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Merge pull request #623 from esben-semmle/js/incomplete-url-sanitization
Approved by mc-semmle
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‎change-notes/1.20/analysis-javascript.md‎

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| **Query** | **Tags** | **Purpose** |
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|-----------------------------------------------|------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| Double escaping or unescaping (`js/double-escaping`) | correctness, security, external/cwe/cwe-116 | Highlights potential double escaping or unescaping of special characters, indicating a possible violation of [CWE-116](https://cwe.mitre.org/data/definitions/116.html). Results are shown on LGTM by default. |
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| Incomplete URL substring sanitization | correctness, security, external/cwe/cwe-020 | Highlights URL sanitizers that are likely to be incomplete, indicating a violation of [CWE-020](https://cwe.mitre.org/data/definitions/20.html). Results shown on LGTM by default. |
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| Incorrect suffix check (`js/incorrect-suffix-check`) | correctness, security, external/cwe/cwe-020 | Highlights error-prone suffix checks based on `indexOf`, indicating a potential violation of [CWE-20](https://cwe.mitre.org/data/definitions/20.html). Results are shown on LGTM by default. |
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| Useless comparison test (`js/useless-comparison-test`) | correctness | Highlights code that is unreachable due to a numeric comparison that is always true or always false. Results are shown on LGTM by default. |
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‎javascript/config/suites/javascript/security‎

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+ semmlecode-javascript-queries/DOM/TargetBlank.ql: /Security/CWE/CWE-200
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+ semmlecode-javascript-queries/Electron/EnablingNodeIntegration.ql: /Security/CWE/CWE-094
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+ semmlecode-javascript-queries/Security/CWE-020/IncompleteUrlSubstringSanitization.ql: /Security/CWE/CWE-020
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+ semmlecode-javascript-queries/Security/CWE-020/IncorrectSuffixCheck.ql: /Security/CWE/CWE-020
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+ semmlecode-javascript-queries/Security/CWE-022/TaintedPath.ql: /Security/CWE/CWE-022
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+ semmlecode-javascript-queries/Security/CWE-078/CommandInjection.ql: /Security/CWE/CWE-078

‎javascript/ql/src/Security/CWE-020/IncompleteUrlSubstringSanitization.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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Sanitizing untrusted URLs is an important technique for
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preventing attacks such as request forgeries and malicious
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redirections. Usually, this is done by checking that the host of a URL
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is in a set of allowed hosts.
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</p>
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<p>
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However, it is notoriously error-prone to treat the URL as
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a string and check if one of the allowed hosts is a substring of the
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URL. Malicious URLs can bypass such security checks by embedding one
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of the allowed hosts in an unexpected location.
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</p>
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<p>
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Even if the substring check is not used in a
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security-critical context, the incomplete check may still cause
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undesirable behaviors when the check succeeds accidentally.
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</p>
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</overview>
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<recommendation>
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<p>
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Parse a URL before performing a check on its host value,
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and ensure that the check handles arbitrary subdomain sequences
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correctly.
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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 code checks that a URL redirection
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will reach the <code>example.com</code> domain, or one of its
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subdomains, and not some malicious site.
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</p>
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<sample src="examples/IncompleteUrlSubstringSanitization_BAD1.js"/>
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<p>
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The substring check is, however, easy to bypass. For example
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by embedding <code>example.com</code> in the path component:
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<code>http://evil-example.net/example.com</code>, or in the query
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string component: <code>http://evil-example.net/?x=example.com</code>.
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Address these shortcomings by checking the host of the parsed URL instead:
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</p>
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<sample src="examples/IncompleteUrlSubstringSanitization_BAD2.js"/>
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<p>
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This is still not a sufficient check as the
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following URLs bypass it: <code>http://evil-example.com</code>
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<code>http://example.com.evil-example.net</code>.
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Instead, use an explicit whitelist of allowed hosts to
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make the redirect secure:
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</p>
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<sample src="examples/IncompleteUrlSubstringSanitization_GOOD.js"/>
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</example>
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<references>
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<li>OWASP: <a href="https://www.owasp.org/index.php/Server_Side_Request_Forgery">SSRF</a></li>
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<li>OWASP: <a href="https://www.owasp.org/index.php/Unvalidated_Redirects_and_Forwards_Cheat_Sheet">XSS Unvalidated Redirects and Forwards Cheat Sheet</a>.</li>
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</references>
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</qhelp>

‎javascript/ql/src/Security/CWE-020/IncompleteUrlSubstringSanitization.ql‎

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/**
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* @name Incomplete URL substring sanitization
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* @description Security checks on the substrings of an unparsed URL are often vulnerable to bypassing.
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* @kind problem
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* @problem.severity warning
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* @precision high
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* @id js/incomplete-url-substring-sanitization
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* @tags correctness
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* security
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* external/cwe/cwe-20
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*/
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import javascript
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private import semmle.javascript.dataflow.InferredTypes
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from DataFlow::MethodCallNode call, string name, DataFlow::Node substring, string target
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where
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(name = "indexOf" or name = "includes" or name = "startsWith" or name = "endsWith") and
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call.getMethodName() = name and
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substring = call.getArgument(0) and
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substring.mayHaveStringValue(target) and
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(
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// target contains a domain on a common TLD, and perhaps some other URL components
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target.regexpMatch("(?i)([a-z]*:?//)?\\.?([a-z0-9-]+\\.)+(com|org|edu|gov|uk|net)(:[0-9]+)?/?") or
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// target is a HTTP URL to a domain on any TLD
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target.regexpMatch("(?i)https?://([a-z0-9-]+\\.)+([a-z]+)(:[0-9]+)?/?")
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) and
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// whitelist
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not (
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name = "indexOf" and
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(
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// arithmetic on the indexOf-result
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any(ArithmeticExpr e).getAnOperand().getUnderlyingValue() = call.asExpr()
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or
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// non-trivial position check on the indexOf-result
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exists(EqualityTest test, Expr n |
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test.hasOperands(call.asExpr(), n) |
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not n.getIntValue() = [-1..0]
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)
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)
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or
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// the leading dot in a subdomain sequence makes the suffix-check safe (if it is performed on the host of the url)
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name = "endsWith" and
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target.regexpMatch("(?i)\\.([a-z0-9-]+)(\\.[a-z0-9-]+)+")
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or
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// the trailing slash makes the prefix-check safe
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(
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name = "startsWith"
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or
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name = "indexOf" and
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exists(EqualityTest test, Expr n |
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test.hasOperands(call.asExpr(), n) and
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n.getIntValue() = 0
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)
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) and
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target.regexpMatch(".*/")
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)
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select call, "'$@' may be at an arbitrary position in the sanitized URL.", substring, target

‎javascript/ql/src/Security/CWE-020/examples/IncompleteUrlSubstringSanitization_BAD1.js‎

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app.get('/some/path', function(req, res) {
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let url = req.param("url");
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// BAD: the host of `url` may be controlled by an attacker
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if (url.includes("example.com")) {
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res.redirect(url);
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}
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});

‎javascript/ql/src/Security/CWE-020/examples/IncompleteUrlSubstringSanitization_BAD2.js‎

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app.get('/some/path', function(req, res) {
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let url = req.param("url"),
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host = urlLib.parse(url).host;
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// BAD: the host of `url` may be controlled by an attacker
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if (host.includes("example.com")) {
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res.redirect(url);
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}
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});

‎javascript/ql/src/Security/CWE-020/examples/IncompleteUrlSubstringSanitization_GOOD.js‎

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app.get('/some/path', function(req, res) {
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let url = req.param('url'),
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host = urlLib.parse(url).host;
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// GOOD: the host of `url` can not be controlled by an attacker
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let allowedHosts = [
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'example.com',
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'beta.example.com',
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'www.example.com'
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];
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if (allowedHosts.includes(host)) {
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res.redirect(url);
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}
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});

‎javascript/ql/test/query-tests/Security/CWE-020/IncompleteUrlSubstringSanitization.expected‎

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| tst-IncompleteUrlSubstringSanitization.js:4:5:4:27 | x.index ... e.com") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:4:15:4:26 | "secure.com" | secure.com |
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| tst-IncompleteUrlSubstringSanitization.js:5:5:5:27 | x.index ... e.net") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:5:15:5:26 | "secure.net" | secure.net |
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| tst-IncompleteUrlSubstringSanitization.js:6:5:6:28 | x.index ... e.com") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:6:15:6:27 | ".secure.com" | .secure.com |
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| tst-IncompleteUrlSubstringSanitization.js:10:5:10:27 | x.index ... e.com") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:10:15:10:26 | "secure.com" | secure.com |
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| tst-IncompleteUrlSubstringSanitization.js:11:5:11:27 | x.index ... e.com") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:11:15:11:26 | "secure.com" | secure.com |
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| tst-IncompleteUrlSubstringSanitization.js:12:5:12:27 | x.index ... e.com") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:12:15:12:26 | "secure.com" | secure.com |
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| tst-IncompleteUrlSubstringSanitization.js:14:5:14:38 | x.start ... e.com") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:14:18:14:37 | "https://secure.com" | https://secure.com |
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| tst-IncompleteUrlSubstringSanitization.js:15:5:15:28 | x.endsW ... e.com") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:15:16:15:27 | "secure.com" | secure.com |
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| tst-IncompleteUrlSubstringSanitization.js:20:5:20:28 | x.inclu ... e.com") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:20:16:20:27 | "secure.com" | secure.com |
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| tst-IncompleteUrlSubstringSanitization.js:32:5:32:35 | x.index ... e.com") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:32:15:32:34 | "https://secure.com" | https://secure.com |
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| tst-IncompleteUrlSubstringSanitization.js:33:5:33:39 | x.index ... m:443") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:33:15:33:38 | "https: ... om:443" | https://secure.com:443 |
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| tst-IncompleteUrlSubstringSanitization.js:34:5:34:36 | x.index ... .com/") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:34:15:34:35 | "https: ... e.com/" | https://secure.com/ |
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| tst-IncompleteUrlSubstringSanitization.js:52:5:52:41 | x.index ... ernal") | '$@' may be at an arbitrary position in the sanitized URL. | tst-IncompleteUrlSubstringSanitization.js:52:15:52:40 | "https: ... ternal" | https://example.internal |

‎javascript/ql/test/query-tests/Security/CWE-020/IncompleteUrlSubstringSanitization.qlref‎

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Security/CWE-020/IncompleteUrlSubstringSanitization.ql

‎javascript/ql/test/query-tests/Security/CWE-020/tst-IncompleteUrlSubstringSanitization.js‎

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(function(x){
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x.indexOf("internal"); // NOT OK, but not flagged
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x.indexOf("localhost"); // NOT OK, but not flagged
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x.indexOf("secure.com"); // NOT OK
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x.indexOf("secure.net"); // NOT OK
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x.indexOf(".secure.com"); // NOT OK
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x.indexOf("sub.secure."); // NOT OK, but not flagged
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x.indexOf(".sub.secure."); // NOT OK, but not flagged
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x.indexOf("secure.com") === -1; // NOT OK
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x.indexOf("secure.com") === 0; // NOT OK
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x.indexOf("secure.com") >= 0; // NOT OK
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x.startsWith("https://secure.com"); // NOT OK
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x.endsWith("secure.com"); // NOT OK
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x.endsWith(".secure.com"); // OK
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x.startsWith("secure.com/"); // OK
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x.indexOf("secure.com/") === 0; // OK
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x.includes("secure.com"); // NOT OK
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x.indexOf("#"); // OK
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x.indexOf(":"); // OK
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x.indexOf(":/"); // OK
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x.indexOf("://"); // OK
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x.indexOf("//"); // OK
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x.indexOf(":443"); // OK
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x.indexOf("/some/path/"); // OK
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x.indexOf("some/path"); // OK
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x.indexOf("/index.html"); // OK
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x.indexOf(":template:"); // OK
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x.indexOf("https://secure.com"); // NOT OK
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x.indexOf("https://secure.com:443"); // NOT OK
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x.indexOf("https://secure.com/"); // NOT OK
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x.indexOf(".cn"); // NOT OK, but not flagged
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x.indexOf(".jpg"); // OK
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x.indexOf("index.html"); // OK
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x.indexOf("index.js"); // OK
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x.indexOf("index.php"); // OK
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x.indexOf("index.css"); // OK
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x.indexOf("secure=true"); // OK (query param)
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x.indexOf("&auth="); // OK (query param)
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x.indexOf(getCurrentDomain()); // NOT OK, but not flagged
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x.indexOf(location.origin); // NOT OK, but not flagged
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x.indexOf("tar.gz") + offset // OK
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x.indexOf("tar.gz") - offset // OK
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x.indexOf("https://example.internal"); // NOT OK
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x.indexOf("https://"); // OK
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});

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