Testing for Weak Encryption (OTG-CRYPST-004)

Summary
Incorrect uses of encryption algorithm may result in sensitive data exposure, key leakage, broken authentication, insecure session and spoofing attack. There are some encryption or hash algorithm is known to be weak and not suggested to be used anymore such MD5 and RC4.

In addition to the right choices of secure encryption or hash algorithm, the right uses of parameters also mater the security level. For example, ECB (Electronic Code Book) mode is not suggested to be used in asymmetric encryption.

The testing guide is trying to provide a guideline how to identify the weak encryption and hash.

Basic Security Checklist
Key exchange: Diffie–Hellman key exchange with minimum 2048 bits Message Integrity: HMAC-SHA2 Message Hash: SHA2 256 bits Assymetric encryption: RSA 2048 bits Symmetric-key algorithm: AES 128 bits Password Hashing: PBKDF2, Scrypt, Bcrypt ECDH、ECDSA: 256 bits
 * When the uses of AES128 and AES256, The IV (Initialization vector) must be random and unpredictable. Refer to FIPS 140-2, Security Requirements for Cryptographic Modules, section 4.9.1. random number generator tests. For example, in Java, "java.util.Random" is considered a weak random number generator. "java.security.SecureRandom" should be used instead of "java.util.Random".
 * When uses of RSA in encryption, Optimal Asymmetric Encryption Padding (OAEP) mode is recommended.
 * When uses of RSA in signature, PSS padding is recommended.
 * Weak hash/encryption algorithms should not be used such MD5, RC4, DES, Blowfish, SHA1. 1024-bit RSA or DSA, 160-bit ECDSA (elliptic curves), 80/112-bit 2TDEA (two key triple DES)
 * Minimum Key length requirement:
 * Uses of SSH, CBC mode should not be used.
 * When symmetric encryption algorithm is used, ECB (Electronic Code Book) mode should not be used.
 * When PBKDF2 is used to hash password, the parameter of iteration is recommended to be over 10000. NIST also suggests at least 10,000 iterations of the hash function. In addition, MD5 hash function is forbidden to be used with PBKDF2 such as PBKDF2WithHmacMD5.

Source Code Review
MD4, MD5, RC4, RC2, DES, Blowfish, SHA-1, ECB
 * Search for the following keyword to check if any weak encryption algorithm is used.


 * For Java implementation, the following API is related to encyprtion. Review the parameters of the encryption implementation. For example,

SecretKeyFactory(SecretKeyFactorySpi keyFacSpi, Provider provider, String algorithm) SecretKeySpec(byte[] key, int offset, int len, String algorithm) Cipher c = Cipher.getInstance("DES/CBC/PKCS5Padding");

RSA/ECB/OAEPWithSHA-1AndMGF1Padding (2048) RSA/ECB/OAEPWithSHA-256AndMGF1Padding (2048)
 * For RSA encryption, the following padding mode are suggested.


 * Search for "ECB", it's not allowed to be used in padding.

// Use a different IV value for every encryption byte[] newIv = ...; s = new GCMParameterSpec(s.getTLen, newIv); cipher.init(..., s); ...
 * Review if different IV (initial Vector) is used.


 * Search for "IvParameterSpec", check if the IV value is generated differently and randomly.

IvParameterSpec iv = new IvParameterSpec(randBytes); SecretKeySpec skey = new SecretKeySpec(key.getBytes, "AES"); Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); cipher.init(Cipher.ENCRYPT_MODE, skey, iv);


 * In Java, search for MessageDigest to check if weak hash althorithm (MD5 or CRC) is used. For example:

MessageDigest md5 = MessageDigest.getInstance("MD5");

Signature sig = Signature.getInstance("SHA1withRSA");
 * For signature, SHA1 and MD5 should not be used. For example:

The iterations should be over 10000, and the salt value should be generated as random value.
 * Search for "PBKDF2". To generate the hash value of password, PBKDF2 is suggested to be used. Review the parameters to generate the PBKDF2 has value.

private static byte[] pbkdf2(char[] password, byte[] salt, int iterations, int bytes) throws NoSuchAlgorithmException, InvalidKeySpecException {       PBEKeySpec spec = new PBEKeySpec(password, salt, iterations, bytes * 8); SecretKeyFactory skf = SecretKeyFactory.getInstance(PBKDF2_ALGORITHM); return skf.generateSecret(spec).getEncoded; }

User related keywords: name, root, su, superuser, login, username, uid Key related keywords: public key, AK, SK, secret Key, private key, passwd, password, pwd, share key, cryto, base64 Other common senstive keywords: sysadmin, root, privilege, pass, key, code, master, admin, uname, session, joken, Oauth, priviatekey
 * Hard-coded senstive information

Tools
CWE-261: Weak Cryptography for Passwords CWE-323: Reusing a Nonce, Key Pair in Encryption. CWE-326: Inadequate Encryption Strength CWE-327: Use of a Broken or Risky Cryptographic Algorithm CWE-328: Reversible One-Way Hash CWE-329: Not Using a Random IV with CBC Mode CWE-330: Use of Insufficiently Random Values CWE-347: Improper Verification of Cryptographic Signature CWE-354: Improper Validation of Integrity Check Value CWE-547: Use of Hard-coded, Security-relevant Constants CWE-780 Use of RSA Algorithm without OAEP
 * Vulnerability scanner such as Nessus to scan weak encryption used in protocol such as SNMP, TLS,SSH
 * Use static code analysis tool to do source code review such as klocwork, Fortify, Coverity, CheckMark for the following cases.