[Demexp-dev] New version of XDR RFC & some comments related to demexp

[David MENTRE]

Hello,

A new version of the IETF's RFC defining XDR has been published:
  http://www.rfc-editor.org/rfc/rfc4506.txt

No major modification has been made:
"""
2.  Changes from RFC 1832

   This document makes no technical changes to RFC 1832 and is published
   for the purposes of noting IANA considerations, augmenting security
   considerations, and distinguishing normative from informative
   references.
"""

Regarding security aspects, here are my comments:

"""
8.  Security Considerations

[...]
   Care must be take to properly encode and decode data to avoid
   attacks.  Known and avoidable risks include:

   *    Buffer overflow attacks.  Where feasible, protocols should be
        defined with explicit limits (via the "<" [ value ] ">" notation
        instead of "<" ">") on elements with variable-length data types.
        Regardless of the feasibility of an explicit limit on the
        variable length of an element of a given protocol, decoders need
        to ensure the incoming size does not exceed the length of any
        provisioned receiver buffers.
"""

   I have tried to define in all cases an explicit limit on elements'
   size.



"""
  *    Nul octets embedded in an encoded value of type string.
"""

   OCaml is not sensitive to this kind of issue.



"""
   *    Decoding of characters in strings that are legal ASCII
        characters but nonetheless are illegal for the intended
        application.
"""

   That might be an issue in the future, especially related to
   classification or links.



"""
   *    Denial of service caused by recursive decoder or encoder
        subroutines.
"""

   I trust Gerd to have correctly programmed the XDR decoder. I haven't
   checked his code.


Of course, anybody is free to make an independent review of the
code. :-)


Best wishes,
d.
-- 
pub  1024D/A3AD7A2A 2004-10-03 David MENTRE <address@hidden>
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