🛡️ Sentinel: [HIGH] Fix Insecure File Upload (Magic Bytes Validation)#70
🛡️ Sentinel: [HIGH] Fix Insecure File Upload (Magic Bytes Validation)#70Krosebrook wants to merge 1 commit intomainfrom
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- Add FLAC and AAC support to `detectAudioFormat` in `server/replit_integrations/audio/client.ts`. - Enforce magic byte validation in `server/routes.ts` for `/api/audio/generate-with-reference`. - Reject uploads with mismatching or unknown magic bytes to prevent malicious file uploads. - Update `AudioFormat` type definition to include `flac` and `aac`. This addresses a security vulnerability where files were only validated by their client-provided MIME type. Co-authored-by: Krosebrook <214532761+Krosebrook@users.noreply.github.com>
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Summary of ChangesHello @Krosebrook, 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 significantly enhances the security posture of the audio upload endpoint by moving beyond client-provided Highlights
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📝 WalkthroughWalkthroughThe changes implement server-side audio file validation using magic byte detection to replace insecure header-based validation. The AudioFormat detection function now recognizes FLAC and AAC formats, and the API endpoint validates uploaded files against detected formats before processing, returning an error if validation fails. Changes
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Code Review
This pull request effectively addresses a critical security vulnerability by introducing server-side magic byte validation for file uploads. The implementation is straightforward and correctly placed within the request lifecycle to reject invalid files early. The detectAudioFormat function has been appropriately extended to support FLAC and AAC formats. I've added one minor suggestion to improve the readability of the new format detection logic.
| if (buffer[0] === 0x66 && buffer[1] === 0x4c && buffer[2] === 0x61 && buffer[3] === 0x43) { | ||
| return "flac"; | ||
| } |
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For improved readability and maintainability, you can use buffer.toString() to check for the 'fLaC' magic string instead of comparing bytes individually. This makes the intent of the code clearer.
| if (buffer[0] === 0x66 && buffer[1] === 0x4c && buffer[2] === 0x61 && buffer[3] === 0x43) { | |
| return "flac"; | |
| } | |
| if (buffer.toString('ascii', 0, 4) === 'fLaC') { | |
| return "flac"; | |
| } |
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Reviewed commit: d90fc94c97
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| } | ||
| // AAC: ADTS header (FFF1 or FFF9 usually) | ||
| // Sync word is 12 bits of 1s (0xFFF) | ||
| if (buffer[0] === 0xff && (buffer[1] & 0xf0) === 0xf0) { |
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The new AAC branch classifies any buffer starting with 0xFF and a high nibble of 0xF as valid AAC, which is too permissive for a security gate. Since /api/audio/generate-with-reference now accepts any non-unknown format, an attacker can craft arbitrary non-audio bytes with a FF F0 prefix and a spoofed audio MIME type to bypass the new server-side content check. This undermines the upload validation the commit intends to enforce; the ADTS header check needs additional bit constraints before returning "aac".
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Pull request overview
This PR adds server-side magic byte validation to the audio file upload endpoint to prevent malicious file uploads. The change addresses a security vulnerability where the previous implementation relied solely on client-provided MIME type headers, which can be easily spoofed.
Changes:
- Enhanced
detectAudioFormatfunction to support FLAC and AAC audio formats with magic byte detection - Added magic byte validation to the
/api/audio/generate-with-referenceendpoint that rejects files with unknown formats - Updated Sentinel documentation with the vulnerability details and prevention guidance
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| server/replit_integrations/audio/client.ts | Added FLAC (fLaC) and AAC (ADTS) magic byte detection patterns; updated AudioFormat type to include new formats |
| server/routes.ts | Added detectAudioFormat import and magic byte validation check that rejects uploads with unknown format |
| .jules/sentinel.md | Documented the insecure file upload vulnerability and prevention measures |
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| // Sentinel: Validate magic bytes | ||
| const detectedFormat = detectAudioFormat(file.buffer); | ||
| if (detectedFormat === "unknown") { |
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File upload validation failures should be logged for security monitoring, following the pattern established in the codebase memories. When magic byte validation fails, log the failure with sanitizeLog() including relevant context like userId, fileSize, mimetype, and originalName. This helps detect and track potential malicious upload attempts. Example pattern: console.warn("File upload validation failed:", sanitizeLog({ userId: req.user.claims.sub, fileSize: file.size, mimetype: file.mimetype, originalName: file.originalname }));
| if (detectedFormat === "unknown") { | |
| if (detectedFormat === "unknown") { | |
| console.warn( | |
| "File upload validation failed:", | |
| sanitizeLog({ | |
| userId: req.user?.claims?.sub, | |
| fileSize: file.size, | |
| mimetype: file.mimetype, | |
| originalName: file.originalname, | |
| }), | |
| ); |
| } | ||
| // AAC: ADTS header (FFF1 or FFF9 usually) | ||
| // Sync word is 12 bits of 1s (0xFFF) | ||
| if (buffer[0] === 0xff && (buffer[1] & 0xf0) === 0xf0) { |
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The AAC detection pattern (buffer[1] & 0xf0) === 0xf0 will create false positives by matching MP3 files. MP3 sync frames start with 0xFF followed by bytes like 0xFB, 0xFA, or 0xF3 (all have upper nibble 0xF0). Since the AAC check comes after the MP3 check, any MP3 file that doesn't have an ID3 tag and uses a frame sync byte not explicitly listed in the MP3 check (like 0xF2, 0xF1, 0xF9, etc.) will be misidentified as AAC.
The memory from the codebase indicates that AAC ADTS files should use explicit checks for 0xFF 0xF1 (MPEG-4) and 0xFF 0xF9 (MPEG-2) rather than bit masking to avoid ambiguity with MP3 sync frames. Consider using explicit byte value checks instead of the bitmask pattern.
| if (buffer[0] === 0xff && (buffer[1] & 0xf0) === 0xf0) { | |
| if (buffer[0] === 0xff && (buffer[1] === 0xf1 || buffer[1] === 0xf9)) { |
| return res.status(400).json({ message: "Reference audio file is required" }); | ||
| } | ||
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| // Sentinel: Validate magic bytes |
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Do not use branded prefixes like "Sentinel:" in comments. Based on the coding guidelines and established codebase conventions, simple descriptive comments should be used instead. Replace "Sentinel: Validate magic bytes" with just "Validate magic bytes".
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🧹 Nitpick comments (2)
server/replit_integrations/audio/client.ts (2)
112-112: Stale comment — FLAC and AAC now also follow this conversion path.📝 Suggested comment update
- // Convert WebM, MP4, OGG, or unknown to WAV + // Convert WebM, MP4, OGG, FLAC, AAC, or unknown to WAV🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed. In `@server/replit_integrations/audio/client.ts` at line 112, Update the stale inline comment that currently reads "Convert WebM, MP4, OGG, or unknown to WAV" to reflect the current supported formats — include FLAC and AAC (e.g. "Convert WebM, MP4, OGG, FLAC, AAC, or unknown to WAV") so it matches the actual conversion path in the audio handling code (look for the conversion block in client.ts where files are normalized to WAV).
50-54: Consider tightening the ADTS mask to avoid misidentifying MPEG-2 MP3 as AAC.The ADTS header's Layer field (bits 2–1 of byte 1) must be
00, so valid ADTS/AAC second bytes are only{0xF0, 0xF1, 0xF8, 0xF9}. The current mask0xF0matches the full range0xF0–0xFF, which includes0xF2(MPEG-2 Layer3 MP3 with CRC protection) — a value the earlier MP3 branch doesn't cover (0xFB,0xFA,0xF3only). That MPEG-2+CRC variant would fall through and be labelled"aac".Security impact is nil (the file still passes as a known audio format), but the format label could affect downstream routing in
ensureCompatibleFormat. Applying the0xF6mask (1111 0110) validates both the sync nibble and the layer bits simultaneously:♻️ Suggested precision fix
- if (buffer[0] === 0xff && (buffer[1] & 0xf0) === 0xf0) { + // Layer bits (2-1) must be 00 per ADTS spec; valid byte-1 values: 0xF0, 0xF1, 0xF8, 0xF9 + if (buffer[0] === 0xff && (buffer[1] & 0xf6) === 0xf0) { return "aac"; }🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed. In `@server/replit_integrations/audio/client.ts` around lines 50 - 54, The ADTS/AAC detection check (if (buffer[0] === 0xff && (buffer[1] & 0xf0) === 0xf0)) is too broad and can misidentify MPEG-2 Layer3 variants as AAC; change the second-byte mask to validate the Layer bits as well by using (buffer[1] & 0xF6) === 0xF0 so only {0xF0,0xF1,0xF8,0xF9} match and MPEG-2 MP3 values like 0xF2 are excluded.
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.
Nitpick comments:
In `@server/replit_integrations/audio/client.ts`:
- Line 112: Update the stale inline comment that currently reads "Convert WebM,
MP4, OGG, or unknown to WAV" to reflect the current supported formats — include
FLAC and AAC (e.g. "Convert WebM, MP4, OGG, FLAC, AAC, or unknown to WAV") so it
matches the actual conversion path in the audio handling code (look for the
conversion block in client.ts where files are normalized to WAV).
- Around line 50-54: The ADTS/AAC detection check (if (buffer[0] === 0xff &&
(buffer[1] & 0xf0) === 0xf0)) is too broad and can misidentify MPEG-2 Layer3
variants as AAC; change the second-byte mask to validate the Layer bits as well
by using (buffer[1] & 0xF6) === 0xF0 so only {0xF0,0xF1,0xF8,0xF9} match and
MPEG-2 MP3 values like 0xF2 are excluded.
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1 issue found across 3 files
Prompt for AI agents (all issues)
Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.
<file name="server/replit_integrations/audio/client.ts">
<violation number="1" location="server/replit_integrations/audio/client.ts:52">
P2: AAC detection is too permissive. The ADTS header requires layer bits = 00; only checking the 0xFFF syncword can misclassify non-AAC data and bypass the new validation. Tighten the check to validate the layer bits (and other fixed-header bits if desired).</violation>
</file>
Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.
| } | ||
| // AAC: ADTS header (FFF1 or FFF9 usually) | ||
| // Sync word is 12 bits of 1s (0xFFF) | ||
| if (buffer[0] === 0xff && (buffer[1] & 0xf0) === 0xf0) { |
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P2: AAC detection is too permissive. The ADTS header requires layer bits = 00; only checking the 0xFFF syncword can misclassify non-AAC data and bypass the new validation. Tighten the check to validate the layer bits (and other fixed-header bits if desired).
Prompt for AI agents
Check if this issue is valid — if so, understand the root cause and fix it. At server/replit_integrations/audio/client.ts, line 52:
<comment>AAC detection is too permissive. The ADTS header requires layer bits = 00; only checking the 0xFFF syncword can misclassify non-AAC data and bypass the new validation. Tighten the check to validate the layer bits (and other fixed-header bits if desired).</comment>
<file context>
@@ -43,6 +43,15 @@ export function detectAudioFormat(buffer: Buffer): AudioFormat {
+ }
+ // AAC: ADTS header (FFF1 or FFF9 usually)
+ // Sync word is 12 bits of 1s (0xFFF)
+ if (buffer[0] === 0xff && (buffer[1] & 0xf0) === 0xf0) {
+ return "aac";
+ }
</file context>
| if (buffer[0] === 0xff && (buffer[1] & 0xf0) === 0xf0) { | |
| if ( | |
| buffer[0] === 0xff && | |
| (buffer[1] & 0xf0) === 0xf0 && | |
| (buffer[1] & 0x06) === 0x00 | |
| ) { |
1 participant
This PR addresses a security vulnerability in the audio upload endpoint (
/api/audio/generate-with-reference). Previously, file validation relied solely on theContent-Typeheader provided by the client, which can be easily spoofed. This change implements server-side magic byte validation to ensure that uploaded files are legitimate audio files before processing.Changes:
detectAudioFormat: Updatedserver/replit_integrations/audio/client.tsto support FLAC (fLaC) and AAC (ADTS) magic bytes.server/routes.tsto calldetectAudioFormaton the uploaded file buffer. If the format is unknown or invalid, the request is rejected with a 400 status code.AudioFormattype to include new supported formats.This creates a defense-in-depth layer against malicious file uploads.
PR created automatically by Jules for task 6579330852988766958 started by @Krosebrook
Summary by cubic
Enforces server-side magic byte validation for audio uploads to block spoofed MIME types. Rejects invalid files with a 400 response before processing.
Written for commit d90fc94. Summary will update on new commits.
Summary by CodeRabbit
Bug Fixes
New Features