Bug#212030: apache: mod_proxy allows the world to use it - letting spammers bounce through it

[Matt Zimmerman <mdz@debian.org>]

tags 212030 - security
thanks

On Sun, Sep 21, 2003 at 10:57:22PM +0300, Amos Shapira wrote:

> My guess is that the spammer somehow causes Apache to redirect SMTP connections
> through its mod_proxy.
> 
> The relevant parts in httpd.conf were:
> --------------------------------------------------------
> LoadModule proxy_module /usr/lib/apache/1.3/libproxy.so
> ....
> <IfModule mod_proxy.c>
> 
>    # Proxy Server directives. Uncomment the following lines to
>    # enable the proxy server:
>    #
>    <IfModule mod_proxy.c>
>    ProxyRequests On
> 
>    <Directory proxy:*>
>        Order deny,allow
>        #Deny from all
>        #Allow from .your_domain.com
>        Allow from all
>    </Directory>
> </IfModule>
> --------------------------------------------------------
> 
> I think this is a security bug (can cause DoS) because

These lines are not present in the provided example configuration.  The
example reads:

#
# Proxy Server directives. Uncomment the following lines to
# enable the proxy server:
#
#<IfModule mod_proxy.c>
#    ProxyRequests On

#    <Directory proxy:*>
#        Order deny,allow
#        Deny from all
#        Allow from .your-domain.com
#    </Directory>

    #
    # Enable/disable the handling of HTTP/1.1 "Via:" headers.
    # ("Full" adds the server version; "Block" removes all outgoing Via: headers
)
    # Set to one of: Off | On | Full | Block
    #
#    ProxyVia On

    #
    # To enable the cache as well, edit and uncomment the following lines:
    # (no cacheing without CacheRoot)
    #
#    CacheRoot "@@ServerRoot@@/proxy"
#    CacheSize 5
#    CacheGcInterval 4
#    CacheMaxExpire 24
#    CacheLastModifiedFactor 0.1
#    CacheDefaultExpire 1
#    NoCache a-domain.com another-domain.edu joes.garage-sale.com

#</IfModule>
# End of proxy directives.

You seem to have explicitly added "Allow from all", thus configuring it as an
open proxy.  The security issue is with your configuration, not with apache.

-- 
 - mdz