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Use of a weak cryptographic initialization vector

go.weak_encryption_initialization_vector

Severity

critical

Resource

Cryptography

Language

Description

The improper use of initialization vectors (IVs) in encryption can weaken data security by enabling pattern detection and making the ciphertext vulnerable to attacks. It’s critical to ensure the IV is generated securely and used correctly to maintain encryption strength.

Rationale

Initialization vectors (IVs) are crucial in encryption schemes like CBC or GCM to ensure the same plaintext results in different ciphertexts. A weak or improperly used IV, such as a static or predictable one, can allow attackers to uncover patterns in the data, leading to potential data leaks or unauthorized access.

Consider the following Golang code:

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"fmt"
)

func main() {
	key := []byte("mysecretencryptionkey")
	iv := []byte("0000000000000000")

	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}

	stream := cipher.NewCFBEncrypter(block, iv) // FLAW
	plaintext := []byte("secret message")
	ciphertext := make([]byte, len(plaintext))

	stream.XORKeyStream(ciphertext, plaintext)

	fmt.Printf("Ciphertext: %x\n", ciphertext)
}

Remediation

To remediate issues with weak or improperly used IVs, ensure they are generated securely and uniquely for each encryption operation.

The remediation example for Golang would look like this:

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"fmt"
	"io"
)

func main() {
	key := []byte("mysecretencryptionkey")

	// Generate a random IV
	iv := make([]byte, aes.BlockSize)
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		panic(err)
	}

	block, err := aes.NewCipher(key)
	if err != nil {
		panic(err)
	}

	stream := cipher.NewCFBEncrypter(block, iv)
	plaintext := []byte("secret message")
	ciphertext := make([]byte, len(plaintext))

	stream.XORKeyStream(ciphertext, plaintext)

	fmt.Printf("IV: %x\n", iv)
	fmt.Printf("Ciphertext: %x\n", ciphertext)
}

References

CWE-1204 : Generation of Weak Initialization Vector (IV).