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Better hashlib check for Python 3.9 (#805)
* Better hashlib check for Python 3.9 In Python 3.9 and later, the hashlib function has a new keyword argument usedforsecurity to describe the usage of the hash. In that way, we can better identify the severity of the error. Previously, hashlib.md5 and the like were part of the blacklist check. For Python 3.9, it'll be part of the hashlib plugin so it can do more advanced checking of usedforsecurity. Signed-off-by: Eric Brown <browne@vmware.com> * Update hashlib_insecure_functions.py
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,118 @@ | ||
| # | ||
| # SPDX-License-Identifier: Apache-2.0 | ||
| r""" | ||
| ====================================================================== | ||
| B324: Test use of insecure md4, md5, or sha1 hash functions in hashlib | ||
| ====================================================================== | ||
| This plugin checks for the usage of the insecure MD4, MD5, or SHA1 hash | ||
| functions in ``hashlib``. The ``hashlib.new`` function provides | ||
| the ability to construct a new hashing object using the named algorithm. This | ||
| can be used to create insecure hash functions like MD4 and MD5 if they are | ||
| passed as algorithm names to this function. | ||
| For Python versions prior to 3.9, this check is similar to B303 blacklist | ||
| except that this checks for insecure hash functions created using | ||
| ``hashlib.new`` function. For Python version 3.9 and later, this check | ||
| does additional checking for usage of keyword usedforsecurity on all | ||
| function variations of hashlib. | ||
| :Example: | ||
| >> Issue: [B324:hashlib] Use of weak MD2, MD4, MD5, or SHA1 hash for | ||
| security. Consider usedforsecurity=False | ||
| Severity: High Confidence: High | ||
| CWE: CWE-327 (https://cwe.mitre.org/data/definitions/327.html) | ||
| Location: examples/hashlib_new_insecure_functions.py:3:0 | ||
| More Info: https://bandit.readthedocs.io/en/latest/plugins/b324_hashlib.html | ||
| 2 | ||
| 3 hashlib.new('md5') | ||
| 4 | ||
| .. seealso:: | ||
| - https://cwe.mitre.org/data/definitions/327.html | ||
| .. versionadded:: 1.5.0 | ||
| .. versionchanged:: 1.7.3 | ||
| CWE information added | ||
| """ # noqa: E501 | ||
| import sys | ||
|
|
||
| import bandit | ||
| from bandit.core import issue | ||
| from bandit.core import test_properties as test | ||
|
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||
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| def _hashlib_func(context): | ||
| if isinstance(context.call_function_name_qual, str): | ||
| qualname_list = context.call_function_name_qual.split(".") | ||
|
|
||
| if "hashlib" in qualname_list: | ||
| func = qualname_list[-1] | ||
| args = context.call_args | ||
| keywords = context.call_keywords | ||
| name = args[0] if args else keywords["name"] | ||
|
|
||
| if func in ("md4", "md5", "sha", "sha1"): | ||
| if keywords.get("usedforsecurity", "True") == "True": | ||
| return bandit.Issue( | ||
| severity=bandit.HIGH, | ||
| confidence=bandit.HIGH, | ||
| cwe=issue.Cwe.BROKEN_CRYPTO, | ||
| text="Use of weak MD2, MD4, MD5, or SHA1 hash " | ||
| "for security. Consider usedforsecurity=False", | ||
| lineno=context.node.lineno, | ||
| ) | ||
| elif func == "new": | ||
| if isinstance(name, str) and name.lower() in ( | ||
| "md4", | ||
| "md5", | ||
| "sha", | ||
| "sha1", | ||
| ): | ||
| if keywords.get("usedforsecurity", "True") == "True": | ||
| return bandit.Issue( | ||
| severity=bandit.HIGH, | ||
| confidence=bandit.HIGH, | ||
| cwe=issue.Cwe.BROKEN_CRYPTO, | ||
| text="Use of weak MD2, MD4, MD5, or SHA1 hash " | ||
| "for security. Consider usedforsecurity=False", | ||
| lineno=context.node.lineno, | ||
| ) | ||
|
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| def _hashlib_new(context): | ||
| if isinstance(context.call_function_name_qual, str): | ||
| qualname_list = context.call_function_name_qual.split(".") | ||
| func = qualname_list[-1] | ||
|
|
||
| if "hashlib" in qualname_list and func == "new": | ||
| args = context.call_args | ||
| keywords = context.call_keywords | ||
| name = args[0] if args else keywords["name"] | ||
| if isinstance(name, str) and name.lower() in ( | ||
| "md4", | ||
| "md5", | ||
| "sha", | ||
| "sha1", | ||
| ): | ||
| return bandit.Issue( | ||
| severity=bandit.MEDIUM, | ||
| confidence=bandit.HIGH, | ||
| cwe=issue.Cwe.BROKEN_CRYPTO, | ||
| text="Use of insecure MD2, MD4, MD5, or SHA1 hash " | ||
| "function.", | ||
| lineno=context.node.lineno, | ||
| ) | ||
|
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| @test.test_id("B324") | ||
| @test.checks("Call") | ||
| def hashlib(context): | ||
| if sys.version_info >= (3, 9): | ||
| return _hashlib_func(context) | ||
| else: | ||
| return _hashlib_new(context) |
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