OpenAFS Master Repository branch, master, updated. BP-openafs-stable-1_8_x-220-gd5816fd

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit 97b0ee4d9c9d069e78af2e046c7987aa4d3f9844
Author: Mark Vitale <mvitale@sinenomine.net>
Date:   Fri Jul 6 01:09:53 2018 -0400

    OPENAFS-SA-2018-003 volser: prevent unbounded input to AFSVolForwardMultiple
    
    AFSVolForwardMultiple is defined with an input parameter that is defined
    to XDR as an unbounded array of replica structs:
      typedef replica manyDests<>;
    
    RPCs with unbounded arrays as inputs are susceptible to remote
    denial-of-service (DOS) attacks.  A malicious client may submit an
    AFSVolForwardMultiple request with an arbitrarily large array, forcing
    the volserver to expend large amounts of network bandwidth, cpu cycles,
    and heap memory to unmarshal the input.
    
    Even though AFSVolForwardMultiple requires superuser authorization, this
    attack is exploitable by non-authorized actors because XDR unmarshalling
    happens long before any authorization checks can occur.
    
    Add a bounding constant (NMAXNSERVERS 13) to the manyDests input array.
    This constant is derived from the current OpenAFS vldb implementation, which
    is limited to 13 replica sites for a given volume by the layout (size) of the
    serverNumber, serverPartition, and serverFlags fields.
    
    [kaduk@mit.edu: explain why this constant is used]
    
    Change-Id: Id12c6a7da4894ec490691eb8791dcd3574baa416

 src/volser/volint.xg |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

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