1 files changed, 269 insertions, 0 deletions
diff --git a/modules/pam_keyinit/pam_keyinit.c b/modules/pam_keyinit/pam_keyinit.c
new file mode 100644
index 00000000..378a7723
--- /dev/null
+++ b/modules/pam_keyinit/pam_keyinit.c
@@ -0,0 +1,269 @@
+/* pam_keyinit.c: Initialise the session keyring on login through a PAM module
+ *
+ * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include "config.h"
+#include <stdarg.h>
+#include <string.h>
+#include <syslog.h>
+#include <pwd.h>
+#include <unistd.h>
+#include <errno.h>
+#include <security/pam_modules.h>
+#include <security/pam_modutil.h>
+#include <security/pam_ext.h>
+#include <sys/syscall.h>
+
+#define KEY_SPEC_SESSION_KEYRING	-3 /* ID for session keyring */
+#define KEY_SPEC_USER_KEYRING		-4 /* ID for UID-specific keyring */
+#define KEY_SPEC_USER_SESSION_KEYRING	-5 /* - key ID for UID-session keyring */
+
+#define KEYCTL_GET_KEYRING_ID		0 /* ask for a keyring's ID */
+#define KEYCTL_JOIN_SESSION_KEYRING	1 /* start named session keyring */
+#define KEYCTL_REVOKE			3 /* revoke a key */
+#define KEYCTL_LINK			8 /* link a key into a keyring */
+
+static int my_session_keyring;
+static int session_counter;
+static int do_revoke;
+static int revoke_as_uid;
+static int revoke_as_gid;
+static int xdebug = 0;
+
+static void debug(pam_handle_t *pamh, const char *fmt, ...)
+	__attribute__((format(printf, 2, 3)));
+
+static void debug(pam_handle_t *pamh, const char *fmt, ...)
+{
+	va_list va;
+
+	if (xdebug) {
+		va_start(va, fmt);
+		pam_vsyslog(pamh, LOG_DEBUG, fmt, va);
+		va_end(va);
+	}
+}
+
+static int error(pam_handle_t *pamh, const char *fmt, ...)
+	__attribute__((format(printf, 2, 3)));
+
+static int error(pam_handle_t *pamh, const char *fmt, ...)
+{
+	va_list va;
+
+	va_start(va, fmt);
+	pam_vsyslog(pamh, LOG_ERR, fmt, va);
+	va_end(va);
+
+	return PAM_SESSION_ERR;
+}
+
+/*
+ * initialise the session keyring for this process
+ */
+static int init_keyrings(pam_handle_t *pamh, int force)
+{
+	int session, usession, ret;
+
+	if (!force) {
+		/* get the IDs of the session keyring and the user session
+		 * keyring */
+		session = syscall(__NR_keyctl,
+				  KEYCTL_GET_KEYRING_ID,
+				  KEY_SPEC_SESSION_KEYRING,
+				  0);
+		debug(pamh, "GET SESSION = %d", session);
+		if (session < 0) {
+			/* don't worry about keyrings if facility not
+			 * installed */
+			if (errno == ENOSYS)
+				return PAM_SUCCESS;
+			return PAM_SESSION_ERR;
+		}
+
+		usession = syscall(__NR_keyctl,
+				   KEYCTL_GET_KEYRING_ID,
+				   KEY_SPEC_USER_SESSION_KEYRING,
+				   0);
+		debug(pamh, "GET SESSION = %d", usession);
+		if (usession < 0)
+			return PAM_SESSION_ERR;
+
+		/* if the user session keyring is our keyring, then we don't
+		 * need to do anything if we're not forcing */
+		if (session != usession)
+			return PAM_SUCCESS;
+	}
+
+	/* create a session keyring, discarding the old one */
+	ret = syscall(__NR_keyctl,
+		      KEYCTL_JOIN_SESSION_KEYRING,
+		      NULL);
+	debug(pamh, "JOIN = %d", ret);
+	if (ret < 0)
+		return PAM_SESSION_ERR;
+
+	my_session_keyring = ret;
+
+	/* make a link from the session keyring to the user keyring */
+	ret = syscall(__NR_keyctl,
+		      KEYCTL_LINK,
+		      KEY_SPEC_USER_KEYRING,
+		      KEY_SPEC_SESSION_KEYRING);
+
+	return ret < 0 ? PAM_SESSION_ERR : PAM_SUCCESS;
+}
+
+/*
+ * revoke the session keyring for this process
+ */
+static void kill_keyrings(pam_handle_t *pamh)
+{
+	int old_uid, old_gid;
+
+	/* revoke the session keyring we created earlier */
+	if (my_session_keyring > 0) {
+		debug(pamh, "REVOKE %d", my_session_keyring);
+
+		old_uid = geteuid();
+		old_gid = getegid();
+		debug(pamh, "UID:%d [%d]  GID:%d [%d]",
+		      revoke_as_uid, old_uid, revoke_as_gid, old_gid);
+
+		/* switch to the real UID and GID so that we have permission to
+		 * revoke the key */
+		if (revoke_as_gid != old_gid && setregid(-1, revoke_as_gid) < 0)
+			error(pamh, "Unable to change GID to %d temporarily\n",
+			      revoke_as_gid);
+
+		if (revoke_as_uid != old_uid && setreuid(-1, revoke_as_uid) < 0)
+			error(pamh, "Unable to change UID to %d temporarily\n",
+			      revoke_as_uid);
+
+		syscall(__NR_keyctl,
+			KEYCTL_REVOKE,
+			my_session_keyring);
+
+		/* return to the orignal UID and GID (probably root) */
+		if (revoke_as_uid != old_uid && setreuid(-1, old_uid) < 0)
+			error(pamh, "Unable to change UID back to %d\n", old_uid);
+
+		if (revoke_as_gid != old_gid && setregid(-1, old_gid) < 0)
+			error(pamh, "Unable to change GID back to %d\n", old_gid);
+
+		my_session_keyring = 0;
+	}
+}
+
+/*
+ * open a PAM session by making sure there's a session keyring
+ */
+PAM_EXTERN
+int pam_sm_open_session(pam_handle_t *pamh, int flags UNUSED,
+			int argc, const char **argv)
+{
+	struct passwd *pw;
+	const char *username;
+	int ret, old_uid, uid, old_gid, gid, loop, force = 0;
+
+	for (loop = 0; loop < argc; loop++) {
+		if (strcmp(argv[loop], "force") == 0)
+			force = 1;
+		else if (strcmp(argv[loop], "debug") == 0)
+			xdebug = 1;
+		else if (strcmp(argv[loop], "revoke") == 0)
+			do_revoke = 1;
+	}
+
+	/* don't do anything if already created a keyring (will be called
+	 * multiple times if mentioned more than once in a pam script)
+	 */
+	session_counter++;
+
+	debug(pamh, "OPEN %d", session_counter);
+
+	if (my_session_keyring > 0)
+		return PAM_SUCCESS;
+
+	/* look up the target UID */
+	ret = pam_get_user(pamh, &username, "key user");
+	if (ret != PAM_SUCCESS)
+		return ret;
+
+	pw = pam_modutil_getpwnam(pamh, username);
+	if (!pw) {
+		error(pamh, "Unable to look up user \"%s\"\n", username);
+		return PAM_USER_UNKNOWN;
+	}
+
+	revoke_as_uid = uid = pw->pw_uid;
+	old_uid = getuid();
+	revoke_as_gid = gid = pw->pw_gid;
+	old_gid = getgid();
+	debug(pamh, "UID:%d [%d]  GID:%d [%d]", uid, old_uid, gid, old_gid);
+
+	/* switch to the real UID and GID so that the keyring ends up owned by
+	 * the right user */
+	if (gid != old_gid && setregid(gid, -1) < 0) {
+		error(pamh, "Unable to change GID to %d temporarily\n", gid);
+		return PAM_SESSION_ERR;
+	}
+
+	if (uid != old_uid && setreuid(uid, -1) < 0) {
+		error(pamh, "Unable to change UID to %d temporarily\n", uid);
+		setregid(old_gid, -1);
+		return PAM_SESSION_ERR;
+	}
+
+	ret = init_keyrings(pamh, force);
+
+	/* return to the orignal UID and GID (probably root) */
+	if (uid != old_uid && setreuid(old_uid, -1) < 0)
+		ret = error(pamh, "Unable to change UID back to %d\n", old_uid);
+
+	if (gid != old_gid && setregid(old_gid, -1) < 0)
+		ret = error(pamh, "Unable to change GID back to %d\n", old_gid);
+
+	return ret;
+}
+
+/*
+ * close a PAM session by revoking the session keyring if requested
+ */
+PAM_EXTERN
+int pam_sm_close_session(pam_handle_t *pamh, int flags UNUSED,
+			 int argc UNUSED, const char **argv UNUSED)
+{
+	debug(pamh, "CLOSE %d,%d,%d",
+	      session_counter, my_session_keyring, do_revoke);
+
+	session_counter--;
+
+	if (session_counter == 0 && my_session_keyring > 0 && do_revoke)
+		kill_keyrings(pamh);
+
+	return PAM_SUCCESS;
+}
+
+#ifdef PAM_STATIC
+
+/* static module data */
+
+struct pam_module _pam_keyinit_modstruct = {
+     "pam_keyinit",
+     NULL,
+     NULL,
+     NULL,
+     pam_sm_open_session,
+     pam_sm_close_session,
+     NULL
+};
+#endif
+