[Bug 110] New: bogus error messages in lastlog_get_entry()

[bugzilla-daemon at mindrot.org]

http://bugzilla.mindrot.org/show_bug.cgi?id=110

           Summary: bogus error messages in lastlog_get_entry()
           Product: Portable OpenSSH
           Version: -current
          Platform: ix86
        OS/Version: Linux
            Status: NEW
          Severity: minor
          Priority: P2
         Component: sshd
        AssignedTo: openssh-unix-dev at mindrot.org
        ReportedBy: peak at argo.troja.mff.cuni.cz


When sshd tries to read beyond the end of lastlog, e.g. when logging to a
high-uid user that has never logged in yet, atomicio() returns 0 and
lastlog_get_entry() generates a bogus error message for errno==0 (e.g.
"lastlog_get_entry: Error reading from /var/log/lastlog: Success"). The
following patch prevents it. Also, I made an attempt to report partial reads in
a proper way.

diff -urN openssh-3.0.2p1.old/loginrec.c openssh-3.0.2p1/loginrec.c
--- openssh-3.0.2p1.old/loginrec.c	Tue Oct 30 03:50:40 2001
+++ openssh-3.0.2p1/loginrec.c	Tue Feb 12 23:16:43 2002
@@ -1486,15 +1486,23 @@
 lastlog_get_entry(struct logininfo *li)
 {
 	struct lastlog last;
-	int fd;
+	int fd, r;
 
 	if (!lastlog_openseek(li, &fd, O_RDONLY))
 		return 0;
 
-	if (atomicio(read, fd, &last, sizeof(last)) != sizeof(last)) {
+	r = atomicio(read, fd, &last, sizeof(last));
+	if (r == 0) {
+		/* no recorded login */
+		memset(&last, '\0', sizeof(last));
+	} else if (r != sizeof(last)) {
 		close(fd);
-		log("lastlog_get_entry: Error reading from %s: %s",
-		    LASTLOG_FILE, strerror(errno));
+		if (r == -1)
+			log("lastlog_get_entry: Error reading from %s: %s",
+			    LASTLOG_FILE, strerror(errno));
+		else
+			log("lastlog_get_entry: Error reading from %s: read %d bytes, expected %d",
+			    LASTLOG_FILE, r, sizeof(last));
 		return 0;
 	}



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