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 #include <errno.h> 26 #include <stdarg.h> 27 #include <string.h> 28 #include <stdio.h> 29 #include <stdlib.h> 30 31 #include "log.h" 32 #include "xmalloc.h" 33 #include "port-linux.h" 34 35 #ifdef WITH_SELINUX 36 #include <selinux/selinux.h> 37 #include <selinux/get_context_list.h> 38 39 #ifndef SSH_SELINUX_UNCONFINED_TYPE 40 # define SSH_SELINUX_UNCONFINED_TYPE ":unconfined_t:" 41 #endif 42 43 /* Wrapper around is_selinux_enabled() to log its return value once only */ 44 int 45 ssh_selinux_enabled(void) 46 { 47 static int enabled = -1; 48 49 if (enabled == -1) { 50 enabled = (is_selinux_enabled() == 1); 51 debug("SELinux support %s", enabled ? "enabled" : "disabled"); 52 } 53 54 return (enabled); 55 } 56 57 /* Return the default security context for the given username */ 58 static char * 59 ssh_selinux_getctxbyname(char *pwname) 60 { 61 char *sc = NULL, *sename = NULL, *lvl = NULL; 62 int r; 63 64 #ifdef HAVE_GETSEUSERBYNAME 65 if (getseuserbyname(pwname, &sename, &lvl) != 0) 66 return NULL; 67 #else 68 sename = pwname; 69 lvl = NULL; 70 #endif 71 72 #ifdef HAVE_GET_DEFAULT_CONTEXT_WITH_LEVEL 73 r = get_default_context_with_level(sename, lvl, NULL, &sc); 74 #else 75 r = get_default_context(sename, NULL, &sc); 76 #endif 77 78 if (r != 0) { 79 switch (security_getenforce()) { 80 case -1: 81 fatal("%s: ssh_selinux_getctxbyname: " 82 "security_getenforce() failed", __func__); 83 case 0: 84 error("%s: Failed to get default SELinux security " 85 "context for %s", __func__, pwname); 86 sc = NULL; 87 break; 88 default: 89 fatal("%s: Failed to get default SELinux security " 90 "context for %s (in enforcing mode)", 91 __func__, pwname); 92 } 93 } 94 95 #ifdef HAVE_GETSEUSERBYNAME 96 free(sename); 97 free(lvl); 98 #endif 99 100 return sc; 101 } 102 103 /* Set the execution context to the default for the specified user */ 104 void 105 ssh_selinux_setup_exec_context(char *pwname) 106 { 107 char *user_ctx = NULL; 108 109 if (!ssh_selinux_enabled()) 110 return; 111 112 debug3("%s: setting execution context", __func__); 113 114 user_ctx = ssh_selinux_getctxbyname(pwname); 115 if (setexeccon(user_ctx) != 0) { 116 switch (security_getenforce()) { 117 case -1: 118 fatal("%s: security_getenforce() failed", __func__); 119 case 0: 120 error("%s: Failed to set SELinux execution " 121 "context for %s", __func__, pwname); 122 break; 123 default: 124 fatal("%s: Failed to set SELinux execution context " 125 "for %s (in enforcing mode)", __func__, pwname); 126 } 127 } 128 if (user_ctx != NULL) 129 freecon(user_ctx); 130 131 debug3("%s: done", __func__); 132 } 133 134 /* Set the TTY context for the specified user */ 135 void 136 ssh_selinux_setup_pty(char *pwname, const char *tty) 137 { 138 char *new_tty_ctx = NULL, *user_ctx = NULL, *old_tty_ctx = NULL; 139 security_class_t chrclass; 140 141 if (!ssh_selinux_enabled()) 142 return; 143 144 debug3("%s: setting TTY context on %s", __func__, tty); 145 146 user_ctx = ssh_selinux_getctxbyname(pwname); 147 148 /* XXX: should these calls fatal() upon failure in enforcing mode? */ 149 150 if (getfilecon(tty, &old_tty_ctx) == -1) { 151 error("%s: getfilecon: %s", __func__, strerror(errno)); 152 goto out; 153 } 154 if ((chrclass = string_to_security_class("chr_file")) == 0) { 155 error("%s: couldn't get security class for chr_file", __func__); 156 goto out; 157 } 158 if (security_compute_relabel(user_ctx, old_tty_ctx, 159 chrclass, &new_tty_ctx) != 0) { 160 error("%s: security_compute_relabel: %s", 161 __func__, strerror(errno)); 162 goto out; 163 } 164 165 if (setfilecon(tty, new_tty_ctx) != 0) 166 error("%s: setfilecon: %s", __func__, strerror(errno)); 167 out: 168 if (new_tty_ctx != NULL) 169 freecon(new_tty_ctx); 170 if (old_tty_ctx != NULL) 171 freecon(old_tty_ctx); 172 if (user_ctx != NULL) 173 freecon(user_ctx); 174 debug3("%s: done", __func__); 175 } 176 177 void 178 ssh_selinux_change_context(const char *newname) 179 { 180 int len, newlen; 181 char *oldctx, *newctx, *cx; 182 LogLevel log_level = SYSLOG_LEVEL_INFO; 183 184 if (!ssh_selinux_enabled()) 185 return; 186 187 if (getcon(&oldctx) < 0) { 188 logit("%s: getcon failed with %s", __func__, strerror(errno)); 189 return; 190 } 191 if ((cx = index(oldctx, ':')) == NULL || (cx = index(cx + 1, ':')) == 192 NULL) { 193 logit("%s: unparsable context %s", __func__, oldctx); 194 return; 195 } 196 197 /* 198 * Check whether we are attempting to switch away from an unconfined 199 * security context. 200 */ 201 if (strncmp(cx, SSH_SELINUX_UNCONFINED_TYPE, 202 sizeof(SSH_SELINUX_UNCONFINED_TYPE) - 1) == 0) 203 log_level = SYSLOG_LEVEL_DEBUG3; 204 205 newlen = strlen(oldctx) + strlen(newname) + 1; 206 newctx = xmalloc(newlen); 207 len = cx - oldctx + 1; 208 memcpy(newctx, oldctx, len); 209 strlcpy(newctx + len, newname, newlen - len); 210 if ((cx = index(cx + 1, ':'))) 211 strlcat(newctx, cx, newlen); 212 debug3("%s: setting context from '%s' to '%s'", __func__, 213 oldctx, newctx); 214 if (setcon(newctx) < 0) 215 do_log2(log_level, "%s: setcon %s from %s failed with %s", 216 __func__, newctx, oldctx, strerror(errno)); 217 free(oldctx); 218 free(newctx); 219 } 220 221 void 222 ssh_selinux_setfscreatecon(const char *path) 223 { 224 char *context; 225 226 if (!ssh_selinux_enabled()) 227 return; 228 if (path == NULL) { 229 setfscreatecon(NULL); 230 return; 231 } 232 if (matchpathcon(path, 0700, &context) == 0) 233 setfscreatecon(context); 234 } 235 236 #endif /* WITH_SELINUX */ 237 238 #ifdef LINUX_OOM_ADJUST 239 /* 240 * The magic "don't kill me" values, old and new, as documented in eg: 241 * http://lxr.linux.no/#linux+v2.6.32/Documentation/filesystems/proc.txt 242 * http://lxr.linux.no/#linux+v2.6.36/Documentation/filesystems/proc.txt 243 */ 244 245 static int oom_adj_save = INT_MIN; 246 static char *oom_adj_path = NULL; 247 struct { 248 char *path; 249 int value; 250 } oom_adjust[] = { 251 {"/proc/self/oom_score_adj", -1000}, /* kernels >= 2.6.36 */ 252 {"/proc/self/oom_adj", -17}, /* kernels <= 2.6.35 */ 253 {NULL, 0}, 254 }; 255 256 /* 257 * Tell the kernel's out-of-memory killer to avoid sshd. 258 * Returns the previous oom_adj value or zero. 259 */ 260 void 261 oom_adjust_setup(void) 262 { 263 int i, value; 264 FILE *fp; 265 266 debug3("%s", __func__); 267 for (i = 0; oom_adjust[i].path != NULL; i++) { 268 oom_adj_path = oom_adjust[i].path; 269 value = oom_adjust[i].value; 270 if ((fp = fopen(oom_adj_path, "r+")) != NULL) { 271 if (fscanf(fp, "%d", &oom_adj_save) != 1) 272 verbose("error reading %s: %s", oom_adj_path, 273 strerror(errno)); 274 else { 275 rewind(fp); 276 if (fprintf(fp, "%d\n", value) <= 0) 277 verbose("error writing %s: %s", 278 oom_adj_path, strerror(errno)); 279 else 280 debug("Set %s from %d to %d", 281 oom_adj_path, oom_adj_save, value); 282 } 283 fclose(fp); 284 return; 285 } 286 } 287 oom_adj_path = NULL; 288 } 289 290 /* Restore the saved OOM adjustment */ 291 void 292 oom_adjust_restore(void) 293 { 294 FILE *fp; 295 296 debug3("%s", __func__); 297 if (oom_adj_save == INT_MIN || oom_adj_path == NULL || 298 (fp = fopen(oom_adj_path, "w")) == NULL) 299 return; 300 301 if (fprintf(fp, "%d\n", oom_adj_save) <= 0) 302 verbose("error writing %s: %s", oom_adj_path, strerror(errno)); 303 else 304 debug("Set %s to %d", oom_adj_path, oom_adj_save); 305 306 fclose(fp); 307 return; 308 } 309 #endif /* LINUX_OOM_ADJUST */ 310 #endif /* WITH_SELINUX || LINUX_OOM_ADJUST */ 311