svn commit: r234469 - head/libexec/ulog-helper

[Ed Schouten]

Author: ed
Date: Thu Apr 19 21:12:08 2012
New Revision: 234469
URL: http://svn.freebsd.org/changeset/base/234469

Log:
  Do a better job at determining the username of the login session.
  
  When multiple users share the same UID, the old code will simply pick an
  arbitrary username to attach to the utmpx entries. Make the code a bit
  more accurate by first checking whether getlogin() returns a username
  which corresponds to the uid of the calling process. If this fails,
  simply fall back to picking an arbitrary username.
  
  Reported by:	saurik on GitHub
  MFC after:	2 weeks

Modified:
  head/libexec/ulog-helper/ulog-helper.c

Modified: head/libexec/ulog-helper/ulog-helper.c
==============================================================================
--- head/libexec/ulog-helper/ulog-helper.c	Thu Apr 19 20:44:40 2012	(r234468)
+++ head/libexec/ulog-helper/ulog-helper.c	Thu Apr 19 21:12:08 2012	(r234469)
@@ -46,6 +46,28 @@ __FBSDID("$FreeBSD$");
  * username.  It does allow users to log arbitrary hostnames.
  */
 
+static const char *
+get_username(void)
+{
+	const struct passwd *pw;
+	const char *login;
+	uid_t uid;
+
+	/*
+	 * Attempt to determine the username corresponding to this login
+	 * session.  First, validate the results of getlogin() against
+	 * the password database.  If getlogin() returns invalid data,
+	 * return an arbitrary username corresponding to this uid.
+	 */
+	uid = getuid();
+	if ((login = getlogin()) != NULL && (pw = getpwnam(login)) != NULL &&
+	    pw->pw_uid == uid)
+		return (login);
+	if ((pw = getpwuid(uid)) != NULL)
+		return (pw->pw_name);
+	return (NULL);
+}
+
 int
 main(int argc, char *argv[])
 {
@@ -57,7 +79,7 @@ main(int argc, char *argv[])
 
 	if ((argc == 2 || argc == 3) && strcmp(argv[1], "login") == 0) {
 		/* Username. */
-		user = user_from_uid(getuid(), 1);
+		user = get_username();
 		if (user == NULL)
 			return (EX_OSERR);