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-rw-r--r--openbsd-compat/port-linux.c313
1 files changed, 313 insertions, 0 deletions
diff --git a/openbsd-compat/port-linux.c b/openbsd-compat/port-linux.c
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+++ b/openbsd-compat/port-linux.c
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+/*
+ * Copyright (c) 2005 Daniel Walsh <dwalsh@redhat.com>
+ * Copyright (c) 2006 Damien Miller <djm@openbsd.org>
+ *
+ * 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 <errno.h>
+#include <stdarg.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "log.h"
+#include "xmalloc.h"
+#include "port-linux.h"
+
+#ifdef WITH_SELINUX
+#include <selinux/selinux.h>
+#include <selinux/get_context_list.h>
+
+#ifndef SSH_SELINUX_UNCONFINED_TYPE
+# define SSH_SELINUX_UNCONFINED_TYPE ":unconfined_t:"
+#endif
+
+/* 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 = NULL;
+ 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);
+ sc = NULL;
+ break;
+ default:
+ fatal("%s: Failed to get default SELinux security "
+ "context for %s (in enforcing mode)",
+ __func__, pwname);
+ }
+ }
+
+#ifdef HAVE_GETSEUSERBYNAME
+ free(sename);
+ free(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;
+ security_class_t chrclass;
+
+ 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 ((chrclass = string_to_security_class("chr_file")) == 0) {
+ error("%s: couldn't get security class for chr_file", __func__);
+ goto out;
+ }
+ if (security_compute_relabel(user_ctx, old_tty_ctx,
+ chrclass, &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;
+ void (*switchlog) (const char *fmt,...) = logit;
+
+ 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;
+ }
+
+ /*
+ * Check whether we are attempting to switch away from an unconfined
+ * security context.
+ */
+ if (strncmp(cx, SSH_SELINUX_UNCONFINED_TYPE,
+ sizeof(SSH_SELINUX_UNCONFINED_TYPE) - 1) == 0)
+ switchlog = debug3;
+
+ 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)
+ switchlog("%s: setcon %s from %s failed with %s", __func__,
+ newctx, oldctx, strerror(errno));
+ free(oldctx);
+ free(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
+ debug("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
+ debug("Set %s to %d", oom_adj_path, oom_adj_save);
+
+ fclose(fp);
+ return;
+}
+#endif /* LINUX_OOM_ADJUST */
+#endif /* WITH_SELINUX || LINUX_OOM_ADJUST */