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Merge remote-tracking branch 'upstream/main' into python-dataflow-variable-capture
2 parents 7cbbf3b + 2cf10a7 commit 38bb06a

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‎config/identical-files.json‎

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"cpp/ql/test/TestUtilities/InlineExpectationsTest.qll",
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"python/ql/test/TestUtilities/InlineExpectationsTest.qll"
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],
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"C++ ExternalAPIs": [
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"cpp/ql/src/Security/CWE/CWE-020/ExternalAPIs.qll",
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"cpp/ql/src/Security/CWE/CWE-020/ir/ExternalAPIs.qll"
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],
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"C++ SafeExternalAPIFunction": [
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"cpp/ql/src/Security/CWE/CWE-020/SafeExternalAPIFunction.qll",
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"cpp/ql/src/Security/CWE/CWE-020/ir/SafeExternalAPIFunction.qll"
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],
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"XML": [
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"cpp/ql/src/semmle/code/cpp/XML.qll",
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"csharp/ql/src/semmle/code/csharp/XML.qll",

‎cpp/ql/src/Security/CWE/CWE-020/CountUntrustedDataToExternalAPI.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>Using unsanitized untrusted data in an external API can cause a variety of security issues. This query reports
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all external APIs that are used with untrusted data, along with how frequently the API is used, and how many
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unique sources of untrusted data flow to this API. This query is designed primarily to help identify which APIs
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may be relevant for security analysis of this application.</p>
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<p>An external API is defined as a call to a function that is not defined in the source code, and is not
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modeled as a taint step in the default taint library. External APIs may be from the C++ standard library,
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third party dependencies or from internal dependencies. The query will report the function name, along with
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either <code>[param x]</code>, where <code>x</code> indicates the position of the parameter receiving the
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untrusted data or <code>[qualifier]</code> indicating the untrusted data is used as the qualifier to the
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function call.</p>
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</overview>
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<recommendation>
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<p>For each result:</p>
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<ul>
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<li>If the result highlights a known sink, no action is required.</li>
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<li>If the result highlights an unknown sink for a problem, then add modeling for the sink to the relevant query.</li>
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<li>If the result represents a call to an external API which transfers taint, add the appropriate modeling, and
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re-run the query to determine what new results have appeared due to this additional modeling.</li>
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</ul>
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<p>Otherwise, the result is likely uninteresting. Custom versions of this query can extend the <code>SafeExternalAPIFunction</code>
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class to exclude known safe external APIs from future analysis.</p>
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</recommendation>
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<example>
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<p>If the query were to return the API <code>fputs [param 1]</code>
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then we should first consider whether this a security relevant sink. In this case, this is writing to a <code>FILE*</code>, so we should
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consider whether this is an XSS sink. If it is, we should confirm that it is handled by the XSS query.</p>
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<p>If the query were to return the API <code>strcat [param 1]</code>, then this should be
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reviewed as a possible taint step, because tainted data would flow from the 1st argument to the 0th argument of the call.</p>
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<p>Note that both examples are correctly handled by the standard taint tracking library and XSS query.</p>
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</example>
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<references>
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</references>
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</qhelp>

‎cpp/ql/src/Security/CWE/CWE-020/CountUntrustedDataToExternalAPI.ql‎

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/**
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* @name Frequency counts for external APIs that are used with untrusted data
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* @description This reports the external APIs that are used with untrusted data, along with how
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* frequently the API is called, and how many unique sources of untrusted data flow
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* to it.
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* @id cpp/count-untrusted-data-external-api
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* @kind table
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* @tags security external/cwe/cwe-20
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*/
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import cpp
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import ExternalAPIs
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from ExternalAPIUsedWithUntrustedData externalAPI
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select externalAPI, count(externalAPI.getUntrustedDataNode()) as numberOfUses,
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externalAPI.getNumberOfUntrustedSources() as numberOfUntrustedSources order by
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numberOfUntrustedSources desc

‎cpp/ql/src/Security/CWE/CWE-020/ExternalAPISinkExample.cpp‎

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#include <cstdio>
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void do_get(FILE* request, FILE* response) {
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char page[1024];
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fgets(page, 1024, request);
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char buffer[1024];
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strcat(buffer, "The page \"");
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strcat(buffer, page);
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strcat(buffer, "\" was not found.");
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fputs(buffer, response);
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}

‎cpp/ql/src/Security/CWE/CWE-020/ExternalAPITaintStepExample.cpp‎

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#include <cstdio>
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void do_get(FILE* request, FILE* response) {
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char user_id[1024];
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fgets(user_id, 1024, request);
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char buffer[1024];
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strcat(buffer, "SELECT * FROM user WHERE user_id='");
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strcat(buffer, user_id);
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strcat(buffer, "'");
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// ...
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}

‎cpp/ql/src/Security/CWE/CWE-020/ExternalAPIs.qll‎

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/**
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* Definitions for reasoning about untrusted data used in APIs defined outside the
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* database.
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*/
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private import cpp
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private import semmle.code.cpp.models.interfaces.DataFlow
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private import semmle.code.cpp.models.interfaces.Taint
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import ExternalAPIsSpecific
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/** A node representing untrusted data being passed to an external API. */
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class UntrustedExternalAPIDataNode extends ExternalAPIDataNode {
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UntrustedExternalAPIDataNode() { any(UntrustedDataToExternalAPIConfig c).hasFlow(_, this) }
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/** Gets a source of untrusted data which is passed to this external API data node. */
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DataFlow::Node getAnUntrustedSource() {
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any(UntrustedDataToExternalAPIConfig c).hasFlow(result, this)
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}
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}
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private newtype TExternalAPI =
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TExternalAPIParameter(Function f, int index) {
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exists(UntrustedExternalAPIDataNode n |
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f = n.getExternalFunction() and
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index = n.getIndex()
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)
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}
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/** An external API which is used with untrusted data. */
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class ExternalAPIUsedWithUntrustedData extends TExternalAPI {
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/** Gets a possibly untrusted use of this external API. */
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UntrustedExternalAPIDataNode getUntrustedDataNode() {
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this = TExternalAPIParameter(result.getExternalFunction(), result.getIndex())
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}
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/** Gets the number of untrusted sources used with this external API. */
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int getNumberOfUntrustedSources() {
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result = strictcount(getUntrustedDataNode().getAnUntrustedSource())
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}
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/** Gets a textual representation of this element. */
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string toString() {
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exists(Function f, int index, string indexString |
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if index = -1 then indexString = "qualifier" else indexString = "param " + index
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|
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this = TExternalAPIParameter(f, index) and
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result = f.toString() + " [" + indexString + "]"
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)
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}
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}

‎cpp/ql/src/Security/CWE/CWE-020/ExternalAPIsSpecific.qll‎

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/**
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* Provides AST-specific definitions for use in the `ExternalAPI` library.
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*/
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import semmle.code.cpp.dataflow.TaintTracking
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import semmle.code.cpp.models.interfaces.FlowSource
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import semmle.code.cpp.models.interfaces.DataFlow
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import SafeExternalAPIFunction
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/** A node representing untrusted data being passed to an external API. */
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class ExternalAPIDataNode extends DataFlow::Node {
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Call call;
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int i;
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ExternalAPIDataNode() {
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// Argument to call to a function
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(
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this.asExpr() = call.getArgument(i)
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or
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i = -1 and this.asExpr() = call.getQualifier()
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) and
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exists(Function f |
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f = call.getTarget() and
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// Defined outside the source archive
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not f.hasDefinition() and
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// Not already modeled as a dataflow or taint step
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not f instanceof DataFlowFunction and
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not f instanceof TaintFunction and
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// Not a call to a known safe external API
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not f instanceof SafeExternalAPIFunction
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)
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}
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/** Gets the called API `Function`. */
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Function getExternalFunction() { result = call.getTarget() }
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/** Gets the index which is passed untrusted data (where -1 indicates the qualifier). */
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int getIndex() { result = i }
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/** Gets the description of the function being called. */
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string getFunctionDescription() { result = getExternalFunction().toString() }
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}
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/** A configuration for tracking flow from `RemoteFlowSource`s to `ExternalAPIDataNode`s. */
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class UntrustedDataToExternalAPIConfig extends TaintTracking::Configuration {
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UntrustedDataToExternalAPIConfig() { this = "UntrustedDataToExternalAPIConfig" }
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override predicate isSource(DataFlow::Node source) {
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exists(RemoteFlowFunction remoteFlow |
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remoteFlow = source.asExpr().(Call).getTarget() and
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remoteFlow.hasRemoteFlowSource(_, _)
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)
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}
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override predicate isSink(DataFlow::Node sink) { sink instanceof ExternalAPIDataNode }
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}

‎cpp/ql/src/Security/CWE/CWE-020/IRCountUntrustedDataToExternalAPI.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>Using unsanitized untrusted data in an external API can cause a variety of security issues. This query reports
7+
all external APIs that are used with untrusted data, along with how frequently the API is used, and how many
8+
unique sources of untrusted data flow to this API. This query is designed primarily to help identify which APIs
9+
may be relevant for security analysis of this application.</p>
10+
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<p>An external API is defined as a call to a function that is not defined in the source code, and is not
12+
modeled as a taint step in the default taint library. External APIs may be from the C++ standard library,
13+
third party dependencies or from internal dependencies. The query will report the function name, along with
14+
either <code>[param x]</code>, where <code>x</code> indicates the position of the parameter receiving the
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untrusted data or <code>[qualifier]</code> indicating the untrusted data is used as the qualifier to the
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function call.</p>
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</overview>
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<recommendation>
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<p>For each result:</p>
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23+
<ul>
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<li>If the result highlights a known sink, no action is required.</li>
25+
<li>If the result highlights an unknown sink for a problem, then add modeling for the sink to the relevant query.</li>
26+
<li>If the result represents a call to an external API which transfers taint, add the appropriate modeling, and
27+
re-run the query to determine what new results have appeared due to this additional modeling.</li>
28+
</ul>
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<p>Otherwise, the result is likely uninteresting. Custom versions of this query can extend the <code>SafeExternalAPIFunction</code>
31+
class to exclude known safe external APIs from future analysis.</p>
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</recommendation>
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<example>
35+
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<p>If the query were to return the API <code>fputs [param 1]</code>
37+
then we should first consider whether this a security relevant sink. In this case, this is writing to a <code>FILE*</code>, so we should
38+
consider whether this is an XSS sink. If it is, we should confirm that it is handled by the XSS query.</p>
39+
40+
<p>If the query were to return the API <code>strcat [param 1]</code>, then this should be
41+
reviewed as a possible taint step, because tainted data would flow from the 1st argument to the 0th argument of the call.</p>
42+
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<p>Note that both examples are correctly handled by the standard taint tracking library and XSS query.</p>
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</example>
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<references>
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</references>
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</qhelp>

‎cpp/ql/src/Security/CWE/CWE-020/IRCountUntrustedDataToExternalAPI.ql‎

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/**
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* @name Frequency counts for external APIs that are used with untrusted data
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* @description This reports the external APIs that are used with untrusted data, along with how
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* frequently the API is called, and how many unique sources of untrusted data flow
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* to it.
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* @id cpp/count-untrusted-data-external-api-ir
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* @kind table
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* @tags security external/cwe/cwe-20
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*/
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import cpp
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import ir.ExternalAPIs
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from ExternalAPIUsedWithUntrustedData externalAPI
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select externalAPI, count(externalAPI.getUntrustedDataNode()) as numberOfUses,
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externalAPI.getNumberOfUntrustedSources() as numberOfUntrustedSources order by
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numberOfUntrustedSources desc

‎cpp/ql/src/Security/CWE/CWE-020/IRUntrustedDataToExternalAPI.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>Using unsanitized untrusted data in an external API can cause a variety of security issues. This query reports
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external APIs that use untrusted data. The results are not filtered, so you can audit all examples.
8+
The query provides data for security reviews of the application and you can also use it to identify external APIs
9+
that should be modeled as either taint steps, or sinks for specific problems.</p>
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<p>An external API is defined as a call to a function that is not defined in the source code, and is not modeled
12+
as a taint step in the default taint library. External APIs may be from the
13+
C++ standard library, third-party dependencies or from internal dependencies. The query reports uses of
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untrusted data in either the qualifier or as one of the arguments of external APIs.</p>
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</overview>
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<recommendation>
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<p>For each result:</p>
20+
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<ul>
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<li>If the result highlights a known sink, confirm that the result is reported by the relevant query, or
23+
that the result is a false positive because this data is sanitized.</li>
24+
<li>If the result highlights an unknown sink for a problem, then add modeling for the sink to the relevant query,
25+
and confirm that the result is either found, or is safe due to appropriate sanitization.</li>
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<li>If the result represents a call to an external API that transfers taint, add the appropriate modeling, and
27+
re-run the query to determine what new results have appeared due to this additional modeling.</li>
28+
</ul>
29+
30+
<p>Otherwise, the result is likely uninteresting. Custom versions of this query can extend the <code>SafeExternalAPIFunction</code>
31+
class to exclude known safe external APIs from future analysis.</p>
32+
33+
</recommendation>
34+
<example>
35+
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<p>In this first example, input is read from <code>fgets</code> and then ultimately used in a call to the
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<code>fputs</code> external API:</p>
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<sample src="ExternalAPISinkExample.cpp" />
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<p>This is an XSS sink. The XSS query should therefore be reviewed to confirm that this sink is appropriately modeled,
42+
and if it is, to confirm that the query reports this particular result, or that the result is a false positive due to
43+
some existing sanitization.</p>
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<p>In this second example, again a request parameter is read from <code>fgets</code>.</p>
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<sample src="ExternalAPITaintStepExample.cpp" />
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<p>If the query reported the call to <code>strcat</code> on line 9, this would suggest that this external API is
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not currently modeled as a taint step in the taint tracking library. The next step would be to model this as a taint step, then
51+
re-run the query to determine what additional results might be found. In this example, it seems likely that <code>buffer</code>
52+
will be executed as an SQL query, potentially leading to an SQL injection vulnerability.</p>
53+
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<p>Note that both examples are correctly handled by the standard taint tracking library and XSS query.</p>
55+
</example>
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<references>
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</references>
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</qhelp>

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