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Normalizes path to prevent path traversal with "/./" #269

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Merged
bitterpanda63 merged 5 commits into from
Feb 6, 2026
Merged

Normalizes path to prevent path traversal with "/./" #269

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23d4235
Update by also parsing `/./` java path traversal injections
bitterpanda63 Feb 5, 2026
37a7ef3
startsWithUnsafePath: use the normalized path
bitterpanda63 Feb 5, 2026
c34685a
make normalizePath private & make sure the test cases use startsWithU…
bitterpanda63 Feb 5, 2026
ad5c75c
remove wrongful comment from UnsafePathChecker.java
bitterpanda63 Feb 5, 2026
0cd2d7d
Update regex to not be reliant on loops
bitterpanda63 Feb 6, 2026
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27 changes: 20 additions & 7 deletions .../src/main/java/dev/aikido/agent_api/vulnerabilities/path_traversal/UnsafePathChecker.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,13 @@
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;

public final class UnsafePathChecker {
private UnsafePathChecker() {}

private static final Pattern CURRENT_DIR_PATTERN = Pattern.compile("/(\\./)+");

private static final List<String> LINUX_ROOT_FOLDERS = Arrays.asList(
"/bin/",
"/boot/",
Expand Down Expand Up @@ -33,7 +37,7 @@ private UnsafePathChecker() {}
);

public static boolean startsWithUnsafePath(String filePathRaw) {
String filePath = ensureOneLeadingSlash(filePathRaw.toLowerCase());
String filePath = normalizePath(filePathRaw.toLowerCase());
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bitterpanda63 marked this conversation as resolved.

List<String> dangerousStartsList = new ArrayList<>(DANGEROUS_PATH_STARTS);
dangerousStartsList.addAll(LINUX_ROOT_FOLDERS);
Expand All @@ -47,15 +51,24 @@ public static boolean startsWithUnsafePath(String filePathRaw) {
}

public static boolean startsWithUnsafePath(String filePathRaw, String userInputRaw) {
String filePath = ensureOneLeadingSlash(filePathRaw.toLowerCase());
String userInput = ensureOneLeadingSlash(userInputRaw.toLowerCase());
String filePath = normalizePath(filePathRaw.toLowerCase());
String userInput = normalizePath(userInputRaw.toLowerCase());
return startsWithUnsafePath(filePath) && filePath.startsWith(userInput);
}

private static String ensureOneLeadingSlash(String path) {
if (path.startsWith("/")) {
return "/" + path.replaceAll("^/+", "");
/**
* Normalizes a path by removing /./ and removing consecutive slashes
*/
private static String normalizePath(String path) {
if (path == null || path.isEmpty()) {
return path;
}
return path;

// Matches /./ or /././ or /./././ etc. (one or more ./ sequences after a /)
String normalized = CURRENT_DIR_PATTERN.matcher(path).replaceAll("/");

// Merge consecutive slashes since these don't change where you are in the path.
normalized = normalized.replaceAll("/+", "/");
return normalized;
}
}
32 changes: 32 additions & 0 deletions agent_api/src/test/java/vulnerabilities/path_traversal/UnsafePathCheckerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -48,4 +48,36 @@ public void testMultipleSlashes() {
assertTrue(UnsafePathChecker.startsWithUnsafePath("///etc/passwd"));
assertFalse(UnsafePathChecker.startsWithUnsafePath("etc/passwd///../test.txt"));
}

@Test
public void testCurrentDirectoryReferences() {
// /./ should be normalized to /
assertTrue(UnsafePathChecker.startsWithUnsafePath("/./etc/passwd", "/./etc"));
assertTrue(UnsafePathChecker.startsWithUnsafePath("/etc/./passwd", "/etc"));
assertTrue(UnsafePathChecker.startsWithUnsafePath("/etc/./passwd", "/etc/./"));

assertTrue(UnsafePathChecker.startsWithUnsafePath("/./etc/passwd"));
assertTrue(UnsafePathChecker.startsWithUnsafePath("/etc/./passwd"));
assertTrue(UnsafePathChecker.startsWithUnsafePath("/./etc/./passwd"));

// Multiple /./ sequences
assertTrue(UnsafePathChecker.startsWithUnsafePath("/././etc/passwd", "/././etc"));
assertTrue(UnsafePathChecker.startsWithUnsafePath("/etc/././passwd"));
}

@Test
public void testPathNormalization() {
// Paths with multiple slashes and /./ should be normalized and detected
assertTrue(UnsafePathChecker.startsWithUnsafePath("//etc//passwd", "/etc"));
assertTrue(UnsafePathChecker.startsWithUnsafePath("/./etc/./passwd", "/etc"));
assertTrue(UnsafePathChecker.startsWithUnsafePath("/././etc/passwd", "/etc"));

// Paths without leading slash are not unsafe
assertFalse(UnsafePathChecker.startsWithUnsafePath("etc/passwd", "etc"));
assertFalse(UnsafePathChecker.startsWithUnsafePath("", ""));

// Combined slashes and dot: ///.///etc/passwd should normalize to /etc/passwd
assertTrue(UnsafePathChecker.startsWithUnsafePath("///.///etc/passwd", "///.///etc"));
assertTrue(UnsafePathChecker.startsWithUnsafePath("///.///etc/passwd"));
}
}