1 /*
2 * Copyright (c) 2005 Daniel Walsh <dwalsh@redhat.com>
3 * Copyright (c) 2006 Damien Miller <djm@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18 /*
19 * Linux-specific portability code - just SELinux support at present
20 */
21
22 #include "includes.h"
23
24 #if defined(WITH_SELINUX) || defined(LINUX_OOM_ADJUST) || \
25 defined(SYSTEMD_NOTIFY)
26 #include <sys/socket.h>
27 #include <sys/un.h>
28
29 #include <errno.h>
30 #include <inttypes.h>
31 #include <stdarg.h>
32 #include <string.h>
33 #include <stdio.h>
34 #include <stdlib.h>
35 #include <time.h>
36 #include <unistd.h>
37
38 #include "log.h"
39 #include "xmalloc.h"
40 #include "port-linux.h"
41 #include "misc.h"
42
43 #ifdef WITH_SELINUX
44 #include <selinux/selinux.h>
45 #include <selinux/label.h>
46 #include <selinux/get_context_list.h>
47
48 #ifndef SSH_SELINUX_UNCONFINED_TYPE
49 # define SSH_SELINUX_UNCONFINED_TYPE ":unconfined_t:"
50 #endif
51
52 /* Wrapper around is_selinux_enabled() to log its return value once only */
53 int
ssh_selinux_enabled(void)54 ssh_selinux_enabled(void)
55 {
56 static int enabled = -1;
57
58 if (enabled == -1) {
59 enabled = (is_selinux_enabled() == 1);
60 debug("SELinux support %s", enabled ? "enabled" : "disabled");
61 }
62
63 return (enabled);
64 }
65
66 /* Return the default security context for the given username */
67 static char *
ssh_selinux_getctxbyname(char * pwname)68 ssh_selinux_getctxbyname(char *pwname)
69 {
70 char *sc = NULL, *sename = NULL, *lvl = NULL;
71 int r;
72
73 #ifdef HAVE_GETSEUSERBYNAME
74 if (getseuserbyname(pwname, &sename, &lvl) != 0)
75 return NULL;
76 #else
77 sename = pwname;
78 lvl = NULL;
79 #endif
80
81 #ifdef HAVE_GET_DEFAULT_CONTEXT_WITH_LEVEL
82 r = get_default_context_with_level(sename, lvl, NULL, &sc);
83 #else
84 r = get_default_context(sename, NULL, &sc);
85 #endif
86
87 if (r != 0) {
88 switch (security_getenforce()) {
89 case -1:
90 fatal("%s: ssh_selinux_getctxbyname: "
91 "security_getenforce() failed", __func__);
92 case 0:
93 error("%s: Failed to get default SELinux security "
94 "context for %s", __func__, pwname);
95 sc = NULL;
96 break;
97 default:
98 fatal("%s: Failed to get default SELinux security "
99 "context for %s (in enforcing mode)",
100 __func__, pwname);
101 }
102 }
103
104 #ifdef HAVE_GETSEUSERBYNAME
105 free(sename);
106 free(lvl);
107 #endif
108
109 return sc;
110 }
111
112 /* Set the execution context to the default for the specified user */
113 void
ssh_selinux_setup_exec_context(char * pwname)114 ssh_selinux_setup_exec_context(char *pwname)
115 {
116 char *user_ctx = NULL;
117
118 if (!ssh_selinux_enabled())
119 return;
120
121 debug3("%s: setting execution context", __func__);
122
123 user_ctx = ssh_selinux_getctxbyname(pwname);
124 if (setexeccon(user_ctx) != 0) {
125 switch (security_getenforce()) {
126 case -1:
127 fatal("%s: security_getenforce() failed", __func__);
128 case 0:
129 error("%s: Failed to set SELinux execution "
130 "context for %s", __func__, pwname);
131 break;
132 default:
133 fatal("%s: Failed to set SELinux execution context "
134 "for %s (in enforcing mode)", __func__, pwname);
135 }
136 }
137 if (user_ctx != NULL)
138 freecon(user_ctx);
139
140 debug3("%s: done", __func__);
141 }
142
143 /* Set the TTY context for the specified user */
144 void
ssh_selinux_setup_pty(char * pwname,const char * tty)145 ssh_selinux_setup_pty(char *pwname, const char *tty)
146 {
147 char *new_tty_ctx = NULL, *user_ctx = NULL, *old_tty_ctx = NULL;
148 security_class_t chrclass;
149
150 if (!ssh_selinux_enabled())
151 return;
152
153 debug3("%s: setting TTY context on %s", __func__, tty);
154
155 user_ctx = ssh_selinux_getctxbyname(pwname);
156
157 /* XXX: should these calls fatal() upon failure in enforcing mode? */
158
159 if (getfilecon(tty, &old_tty_ctx) == -1) {
160 error("%s: getfilecon: %s", __func__, strerror(errno));
161 goto out;
162 }
163 if ((chrclass = string_to_security_class("chr_file")) == 0) {
164 error("%s: couldn't get security class for chr_file", __func__);
165 goto out;
166 }
167 if (security_compute_relabel(user_ctx, old_tty_ctx,
168 chrclass, &new_tty_ctx) != 0) {
169 error("%s: security_compute_relabel: %s",
170 __func__, strerror(errno));
171 goto out;
172 }
173
174 if (setfilecon(tty, new_tty_ctx) != 0)
175 error("%s: setfilecon: %s", __func__, strerror(errno));
176 out:
177 if (new_tty_ctx != NULL)
178 freecon(new_tty_ctx);
179 if (old_tty_ctx != NULL)
180 freecon(old_tty_ctx);
181 if (user_ctx != NULL)
182 freecon(user_ctx);
183 debug3("%s: done", __func__);
184 }
185
186 void
ssh_selinux_change_context(const char * newname)187 ssh_selinux_change_context(const char *newname)
188 {
189 char *oldctx, *newctx, *cx, *cx2;
190 LogLevel log_level = SYSLOG_LEVEL_INFO;
191
192 if (!ssh_selinux_enabled())
193 return;
194
195 if (getcon(&oldctx) < 0) {
196 logit_f("getcon failed with %s", strerror(errno));
197 return;
198 }
199 if ((cx = strchr(oldctx, ':')) == NULL ||
200 (cx = strchr(cx + 1, ':')) == NULL ||
201 (cx - oldctx) >= INT_MAX) {
202 logit_f("unparsable context %s", oldctx);
203 return;
204 }
205
206 /*
207 * Check whether we are attempting to switch away from an unconfined
208 * security context.
209 */
210 if (strncmp(cx, SSH_SELINUX_UNCONFINED_TYPE,
211 sizeof(SSH_SELINUX_UNCONFINED_TYPE) - 1) == 0)
212 log_level = SYSLOG_LEVEL_DEBUG3;
213
214 cx2 = strchr(cx + 1, ':');
215 xasprintf(&newctx, "%.*s%s%s", (int)(cx - oldctx + 1), oldctx,
216 newname, cx2 == NULL ? "" : cx2);
217
218 debug3_f("setting context from '%s' to '%s'", oldctx, newctx);
219 if (setcon(newctx) < 0)
220 do_log2_f(log_level, "setcon %s from %s failed with %s",
221 newctx, oldctx, strerror(errno));
222 free(oldctx);
223 free(newctx);
224 }
225
226 void
ssh_selinux_setfscreatecon(const char * path)227 ssh_selinux_setfscreatecon(const char *path)
228 {
229 char *context;
230 struct selabel_handle *shandle = NULL;
231
232 if (!ssh_selinux_enabled())
233 return;
234 if (path == NULL) {
235 setfscreatecon(NULL);
236 return;
237 }
238 if ((shandle = selabel_open(SELABEL_CTX_FILE, NULL, 0)) == NULL) {
239 debug_f("selabel_open failed");
240 return;
241 }
242 if (selabel_lookup(shandle, &context, path, 0700) == 0)
243 setfscreatecon(context);
244 selabel_close(shandle);
245 }
246
247 #endif /* WITH_SELINUX */
248
249 #ifdef LINUX_OOM_ADJUST
250 /*
251 * The magic "don't kill me" values, old and new, as documented in eg:
252 * http://lxr.linux.no/#linux+v2.6.32/Documentation/filesystems/proc.txt
253 * http://lxr.linux.no/#linux+v2.6.36/Documentation/filesystems/proc.txt
254 */
255
256 static int oom_adj_save = INT_MIN;
257 static char *oom_adj_path = NULL;
258 struct {
259 char *path;
260 int value;
261 } oom_adjust[] = {
262 {"/proc/self/oom_score_adj", -1000}, /* kernels >= 2.6.36 */
263 {"/proc/self/oom_adj", -17}, /* kernels <= 2.6.35 */
264 {NULL, 0},
265 };
266
267 /*
268 * Tell the kernel's out-of-memory killer to avoid sshd.
269 * Returns the previous oom_adj value or zero.
270 */
271 void
oom_adjust_setup(void)272 oom_adjust_setup(void)
273 {
274 int i, value;
275 FILE *fp;
276
277 debug3("%s", __func__);
278 for (i = 0; oom_adjust[i].path != NULL; i++) {
279 oom_adj_path = oom_adjust[i].path;
280 value = oom_adjust[i].value;
281 if ((fp = fopen(oom_adj_path, "r+")) != NULL) {
282 if (fscanf(fp, "%d", &oom_adj_save) != 1)
283 verbose("error reading %s: %s", oom_adj_path,
284 strerror(errno));
285 else {
286 rewind(fp);
287 if (fprintf(fp, "%d\n", value) <= 0)
288 verbose("error writing %s: %s",
289 oom_adj_path, strerror(errno));
290 else
291 debug("Set %s from %d to %d",
292 oom_adj_path, oom_adj_save, value);
293 }
294 fclose(fp);
295 return;
296 }
297 }
298 oom_adj_path = NULL;
299 }
300
301 /* Restore the saved OOM adjustment */
302 void
oom_adjust_restore(void)303 oom_adjust_restore(void)
304 {
305 FILE *fp;
306
307 debug3("%s", __func__);
308 if (oom_adj_save == INT_MIN || oom_adj_path == NULL ||
309 (fp = fopen(oom_adj_path, "w")) == NULL)
310 return;
311
312 if (fprintf(fp, "%d\n", oom_adj_save) <= 0)
313 verbose("error writing %s: %s", oom_adj_path, strerror(errno));
314 else
315 debug("Set %s to %d", oom_adj_path, oom_adj_save);
316
317 fclose(fp);
318 return;
319 }
320 #endif /* LINUX_OOM_ADJUST */
321
322 #ifdef SYSTEMD_NOTIFY
323
324 static void ssh_systemd_notify(const char *, ...)
325 __attribute__((__format__ (printf, 1, 2))) __attribute__((__nonnull__ (1)));
326
327 static void
ssh_systemd_notify(const char * fmt,...)328 ssh_systemd_notify(const char *fmt, ...)
329 {
330 char *s = NULL;
331 const char *path;
332 struct stat sb;
333 struct sockaddr_un addr;
334 int fd = -1;
335 va_list ap;
336
337 if ((path = getenv("NOTIFY_SOCKET")) == NULL || strlen(path) == 0)
338 return;
339
340 va_start(ap, fmt);
341 xvasprintf(&s, fmt, ap);
342 va_end(ap);
343
344 /* Only AF_UNIX is supported, with path or abstract sockets */
345 if (path[0] != '/' && path[0] != '@') {
346 error_f("socket \"%s\" is not compatible with AF_UNIX", path);
347 goto out;
348 }
349
350 if (path[0] == '/' && stat(path, &sb) != 0) {
351 error_f("socket \"%s\" stat: %s", path, strerror(errno));
352 goto out;
353 }
354
355 memset(&addr, 0, sizeof(addr));
356 addr.sun_family = AF_UNIX;
357 if (strlcpy(addr.sun_path, path,
358 sizeof(addr.sun_path)) >= sizeof(addr.sun_path)) {
359 error_f("socket path \"%s\" too long", path);
360 goto out;
361 }
362 /* Support for abstract socket */
363 if (addr.sun_path[0] == '@')
364 addr.sun_path[0] = 0;
365 if ((fd = socket(PF_UNIX, SOCK_DGRAM, 0)) == -1) {
366 error_f("socket \"%s\": %s", path, strerror(errno));
367 goto out;
368 }
369 if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) != 0) {
370 error_f("socket \"%s\" connect: %s", path, strerror(errno));
371 goto out;
372 }
373 if (write(fd, s, strlen(s)) != (ssize_t)strlen(s)) {
374 error_f("socket \"%s\" write: %s", path, strerror(errno));
375 goto out;
376 }
377 debug_f("socket \"%s\" notified %s", path, s);
378 out:
379 if (fd != -1)
380 close(fd);
381 free(s);
382 }
383
384 void
ssh_systemd_notify_ready(void)385 ssh_systemd_notify_ready(void)
386 {
387 ssh_systemd_notify("READY=1");
388 }
389
390 void
ssh_systemd_notify_reload(void)391 ssh_systemd_notify_reload(void)
392 {
393 struct timespec now;
394
395 monotime_ts(&now);
396 if (now.tv_sec < 0 || now.tv_nsec < 0) {
397 error_f("monotime returned negative value");
398 ssh_systemd_notify("RELOADING=1");
399 } else {
400 ssh_systemd_notify("RELOADING=1\nMONOTONIC_USEC=%llu",
401 ((uint64_t)now.tv_sec * 1000000ULL) +
402 ((uint64_t)now.tv_nsec / 1000ULL));
403 }
404 }
405 #endif /* SYSTEMD_NOTIFY */
406
407 #endif /* WITH_SELINUX || LINUX_OOM_ADJUST || SYSTEMD_NOTIFY */
408