79 lines
3.3 KiB
Diff
79 lines
3.3 KiB
Diff
From ced38e7dcb84cd11039fe6b7c078593c2a4968ff Mon Sep 17 00:00:00 2001
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From: Paul Kehrer <paul.l.kehrer@gmail.com>
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Date: Sun, 18 Dec 2016 18:36:05 -0600
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Subject: add memory limit check for scrypt
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fixes #3323
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---
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src/cryptography/hazmat/backends/openssl/backend.py | 8 +++++---
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tests/hazmat/primitives/test_scrypt.py | 19 +++++++++++++++++++
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2 files changed, 24 insertions(+), 3 deletions(-)
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diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
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index 71063c1..9e101a3 100644
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--- a/src/cryptography/hazmat/backends/openssl/backend.py
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+++ b/src/cryptography/hazmat/backends/openssl/backend.py
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@@ -143,6 +143,7 @@ class Backend(object):
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self._cipher_registry = {}
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self._register_default_ciphers()
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self.activate_osrandom_engine()
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+ self._scrypt_mem_limit = sys.maxsize // 2
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def openssl_assert(self, ok):
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return binding._openssl_assert(self._lib, ok)
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@@ -1894,9 +1895,10 @@ class Backend(object):
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def derive_scrypt(self, key_material, salt, length, n, r, p):
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buf = self._ffi.new("unsigned char[]", length)
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- res = self._lib.EVP_PBE_scrypt(key_material, len(key_material), salt,
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- len(salt), n, r, p, sys.maxsize // 2,
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- buf, length)
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+ res = self._lib.EVP_PBE_scrypt(
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+ key_material, len(key_material), salt, len(salt), n, r, p,
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+ self._scrypt_mem_limit, buf, length
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+ )
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self.openssl_assert(res == 1)
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return self._ffi.buffer(buf)[:]
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diff --git a/tests/hazmat/primitives/test_scrypt.py b/tests/hazmat/primitives/test_scrypt.py
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index 49b304e..450eb82 100644
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--- a/tests/hazmat/primitives/test_scrypt.py
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+++ b/tests/hazmat/primitives/test_scrypt.py
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@@ -22,10 +22,28 @@ vectors = load_vectors_from_file(
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os.path.join("KDF", "scrypt.txt"), load_nist_vectors)
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+def _skip_if_memory_limited(memory_limit, params):
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+ # Memory calc adapted from OpenSSL (URL split over 2 lines, thanks PEP8)
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+ # https://github.com/openssl/openssl/blob/6286757141a8c6e14d647ec733634a
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+ # e0c83d9887/crypto/evp/scrypt.c#L189-L221
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+ blen = int(params["p"]) * 128 * int(params["r"])
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+ vlen = 32 * int(params["r"]) * (int(params["n"]) + 2) * 4
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+ memory_required = blen + vlen
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+ if memory_limit < memory_required:
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+ pytest.skip("Test exceeds Scrypt memory limit. "
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+ "This is likely a 32-bit platform.")
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+
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+
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+def test_memory_limit_skip():
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+ with pytest.raises(pytest.skip.Exception):
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+ _skip_if_memory_limited(1000, {"p": 16, "r": 64, "n": 1024})
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+
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+
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@pytest.mark.requires_backend_interface(interface=ScryptBackend)
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class TestScrypt(object):
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@pytest.mark.parametrize("params", vectors)
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def test_derive(self, backend, params):
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+ _skip_if_memory_limited(backend._scrypt_mem_limit, params)
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password = params["password"]
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work_factor = int(params["n"])
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block_size = int(params["r"])
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@@ -77,6 +95,7 @@ class TestScrypt(object):
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@pytest.mark.parametrize("params", vectors)
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def test_verify(self, backend, params):
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+ _skip_if_memory_limited(backend._scrypt_mem_limit, params)
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password = params["password"]
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work_factor = int(params["n"])
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block_size = int(params["r"])
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