"An 'Asp.Net' accident waiting to happen" - Draft article

Discussion in 'ASP .Net Security' started by Dinis Cruz, Oct 30, 2003.

  1. Dinis Cruz

    Dinis Cruz Guest

    Hello

    Please see bellow the final draft of an article soon to be published.

    I would appreciate your comments and corrections of anything that I
    might have got wrong.

    Best regards

    Dinis Cruz


    -------------------------------------


    An 'Asp.Net' accident waiting to happen

    I would like to call the attention of the Asp.Net Community and
    Microsoft to an accident waiting to happen. In a time where Security
    is finally being taken seriously by Microsoft, their focus is still in
    adding features to products and not making the existent products
    secure.

    The accident will be the wide spread exploitation of websites hosted
    in shared hosting environments (such as ISPs). The problems described
    next will also affect any major Asp.Net application, but their
    problems will be dealt privately and lessons will not be learnt by the
    community.

    Asp.Net is the latest and most powerful web application development
    tool produced by Microsoft. Although it is a major technological
    advance from its predecessors (Asp, ISAPI, Web Classes, Custom COM
    Objects developed in Visual Studio 6, etc.) it is also very dangerous.

    The .Net framework (which is fully implemented in Asp.Net) is very
    feature rich and powerful. It provides the developer (i.e. development
    team) with a huge array of tools, objects and methods that make their
    web application development a quick, easy and effective process.

    Microsoft, knowing that security is becoming more and more a central
    issue for end clients, included in the .Net framework several
    technologies that allow the creation and deployment of secure
    applications. The most important are:

    - Code Access Security (CAS)
    - Ability to deploy APTCA (AllowPartiallyTrustedCallersAttribute)
    assemblies in the GAC (Global Assembly Cache)
    - Built in Encryption technology (DPAPI)
    - Several methods to implement Secured Database Accesses
    - Several authentication methods and Build-in Impersonation features
    - Extended used of Role Based Security (used in conjunction with
    Windows server security features)

    IIS 6 web server and windows 2003 also provide some tools to deploy
    secure websites:

    - Applications pools (allow the execution of each website under the
    rights on a unique (low privileged) user)
    - Better management of process and threads

    These tools should allow the developer to create secure applications
    that could be deployed in secure servers.

    The problem is that today, the development and deployment of secure
    web applications in secure web servers is almost impossible because:

    - Although CAS (Code Access Security) could be used to limit what a
    web application could 'do' on the host server, in the real world it
    doesn't work. Any web application that is executed in 'Partially
    trusted' environments (i.e. not in 'Full Trust') will not have access
    to fundamental Asp.Net features such as: Database connectivity using
    OleDB or ODBC, use of COM objects and many other important features.

    - If a developer wants to use the powerful Asp.Net development
    environment in a quick, easy and effective way, the solution is to run
    its Asp.Net code in 'Full Trust' environments. The problem is that
    most security tools and technologies previously mentioned only work
    effectively in 'Partially trusted' environments

    - Most ISPs that provide Shared Hosting environments allow their
    hosted websites to execute with 'Full Trust' rights. This means that
    even if a developer manages to get their web application to work in
    'Partially trusted' environments, he would not be able to find a
    secure host for it. The only way around this is to purchase a
    dedicated server, which is also very dangerous, because it would then
    be the developer's responsibility to securely configure and manage it.

    - Most developers will store sensitive information (such as usernames
    and passwords) in an unencrypted format in configuration files stored
    in their website's folders (for example in Web.config). This happens
    because the current version of Asp.Net doesn't provide a quick,
    effective and scalable solution to store encrypted data in the
    registry (or other secure location)

    - In a shared hosting environment everybody has access to everybody's
    temporary files (i.e. the 'Asp.Net Temporary files' folder) and in
    Asp.Net all code is initially compiled into IL (Intermediate Language)
    which is easily decompiled into VB or C#. This means that every user
    with access to a valid account in a shared hosting environment can
    read the source code (.aspx, vb, cs or dll) of every website hosted in
    that server.

    - In 'Full Trust' environments, the developer has access to the entire
    windows 32 API and (using reflection) all .Net functions (private or
    public). This means that it is easy to write code that: Executes
    commands on the server (i.e. creates processes), lists usernames,
    lists running process, list installed services, open TCP connections,
    etc...

    Fundamentally, the problem is that the current version of the .Net
    Framework (version 1.14) doesn't allow the creation of secure hosting
    environments.

    Unless (of course), one is prepared to developed 'Partially Trusted'
    web applications.

    This could be done by using the reduced (and very limited) 'Partially
    Trusted' Asp.Net development environment, or by spending an extra 50%
    to 100% development time in creating secure strong name assemblies
    that can be published in the server's GAC (although this is not very
    practical for ISPs).

    Today (Oct/2003):

    1) There are hundreds of ISPs providing 'Full Trust' Asp.Net shared
    hosting services

    2) Microsoft is not publicly acknowledging (as a problem or security
    vulnerability) the fact that these ISPs have no alternative but to
    provide 'Full Trust' shared hosting environments. And consequently is
    not focused on providing or developing a solution.

    3) Microsoft is focused in developing the next version of Asp.Net
    (version 1.2) which will have even more features and will be even more
    powerful (although Microsoft says that the new version will be more
    secure)

    4) Malicious users have already realized that the current windows
    based ISP's hosting environments are insecure and easy to exploit.
    Although most incidents are still private and the ISPs will not
    publicly acknowledge their existence, recently one case was so serious
    that it got some press attention: See the "Interland Security
    Incident" story where a malicious user injected malicious code in
    several websites hosted by Interland's shared hosting servers. This
    code used known bugs in the website's visitors Internet Explorer Web
    Browser which (description from the Wired article) "... Web surfers
    who have visited the compromised sites might get a surprise on their
    next phone bill when they discover expensive calls made to 900
    numbers. Others could also find themselves party to a
    denial-of-service attack launched against another computer...". For
    more details read this article: "Wired.com : 'Security holes Vex Web
    Hosting Firm' : http://www.wired.com/news/business/0,1367,60303,00.html"
    and this "news.com : 'Web Hosting Company confirms hack attack' :
    http://news.com.com/2100-1002-5076050.html" and this
    "ComputerWorld.com : 'Security breach at Web host leaves sites at
    risk' : http://www.computerworld.com/securitytopics/security/story/0,10801,84675,00.html".

    5) The ISPs are telling their clients that their shared hosting
    servers are secure and the clients believe them (reinforced by the
    fact that Microsoft doesn't acknowledge the problem). This is quite
    important because if the clients where aware of these problems, they
    would demand (and possibly pay more for) secure environments to host
    their websites.

    The massive exploitation of these vulnerabilities by malicious users
    is just a matter of time. In my view the most dangerous problem is the
    fact that (today) there is no real alternative (i.e. solution) to
    securely host Asp.Net websites in a shared hosting environment.

    If in a near future a major security incident occurs (with widespread
    media coverage) and, the ISPs had to (or where forced to) change the
    current 'Full Trust' level to a 'Partially trusted' level, the side
    effect would be that most (if not all) hosted Asp.Net websites would
    stop working or would seriously malfunction.

    In conclusion, it is an 'Asp.Net' accident waiting to happen!

    Dinis Cruz is a Security Consultant currently working for several UK
    governmental Departments, International Corporations and ISPs. He is
    specialist in .Net Security and is the creator and main developer of
    the Open Source web application ANSA (Asp.Net Security Consultant). He
    is also the managing director of DDPlus; a UK based IT Security
    Company (www.ddplus.net). Dinis can be contacted on
    Dinis Cruz, Oct 30, 2003
    #1
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