Ruby OpenSSL Library - IV Reuse in GCM Mode

An IV reuse bug was discovered in Ruby's OpenSSL library when using aes-gcm. When encrypting data with aes-*-gcm, if the IV is set before setting the key, the cipher will default to using a static IV. This creates a static nonce and since aes-gcm is a stream cipher, this can lead to known …

def encrypt(plaintext)
    cipher = OpenSSL::Cipher.new('aes-256-gcm')
    iv = cipher.random_iv # Notice here the IV is set before the key
    cipher.key = '11111111111111111111111111111111'
    cipher.auth_data = ""
    ciphertext = cipher.update(plaintext) + cipher.final
    tag = …