Adds parameter safety checks to crypto wrappers

eth2deposit/utils/crypto.py

@@ -19,6 +19,8 @@ def SHA256(x: bytes) -> bytes:
 
 
 def scrypt(*, password: str, salt: str, n: int, r: int, p: int, dklen: int) -> bytes:
+    if n * r * p < 2**20:  # 128 MB memory usage
+        raise ValueError("The Scrypt parameters chosen are not secure.")
     if n >= 2**(128 * r / 8):
         raise ValueError("The given `n` should be less than `2**(128 * r / 8)`."
                          f"\tGot `n={n}`, r={r}, 2**(128 * r / 8)={2**(128 * r / 8)}")
@@ -29,6 +31,14 @@ def scrypt(*, password: str, salt: str, n: int, r: int, p: int, dklen: int) -> b
 def PBKDF2(*, password: bytes, salt: bytes, dklen: int, c: int, prf: str) -> bytes:
     if 'sha' not in prf:
         raise ValueError(f"String 'sha' is not in `prf`({prf})")
+    if 'sha256' in prf and c < 2**18:
+        '''
+        Verify the number of rounds of SHA256-PBKDF2. SHA512 bot checked as use in BIP39
+        does not require and therefore doesn't use safe parameters (c=2048).
+
+        Ref: https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki#from-mnemonic-to-seed
+        '''
+        raise ValueError("The PBKDF2 parameters chosen are not secure.")
     _hash = _sha256 if 'sha256' in prf else _sha512
     res = _PBKDF2(password=password, salt=salt, dkLen=dklen, count=c, hmac_hash_module=_hash)  # type: ignore
     return res if isinstance(res, bytes) else res[0]  # PyCryptodome can return Tuple[bytes]

tests/test_utils/test_crypto.py

@@ -10,11 +10,12 @@ from eth2deposit.utils.crypto import (
 @pytest.mark.parametrize(
     'n, r, valid',
     [
-        (int(2**(128 * 1 / 8)) // 2, 1, True),
-        (int(2**(128 * 1 / 8)), 1, False),
+        (int(2**(128 * 1 / 8)) * 2, 8, True),
+        (int(2**(128 * 1 / 8)) * 1, 8, False),  # Unsafe Parameters
+        (int(2**(128 * 1 / 8)) * 1, 1, False),  # Invalid n
     ]
 )
-def test_scrypt_invalid_n(n, r, valid):
+def test_scrypt_invalid_params(n, r, valid):
     if valid:
         scrypt(
             password="mypassword",
@@ -63,6 +64,34 @@ def test_PBKDF2_invalid_prf(prf, valid):
             )
 
 
+@pytest.mark.parametrize(
+    'count, prf, valid',
+    [
+        (2**18, "sha256", True),
+        (2**17, "sha256", False),
+        (2**11, "sha512", True),
+    ]
+)
+def test_PBKDF2_invalid_count(count, prf, valid):
+    if valid:
+        PBKDF2(
+            password="mypassword",
+            salt="mysalt",
+            dklen=64,
+            c=count,
+            prf=prf
+        )
+    else:
+        with pytest.raises(ValueError):
+            PBKDF2(
+                password="mypassword",
+                salt="mysalt",
+                dklen=64,
+                c=2048,
+                prf=prf,
+            )
+
+
 @pytest.mark.parametrize(
     'key, iv, valid',
     [