Add rule for PyOpenSSL RSA and DSA key generation (#147)

* Checks function OpenSSL.crypto.PKey().generate_key
* Looks for weak keys being initialized

---------

Signed-off-by: Eric Brown <[email protected]>
Signed-off-by: Eric Brown <[email protected]>

precli/rules/python/third_party/PyYAML/yaml_load.py

@@ -44,7 +44,7 @@
 
 .. seealso::
 
- - `Deserialization of Untrusted Data in the PyYAML Module <https://docs.securesauce.dev/rules/PRE0518>`_
+ - `Deserialization of Untrusted Data in the PyYAML Module <https://docs.securesauce.dev/rules/PRE0519>`_
  - `PyYAML Documentation <https://pyyaml.org/wiki/PyYAMLDocumentation>`_
  - `CWE-502: Deserialization of Untrusted Data <https://cwe.mitre.org/data/definitions/502.html>`_
 

precli/rules/python/third_party/pycrypto/pycrypto_weak_cipher.py

@@ -75,7 +75,7 @@
 
     key = b'Very long and confidential key'
     nonce = Random.new().read(16)
-    tempkey = SHA.new(key+nonce).digest()
+    tempkey = SHA.new(key + nonce).digest()
     cipher = ARC4.new(tempkey)
     msg = nonce + cipher.encrypt(b'Open the pod bay doors, HAL')
 
@@ -97,7 +97,7 @@
 
     key = b'Very long and confidential key'
     nonce = Random.new().read(16)
-    tempkey = SHA.new(key+nonce).digest()
+    tempkey = SHA.new(key + nonce).digest()
     cipher = AES.new(tempkey)
     msg = nonce + cipher.encrypt(b'Open the pod bay doors, HAL')
 

precli/rules/python/third_party/pycrypto/pycrypto_weak_key.py

@@ -124,7 +124,7 @@ def analyze(self, context: dict, **kwargs: dict) -> Result:
                     message=self.message.format("DSA", 2048),
                     fixes=fixes,
                 )
-        elif call.name_qualified in "Crypto.PublicKey.RSA.generate":
+        elif call.name_qualified == "Crypto.PublicKey.RSA.generate":
             argument = call.get_argument(position=0, name="bits")
             bits = argument.value
 

precli/rules/python/third_party/pycryptodomex/pycryptodomex_weak_cipher.py

@@ -68,14 +68,14 @@
    :linenos:
    :emphasize-lines: 9
 
-    from Crypto.Cipher import ARC4
-    from Crypto.Hash import SHA
-    from Crypto import Random
+    from Cryptodome.Cipher import ARC4
+    from Cryptodome.Hash import SHA
+    from Cryptodome import Random
 
 
     key = b'Very long and confidential key'
     nonce = Random.new().read(16)
-    tempkey = SHA.new(key+nonce).digest()
+    tempkey = SHA.new(key + nonce).digest()
     cipher = ARC4.new(tempkey)
     msg = nonce + cipher.encrypt(b'Open the pod bay doors, HAL')
 
@@ -90,14 +90,14 @@
    :linenos:
    :emphasize-lines: 1,9
 
-    from Crypto.Cipher import AES
-    from Crypto.Hash import SHA
-    from Crypto import Random
+    from Cryptodome.Cipher import AES
+    from Cryptodome.Hash import SHA
+    from Cryptodome import Random
 
 
     key = b'Very long and confidential key'
     nonce = Random.new().read(16)
-    tempkey = SHA.new(key+nonce).digest()
+    tempkey = SHA.new(key + nonce).digest()
     cipher = AES.new(tempkey)
     msg = nonce + cipher.encrypt(b'Open the pod bay doors, HAL')
 

precli/rules/python/third_party/pycryptodomex/pycryptodomex_weak_key.py

@@ -39,7 +39,7 @@
    :linenos:
    :emphasize-lines: 4
 
-    from Crypto.PublicKey import DSA
+    from Cryptodome.PublicKey import DSA
 
 
     key = DSA.generate(1024)
@@ -55,7 +55,7 @@
    :linenos:
    :emphasize-lines: 4
 
-    from Crypto.PublicKey import DSA
+    from Cryptodome.PublicKey import DSA
 
 
     key = DSA.generate(2048)
@@ -124,7 +124,7 @@ def analyze(self, context: dict, **kwargs: dict) -> Result:
                     message=self.message.format("DSA", 2048),
                     fixes=fixes,
                 )
-        elif call.name_qualified in "Crypto.PublicKey.RSA.generate":
+        elif call.name_qualified == "Cryptodome.PublicKey.RSA.generate":
             argument = call.get_argument(position=0, name="bits")
             bits = argument.value
 

precli/rules/python/third_party/pyopenssl/pyopenssl_weak_key.py

@@ -0,0 +1,135 @@
+# Copyright 2023 Secure Saurce LLC
+r"""
+==================================================================
+Inadequate Encryption Strength Using Weak Keys in PyOpenSSL Module
+==================================================================
+
+Using weak key sizes for cryptographic algorithms like RSA and DSA can
+compromise the security of your encryption and digital signatures. Here's
+a brief overview of the risks associated with weak key sizes for these
+algorithms:
+
+RSA (Rivest-Shamir-Adleman):
+RSA is widely used for both encryption and digital signatures. Weak key sizes
+in RSA can be vulnerable to factorization attacks, such as the famous RSA-129
+challenge, which was factored in 1994 after 17 years of effort. Using small
+key sizes makes it easier for attackers to factor the modulus and recover
+the private key.
+
+It's generally recommended to use RSA key sizes of 2048 bits or more for
+security in the present day, with 3072 bits or higher being increasingly
+preferred for long-term security.
+
+DSA (Digital Signature Algorithm):
+DSA is used for digital signatures and relies on the discrete logarithm
+problem. Using weak key sizes in DSA can make it susceptible to attacks that
+involve solving the discrete logarithm problem, like the GNFS (General
+Number Field Sieve) algorithm.
+
+For DSA, key sizes of 2048 bits or more are recommended for modern security.
+Note that DSA is not as commonly used as RSA or ECC for new applications, and
+ECDSA (Elliptic Curve Digital Signature Algorithm) is often preferred due to
+its efficiency and strong security properties.
+
+-------
+Example
+-------
+
+.. code-block:: python
+   :linenos:
+   :emphasize-lines: 4
+
+    from Crypto.PublicKey import DSA
+
+
+    key = DSA.generate(1024)
+
+-----------
+Remediation
+-----------
+
+Its recommended to increase the key size to at least 2048 for DSA and RSA
+algorithms.
+
+.. code-block:: python
+   :linenos:
+   :emphasize-lines: 4
+
+    from Crypto.PublicKey import DSA
+
+
+    key = DSA.generate(2048)
+
+.. seealso::
+
+ - `Inadequate Encryption Strength Using Weak Keys in PyOpenSSL Module <https://docs.securesauce.dev/rules/PRE0518>`_
+ - `crypto — Generic cryptographic module — pyOpenSSL documentation <https://www.pyopenssl.org/en/latest/api/crypto.html#pkey-objects>`_
+ - `CWE-326: Inadequate Encryption Strength <https://cwe.mitre.org/data/definitions/326.html>`_
+
+.. versionadded:: 1.0.0
+
+"""  # noqa: E501
+from precli.core.config import Config
+from precli.core.level import Level
+from precli.core.location import Location
+from precli.core.result import Result
+from precli.rules import Rule
+
+
+class PyopensslWeakKey(Rule):
+    def __init__(self, id: str):
+        super().__init__(
+            id=id,
+            name="inadequate_encryption_strength",
+            full_descr=__doc__,
+            cwe_id=326,
+            message="Using {} key sizes less than {} bits is considered "
+            "vulnerable to attacks.",
+            targets=("call"),
+            wildcards={
+                "OpenSSL.crypto.*": [
+                    "PKey",
+                    "TYPE_DSA",
+                ],
+                "OpenSSL.*": [
+                    "crypto.PKey",
+                    "crypto.TYPE_DSA",
+                ],
+            },
+            config=Config(enabled=False),
+        )
+
+    def analyze(self, context: dict, **kwargs: dict) -> Result:
+        call = kwargs.get("call")
+
+        if call.name_qualified == "OpenSSL.crypto.PKey.generate_key":
+            arg0 = call.get_argument(position=0, name="type")
+            key_type = arg0.value
+
+            if key_type == "OpenSSL.crypto.TYPE_DSA":
+                key = "DSA"
+            elif key_type == "OpenSSL.crypto.TYPE_RSA":
+                key = "RSA"
+
+            arg1 = call.get_argument(position=1, name="bits")
+            bits = arg1.value
+
+            if key in ["DSA", "RSA"] and bits < 2048:
+                fixes = Rule.get_fixes(
+                    context=context,
+                    deleted_location=Location(node=arg1.node),
+                    description=f"Use a minimum key size of 2048 for "
+                    f"{key_type} keys.",
+                    inserted_content="2048",
+                )
+
+                return Result(
+                    rule_id=self.id,
+                    location=Location(
+                        file_name=context["file_name"],
+                        node=arg1.node,
+                    ),
+                    level=Level.ERROR if bits <= 1024 else Level.WARNING,
+                    message=self.message.format(key_type, 2048),
+                    fixes=fixes,
+                )

precli/rules/python/third_party/requests/no_certificate_verify.py

@@ -45,7 +45,7 @@
 
 .. seealso::
 
- - `Improper Certificate Validation Using Requests Module <https://docs.securesauce.dev/rules/PRE0519>`_
+ - `Improper Certificate Validation Using Requests Module <https://docs.securesauce.dev/rules/PRE0520>`_
  - `Requests HTTP for Humans™ <https://requests.readthedocs.io/en/latest/>`_
  - `CWE-295: Improper Certificate Validation <https://cwe.mitre.org/data/definitions/295.html>`_
 

setup.cfg

@@ -138,11 +138,14 @@ precli.rules.python =
     # precli/rules/python/third_party/pyopenssl/insecure_tls_method.py
     PRE0517 = precli.rules.python.third_party.pyopenssl.insecure_tls_method:InsecureTlsMethod
 
+    # precli/rules/python/third_party/pyopenssl/pyopenssl_weak_key.py
+    PRE0518 = precli.rules.python.third_party.pyopenssl.pyopenssl_weak_key:PyopensslWeakKey
+
     # precli/rules/python/third_party/PyYAML/yaml_load.py
-    PRE0518 = precli.rules.python.third_party.PyYAML.yaml_load:YamlLoad
+    PRE0519 = precli.rules.python.third_party.PyYAML.yaml_load:YamlLoad
 
     # precli/rules/python/third_party/requests/no_certificate_verify.py
-    PRE0519 = precli.rules.python.third_party.requests.no_certificate_verify:NoCertificateVerify
+    PRE0520 = precli.rules.python.third_party.requests.no_certificate_verify:NoCertificateVerify
 
 [build_sphinx]
 all_files = 1

tests/unit/rules/python/third_party/PyYAML/test_yaml_load.py

@@ -7,7 +7,7 @@
 from tests.unit.rules.python import test_case
 
 
-RULE_ID = "PRE0518"
+RULE_ID = "PRE0519"
 
 
 class YamlLoadTests(test_case.TestCase):

tests/unit/rules/python/third_party/pyopenssl/examples/generate_key_dsa_1024.py

@@ -0,0 +1,4 @@
+from OpenSSL import crypto
+
+
+crypto.PKey().generate_key(type=crypto.TYPE_DSA, bits=1024)

tests/unit/rules/python/third_party/pyopenssl/examples/generate_key_dsa_2048.py

@@ -0,0 +1,4 @@
+from OpenSSL import crypto
+
+
+crypto.PKey().generate_key(type=crypto.TYPE_DSA, bits=2048)

tests/unit/rules/python/third_party/pyopenssl/examples/generate_key_dsa_4096.py

@@ -0,0 +1,4 @@
+from OpenSSL import crypto
+
+
+crypto.PKey().generate_key(type=crypto.TYPE_DSA, bits=4096)

tests/unit/rules/python/third_party/pyopenssl/examples/generate_key_rsa_1024.py

@@ -0,0 +1,4 @@
+from OpenSSL import crypto
+
+
+crypto.PKey().generate_key(type=crypto.TYPE_RSA, bits=1024)

tests/unit/rules/python/third_party/pyopenssl/examples/generate_key_rsa_2048.py

@@ -0,0 +1,4 @@
+from OpenSSL import crypto
+
+
+crypto.PKey().generate_key(type=crypto.TYPE_RSA, bits=2048)

tests/unit/rules/python/third_party/pyopenssl/examples/generate_key_rsa_4096.py

@@ -0,0 +1,4 @@
+from OpenSSL import crypto
+
+
+crypto.PKey().generate_key(type=crypto.TYPE_RSA, bits=4096)

tests/unit/rules/python/third_party/requests/test_no_certificate_verify.py

@@ -7,7 +7,7 @@
 from tests.unit.rules.python import test_case
 
 
-RULE_ID = "PRE0519"
+RULE_ID = "PRE0520"
 
 
 class NoCertificateVerifyTests(test_case.TestCase):