in support/suexec.c [298:726]
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 *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 */
/*
* Start with a "clean" environment
*/
clean_env();
/*
* 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("crit: invalid uid: (%lu)\n", (unsigned long)uid);
exit(102);
}
/*
* See if this is a 'how were you compiled' request, and
* comply if so.
*/
if ((argc > 1)
&& (! strcmp(argv[1], "-V"))
&& ((uid == 0)
#ifdef _OSD_POSIX
/* User name comparisons are case insensitive on BS2000/OSD */
|| (! strcasecmp(AP_HTTPD_USER, pw->pw_name)))
#else /* _OSD_POSIX */
|| (! strcmp(AP_HTTPD_USER, pw->pw_name)))
#endif /* _OSD_POSIX */
) {
#ifdef AP_DOC_ROOT
fprintf(stderr, " -D AP_DOC_ROOT=\"%s\"\n", AP_DOC_ROOT);
#endif
#ifdef AP_GID_MIN
fprintf(stderr, " -D AP_GID_MIN=%d\n", AP_GID_MIN);
#endif
#ifdef AP_HTTPD_USER
fprintf(stderr, " -D AP_HTTPD_USER=\"%s\"\n", AP_HTTPD_USER);
#endif
#if defined(AP_LOG_SYSLOG)
fprintf(stderr, " -D AP_LOG_SYSLOG\n");
#elif defined(AP_LOG_EXEC)
fprintf(stderr, " -D AP_LOG_EXEC=\"%s\"\n", AP_LOG_EXEC);
#endif
#ifdef AP_SAFE_PATH
fprintf(stderr, " -D AP_SAFE_PATH=\"%s\"\n", AP_SAFE_PATH);
#endif
#ifdef AP_SUEXEC_UMASK
fprintf(stderr, " -D AP_SUEXEC_UMASK=%03o\n", AP_SUEXEC_UMASK);
#endif
#ifdef AP_UID_MIN
fprintf(stderr, " -D AP_UID_MIN=%d\n", AP_UID_MIN);
#endif
#ifdef AP_USERDIR_SUFFIX
fprintf(stderr, " -D AP_USERDIR_SUFFIX=\"%s\"\n", AP_USERDIR_SUFFIX);
#endif
exit(0);
}
/*
* If there are a proper number of arguments, set
* all of them to variables. Otherwise, error out.
*/
if (argc < 4) {
log_err("too few arguments\n");
exit(101);
}
target_uname = argv[1];
target_gname = argv[2];
cmd = argv[3];
/*
* 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(AP_HTTPD_USER, pw->pw_name)) {
log_err("user mismatch (%s instead of %s)\n", pw->pw_name, AP_HTTPD_USER);
exit(103);
}
#else /*_OSD_POSIX*/
if (strcmp(AP_HTTPD_USER, pw->pw_name)) {
log_err("user mismatch (%s instead of %s)\n", pw->pw_name, AP_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 (strspn(target_uname, "1234567890") != strlen(target_uname)) {
if ((pw = getpwnam(target_uname)) == NULL) {
log_err("invalid target user name: (%s)\n", target_uname);
exit(105);
}
}
else {
long parsed_uid = safe_strtol(target_uname);
uid_t target_uid = parsed_uid;
/* uid_t may be signed or unsigned and may be smaller than
* long; try to catch long->(u)int conversion surprises and
* avoid calling getpwuid with a negative value though it
* should be safe anyway. */
if (parsed_uid < 0 || target_uid < 0 || target_uid != parsed_uid
|| (pw = getpwuid(target_uid)) == NULL) {
log_err("invalid target user id: (%s)\n", target_uname);
exit(121);
}
}
/*
* 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);
}
}
else {
long parsed_gid = safe_strtol(target_gname);
gid_t target_gid = parsed_gid;
/* See above on long to uid_t conversion. */
if (parsed_gid < 0 || target_gid < 0 || target_gid != parsed_gid
|| (gr = getgrgid(target_gid)) == NULL) {
log_err("invalid target group id: (%s)\n", target_gname);
exit(106);
}
}
gid = gr->gr_gid;
if ((actual_gname = strdup(gr->gr_name)) == NULL) {
log_err("failed to alloc memory\n");
exit(125);
}
#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);
if (actual_uname == NULL || target_homedir == NULL) {
log_err("failed to alloc memory\n");
exit(126);
}
/*
* Log the transaction here to be sure we have an open log
* before we setuid().
*/
log_no_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 AP_UID_MIN. Tsk tsk.
*/
if ((uid == 0) || (uid < AP_UID_MIN)) {
log_err("cannot run as forbidden uid (%lu/%s)\n", (unsigned long)uid, cmd);
exit(107);
}
/*
* Error out if attempt is made to execute as root group
* or as a GID less than AP_GID_MIN. Tsk tsk.
*/
if ((gid == 0) || (gid < AP_GID_MIN)) {
log_err("cannot run as forbidden gid (%lu/%s)\n", (unsigned long)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/initgroups (%lu: %s): %s\n",
(unsigned long)gid, cmd, strerror(errno));
exit(109);
}
/*
* setuid() to the target user. Error out on fail.
*/
if ((setuid(uid)) != 0) {
log_err("failed to setuid (%lu: %s): %s\n",
(unsigned long)uid, cmd, strerror(errno));
exit(110);
}
/*
* Get the current working directory, as well as the proper
* document root (dependent 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(AP_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(AP_DOC_ROOT)) != 0) ||
((getcwd(dwd, AP_MAXPATH)) == NULL) ||
((chdir(cwd)) != 0)) {
log_err("cannot get docroot information (%s)\n", AP_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 (%lu/%lu) mismatch "
"with directory (%lu/%lu) or program (%lu/%lu)\n",
(unsigned long)uid, (unsigned long)gid,
(unsigned long)dir_info.st_uid, (unsigned long)dir_info.st_gid,
(unsigned long)prg_info.st_uid, (unsigned long)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);
}
#ifdef AP_SUEXEC_UMASK
/*
* umask() uses inverse logic; bits are CLEAR for allowed access.
*/
if ((~AP_SUEXEC_UMASK) & 0022) {
log_err("notice: AP_SUEXEC_UMASK of %03o allows "
"write permission to group and/or other\n", AP_SUEXEC_UMASK);
}
umask(AP_SUEXEC_UMASK);
#endif /* AP_SUEXEC_UMASK */
/* Be sure to close the log file so the CGI can't mess with it. */
#ifdef AP_LOG_SYSLOG
if (log_open) {
closelog();
log_open = 0;
}
#else
if (log != NULL) {
#if APR_HAVE_FCNTL_H
/*
* ask fcntl(2) to set the FD_CLOEXEC flag on the log file,
* so it'll be automagically closed if the exec() call succeeds.
*/
fflush(log);
setbuf(log, NULL);
if ((fcntl(fileno(log), F_SETFD, FD_CLOEXEC) == -1)) {
log_err("error: can't set close-on-exec flag");
exit(122);
}
#else
/*
* In this case, exec() errors won't be logged because we have already
* dropped privileges and won't be able to reopen the log file.
*/
fclose(log);
log = NULL;
#endif
}
#endif
/*
* 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);
}