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Merge pull request #2092 from esben-semmle/js/brittle-system-reflection-command
Approved by mchammer01, xiemaisi
2 parents eb9d90d + 5a983cb commit 1c79ec5

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‎change-notes/1.23/analysis-javascript.md‎

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| Unused index variable (`js/unused-index-variable`) | correctness | Highlights loops that iterate over an array, but do not use the index variable to access array elements, indicating a possible typo or logic error. Results are shown on LGTM by default. |
2020
| Loop bound injection (`js/loop-bound-injection`) | security, external/cwe/cwe-834 | Highlights loops where a user-controlled object with an arbitrary .length value can trick the server to loop indefinitely. Results are not shown on LGTM by default. |
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| Suspicious method name (`js/suspicious-method-name-declaration`) | correctness, typescript, methods | Highlights suspiciously named methods where the developer likely meant to write a constructor or function. Results are shown on LGTM by default. |
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| Shell command built from environment values (`js/shell-command-injection-from-environment`) | correctness, security, external/cwe/cwe-078, external/cwe/cwe-088 | Highlights shell commands that may change behavior inadvertently depending on the execution environment, indicating a possible violation of [CWE-78](https://cwe.mitre.org/data/definitions/78.html). Results are shown on LGTM by default.|
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| Use of returnless function (`js/use-of-returnless-function`) | maintainability, correctness | Highlights calls where the return value is used, but the callee never returns a value. Results are shown on LGTM by default. |
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| Useless regular expression character escape (`js/useless-regexp-character-escape`) | correctness, security, external/cwe/cwe-20 | Highlights regular expression strings with useless character escapes, indicating a possible violation of [CWE-20](https://cwe.mitre.org/data/definitions/20.html). Results are shown on LGTM by default. |
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| Unreachable method overloads (`js/unreachable-method-overloads`) | correctness, typescript | Highlights method overloads that are impossible to use from client code. Results are shown on LGTM by default. |

‎javascript/config/suites/javascript/security‎

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+ semmlecode-javascript-queries/Security/CWE-022/ZipSlip.ql: /Security/CWE/CWE-022
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+ semmlecode-javascript-queries/Security/CWE-078/CommandInjection.ql: /Security/CWE/CWE-078
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+ semmlecode-javascript-queries/Security/CWE-078/IndirectCommandInjection.ql: /Security/CWE/CWE-078
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+ semmlecode-javascript-queries/Security/CWE-078/ShellCommandInjectionFromEnvironment: /Security/CWE/CWE-078
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+ semmlecode-javascript-queries/Security/CWE-079/ReflectedXss.ql: /Security/CWE/CWE-079
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+ semmlecode-javascript-queries/Security/CWE-079/StoredXss.ql: /Security/CWE/CWE-079
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+ semmlecode-javascript-queries/Security/CWE-079/Xss.ql: /Security/CWE/CWE-079

‎javascript/ql/src/Security/CWE-078/ShellCommandInjectionFromEnvironment.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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Dynamically constructing a shell command with values from the
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local environment, such as file paths, may inadvertently
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change the meaning of the shell command.
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Such changes can occur when an environment value contains
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characters that the shell interprets in a special way, for instance
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quotes and spaces.
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This can result in the shell command misbehaving, or even
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allowing a malicious user to execute arbitrary commands on the system.
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</p>
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</overview>
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<recommendation>
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<p>
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If possible, use hard-coded string literals to specify the
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shell command to run, and provide the dynamic arguments to the shell
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command separately to avoid interpretation by the shell.
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</p>
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<p>
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Alternatively, if the shell command must be constructed
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dynamically, then add code to ensure that special characters in
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environment values do not alter the shell command unexpectedly.
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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 example shows a dynamically constructed shell
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command that recursively removes a temporary directory that is located
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next to the currently executing JavaScript file. Such utilities are
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often found in custom build scripts.
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</p>
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<sample src="examples/shell-command-injection-from-environment.js" />
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<p>
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The shell command will, however, fail to work as intended if the
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absolute path of the script's directory contains spaces. In that
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case, the shell command will interpret the absolute path as multiple
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paths, instead of a single path.
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</p>
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<p>
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For instance, if the absolute path of
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the temporary directory is <code>/home/username/important
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project/temp</code>, then the shell command will recursively delete
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<code>/home/username/important</code> and <code>project/temp</code>,
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where the latter path gets resolved relative to the working directory
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of the JavaScript process.
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</p>
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<p>
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Even worse, although less likely, a malicious user could
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provide the path <code>/home/username/; cat /etc/passwd #/important
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project/temp</code> in order to execute the command <code>cat
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/etc/passwd</code>.
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</p>
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<p>
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To avoid such potentially catastrophic behaviors, provide the
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directory as an argument that does not get interpreted by a
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shell:
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</p>
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<sample src="examples/shell-command-injection-from-environment_fixed.js" />
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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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</references>
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</qhelp>

‎javascript/ql/src/Security/CWE-078/ShellCommandInjectionFromEnvironment.ql‎

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/**
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* @name Shell command built from environment values
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* @description Building a shell command string with values from the enclosing
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* environment may cause subtle bugs or vulnerabilities.
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* @kind path-problem
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* @problem.severity warning
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* @precision high
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* @id js/shell-command-injection-from-environment
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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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*/
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import javascript
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import DataFlow::PathGraph
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import semmle.javascript.security.dataflow.ShellCommandInjectionFromEnvironment::ShellCommandInjectionFromEnvironment
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from
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Configuration cfg, DataFlow::PathNode source, DataFlow::PathNode sink, DataFlow::Node highlight,
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Source sourceNode
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where
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sourceNode = source.getNode() and
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cfg.hasFlowPath(source, sink) and
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if cfg.isSinkWithHighlight(sink.getNode(), _)
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then cfg.isSinkWithHighlight(sink.getNode(), highlight)
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else highlight = sink.getNode()
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select highlight, source, sink, "This shell command depends on an uncontrolled $@.", sourceNode,
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sourceNode.getSourceType()

‎javascript/ql/src/Security/CWE-078/examples/shell-command-injection-from-environment.js‎

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var cp = require("child_process"),
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path = require("path");
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function cleanupTemp() {
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let cmd = "rm -rf " + path.join(__dirname, "temp");
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cp.execSync(cmd); // BAD
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}

‎javascript/ql/src/Security/CWE-078/examples/shell-command-injection-from-environment_fixed.js‎

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var cp = require("child_process"),
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path = require("path");
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function cleanupTemp() {
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let cmd = "rm",
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args = ["-rf", path.join(__dirname, "temp")];
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cp.execFileSync(cmd, args); // GOOD
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}

‎javascript/ql/src/semmle/javascript/Concepts.qll‎

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/** Gets an argument to this execution that specifies the command. */
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abstract DataFlow::Node getACommandArgument();
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/** Holds if a shell interprets `arg`. */
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predicate isShellInterpreted(DataFlow::Node arg) { none() }
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/**
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* Gets an argument to this command execution that specifies the argument list
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* to the command.

‎javascript/ql/src/semmle/javascript/frameworks/NodeJSLib.qll‎

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this = DataFlow::moduleMember("child_process", methodName).getACall()
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}
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override DataFlow::Node getACommandArgument() {
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private DataFlow::Node getACommandArgument(boolean shell) {
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// check whether this is an invocation of an exec/spawn/fork method
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(
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methodName = "exec" or
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methodName = "execSync" or
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methodName = "execFile" or
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methodName = "execFileSync" or
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methodName = "spawn" or
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methodName = "spawnSync" or
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methodName = "fork"
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shell = true and
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(
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methodName = "exec" or
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methodName = "execSync"
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)
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or
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shell = false and
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(
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methodName = "execFile" or
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methodName = "execFileSync" or
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methodName = "spawn" or
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methodName = "spawnSync" or
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methodName = "fork"
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)
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) and
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// all of the above methods take the command as their first argument
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result = getArgument(0)
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}
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override DataFlow::Node getACommandArgument() { result = getACommandArgument(_) }
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override predicate isShellInterpreted(DataFlow::Node arg) { arg = getACommandArgument(true) }
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override DataFlow::Node getArgumentList() {
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(
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methodName = "execFile" or

‎javascript/ql/src/semmle/javascript/frameworks/ShellJS.qll‎

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ShellJSExec() { name = "exec" }
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override DataFlow::Node getACommandArgument() { result = getArgument(0) }
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override predicate isShellInterpreted(DataFlow::Node arg) { arg = getACommandArgument() }
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}
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/**

‎javascript/ql/src/semmle/javascript/frameworks/SystemCommandExecutors.qll‎

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private class SystemCommandExecutors extends SystemCommandExecution, DataFlow::InvokeNode {
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int cmdArg;
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boolean shell;
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SystemCommandExecutors() {
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exists(string mod, DataFlow::SourceNode callee |
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exists(string method |
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mod = "cross-spawn" and method = "sync" and cmdArg = 0
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mod = "cross-spawn" and method = "sync" and cmdArg = 0 and shell = false
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or
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mod = "execa" and
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(
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method = "shell" or
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method = "shellSync" or
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method = "stdout" or
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method = "stderr" or
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method = "sync"
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shell = false and
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(
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method = "shell" or
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method = "shellSync" or
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method = "stdout" or
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method = "stderr" or
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method = "sync"
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)
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or
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shell = true and
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(method = "command" or method = "commandSync")
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) and
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cmdArg = 0
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|
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callee = DataFlow::moduleMember(mod, method)
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)
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or
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(
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mod = "cross-spawn" and cmdArg = 0
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or
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mod = "cross-spawn-async" and cmdArg = 0
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or
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mod = "exec" and cmdArg = 0
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or
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mod = "exec-async" and cmdArg = 0
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or
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mod = "execa" and cmdArg = 0
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shell = false and
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(
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mod = "cross-spawn" and cmdArg = 0
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or
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mod = "cross-spawn-async" and cmdArg = 0
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or
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mod = "exec-async" and cmdArg = 0
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or
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mod = "execa" and cmdArg = 0
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)
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or
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mod = "remote-exec" and cmdArg = 1
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shell = true and
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(
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mod = "exec" and
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cmdArg = 0
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or
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mod = "remote-exec" and cmdArg = 1
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)
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) and
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callee = DataFlow::moduleImport(mod)
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|
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}
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override DataFlow::Node getACommandArgument() { result = getArgument(cmdArg) }
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override predicate isShellInterpreted(DataFlow::Node arg) {
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arg = getACommandArgument() and shell = true
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}
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}

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