1 /* 2 * Copyright (c) 2005 Daniel Walsh <dwalsh (at) redhat.com> 3 * Copyright (c) 2006 Damien Miller <djm (at) 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 30 #include "log.h" 31 #include "xmalloc.h" 32 #include "port-linux.h" 33 34 #ifdef WITH_SELINUX 35 #include <selinux/selinux.h> 36 #include <selinux/flask.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 security_context_t 59 ssh_selinux_getctxbyname(char *pwname) 60 { 61 security_context_t sc = NULL; 62 char *sename = NULL, *lvl = NULL; 63 int r; 64 65 #ifdef HAVE_GETSEUSERBYNAME 66 if (getseuserbyname(pwname, &sename, &lvl) != 0) 67 return NULL; 68 #else 69 sename = pwname; 70 lvl = NULL; 71 #endif 72 73 #ifdef HAVE_GET_DEFAULT_CONTEXT_WITH_LEVEL 74 r = get_default_context_with_level(sename, lvl, NULL, &sc); 75 #else 76 r = get_default_context(sename, NULL, &sc); 77 #endif 78 79 if (r != 0) { 80 switch (security_getenforce()) { 81 case -1: 82 fatal("%s: ssh_selinux_getctxbyname: " 83 "security_getenforce() failed", __func__); 84 case 0: 85 error("%s: Failed to get default SELinux security " 86 "context for %s", __func__, pwname); 87 sc = NULL; 88 break; 89 default: 90 fatal("%s: Failed to get default SELinux security " 91 "context for %s (in enforcing mode)", 92 __func__, pwname); 93 } 94 } 95 96 #ifdef HAVE_GETSEUSERBYNAME 97 free(sename); 98 free(lvl); 99 #endif 100 101 return sc; 102 } 103 104 /* Set the execution context to the default for the specified user */ 105 void 106 ssh_selinux_setup_exec_context(char *pwname) 107 { 108 security_context_t user_ctx = NULL; 109 110 if (!ssh_selinux_enabled()) 111 return; 112 113 debug3("%s: setting execution context", __func__); 114 115 user_ctx = ssh_selinux_getctxbyname(pwname); 116 if (setexeccon(user_ctx) != 0) { 117 switch (security_getenforce()) { 118 case -1: 119 fatal("%s: security_getenforce() failed", __func__); 120 case 0: 121 error("%s: Failed to set SELinux execution " 122 "context for %s", __func__, pwname); 123 break; 124 default: 125 fatal("%s: Failed to set SELinux execution context " 126 "for %s (in enforcing mode)", __func__, pwname); 127 } 128 } 129 if (user_ctx != NULL) 130 freecon(user_ctx); 131 132 debug3("%s: done", __func__); 133 } 134 135 /* Set the TTY context for the specified user */ 136 void 137 ssh_selinux_setup_pty(char *pwname, const char *tty) 138 { 139 security_context_t new_tty_ctx = NULL; 140 security_context_t user_ctx = NULL; 141 security_context_t old_tty_ctx = NULL; 142 143 if (!ssh_selinux_enabled()) 144 return; 145 146 debug3("%s: setting TTY context on %s", __func__, tty); 147 148 user_ctx = ssh_selinux_getctxbyname(pwname); 149 150 /* XXX: should these calls fatal() upon failure in enforcing mode? */ 151 152 if (getfilecon(tty, &old_tty_ctx) == -1) { 153 error("%s: getfilecon: %s", __func__, strerror(errno)); 154 goto out; 155 } 156 157 if (security_compute_relabel(user_ctx, old_tty_ctx, 158 SECCLASS_CHR_FILE, &new_tty_ctx) != 0) { 159 error("%s: security_compute_relabel: %s", 160 __func__, strerror(errno)); 161 goto out; 162 } 163 164 if (setfilecon(tty, new_tty_ctx) != 0) 165 error("%s: setfilecon: %s", __func__, strerror(errno)); 166 out: 167 if (new_tty_ctx != NULL) 168 freecon(new_tty_ctx); 169 if (old_tty_ctx != NULL) 170 freecon(old_tty_ctx); 171 if (user_ctx != NULL) 172 freecon(user_ctx); 173 debug3("%s: done", __func__); 174 } 175 176 void 177 ssh_selinux_change_context(const char *newname) 178 { 179 int len, newlen; 180 char *oldctx, *newctx, *cx; 181 void (*switchlog) (const char *fmt,...) = logit; 182 183 if (!ssh_selinux_enabled()) 184 return; 185 186 if (getcon((security_context_t *)&oldctx) < 0) { 187 logit("%s: getcon failed with %s", __func__, strerror(errno)); 188 return; 189 } 190 if ((cx = index(oldctx, ':')) == NULL || (cx = index(cx + 1, ':')) == 191 NULL) { 192 logit ("%s: unparseable context %s", __func__, oldctx); 193 return; 194 } 195 196 /* 197 * Check whether we are attempting to switch away from an unconfined 198 * security context. 199 */ 200 if (strncmp(cx, SSH_SELINUX_UNCONFINED_TYPE, 201 sizeof(SSH_SELINUX_UNCONFINED_TYPE) - 1) == 0) 202 switchlog = debug3; 203 204 newlen = strlen(oldctx) + strlen(newname) + 1; 205 newctx = xmalloc(newlen); 206 len = cx - oldctx + 1; 207 memcpy(newctx, oldctx, len); 208 strlcpy(newctx + len, newname, newlen - len); 209 if ((cx = index(cx + 1, ':'))) 210 strlcat(newctx, cx, newlen); 211 debug3("%s: setting context from '%s' to '%s'", __func__, 212 oldctx, newctx); 213 if (setcon(newctx) < 0) 214 switchlog("%s: setcon %s from %s failed with %s", __func__, 215 newctx, oldctx, strerror(errno)); 216 free(oldctx); 217 free(newctx); 218 } 219 220 void 221 ssh_selinux_setfscreatecon(const char *path) 222 { 223 security_context_t context; 224 225 if (!ssh_selinux_enabled()) 226 return; 227 if (path == NULL) { 228 setfscreatecon(NULL); 229 return; 230 } 231 if (matchpathcon(path, 0700, &context) == 0) 232 setfscreatecon(context); 233 } 234 235 #endif /* WITH_SELINUX */ 236 237 #ifdef LINUX_OOM_ADJUST 238 /* 239 * The magic "don't kill me" values, old and new, as documented in eg: 240 * http://lxr.linux.no/#linux+v2.6.32/Documentation/filesystems/proc.txt 241 * http://lxr.linux.no/#linux+v2.6.36/Documentation/filesystems/proc.txt 242 */ 243 244 static int oom_adj_save = INT_MIN; 245 static char *oom_adj_path = NULL; 246 struct { 247 char *path; 248 int value; 249 } oom_adjust[] = { 250 {"/proc/self/oom_score_adj", -1000}, /* kernels >= 2.6.36 */ 251 {"/proc/self/oom_adj", -17}, /* kernels <= 2.6.35 */ 252 {NULL, 0}, 253 }; 254 255 /* 256 * Tell the kernel's out-of-memory killer to avoid sshd. 257 * Returns the previous oom_adj value or zero. 258 */ 259 void 260 oom_adjust_setup(void) 261 { 262 int i, value; 263 FILE *fp; 264 265 debug3("%s", __func__); 266 for (i = 0; oom_adjust[i].path != NULL; i++) { 267 oom_adj_path = oom_adjust[i].path; 268 value = oom_adjust[i].value; 269 if ((fp = fopen(oom_adj_path, "r+")) != NULL) { 270 if (fscanf(fp, "%d", &oom_adj_save) != 1) 271 verbose("error reading %s: %s", oom_adj_path, 272 strerror(errno)); 273 else { 274 rewind(fp); 275 if (fprintf(fp, "%d\n", value) <= 0) 276 verbose("error writing %s: %s", 277 oom_adj_path, strerror(errno)); 278 else 279 debug("Set %s from %d to %d", 280 oom_adj_path, oom_adj_save, value); 281 } 282 fclose(fp); 283 return; 284 } 285 } 286 oom_adj_path = NULL; 287 } 288 289 /* Restore the saved OOM adjustment */ 290 void 291 oom_adjust_restore(void) 292 { 293 FILE *fp; 294 295 debug3("%s", __func__); 296 if (oom_adj_save == INT_MIN || oom_adj_path == NULL || 297 (fp = fopen(oom_adj_path, "w")) == NULL) 298 return; 299 300 if (fprintf(fp, "%d\n", oom_adj_save) <= 0) 301 verbose("error writing %s: %s", oom_adj_path, strerror(errno)); 302 else 303 debug("Set %s to %d", oom_adj_path, oom_adj_save); 304 305 fclose(fp); 306 return; 307 } 308 #endif /* LINUX_OOM_ADJUST */ 309 #endif /* WITH_SELINUX || LINUX_OOM_ADJUST */ 310
