FreeBSD-SA-97:02: Buffer overflow in lpd

[aleph1 () DFW NET (Aleph One)]

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=============================================================================
FreeBSD-SA-97:02                                            Security Advisory
                                                                FreeBSD, Inc.

Topic:          Buffer overflow in lpd

Category:       core
Module:         lpd
Announced:      1997-03-xxx
Affects:        FreeBSD 2.1.7 and earlier and FreeBSD 2.2 snapshots
                before 1997/02/25 suffer from this problem.
Corrected:      FreeBSD-current as of 1997/02/25
                FreeBSD 2.2 as of 1997/02/25
FreeBSD only:   yes

Patches:        ftp://freebsd.org/pub/CERT/patches/SA-97:02/

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I.   Background

     The lpd program is used to print local and remote print jobs.  It
     is standard software in the FreeBSD operating system.

II.  Problem Description

     The lpd program runs as root.  A remote attacker can exploit a
     buffer overflow to obtain root privs.

III. Impact

     Remote users can gain root privs.

IV.  Workaround

     The only workaround is to disable lpd, which will have the effect
     of removing the printing functionality from the system.  Since
     the buffer overflow happens before the connection is authenticated,
     using lpd's authentication methods will not affect the system
     vulnerability.

V.   Solution

     Apply the following patch, rebuild and install libc:

     (This patch can also be found on
        ftp://freebsd.org/pub/CERT/patches/SA-97:02/)

    Index: rcmd.c
    ===================================================================
    RCS file: /home/imp/FreeBSD/CVS/src/lib/libc/net/rcmd.c,v
    retrieving revision 1.3.4.4
    retrieving revision 1.3.4.5
    diff -u -r1.3.4.4 -r1.3.4.5
    --- rcmd.c  1997/02/09 06:57:54     1.3.4.4
    +++ rcmd.c  1997/02/26 06:14:11     1.3.4.5
    @@ -377,7 +377,8 @@
        if ((hp = gethostbyaddr((char *)&raddr, sizeof(u_long),
                                                        AF_INET)) == NULL)
                return (-1);
    -   strcpy(hname, hp->h_name);
    +   strncpy(hname, hp->h_name, sizeof(hname));
    +   hname[sizeof(hname) - 1] = '\0';

        while (fgets(buf, sizeof(buf), hostf)) {
                p = buf;

VI.   Thanks

     This problem was brought to light by Oliver Friedrichs
     <oliver () SECNET COM>.

=============================================================================
FreeBSD, Inc.

Web Site:                       http://www.freebsd.org/
Confidential contacts:          security-officer () freebsd org
PGP Key:                        ftp://freebsd.org/pub/CERT/public_key.asc
Security notifications:         security-notifications () freebsd org
Security public discussion:     security () freebsd org

Notice: Any patches in this document may not apply cleanly due to
        modifications caused by digital signature or mailer software.
        Please reference the URL listed at the top of this document
        for original copies of all patches if necessary.
=============================================================================

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