systemd/1012-pam_systemd_do_override_XDG_RUNTIME_DIR_of_the_original_user.patch

Based on upstream baae0358f349870544884e405e82e4be7d8add9f
| From: Lennart Poettering <lennart@poettering.net>
| Date: Tue, 26 Nov 2013 04:05:00 +0000
| Subject: pam_systemd: do not set XDG_RUNTIME_DIR if the session's original user is not the same as the newly logged in one
| It's better not to set any XDG_RUNTIME_DIR at all rather than one of a
| different user. So let's do this.
--- systemd-208/src/login/logind-dbus.c
+++ systemd-208/src/login/logind-dbus.c	2013-11-26 13:37:05.730735774 +0000
@@ -523,6 +523,7 @@ static int bus_manager_create_session(Ma
                                 DBUS_TYPE_OBJECT_PATH, &path,
                                 DBUS_TYPE_STRING, &session->user->runtime_path,
                                 DBUS_TYPE_UNIX_FD, &fifo_fd,
+                                DBUS_TYPE_UINT32, &session->user->uid,
                                 DBUS_TYPE_STRING, &cseat,
                                 DBUS_TYPE_UINT32, &vtnr,
                                 DBUS_TYPE_BOOLEAN, &exists,
--- systemd-208/src/login/logind-session-dbus.c
+++ systemd-208/src/login/logind-session-dbus.c	2013-11-26 13:36:07.478236401 +0000
@@ -755,6 +755,7 @@ int session_send_create_reply(Session *s
                                     DBUS_TYPE_OBJECT_PATH, &path,
                                     DBUS_TYPE_STRING, &s->user->runtime_path,
                                     DBUS_TYPE_UNIX_FD, &fifo_fd,
+                                    DBUS_TYPE_UINT32, &s->user->uid,
                                     DBUS_TYPE_STRING, &cseat,
                                     DBUS_TYPE_UINT32, &vtnr,
                                     DBUS_TYPE_BOOLEAN, &exists,
--- systemd-208/src/login/pam-module.c
+++ systemd-208/src/login/pam-module.c	2013-11-26 14:32:20.194235777 +0000
@@ -93,24 +93,18 @@ static int get_user_data(
         assert(ret_username);
         assert(ret_pw);
 
-        r = audit_loginuid_from_pid(0, &uid);
-        if (r >= 0)
-                pw = pam_modutil_getpwuid(handle, uid);
-        else {
-                r = pam_get_user(handle, &username, NULL);
-                if (r != PAM_SUCCESS) {
-                        pam_syslog(handle, LOG_ERR, "Failed to get user name.");
-                        return r;
-                }
-
-                if (isempty(username)) {
-                        pam_syslog(handle, LOG_ERR, "User name not valid.");
-                        return PAM_AUTH_ERR;
-                }
+        r = pam_get_user(handle, &username, NULL);
+        if (r != PAM_SUCCESS) {
+                pam_syslog(handle, LOG_ERR, "Failed to get user name.");
+                return r;
+        }
 
-                pw = pam_modutil_getpwnam(handle, username);
+        if (isempty(username)) {
+                pam_syslog(handle, LOG_ERR, "User name not valid.");
+                return PAM_AUTH_ERR;
         }
 
+        pw = pam_modutil_getpwnam(handle, username);
         if (!pw) {
                 pam_syslog(handle, LOG_ERR, "Failed to get user data.");
                 return PAM_USER_UNKNOWN;
@@ -123,16 +117,14 @@ static int get_user_data(
 }
 
 static int get_seat_from_display(const char *display, const char **seat, uint32_t *vtnr) {
-        _cleanup_free_ char *p = NULL;
-        int r;
-        _cleanup_close_ int fd = -1;
         union sockaddr_union sa = {
                 .un.sun_family = AF_UNIX,
         };
+         _cleanup_free_ char *p = NULL, *tty = NULL;
+         _cleanup_close_ int fd = -1;
         struct ucred ucred;
         socklen_t l;
-        _cleanup_free_ char *tty = NULL;
-        int v;
+        int v, r;
 
         assert(display);
         assert(vtnr);
@@ -194,13 +186,12 @@ _public_ PAM_EXTERN int pam_sm_open_sess
         dbus_bool_t remote, existing;
         int r;
         uint32_t vtnr = 0;
+        uid_t original_uid;
 
         assert(handle);
 
         dbus_error_init(&error);
 
-        /* pam_syslog(handle, LOG_INFO, "pam-systemd initializing"); */
-
         /* Make this a NOP on non-logind systems */
         if (!logind_running())
                 return PAM_SUCCESS;
@@ -213,6 +204,9 @@ _public_ PAM_EXTERN int pam_sm_open_sess
                 goto finish;
         }
 
+        if (debug)
+                pam_syslog(handle, LOG_INFO, "pam-systemd initializing");
+
         r = get_user_data(handle, &username, &pw);
         if (r != PAM_SUCCESS)
                 goto finish;
@@ -374,7 +368,11 @@ _public_ PAM_EXTERN int pam_sm_open_sess
         if (debug)
                 pam_syslog(handle, LOG_DEBUG, "Asking logind to create session: "
                            "uid=%u pid=%u service=%s type=%s class=%s seat=%s vtnr=%u tty=%s display=%s remote=%s remote_user=%s remote_host=%s",
-                           uid, pid, service, type, class, seat, vtnr, tty, display, yes_no(remote), remote_user, remote_host);
+                              pw->pw_uid, pid,
+                              strempty(service),
+                              type, class,
+                              seat, vtnr, tty, display,
+                              yes_no(remote), remote_user, remote_host);
 
         reply = dbus_connection_send_with_reply_and_block(bus, m, -1, &error);
         if (!reply) {
@@ -388,6 +386,7 @@ _public_ PAM_EXTERN int pam_sm_open_sess
                                    DBUS_TYPE_OBJECT_PATH, &object_path,
                                    DBUS_TYPE_STRING, &runtime_path,
                                    DBUS_TYPE_UNIX_FD, &session_fd,
+                                   DBUS_TYPE_UINT32, &original_uid,
                                    DBUS_TYPE_STRING, &seat,
                                    DBUS_TYPE_UINT32, &vtnr,
                                    DBUS_TYPE_BOOLEAN, &existing,
@@ -399,8 +398,8 @@ _public_ PAM_EXTERN int pam_sm_open_sess
 
         if (debug)
                 pam_syslog(handle, LOG_DEBUG, "Reply from logind: "
-                           "id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u",
-                           id, object_path, runtime_path, session_fd, seat, vtnr);
+                           "id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u original_uid=%u",
+                           id, object_path, runtime_path, session_fd, seat, vtnr, original_uid);
 
         r = pam_misc_setenv(handle, "XDG_SESSION_ID", id, 0);
         if (r != PAM_SUCCESS) {
@@ -408,10 +407,24 @@ _public_ PAM_EXTERN int pam_sm_open_sess
                 goto finish;
         }
 
-        r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", runtime_path, 0);
-        if (r != PAM_SUCCESS) {
-                pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
-                goto finish;
+        if (original_uid == pw->pw_uid) {
+                /* Don't set $XDG_RUNTIME_DIR if the user we now
+                 * authenticated for does not match the original user
+                 * of the session. We do this in order not to result
+                 * in privileged apps clobbering the runtime directory
+                 * unnecessarily. */
+
+                r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", runtime_path, 0);
+                if (r != PAM_SUCCESS) {
+                         pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
+                         goto finish;
+                }
+        } else if (getenv("XDG_RUNTIME_DIR")) {
+                r = pam_putenv(handle, "XDG_RUNTIME_DIR");
+                if (r != PAM_SUCCESS && r != PAM_BAD_ITEM) {
+                         pam_syslog(handle, LOG_ERR, "Failed to unset runtime dir.");
+                }
+                (void) unsetenv("XDG_RUNTIME_DIR");
         }
 
         if (!isempty(seat)) {