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Merge pull request #564 from taus-semmle/python-insecure-ssl-version
Python: Check for insecure versions of SSL and TLS.
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‎change-notes/1.20/analysis-python.md‎

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# Improvements to Python analysis
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## General improvements
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> Changes that affect alerts in many files or from many queries
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> For example, changes to file classification
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## New queries
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| **Query** | **Tags** | **Purpose** |
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|-----------------------------|-----------|--------------------------------------------------------------------|
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| Default version of SSL/TLS may be insecure (`py/insecure-default-protocol`) | security, external/cwe/cwe-327 | Finds instances where an insecure default protocol may be used. Results are shown on LGTM by default. |
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| Use of insecure SSL/TLS version (`py/insecure-protocol`) | security, external/cwe/cwe-327 | Finds instances where a known insecure protocol has been specified. Results are shown on LGTM by default. |
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## Changes to existing queries
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| **Query** | **Expected impact** | **Change** |
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|----------------------------|------------------------|------------------------------------------------------------------|
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## Changes to code extraction
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* *Series of bullet points*
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## Changes to QL libraries
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* *Series of bullet points*

‎python/ql/src/Security/CWE-327/InsecureDefaultProtocol.qhelp‎

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p> The <code>ssl</code> library defaults to an insecure version of
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SSL/TLS when no specific protocol version is specified. This may leave
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the connection vulnerable to attack.
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</p>
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</overview>
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<recommendation>
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<p>
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Ensure that a modern, strong protocol is used. All versions of SSL,
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and TLS 1.0 are known to be vulnerable to attacks. Using TLS 1.1 or
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above is strongly recommended. If no explicit
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<code>ssl_version</code> is specified, the default
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<code>PROTOCOL_TLS</code> is chosen. This protocol is insecure and
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should not be used.
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</p>
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</recommendation>
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<example>
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<p>
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The following code shows two different ways of setting up a connection
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using SSL or TLS. They are both potentially insecure because the
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default version is used.
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</p>
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<sample src="examples/insecure_default_protocol.py" />
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<p>
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Both of the cases above should be updated to use a secure protocol
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instead, for instance by specifying
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<code>ssl_version=PROTOCOL_TLSv1_1</code> as a keyword argument.
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</p>
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<p>
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Note that <code>ssl.wrap_socket</code> has been deprecated in
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Python 3.7. A preferred alternative is to use
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<code>ssl.SSLContext</code>, which is supported in Python 2.7.9 and
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3.2 and later versions.
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</p>
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</example>
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<references>
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<li>Wikipedia: <a href="https://en.wikipedia.org/wiki/Transport_Layer_Security"> Transport Layer Security</a>.</li>
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<li>Python 3 documentation: <a href="https://docs.python.org/3/library/ssl.html#ssl.SSLContext"> class ssl.SSLContext</a>.</li>
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<li>Python 3 documentation: <a href="https://docs.python.org/3/library/ssl.html#ssl.wrap_socket"> ssl.wrap_socket</a>.</li>
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</references>
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</qhelp>

‎python/ql/src/Security/CWE-327/InsecureDefaultProtocol.ql‎

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/**
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* @name Default version of SSL/TLS may be insecure
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* @description Leaving the SSL/TLS version unspecified may result in an insecure
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* default protocol being used.
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* @id py/insecure-default-protocol
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* @kind problem
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* @problem.severity warning
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* @precision high
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* @tags security
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* external/cwe/cwe-327
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*/
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import python
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FunctionObject ssl_wrap_socket() {
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result = any(ModuleObject ssl | ssl.getName() = "ssl").getAttribute("wrap_socket")
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}
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ClassObject ssl_Context_class() {
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result = any(ModuleObject ssl | ssl.getName() = "ssl").getAttribute("SSLContext")
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}
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CallNode unsafe_call(string method_name) {
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result = ssl_wrap_socket().getACall() and
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method_name = "deprecated method ssl.wrap_socket"
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or
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result = ssl_Context_class().getACall() and
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method_name = "ssl.SSLContext"
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}
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from CallNode call, string method_name
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where
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call = unsafe_call(method_name) and
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not exists(call.getArgByName("ssl_version"))
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select call, "Call to " + method_name + " does not specify a protocol, which may result in an insecure default being used."
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‎python/ql/src/Security/CWE-327/InsecureProtocol.qhelp‎

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>
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Using a broken or weak cryptographic protocol may make a connection
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vulnerable to interference from an attacker.
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</p>
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</overview>
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<recommendation>
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<p>
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Ensure that a modern, strong protocol is used. All versions of SSL,
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and TLS 1.0 are known to be vulnerable to attacks. Using TLS 1.1 or
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above is strongly recommended.
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</p>
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</recommendation>
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<example>
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<p>
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The following code shows a variety of ways of setting up a
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connection using SSL or TLS. They are all insecure because of the
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version specified.
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</p>
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<sample src="examples/insecure_protocol.py" />
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<p>
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All cases should be updated to use a secure protocol, such as
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<code>PROTOCOL_TLSv1_1</code>.
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</p>
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<p>
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Note that <code>ssl.wrap_socket</code> has been deprecated in
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Python 3.7. A preferred alternative is to use
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<code>ssl.SSLContext</code>, which is supported in Python 2.7.9 and
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3.2 and later versions.
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</p>
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</example>
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<references>
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<li>Wikipedia: <a href="https://en.wikipedia.org/wiki/Transport_Layer_Security"> Transport Layer Security</a>.</li>
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<li>Python 3 documentation: <a href="https://docs.python.org/3/library/ssl.html#ssl.SSLContext"> class ssl.SSLContext</a>.</li>
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<li>Python 3 documentation: <a href="https://docs.python.org/3/library/ssl.html#ssl.wrap_socket"> ssl.wrap_socket</a>.</li>
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<li>pyOpenSSL documentation: <a href="https://pyopenssl.org/en/stable/api/ssl.html"> An interface to the SSL-specific parts of OpenSSL</a>.</li>
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</references>
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</qhelp>

‎python/ql/src/Security/CWE-327/InsecureProtocol.ql‎

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/**
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* @name Use of insecure SSL/TLS version
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* @description Using an insecure SSL/TLS version may leave the connection vulnerable to attacks.
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* @id py/insecure-protocol
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* @kind problem
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* @problem.severity warning
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* @precision high
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* @tags security
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* external/cwe/cwe-327
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*/
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import python
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FunctionObject ssl_wrap_socket() {
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result = the_ssl_module().getAttribute("wrap_socket")
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}
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ClassObject ssl_Context_class() {
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result = the_ssl_module().getAttribute("SSLContext")
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}
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string insecure_version_name() {
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// For `pyOpenSSL.SSL`
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result = "SSLv2_METHOD" or
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result = "SSLv23_METHOD" or
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result = "SSLv3_METHOD" or
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result = "TLSv1_METHOD" or
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// For the `ssl` module
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result = "PROTOCOL_SSLv2" or
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result = "PROTOCOL_SSLv3" or
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result = "PROTOCOL_SSLv23" or
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result = "PROTOCOL_TLS" or
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result = "PROTOCOL_TLSv1"
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}
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private ModuleObject the_ssl_module() {
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result = any(ModuleObject m | m.getName() = "ssl")
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}
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private ModuleObject the_pyOpenSSL_module() {
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result = any(ModuleObject m | m.getName() = "pyOpenSSL.SSL")
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}
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/* A syntactic check for cases where points-to analysis cannot infer the presence of
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* a protocol constant, e.g. if it has been removed in later versions of the `ssl`
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* library.
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*/
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predicate probable_insecure_ssl_constant(CallNode call, string insecure_version) {
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exists(ControlFlowNode arg | arg = call.getArgByName("ssl_version") |
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arg.(AttrNode).getObject(insecure_version).refersTo(the_ssl_module())
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or
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arg.(NameNode).getId() = insecure_version and
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exists(Import imp |
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imp.getAnImportedModuleName() = "ssl" and
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imp.getAName().getAsname().(Name).getId() = insecure_version
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)
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)
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}
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predicate unsafe_ssl_wrap_socket_call(CallNode call, string method_name, string insecure_version) {
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(
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call = ssl_wrap_socket().getACall() and
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method_name = "deprecated method ssl.wrap_socket"
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or
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call = ssl_Context_class().getACall() and
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method_name = "ssl.SSLContext"
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)
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and
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insecure_version = insecure_version_name()
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and
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(
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call.getArgByName("ssl_version").refersTo(the_ssl_module().getAttribute(insecure_version))
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or
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probable_insecure_ssl_constant(call, insecure_version)
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)
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}
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ClassObject the_pyOpenSSL_Context_class() {
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result = any(ModuleObject m | m.getName() = "pyOpenSSL.SSL").getAttribute("Context")
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}
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predicate unsafe_pyOpenSSL_Context_call(CallNode call, string insecure_version) {
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call = the_pyOpenSSL_Context_class().getACall() and
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insecure_version = insecure_version_name() and
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call.getArg(0).refersTo(the_pyOpenSSL_module().getAttribute(insecure_version))
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}
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from CallNode call, string method_name, string insecure_version
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where
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unsafe_ssl_wrap_socket_call(call, method_name, insecure_version)
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or
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unsafe_pyOpenSSL_Context_call(call, insecure_version) and method_name = "pyOpenSSL.SSL.Context"
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select call, "Insecure SSL/TLS protocol version " + insecure_version + " specified in call to " + method_name + "."

‎python/ql/src/Security/CWE-327/examples/insecure_default_protocol.py‎

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import ssl
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import socket
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# Using the deprecated ssl.wrap_socket method
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ssl.wrap_socket(socket.socket())
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# Using SSLContext
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context = ssl.SSLContext()

‎python/ql/src/Security/CWE-327/examples/insecure_protocol.py‎

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import ssl
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import socket
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# Using the deprecated ssl.wrap_socket method
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ssl.wrap_socket(socket.socket(), ssl_version=ssl.PROTOCOL_SSLv2)
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# Using SSLContext
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context = ssl.SSLContext(ssl_version=ssl.PROTOCOL_SSLv3)
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# Using pyOpenSSL
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from pyOpenSSL import SSL
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context = SSL.Context(SSL.TLSv1_METHOD)
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‎python/ql/test/query-tests/Security/CWE-327/InsecureDefaultProtocol.expected‎

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| InsecureProtocol.py:41:1:41:17 | ControlFlowNode for Attribute() | Call to deprecated method ssl.wrap_socket does not specify a protocol, which may result in an insecure default being used. |
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| InsecureProtocol.py:42:11:42:22 | ControlFlowNode for SSLContext() | Call to ssl.SSLContext does not specify a protocol, which may result in an insecure default being used. |

‎python/ql/test/query-tests/Security/CWE-327/InsecureDefaultProtocol.qlref‎

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Security/CWE-327/InsecureDefaultProtocol.ql

‎python/ql/test/query-tests/Security/CWE-327/InsecureProtocol.expected‎

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| InsecureProtocol.py:6:1:6:47 | ControlFlowNode for Attribute() | Insecure SSL/TLS protocol version PROTOCOL_SSLv2 specified in call to deprecated method ssl.wrap_socket. |
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| InsecureProtocol.py:7:1:7:47 | ControlFlowNode for Attribute() | Insecure SSL/TLS protocol version PROTOCOL_SSLv3 specified in call to deprecated method ssl.wrap_socket. |
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| InsecureProtocol.py:8:1:8:47 | ControlFlowNode for Attribute() | Insecure SSL/TLS protocol version PROTOCOL_TLSv1 specified in call to deprecated method ssl.wrap_socket. |
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| InsecureProtocol.py:10:1:10:42 | ControlFlowNode for SSLContext() | Insecure SSL/TLS protocol version PROTOCOL_SSLv2 specified in call to ssl.SSLContext. |
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| InsecureProtocol.py:11:1:11:42 | ControlFlowNode for SSLContext() | Insecure SSL/TLS protocol version PROTOCOL_SSLv3 specified in call to ssl.SSLContext. |
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| InsecureProtocol.py:12:1:12:42 | ControlFlowNode for SSLContext() | Insecure SSL/TLS protocol version PROTOCOL_TLSv1 specified in call to ssl.SSLContext. |
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| InsecureProtocol.py:14:1:14:29 | ControlFlowNode for Attribute() | Insecure SSL/TLS protocol version SSLv2_METHOD specified in call to pyOpenSSL.SSL.Context. |
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| InsecureProtocol.py:15:1:15:30 | ControlFlowNode for Attribute() | Insecure SSL/TLS protocol version SSLv23_METHOD specified in call to pyOpenSSL.SSL.Context. |
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| InsecureProtocol.py:16:1:16:29 | ControlFlowNode for Attribute() | Insecure SSL/TLS protocol version SSLv3_METHOD specified in call to pyOpenSSL.SSL.Context. |
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| InsecureProtocol.py:17:1:17:29 | ControlFlowNode for Attribute() | Insecure SSL/TLS protocol version TLSv1_METHOD specified in call to pyOpenSSL.SSL.Context. |
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| InsecureProtocol.py:32:1:32:19 | ControlFlowNode for Attribute() | Insecure SSL/TLS protocol version SSLv2_METHOD specified in call to pyOpenSSL.SSL.Context. |
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| InsecureProtocol.py:48:1:48:43 | ControlFlowNode for Attribute() | Insecure SSL/TLS protocol version PROTOCOL_SSLv2 specified in call to deprecated method ssl.wrap_socket. |
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| InsecureProtocol.py:49:1:49:38 | ControlFlowNode for SSLContext() | Insecure SSL/TLS protocol version PROTOCOL_SSLv2 specified in call to ssl.SSLContext. |

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