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git.ipfire.org Git - people/pmueller/ipfire-2.x.git/blob - src/misc-progs/setuid.c
1 /* This file is part of the IPCop Firewall.
3 * IPCop is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation; either version 2 of the License, or
6 * (at your option) any later version.
8 * IPCop is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
13 * You should have received a copy of the GNU General Public License
14 * along with IPCop; if not, write to the Free Software
15 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17 * Copyright (C) 2003-04-22 Robert Kerr <rkerr@go.to>
19 * $Id: setuid.c,v 1.2.2.1 2005/11/18 14:51:43 franck78 Exp $
28 #include <sys/types.h>
31 #include <sys/resource.h>
44 /* Trusted environment for executing commands */
45 char * trusted_env
[4] = {
46 "PATH=/usr/bin:/usr/sbin:/sbin:/bin",
52 /* Spawns a child process that uses /bin/sh to interpret a command.
53 * This is much the same in use and purpose as system(), yet as it uses execve
54 * to pass a trusted environment it's immune to attacks based upon changing
55 * IFS, ENV, BASH_ENV and other such variables.
56 * Note this does NOT guard against any other attacks, inparticular you MUST
57 * validate the command you are passing. If the command is formed from user
58 * input be sure to check this input is what you expect. Nasty things can
59 * happen if a user can inject ; or `` into your command for example */
60 int safe_system(char* command
) {
61 return system_core(command
, 0, 0, "safe_system");
64 /* Much like safe_system but lets you specify a non-root uid and gid to run
66 int unpriv_system(char* command
, uid_t uid
, gid_t gid
) {
67 return system_core(command
, uid
, gid
, "unpriv_system");
70 int system_core(char* command
, uid_t uid
, gid_t gid
, char *error
) {
76 switch(pid
= fork()) {
83 if (gid
&& setgid(gid
)) {
84 fprintf(stderr
, "%s: ", error
);
85 perror("Couldn't setgid");
89 if (uid
&& setuid(uid
)) {
90 fprintf(stderr
, "%s: ", error
);
91 perror("Couldn't setuid");
99 execve("/bin/sh", argv
, trusted_env
);
100 fprintf(stderr
, "%s: ", error
);
101 perror("execve failed");
105 default: /* parent */
107 if (waitpid(pid
, &status
, 0) == -1) {
118 /* General routine to initialise a setuid root program, and put the
119 * environment in a known state. Returns 1 on success, if initsetuid() returns
120 * 0 then you should exit(1) immediately, DON'T attempt to recover from the
122 int initsetuid(void) {
127 /* Prevent signal tricks by ignoring all except SIGKILL and SIGCHILD */
128 for (i
= 0; i
< NSIG
; i
++) {
129 if (i
!= SIGKILL
&& i
!= SIGCHLD
)
133 /* dump all non-standard file descriptors (a full descriptor table could
134 * lead to DoS by preventing us opening files) */
135 if ((fds
= getdtablesize()) == -1)
137 for (i
= 3; i
< fds
; i
++)
140 /* check stdin, stdout & stderr are open before going any further */
141 for (i
= 0; i
< 3; i
++)
142 if( fstat(i
, &st
) == -1 && ((errno
!= EBADF
) || (close(i
), open("/dev/null", O_RDWR
, 0)) != i
))
145 /* disable core dumps in case we're processing sensitive information */
146 rlim
.rlim_cur
= rlim
.rlim_max
= 0;
147 if (setrlimit(RLIMIT_CORE
, &rlim
)) {
148 perror("Couldn't disable core dumps");
152 /* drop any supplementary groups, set uid & gid to root */
153 if (setgroups(0, NULL
)) {
154 perror("Couldn't clear group list");
159 perror("Couldn't setgid(0)");
164 perror("Couldn't setuid(0)");