🛡️ Sentinel: [HIGH] Fix RTLO Spoofing in Folder Names by abhimehro · Pull Request #163 · abhimehro/ctrld-sync

abhimehro · 2026-02-05T11:02:42Z

🚨 Severity: HIGH
💡 Vulnerability: Folder names allowed Unicode Bidi control characters (e.g., RTLO), enabling Homograph/Spoofing attacks where a name like "safe\u202eexe.pdf" renders as "safepdf.exe". Also allowed path separators / and \ which could cause confusion.
🔧 Fix: Enhanced is_valid_folder_name to explicitly block Bidi control characters and path separators.
✅ Verification: Added new test cases in tests/test_folder_validation.py which pass.

PR created automatically by Jules for task 15718768312849110796 started by @abhimehro

- Block Unicode Bidi control characters (RTLO, etc.) in folder names to prevent spoofing. - Block path separators (/ and \) to prevent potential path confusion. - Update tests/test_folder_validation.py with new test cases. Co-authored-by: abhimehro <84992105+abhimehro@users.noreply.github.com>

google-labs-jules · 2026-02-05T11:02:44Z

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trunk-io · 2026-02-05T11:02:47Z

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gemini-code-assist · 2026-02-05T11:02:59Z

Summary of Changes

Hello @abhimehro, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a high-severity security vulnerability by enhancing folder name validation. It prevents homograph and spoofing attacks that leverage Unicode Bidi control characters and eliminates confusion caused by path separators in folder names. These changes significantly improve the security and integrity of folder naming conventions within the system.

Highlights

RTLO Spoofing Prevention: Implemented explicit blocking of Unicode Bidi control characters (U+202A-U+202E, U+2066-U+2069) in the is_valid_folder_name function to prevent homograph and spoofing attacks.
Path Separator Blocking: Added validation to block common path separators (/ and \) in folder names to avoid confusion and potential misuse.
Enhanced Test Coverage: Introduced new test cases in tests/test_folder_validation.py to verify the correct blocking of both Bidi control characters and path separators.
Vulnerability Documentation: A new markdown file, .jules/sentinel.md, was added to document the RTLO/Bidi Spoofing vulnerability, outlining its nature, learning points, and prevention strategy.

Changelog

.jules/sentinel.md
- Added a new file documenting the RTLO/Bidi Spoofing vulnerability, including its nature, learning points, and prevention strategy.
main.py
- Modified the is_valid_folder_name function to include new validation rules.
- Updated the dangerous_chars set to explicitly block path separators (/, \).
- Introduced a new bidi_chars set to block specific Unicode Bidi control characters (U+202A-U+202E, U+2066-U+2069).
- Updated the validation logic to check for both dangerous_chars and bidi_chars.
tests/test_folder_validation.py
- Added new test cases to test_folder_name_security to cover the updated validation logic.
- Included tests for folder names containing path separators (/, \).
- Added tests for folder names containing Bidi control characters (\u202e, \u202a).

Activity

This pull request was automatically generated by Jules for a task initiated by @abhimehro.

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tests/test_folder_validation.py


+        # Case 6: Path Separators
+        slash_data = {"group": {"group": "Folder/Name"}}
+        assert main.validate_folder_data(slash_data, "http://slash.com") is False


tests/test_folder_validation.py

+        assert main.validate_folder_data(slash_data, "http://slash.com") is False
+
+        backslash_data = {"group": {"group": "Folder\\Name"}}
+        assert main.validate_folder_data(backslash_data, "http://backslash.com") is False


tests/test_folder_validation.py

+        # Case 7: Bidi Control Characters (RTLO)
+        # \u202e is Right-To-Left Override
+        rtlo_data = {"group": {"group": "SafeName\u202eexe.pdf"}}
+        assert main.validate_folder_data(rtlo_data, "http://rtlo.com") is False


tests/test_folder_validation.py

+
+        # Case 8: Other Bidi Char
+        lre_data = {"group": {"group": "Name\u202a"}}
+        assert main.validate_folder_data(lre_data, "http://lre.com") is False


tests/test_folder_validation.py


+        # Case 6: Path Separators
+        slash_data = {"group": {"group": "Folder/Name"}}
+        assert main.validate_folder_data(slash_data, "http://slash.com") is False


tests/test_folder_validation.py

+        assert main.validate_folder_data(slash_data, "http://slash.com") is False
+
+        backslash_data = {"group": {"group": "Folder\\Name"}}
+        assert main.validate_folder_data(backslash_data, "http://backslash.com") is False


tests/test_folder_validation.py

+        # Case 7: Bidi Control Characters (RTLO)
+        # \u202e is Right-To-Left Override
+        rtlo_data = {"group": {"group": "SafeName\u202eexe.pdf"}}
+        assert main.validate_folder_data(rtlo_data, "http://rtlo.com") is False


tests/test_folder_validation.py

+
+        # Case 8: Other Bidi Char
+        lre_data = {"group": {"group": "Name\u202a"}}
+        assert main.validate_folder_data(lre_data, "http://lre.com") is False


.jules/sentinel.md

@@ -0,0 +1,4 @@
+## 2025-02-18 - [RTLO/Bidi Spoofing in Folder Names]


.jules/sentinel.md

@@ -0,0 +1,4 @@
+## 2025-02-18 - [RTLO/Bidi Spoofing in Folder Names]


Copilot

Pull request overview

This PR fixes a HIGH severity security vulnerability where folder names could contain Unicode Bidi control characters (particularly RTLO - Right-to-Left Override) and path separators, enabling spoofing attacks where malicious names like "safe\u202eexe.pdf" would render as "safepdf.exe", potentially misleading users about file types.

Changes:

Enhanced is_valid_folder_name() validation to explicitly block 9 Unicode Bidi control characters (U+202A through U+202E and U+2066 through U+2069) and path separators (/ and )
Added comprehensive test cases covering path separators and multiple Bidi control characters
Documented the vulnerability, learning, and prevention strategy in sentinel.md

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
main.py	Added blocking of path separators and Bidi control characters in folder name validation logic
tests/test_folder_validation.py	Added 4 new test cases (Cases 6-8) validating rejection of path separators and Bidi characters
.jules/sentinel.md	Created documentation entry describing the RTLO/Bidi spoofing vulnerability and mitigation

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Copilot · 2026-02-05T11:11:50Z

main.py

+    bidi_chars = {
+        "\u202a",
+        "\u202b",
+        "\u202c",
+        "\u202d",
+        "\u202e",
+        "\u2066",
+        "\u2067",
+        "\u2068",
+        "\u2069",
+    }


The bidi_chars set is recreated on every function call, which is inefficient. Consider moving it to module level as a constant (e.g., BIDI_CONTROL_CHARS) similar to how dangerous_chars is defined inline but could also be a constant. This would improve performance especially if this validation is called frequently.

Copilot · 2026-02-05T11:11:51Z

main.py

+    # Block Bidi control characters to prevent RTLO spoofing
+    # \u202a (LRE), \u202b (RLE), \u202c (PDF), \u202d (LRO), \u202e (RLO)
+    # \u2066 (LRI), \u2067 (RLI), \u2068 (FSI), \u2069 (PDI)
+    bidi_chars = {
+        "\u202a",
+        "\u202b",
+        "\u202c",
+        "\u202d",
+        "\u202e",
+        "\u2066",
+        "\u2067",
+        "\u2068",
+        "\u2069",
+    }


Consider also blocking U+200E (Left-to-Right Mark) and U+200F (Right-to-Left Mark) for completeness, as these can also be used for text direction manipulation attacks, though they are less severe than the override/embedding characters. While LRM and RLM are less dangerous than RTLO, blocking them would provide defense-in-depth for folder names where directional marks serve no legitimate purpose.

gemini-code-assist

Code Review

This pull request addresses a high-severity spoofing vulnerability (RTLO) in folder names by blocking Unicode Bidi control characters and path separators. The changes in main.py correctly implement the validation logic, and the accompanying tests in tests/test_folder_validation.py verify the fix. My review includes suggestions to improve performance in main.py by defining constant sets at the module level, and to enhance the test suite in tests/test_folder_validation.py for better coverage and maintainability. Specifically, I've pointed out that the test coverage for the newly blocked Bidi characters is incomplete, which is critical for a security fix. I've also suggested a small refactoring to reduce code duplication in the tests.

gemini-code-assist · 2026-02-05T11:12:46Z

tests/test_folder_validation.py

+        # Case 7: Bidi Control Characters (RTLO)
+        # \u202e is Right-To-Left Override
+        rtlo_data = {"group": {"group": "SafeName\u202eexe.pdf"}}
+        assert main.validate_folder_data(rtlo_data, "http://rtlo.com") is False
+
+        # Case 8: Other Bidi Char
+        lre_data = {"group": {"group": "Name\u202a"}}
+        assert main.validate_folder_data(lre_data, "http://lre.com") is False


The test coverage for the Bidi control characters is incomplete. The fix in main.py blocks 9 different characters, but the tests only cover 2 of them (\u202e and \u202a). For a security-related change, it's crucial to ensure all blocked characters are explicitly tested to prevent regressions.

Suggested change

# Case 7: Bidi Control Characters (RTLO)

# \u202e is Right-To-Left Override

rtlo_data = {"group": {"group": "SafeName\u202eexe.pdf"}}

assert main.validate_folder_data(rtlo_data, "http://rtlo.com") is False

# Case 8: Other Bidi Char

lre_data = {"group": {"group": "Name\u202a"}}

assert main.validate_folder_data(lre_data, "http://lre.com") is False

# Case 7: Bidi Control Characters

bidi_chars_to_test = {

"\u202a", "\u202b", "\u202c", "\u202d", "\u202e",

"\u2066", "\u2067", "\u2068", "\u2069",

}

for char in bidi_chars_to_test:

data = {"group": {"group": f"SafeName{char}exploit.exe"}}

assert main.validate_folder_data(data, "http://bidi.com") is False

gemini-code-assist · 2026-02-05T11:12:46Z

main.py

    dangerous_chars = set("<>\"'`")
-    if any(c in dangerous_chars for c in name):
+
+    # Block path separators to prevent confusion
+    dangerous_chars.update(["/", "\\"])
+
+    # Block Bidi control characters to prevent RTLO spoofing
+    # \u202a (LRE), \u202b (RLE), \u202c (PDF), \u202d (LRO), \u202e (RLO)
+    # \u2066 (LRI), \u2067 (RLI), \u2068 (FSI), \u2069 (PDI)
+    bidi_chars = {
+        "\u202a",
+        "\u202b",
+        "\u202c",
+        "\u202d",
+        "\u202e",
+        "\u2066",
+        "\u2067",
+        "\u2068",
+        "\u2069",
+    }


For performance, the dangerous_chars and bidi_chars sets are being recreated on every call to is_valid_folder_name. Since this function can be called frequently, it's more efficient to define these as module-level constants to avoid the overhead of set creation on each invocation.

For example, you could define them at the top of the file and reference them in the function:

# At module level _DANGEROUS_FOLDER_CHARS = set("<>\"'`/\\") _BIDI_CHARS = { "\u202a", "\u202b", "\u202c", "\u202d", "\u202e", "\u2066", "\u2067", "\u2068", "\u2069", } def is_valid_folder_name(name: str) -> bool: # ... (initial checks) if any(c in _DANGEROUS_FOLDER_CHARS or c in _BIDI_CHARS for c in name): return False return True

gemini-code-assist · 2026-02-05T11:12:46Z

tests/test_folder_validation.py

+        slash_data = {"group": {"group": "Folder/Name"}}
+        assert main.validate_folder_data(slash_data, "http://slash.com") is False
+
+        backslash_data = {"group": {"group": "Folder\\Name"}}
+        assert main.validate_folder_data(backslash_data, "http://backslash.com") is False


These two test cases for path separators are very similar. To reduce code duplication and improve maintainability, you can combine them into a single loop.

Suggested change

slash_data = {"group": {"group": "Folder/Name"}}

assert main.validate_folder_data(slash_data, "http://slash.com") is False

backslash_data = {"group": {"group": "Folder\\Name"}}

assert main.validate_folder_data(backslash_data, "http://backslash.com") is False

# Case 6: Path Separators

for separator in ("/", "\\"):

data = {"group": {"group": f"Folder{separator}Name"}}

assert main.validate_folder_data(data, "http://separator.com") is False

Security: Block Unicode Bidi control characters to prevent homograph attacks - Block 11 Bidi control characters (LRE, RLE, PDF, LRO, RLO, LRI, RLI, FSI, PDI, LRM, RLM) - Block path separators (/ and \) to prevent confusion - Move dangerous character sets to module-level constants for performance - Add comprehensive test coverage for all blocked characters - Test characters in different positions (start, middle, end) - Add security documentation explaining the vulnerability Addresses feedback from PR #163 Co-authored-by: abhimehro <84992105+abhimehro@users.noreply.github.com>

Copilot AI review requested due to automatic review settings February 5, 2026 11:02

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This was referenced Feb 8, 2026

Consolidate 36 Jules PRs: pre-compile regex, harden log sanitization, add dry-run plan details #175

Merged

Consolidate parallel deletion, RTLO prevention, and .env auto-fix from PRs #146, #149, #163, #164, #166 #176

Merged

Copilot AI mentioned this pull request Feb 9, 2026

Combine API access check and folder listing into single request; close stale Jules PRs #178

Merged

abhimehro closed this Feb 9, 2026

abhimehro deleted the sentinel-rtlo-fix-15718768312849110796 branch February 9, 2026 02:18

		@@ -0,0 +1,4 @@
		## 2025-02-18 - [RTLO/Bidi Spoofing in Folder Names]

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