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Reject oversized digest_size in generichash_blake2b_final() #965

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Reject oversized digest_size in generichash_blake2b_final() #965

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6 changes: 6 additions & 0 deletions src/nacl/bindings/crypto_generichash.py
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Original file line number Diff line number Diff line change
Expand Up @@ -271,6 +271,12 @@ def generichash_blake2b_final(state: Blake2State) -> bytes:
raising=exc.TypeError,
)

ensure(
state.digest_size <= crypto_generichash_BYTES_MAX,
_TOOBIG.format("Digest_size", crypto_generichash_BYTES_MAX),
raising=exc.ValueError,
)

_digest = ffi.new("unsigned char[]", crypto_generichash_BYTES_MAX)
rc = lib.crypto_generichash_blake2b_final(
state._statebuf, _digest, state.digest_size
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17 changes: 17 additions & 0 deletions tests/test_generichash.py
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Original file line number Diff line number Diff line change
Expand Up @@ -155,6 +155,23 @@ def test_expected_bindings_level_pickle_and_copy_failures():
copy.copy(st)


def test_generichash_blake2b_final_rejects_oversized_directly_constructed_state():
# Regression test for https://github.com/pyca/pynacl/issues/964
# A Blake2State constructed directly (bypassing
# generichash_blake2b_init()'s parameter validation) with an
# out-of-range digest_size used to crash the process with SIGABRT
# inside libsodium instead of raising a Python exception.
from nacl.bindings.crypto_generichash import (
Blake2State,
crypto_generichash_BYTES_MAX,
generichash_blake2b_final,
)

state = Blake2State(crypto_generichash_BYTES_MAX + 1)
with pytest.raises(exc.ValueError):
generichash_blake2b_final(state)


@pytest.mark.parametrize(
["message", "key", "outlen", "output"], blake2_reference_vectors()
)
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