From 3e98406d1fa4ad8387d99e7f881fb65fad1ae190 Mon Sep 17 00:00:00 2001
From: "Anna (navi) Figueiredo Gomes" <navi@vlhl.dev>
Date: Sun, 27 Oct 2024 15:52:28 +0100
Subject: [PATCH] pam_openrc

---
 src/meson.build             |  1 +
 src/pam_openrc/meson.build  | 11 +++++
 src/pam_openrc/pam_openrc.c | 87 +++++++++++++++++++++++++++++++++++++
 3 files changed, 99 insertions(+)
 create mode 100644 src/pam_openrc/meson.build
 create mode 100644 src/pam_openrc/pam_openrc.c

diff --git a/src/meson.build b/src/meson.build
index 1dce3c0f..10d88c4e 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -19,6 +19,7 @@ subdir('openrc-init')
 subdir('openrc-run')
 subdir('openrc-shutdown')
 subdir('openrc-user')
+subdir('pam_openrc')
 subdir('poweroff')
 subdir('rc-abort')
 subdir('rc-depend')
diff --git a/src/pam_openrc/meson.build b/src/pam_openrc/meson.build
new file mode 100644
index 00000000..54fd1eca
--- /dev/null
+++ b/src/pam_openrc/meson.build
@@ -0,0 +1,11 @@
+if get_option('pam') and pam_dep.found()
+  shared_module('pam_openrc',
+    ['pam_openrc.c', misc_c, version_h],
+    c_args : [cc_branding_flags],
+    dependencies : [pam_dep],
+    name_prefix : '',
+    link_with : [libeinfo, librc],
+    include_directories : [incdir, einfo_incdir, rc_incdir],
+    install : true,
+    install_dir : libdir / 'security')
+endif
diff --git a/src/pam_openrc/pam_openrc.c b/src/pam_openrc/pam_openrc.c
new file mode 100644
index 00000000..bea542f5
--- /dev/null
+++ b/src/pam_openrc/pam_openrc.c
@@ -0,0 +1,87 @@
+#include <fcntl.h>
+#include <pwd.h>
+#ifndef LINUX_PAM
+#include <security/pam_appl.h>
+#endif
+#include <security/pam_modules.h>
+#include <sys/file.h>
+#include <sys/wait.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#include <einfo.h>
+#include <rc.h>
+#include "helpers.h"
+
+static int lock_user(struct passwd *pw) {
+	char *file;
+	int fd;
+
+	xasprintf(&file, "%s/users/%s", rc_svcdir(), pw->pw_name);
+	elog(LOG_INFO, "Opening %s.", file);
+	fd = open(file, O_RDWR | O_CREAT | O_CLOEXEC, 0664);
+	free(file);
+
+	if (fd == -1 || flock(fd, LOCK_EX | LOCK_NB) == -1) {
+		elog(LOG_ERR, "Failed to lock lockfile.");
+		return -1;
+	}
+
+	return fd;
+}
+
+static int exec_openrc(pam_handle_t *pamh, bool start) {
+	const char *username, *session;
+	struct passwd *user;
+	char *elog_name;
+	int lockfile;
+	pid_t child;
+
+	if (pam_get_item(pamh, PAM_SERVICE, (const void **)&session) != PAM_SUCCESS)
+		return PAM_SESSION_ERR;
+	/* noop if the current stack was started by openrc-user, to avoid looping */
+	if (strcmp(session, "openrc-user") == 0)
+		return PAM_SUCCESS;
+
+	if (pam_get_user(pamh, &username, "") != PAM_SUCCESS || !(user = getpwnam(username)))
+		return PAM_SESSION_ERR;
+
+	if (user->pw_uid == 0)
+		return PAM_SUCCESS;
+
+	xasprintf(&elog_name, "pam_openrc[%s]", user->pw_name);
+	setenv("EINFO_LOG", elog_name, true);
+	free(elog_name);
+
+	if ((lockfile = lock_user(user)) == -1) {
+		unsetenv("EINFO_LOG");
+		return PAM_SESSION_ERR;
+	}
+
+	if ((child = fork()) == 0) {
+		setsid();
+		if (fork() == 0) {
+			execl(RC_LIBEXECDIR "/bin/openrc-user", "openrc-user", user->pw_name, start ? "start" : "stop", NULL);
+			elog(LOG_ERR, "Failed to exec openrc-user");
+			close(lockfile);
+			exit(1);
+		}
+		exit(0);
+	}
+
+	waitpid(child, NULL, 0);
+
+	close(lockfile);
+	unsetenv("EINFO_LOG");
+	return PAM_SUCCESS;
+}
+
+PAM_EXTERN int pam_sm_open_session(pam_handle_t *pamh, int flags, int argc, const char **argv) {
+	(void) flags; (void) argc; (void) argv;
+	return exec_openrc(pamh, true);
+}
+
+PAM_EXTERN int pam_sm_close_session(pam_handle_t *pamh, int flags, int argc, const char **argv) {
+	(void) flags; (void) argc; (void) argv;
+	return exec_openrc(pamh, false);
+}