Insecure Use of Cryptography
Why is this important?
Cryptography is hard. And when it is used in an application, it's usually to make sure user data is secure in transit and at rest. Unfortunately, cryptographic libraries are not always easy to use. They require proper configuration and settings to ensure the data is safe.
Check out this video for a high-level explanation:
Fixing Insecure Use of Cryptography
Option A: Use Strong Message Digest
The algorithms SHA-1, MD2, MD4 and MD5 are not a recommended MessageDigest. The
security of the MD5 hash function is severely compromised. A collision attack
exists that can find collisions within seconds on a computer with a 2.6 GHz
Pentium 4 processor. Further, there is also a chosen-prefix collision attack
that can produce a collision for two inputs with specified prefixes within
hours, using off-the-shelf computing hardware.
PBKDF2 with SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, or SHA-512/256 are
acceptable for all hash function use-cases.
Detailed Instructions
- Go through the issues that GuardRails identified in the PR.
- Identify the code like:
MessageDigest md5Digest = MessageDigest.getInstance("MD5");
md5Digest.update(password.getBytes());
byte[] hashValue = md5Digest.digest();
- And replace it with:
// Java 8 or higher
public static byte[] getEncryptedPassword(String password, byte[] salt) throws NoSuchAlgorithmException, InvalidKeySpecException {
KeySpec spec = new PBEKeySpec(password.toCharArray(), salt, 4096, 256 * 8);
SecretKeyFactory f = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
return f.generateSecret(spec).getEncoded();
}
- Test it
- Ship it 🚢 and relax 🌴
References
- Qualys blog: SHA1 Deprecation: What You Need to Know
- Google Online Security Blog: Gradually sunsetting SHA-1
- NIST: Transitions: Recommendation for Transitioning the Use of Cryptographic Algorithms and Key Lengths
- Stackoverflow: Reliable implementation of PBKDF2-HMAC-SHA256 for Java
- CWE-327: Use of a Broken or Risky Cryptographic Algorithm
Option B: Use Strong Ciphers
Cryptography is a complex topic and there are many ways it can be used insecurely.
The following issues are identified by GuardRails and can be easily avoided.
NullCipher
The NullCipher is rarely used intentionally in production applications. It implements the Cipher interface by returning ciphertext identical to the supplied plaintext and as such serves no security value.
ECB Mode
An authentication cipher mode which provides better confidentiality of the encrypted data should be used instead of Electronic Code Book (ECB) mode, which does not provide good confidentiality. Specifically, ECB mode produces the same output for the same input each time. So, for example, if a user is sending a password, the encrypted value is the same each time. This allows an attacker to intercept and replay the data.
Padding Oracle
This specific mode of CBC with PKCS5Padding is susceptible to padding oracle attacks. An adversary could potentially decrypt the message if the system exposed the difference between plaintext with invalid padding or valid padding. The distinction between valid and invalid padding is usually revealed through distinct error messages being returned for each condition.
Cipher Integrity
The ciphertext produced is susceptible to alteration by an adversary. This means that the cipher provides no way to detect that the data has been tampered with. If the ciphertext can be controlled by an attacker, it could be altered without detection.
Detailed Instructions
- Go through the issues that GuardRails identified in the PR.
- Identify the code like this:
// NullCipher
Cipher doNothingCihper = new NullCipher();
[...]
//The ciphertext produced will be identical to the plaintext.
byte[] cipherText = c.doFinal(plainText);
or:
// ECB Mode
Cipher c = Cipher.getInstance("AES/ECB/NoPadding");
c.init(Cipher.ENCRYPT_MODE, k, iv);
byte[] cipherText = c.doFinal(plainText);
or:
Cipher c = Cipher.getInstance("AES/CBC/PKCS5Padding");
c.init(Cipher.ENCRYPT_MODE, k, iv);
byte[] cipherText = c.doFinal(plainText);
- And replace it with a proper cryptographic operation.
Cipher c = Cipher.getInstance("AES/GCM/NoPadding");
c.init(Cipher.ENCRYPT_MODE, k, iv);
byte[] cipherText = c.doFinal(plainText);
- Test it
- Ship it 🚢 and relax 🌴
References
Option C: Use RSA with propper padding
Using the RSA algorithm without Optimal Asymmetric Encryption Padding (OAEP) weakens the encryption.
Detailed Instructions
- Go through the issues that GuardRails identified in the PR.
- Identify the code like this:
Cipher.getInstance("RSA/NONE/NoPadding");
- And replace it with:
Cipher.getInstance("RSA/ECB/OAEPWithMD5AndMGF1Padding")
- Test it
- Ship it 🚢 and relax 🌴
References
Option D: Use Strong Key Sizes
The Blowfish cipher supports key sizes from 32 bits to 448 bits. A small key size makes the ciphertext vulnerable to brute force attacks. At least 128 bits of entropy should be used when generating the key if use of Blowfish is required.
For the RSA algorithm the use of 2048 bits and higher is recommended.
Detailed Instructions
- Go through the issues that GuardRails identified in the PR.
- Identify the code like this:
// Vulnerable Blowfish example
KeyGenerator keyGen = KeyGenerator.getInstance("Blowfish");
keyGen.init(64);
and ensure the minimum acceptable key size of 128 is used:
// Blowfish example
KeyGenerator keyGen = KeyGenerator.getInstance("Blowfish");
keyGen.init(128);
or alternatively, for RSA, identify code like this:
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(512);
and ensure the minimum acceptable key size of 2048 is used:
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(2048);
- Test it
- Ship it 🚢 and relax 🌴