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
%#define VOLDUMPV2_OMITDIRS 1
const SIZE = 1024;
+const NMAXNSERVERS = 13;
struct volser_status {
afs_uint32 volID; /* Volume id--unique over all systems */
afs_uint64 dump_size;
};
-typedef replica manyDests<>;
+typedef replica manyDests<NMAXNSERVERS>;
typedef afs_int32 manyResults<>;
typedef transDebugInfo transDebugEntries<>;
typedef volintInfo volEntries<>;