Add a new library: libulog.

One of the things I really want to do, is to get rid of the limitations
of our current utmp(5) mechanism:

- It only allows 8 byte TTY device names.
- The hostname only allows 16 bytes of storage.

I'm not a big fan of <utmpx.h>, but I think we should at least try to
add parts of it. Unfortunately we cannot implement <utmpx.h>, because we
miss various fields, such as ut_id, ut_pid, etc. The API provided by
libulog shares some similarities with <utmpx.h>, so it shouldn't be too
hard to port these applications eventually. In most simple cases, it
should just be a matter of removing the ulog_ prefix everywhere.

As a bonus, it also implements a function called ulog_login_pseudo(),
which allows unprivileged applications to write log entries, provided
they have a valid file descriptor to a pseudo-terminal master device.

libulog will allow a smoother transition to a new file format by adding
a library interface to deal with utmp/wtmp/lastlog files. I initially
thought about adding the functionality to libutil, but because I'm not
planning on keeping this library around forever, we'd better keep it
separated.

Next items on the todo list:

1. Port applications in the base system (and ports) to libulog, instead
   of letting them use <utmp.h>.
2. Remove <utmp.h>, implement <utmpx.h> and reimplement this library on
   top.
3. Port as many applications as possible back to <utmpx.h>.

1 files changed, 93 insertions, 0 deletions

diff --git a/lib/libulog/ulog_login_pseudo.c b/lib/libulog/ulog_login_pseudo.c
new file mode 100644
index 0000000..841a2db
--- /dev/null
+++ b/lib/libulog/ulog_login_pseudo.c
@@ -0,0 +1,93 @@
+/*-
+ * Copyright (c) 2009 Ed Schouten <ed@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/wait.h>
+
+#include <errno.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#include "ulog_internal.h"
+
+#define	_PATH_ULOG_HELPER	"/usr/libexec/ulog-helper"
+
+/*
+ * Registering login sessions.
+ */
+
+static void
+ulog_exec_helper(int fd, char const * const argv[])
+{
+	sigset_t oblock, nblock;
+	pid_t pid, wpid;
+	int status;
+
+	/* Block SIGCHLD. */
+	sigemptyset(&nblock);
+	sigaddset(&nblock, SIGCHLD);
+	sigprocmask(SIG_BLOCK, &nblock, &oblock);
+
+	switch (pid = fork()) {
+	case -1:
+		break;
+	case 0:
+		/* Execute helper program. */
+		if (dup2(fd, STDIN_FILENO) == -1)
+			exit(EX_UNAVAILABLE);
+		sigprocmask(SIG_SETMASK, &oblock, NULL);
+		execv(_PATH_ULOG_HELPER, __DECONST(char * const *, argv));
+		exit(EX_UNAVAILABLE);
+	default:
+		/* Wait for helper to finish. */
+		do {
+			wpid = waitpid(pid, &status, 0);
+		} while (wpid == -1 && errno == EINTR);
+		break;
+	}
+
+	sigprocmask(SIG_SETMASK, &oblock, NULL);
+}
+
+void
+ulog_login_pseudo(int fd, const char *host)
+{
+	char const * const args[4] = { "ulog-helper", "login", host, NULL };
+
+	ulog_exec_helper(fd, args);
+}
+
+void
+ulog_logout_pseudo(int fd)
+{
+	char const * const args[3] = { "ulog-helper", "logout", NULL };
+
+	ulog_exec_helper(fd, args);
+}