support/suexec.c

   1 /* Licensed to the Apache Software Foundation (ASF) under one or more
   2  * contributor license agreements.  See the NOTICE file distributed with
   3  * this work for additional information regarding copyright ownership.
   4  * The ASF licenses this file to You under the Apache License, Version 2.0
   5  * (the "License"); you may not use this file except in compliance with
   6  * the License.  You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 /*
  18  * suexec.c -- "Wrapper" support program for suEXEC behaviour for Apache
  19  *
  20  ***********************************************************************
  21  *
  22  * NOTE! : DO NOT edit this code!!!  Unless you know what you are doing,
  23  *         editing this code might open up your system in unexpected
  24  *         ways to would-be crackers.  Every precaution has been taken
  25  *         to make this code as safe as possible; alter it at your own
  26  *         risk.
  27  *
  28  ***********************************************************************
  29  *
  30  *
  31  */
  32
  33 #include "apr.h"
  34 #include "ap_config.h"
  35 #include "suexec.h"
  36
  37 #include <sys/param.h>
  38 #include <sys/stat.h>
  39 #include <sys/types.h>
  40 #include <string.h>
  41 #include <time.h>
  42 #if APR_HAVE_UNISTD_H
  43 #include <unistd.h>
  44 #endif
  45
  46 #include <stdio.h>
  47 #include <stdarg.h>
  48 #include <stdlib.h>
  49
  50 #ifdef HAVE_PWD_H
  51 #include <pwd.h>
  52 #endif
  53
  54 #ifdef HAVE_GRP_H
  55 #include <grp.h>
  56 #endif
  57
  58 /*
  59  ***********************************************************************
  60  * There is no initgroups() in QNX, so I believe this is safe :-)
  61  * Use cc -osuexec -3 -O -mf -DQNX suexec.c to compile.
  62  *
  63  * May 17, 1997.
  64  * Igor N. Kovalenko -- infoh mail.wplus.net
  65  ***********************************************************************
  66  */
  67
  68 #if defined(NEED_INITGROUPS)
  69 int initgroups(const char *name, gid_t basegid)
  70 {
  71     /* QNX and MPE do not appear to support supplementary groups. */
  72     return 0;
  73 }
  74 #endif
  75
  76 #if defined(SUNOS4)
  77 extern char *sys_errlist[];
  78 #define strerror(x) sys_errlist[(x)]
  79 #endif
  80
  81 #if defined(PATH_MAX)
  82 #define AP_MAXPATH PATH_MAX
  83 #elif defined(MAXPATHLEN)
  84 #define AP_MAXPATH MAXPATHLEN
  85 #else
  86 #define AP_MAXPATH 8192
  87 #endif
  88
  89 #define AP_ENVBUF 256
  90
  91 extern char **environ;
  92 static FILE *log = NULL;
  93
  94 static const char *const safe_env_lst[] =
  95 {
  96     /* variable name starts with */
  97     "HTTP_",
  98     "SSL_",
  99
 100     /* variable name is */
 101     "AUTH_TYPE=",
 102     "CONTENT_LENGTH=",
 103     "CONTENT_TYPE=",
 104     "DATE_GMT=",
 105     "DATE_LOCAL=",
 106     "DOCUMENT_NAME=",
 107     "DOCUMENT_PATH_INFO=",
 108     "DOCUMENT_ROOT=",
 109     "DOCUMENT_URI=",
 110     "GATEWAY_INTERFACE=",
 111     "HTTPS=",
 112     "LAST_MODIFIED=",
 113     "PATH_INFO=",
 114     "PATH_TRANSLATED=",
 115     "QUERY_STRING=",
 116     "QUERY_STRING_UNESCAPED=",
 117     "REMOTE_ADDR=",
 118     "REMOTE_HOST=",
 119     "REMOTE_IDENT=",
 120     "REMOTE_PORT=",
 121     "REMOTE_USER=",
 122     "REDIRECT_HANDLER=",
 123     "REDIRECT_QUERY_STRING=",
 124     "REDIRECT_REMOTE_USER=",
 125     "REDIRECT_STATUS=",
 126     "REDIRECT_URL=",
 127     "REQUEST_METHOD=",
 128     "REQUEST_URI=",
 129     "SCRIPT_FILENAME=",
 130     "SCRIPT_NAME=",
 131     "SCRIPT_URI=",
 132     "SCRIPT_URL=",
 133     "SERVER_ADMIN=",
 134     "SERVER_NAME=",
 135     "SERVER_ADDR=",
 136     "SERVER_PORT=",
 137     "SERVER_PROTOCOL=",
 138     "SERVER_SIGNATURE=",
 139     "SERVER_SOFTWARE=",
 140     "UNIQUE_ID=",
 141     "USER_NAME=",
 142     "TZ=",
 143     NULL
 144 };
 145
 146
 147 static void err_output(int is_error, const char *fmt, va_list ap)
 148 {
 149 #ifdef AP_LOG_EXEC
 150     time_t timevar;
 151     struct tm *lt;
 152
 153     if (!log) {
 154         if ((log = fopen(AP_LOG_EXEC, "a")) == NULL) {
 155             fprintf(stderr, "suexec failure: could not open log file\n");
 156             perror("fopen");
 157             exit(1);
 158         }
 159     }
 160
 161     if (is_error) {
 162         fprintf(stderr, "suexec policy violation: see suexec log for more "
 163                         "details\n");
 164     }
 165
 166     time(&timevar);
 167     lt = localtime(&timevar);
 168
 169     fprintf(log, "[%d-%.2d-%.2d %.2d:%.2d:%.2d]: ",
 170             lt->tm_year + 1900, lt->tm_mon + 1, lt->tm_mday,
 171             lt->tm_hour, lt->tm_min, lt->tm_sec);
 172
 173     vfprintf(log, fmt, ap);
 174
 175     fflush(log);
 176 #endif /* AP_LOG_EXEC */
 177     return;
 178 }
 179
 180 static void log_err(const char *fmt,...)
 181 {
 182 #ifdef AP_LOG_EXEC
 183     va_list ap;
 184
 185     va_start(ap, fmt);
 186     err_output(1, fmt, ap); /* 1 == is_error */
 187     va_end(ap);
 188 #endif /* AP_LOG_EXEC */
 189     return;
 190 }
 191
 192 static void log_no_err(const char *fmt,...)
 193 {
 194 #ifdef AP_LOG_EXEC
 195     va_list ap;
 196
 197     va_start(ap, fmt);
 198     err_output(0, fmt, ap); /* 0 == !is_error */
 199     va_end(ap);
 200 #endif /* AP_LOG_EXEC */
 201     return;
 202 }
 203
 204 static void clean_env(void)
 205 {
 206     char pathbuf[512];
 207     char **cleanenv;
 208     char **ep;
 209     int cidx = 0;
 210     int idx;
 211
 212     /* While cleaning the environment, the environment should be clean.
 213      * (e.g. malloc() may get the name of a file for writing debugging info.
 214      * Bad news if MALLOC_DEBUG_FILE is set to /etc/passwd.  Sprintf() may be
 215      * susceptible to bad locale settings....)
 216      * (from PR 2790)
 217      */
 218     char **envp = environ;
 219     char *empty_ptr = NULL;
 220
 221     environ = &empty_ptr; /* VERY safe environment */
 222
 223     if ((cleanenv = (char **) calloc(AP_ENVBUF, sizeof(char *))) == NULL) {
 224         log_err("failed to malloc memory for environment\n");
 225         exit(120);
 226     }
 227
 228     sprintf(pathbuf, "PATH=%s", AP_SAFE_PATH);
 229     cleanenv[cidx] = strdup(pathbuf);
 230     cidx++;
 231
 232     for (ep = envp; *ep && cidx < AP_ENVBUF-1; ep++) {
 233         for (idx = 0; safe_env_lst[idx]; idx++) {
 234             if (!strncmp(*ep, safe_env_lst[idx],
 235                          strlen(safe_env_lst[idx]))) {
 236                 cleanenv[cidx] = *ep;
 237                 cidx++;
 238                 break;
 239             }
 240         }
 241     }
 242
 243     cleanenv[cidx] = NULL;
 244
 245     environ = cleanenv;
 246 }
 247
 248 int main(int argc, char *argv[])
 249 {
 250     int userdir = 0;        /* ~userdir flag             */
 251     uid_t uid;              /* user information          */
 252     gid_t gid;              /* target group placeholder  */
 253     char *target_uname;     /* target user name          */
 254     char *target_gname;     /* target group name         */
 255     char *target_homedir;   /* target home directory     */
 256     char *actual_uname;     /* actual user name          */
 257     char *actual_gname;     /* actual group name         */
 258     char *prog;             /* name of this program      */
 259     char *cmd;              /* command to be executed    */
 260     char cwd[AP_MAXPATH];   /* current working directory */
 261     char dwd[AP_MAXPATH];   /* docroot working directory */
 262     struct passwd *pw;      /* password entry holder     */
 263     struct group *gr;       /* group entry holder        */
 264     struct stat dir_info;   /* directory info holder     */
 265     struct stat prg_info;   /* program info holder       */
 266
 267     /*
 268      * Start with a "clean" environment
 269      */
 270     clean_env();
 271
 272     prog = argv[0];
 273     /*
 274      * Check existence/validity of the UID of the user
 275      * running this program.  Error out if invalid.
 276      */
 277     uid = getuid();
 278     if ((pw = getpwuid(uid)) == NULL) {
 279         log_err("crit: invalid uid: (%ld)\n", uid);
 280         exit(102);
 281     }
 282     /*
 283      * See if this is a 'how were you compiled' request, and
 284      * comply if so.
 285      */
 286     if ((argc > 1)
 287         && (! strcmp(argv[1], "-V"))
 288         && ((uid == 0)
 289 #ifdef _OSD_POSIX
 290         /* User name comparisons are case insensitive on BS2000/OSD */
 291             || (! strcasecmp(AP_HTTPD_USER, pw->pw_name)))
 292 #else  /* _OSD_POSIX */
 293             || (! strcmp(AP_HTTPD_USER, pw->pw_name)))
 294 #endif /* _OSD_POSIX */
 295         ) {
 296 #ifdef AP_DOC_ROOT
 297         fprintf(stderr, " -D AP_DOC_ROOT=\"%s\"\n", AP_DOC_ROOT);
 298 #endif
 299 #ifdef AP_GID_MIN
 300         fprintf(stderr, " -D AP_GID_MIN=%d\n", AP_GID_MIN);
 301 #endif
 302 #ifdef AP_HTTPD_USER
 303         fprintf(stderr, " -D AP_HTTPD_USER=\"%s\"\n", AP_HTTPD_USER);
 304 #endif
 305 #ifdef AP_LOG_EXEC
 306         fprintf(stderr, " -D AP_LOG_EXEC=\"%s\"\n", AP_LOG_EXEC);
 307 #endif
 308 #ifdef AP_SAFE_PATH
 309         fprintf(stderr, " -D AP_SAFE_PATH=\"%s\"\n", AP_SAFE_PATH);
 310 #endif
 311 #ifdef AP_SUEXEC_UMASK
 312         fprintf(stderr, " -D AP_SUEXEC_UMASK=%03o\n", AP_SUEXEC_UMASK);
 313 #endif
 314 #ifdef AP_UID_MIN
 315         fprintf(stderr, " -D AP_UID_MIN=%d\n", AP_UID_MIN);
 316 #endif
 317 #ifdef AP_USERDIR_SUFFIX
 318         fprintf(stderr, " -D AP_USERDIR_SUFFIX=\"%s\"\n", AP_USERDIR_SUFFIX);
 319 #endif
 320         exit(0);
 321     }
 322     /*
 323      * If there are a proper number of arguments, set
 324      * all of them to variables.  Otherwise, error out.
 325      */
 326     if (argc < 4) {
 327         log_err("too few arguments\n");
 328         exit(101);
 329     }
 330     target_uname = argv[1];
 331     target_gname = argv[2];
 332     cmd = argv[3];
 333
 334     /*
 335      * Check to see if the user running this program
 336      * is the user allowed to do so as defined in
 337      * suexec.h.  If not the allowed user, error out.
 338      */
 339 #ifdef _OSD_POSIX
 340     /* User name comparisons are case insensitive on BS2000/OSD */
 341     if (strcasecmp(AP_HTTPD_USER, pw->pw_name)) {
 342         log_err("user mismatch (%s instead of %s)\n", pw->pw_name, AP_HTTPD_USER);
 343         exit(103);
 344     }
 345 #else  /*_OSD_POSIX*/
 346     if (strcmp(AP_HTTPD_USER, pw->pw_name)) {
 347         log_err("user mismatch (%s instead of %s)\n", pw->pw_name, AP_HTTPD_USER);
 348         exit(103);
 349     }
 350 #endif /*_OSD_POSIX*/
 351
 352     /*
 353      * Check for a leading '/' (absolute path) in the command to be executed,
 354      * or attempts to back up out of the current directory,
 355      * to protect against attacks.  If any are
 356      * found, error out.  Naughty naughty crackers.
 357      */
 358     if ((cmd[0] == '/') || (!strncmp(cmd, "../", 3))
 359         || (strstr(cmd, "/../") != NULL)) {
 360         log_err("invalid command (%s)\n", cmd);
 361         exit(104);
 362     }
 363
 364     /*
 365      * Check to see if this is a ~userdir request.  If
 366      * so, set the flag, and remove the '~' from the
 367      * target username.
 368      */
 369     if (!strncmp("~", target_uname, 1)) {
 370         target_uname++;
 371         userdir = 1;
 372     }
 373
 374     /*
 375      * Error out if the target username is invalid.
 376      */
 377     if (strspn(target_uname, "1234567890") != strlen(target_uname)) {
 378         if ((pw = getpwnam(target_uname)) == NULL) {
 379             log_err("invalid target user name: (%s)\n", target_uname);
 380             exit(105);
 381         }
 382     }
 383     else {
 384         if ((pw = getpwuid(atoi(target_uname))) == NULL) {
 385             log_err("invalid target user id: (%s)\n", target_uname);
 386             exit(121);
 387         }
 388     }
 389
 390     /*
 391      * Error out if the target group name is invalid.
 392      */
 393     if (strspn(target_gname, "1234567890") != strlen(target_gname)) {
 394         if ((gr = getgrnam(target_gname)) == NULL) {
 395             log_err("invalid target group name: (%s)\n", target_gname);
 396             exit(106);
 397         }
 398     }
 399     else {
 400         if ((gr = getgrgid(atoi(target_gname))) == NULL) {
 401             log_err("invalid target group id: (%s)\n", target_gname);
 402             exit(106);
 403         }
 404     }
 405     gid = gr->gr_gid;
 406     actual_gname = strdup(gr->gr_name);
 407
 408 #ifdef _OSD_POSIX
 409     /*
 410      * Initialize BS2000 user environment
 411      */
 412     {
 413         pid_t pid;
 414         int status;
 415
 416         switch (pid = ufork(target_uname)) {
 417         case -1:    /* Error */
 418             log_err("failed to setup bs2000 environment for user %s: %s\n",
 419                     target_uname, strerror(errno));
 420             exit(150);
 421         case 0:     /* Child */
 422             break;
 423         default:    /* Father */
 424             while (pid != waitpid(pid, &status, 0))
 425                 ;
 426             /* @@@ FIXME: should we deal with STOP signals as well? */
 427             if (WIFSIGNALED(status)) {
 428                 kill (getpid(), WTERMSIG(status));
 429             }
 430             exit(WEXITSTATUS(status));
 431         }
 432     }
 433 #endif /*_OSD_POSIX*/
 434
 435     /*
 436      * Save these for later since initgroups will hose the struct
 437      */
 438     uid = pw->pw_uid;
 439     actual_uname = strdup(pw->pw_name);
 440     target_homedir = strdup(pw->pw_dir);
 441
 442     /*
 443      * Log the transaction here to be sure we have an open log
 444      * before we setuid().
 445      */
 446     log_no_err("uid: (%s/%s) gid: (%s/%s) cmd: %s\n",
 447                target_uname, actual_uname,
 448                target_gname, actual_gname,
 449                cmd);
 450
 451     /*
 452      * Error out if attempt is made to execute as root or as
 453      * a UID less than AP_UID_MIN.  Tsk tsk.
 454      */
 455     if ((uid == 0) || (uid < AP_UID_MIN)) {
 456         log_err("cannot run as forbidden uid (%d/%s)\n", uid, cmd);
 457         exit(107);
 458     }
 459
 460     /*
 461      * Error out if attempt is made to execute as root group
 462      * or as a GID less than AP_GID_MIN.  Tsk tsk.
 463      */
 464     if ((gid == 0) || (gid < AP_GID_MIN)) {
 465         log_err("cannot run as forbidden gid (%d/%s)\n", gid, cmd);
 466         exit(108);
 467     }
 468
 469     /*
 470      * Change UID/GID here so that the following tests work over NFS.
 471      *
 472      * Initialize the group access list for the target user,
 473      * and setgid() to the target group. If unsuccessful, error out.
 474      */
 475     if (((setgid(gid)) != 0) || (initgroups(actual_uname, gid) != 0)) {
 476         log_err("failed to setgid (%ld: %s)\n", gid, cmd);
 477         exit(109);
 478     }
 479
 480     /*
 481      * setuid() to the target user.  Error out on fail.
 482      */
 483     if ((setuid(uid)) != 0) {
 484         log_err("failed to setuid (%ld: %s)\n", uid, cmd);
 485         exit(110);
 486     }
 487
 488     /*
 489      * Get the current working directory, as well as the proper
 490      * document root (dependant upon whether or not it is a
 491      * ~userdir request).  Error out if we cannot get either one,
 492      * or if the current working directory is not in the docroot.
 493      * Use chdir()s and getcwd()s to avoid problems with symlinked
 494      * directories.  Yuck.
 495      */
 496     if (getcwd(cwd, AP_MAXPATH) == NULL) {
 497         log_err("cannot get current working directory\n");
 498         exit(111);
 499     }
 500
 501     if (userdir) {
 502         if (((chdir(target_homedir)) != 0) ||
 503             ((chdir(AP_USERDIR_SUFFIX)) != 0) ||
 504             ((getcwd(dwd, AP_MAXPATH)) == NULL) ||
 505             ((chdir(cwd)) != 0)) {
 506             log_err("cannot get docroot information (%s)\n", target_homedir);
 507             exit(112);
 508         }
 509     }
 510     else {
 511         if (((chdir(AP_DOC_ROOT)) != 0) ||
 512             ((getcwd(dwd, AP_MAXPATH)) == NULL) ||
 513             ((chdir(cwd)) != 0)) {
 514             log_err("cannot get docroot information (%s)\n", AP_DOC_ROOT);
 515             exit(113);
 516         }
 517     }
 518
 519     if ((strncmp(cwd, dwd, strlen(dwd))) != 0) {
 520         log_err("command not in docroot (%s/%s)\n", cwd, cmd);
 521         exit(114);
 522     }
 523
 524     /*
 525      * Stat the cwd and verify it is a directory, or error out.
 526      */
 527     if (((lstat(cwd, &dir_info)) != 0) || !(S_ISDIR(dir_info.st_mode))) {
 528         log_err("cannot stat directory: (%s)\n", cwd);
 529         exit(115);
 530     }
 531
 532     /*
 533      * Error out if cwd is writable by others.
 534      */
 535     if ((dir_info.st_mode & S_IWOTH) || (dir_info.st_mode & S_IWGRP)) {
 536         log_err("directory is writable by others: (%s)\n", cwd);
 537         exit(116);
 538     }
 539
 540     /*
 541      * Error out if we cannot stat the program.
 542      */
 543     if (((lstat(cmd, &prg_info)) != 0) || (S_ISLNK(prg_info.st_mode))) {
 544         log_err("cannot stat program: (%s)\n", cmd);
 545         exit(117);
 546     }
 547
 548     /*
 549      * Error out if the program is writable by others.
 550      */
 551     if ((prg_info.st_mode & S_IWOTH) || (prg_info.st_mode & S_IWGRP)) {
 552         log_err("file is writable by others: (%s/%s)\n", cwd, cmd);
 553         exit(118);
 554     }
 555
 556     /*
 557      * Error out if the file is setuid or setgid.
 558      */
 559     if ((prg_info.st_mode & S_ISUID) || (prg_info.st_mode & S_ISGID)) {
 560         log_err("file is either setuid or setgid: (%s/%s)\n", cwd, cmd);
 561         exit(119);
 562     }
 563
 564     /*
 565      * Error out if the target name/group is different from
 566      * the name/group of the cwd or the program.
 567      */
 568     if ((uid != dir_info.st_uid) ||
 569         (gid != dir_info.st_gid) ||
 570         (uid != prg_info.st_uid) ||
 571         (gid != prg_info.st_gid)) {
 572         log_err("target uid/gid (%ld/%ld) mismatch "
 573                 "with directory (%ld/%ld) or program (%ld/%ld)\n",
 574                 uid, gid,
 575                 dir_info.st_uid, dir_info.st_gid,
 576                 prg_info.st_uid, prg_info.st_gid);
 577         exit(120);
 578     }
 579     /*
 580      * Error out if the program is not executable for the user.
 581      * Otherwise, she won't find any error in the logs except for
 582      * "[error] Premature end of script headers: ..."
 583      */
 584     if (!(prg_info.st_mode & S_IXUSR)) {
 585         log_err("file has no execute permission: (%s/%s)\n", cwd, cmd);
 586         exit(121);
 587     }
 588
 589 #ifdef AP_SUEXEC_UMASK
 590     /*
 591      * umask() uses inverse logic; bits are CLEAR for allowed access.
 592      */
 593     if ((~AP_SUEXEC_UMASK) & 0022) {
 594         log_err("notice: AP_SUEXEC_UMASK of %03o allows "
 595                 "write permission to group and/or other\n", AP_SUEXEC_UMASK);
 596     }
 597     umask(AP_SUEXEC_UMASK);
 598 #endif /* AP_SUEXEC_UMASK */
 599
 600     /*
 601      * Be sure to close the log file so the CGI can't
 602      * mess with it.  If the exec fails, it will be reopened
 603      * automatically when log_err is called.  Note that the log
 604      * might not actually be open if AP_LOG_EXEC isn't defined.
 605      * However, the "log" cell isn't ifdef'd so let's be defensive
 606      * and assume someone might have done something with it
 607      * outside an ifdef'd AP_LOG_EXEC block.
 608      */
 609     if (log != NULL) {
 610         fclose(log);
 611         log = NULL;
 612     }
 613
 614     /*
 615      * Execute the command, replacing our image with its own.
 616      */
 617 #ifdef NEED_HASHBANG_EMUL
 618     /* We need the #! emulation when we want to execute scripts */
 619     {
 620         extern char **environ;
 621
 622         ap_execve(cmd, &argv[3], environ);
 623     }
 624 #else /*NEED_HASHBANG_EMUL*/
 625     execv(cmd, &argv[3]);
 626 #endif /*NEED_HASHBANG_EMUL*/
 627
 628     /*
 629      * (I can't help myself...sorry.)
 630      *
 631      * Uh oh.  Still here.  Where's the kaboom?  There was supposed to be an
 632      * EARTH-shattering kaboom!
 633      *
 634      * Oh well, log the failure and error out.
 635      */
 636     log_err("(%d)%s: exec failed (%s)\n", errno, strerror(errno), cmd);
 637     exit(255);
 638 }