httpd/support/suexec.c

	suexec.c revision 64185f9824e42f21ca7b9ae6c004484215c031a7
/* ====================================================================
 * Copyright (c) 1995-2000 The Apache Software Foundation.  All rights reserved.
 *
 * 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 acknowledgment:
 *    "This product includes software developed by the Apache Software Foundation
 *    for use in the Apache HTTP server project (http://www.apache.org/)."
 *
 * 4. The names "Apache Server" and "Apache Software Foundation" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Software Foundation.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the Apache Software Foundation
 *    for use in the Apache HTTP server project (http://www.apache.org/)."
 *
 * THIS SOFTWARE IS PROVIDED BY THE Apache Software Foundation ``AS IS'' AND ANY
 * EXPRESSED 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 Apache Software Foundation OR
 * ITS 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was originally based
 * on public domain software written at the National Center for
 * Supercomputing Applications, University of Illinois, Urbana-Champaign.
 * For more information on the Apache Software Foundation and the Apache HTTP server
 * project, please see <http://www.apache.org/>.
 *
 */

/*
 * suexec.c -- "Wrapper" support program for suEXEC behaviour for Apache
 *
 ***********************************************************************
 *
 * NOTE! : DO NOT edit this code!!!  Unless you know what you are doing,
 *         editing this code might open up your system in unexpected
 *         ways to would-be crackers.  Every precaution has been taken
 *         to make this code as safe as possible; alter it at your own
 *         risk.
 *
 ***********************************************************************
 *
 *
 */

#include "ap_config.h"
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <stdarg.h>

#include "suexec.h"

/*
 ***********************************************************************
 * There is no initgroups() in QNX, so I believe this is safe :-)
 * Use cc -osuexec -3 -O -mf -DQNX suexec.c to compile.
 *
 * May 17, 1997.
 * Igor N. Kovalenko -- infoh@mail.wplus.net
 ***********************************************************************
 */

#if defined(NEED_INITGROUPS)
int initgroups(const char *name, gid_t basegid)
{
/* QNX and MPE do not appear to support supplementary groups. */
    return 0;
}
#endif

#if defined(PATH_MAX)
#define AP_MAXPATH PATH_MAX
#elif defined(MAXPATHLEN)
#define AP_MAXPATH MAXPATHLEN
#else
#define AP_MAXPATH 8192
#endif

#define AP_ENVBUF 256

extern char **environ;
static FILE *log = NULL;

char *safe_env_lst[] =
{
    "AUTH_TYPE",
    "CONTENT_LENGTH",
    "CONTENT_TYPE",
    "DATE_GMT",
    "DATE_LOCAL",
    "DOCUMENT_NAME",
    "DOCUMENT_PATH_INFO",
    "DOCUMENT_ROOT",
    "DOCUMENT_URI",
    "FILEPATH_INFO",
    "GATEWAY_INTERFACE",
    "LAST_MODIFIED",
    "PATH_INFO",
    "PATH_TRANSLATED",
    "QUERY_STRING",
    "QUERY_STRING_UNESCAPED",
    "REMOTE_ADDR",
    "REMOTE_HOST",
    "REMOTE_IDENT",
    "REMOTE_PORT",
    "REMOTE_USER",
    "REDIRECT_QUERY_STRING",
    "REDIRECT_STATUS",
    "REDIRECT_URL",
    "REQUEST_METHOD",
    "REQUEST_URI",
    "SCRIPT_FILENAME",
    "SCRIPT_NAME",
    "SCRIPT_URI",
    "SCRIPT_URL",
    "SERVER_ADMIN",
    "SERVER_NAME",
    "SERVER_ADDR",
    "SERVER_PORT",
    "SERVER_PROTOCOL",
    "SERVER_SOFTWARE",
    "UNIQUE_ID",
    "USER_NAME",
    "TZ",
    NULL
};


static void err_output(const char *fmt, va_list ap)
{
#ifdef LOG_EXEC
    time_t timevar;
    struct tm *lt;

    if (!log) {
    if ((log = fopen(LOG_EXEC, "a")) == NULL) {
        fprintf(stderr, "failed to open log file\n");
        perror("fopen");
        exit(1);
    }
    }

    time(&timevar);
    lt = localtime(&timevar);

    fprintf(log, "[%d-%.2d-%.2d %.2d:%.2d:%.2d]: ",
        lt->tm_year + 1900, lt->tm_mon + 1, lt->tm_mday,
        lt->tm_hour, lt->tm_min, lt->tm_sec);

    vfprintf(log, fmt, ap);

    fflush(log);
#endif /* LOG_EXEC */
    return;
}

static void log_err(const char *fmt,...)
{
#ifdef LOG_EXEC
    va_list ap;

    va_start(ap, fmt);
    err_output(fmt, ap);
    va_end(ap);
#endif /* LOG_EXEC */
    return;
}

static void clean_env(void)
{
    char pathbuf[512];
    char **cleanenv;
    char **ep;
    int cidx = 0;
    int idx;


    if ((cleanenv = (char **) calloc(AP_ENVBUF, sizeof(char *))) == NULL) {
        log_err("failed to malloc memory for environment\n");
    exit(120);
    }

    sprintf(pathbuf, "PATH=%s", SAFE_PATH);
    cleanenv[cidx] = strdup(pathbuf);
    cidx++;

    for (ep = environ; *ep && cidx < AP_ENVBUF-1; ep++) {
    if (!strncmp(*ep, "HTTP_", 5)) {
        cleanenv[cidx] = *ep;
        cidx++;
    }
    else {
        for (idx = 0; safe_env_lst[idx]; idx++) {
        if (!strncmp(*ep, safe_env_lst[idx],
                 strlen(safe_env_lst[idx]))) {
            cleanenv[cidx] = *ep;
            cidx++;
            break;
        }
        }
    }
    }

    cleanenv[cidx] = NULL;

    environ = cleanenv;
}

int main(int argc, char *argv[])
{
    int userdir = 0;        /* ~userdir flag             */
    uid_t uid;          /* user information          */
    gid_t gid;          /* target group placeholder  */
    char *target_uname;     /* target user name          */
    char *target_gname;     /* target group name         */
    char *target_homedir;   /* target home directory     */
    char *actual_uname;     /* actual user name          */
    char *actual_gname;     /* actual group name         */
    char *prog;         /* name of this program      */
    char *cmd;          /* command to be executed    */
    char cwd[AP_MAXPATH];   /* current working directory */
    char dwd[AP_MAXPATH];   /* docroot working directory */
    struct passwd *pw;      /* password entry holder     */
    struct group *gr;       /* group entry holder        */
    struct stat dir_info;   /* directory info holder     */
    struct stat prg_info;   /* program info holder       */

    /*
     * If there are a proper number of arguments, set
     * all of them to variables.  Otherwise, error out.
     */
    prog = argv[0];
    if (argc < 4) {
    log_err("too few arguments\n");
    exit(101);
    }
    target_uname = argv[1];
    target_gname = argv[2];
    cmd = argv[3];

    /*
     * Check existence/validity of the UID of the user
     * running this program.  Error out if invalid.
     */
    uid = getuid();
    if ((pw = getpwuid(uid)) == NULL) {
    log_err("invalid uid: (%ld)\n", uid);
    exit(102);
    }

    /*
     * Check to see if the user running this program
     * is the user allowed to do so as defined in
     * suexec.h.  If not the allowed user, error out.
     */
#ifdef _OSD_POSIX
    /* User name comparisons are case insensitive on BS2000/OSD */
    if (strcasecmp(HTTPD_USER, pw->pw_name)) {
        log_err("user mismatch (%s instead of %s)\n", pw->pw_name, HTTPD_USER);
    exit(103);
    }
#else  /*_OSD_POSIX*/
    if (strcmp(HTTPD_USER, pw->pw_name)) {
        log_err("user mismatch (%s instead of %s)\n", pw->pw_name, HTTPD_USER);
    exit(103);
    }
#endif /*_OSD_POSIX*/

    /*
     * Check for a leading '/' (absolute path) in the command to be executed,
     * or attempts to back up out of the current directory,
     * to protect against attacks.  If any are
     * found, error out.  Naughty naughty crackers.
     */
    if ((cmd[0] == '/') || (!strncmp(cmd, "../", 3))
    || (strstr(cmd, "/../") != NULL)) {
        log_err("invalid command (%s)\n", cmd);
    exit(104);
    }

    /*
     * Check to see if this is a ~userdir request.  If
     * so, set the flag, and remove the '~' from the
     * target username.
     */
    if (!strncmp("~", target_uname, 1)) {
    target_uname++;
    userdir = 1;
    }

    /*
     * Error out if the target username is invalid.
     */
    if ((pw = getpwnam(target_uname)) == NULL) {
    log_err("invalid target user name: (%s)\n", target_uname);
    exit(105);
    }

    /*
     * Error out if the target group name is invalid.
     */
    if (strspn(target_gname, "1234567890") != strlen(target_gname)) {
    if ((gr = getgrnam(target_gname)) == NULL) {
        log_err("invalid target group name: (%s)\n", target_gname);
        exit(106);
    }
    gid = gr->gr_gid;
    actual_gname = strdup(gr->gr_name);
    }
    else {
    gid = atoi(target_gname);
    actual_gname = strdup(target_gname);
    }

#ifdef _OSD_POSIX
    /*
     * Initialize BS2000 user environment
     */
    {
    pid_t pid;
    int status;

    switch (pid = ufork(target_uname))
    {
    case -1:    /* Error */
        log_err("failed to setup bs2000 environment for user %s: %s\n",
            target_uname, strerror(errno));
        exit(150);
    case 0: /* Child */
        break;
    default:    /* Father */
        while (pid != waitpid(pid, &status, 0))
        ;
        /* @@@ FIXME: should we deal with STOP signals as well? */
        if (WIFSIGNALED(status))
        kill (getpid(), WTERMSIG(status));
        exit(WEXITSTATUS(status));
    }
    }
#endif /*_OSD_POSIX*/

    /*
     * Save these for later since initgroups will hose the struct
     */
    uid = pw->pw_uid;
    actual_uname = strdup(pw->pw_name);
    target_homedir = strdup(pw->pw_dir);

    /*
     * Log the transaction here to be sure we have an open log
     * before we setuid().
     */
    log_err("uid: (%s/%s) gid: (%s/%s) cmd: %s\n",
        target_uname, actual_uname,
        target_gname, actual_gname,
        cmd);

    /*
     * Error out if attempt is made to execute as root or as
     * a UID less than UID_MIN.  Tsk tsk.
     */
    if ((uid == 0) || (uid < UID_MIN)) {
    log_err("cannot run as forbidden uid (%d/%s)\n", uid, cmd);
    exit(107);
    }

    /*
     * Error out if attempt is made to execute as root group
     * or as a GID less than GID_MIN.  Tsk tsk.
     */
    if ((gid == 0) || (gid < GID_MIN)) {
    log_err("cannot run as forbidden gid (%d/%s)\n", gid, cmd);
    exit(108);
    }

    /*
     * Change UID/GID here so that the following tests work over NFS.
     *
     * Initialize the group access list for the target user,
     * and setgid() to the target group. If unsuccessful, error out.
     */
    if (((setgid(gid)) != 0) || (initgroups(actual_uname, gid) != 0)) {
    log_err("failed to setgid (%ld: %s)\n", gid, cmd);
    exit(109);
    }

    /*
     * setuid() to the target user.  Error out on fail.
     */
    if ((setuid(uid)) != 0) {
    log_err("failed to setuid (%ld: %s)\n", uid, cmd);
    exit(110);
    }

    /*
     * Get the current working directory, as well as the proper
     * document root (dependant upon whether or not it is a
     * ~userdir request).  Error out if we cannot get either one,
     * or if the current working directory is not in the docroot.
     * Use chdir()s and getcwd()s to avoid problems with symlinked
     * directories.  Yuck.
     */
    if (getcwd(cwd, AP_MAXPATH) == NULL) {
    log_err("cannot get current working directory\n");
    exit(111);
    }

    if (userdir) {
    if (((chdir(target_homedir)) != 0) ||
        ((chdir(USERDIR_SUFFIX)) != 0) ||
        ((getcwd(dwd, AP_MAXPATH)) == NULL) ||
        ((chdir(cwd)) != 0)) {
        log_err("cannot get docroot information (%s)\n", target_homedir);
        exit(112);
    }
    }
    else {
    if (((chdir(DOC_ROOT)) != 0) ||
        ((getcwd(dwd, AP_MAXPATH)) == NULL) ||
        ((chdir(cwd)) != 0)) {
        log_err("cannot get docroot information (%s)\n", DOC_ROOT);
        exit(113);
    }
    }

    if ((strncmp(cwd, dwd, strlen(dwd))) != 0) {
    log_err("command not in docroot (%s/%s)\n", cwd, cmd);
    exit(114);
    }

    /*
     * Stat the cwd and verify it is a directory, or error out.
     */
    if (((lstat(cwd, &dir_info)) != 0) || !(S_ISDIR(dir_info.st_mode))) {
    log_err("cannot stat directory: (%s)\n", cwd);
    exit(115);
    }

    /*
     * Error out if cwd is writable by others.
     */
    if ((dir_info.st_mode & S_IWOTH) || (dir_info.st_mode & S_IWGRP)) {
    log_err("directory is writable by others: (%s)\n", cwd);
    exit(116);
    }

    /*
     * Error out if we cannot stat the program.
     */
    if (((lstat(cmd, &prg_info)) != 0) || (S_ISLNK(prg_info.st_mode))) {
    log_err("cannot stat program: (%s)\n", cmd);
    exit(117);
    }

    /*
     * Error out if the program is writable by others.
     */
    if ((prg_info.st_mode & S_IWOTH) || (prg_info.st_mode & S_IWGRP)) {
    log_err("file is writable by others: (%s/%s)\n", cwd, cmd);
    exit(118);
    }

    /*
     * Error out if the file is setuid or setgid.
     */
    if ((prg_info.st_mode & S_ISUID) || (prg_info.st_mode & S_ISGID)) {
    log_err("file is either setuid or setgid: (%s/%s)\n", cwd, cmd);
    exit(119);
    }

    /*
     * Error out if the target name/group is different from
     * the name/group of the cwd or the program.
     */
    if ((uid != dir_info.st_uid) ||
    (gid != dir_info.st_gid) ||
    (uid != prg_info.st_uid) ||
    (gid != prg_info.st_gid)) {
    log_err("target uid/gid (%ld/%ld) mismatch "
        "with directory (%ld/%ld) or program (%ld/%ld)\n",
        uid, gid,
        dir_info.st_uid, dir_info.st_gid,
        prg_info.st_uid, prg_info.st_gid);
    exit(120);
    }
    /*
     * Error out if the program is not executable for the user.
     * Otherwise, she won't find any error in the logs except for
     * "[error] Premature end of script headers: ..."
     */
    if (!(prg_info.st_mode & S_IXUSR)) {
    log_err("file has no execute permission: (%s/%s)\n", cwd, cmd);
    exit(121);
    }

    clean_env();

    /*
     * Be sure to close the log file so the CGI can't
     * mess with it.  If the exec fails, it will be reopened
     * automatically when log_err is called.  Note that the log
     * might not actually be open if LOG_EXEC isn't defined.
     * However, the "log" cell isn't ifdef'd so let's be defensive
     * and assume someone might have done something with it
     * outside an ifdef'd LOG_EXEC block.
     */
    if (log != NULL) {
    fclose(log);
    log = NULL;
    }

    /*
     * Execute the command, replacing our image with its own.
     */
#ifdef NEED_HASHBANG_EMUL
    /* We need the #! emulation when we want to execute scripts */
    {
    extern char **environ;

    ap_execve(cmd, &argv[3], environ);
    }
#else /*NEED_HASHBANG_EMUL*/
    execv(cmd, &argv[3]);
#endif /*NEED_HASHBANG_EMUL*/

    /*
     * (I can't help myself...sorry.)
     *
     * Uh oh.  Still here.  Where's the kaboom?  There was supposed to be an
     * EARTH-shattering kaboom!
     *
     * Oh well, log the failure and error out.
     */
    log_err("(%d)%s: exec failed (%s)\n", errno, strerror(errno), cmd);
    exit(255);
}