Annotation of embedaddon/sudo/plugins/sudoers/check.c, revision 1.1.1.1

1.1       misho       1: /*
                      2:  * Copyright (c) 1993-1996,1998-2005, 2007-2011
                      3:  *     Todd C. Miller <Todd.Miller@courtesan.com>
                      4:  *
                      5:  * Permission to use, copy, modify, and distribute this software for any
                      6:  * purpose with or without fee is hereby granted, provided that the above
                      7:  * copyright notice and this permission notice appear in all copies.
                      8:  *
                      9:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
                     10:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
                     11:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
                     12:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
                     13:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
                     14:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
                     15:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
                     16:  *
                     17:  * Sponsored in part by the Defense Advanced Research Projects
                     18:  * Agency (DARPA) and Air Force Research Laboratory, Air Force
                     19:  * Materiel Command, USAF, under agreement number F39502-99-1-0512.
                     20:  */
                     21: 
                     22: #include <config.h>
                     23: 
                     24: #include <sys/types.h>
                     25: #include <sys/param.h>
                     26: #include <sys/time.h>
                     27: #include <sys/stat.h>
                     28: #ifdef __linux__
                     29: # include <sys/vfs.h>
                     30: #endif
                     31: #if defined(__sun) && defined(__SVR4)
                     32: # include <sys/statvfs.h>
                     33: #endif
                     34: #ifndef __TANDEM
                     35: # include <sys/file.h>
                     36: #endif
                     37: #include <stdio.h>
                     38: #ifdef STDC_HEADERS
                     39: # include <stdlib.h>
                     40: # include <stddef.h>
                     41: #else
                     42: # ifdef HAVE_STDLIB_H
                     43: #  include <stdlib.h>
                     44: # endif
                     45: #endif /* STDC_HEADERS */
                     46: #ifdef HAVE_STRING_H
                     47: # include <string.h>
                     48: #endif /* HAVE_STRING_H */
                     49: #ifdef HAVE_STRINGS_H
                     50: # include <strings.h>
                     51: #endif /* HAVE_STRINGS_H */
                     52: #ifdef HAVE_UNISTD_H
                     53: # include <unistd.h>
                     54: #endif /* HAVE_UNISTD_H */
                     55: #if TIME_WITH_SYS_TIME
                     56: # include <time.h>
                     57: #endif
                     58: #include <errno.h>
                     59: #include <fcntl.h>
                     60: #include <signal.h>
                     61: #include <pwd.h>
                     62: #include <grp.h>
                     63: 
                     64: #include "sudoers.h"
                     65: 
                     66: /* Status codes for timestamp_status() */
                     67: #define TS_CURRENT             0
                     68: #define TS_OLD                 1
                     69: #define TS_MISSING             2
                     70: #define TS_NOFILE              3
                     71: #define TS_ERROR               4
                     72: 
                     73: /* Flags for timestamp_status() */
                     74: #define TS_MAKE_DIRS           1
                     75: #define TS_REMOVE              2
                     76: 
                     77: /*
                     78:  * Info stored in tty ticket from stat(2) to help with tty matching.
                     79:  */
                     80: static struct tty_info {
                     81:     dev_t dev;                 /* ID of device tty resides on */
                     82:     dev_t rdev;                        /* tty device ID */
                     83:     ino_t ino;                 /* tty inode number */
                     84:     struct timeval ctime;      /* tty inode change time */
                     85: } tty_info;
                     86: 
                     87: static int   build_timestamp(char **, char **);
                     88: static int   timestamp_status(char *, char *, char *, int);
                     89: static char *expand_prompt(char *, char *, char *);
                     90: static void  lecture(int);
                     91: static void  update_timestamp(char *, char *);
                     92: static int   tty_is_devpts(const char *);
                     93: static struct passwd *get_authpw(void);
                     94: 
                     95: /*
                     96:  * Returns TRUE if the user successfully authenticates, else FALSE.
                     97:  */
                     98: int
                     99: check_user(int validated, int mode)
                    100: {
                    101:     struct passwd *auth_pw;
                    102:     char *timestampdir = NULL;
                    103:     char *timestampfile = NULL;
                    104:     char *prompt;
                    105:     struct stat sb;
                    106:     int status, rval = TRUE;
                    107:     int need_pass = def_authenticate;
                    108: 
                    109:     /*
                    110:      * Init authentication system regardless of whether we need a password.
                    111:      * Required for proper PAM session support.
                    112:      */
                    113:     auth_pw = get_authpw();
                    114:     if (sudo_auth_init(auth_pw) == -1) {
                    115:        rval = -1;
                    116:        goto done;
                    117:     }
                    118: 
                    119:     if (need_pass) {
                    120:        /* Always need a password when -k was specified with the command. */
                    121:        if (ISSET(mode, MODE_IGNORE_TICKET)) {
                    122:            SET(validated, FLAG_CHECK_USER);
                    123:        } else {
                    124:            /*
                    125:             * Don't prompt for the root passwd or if the user is exempt.
                    126:             * If the user is not changing uid/gid, no need for a password.
                    127:             */
                    128:            if (user_uid == 0 || (user_uid == runas_pw->pw_uid &&
                    129:                (!runas_gr || user_in_group(sudo_user.pw, runas_gr->gr_name)))
                    130:                || user_is_exempt())
                    131:                need_pass = FALSE;
                    132:        }
                    133:     }
                    134:     if (!need_pass)
                    135:        goto done;
                    136: 
                    137:     /* Stash the tty's ctime for tty ticket comparison. */
                    138:     if (def_tty_tickets && user_ttypath && stat(user_ttypath, &sb) == 0) {
                    139:        tty_info.dev = sb.st_dev;
                    140:        tty_info.ino = sb.st_ino;
                    141:        tty_info.rdev = sb.st_rdev;
                    142:        if (tty_is_devpts(user_ttypath))
                    143:            ctim_get(&sb, &tty_info.ctime);
                    144:     }
                    145: 
                    146:     if (build_timestamp(&timestampdir, &timestampfile) == -1) {
                    147:        rval = -1;
                    148:        goto done;
                    149:     }
                    150: 
                    151:     status = timestamp_status(timestampdir, timestampfile, user_name,
                    152:        TS_MAKE_DIRS);
                    153: 
                    154:     if (status != TS_CURRENT || ISSET(validated, FLAG_CHECK_USER)) {
                    155:        /* Bail out if we are non-interactive and a password is required */
                    156:        if (ISSET(mode, MODE_NONINTERACTIVE)) {
                    157:            warningx(_("sorry, a password is required to run %s"), getprogname());
                    158:            rval = -1;
                    159:            goto done;
                    160:        }
                    161: 
                    162:        /* XXX - should not lecture if askpass helper is being used. */
                    163:        lecture(status);
                    164: 
                    165:        /* Expand any escapes in the prompt. */
                    166:        prompt = expand_prompt(user_prompt ? user_prompt : def_passprompt,
                    167:            user_name, user_shost);
                    168: 
                    169:        rval = verify_user(auth_pw, prompt);
                    170:     }
                    171:     /* Only update timestamp if user was validated. */
                    172:     if (rval == TRUE && ISSET(validated, VALIDATE_OK) &&
                    173:        !ISSET(mode, MODE_IGNORE_TICKET) && status != TS_ERROR)
                    174:        update_timestamp(timestampdir, timestampfile);
                    175:     efree(timestampdir);
                    176:     efree(timestampfile);
                    177: 
                    178: done:
                    179:     sudo_auth_cleanup(auth_pw);
                    180:     pw_delref(auth_pw);
                    181: 
                    182:     return rval;
                    183: }
                    184: 
                    185: #define DEFAULT_LECTURE "\n" \
                    186:     "We trust you have received the usual lecture from the local System\n" \
                    187:     "Administrator. It usually boils down to these three things:\n\n" \
                    188:     "    #1) Respect the privacy of others.\n" \
                    189:     "    #2) Think before you type.\n" \
                    190:     "    #3) With great power comes great responsibility.\n\n"
                    191: 
                    192: /*
                    193:  * Standard sudo lecture.
                    194:  */
                    195: static void
                    196: lecture(int status)
                    197: {
                    198:     FILE *fp;
                    199:     char buf[BUFSIZ];
                    200:     ssize_t nread;
                    201:     struct sudo_conv_message msg;
                    202:     struct sudo_conv_reply repl;
                    203: 
                    204:     if (def_lecture == never ||
                    205:        (def_lecture == once && status != TS_MISSING && status != TS_ERROR))
                    206:        return;
                    207: 
                    208:     memset(&msg, 0, sizeof(msg));
                    209:     memset(&repl, 0, sizeof(repl));
                    210: 
                    211:     if (def_lecture_file && (fp = fopen(def_lecture_file, "r")) != NULL) {
                    212:        while ((nread = fread(buf, sizeof(char), sizeof(buf) - 1, fp)) != 0) {
                    213:            buf[sizeof(buf) - 1] = '\0';
                    214:            msg.msg_type = SUDO_CONV_ERROR_MSG;
                    215:            msg.msg = buf;
                    216:            sudo_conv(1, &msg, &repl);
                    217:        }
                    218:        fclose(fp);
                    219:     } else {
                    220:        msg.msg_type = SUDO_CONV_ERROR_MSG;
                    221:        msg.msg = _(DEFAULT_LECTURE);
                    222:        sudo_conv(1, &msg, &repl);
                    223:     }
                    224: }
                    225: 
                    226: /*
                    227:  * Update the time on the timestamp file/dir or create it if necessary.
                    228:  */
                    229: static void
                    230: update_timestamp(char *timestampdir, char *timestampfile)
                    231: {
                    232:     /* If using tty timestamps but we have no tty there is nothing to do. */
                    233:     if (def_tty_tickets && !user_ttypath)
                    234:        return;
                    235: 
                    236:     if (timestamp_uid != 0)
                    237:        set_perms(PERM_TIMESTAMP);
                    238:     if (timestampfile) {
                    239:        /*
                    240:         * Store tty info in timestamp file
                    241:         */
                    242:        int fd = open(timestampfile, O_WRONLY|O_CREAT, 0600);
                    243:        if (fd == -1)
                    244:            log_error(NO_EXIT|USE_ERRNO, _("unable to open %s"), timestampfile);
                    245:        else {
                    246:            lock_file(fd, SUDO_LOCK);
                    247:            if (write(fd, &tty_info, sizeof(tty_info)) != sizeof(tty_info)) {
                    248:                log_error(NO_EXIT|USE_ERRNO, _("unable to write to %s"),
                    249:                    timestampfile);
                    250:            }
                    251:            close(fd);
                    252:        }
                    253:     } else {
                    254:        if (touch(-1, timestampdir, NULL) == -1) {
                    255:            if (mkdir(timestampdir, 0700) == -1) {
                    256:                log_error(NO_EXIT|USE_ERRNO, _("unable to mkdir %s"),
                    257:                    timestampdir);
                    258:            }
                    259:        }
                    260:     }
                    261:     if (timestamp_uid != 0)
                    262:        restore_perms();
                    263: }
                    264: 
                    265: /*
                    266:  * Expand %h and %u escapes in the prompt and pass back the dynamically
                    267:  * allocated result.  Returns the same string if there are no escapes.
                    268:  */
                    269: static char *
                    270: expand_prompt(char *old_prompt, char *user, char *host)
                    271: {
                    272:     size_t len, n;
                    273:     int subst;
                    274:     char *p, *np, *new_prompt, *endp;
                    275: 
                    276:     /* How much space do we need to malloc for the prompt? */
                    277:     subst = 0;
                    278:     for (p = old_prompt, len = strlen(old_prompt); *p; p++) {
                    279:        if (p[0] =='%') {
                    280:            switch (p[1]) {
                    281:                case 'h':
                    282:                    p++;
                    283:                    len += strlen(user_shost) - 2;
                    284:                    subst = 1;
                    285:                    break;
                    286:                case 'H':
                    287:                    p++;
                    288:                    len += strlen(user_host) - 2;
                    289:                    subst = 1;
                    290:                    break;
                    291:                case 'p':
                    292:                    p++;
                    293:                    if (def_rootpw)
                    294:                            len += 2;
                    295:                    else if (def_targetpw || def_runaspw)
                    296:                            len += strlen(runas_pw->pw_name) - 2;
                    297:                    else
                    298:                            len += strlen(user_name) - 2;
                    299:                    subst = 1;
                    300:                    break;
                    301:                case 'u':
                    302:                    p++;
                    303:                    len += strlen(user_name) - 2;
                    304:                    subst = 1;
                    305:                    break;
                    306:                case 'U':
                    307:                    p++;
                    308:                    len += strlen(runas_pw->pw_name) - 2;
                    309:                    subst = 1;
                    310:                    break;
                    311:                case '%':
                    312:                    p++;
                    313:                    len--;
                    314:                    subst = 1;
                    315:                    break;
                    316:                default:
                    317:                    break;
                    318:            }
                    319:        }
                    320:     }
                    321: 
                    322:     if (subst) {
                    323:        new_prompt = emalloc(++len);
                    324:        endp = new_prompt + len;
                    325:        for (p = old_prompt, np = new_prompt; *p; p++) {
                    326:            if (p[0] =='%') {
                    327:                switch (p[1]) {
                    328:                    case 'h':
                    329:                        p++;
                    330:                        n = strlcpy(np, user_shost, np - endp);
                    331:                        if (n >= np - endp)
                    332:                            goto oflow;
                    333:                        np += n;
                    334:                        continue;
                    335:                    case 'H':
                    336:                        p++;
                    337:                        n = strlcpy(np, user_host, np - endp);
                    338:                        if (n >= np - endp)
                    339:                            goto oflow;
                    340:                        np += n;
                    341:                        continue;
                    342:                    case 'p':
                    343:                        p++;
                    344:                        if (def_rootpw)
                    345:                                n = strlcpy(np, "root", np - endp);
                    346:                        else if (def_targetpw || def_runaspw)
                    347:                                n = strlcpy(np, runas_pw->pw_name, np - endp);
                    348:                        else
                    349:                                n = strlcpy(np, user_name, np - endp);
                    350:                        if (n >= np - endp)
                    351:                                goto oflow;
                    352:                        np += n;
                    353:                        continue;
                    354:                    case 'u':
                    355:                        p++;
                    356:                        n = strlcpy(np, user_name, np - endp);
                    357:                        if (n >= np - endp)
                    358:                            goto oflow;
                    359:                        np += n;
                    360:                        continue;
                    361:                    case 'U':
                    362:                        p++;
                    363:                        n = strlcpy(np,  runas_pw->pw_name, np - endp);
                    364:                        if (n >= np - endp)
                    365:                            goto oflow;
                    366:                        np += n;
                    367:                        continue;
                    368:                    case '%':
                    369:                        /* convert %% -> % */
                    370:                        p++;
                    371:                        break;
                    372:                    default:
                    373:                        /* no conversion */
                    374:                        break;
                    375:                }
                    376:            }
                    377:            *np++ = *p;
                    378:            if (np >= endp)
                    379:                goto oflow;
                    380:        }
                    381:        *np = '\0';
                    382:     } else
                    383:        new_prompt = old_prompt;
                    384: 
                    385:     return new_prompt;
                    386: 
                    387: oflow:
                    388:     /* We pre-allocate enough space, so this should never happen. */
                    389:     errorx(1, _("internal error, expand_prompt() overflow"));
                    390: }
                    391: 
                    392: /*
                    393:  * Checks if the user is exempt from supplying a password.
                    394:  */
                    395: int
                    396: user_is_exempt(void)
                    397: {
                    398:     if (!def_exempt_group)
                    399:        return FALSE;
                    400:     return user_in_group(sudo_user.pw, def_exempt_group);
                    401: }
                    402: 
                    403: /*
                    404:  * Fills in timestampdir as well as timestampfile if using tty tickets.
                    405:  */
                    406: static int
                    407: build_timestamp(char **timestampdir, char **timestampfile)
                    408: {
                    409:     char *dirparent;
                    410:     int len;
                    411: 
                    412:     dirparent = def_timestampdir;
                    413:     len = easprintf(timestampdir, "%s/%s", dirparent, user_name);
                    414:     if (len >= PATH_MAX)
                    415:        goto bad;
                    416: 
                    417:     /*
                    418:      * Timestamp file may be a file in the directory or NUL to use
                    419:      * the directory as the timestamp.
                    420:      */
                    421:     if (def_tty_tickets) {
                    422:        char *p;
                    423: 
                    424:        if ((p = strrchr(user_tty, '/')))
                    425:            p++;
                    426:        else
                    427:            p = user_tty;
                    428:        if (def_targetpw)
                    429:            len = easprintf(timestampfile, "%s/%s/%s:%s", dirparent, user_name,
                    430:                p, runas_pw->pw_name);
                    431:        else
                    432:            len = easprintf(timestampfile, "%s/%s/%s", dirparent, user_name, p);
                    433:        if (len >= PATH_MAX)
                    434:            goto bad;
                    435:     } else if (def_targetpw) {
                    436:        len = easprintf(timestampfile, "%s/%s/%s", dirparent, user_name,
                    437:            runas_pw->pw_name);
                    438:        if (len >= PATH_MAX)
                    439:            goto bad;
                    440:     } else
                    441:        *timestampfile = NULL;
                    442: 
                    443:     return len;
                    444: bad:
                    445:     log_error(0, _("timestamp path too long: %s"), *timestampfile);
                    446:     return -1;
                    447: }
                    448: 
                    449: /*
                    450:  * Check the timestamp file and directory and return their status.
                    451:  */
                    452: static int
                    453: timestamp_status(char *timestampdir, char *timestampfile, char *user, int flags)
                    454: {
                    455:     struct stat sb;
                    456:     struct timeval boottime, mtime;
                    457:     time_t now;
                    458:     char *dirparent = def_timestampdir;
                    459:     int status = TS_ERROR;             /* assume the worst */
                    460: 
                    461:     if (timestamp_uid != 0)
                    462:        set_perms(PERM_TIMESTAMP);
                    463: 
                    464:     /*
                    465:      * Sanity check dirparent and make it if it doesn't already exist.
                    466:      * We start out assuming the worst (that the dir is not sane) and
                    467:      * if it is ok upgrade the status to ``no timestamp file''.
                    468:      * Note that we don't check the parent(s) of dirparent for
                    469:      * sanity since the sudo dir is often just located in /tmp.
                    470:      */
                    471:     if (lstat(dirparent, &sb) == 0) {
                    472:        if (!S_ISDIR(sb.st_mode))
                    473:            log_error(NO_EXIT, _("%s exists but is not a directory (0%o)"),
                    474:                dirparent, (unsigned int) sb.st_mode);
                    475:        else if (sb.st_uid != timestamp_uid)
                    476:            log_error(NO_EXIT, _("%s owned by uid %u, should be uid %u"),
                    477:                dirparent, (unsigned int) sb.st_uid,
                    478:                (unsigned int) timestamp_uid);
                    479:        else if ((sb.st_mode & 0000022))
                    480:            log_error(NO_EXIT,
                    481:                _("%s writable by non-owner (0%o), should be mode 0700"),
                    482:                dirparent, (unsigned int) sb.st_mode);
                    483:        else {
                    484:            if ((sb.st_mode & 0000777) != 0700)
                    485:                (void) chmod(dirparent, 0700);
                    486:            status = TS_MISSING;
                    487:        }
                    488:     } else if (errno != ENOENT) {
                    489:        log_error(NO_EXIT|USE_ERRNO, _("unable to stat %s"), dirparent);
                    490:     } else {
                    491:        /* No dirparent, try to make one. */
                    492:        if (ISSET(flags, TS_MAKE_DIRS)) {
                    493:            if (mkdir(dirparent, S_IRWXU))
                    494:                log_error(NO_EXIT|USE_ERRNO, _("unable to mkdir %s"),
                    495:                    dirparent);
                    496:            else
                    497:                status = TS_MISSING;
                    498:        }
                    499:     }
                    500:     if (status == TS_ERROR)
                    501:        goto done;
                    502: 
                    503:     /*
                    504:      * Sanity check the user's ticket dir.  We start by downgrading
                    505:      * the status to TS_ERROR.  If the ticket dir exists and is sane
                    506:      * this will be upgraded to TS_OLD.  If the dir does not exist,
                    507:      * it will be upgraded to TS_MISSING.
                    508:      */
                    509:     status = TS_ERROR;                 /* downgrade status again */
                    510:     if (lstat(timestampdir, &sb) == 0) {
                    511:        if (!S_ISDIR(sb.st_mode)) {
                    512:            if (S_ISREG(sb.st_mode)) {
                    513:                /* convert from old style */
                    514:                if (unlink(timestampdir) == 0)
                    515:                    status = TS_MISSING;
                    516:            } else
                    517:                log_error(NO_EXIT, _("%s exists but is not a directory (0%o)"),
                    518:                    timestampdir, (unsigned int) sb.st_mode);
                    519:        } else if (sb.st_uid != timestamp_uid)
                    520:            log_error(NO_EXIT, _("%s owned by uid %u, should be uid %u"),
                    521:                timestampdir, (unsigned int) sb.st_uid,
                    522:                (unsigned int) timestamp_uid);
                    523:        else if ((sb.st_mode & 0000022))
                    524:            log_error(NO_EXIT,
                    525:                _("%s writable by non-owner (0%o), should be mode 0700"),
                    526:                timestampdir, (unsigned int) sb.st_mode);
                    527:        else {
                    528:            if ((sb.st_mode & 0000777) != 0700)
                    529:                (void) chmod(timestampdir, 0700);
                    530:            status = TS_OLD;            /* do date check later */
                    531:        }
                    532:     } else if (errno != ENOENT) {
                    533:        log_error(NO_EXIT|USE_ERRNO, _("unable to stat %s"), timestampdir);
                    534:     } else
                    535:        status = TS_MISSING;
                    536: 
                    537:     /*
                    538:      * If there is no user ticket dir, AND we are in tty ticket mode,
                    539:      * AND the TS_MAKE_DIRS flag is set, create the user ticket dir.
                    540:      */
                    541:     if (status == TS_MISSING && timestampfile && ISSET(flags, TS_MAKE_DIRS)) {
                    542:        if (mkdir(timestampdir, S_IRWXU) == -1) {
                    543:            status = TS_ERROR;
                    544:            log_error(NO_EXIT|USE_ERRNO, _("unable to mkdir %s"), timestampdir);
                    545:        }
                    546:     }
                    547: 
                    548:     /*
                    549:      * Sanity check the tty ticket file if it exists.
                    550:      */
                    551:     if (timestampfile && status != TS_ERROR) {
                    552:        if (status != TS_MISSING)
                    553:            status = TS_NOFILE;                 /* dir there, file missing */
                    554:        if (def_tty_tickets && !user_ttypath)
                    555:            goto done;                          /* no tty, always prompt */
                    556:        if (lstat(timestampfile, &sb) == 0) {
                    557:            if (!S_ISREG(sb.st_mode)) {
                    558:                status = TS_ERROR;
                    559:                log_error(NO_EXIT, _("%s exists but is not a regular file (0%o)"),
                    560:                    timestampfile, (unsigned int) sb.st_mode);
                    561:            } else {
                    562:                /* If bad uid or file mode, complain and kill the bogus file. */
                    563:                if (sb.st_uid != timestamp_uid) {
                    564:                    log_error(NO_EXIT,
                    565:                        _("%s owned by uid %u, should be uid %u"),
                    566:                        timestampfile, (unsigned int) sb.st_uid,
                    567:                        (unsigned int) timestamp_uid);
                    568:                    (void) unlink(timestampfile);
                    569:                } else if ((sb.st_mode & 0000022)) {
                    570:                    log_error(NO_EXIT,
                    571:                        _("%s writable by non-owner (0%o), should be mode 0600"),
                    572:                        timestampfile, (unsigned int) sb.st_mode);
                    573:                    (void) unlink(timestampfile);
                    574:                } else {
                    575:                    /* If not mode 0600, fix it. */
                    576:                    if ((sb.st_mode & 0000777) != 0600)
                    577:                        (void) chmod(timestampfile, 0600);
                    578: 
                    579:                    /*
                    580:                     * Check for stored tty info.  If the file is zero-sized
                    581:                     * it is an old-style timestamp with no tty info in it.
                    582:                     * If removing, we don't care about the contents.
                    583:                     * The actual mtime check is done later.
                    584:                     */
                    585:                    if (ISSET(flags, TS_REMOVE)) {
                    586:                        status = TS_OLD;
                    587:                    } else if (sb.st_size != 0) {
                    588:                        struct tty_info info;
                    589:                        int fd = open(timestampfile, O_RDONLY, 0644);
                    590:                        if (fd != -1) {
                    591:                            if (read(fd, &info, sizeof(info)) == sizeof(info) &&
                    592:                                memcmp(&info, &tty_info, sizeof(info)) == 0) {
                    593:                                status = TS_OLD;
                    594:                            }
                    595:                            close(fd);
                    596:                        }
                    597:                    }
                    598:                }
                    599:            }
                    600:        } else if (errno != ENOENT) {
                    601:            log_error(NO_EXIT|USE_ERRNO, _("unable to stat %s"), timestampfile);
                    602:            status = TS_ERROR;
                    603:        }
                    604:     }
                    605: 
                    606:     /*
                    607:      * If the file/dir exists and we are not removing it, check its mtime.
                    608:      */
                    609:     if (status == TS_OLD && !ISSET(flags, TS_REMOVE)) {
                    610:        mtim_get(&sb, &mtime);
                    611:        /* Negative timeouts only expire manually (sudo -k). */
                    612:        if (def_timestamp_timeout < 0 && mtime.tv_sec != 0)
                    613:            status = TS_CURRENT;
                    614:        else {
                    615:            now = time(NULL);
                    616:            if (def_timestamp_timeout &&
                    617:                now - mtime.tv_sec < 60 * def_timestamp_timeout) {
                    618:                /*
                    619:                 * Check for bogus time on the stampfile.  The clock may
                    620:                 * have been set back or someone could be trying to spoof us.
                    621:                 */
                    622:                if (mtime.tv_sec > now + 60 * def_timestamp_timeout * 2) {
                    623:                    time_t tv_sec = (time_t)mtime.tv_sec;
                    624:                    log_error(NO_EXIT,
                    625:                        _("timestamp too far in the future: %20.20s"),
                    626:                        4 + ctime(&tv_sec));
                    627:                    if (timestampfile)
                    628:                        (void) unlink(timestampfile);
                    629:                    else
                    630:                        (void) rmdir(timestampdir);
                    631:                    status = TS_MISSING;
                    632:                } else if (get_boottime(&boottime) && timevalcmp(&mtime, &boottime, <)) {
                    633:                    status = TS_OLD;
                    634:                } else {
                    635:                    status = TS_CURRENT;
                    636:                }
                    637:            }
                    638:        }
                    639:     }
                    640: 
                    641: done:
                    642:     if (timestamp_uid != 0)
                    643:        restore_perms();
                    644:     return status;
                    645: }
                    646: 
                    647: /*
                    648:  * Remove the timestamp ticket file/dir.
                    649:  */
                    650: void
                    651: remove_timestamp(int remove)
                    652: {
                    653:     struct timeval tv;
                    654:     char *timestampdir, *timestampfile, *path;
                    655:     int status;
                    656: 
                    657:     if (build_timestamp(&timestampdir, &timestampfile) == -1)
                    658:        return;
                    659: 
                    660:     status = timestamp_status(timestampdir, timestampfile, user_name,
                    661:        TS_REMOVE);
                    662:     if (status != TS_MISSING && status != TS_ERROR) {
                    663:        path = timestampfile ? timestampfile : timestampdir;
                    664:        if (remove) {
                    665:            if (timestampfile)
                    666:                status = unlink(timestampfile);
                    667:            else
                    668:                status = rmdir(timestampdir);
                    669:            if (status == -1 && errno != ENOENT) {
                    670:                log_error(NO_EXIT,
                    671:                    _("unable to remove %s (%s), will reset to the epoch"),
                    672:                    path, strerror(errno));
                    673:                remove = FALSE;
                    674:            }
                    675:        }
                    676:        if (!remove) {
                    677:            timevalclear(&tv);
                    678:            if (touch(-1, path, &tv) == -1 && errno != ENOENT)
                    679:                error(1, _("unable to reset %s to the epoch"), path);
                    680:        }
                    681:     }
                    682: 
                    683:     efree(timestampdir);
                    684:     efree(timestampfile);
                    685: }
                    686: 
                    687: /*
                    688:  * Returns TRUE if tty lives on a devpts or /devices filesystem, else FALSE.
                    689:  * Unlike most filesystems, the ctime of devpts nodes is not updated when
                    690:  * the device node is written to, only when the inode's status changes,
                    691:  * typically via the chmod, chown, link, rename, or utimes system calls.
                    692:  * Since the ctime is "stable" in this case, we can stash it the tty ticket
                    693:  * file and use it to determine whether the tty ticket file is stale.
                    694:  */
                    695: static int
                    696: tty_is_devpts(const char *tty)
                    697: {
                    698:     int retval = FALSE;
                    699: #ifdef __linux__
                    700:     struct statfs sfs;
                    701: 
                    702: #ifndef DEVPTS_SUPER_MAGIC
                    703: # define DEVPTS_SUPER_MAGIC 0x1cd1
                    704: #endif
                    705: 
                    706:     if (statfs(tty, &sfs) == 0) {
                    707:        if (sfs.f_type == DEVPTS_SUPER_MAGIC)
                    708:            retval = TRUE;
                    709:     }
                    710: #elif defined(__sun) && defined(__SVR4)
                    711:     struct statvfs sfs;
                    712: 
                    713:     if (statvfs(tty, &sfs) == 0) {
                    714:        if (strcmp(sfs.f_fstr, "devices") == 0)
                    715:            retval = TRUE;
                    716:     }
                    717: #endif /* __linux__ */
                    718:     return retval;
                    719: }
                    720: 
                    721: /*
                    722:  * Get passwd entry for the user we are going to authenticate as.
                    723:  * By default, this is the user invoking sudo.  In the most common
                    724:  * case, this matches sudo_user.pw or runas_pw.
                    725:  */
                    726: static struct passwd *
                    727: get_authpw(void)
                    728: {
                    729:     struct passwd *pw;
                    730: 
                    731:     if (def_rootpw) {
                    732:        if ((pw = sudo_getpwuid(ROOT_UID)) == NULL)
                    733:            log_error(0, _("unknown uid: %u"), ROOT_UID);
                    734:     } else if (def_runaspw) {
                    735:        if ((pw = sudo_getpwnam(def_runas_default)) == NULL)
                    736:            log_error(0, _("unknown user: %s"), def_runas_default);
                    737:     } else if (def_targetpw) {
                    738:        if (runas_pw->pw_name == NULL)
                    739:            log_error(NO_MAIL|MSG_ONLY, _("unknown uid: %u"),
                    740:                (unsigned int) runas_pw->pw_uid);
                    741:        pw_addref(runas_pw);
                    742:        pw = runas_pw;
                    743:     } else {
                    744:        pw_addref(sudo_user.pw);
                    745:        pw = sudo_user.pw;
                    746:     }
                    747: 
                    748:     return pw;
                    749: }

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