Implement OpenBSD authentication using bsd_auth(3).

OpenBSD does not have nor use pam(8) for password authentication but
instead uses bsd_auth(3): add a bsd_auth authentication scheme to
make locking possible.
This has been a part of gnome-screensaver already but was probably
removed at one point. This is mostly identical to that code, with some
minor modifications.

4 files changed, 123 insertions, 7 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 298382d..9b32abf 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -256,9 +256,13 @@ install-exec-hook:
 	@if [ "x@NEED_SETUID@" = "xyes" ]; then \
 	    echo "***" ; \
 	    echo "***  Warning: mate-screensaver has been compiled with support for" ; \
-	    echo "***           shadow passwords.  If your system actually uses shadow" ; \
-	    echo "***           passwords then it must be installed as a setuid root" ; \
-	    echo "***           program in order for locking to work.  To do this, you" ; \
+	    if [ "x@AUTH_SCHEME@" = "xbsdauth" ]; then \
+		echo "***           bsd_auth(3) and must be installed as a setuid root" ; \
+	    else \
+	        echo "***           shadow passwords. If your system actually uses shadow" ; \
+	        echo "***           passwords then it must be installed as a setuid root" ; \
+	    fi; \
+	    echo "***           program in order for locking to work. To do this, you" ; \
 	    echo "***           must run:" ; \
 	    echo "***" ; \
 	    echo "***           chown root $(DESTDIR)$(libexecdir)/mate-screensaver-dialog" ; \
diff --git a/src/gs-auth-bsdauth.c b/src/gs-auth-bsdauth.c
new file mode 100644
index 0000000..3463974
--- /dev/null
+++ b/src/gs-auth-bsdauth.c
@@ -0,0 +1,103 @@
+/*
+ * gs-auth-bsdauth.c --- verifying typed passwords with bsd_auth(3)
+ *
+ * Copyright (c) 1993-1998 Jamie Zawinski <[email protected]>
+ * Copyright (C) 2006 William Jon McCann <[email protected]>
+ * Copyright (c) 2009 Antoine Jacoutot <[email protected]>
+ * Copyright (c) 2017 Robert Nagy <[email protected]>
+ *
+ * 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.
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+#include <pwd.h>
+#include <sys/types.h>
+
+#include <login_cap.h>
+#include <bsd_auth.h>
+
+#include "gs-auth.h"
+#include "subprocs.h"
+
+static gboolean verbose_enabled = FALSE;
+
+GQuark
+gs_auth_error_quark (void)
+{
+	static GQuark quark = 0;
+	if (! quark) {
+		quark = g_quark_from_static_string ("gs_auth_error");
+	}
+
+	return quark;
+}
+
+void
+gs_auth_set_verbose (gboolean enabled)
+{
+	verbose_enabled = enabled;
+}
+
+gboolean
+gs_auth_get_verbose (void)
+{
+	return verbose_enabled;
+}
+
+gboolean
+gs_auth_verify_user (const char       *username,
+                     const char       *display,
+                     GSAuthMessageFunc func,
+                     gpointer          data,
+                     GError          **error)
+{
+	int res;
+	char *password;
+
+	/* ask for the password for user */
+	if (func != NULL) {
+		func (GS_AUTH_MESSAGE_PROMPT_ECHO_OFF,
+		    "Password: ",
+		    &password,
+		    data);
+	}
+
+	if (password == NULL) {
+		return FALSE;
+	}
+
+	/* authenticate */
+	res = auth_userokay((char *)username, NULL, "auth-mate-screensaver", password);
+
+	return res;
+}
+
+gboolean
+gs_auth_init (void)
+{
+	return TRUE;
+}
+
+gboolean
+gs_auth_priv_init (void)
+{
+	return TRUE;
+}
diff --git a/src/gs-auth-pwent.c b/src/gs-auth-pwent.c
index 0b253c6..a0c1d80 100644
--- a/src/gs-auth-pwent.c
+++ b/src/gs-auth-pwent.c
@@ -171,10 +171,10 @@ get_encrypted_passwd (const char *user)
 		}
 	}
 
-#ifndef HAVE_PAM
-	/* We only issue this warning if not compiled with support for PAM.
-	   If we're using PAM, it's not unheard of that normal pwent passwords
-	   would be unavailable. */
+#if !defined(HAVE_PAM) && !defined(HAVE_BSDAUTH)
+	/* We only issue this warning if not compiled with support for PAM,
+	   or bsd_auth(3). If we're using PAM, it's not unheard of that
+	   normal pwent passwords would be unavailable. */
 
 	if (!result)
 	{
diff --git a/src/setuid.c b/src/setuid.c
index 80e4659..0a065d9 100644
--- a/src/setuid.c
+++ b/src/setuid.c
@@ -209,6 +209,15 @@ hack_uid (char **nolock_reason,
 
 		if (uid != euid || gid != egid)
 		{
+#ifdef HAVE_BSDAUTH /* we need to setgid auth to run the bsd_auth(3) login_* helpers */
+			struct group *authg = getgrnam("auth");
+			if (!authg || !authg->gr_name || !*authg->gr_name) {
+				reason = g_strdup ("no such group as \"auth\" for bsdauth.");
+				ret = FALSE;
+				goto out;
+			}
+			gid = authg->gr_gid;
+#endif /* !HAVE_BSDAUTH */
 			if (! set_ids_by_number (uid, gid, uid_message))
 			{
 				reason = g_strdup ("unable to discard privileges.");