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/* $Id: port-linux.c,v 1.17 2012/03/08 23:25:18 djm Exp $ */
/*
* Copyright (c) 2005 Daniel Walsh <dwalsh@redhat.com>
* Copyright (c) 2006 Damien Miller <djm@openbsd.org>
*
* 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.
*/
/*
* Linux-specific portability code - just SELinux support at present
*/
#include "includes.h"
#if defined(WITH_SELINUX) || defined(LINUX_OOM_ADJUST)
#include <errno.h>
#include <stdarg.h>
#include <string.h>
#include <stdio.h>
#include "log.h"
#include "xmalloc.h"
#include "port-linux.h"
#ifdef WITH_SELINUX
#include <selinux/selinux.h>
#include <selinux/flask.h>
#include <selinux/get_context_list.h>
#ifndef SSH_SELINUX_UNCONFINED_TYPE
# define SSH_SELINUX_UNCONFINED_TYPE ":unconfined_t:"
#endif
/* Wrapper around is_selinux_enabled() to log its return value once only */
int
ssh_selinux_enabled(void)
{
static int enabled = -1;
if (enabled == -1) {
enabled = (is_selinux_enabled() == 1);
debug("SELinux support %s", enabled ? "enabled" : "disabled");
}
return (enabled);
}
/* Return the default security context for the given username */
static security_context_t
ssh_selinux_getctxbyname(char *pwname)
{
security_context_t sc = NULL;
char *sename = NULL, *lvl = NULL;
int r;
#ifdef HAVE_GETSEUSERBYNAME
if (getseuserbyname(pwname, &sename, &lvl) != 0)
return NULL;
#else
sename = pwname;
lvl = NULL;
#endif
#ifdef HAVE_GET_DEFAULT_CONTEXT_WITH_LEVEL
r = get_default_context_with_level(sename, lvl, NULL, &sc);
#else
r = get_default_context(sename, NULL, &sc);
#endif
if (r != 0) {
switch (security_getenforce()) {
case -1:
fatal("%s: ssh_selinux_getctxbyname: "
"security_getenforce() failed", __func__);
case 0:
error("%s: Failed to get default SELinux security "
"context for %s", __func__, pwname);
sc = NULL;
break;
default:
fatal("%s: Failed to get default SELinux security "
"context for %s (in enforcing mode)",
__func__, pwname);
}
}
#ifdef HAVE_GETSEUSERBYNAME
if (sename != NULL)
xfree(sename);
if (lvl != NULL)
xfree(lvl);
#endif
return sc;
}
/* Set the execution context to the default for the specified user */
void
ssh_selinux_setup_exec_context(char *pwname)
{
security_context_t user_ctx = NULL;
if (!ssh_selinux_enabled())
return;
debug3("%s: setting execution context", __func__);
user_ctx = ssh_selinux_getctxbyname(pwname);
if (setexeccon(user_ctx) != 0) {
switch (security_getenforce()) {
case -1:
fatal("%s: security_getenforce() failed", __func__);
case 0:
error("%s: Failed to set SELinux execution "
"context for %s", __func__, pwname);
break;
default:
fatal("%s: Failed to set SELinux execution context "
"for %s (in enforcing mode)", __func__, pwname);
}
}
if (user_ctx != NULL)
freecon(user_ctx);
debug3("%s: done", __func__);
}
/* Set the TTY context for the specified user */
void
ssh_selinux_setup_pty(char *pwname, const char *tty)
{
security_context_t new_tty_ctx = NULL;
security_context_t user_ctx = NULL;
security_context_t old_tty_ctx = NULL;
if (!ssh_selinux_enabled())
return;
debug3("%s: setting TTY context on %s", __func__, tty);
user_ctx = ssh_selinux_getctxbyname(pwname);
/* XXX: should these calls fatal() upon failure in enforcing mode? */
if (getfilecon(tty, &old_tty_ctx) == -1) {
error("%s: getfilecon: %s", __func__, strerror(errno));
goto out;
}
if (security_compute_relabel(user_ctx, old_tty_ctx,
SECCLASS_CHR_FILE, &new_tty_ctx) != 0) {
error("%s: security_compute_relabel: %s",
__func__, strerror(errno));
goto out;
}
if (setfilecon(tty, new_tty_ctx) != 0)
error("%s: setfilecon: %s", __func__, strerror(errno));
out:
if (new_tty_ctx != NULL)
freecon(new_tty_ctx);
if (old_tty_ctx != NULL)
freecon(old_tty_ctx);
if (user_ctx != NULL)
freecon(user_ctx);
debug3("%s: done", __func__);
}
void
ssh_selinux_change_context(const char *newname)
{
int len, newlen;
char *oldctx, *newctx, *cx;
void (*switchlog) (const char *fmt,...) = logit;
if (!ssh_selinux_enabled())
return;
if (getcon((security_context_t *)&oldctx) < 0) {
logit("%s: getcon failed with %s", __func__, strerror(errno));
return;
}
if ((cx = index(oldctx, ':')) == NULL || (cx = index(cx + 1, ':')) ==
NULL) {
logit ("%s: unparseable context %s", __func__, oldctx);
return;
}
/*
* Check whether we are attempting to switch away from an unconfined
* security context.
*/
if (strncmp(cx, SSH_SELINUX_UNCONFINED_TYPE,
sizeof(SSH_SELINUX_UNCONFINED_TYPE) - 1) == 0)
switchlog = debug3;
newlen = strlen(oldctx) + strlen(newname) + 1;
newctx = xmalloc(newlen);
len = cx - oldctx + 1;
memcpy(newctx, oldctx, len);
strlcpy(newctx + len, newname, newlen - len);
if ((cx = index(cx + 1, ':')))
strlcat(newctx, cx, newlen);
debug3("%s: setting context from '%s' to '%s'", __func__,
oldctx, newctx);
if (setcon(newctx) < 0)
switchlog("%s: setcon %s from %s failed with %s", __func__,
newctx, oldctx, strerror(errno));
xfree(oldctx);
xfree(newctx);
}
void
ssh_selinux_setfscreatecon(const char *path)
{
security_context_t context;
if (!ssh_selinux_enabled())
return;
if (path == NULL) {
setfscreatecon(NULL);
return;
}
if (matchpathcon(path, 0700, &context) == 0)
setfscreatecon(context);
}
#endif /* WITH_SELINUX */
#ifdef LINUX_OOM_ADJUST
/*
* The magic "don't kill me" values, old and new, as documented in eg:
* http://lxr.linux.no/#linux+v2.6.32/Documentation/filesystems/proc.txt
* http://lxr.linux.no/#linux+v2.6.36/Documentation/filesystems/proc.txt
*/
static int oom_adj_save = INT_MIN;
static char *oom_adj_path = NULL;
struct {
char *path;
int value;
} oom_adjust[] = {
{"/proc/self/oom_score_adj", -1000}, /* kernels >= 2.6.36 */
{"/proc/self/oom_adj", -17}, /* kernels <= 2.6.35 */
{NULL, 0},
};
/*
* Tell the kernel's out-of-memory killer to avoid sshd.
* Returns the previous oom_adj value or zero.
*/
void
oom_adjust_setup(void)
{
int i, value;
FILE *fp;
debug3("%s", __func__);
for (i = 0; oom_adjust[i].path != NULL; i++) {
oom_adj_path = oom_adjust[i].path;
value = oom_adjust[i].value;
if ((fp = fopen(oom_adj_path, "r+")) != NULL) {
if (fscanf(fp, "%d", &oom_adj_save) != 1)
verbose("error reading %s: %s", oom_adj_path,
strerror(errno));
else {
rewind(fp);
if (fprintf(fp, "%d\n", value) <= 0)
verbose("error writing %s: %s",
oom_adj_path, strerror(errno));
else
verbose("Set %s from %d to %d",
oom_adj_path, oom_adj_save, value);
}
fclose(fp);
return;
}
}
oom_adj_path = NULL;
}
/* Restore the saved OOM adjustment */
void
oom_adjust_restore(void)
{
FILE *fp;
debug3("%s", __func__);
if (oom_adj_save == INT_MIN || oom_adj_path == NULL ||
(fp = fopen(oom_adj_path, "w")) == NULL)
return;
if (fprintf(fp, "%d\n", oom_adj_save) <= 0)
verbose("error writing %s: %s", oom_adj_path, strerror(errno));
else
verbose("Set %s to %d", oom_adj_path, oom_adj_save);
fclose(fp);
return;
}
#endif /* LINUX_OOM_ADJUST */
#endif /* WITH_SELINUX || LINUX_OOM_ADJUST */