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>.

2 files changed, 94 insertions, 0 deletions

diff --git a/libexec/ulog-helper/Makefile b/libexec/ulog-helper/Makefile
new file mode 100644
index 0000000..c420200
--- /dev/null
+++ b/libexec/ulog-helper/Makefile
@@ -0,0 +1,13 @@
+# $FreeBSD$
+
+PROG=	ulog-helper
+BINOWN=	root
+BINMODE=4555
+NO_MAN=
+
+DPADD=	${LIBULOG}
+LDADD=	-lulog
+
+WARNS?=	6
+
+.include <bsd.prog.mk>
diff --git a/libexec/ulog-helper/ulog-helper.c b/libexec/ulog-helper/ulog-helper.c
new file mode 100644
index 0000000..ecf6507
--- /dev/null
+++ b/libexec/ulog-helper/ulog-helper.c
@@ -0,0 +1,81 @@
+/*-
+ * Copyright (c) 2009 Ed Schouten <ed@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <pwd.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+#include <ulog.h>
+
+/*
+ * This setuid helper utility writes user login records to disk.
+ * Unprivileged processes are not capable of writing records to utmp,
+ * wtmp and lastlog, but we do want to allow this for pseudo-terminals.
+ * Because a file descriptor to a pseudo-terminal master device can only
+ * be obtained by processes using the pseudo-terminal, we expect such a
+ * descriptor on stdin.
+ *
+ * It uses the real user ID of the calling process to determine the
+ * username.  It does allow users to log arbitrary hostnames.
+ */
+
+int
+main(int argc, char *argv[])
+{
+	const char *line;
+
+	/* Device line name. */
+	if ((line = ptsname(STDIN_FILENO)) == NULL)
+		return (EX_USAGE);
+
+	if ((argc == 2 || argc == 3) && strcmp(argv[1], "login") == 0) {
+		struct passwd *pwd;
+		const char *host = NULL;
+
+		/* Username. */
+		pwd = getpwuid(getuid());
+		if (pwd == NULL)
+			return (EX_OSERR);
+
+		/* Hostname. */
+		if (argc == 3)
+			host = argv[2];
+
+		if (ulog_login(line, pwd->pw_name, host) != 0)
+			return (EX_OSFILE);
+		return (EX_OK);
+	} else if (argc == 2 && strcmp(argv[1], "logout") == 0) {
+		if (ulog_logout(line) != 0)
+			return (EX_OSFILE);
+		return (EX_OK);
+	}
+
+	return (EX_USAGE);
+}