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BF: disallow exploiting of non-greedy .* in previous fix by providing too long rhost -- do not impose length limits for user-provided input 

since daemon might eventually change reported length and we would need to adjust anyways.  So limiting
in length does not provide additional security but allows for a possible injection vector
pull/426/head
Yaroslav Halchenko 2013-11-08 10:06:24 -08:00
parent abb012ae5c
commit 750e0c1e3d
3 changed files with 6 additions and 4 deletions
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2
ChangeLog
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@ -78,7 +78,7 @@ some obscure corner of the Internet.
* filter.d/recidive -- support f2b syslog target and anchor regex at start
* filter.d/mysqld-auth.conf - mysql can use syslog
* filter.d/sshd - regex enhancements to support openssh-6.3. Closes Debian
bug #722970
bug #722970. Thanks Colin Watson for the regex analysis.
* filter.d/wuftpd - regex enhancements to support pam and wuftpd. Closes
Debian bug #665925
Rolf Fokkens

2
config/filter.d/sshd.conf
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@ -14,7 +14,7 @@ _daemon = sshd
failregex = ^%(__prefix_line)s(?:error: PAM: )?[aA]uthentication (?:failure|error) for .* from <HOST>( via \S+)?\s*$
^%(__prefix_line)s(?:error: PAM: )?User not known to the underlying authentication module for .* from <HOST>\s*$
^%(__prefix_line)sFailed \S+ for .*? from <HOST>(?: port \d*)?(?: ssh\d*)?(: (ruser .{0,100}|(\S+ ID \S+ \(serial \d+\) CA )?\S+ %(__md5hex)s(, client user ".{0,100}", client host ".{0,100}")?))?\s*$
^%(__prefix_line)sFailed \S+ for .*? from <HOST>(?: port \d*)?(?: ssh\d*)?(: (ruser .*|(\S+ ID \S+ \(serial \d+\) CA )?\S+ %(__md5hex)s(, client user ".*", client host ".*")?))?\s*$
^%(__prefix_line)sROOT LOGIN REFUSED.* FROM <HOST>\s*$
^%(__prefix_line)s[iI](?:llegal|nvalid) user .* from <HOST>\s*$
^%(__prefix_line)sUser .+ from <HOST> not allowed because not listed in AllowUsers\s*$

6
testcases/files/logs/sshd
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@ -95,6 +95,8 @@ Sep 29 17:15:02 spaceman sshd[12946]: Failed hostbased for dan from 127.0.0.1 po
# failJSON: { "time": "2004-09-29T17:15:02", "match": true , "host": "127.0.0.1" }
Sep 29 17:15:02 spaceman sshd[12946]: Failed hostbased for dan from 127.0.0.1 port 45785 ssh2: DSA 01:c0:79:41:91:31:9a:7d:95:23:91:ac:b1:6d:59:81, client user "dan", client host "localhost.localdomain"
# Injecting into rhost for the format of OpenSSH >=6.3
# failJSON: { "time": "2004-09-29T17:15:02", "match": true , "host": "127.0.0.1" }
# failJSON: { "time": "2004-09-29T17:15:02", "match": true , "host": "127.0.0.1", "desc": "Injecting into rhost for the format of OpenSSH >=6.3" }
Sep 29 17:15:02 spaceman sshd[12946]: Failed password for user from 127.0.0.1 port 20000 ssh1: ruser from 1.2.3.4
# failJSON: { "time": "2004-09-29T17:15:02", "match": true , "host": "127.0.0.1", "desc": "Injecting while exhausting initially present {0,100} match length limits set for ruser etc" }
Sep 29 17:15:02 spaceman sshd[12946]: Failed password for user from 127.0.0.1 port 20000 ssh1: ruser XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX from 1.2.3.4