motd().
 */
static volatile int motdinterrupt;
static void
sigint(int signo __unused)
{
        motdinterrupt = 1;
}

/*
 * Display the contents of a file (such as /etc/motd).
 */
static int
motd(const char *motdfile)
{
        struct sigaction newint, oldint;
        FILE *f;
        int ch;

        if ((f = fopen(motdfile, "r")) == NULL)
                return (-1);
        motdinterrupt = 0;
        newint.sa_handler = sigint;
        newint.sa_flags = 0;
        sigfillset(&newint.sa_mask);
        sigaction(SIGINT, &newint, &oldint);
        while ((ch = fgetc(f)) != EOF && !motdinterrupt)
                putchar(ch);
        sigaction(SIGINT, &oldint, NULL);
        if (ch != EOF || ferror(f)) {
                fclose(f);
                return (-1);
        }
        fclose(f);
        return (0);
}

/*
 * SIGALRM handler, to enforce login prompt timeout.
 *
 * XXX This can potentially confuse the hell out of PAM.  We should
 * XXX instead implement a conversation function that returns
 * XXX PAM_CONV_ERR when interrupted by a signal, and have the signal
 * XXX handler just set a flag.
 */
static void
timedout(int signo __unused)
{

        longjmp(timeout_buf, signo);
}

static void
badlogin(char *name)
{

        if (failures == 0)
                return;
        if (hflag) {
                syslog(LOG_NOTICE, "%d LOGIN FAILURE%s FROM %s",
                    failures, failures > 1 ? "S" : "", hostname);
                syslog(LOG_AUTHPRIV|LOG_NOTICE,
                    "%d LOGIN FAILURE%s FROM %s, %s",
                    failures, failures > 1 ? "S" : "", hostname, name);
        } else {
                syslog(LOG_NOTICE, "%d LOGIN FAILURE%s ON %s",
                    failures, failures > 1 ? "S" : "", tty);
                syslog(LOG_AUTHPRIV|LOG_NOTICE,
                    "%d LOGIN FAILURE%s ON %s, %s",
                    failures, failures > 1 ? "S" : "", tty, name);
        }
        failures = 0;
}

const char *
stypeof(char *ttyid)
{
        struct ttyent *t;

        if (ttyid != NULL && *ttyid != '\0') {
                t = getttynam(ttyid);
                if (t != NULL && t->ty_type != NULL)
                        return (t->ty_type);
        }
        return (NULL);
}

static void
refused(const char *msg, const char *rtype, int lout)
{

        if (msg != NULL)
            printf("%s.\n", msg);
        if (hflag)
                syslog(LOG_NOTICE, "LOGIN %s REFUSED (%s) FROM %s ON TTY %s",
                    pwd->pw_name, rtype, hostname, tty);
        else
                syslog(LOG_NOTICE, "LOGIN %s REFUSED (%s) ON TTY %s",
                    pwd->pw_name, rtype, tty);
        if (lout)
                bail(SLEEP_EXIT, 1);
}

/*
 * Log a PAM error
 */
static void
pam_syslog(const char *msg)
{
        syslog(LOG_ERR, "%s: %s", msg, pam_strerror(pamh, pam_err));
}

/*
 * Shut down PAM
 */
static void
pam_cleanup(void)
{

        if (pamh != NULL) {
                if (pam_session_established) {
                        pam_err = pam_close_session(pamh, 0);
                        if (pam_err != PAM_SUCCESS)
                                pam_syslog("pam_close_session()");
                }
                pam_session_established = 0;
                if (pam_cred_established) {
                        pam_err = pam_setcred(pamh, pam_silent|PAM_DELETE_CRED);
                        if (pam_err != PAM_SUCCESS)
                                pam_syslog("pam_setcred()");
                }
                pam_cred_established = 0;
                pam_end(pamh, pam_err);
                pamh = NULL;
        }
}

static void
bail_internal(int sec, int eval, int signo)
{
        struct sigaction sa;

        pam_cleanup();
#ifdef USE_BSM_AUDIT
        if (pwd != NULL)
                audit_logout();
#endif
        (void)sleep(sec);
        if (signo == 0)
                exit(eval);
        else {
                sa.sa_handler = SIG_DFL;
                sa.sa_flags = 0;
                (void)sigemptyset(&sa.sa_mask);
                (void)sigaction(signo, &sa, NULL);
                (void)sigaddset(&sa.sa_mask, signo);
                (void)sigprocmask(SIG_UNBLOCK, &sa.sa_mask, NULL);
                raise(signo);
                exit(128 + signo);
        }
}

/*
 * Exit, optionally after sleeping a few seconds
 */
static void
bail(int sec, int eval)
{
        bail_internal(sec, eval, 0);
}

/*
 * Exit because of a signal.
 * This is not async-signal safe, so only call async-signal safe functions
 * while the signal is unmasked.
 */
static void
bail_sig(int signo)
{
        bail_internal(NO_SLEEP_EXIT, 0, signo);
}