/* ====================================================================
 * Copyright (c) 1995-1997 The Apache Group.  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 Group
 *    for use in the Apache HTTP server project (http://www.apache.org/)."
 *
 * 4. The names "Apache Server" and "Apache Group" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission.
 *
 * 5. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the Apache Group
 *    for use in the Apache HTTP server project (http://www.apache.org/)."
 *
 * THIS SOFTWARE IS PROVIDED BY THE APACHE GROUP ``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 GROUP 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 Group 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 Group 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 "suexec.h"

#include <sys/param.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>
#include <sys/stat.h>

#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;

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",
    "SCRIPT_FILENAME",
    "SCRIPT_NAME",
    "SCRIPT_URI",
    "SCRIPT_URL",
    "SERVER_ADMIN",
    "SERVER_NAME",
    "SERVER_PORT",
    "SERVER_PROTOCOL",
    "SERVER_SOFTWARE",
    "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, "[%.2d:%.2d:%.2d %.2d-%.2d-%.2d]: ", lt->tm_hour, lt->tm_min,
	    lt->tm_sec, lt->tm_mday, (lt->tm_mon + 1), lt->tm_year);
    
    vfprintf(log, fmt, ap);

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

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;
}

void clean_env() 
{
    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 env mem\n");
	exit(120);
    }
    
    for (ep = environ; *ep && cidx < AP_ENVBUF; 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;
		}
	    }
	}
    }

    sprintf(pathbuf, "PATH=%s", SAFE_PATH);
    cleanenv[cidx] = strdup(pathbuf);
    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.
     */
    if (strcmp(HTTPD_USER, pw->pw_name)) {
	log_err("user mismatch (%s)\n", pw->pw_name);
	exit(103);
    }
    
    /*
     * 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);
    }

    /*
     * 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) %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);
    }

    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.
     */
    fclose(log);
    log = NULL;
    
    /*
     * Execute the command, replacing our image with its own.
     */
    execv(cmd, &argv[3]);

    /*
     * (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("exec failed (%s)\n", cmd);
    exit(255);
}