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/*
* Copyright (c) 2009-2010 Todd C. Miller <Todd.Miller@courtesan.com>
* Copyright (c) 2008 Dan Walsh <dwalsh@redhat.com>
*
* Borrowed heavily from newrole source code
* Authors:
* Anthony Colatrella
* Tim Fraser
* Steve Grubb <sgrubb@redhat.com>
* Darrel Goeddel <DGoeddel@trustedcs.com>
* Michael Thompson <mcthomps@us.ibm.com>
* Dan Walsh <dwalsh@redhat.com>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <config.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <selinux/flask.h> /* for SECCLASS_CHR_FILE */
#include <selinux/selinux.h> /* for is_selinux_enabled() */
#include <selinux/context.h> /* for context-mangling functions */
#include <selinux/get_default_type.h>
#include <selinux/get_context_list.h>
#ifdef HAVE_LINUX_AUDIT
# include <libaudit.h>
#endif
#include "sudo.h"
#include "sudo_exec.h"
static struct selinux_state {
security_context_t old_context;
security_context_t new_context;
security_context_t tty_context;
security_context_t new_tty_context;
const char *ttyn;
int ttyfd;
int enforcing;
} se_state;
#ifdef HAVE_LINUX_AUDIT
static int
audit_role_change(const security_context_t old_context,
const security_context_t new_context, const char *ttyn)
{
int au_fd, rc = -1;
char *message;
debug_decl(audit_role_change, SUDO_DEBUG_SELINUX)
au_fd = audit_open();
if (au_fd == -1) {
/* Kernel may not have audit support. */
if (errno != EINVAL && errno != EPROTONOSUPPORT && errno != EAFNOSUPPORT
)
error(1, _("unable to open audit system"));
} else {
/* audit role change using the same format as newrole(1) */
easprintf(&message, "newrole: old-context=%s new-context=%s",
old_context, new_context);
rc = audit_log_user_message(au_fd, AUDIT_USER_ROLE_CHANGE,
message, NULL, NULL, ttyn, 1);
if (rc <= 0)
warning(_("unable to send audit message"));
efree(message);
close(au_fd);
}
debug_return_int(rc);
}
#endif
/*
* This function attempts to revert the relabeling done to the tty.
* fd - referencing the opened ttyn
* ttyn - name of tty to restore
*
* Returns zero on success, non-zero otherwise
*/
int
selinux_restore_tty(void)
{
int retval = 0;
security_context_t chk_tty_context = NULL;
debug_decl(selinux_restore_tty, SUDO_DEBUG_SELINUX)
if (se_state.ttyfd == -1 || se_state.new_tty_context == NULL)
goto skip_relabel;
/* Verify that the tty still has the context set by sudo. */
if ((retval = fgetfilecon(se_state.ttyfd, &chk_tty_context)) < 0) {
warning(_("unable to fgetfilecon %s"), se_state.ttyn);
goto skip_relabel;
}
if ((retval = strcmp(chk_tty_context, se_state.new_tty_context))) {
warningx(_("%s changed labels"), se_state.ttyn);
goto skip_relabel;
}
if ((retval = fsetfilecon(se_state.ttyfd, se_state.tty_context)) < 0)
warning(_("unable to restore context for %s"), se_state.ttyn);
skip_relabel:
if (se_state.ttyfd != -1) {
close(se_state.ttyfd);
se_state.ttyfd = -1;
}
if (chk_tty_context != NULL) {
freecon(chk_tty_context);
chk_tty_context = NULL;
}
debug_return_int(retval);
}
/*
* This function attempts to relabel the tty. If this function fails, then
* the contexts are free'd and -1 is returned. On success, 0 is returned
* and tty_context and new_tty_context are set.
*
* This function will not fail if it can not relabel the tty when selinux is
* in permissive mode.
*/
static int
relabel_tty(const char *ttyn, int ptyfd)
{
security_context_t tty_con = NULL;
security_context_t new_tty_con = NULL;
int fd;
debug_decl(relabel_tty, SUDO_DEBUG_SELINUX)
se_state.ttyfd = ptyfd;
/* It is perfectly legal to have no tty. */
if (ptyfd == -1 && ttyn == NULL)
debug_return_int(0);
/* If sudo is not allocating a pty for the command, open current tty. */
if (ptyfd == -1) {
se_state.ttyfd = open(ttyn, O_RDWR|O_NONBLOCK);
if (se_state.ttyfd == -1) {
warning(_("unable to open %s, not relabeling tty"), ttyn);
if (se_state.enforcing)
goto bad;
}
(void)fcntl(se_state.ttyfd, F_SETFL,
fcntl(se_state.ttyfd, F_GETFL, 0) & ~O_NONBLOCK);
}
if (fgetfilecon(se_state.ttyfd, &tty_con) < 0) {
warning(_("unable to get current tty context, not relabeling tty"));
if (se_state.enforcing)
goto bad;
}
if (tty_con && (security_compute_relabel(se_state.new_context, tty_con,
SECCLASS_CHR_FILE, &new_tty_con) < 0)) {
warning(_("unable to get new tty context, not relabeling tty"));
if (se_state.enforcing)
goto bad;
}
if (new_tty_con != NULL) {
if (fsetfilecon(se_state.ttyfd, new_tty_con) < 0) {
warning(_("unable to set new tty context"));
if (se_state.enforcing)
goto bad;
}
}
if (ptyfd != -1) {
/* Reopen pty that was relabeled, std{in,out,err} are reset later. */
se_state.ttyfd = open(ttyn, O_RDWR|O_NOCTTY, 0);
if (se_state.ttyfd == -1) {
warning(_("unable to open %s"), ttyn);
if (se_state.enforcing)
goto bad;
}
if (dup2(se_state.ttyfd, ptyfd) == -1) {
warning("dup2");
goto bad;
}
} else {
/* Re-open tty to get new label and reset std{in,out,err} */
close(se_state.ttyfd);
se_state.ttyfd = open(ttyn, O_RDWR|O_NONBLOCK);
if (se_state.ttyfd == -1) {
warning(_("unable to open %s"), ttyn);
goto bad;
}
(void)fcntl(se_state.ttyfd, F_SETFL,
fcntl(se_state.ttyfd, F_GETFL, 0) & ~O_NONBLOCK);
for (fd = STDIN_FILENO; fd <= STDERR_FILENO; fd++) {
if (isatty(fd) && dup2(se_state.ttyfd, fd) == -1) {
warning("dup2");
goto bad;
}
}
}
/* Retain se_state.ttyfd so we can restore label when command finishes. */
(void)fcntl(se_state.ttyfd, F_SETFD, FD_CLOEXEC);
se_state.ttyn = ttyn;
se_state.tty_context = tty_con;
se_state.new_tty_context = new_tty_con;
debug_return_int(0);
bad:
if (se_state.ttyfd != -1 && se_state.ttyfd != ptyfd) {
close(se_state.ttyfd);
se_state.ttyfd = -1;
}
freecon(tty_con);
debug_return_int(-1);
}
/*
* Returns a new security context based on the old context and the
* specified role and type.
*/
security_context_t
get_exec_context(security_context_t old_context, const char *role, const char *type)
{
security_context_t new_context = NULL;
context_t context = NULL;
char *typebuf = NULL;
debug_decl(get_exec_context, SUDO_DEBUG_SELINUX)
/* We must have a role, the type is optional (we can use the default). */
if (!role) {
warningx(_("you must specify a role for type %s"), type);
errno = EINVAL;
goto bad;
}
if (!type) {
if (get_default_type(role, &typebuf)) {
warningx(_("unable to get default type for role %s"), role);
errno = EINVAL;
goto bad;
}
type = typebuf;
}
/*
* Expand old_context into a context_t so that we extract and modify
* its components easily.
*/
context = context_new(old_context);
/*
* Replace the role and type in "context" with the role and
* type we will be running the command as.
*/
if (context_role_set(context, role)) {
warning(_("failed to set new role %s"), role);
goto bad;
}
if (context_type_set(context, type)) {
warning(_("failed to set new type %s"), type);
goto bad;
}
/*
* Convert "context" back into a string and verify it.
*/
new_context = estrdup(context_str(context));
if (security_check_context(new_context) < 0) {
warningx(_("%s is not a valid context"), new_context);
errno = EINVAL;
goto bad;
}
#ifdef DEBUG
warningx("Your new context is %s", new_context);
#endif
context_free(context);
debug_return_ptr(new_context);
bad:
efree(typebuf);
context_free(context);
freecon(new_context);
debug_return_ptr(NULL);
}
/*
* Set the exec and tty contexts in preparation for fork/exec.
* Must run as root, before the uid change.
* If ptyfd is not -1, it indicates we are running
* in a pty and do not need to reset std{in,out,err}.
* Returns 0 on success and -1 on failure.
*/
int
selinux_setup(const char *role, const char *type, const char *ttyn,
int ptyfd)
{
int rval = -1;
debug_decl(selinux_setup, SUDO_DEBUG_SELINUX)
/* Store the caller's SID in old_context. */
if (getprevcon(&se_state.old_context)) {
warning(_("failed to get old_context"));
goto done;
}
se_state.enforcing = security_getenforce();
if (se_state.enforcing < 0) {
warning(_("unable to determine enforcing mode."));
goto done;
}
#ifdef DEBUG
warningx("your old context was %s", se_state.old_context);
#endif
se_state.new_context = get_exec_context(se_state.old_context, role, type);
if (!se_state.new_context)
goto done;
if (relabel_tty(ttyn, ptyfd) < 0) {
warning(_("unable to setup tty context for %s"), se_state.new_context);
goto done;
}
#ifdef DEBUG
if (se_state.ttyfd != -1) {
warningx("your old tty context is %s", se_state.tty_context);
warningx("your new tty context is %s", se_state.new_tty_context);
}
#endif
#ifdef HAVE_LINUX_AUDIT
audit_role_change(se_state.old_context, se_state.new_context,
se_state.ttyn);
#endif
rval = 0;
done:
debug_return_int(rval);
}
void
selinux_execve(const char *path, char *const argv[], char *const envp[],
int noexec)
{
char **nargv;
int argc, serrno;
debug_decl(selinux_execve, SUDO_DEBUG_SELINUX)
if (setexeccon(se_state.new_context)) {
warning(_("unable to set exec context to %s"), se_state.new_context);
if (se_state.enforcing)
debug_return;
}
#ifdef HAVE_SETKEYCREATECON
if (setkeycreatecon(se_state.new_context)) {
warning(_("unable to set key creation context to %s"), se_state.new_context);
if (se_state.enforcing)
debug_return;
}
#endif /* HAVE_SETKEYCREATECON */
/*
* Build new argv with sesh as argv[0].
* If argv[0] ends in -noexec, sesh will disable execute
* for the command it runs.
*/
for (argc = 0; argv[argc] != NULL; argc++)
continue;
nargv = emalloc2(argc + 2, sizeof(char *));
if (noexec)
nargv[0] = *argv[0] == '-' ? "-sesh-noexec" : "sesh-noexec";
else
nargv[0] = *argv[0] == '-' ? "-sesh" : "sesh";
nargv[1] = (char *)path;
memcpy(&nargv[2], &argv[1], argc * sizeof(char *)); /* copies NULL */
/* sesh will handle noexec for us. */
sudo_execve(_PATH_SUDO_SESH, nargv, envp, 0);
serrno = errno;
free(nargv);
errno = serrno;
debug_return;
}
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