Add X963KDF from ANSI X9.63:2001

The implemention allows the use a Hash function to implement a KDF very
similar to ConcatKDFHash, just different enough to require a separate
derivation function.

Closes #2203

Signed-off-by: Simo Sorce <simo@redhat.com>

1 files changed, 120 insertions, 0 deletions

diff --git a/tests/hazmat/primitives/test_x963kdf.py b/tests/hazmat/primitives/test_x963kdf.py
new file mode 100644
index 00000000..d87a46b8
--- /dev/null
+++ b/tests/hazmat/primitives/test_x963kdf.py
@@ -0,0 +1,120 @@
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+
+from __future__ import absolute_import, division, print_function
+
+import binascii
+
+import pytest
+
+from cryptography.exceptions import (
+    AlreadyFinalized, InvalidKey, _Reasons
+)
+from cryptography.hazmat.backends.interfaces import HashBackend
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.kdf.x963kdf import X963KDF
+
+from ...utils import raises_unsupported_algorithm
+
+
+@pytest.mark.requires_backend_interface(interface=HashBackend)
+class TestX963KDF(object):
+    def test_length_limit(self, backend):
+        big_length = hashes.SHA256().digest_size * (2 ** 32 - 1) + 1
+
+        with pytest.raises(ValueError):
+            X963KDF(hashes.SHA256(), big_length, None, backend)
+
+    def test_already_finalized(self, backend):
+        xkdf = X963KDF(hashes.SHA256(), 16, None, backend)
+
+        xkdf.derive(b"\x01" * 16)
+
+        with pytest.raises(AlreadyFinalized):
+            xkdf.derive(b"\x02" * 16)
+
+    def test_derive(self, backend):
+        key = binascii.unhexlify(
+            b"96c05619d56c328ab95fe84b18264b08725b85e33fd34f08"
+        )
+
+        derivedkey = binascii.unhexlify(b"443024c3dae66b95e6f5670601558f71")
+
+        xkdf = X963KDF(hashes.SHA256(), 16, None, backend)
+
+        assert xkdf.derive(key) == derivedkey
+
+    def test_verify(self, backend):
+        key = binascii.unhexlify(
+            b"22518b10e70f2a3f243810ae3254139efbee04aa57c7af7d"
+        )
+
+        sharedinfo = binascii.unhexlify(b"75eef81aa3041e33b80971203d2c0c52")
+
+        derivedkey = binascii.unhexlify(
+            b"c498af77161cc59f2962b9a713e2b215152d139766ce34a776df11866a69bf2e"
+            b"52a13d9c7c6fc878c50c5ea0bc7b00e0da2447cfd874f6cf92f30d0097111485"
+            b"500c90c3af8b487872d04685d14c8d1dc8d7fa08beb0ce0ababc11f0bd496269"
+            b"142d43525a78e5bc79a17f59676a5706dc54d54d4d1f0bd7e386128ec26afc21"
+        )
+
+        xkdf = X963KDF(hashes.SHA256(), 128, sharedinfo, backend)
+
+        assert xkdf.verify(key, derivedkey) is None
+
+    def test_invalid_verify(self, backend):
+        key = binascii.unhexlify(
+            b"96c05619d56c328ab95fe84b18264b08725b85e33fd34f08"
+        )
+
+        xkdf = X963KDF(hashes.SHA256(), 16, None, backend)
+
+        with pytest.raises(InvalidKey):
+            xkdf.verify(key, b"wrong derived key")
+
+    def test_unicode_typeerror(self, backend):
+        with pytest.raises(TypeError):
+            X963KDF(
+                hashes.SHA256(),
+                16,
+                sharedinfo=u"foo",
+                backend=backend
+            )
+
+        with pytest.raises(TypeError):
+            xkdf = X963KDF(
+                hashes.SHA256(),
+                16,
+                sharedinfo=None,
+                backend=backend
+            )
+
+            xkdf.derive(u"foo")
+
+        with pytest.raises(TypeError):
+            xkdf = X963KDF(
+                hashes.SHA256(),
+                16,
+                sharedinfo=None,
+                backend=backend
+            )
+
+            xkdf.verify(u"foo", b"bar")
+
+        with pytest.raises(TypeError):
+            xkdf = X963KDF(
+                hashes.SHA256(),
+                16,
+                sharedinfo=None,
+                backend=backend
+            )
+
+            xkdf.verify(b"foo", u"bar")
+
+
+def test_invalid_backend():
+    pretend_backend = object()
+
+    with raises_unsupported_algorithm(_Reasons.BACKEND_MISSING_INTERFACE):
+        X963KDF(hashes.SHA256(), 16, None, pretend_backend)