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Change compression prior to encryption for best results #351

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Change compression prior to encryption for best results #351

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12 changes: 5 additions & 7 deletions utils/crypto.py
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Original file line number Diff line number Diff line change
Expand Up @@ -19,25 +19,23 @@ def encrypt_text(text: str, secret_key: str | bytes) -> str:
if isinstance(secret_key, str):
secret_key = secret_key.encode("utf-8")
cipher = AES.new(secret_key.ljust(32)[:32], AES.MODE_CBC, iv)
encoded_text = text.encode("utf-8")
encoded_text = zlib.compress(text.encode("utf-8"))
encrypted_data = cipher.encrypt(
encoded_text + b"\0" * (16 - len(encoded_text) % 16)
)
compressed_data = zlib.compress(iv + encrypted_data)
encrypted_str = urlsafe_b64encode(compressed_data).decode("utf-8")
encrypted_str = urlsafe_b64encode(iv + encrypted_data).decode("utf-8")
return encrypted_str


def decrypt_text(secret_str: str, secret_key: str | bytes) -> str:
decoded_data = urlsafe_b64decode(secret_str)
encrypted_data = zlib.decompress(decoded_data)
iv = encrypted_data[:16]
iv = decoded_data[:16]
if isinstance(secret_key, str):
secret_key = secret_key.encode("utf-8")
cipher = AES.new(secret_key.ljust(32)[:32], AES.MODE_CBC, iv)
decrypted_data = cipher.decrypt(encrypted_data[16:])
decrypted_data = cipher.decrypt(decoded_data[16:])
Comment on lines +32 to +36
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⚠️ Potential issue

Add input validation for IV and ciphertext

The function lacks crucial input validation which could lead to security issues:

  1. No validation of IV length (should be 16 bytes)
  2. No validation of decoded data length (should be at least IV length + block size)

Apply this fix:

 decoded_data = urlsafe_b64decode(secret_str)
+ if len(decoded_data) < 32:  # minimum length: 16 (IV) + 16 (one AES block)
+     raise ValueError("Invalid encrypted data length")
 iv = decoded_data[:16]
 if isinstance(secret_key, str):
     secret_key = secret_key.encode("utf-8")
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
iv = decoded_data[:16]
if isinstance(secret_key, str):
secret_key = secret_key.encode("utf-8")
cipher = AES.new(secret_key.ljust(32)[:32], AES.MODE_CBC, iv)
decrypted_data = cipher.decrypt(encrypted_data[16:])
decrypted_data = cipher.decrypt(decoded_data[16:])
decoded_data = urlsafe_b64decode(secret_str)
if len(decoded_data) < 32: # minimum length: 16 (IV) + 16 (one AES block)
raise ValueError("Invalid encrypted data length")
iv = decoded_data[:16]
if isinstance(secret_key, str):
secret_key = secret_key.encode("utf-8")
cipher = AES.new(secret_key.ljust(32)[:32], AES.MODE_CBC, iv)
decrypted_data = cipher.decrypt(decoded_data[16:])

decrypted_data = decrypted_data.rstrip(b"\0")
return decrypted_data.decode("utf-8")
return zlib.decompress(decrypted_data).decode("utf-8")
Comment on lines 37 to +38
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⚠️ Potential issue

Add error handling and backward compatibility

The decompression step lacks error handling and breaks backward compatibility with existing encrypted data.

  1. Add error handling for decompression:
 decrypted_data = decrypted_data.rstrip(b"\0")
- return zlib.decompress(decrypted_data).decode("utf-8")
+ try:
+     return zlib.decompress(decrypted_data).decode("utf-8")
+ except zlib.error:
+     # Attempt backward compatibility with uncompressed data
+     try:
+         return decrypted_data.decode("utf-8")
+     except UnicodeDecodeError:
+         raise ValueError("Failed to decrypt: invalid data format")
  1. Consider adding a version byte to the encrypted data to properly handle both compressed and uncompressed formats:
# In encrypt_text:
version = b'\x01'  # Version 1: compressed
encrypted_str = urlsafe_b64encode(version + iv + encrypted_data).decode("utf-8")

# In decrypt_text:
version = decoded_data[0:1]
iv = decoded_data[1:17]
if version == b'\x01':
    # Handle compressed data
else:
    # Handle uncompressed data



def encrypt_user_data(user_data: UserData) -> str:
Expand Down