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Fix partial path traversal Java example Again #12735

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Merged
atorralba merged 3 commits into from
Apr 3, 2023
Merged

Fix partial path traversal Java example Again #12735

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e641505
Fix partial path traversal Java example Again
JLLeitschuh Mar 31, 2023
b9d4092
Update java/ql/src/Security/CWE/CWE-023/PartialPathTraversalRemainder…
JLLeitschuh Mar 31, 2023
0d774a6
Fix partial path traversal Java example Again
JLLeitschuh Mar 31, 2023
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2 changes: 1 addition & 1 deletion java/ql/src/Security/CWE/CWE-023/PartialPathTraversalBad.java
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
public class PartialPathTraversalBad {
public void example(File dir, File parent) throws IOException {
if (!dir.getCanonicalPath().startsWith(parent.getCanonicalPath())) {
throw new IOException("Invalid directory: " + dir.getCanonicalPath());
throw new IOException("Path traversal attempt: " + dir.getCanonicalPath());
}
}
}
6 changes: 4 additions & 2 deletions java/ql/src/Security/CWE/CWE-023/PartialPathTraversalGood.java
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Original file line number Diff line number Diff line change
@@ -1,7 +1,9 @@
import java.io.File;

public class PartialPathTraversalGood {
public void example(File dir, File parent) throws IOException {
if (!dir.getCanonicalPath().startsWith(parent.getCanonicalPath() + File.separator)) {
throw new IOException("Invalid directory: " + dir.getCanonicalPath());
if (!dir.toPath().normalize().startsWith(parent.toPath())) {
throw new IOException("Path traversal attempt: " + dir.getCanonicalPath());
}
}
}
7 changes: 3 additions & 4 deletions java/ql/src/Security/CWE/CWE-023/PartialPathTraversalRemainder.inc.qhelp
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Expand Up @@ -26,10 +26,9 @@ and not just children of <code>parent</code>, which is a security issue.

<p>

In this example, the <code>if</code> statement checks if <code>parent.getCanonicalPath() + File.separator </code>
is a prefix of <code>dir.getCanonicalPath()</code>. Because <code>parent.getCanonicalPath() + File.separator</code> is
indeed slash-terminated, the user supplying <code>dir</code> can only access children of
<code>parent</code>, as desired.
In this example, the <code>if</code> statement checks if <code>parent.toPath()</code>
is a prefix of <code>dir.normalize()</code>. Because <code>Path#startsWith</code> does the correct check that
<code>dir</code> is a child of <code>parent</code>, users will not be able to access siblings of <code>parent</code>, as desired.

</p>

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6 changes: 6 additions & 0 deletions java/ql/test/query-tests/security/CWE-023/semmle/tests/PartialPathTraversalTest.java
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Expand Up @@ -225,6 +225,12 @@ void foo24(File dir, File parent) throws IOException {
}
}

public void doesNotFlagOptimalSafeVersion(File dir, File parent) throws IOException {
if (!dir.toPath().normalize().startsWith(parent.toPath())) { // Safe
throw new IOException("Path traversal attempt: " + dir.getCanonicalPath());
}
}

public void doesNotFlag() {
"hello".startsWith("goodbye");
}
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