/* $Id: port-linux.c,v 1.11.4.2 2011/02/04 00:43:08 djm Exp $ */ /* * Copyright (c) 2005 Daniel Walsh * Copyright (c) 2006 Damien Miller * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ /* * Linux-specific portability code - just SELinux support at present */ #include "includes.h" #if defined(WITH_SELINUX) || defined(LINUX_OOM_ADJUST) #include #include #include #include #include "log.h" #include "xmalloc.h" #include "port-linux.h" #ifdef WITH_SELINUX #include #include #include /* Wrapper around is_selinux_enabled() to log its return value once only */ int ssh_selinux_enabled(void) { static int enabled = -1; if (enabled == -1) { enabled = (is_selinux_enabled() == 1); debug("SELinux support %s", enabled ? "enabled" : "disabled"); } return (enabled); } /* Return the default security context for the given username */ static security_context_t ssh_selinux_getctxbyname(char *pwname) { security_context_t sc; char *sename = NULL, *lvl = NULL; int r; #ifdef HAVE_GETSEUSERBYNAME if (getseuserbyname(pwname, &sename, &lvl) != 0) return NULL; #else sename = pwname; lvl = NULL; #endif #ifdef HAVE_GET_DEFAULT_CONTEXT_WITH_LEVEL r = get_default_context_with_level(sename, lvl, NULL, &sc); #else r = get_default_context(sename, NULL, &sc); #endif if (r != 0) { switch (security_getenforce()) { case -1: fatal("%s: ssh_selinux_getctxbyname: " "security_getenforce() failed", __func__); case 0: error("%s: Failed to get default SELinux security " "context for %s", __func__, pwname); break; default: fatal("%s: Failed to get default SELinux security " "context for %s (in enforcing mode)", __func__, pwname); } } #ifdef HAVE_GETSEUSERBYNAME if (sename != NULL) xfree(sename); if (lvl != NULL) xfree(lvl); #endif return (sc); } /* Set the execution context to the default for the specified user */ void ssh_selinux_setup_exec_context(char *pwname) { security_context_t user_ctx = NULL; if (!ssh_selinux_enabled()) return; debug3("%s: setting execution context", __func__); user_ctx = ssh_selinux_getctxbyname(pwname); if (setexeccon(user_ctx) != 0) { switch (security_getenforce()) { case -1: fatal("%s: security_getenforce() failed", __func__); case 0: error("%s: Failed to set SELinux execution " "context for %s", __func__, pwname); break; default: fatal("%s: Failed to set SELinux execution context " "for %s (in enforcing mode)", __func__, pwname); } } if (user_ctx != NULL) freecon(user_ctx); debug3("%s: done", __func__); } /* Set the TTY context for the specified user */ void ssh_selinux_setup_pty(char *pwname, const char *tty) { security_context_t new_tty_ctx = NULL; security_context_t user_ctx = NULL; security_context_t old_tty_ctx = NULL; if (!ssh_selinux_enabled()) return; debug3("%s: setting TTY context on %s", __func__, tty); user_ctx = ssh_selinux_getctxbyname(pwname); /* XXX: should these calls fatal() upon failure in enforcing mode? */ if (getfilecon(tty, &old_tty_ctx) == -1) { error("%s: getfilecon: %s", __func__, strerror(errno)); goto out; } if (security_compute_relabel(user_ctx, old_tty_ctx, SECCLASS_CHR_FILE, &new_tty_ctx) != 0) { error("%s: security_compute_relabel: %s", __func__, strerror(errno)); goto out; } if (setfilecon(tty, new_tty_ctx) != 0) error("%s: setfilecon: %s", __func__, strerror(errno)); out: if (new_tty_ctx != NULL) freecon(new_tty_ctx); if (old_tty_ctx != NULL) freecon(old_tty_ctx); if (user_ctx != NULL) freecon(user_ctx); debug3("%s: done", __func__); } void ssh_selinux_change_context(const char *newname) { int len, newlen; char *oldctx, *newctx, *cx; if (!ssh_selinux_enabled()) return; if (getcon((security_context_t *)&oldctx) < 0) { logit("%s: getcon failed with %s", __func__, strerror (errno)); return; } if ((cx = index(oldctx, ':')) == NULL || (cx = index(cx + 1, ':')) == NULL) { logit ("%s: unparseable context %s", __func__, oldctx); return; } newlen = strlen(oldctx) + strlen(newname) + 1; newctx = xmalloc(newlen); len = cx - oldctx + 1; memcpy(newctx, oldctx, len); strlcpy(newctx + len, newname, newlen - len); if ((cx = index(cx + 1, ':'))) strlcat(newctx, cx, newlen); debug3("%s: setting context from '%s' to '%s'", __func__, oldctx, newctx); if (setcon(newctx) < 0) logit("%s: setcon failed with %s", __func__, strerror (errno)); xfree(oldctx); xfree(newctx); } void ssh_selinux_setfscreatecon(const char *path) { security_context_t context; if (!ssh_selinux_enabled()) return; if (path == NULL) setfscreatecon(NULL); return; } if (matchpathcon(path, 0700, &context) == 0) setfscreatecon(context); } #endif /* WITH_SELINUX */ #ifdef LINUX_OOM_ADJUST /* * The magic "don't kill me" values, old and new, as documented in eg: * http://lxr.linux.no/#linux+v2.6.32/Documentation/filesystems/proc.txt * http://lxr.linux.no/#linux+v2.6.36/Documentation/filesystems/proc.txt */ static int oom_adj_save = INT_MIN; static char *oom_adj_path = NULL; struct { char *path; int value; } oom_adjust[] = { {"/proc/self/oom_score_adj", -1000}, /* kernels >= 2.6.36 */ {"/proc/self/oom_adj", -17}, /* kernels <= 2.6.35 */ {NULL, 0}, }; /* * Tell the kernel's out-of-memory killer to avoid sshd. * Returns the previous oom_adj value or zero. */ void oom_adjust_setup(void) { int i, value; FILE *fp; debug3("%s", __func__); for (i = 0; oom_adjust[i].path != NULL; i++) { oom_adj_path = oom_adjust[i].path; value = oom_adjust[i].value; if ((fp = fopen(oom_adj_path, "r+")) != NULL) { if (fscanf(fp, "%d", &oom_adj_save) != 1) verbose("error reading %s: %s", oom_adj_path, strerror(errno)); else { rewind(fp); if (fprintf(fp, "%d\n", value) <= 0) verbose("error writing %s: %s", oom_adj_path, strerror(errno)); else verbose("Set %s from %d to %d", oom_adj_path, oom_adj_save, value); } fclose(fp); return; } } oom_adj_path = NULL; } /* Restore the saved OOM adjustment */ void oom_adjust_restore(void) { FILE *fp; debug3("%s", __func__); if (oom_adj_save == INT_MIN || oom_adj_path == NULL || (fp = fopen(oom_adj_path, "w")) == NULL) return; if (fprintf(fp, "%d\n", oom_adj_save) <= 0) verbose("error writing %s: %s", oom_adj_path, strerror(errno)); else verbose("Set %s to %d", oom_adj_path, oom_adj_save); fclose(fp); return; } #endif /* LINUX_OOM_ADJUST */ #endif /* WITH_SELINUX || LINUX_OOM_ADJUST */