def verify(message, signature, pub_key):
"""Verifies that the signature matches the message.
The hash method is detected automatically from the signature.
:param message: the signed message. Can be an 8-bit string or a file-like
object. If ``message`` has a ``read()`` method, it is assumed to be a
file-like object.
:param signature: the signature block, as created with :py:func:`rsa.sign`.
:param pub_key: the :py:class:`adafruit_rsaPublicKey` of the person signing the message.
:raise VerificationError: when the signature doesn't match the message.
:returns: the name of the used hash.
"""
keylength = common.byte_size(pub_key.n)
encrypted = transform.bytes2int(signature)
decrypted = core.decrypt_int(encrypted, pub_key.e, pub_key.n)
clearsig = transform.int2bytes(decrypted, keylength)
# Get the hash method
method_name = _find_method_hash(clearsig)
message_hash = compute_hash(message, method_name)
# Reconstruct the expected padded hash
cleartext = HASH_ASN1[method_name] + message_hash
expected = _pad_for_signing(cleartext, keylength)
# Compare with the signed one
if expected != clearsig:
raise VerificationError("Verification failed")
return method_name
def find_signature_hash(signature, pub_key):
"""Returns the hash name detected from the signature.
If you also want to verify the message, use :py:func:`adafruit_rsaverify()` instead.
It also returns the name of the used hash.
:param signature: the signature block, as created with :py:func:`adafruit_rsasign`.
:param pub_key: the :py:class:`adafruit_rsaPublicKey` of the person signing the message.
:returns: the name of the used hash.
"""
keylength = common.byte_size(pub_key.n)
encrypted = transform.bytes2int(signature)
decrypted = core.decrypt_int(encrypted, pub_key.e, pub_key.n)
clearsig = transform.int2bytes(decrypted, keylength)
return _find_method_hash(clearsig)
