id	summary	reporter	owner	description	type	status	priority	milestone	version	resolution	keywords	cc	launchpad_bug
24	SHA256 failure on NetBSD with multiple segments	warner	bdew	"In [http://allmydata.org/trac/tahoe/ticket/738 tahoe#738], a user reported
hash-validation failures on a certain sized file on NetBSD/i386. Working
backwards, we were able to isolate the problem to a pycryptopp hash failure,
as demonstrated in the following test:

{{{
expected = SHA256(""a""*33 + ""a""*95).hexdigest()
s = SHA256(""a""*33)
s.update(""a""*95)
got = s.hexdigest()
assert expected==got, (expected, got)
}}}

It would appear that two updates, in which the total number of bytes is a
multiple of 128, and in which the first write is an odd number less than 64,
will cause this bug.

I'll attach a file with a test case to add to the pycryptopp test suite that
should exercise this problem.

This was observed in an 0.5.14 tree, on a box described as ""NetBSD fasty
4.99.7 NetBSD 4.99.7 ... i386"". The sha.cpp file was compiled with a command
line of: {{{cc -pthread -fno-strict-aliasing -DNDEBUG -O2 -I/usr/include -I/usr/pkg/include -fPIC -I. -I/usr/pkg/include/python2.5 -c cryptopp/sha.cpp -o build/temp.netbsd-4.99.7-i386-2.5/cryptopp/sha.o -w}}}. (note that inline assembly was probably enabled). ""cc"" was {{{cc (GCC) 4.1.2 20060628 prerelease (NetBSD nb2 20060711)}}}, and ""as"" was {{{GNU assembler 2.16.1}}}.


"	defect	closed	critical		0.5.1	fixed	integrity	bdew midnightmagic weidai