[Plugins-writers] Apache username

paul@private

Hi,

I notice this plugin is prone to false negatives on servers that do not 
return 404s. I suggest this patch which just checks if you get a 
DIFFERENT response for ~root than for ~anna_foo_fighter, which is the 
point of the vulnerability. It seems to work just fine and solves the 
false negative I had in mind.

Regards,

Paul

-- 
Paul Johnston, GSEC
Internet Security Specialist
Westpoint Limited
Albion Wharf, 19 Albion Street,
Manchester, M1 5LN
England
Tel: +44 (0)161 237 1028
Fax: +44 (0)161 237 1031
email: paul@private
web: www.westpoint.ltd.uk

#
# Copyright 2001 by Noam Rathaus <noamr@private>
#
# See the Nessus Scripts License for details
#
#

if(description)
{
 script_id(10766);
 script_bugtraq_id(3335);
 script_cve_id("CAN-2001-1013");
 script_version ("$Revision: 1.12 $");

 name["english"] = "Apache UserDir Sensitive Information Disclosure";
 script_name(english:name["english"]);

 desc["english"] = "An information leak occurs on Apache based web servers
whenever the UserDir module is enabled. The vulnerability allows an external
attacker to enumerate existing accounts by requesting access to their home
directory and monitoring the response.

Solution:
1) Disable this feature by changing 'UserDir public_html' (or whatever) to
'UserDir  disabled'.

Or

2) Use a RedirectMatch rewrite rule under Apache -- this works even if there
is no such  entry in the password file, e.g.:
RedirectMatch ^/~(.*)$ http://my-target-webserver.somewhere.org/$1

Or

3) Add into httpd.conf:
ErrorDocument 404 http://localhost/sample.html
ErrorDocument 403 http://localhost/sample.html
(NOTE: You need to use a FQDN inside the URL for it to work properly).

Additional Information:
http://www.securiteam.com/unixfocus/5WP0C1F5FI.html

Risk factor : Low";

 script_description(english:desc["english"]);

 summary["english"] = "Apache UserDir Sensitive Information Disclosure";
 script_summary(english:summary["english"]);

 script_category(ACT_GATHER_INFO);

 script_copyright(english:"This script is Copyright (C) 2001 SecuriTeam");
 family["english"] = "Misc.";
 script_family(english:family["english"]);

 script_dependencie("find_service.nes", "http_version.nasl");
 script_require_keys("www/apache");
 script_require_ports("Services/www", 80);
 exit(0);
}

#
# The script code starts here
#

include("http_func.inc");

port = get_http_port(default:80);

if (! get_port_state(port)) exit(0);

soc = http_open_socket(port);
if(! soc) exit(0);

soc = http_open_socket(port);
if (soc)
{
 req = http_head(item:"/~root", port:port);
 send(socket:soc, data:req);
 buf_valid = recv_line(socket:soc, length:1000);
 http_close_socket(soc);
}

soc = http_open_socket(port);
if (soc)
{
 req = http_head(item:"/~anna_foo_fighter", port:port);
 send(socket:soc, data:req);
 buf_invalid = recv_line(socket:soc, length:1000);
 http_close_socket(soc);
}

if (buf_valid != buf_invalid)
{
 security_note(port);
}

*** ../plugins/apache_username.nasl	2005-02-01 13:59:22.000000000 +0000
--- apache_username.nasl	2005-02-01 16:52:10.000000000 +0000
***************
*** 94,100 ****
   http_close_socket(soc);
  }

! if (("403 Forbidden" >< buf_valid) && ("404 Not Found" >< buf_invalid))
  {
   security_note(port);
  }
--- 94,100 ----
   http_close_socket(soc);
  }

! if (buf_valid != buf_invalid)
  {
   security_note(port);
  }

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