1 /* $Id: port-linux.c,v 1.18 2013/06/01 22:07:32 dtucker Exp $ */ 2 3 /* 4 * Copyright (c) 2005 Daniel Walsh <dwalsh (at) redhat.com> 5 * Copyright (c) 2006 Damien Miller <djm (at) openbsd.org> 6 * 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. 10 * 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. 18 */ 19 20 /* 21 * Linux-specific portability code - just SELinux support at present 22 */ 23 24 #include "includes.h" 25 26 #if defined(WITH_SELINUX) || defined(LINUX_OOM_ADJUST) 27 #include <errno.h> 28 #include <stdarg.h> 29 #include <string.h> 30 #include <stdio.h> 31 32 #include "log.h" 33 #include "xmalloc.h" 34 #include "port-linux.h" 35 36 #ifdef WITH_SELINUX 37 #include <selinux/selinux.h> 38 #include <selinux/flask.h> 39 #include <selinux/get_context_list.h> 40 41 #ifndef SSH_SELINUX_UNCONFINED_TYPE 42 # define SSH_SELINUX_UNCONFINED_TYPE ":unconfined_t:" 43 #endif 44 45 /* Wrapper around is_selinux_enabled() to log its return value once only */ 46 int 47 ssh_selinux_enabled(void) 48 { 49 static int enabled = -1; 50 51 if (enabled == -1) { 52 enabled = (is_selinux_enabled() == 1); 53 debug("SELinux support %s", enabled ? "enabled" : "disabled"); 54 } 55 56 return (enabled); 57 } 58 59 /* Return the default security context for the given username */ 60 static security_context_t 61 ssh_selinux_getctxbyname(char *pwname) 62 { 63 security_context_t sc = NULL; 64 char *sename = NULL, *lvl = NULL; 65 int r; 66 67 #ifdef HAVE_GETSEUSERBYNAME 68 if (getseuserbyname(pwname, &sename, &lvl) != 0) 69 return NULL; 70 #else 71 sename = pwname; 72 lvl = NULL; 73 #endif 74 75 #ifdef HAVE_GET_DEFAULT_CONTEXT_WITH_LEVEL 76 r = get_default_context_with_level(sename, lvl, NULL, &sc); 77 #else 78 r = get_default_context(sename, NULL, &sc); 79 #endif 80 81 if (r != 0) { 82 switch (security_getenforce()) { 83 case -1: 84 fatal("%s: ssh_selinux_getctxbyname: " 85 "security_getenforce() failed", __func__); 86 case 0: 87 error("%s: Failed to get default SELinux security " 88 "context for %s", __func__, pwname); 89 sc = NULL; 90 break; 91 default: 92 fatal("%s: Failed to get default SELinux security " 93 "context for %s (in enforcing mode)", 94 __func__, pwname); 95 } 96 } 97 98 #ifdef HAVE_GETSEUSERBYNAME 99 free(sename); 100 free(lvl); 101 #endif 102 103 return sc; 104 } 105 106 /* Set the execution context to the default for the specified user */ 107 void 108 ssh_selinux_setup_exec_context(char *pwname) 109 { 110 security_context_t user_ctx = NULL; 111 112 if (!ssh_selinux_enabled()) 113 return; 114 115 debug3("%s: setting execution context", __func__); 116 117 user_ctx = ssh_selinux_getctxbyname(pwname); 118 if (setexeccon(user_ctx) != 0) { 119 switch (security_getenforce()) { 120 case -1: 121 fatal("%s: security_getenforce() failed", __func__); 122 case 0: 123 error("%s: Failed to set SELinux execution " 124 "context for %s", __func__, pwname); 125 break; 126 default: 127 fatal("%s: Failed to set SELinux execution context " 128 "for %s (in enforcing mode)", __func__, pwname); 129 } 130 } 131 if (user_ctx != NULL) 132 freecon(user_ctx); 133 134 debug3("%s: done", __func__); 135 } 136 137 /* Set the TTY context for the specified user */ 138 void 139 ssh_selinux_setup_pty(char *pwname, const char *tty) 140 { 141 security_context_t new_tty_ctx = NULL; 142 security_context_t user_ctx = NULL; 143 security_context_t old_tty_ctx = NULL; 144 145 if (!ssh_selinux_enabled()) 146 return; 147 148 debug3("%s: setting TTY context on %s", __func__, tty); 149 150 user_ctx = ssh_selinux_getctxbyname(pwname); 151 152 /* XXX: should these calls fatal() upon failure in enforcing mode? */ 153 154 if (getfilecon(tty, &old_tty_ctx) == -1) { 155 error("%s: getfilecon: %s", __func__, strerror(errno)); 156 goto out; 157 } 158 159 if (security_compute_relabel(user_ctx, old_tty_ctx, 160 SECCLASS_CHR_FILE, &new_tty_ctx) != 0) { 161 error("%s: security_compute_relabel: %s", 162 __func__, strerror(errno)); 163 goto out; 164 } 165 166 if (setfilecon(tty, new_tty_ctx) != 0) 167 error("%s: setfilecon: %s", __func__, strerror(errno)); 168 out: 169 if (new_tty_ctx != NULL) 170 freecon(new_tty_ctx); 171 if (old_tty_ctx != NULL) 172 freecon(old_tty_ctx); 173 if (user_ctx != NULL) 174 freecon(user_ctx); 175 debug3("%s: done", __func__); 176 } 177 178 void 179 ssh_selinux_change_context(const char *newname) 180 { 181 int len, newlen; 182 char *oldctx, *newctx, *cx; 183 void (*switchlog) (const char *fmt,...) = logit; 184 185 if (!ssh_selinux_enabled()) 186 return; 187 188 if (getcon((security_context_t *)&oldctx) < 0) { 189 logit("%s: getcon failed with %s", __func__, strerror(errno)); 190 return; 191 } 192 if ((cx = index(oldctx, ':')) == NULL || (cx = index(cx + 1, ':')) == 193 NULL) { 194 logit ("%s: unparseable context %s", __func__, oldctx); 195 return; 196 } 197 198 /* 199 * Check whether we are attempting to switch away from an unconfined 200 * security context. 201 */ 202 if (strncmp(cx, SSH_SELINUX_UNCONFINED_TYPE, 203 sizeof(SSH_SELINUX_UNCONFINED_TYPE) - 1) == 0) 204 switchlog = debug3; 205 206 newlen = strlen(oldctx) + strlen(newname) + 1; 207 newctx = xmalloc(newlen); 208 len = cx - oldctx + 1; 209 memcpy(newctx, oldctx, len); 210 strlcpy(newctx + len, newname, newlen - len); 211 if ((cx = index(cx + 1, ':'))) 212 strlcat(newctx, cx, newlen); 213 debug3("%s: setting context from '%s' to '%s'", __func__, 214 oldctx, newctx); 215 if (setcon(newctx) < 0) 216 switchlog("%s: setcon %s from %s failed with %s", __func__, 217 newctx, oldctx, strerror(errno)); 218 free(oldctx); 219 free(newctx); 220 } 221 222 void 223 ssh_selinux_setfscreatecon(const char *path) 224 { 225 security_context_t context; 226 227 if (!ssh_selinux_enabled()) 228 return; 229 if (path == NULL) { 230 setfscreatecon(NULL); 231 return; 232 } 233 if (matchpathcon(path, 0700, &context) == 0) 234 setfscreatecon(context); 235 } 236 237 #endif /* WITH_SELINUX */ 238 239 #ifdef LINUX_OOM_ADJUST 240 /* 241 * The magic "don't kill me" values, old and new, as documented in eg: 242 * http://lxr.linux.no/#linux+v2.6.32/Documentation/filesystems/proc.txt 243 * http://lxr.linux.no/#linux+v2.6.36/Documentation/filesystems/proc.txt 244 */ 245 246 static int oom_adj_save = INT_MIN; 247 static char *oom_adj_path = NULL; 248 struct { 249 char *path; 250 int value; 251 } oom_adjust[] = { 252 {"/proc/self/oom_score_adj", -1000}, /* kernels >= 2.6.36 */ 253 {"/proc/self/oom_adj", -17}, /* kernels <= 2.6.35 */ 254 {NULL, 0}, 255 }; 256 257 /* 258 * Tell the kernel's out-of-memory killer to avoid sshd. 259 * Returns the previous oom_adj value or zero. 260 */ 261 void 262 oom_adjust_setup(void) 263 { 264 int i, value; 265 FILE *fp; 266 267 debug3("%s", __func__); 268 for (i = 0; oom_adjust[i].path != NULL; i++) { 269 oom_adj_path = oom_adjust[i].path; 270 value = oom_adjust[i].value; 271 if ((fp = fopen(oom_adj_path, "r+")) != NULL) { 272 if (fscanf(fp, "%d", &oom_adj_save) != 1) 273 verbose("error reading %s: %s", oom_adj_path, 274 strerror(errno)); 275 else { 276 rewind(fp); 277 if (fprintf(fp, "%d\n", value) <= 0) 278 verbose("error writing %s: %s", 279 oom_adj_path, strerror(errno)); 280 else 281 verbose("Set %s from %d to %d", 282 oom_adj_path, oom_adj_save, value); 283 } 284 fclose(fp); 285 return; 286 } 287 } 288 oom_adj_path = NULL; 289 } 290 291 /* Restore the saved OOM adjustment */ 292 void 293 oom_adjust_restore(void) 294 { 295 FILE *fp; 296 297 debug3("%s", __func__); 298 if (oom_adj_save == INT_MIN || oom_adj_path == NULL || 299 (fp = fopen(oom_adj_path, "w")) == NULL) 300 return; 301 302 if (fprintf(fp, "%d\n", oom_adj_save) <= 0) 303 verbose("error writing %s: %s", oom_adj_path, strerror(errno)); 304 else 305 verbose("Set %s to %d", oom_adj_path, oom_adj_save); 306 307 fclose(fp); 308 return; 309 } 310 #endif /* LINUX_OOM_ADJUST */ 311 #endif /* WITH_SELINUX || LINUX_OOM_ADJUST */ 312
