1 /* $Id: port-linux.c,v 1.11.4.3 2011/02/06 02:24:17 dtucker Exp $ */
4 * Copyright (c) 2005 Daniel Walsh <dwalsh@redhat.com>
5 * Copyright (c) 2006 Damien Miller <djm@openbsd.org>
7 * Permission to use, copy, modify, and distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
21 * Linux-specific portability code - just SELinux support at present
26 #if defined(WITH_SELINUX) || defined(LINUX_OOM_ADJUST)
34 #include "port-linux.h"
37 #include <selinux/selinux.h>
38 #include <selinux/flask.h>
39 #include <selinux/get_context_list.h>
41 /* Wrapper around is_selinux_enabled() to log its return value once only */
43 ssh_selinux_enabled(void)
45 static int enabled = -1;
48 enabled = (is_selinux_enabled() == 1);
49 debug("SELinux support %s", enabled ? "enabled" : "disabled");
55 /* Return the default security context for the given username */
56 static security_context_t
57 ssh_selinux_getctxbyname(char *pwname)
59 security_context_t sc;
60 char *sename = NULL, *lvl = NULL;
63 #ifdef HAVE_GETSEUSERBYNAME
64 if (getseuserbyname(pwname, &sename, &lvl) != 0)
71 #ifdef HAVE_GET_DEFAULT_CONTEXT_WITH_LEVEL
72 r = get_default_context_with_level(sename, lvl, NULL, &sc);
74 r = get_default_context(sename, NULL, &sc);
78 switch (security_getenforce()) {
80 fatal("%s: ssh_selinux_getctxbyname: "
81 "security_getenforce() failed", __func__);
83 error("%s: Failed to get default SELinux security "
84 "context for %s", __func__, pwname);
87 fatal("%s: Failed to get default SELinux security "
88 "context for %s (in enforcing mode)",
93 #ifdef HAVE_GETSEUSERBYNAME
103 /* Set the execution context to the default for the specified user */
105 ssh_selinux_setup_exec_context(char *pwname)
107 security_context_t user_ctx = NULL;
109 if (!ssh_selinux_enabled())
112 debug3("%s: setting execution context", __func__);
114 user_ctx = ssh_selinux_getctxbyname(pwname);
115 if (setexeccon(user_ctx) != 0) {
116 switch (security_getenforce()) {
118 fatal("%s: security_getenforce() failed", __func__);
120 error("%s: Failed to set SELinux execution "
121 "context for %s", __func__, pwname);
124 fatal("%s: Failed to set SELinux execution context "
125 "for %s (in enforcing mode)", __func__, pwname);
128 if (user_ctx != NULL)
131 debug3("%s: done", __func__);
134 /* Set the TTY context for the specified user */
136 ssh_selinux_setup_pty(char *pwname, const char *tty)
138 security_context_t new_tty_ctx = NULL;
139 security_context_t user_ctx = NULL;
140 security_context_t old_tty_ctx = NULL;
142 if (!ssh_selinux_enabled())
145 debug3("%s: setting TTY context on %s", __func__, tty);
147 user_ctx = ssh_selinux_getctxbyname(pwname);
149 /* XXX: should these calls fatal() upon failure in enforcing mode? */
151 if (getfilecon(tty, &old_tty_ctx) == -1) {
152 error("%s: getfilecon: %s", __func__, strerror(errno));
156 if (security_compute_relabel(user_ctx, old_tty_ctx,
157 SECCLASS_CHR_FILE, &new_tty_ctx) != 0) {
158 error("%s: security_compute_relabel: %s",
159 __func__, strerror(errno));
163 if (setfilecon(tty, new_tty_ctx) != 0)
164 error("%s: setfilecon: %s", __func__, strerror(errno));
166 if (new_tty_ctx != NULL)
167 freecon(new_tty_ctx);
168 if (old_tty_ctx != NULL)
169 freecon(old_tty_ctx);
170 if (user_ctx != NULL)
172 debug3("%s: done", __func__);
176 ssh_selinux_change_context(const char *newname)
179 char *oldctx, *newctx, *cx;
181 if (!ssh_selinux_enabled())
184 if (getcon((security_context_t *)&oldctx) < 0) {
185 logit("%s: getcon failed with %s", __func__, strerror (errno));
188 if ((cx = index(oldctx, ':')) == NULL || (cx = index(cx + 1, ':')) ==
190 logit ("%s: unparseable context %s", __func__, oldctx);
194 newlen = strlen(oldctx) + strlen(newname) + 1;
195 newctx = xmalloc(newlen);
196 len = cx - oldctx + 1;
197 memcpy(newctx, oldctx, len);
198 strlcpy(newctx + len, newname, newlen - len);
199 if ((cx = index(cx + 1, ':')))
200 strlcat(newctx, cx, newlen);
201 debug3("%s: setting context from '%s' to '%s'", __func__, oldctx,
203 if (setcon(newctx) < 0)
204 logit("%s: setcon failed with %s", __func__, strerror (errno));
210 ssh_selinux_setfscreatecon(const char *path)
212 security_context_t context;
214 if (!ssh_selinux_enabled())
217 setfscreatecon(NULL);
220 if (matchpathcon(path, 0700, &context) == 0)
221 setfscreatecon(context);
224 #endif /* WITH_SELINUX */
226 #ifdef LINUX_OOM_ADJUST
228 * The magic "don't kill me" values, old and new, as documented in eg:
229 * http://lxr.linux.no/#linux+v2.6.32/Documentation/filesystems/proc.txt
230 * http://lxr.linux.no/#linux+v2.6.36/Documentation/filesystems/proc.txt
233 static int oom_adj_save = INT_MIN;
234 static char *oom_adj_path = NULL;
239 {"/proc/self/oom_score_adj", -1000}, /* kernels >= 2.6.36 */
240 {"/proc/self/oom_adj", -17}, /* kernels <= 2.6.35 */
245 * Tell the kernel's out-of-memory killer to avoid sshd.
246 * Returns the previous oom_adj value or zero.
249 oom_adjust_setup(void)
254 debug3("%s", __func__);
255 for (i = 0; oom_adjust[i].path != NULL; i++) {
256 oom_adj_path = oom_adjust[i].path;
257 value = oom_adjust[i].value;
258 if ((fp = fopen(oom_adj_path, "r+")) != NULL) {
259 if (fscanf(fp, "%d", &oom_adj_save) != 1)
260 verbose("error reading %s: %s", oom_adj_path,
264 if (fprintf(fp, "%d\n", value) <= 0)
265 verbose("error writing %s: %s",
266 oom_adj_path, strerror(errno));
268 verbose("Set %s from %d to %d",
269 oom_adj_path, oom_adj_save, value);
278 /* Restore the saved OOM adjustment */
280 oom_adjust_restore(void)
284 debug3("%s", __func__);
285 if (oom_adj_save == INT_MIN || oom_adj_path == NULL ||
286 (fp = fopen(oom_adj_path, "w")) == NULL)
289 if (fprintf(fp, "%d\n", oom_adj_save) <= 0)
290 verbose("error writing %s: %s", oom_adj_path, strerror(errno));
292 verbose("Set %s to %d", oom_adj_path, oom_adj_save);
297 #endif /* LINUX_OOM_ADJUST */
298 #endif /* WITH_SELINUX || LINUX_OOM_ADJUST */