T09 · Insecure Skill Coding Practices
Error
- Location
- ransomware_protection.py:66
- Finding
- File integrity verification accepts altered files without comparing hashes<![CDATA[ ## Vulnerability Details **File Location**: `ransomware_protection.py:66-84` **Vulnerability Type**: Improper integrity validation **Risk Level**: High ### Vulnerable Code ```python try: sha256 = hashlib.sha256() with open(filepath, 'rb') as f: for chunk in iter(lambda: f.read(8192), b''): sha256.update(chunk) current_hash = sha256.hexdigest().upper()[:16] # Load the original proof proof_list = load_proof_list() if original_proof_id in str(proof_list): # Simplified verification: should actually compare hashes result["verified"] = True result["message"] = "File integrity verification passed" result["current_hash"] = current_hash else: result["message"] = "Original proof record not found" except Exception as e: result["message"] = f"Verification failed: {str(e)}" ``` ### Technical Analysis The function calculates the current file hash but never compares it with the hash recorded when the proof was created. Instead, it marks the file as verified whenever the supplied proof identifier appears anywhere in the proof-list representation. Proof existence and file integrity are separate security properties. The existence of a proof identifier does not demonstrate that the current file has the same content as the originally proven file. The implementation consequently provides a false-positive integrity result for modified, substituted, or ransomware-encrypted files. Using only the first 16 hexadecimal characters of SHA-256 also reduces the effective digest from 256 bits to 64 bits. Although this is not the primary bypass, full SHA-256 values should be retained for security-sensitive integrity checks. ### Attack Path 1. An attacker or user obtains any proof identifier present in the local proof list. 2. The protected file is modified, replaced, corrupted, or encrypted. 3. `verify_file_integrity()` is called with the altered file and the existing proof identifie ...[truncated 677 chars]
- Remediation
- <![CDATA[ ## Remediation Suggestions 1. Store a complete SHA-256 digest in a structured proof record at proof-creation time. 2. Retrieve the exact record associated with `original_proof_id`; do not search a string representation. 3. Recalculate the complete SHA-256 digest of the current file. 4. Compare the two digests using exact equality, preferably `hmac.compare_digest()`. 5. Return success only if the proof exists, the record is structurally valid, and both hashes match. 6. Distinguish between `proof_not_found`, `hash_mismatch`, `file_unreadable`, and `verified` results. 7. Add tests covering modified files, substituted files, invalid proof IDs, malformed records, and hash mismatches. ]]>
