Re: (ITS#8230) [PATCH] totp: bug fixes and improvements

[peter@adpm.de]

Hi,

On Sunday, 30. August 2015 23:58:09 Howard Chu wrote:
> > Please note the run index i changed direction, which causes different
> > results because of  >>=.
> > 
> > In my tests [double checked before sending this mail] on an amd64 [little-
> > endian architecture], the patched version converts 0x3837363534333231 to
> > - "87654321"	in the !WORDS_BIGENDIAN case [unchanged]
> > - "12345678"	in the WORDS_BIGENDIAN case
> > [using the fact that  0x3N = "N"  for 0 <= N <=9]
> > To me that looks correct.
> > 
> > What issues did you see exactly?
> 
> That is exactly wrong. Given any integer input the string should be
> identical regardless of endianness. It should be "87654321" in both cases.
> With your patch, hashes will be incompatible between different machine
> architectures.

Please read my mail again!
I tested the WORDS_BIGENDIAN case on a *little-endian* architecture using the 
same data as the !WORDS_BIGENDIAN case.

In that case [i.e. testing on the "wrong-endian" architecture] the result *is 
expected* to come out in reversed order.
Otherwise it would end-up in wrong order on the "right-endian" architecture.

Do you agree?

If you don't, please hint me to some code that allows me to check and fix my 
code.

Best
Peter

-- 
Peter Marschall
peter@adpm.de