1 fetchmail-SA-2006-02: TLS enforcement problem/MITM attack/password exposure
3 Topics: fetchmail cannot enforce TLS
5 Author: Matthias Andree
8 Type: secret information disclosure
9 Impact: fetchmail can expose cleartext password over unsecure link
10 fetchmail may not detect man in the middle attacks
12 Credits: Isaac Wilcox (bug report, testing, collaboration on fix)
13 CVE Name: CVE-2006-5867
14 URL: http://fetchmail.berlios.de/fetchmail-SA-2006-02.txt
15 Project URL: http://fetchmail.berlios.de/
17 Affects: fetchmail releases <= 6.3.5
18 fetchmail release candidates 6.3.6-rc1, -rc2, -rc3
20 Not affected: fetchmail release candidate 6.3.6-rc4
21 fetchmail release 6.3.6
23 Corrected: 2006-11-26 fetchmail 6.3.6-rc4
29 2006-11-16 v0.01 internal review draft
30 2006-11-26 v0.02 revise failure cases, workaround, add acknowledgments
36 fetchmail is a software package to retrieve mail from remote POP2, POP3,
37 IMAP, ETRN or ODMR servers and forward it to local SMTP, LMTP servers or
38 message delivery agents.
40 fetchmail ships with a graphical, Python/Tkinter based configuration
41 utility named "fetchmailconf" to help the user create configuration (run
42 control) files for fetchmail.
45 2. Problem description and Impact
46 =================================
48 Fetchmail has has several nasty password disclosure vulnerabilities for
49 a long time. It was only recently that these have been found.
51 V1. sslcertck/sslfingerprint options should have implied "sslproto tls1"
52 in order to enforce TLS negotiation, but did not.
54 V2. Even with "sslproto tls1" in the config, fetches would go ahead
55 in plain text if STLS/STARTTLS wasn't available (not advertised,
56 or advertised but rejected).
58 V3. POP3 fetches could completely ignore all TLS options whether
59 available or not because it didn't reliably issue CAPA before
60 checking for STLS support, and it would only try STLS if it had seen
61 the server's advertisement.
63 V4. POP3 could fall back to using plain text passwords, even if strong
64 authentication had been configured.
66 V5. POP2 would not complain if strong authentication or TLS had been
69 This can cause eavesdroppers to obtain the password, depending on the
70 authentication scheme that is configured or auto-selected, and
71 subsequently impersonate somebody else when logging into the upstream
78 If your upstream offers SSLv3-wrapped service on a dedicated port,
79 use fetchmail --ssl --sslcertck --sslproto ssl3 on the command line,
80 or equivalent in the run control file. This encrypts the whole session.
86 Download and install fetchmail 6.3.6 or a newer stable release from
87 fetchmail's project site at
88 <http://developer.berlios.de/project/showfiles.php?group_id=1824>.
94 Isaac Wilcox has been a great help with testing the fixes and getting
98 A. Copyright, License and Warranty
99 ==================================
101 (C) Copyright 2006 by Matthias Andree, <matthias.andree@gmx.de>.
102 Some rights reserved.
104 This work is licensed under the Creative Commons
105 Attribution-NonCommercial-NoDerivs German License. To view a copy of
106 this license, visit http://creativecommons.org/licenses/by-nc-nd/2.0/de/
107 or send a letter to Creative Commons; 559 Nathan Abbott Way;
108 Stanford, California 94305; USA.
110 THIS WORK IS PROVIDED FREE OF CHARGE AND WITHOUT ANY WARRANTIES.
111 Use the information herein at your own risk.
113 END OF fetchmail-SA-2006-02.txt