• Russ Cox's avatar
    hash: add MarshalBinary/UnmarshalBinary round trip + golden test for all implementations · 1d547e4a
    Russ Cox authored
    There are some basic tests in the packages implementing the hashes,
    but this one is meant to be comprehensive for the standard library
    as a whole.
    
    Most importantly, it locks in the current representations and makes
    sure that they do not change from release to release (and also, as a
    result, that future releases can parse the representations generated
    by older releases).
    
    The crypto/* MarshalBinary implementations are being changed
    in this CL to write only d.x[:d.nx] to the encoding, with zeros for
    the remainder of the slice d.x[d.nx:]. The old encoding wrote the
    whole d.x, but that exposed an internal detail: whether d.x is
    cleared after a full buffer is accumulated, and also whether d.x was
    used at all for previous blocks (consider 1-byte writes vs 1024-byte writes).
    The new encoding writes only what the decoder needs to know,
    nothing more.
    
    In fact the old encodings were arguably also a security hole,
    because they exposed data written even before the most recent
    call to the Reset method, data that clearly has no impact on the
    current hash and clearly should not be exposed. The leakage
    is clearly visible in the old crypto/sha1 golden test tables also
    being modified in this CL.
    
    Change-Id: I4e9193a3ec5f91d27ce7d0aa24c19b3923741416
    Reviewed-on: https://go-review.googlesource.com/82136
    Run-TryBot: Russ Cox <rsc@golang.org>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarJoe Tsai <thebrokentoaster@gmail.com>
    1d547e4a
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