Summary
The storage service's file upload handler trusts the client-provided Content-Type header without performing server-side MIME type detection. This allows an attacker to upload files with an arbitrary MIME type, bypassing any MIME-type-based restrictions configured on storage buckets.
Affected Component
- Service:
services/storage
- File:
services/storage/controller/upload_files.go
- Function:
getMultipartFile (lines 48-70)
Root Cause
In getMultipartFile, if the client provides a non-empty Content-Type header that isn't application/octet-stream, the function returns it as-is without performing content-based detection:
contentType := file.header.Header.Get("Content-Type")
if contentType != "" && contentType != "application/octet-stream" {
return fileContent, contentType, nil // skip detection entirely
}
// mimetype.DetectReader only reached if client sends no Content-Type
// or sends application/octet-stream
mt, err := mimetype.DetectReader(fileContent)Impact
Incorrect MIME type in file metadata. The MIME type stored in file metadata reflects what the client claims rather than what the file actually contains. Any system consuming this metadata (browsers, CDNs, applications) may handle the file incorrectly based on the spoofed type.
Suggested Fix
Always detect MIME type from file content using mimetype.DetectReader, ignoring the client-provided Content-Type header entirely.
References
- CWE-345: Insufficient Verification of Data Authenticity
- CWE-434: Unrestricted Upload of File with Dangerous Type
References
0xkakash1 Reporter
Summary
The storage service's file upload handler trusts the client-provided
Content-Typeheader without performing server-side MIME type detection. This allows an attacker to upload files with an arbitrary MIME type, bypassing any MIME-type-based restrictions configured on storage buckets.Affected Component
services/storageservices/storage/controller/upload_files.gogetMultipartFile(lines 48-70)Root Cause
In
getMultipartFile, if the client provides a non-emptyContent-Typeheader that isn'tapplication/octet-stream, the function returns it as-is without performing content-based detection:Impact
Incorrect MIME type in file metadata. The MIME type stored in file metadata reflects what the client claims rather than what the file actually contains. Any system consuming this metadata (browsers, CDNs, applications) may handle the file incorrectly based on the spoofed type.
Suggested Fix
Always detect MIME type from file content using
mimetype.DetectReader, ignoring the client-providedContent-Typeheader entirely.References
References