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Thread: HTTP proxy vulnerabilty......

  1. #1
    jim Guest

    HTTP proxy vulnerabilty......

    I have found this , what do you think about ?

    Vulnerability Note VU#*50227
    Multiple vendors' HTTP proxy default configurations allow arbitrary TCP connections via HTTP CONNECT method
    Overview
    Multiple vendors' HTTP proxy services use insecure default configurations that could allow an attacker to make arbitrary TCP connections to internal hosts or external third-party hosts.
    I. Description
    HTTP proxy services commonly support the HTTP CONNECT method, which is designed to create a TCP connection that bypasses the normal application layer functionality of the proxy service. Typically, the HTTP CONNECT method is used to tunnel HTTPS connections through an HTTP proxy. The proxy service does not decrypt the HTTPS traffic, as this would violate the end-to-end security model used by TLS/SSL.
    The HTTP CONNECT method is described in an expired IETF Internet-Draft written in ***8 by Ari Luotonen. This document clearly explains the security risks associated with the HTTP CONNECT method:


    6. Security Considerations

    The CONNECT tunneling mechanism is really a lower-level function than
    the rest of the HTTP methods, kind of an escape mechanism for saying
    that the proxy should not interfere with the ***********, but merely
    forward the data. In the case of SSL tunneling, this is because the
    proxy should not need to know the entire URI that is being accessed
    (privacy, security), only the information that it explicitly needs
    (hostname and port number) in order to carry out its part.

    Due to this fact, the proxy cannot necessarily verify that the
    protocol being spoken is really what it is supposed to tunnel (SSL
    for example), and so the proxy configuration should explicitly limit
    allowed connections to well-known ports for that protocol (such as
    44* for HTTPS, 56* for SNEWS, as assigned by IANA, the Internet
    Assigned Numbers Authority).

    Ports of specific concern are such as the telnet port (port 2*), SMTP
    port (port 25) and many UNIX specific service ports (range 5*2-600).
    Allowing such tunnelled connections to e.g. the SMTP port might
    enable sending of uncontrolled E-mail ("spam").

    Many vendors' HTTP proxy services are configured by default to listen on all interfaces and to allow HTTP CONNECT method tunnels to any TCP port. Since most proxy services do not inspect application layer data in a tunneled connection, almost any TCP-based protocol may be forwarded through the proxy service. This creates an additional vulnerability in the case of HTTP anti-virus scanners and content filters that do not check the contents of an HTTP CONNECT method tunnel (VU#8682**). In addition, an attacker may be able to cause a denial of service by making recursive connections to a proxy service. Note that a wide variety of products including proxy servers, web servers, caches, firewalls, and content/virus scanners may provide HTTP proxy services.
    II. Impact
    The HTTP CONNECT method can be abused to establish arbitrary TCP connections through vulnerable proxy services. The CERT/** has received reports of this technique being used to connect to SMTP services (25/tcp) to initiate the delivery of unsolicited bulk email (spam). In a more dangerous case, an attacker may be able to establish a connection from a public network through a vulnerable proxy service to an internal network. If a proxy service allows recursive connections, an attacker may be able to cause a denial-of-service condition by consuming resources
    III. Solution
    Secure Proxy Configuration
    Examine the configuration of your proxy services to determine if they allow HTTP CONNECT method connections to arbitrary TCP ports and whether they allow connections from untrusted networks such as the Internet. Configure your proxy services to only allow connections from trusted networks to reasonably safe TCP ports such as HTTPS (44*/tcp). If possible, configure your proxy services not to allow recursive connections. For more information about specific products, check the Systems Affected section of this document, consult your product documentation, or contact your vendor.


    Systems Affected
    Vendor Status Date Updated
    Squid Not Vulnerable *2-Apr-2002
    Apache Not Vulnerable *2-Apr-2002
    Check Point Vulnerable *7-May-2002
    Junkbusters Not Vulnerable *2-Apr-2002
    Trend Micro Vulnerable *2-Apr-2002
    CacheFlow Inc. Unknown *2-Apr-2002
    Finjan Software Unknown *2-Apr-2002
    TIS Not Vulnerable *6-Apr-2002
    CERN Unknown **-Apr-2002
    Cisco Vulnerable *6-May-2002

  2. #2
    Unregistered Guest

    Re: HTTP proxy vulnerabilty......

    This is very nice story, but what the hell is the point jim ?

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