Support reading ucred from the socket on FreeBSD

On FreeBSD we have to use getsockopt(fd, SOL_LOCAL, LOCAL_PEERCRED)
instead. This change is based on a downstream patch in FreeBSD ports.

Co-authored-by: Greg V <greg@unrelenting.technology>
Co-authored-by: Koop Mast <kwm@rainbow-runner.nl>
Signed-off-by: Alex Richardson <Alexander.Richardson@cl.cam.ac.uk>

meson.build

@@ -26,7 +26,7 @@ add_project_arguments(
 	language: 'c'
 )
 
-foreach h: [ 'sys/prctl.h' ]
+foreach h: [ 'sys/prctl.h', 'sys/ucred.h' ]
 	config_h.set('HAVE_' + h.underscorify().to_upper(), cc.has_header(h))
 endforeach
 
@@ -41,6 +41,7 @@ have_funcs = [
 foreach f: have_funcs
 	config_h.set('HAVE_' + f.underscorify().to_upper(), cc.has_function(f))
 endforeach
+config_h.set10('HAVE_XUCRED_CR_PID', cc.has_member('struct xucred', 'cr_pid', prefix : '#include <sys/ucred.h>'))
 
 if get_option('libraries')
 	if host_machine.system() == 'freebsd'

src/wayland-os.c

@@ -25,14 +25,19 @@
 
 #define _GNU_SOURCE
 
+#include "../config.h"
+
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <sys/epoll.h>
+#include <sys/un.h>
+#ifdef HAVE_SYS_UCRED_H
+#include <sys/ucred.h>
+#endif
 
-#include "../config.h"
 #include "wayland-os.h"
 
 static int
@@ -72,6 +77,46 @@ wl_os_socket_cloexec(int domain, int type, int protocol)
 	return set_cloexec_or_close(fd);
 }
 
+#if defined(__FreeBSD__)
+int
+wl_os_socket_peercred(int sockfd, uid_t *uid, gid_t *gid, pid_t *pid)
+{
+	socklen_t len;
+	struct xucred ucred;
+
+	len = sizeof(ucred);
+	if (getsockopt(sockfd, SOL_LOCAL, LOCAL_PEERCRED, &ucred, &len) < 0 ||
+	    ucred.cr_version != XUCRED_VERSION)
+		return -1;
+	*uid = ucred.cr_uid;
+	*gid = ucred.cr_gid;
+#if HAVE_XUCRED_CR_PID
+	/* Since https://cgit.freebsd.org/src/commit/?id=c5afec6e895a */
+	*pid = ucred.cr_pid;
+#else
+	*pid = 0;
+#endif
+	return 0;
+}
+#elif defined(SO_PEERCRED)
+int
+wl_os_socket_peercred(int sockfd, uid_t *uid, gid_t *gid, pid_t *pid)
+{
+	socklen_t len;
+	struct ucred ucred;
+
+	len = sizeof(ucred);
+	if (getsockopt(sockfd, SOL_SOCKET, SO_PEERCRED, &ucred, &len) < 0)
+		return -1;
+	*uid = ucred.uid;
+	*gid = ucred.gid;
+	*pid = ucred.pid;
+	return 0;
+}
+#else
+#error "Don't know how to read ucred on this platform"
+#endif
+
 int
 wl_os_dupfd_cloexec(int fd, int minfd)
 {

src/wayland-os.h

@@ -26,9 +26,15 @@
 #ifndef WAYLAND_OS_H
 #define WAYLAND_OS_H
 
+#include <sys/types.h>
+#include <sys/socket.h>
+
 int
 wl_os_socket_cloexec(int domain, int type, int protocol);
 
+int
+wl_os_socket_peercred(int sockfd, uid_t *uid, gid_t *gid, pid_t *pid);
+
 int
 wl_os_dupfd_cloexec(int fd, int minfd);
 

src/wayland-server.c

@@ -78,7 +78,9 @@ struct wl_client {
 	struct wl_list link;
 	struct wl_map objects;
 	struct wl_priv_signal destroy_signal;
-	struct ucred ucred;
+	pid_t pid;
+	uid_t uid;
+	gid_t gid;
 	int error;
 	struct wl_priv_signal resource_created_signal;
 };
@@ -314,7 +316,7 @@ wl_resource_post_error(struct wl_resource *resource,
 static void
 destroy_client_with_error(struct wl_client *client, const char *reason)
 {
-	wl_log("%s (pid %u)\n", reason, client->ucred.pid);
+	wl_log("%s (pid %u)\n", reason, client->pid);
 	wl_client_destroy(client);
 }
 
@@ -513,7 +515,6 @@ WL_EXPORT struct wl_client *
 wl_client_create(struct wl_display *display, int fd)
 {
 	struct wl_client *client;
-	socklen_t len;
 
 	client = zalloc(sizeof *client);
 	if (client == NULL)
@@ -528,9 +529,8 @@ wl_client_create(struct wl_display *display, int fd)
 	if (!client->source)
 		goto err_client;
 
-	len = sizeof client->ucred;
-	if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED,
-		       &client->ucred, &len) < 0)
+	if (wl_os_socket_peercred(fd, &client->uid, &client->gid,
+				  &client->pid) != 0)
 		goto err_source;
 
 	client->connection = wl_connection_create(fd);
@@ -586,11 +586,11 @@ wl_client_get_credentials(struct wl_client *client,
 			  pid_t *pid, uid_t *uid, gid_t *gid)
 {
 	if (pid)
-		*pid = client->ucred.pid;
+		*pid = client->pid;
 	if (uid)
-		*uid = client->ucred.uid;
+		*uid = client->uid;
 	if (gid)
-		*gid = client->ucred.gid;
+		*gid = client->gid;
 }
 
 /** Get the file descriptor for the client