New submission from Jack Lloyd: The XDR format requires integers to fit into 4 byte values. However (at least on x86-64) xdrlib will silently accept (and truncate) values larger than this (up to 2**64-1). Taking a (very brief) look at the xdrlib code, it appears this is actually a problem in the struct module, but I don't have the time (or interest) to trace through the _struct module code.
An example on an x86-64 machine (Python 2.4.3) of encoding 2**32 (which
will not fit in an XDR field) being silently truncated:
$ ./xdr.py
4294967296 -> 00000000 -> 0
An example of struct itself not detecting overflow:
>>> struct.pack("!I", 2**32)
'\x00\x00\x00\x00'
struct.pack will only throw an overflow error if a value >= 2**64 is
used, even if it is encoding into a field that is much smaller.
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components: Extension Modules
files: xdr.py
messages: 57939
nosy: lloyd
severity: normal
status: open
title: xdrlib fails to detect overflow (struct bug?)
type: behavior
versions: Python 2.4
Added file: http://bugs.python.org/file8825/xdr.py
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Tracker <[EMAIL PROTECTED]>
<http://bugs.python.org/issue1523>
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xdr.py
Description: Binary data
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