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Merge pull request github#10708 from erik-krogh/kernelSink
RB: add a query flagging uses of `Kernel.open()` that are not with a constant string
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‎ruby/ql/lib/codeql/ruby/security/KernelOpenQuery.qll

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/**
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* Provides utility classes and predicates for reasoning about `Kernel.open` and related methods.
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*/
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private import codeql.ruby.AST
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private import codeql.ruby.DataFlow
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private import codeql.ruby.AST
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private import codeql.ruby.ApiGraphs
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private import codeql.ruby.frameworks.core.Kernel::Kernel
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/** A call to a method that might access a file or start a process. */
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class AmbiguousPathCall extends DataFlow::CallNode {
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string name;
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AmbiguousPathCall() {
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this.(KernelMethodCall).getMethodName() = "open" and
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name = "Kernel.open"
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or
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this = API::getTopLevelMember("IO").getAMethodCall("read") and
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not this = API::getTopLevelMember("File").getAMethodCall("read") and // needed in e.g. opal/opal, where some calls have both paths, but I'm not sure why
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name = "IO.read"
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}
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/** Gets the name for the method being called. */
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string getName() { result = name }
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/** Gets the name for a safer method that can be used instead. */
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string getReplacement() {
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result = "File.read" and name = "IO.read"
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or
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result = "File.open" and name = "Kernel.open"
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}
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/** Gets the argument that specifies the path to be accessed. */
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DataFlow::Node getPathArgument() { result = this.getArgument(0) }
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}

‎ruby/ql/src/change-notes/2022-10-06-non-constant-kernel-open.md

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---
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category: newQuery
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---
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* Added a new query, `rb/non-constant-kernel-open`, to detect uses of Kernel.open and related methods with non-constant values.

‎ruby/ql/src/queries/security/cwe-078/KernelOpen.inc.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>If <code>Kernel.open</code> is given a file name that starts with a <code>|</code>
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character, it will execute the remaining string as a shell command. If a
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malicious user can control the file name, they can execute arbitrary code.
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The same vulnerability applies to <code>IO.read</code>.
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</p>
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</overview>
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<recommendation>
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<p>Use <code>File.open</code> instead of <code>Kernel.open</code>, as the former
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does not have this vulnerability. Similarly, use <code>File.read</code> instead
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of <code>IO.read</code>.</p>
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</recommendation>
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<example>
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<p>
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The following example shows code that calls <code>Kernel.open</code> on a
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user-supplied file path.
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</p>
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<sample src="examples/kernel_open.rb" />
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<p>Instead, <code>File.open</code> should be used, as in the following example.</p>
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<sample src="examples/file_open.rb" />
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</example>
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<references>
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<li>
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OWASP:
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<a href="https://www.owasp.org/index.php/Command_Injection">Command Injection</a>.
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</li>
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<li>
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Example CVE: <a href="https://www.ruby-lang.org/en/news/2021/05/02/os-command-injection-in-rdoc/">Command Injection in RDoc</a>.
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</li>
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</references>
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</qhelp>

‎ruby/ql/src/queries/security/cwe-078/KernelOpen.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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<!DOCTYPE qhelp PUBLIC "-//Semmle//qhelp//EN" "qhelp.dtd">
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<qhelp>
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<overview>
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<p>If <code>Kernel.open</code> is given a file name that starts with a <code>|</code>
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character, it will execute the remaining string as a shell command. If a
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malicious user can control the file name, they can execute arbitrary code.
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The same vulnerability applies to <code>IO.read</code>.
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</p>
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</overview>
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<recommendation>
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<p>Use <code>File.open</code> instead of <code>Kernel.open</code>, as the former
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does not have this vulnerability. Similarly, use <code>File.read</code> instead
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of <code>IO.read</code>.</p>
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</recommendation>
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<example>
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<p>
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The following example shows code that calls <code>Kernel.open</code> on a
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user-supplied file path.
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</p>
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<sample src="examples/kernel_open.rb" />
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<p>Instead, <code>File.open</code> should be used, as in the following example.</p>
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<sample src="examples/file_open.rb" />
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</example>
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<references>
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<li>
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OWASP:
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<a href="https://www.owasp.org/index.php/Command_Injection">Command Injection</a>.
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</li>
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<li>
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Example CVE: <a href="https://www.ruby-lang.org/en/news/2021/05/02/os-command-injection-in-rdoc/">Command Injection in RDoc</a>.
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</li>
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</references>
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</qhelp>
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<include src="KernelOpen.inc.qhelp" />
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</qhelp>

‎ruby/ql/src/queries/security/cwe-078/KernelOpen.ql

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/**
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* @name Use of `Kernel.open` or `IO.read`
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* @name Use of `Kernel.open` or `IO.read` with user-controlled input
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* @description Using `Kernel.open` or `IO.read` may allow a malicious
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* user to execute arbitrary system commands.
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* @kind path-problem
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* external/cwe/cwe-073
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*/
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import codeql.ruby.AST
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import codeql.ruby.ApiGraphs
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import codeql.ruby.frameworks.core.Kernel::Kernel
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import codeql.ruby.DataFlow
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import codeql.ruby.TaintTracking
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import codeql.ruby.dataflow.BarrierGuards
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import codeql.ruby.dataflow.RemoteFlowSources
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import codeql.ruby.DataFlow
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import codeql.ruby.dataflow.BarrierGuards
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import DataFlow::PathGraph
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/**
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* A method call that has a suggested replacement.
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*/
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abstract class Replacement extends DataFlow::CallNode {
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abstract string getFrom();
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abstract string getTo();
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}
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class KernelOpenCall extends KernelMethodCall, Replacement {
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KernelOpenCall() { this.getMethodName() = "open" }
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override string getFrom() { result = "Kernel.open" }
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override string getTo() { result = "File.open" }
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}
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class IOReadCall extends DataFlow::CallNode, Replacement {
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IOReadCall() { this = API::getTopLevelMember("IO").getAMethodCall("read") }
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override string getFrom() { result = "IO.read" }
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override string getTo() { result = "File.read" }
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}
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import codeql.ruby.security.KernelOpenQuery
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class Configuration extends TaintTracking::Configuration {
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Configuration() { this = "KernelOpen" }
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override predicate isSource(DataFlow::Node source) { source instanceof RemoteFlowSource }
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override predicate isSink(DataFlow::Node sink) {
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exists(KernelOpenCall c | c.getArgument(0) = sink)
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or
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exists(IOReadCall c | c.getArgument(0) = sink)
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sink = any(AmbiguousPathCall r).getPathArgument()
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}
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override predicate isSanitizer(DataFlow::Node node) {
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sourceNode = source.getNode() and
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call.getArgument(0) = sink.getNode()
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select sink.getNode(), source, sink,
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"This call to " + call.(Replacement).getFrom() + " depends on a $@. Replace it with " +
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call.(Replacement).getTo() + ".", source.getNode(), "user-provided value"
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"This call to " + call.(AmbiguousPathCall).getName() +
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" depends on a $@. Consider replacing it with " + call.(AmbiguousPathCall).getReplacement() +
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".", source.getNode(), "user-provided value"

‎ruby/ql/src/queries/security/cwe-078/NonConstantKernelOpen.qhelp

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<!DOCTYPE qhelp PUBLIC "-//Semmle//qhelp//EN" "qhelp.dtd">
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<qhelp>
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<include src="KernelOpen.inc.qhelp" />
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</qhelp>

‎ruby/ql/src/queries/security/cwe-078/NonConstantKernelOpen.ql

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/**
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* @name Use of `Kernel.open` or `IO.read` with a non-constant value
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* @description Using `Kernel.open` or `IO.read` may allow a malicious
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* user to execute arbitrary system commands.
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* @kind problem
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* @problem.severity warning
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* @security-severity 6.5
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* @precision high
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* @id rb/non-constant-kernel-open
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* @tags correctness
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* security
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* external/cwe/cwe-078
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* external/cwe/cwe-088
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* external/cwe/cwe-073
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*/
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import codeql.ruby.security.KernelOpenQuery
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import codeql.ruby.ast.Literal
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from AmbiguousPathCall call
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where
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// there is not a constant string argument
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not exists(call.getPathArgument().asExpr().getExpr().getConstantValue()) and
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// if it's a format string, then the first argument is not a constant string
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not call.getPathArgument().getALocalSource().asExpr().getExpr().(StringLiteral).getComponent(0)
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instanceof StringTextComponent
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select call,
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"Call to " + call.getName() + " with a non-constant value. Consider replacing it with " +
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call.getReplacement() + "."

‎ruby/ql/test/query-tests/security/cwe-078/CommandInjection.expected renamed to ‎ruby/ql/test/query-tests/security/cwe-078/CommandInjection/CommandInjection.expected

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‎ruby/ql/test/query-tests/security/cwe-078/CommandInjection.qlref renamed to ‎ruby/ql/test/query-tests/security/cwe-078/CommandInjection/CommandInjection.qlref

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‎ruby/ql/test/query-tests/security/cwe-078/CommandInjection.rb renamed to ‎ruby/ql/test/query-tests/security/cwe-078/CommandInjection/CommandInjection.rb

File renamed without changes.

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