pixa/internal/seal/crypto_test.go

package seal_test

import (
	"bytes"
	"errors"
	"testing"

	"sneak.berlin/go/pixa/internal/seal"
)

func TestDeriveKey_Consistent(t *testing.T) {
	t.Parallel()

	masterKey := []byte("test-master-key-12345")
	salt := "test-salt-v1"

	key1, err := seal.DeriveKey(masterKey, salt)
	if err != nil {
		t.Fatalf("DeriveKey() error = %v", err)
	}

	key2, err := seal.DeriveKey(masterKey, salt)
	if err != nil {
		t.Fatalf("DeriveKey() error = %v", err)
	}

	if key1 != key2 {
		t.Error("DeriveKey() should produce consistent keys for same input")
	}
}

func TestDeriveKey_DifferentSalts(t *testing.T) {
	t.Parallel()

	masterKey := []byte("test-master-key-12345")

	key1, err := seal.DeriveKey(masterKey, "salt-1")
	if err != nil {
		t.Fatalf("DeriveKey() error = %v", err)
	}

	key2, err := seal.DeriveKey(masterKey, "salt-2")
	if err != nil {
		t.Fatalf("DeriveKey() error = %v", err)
	}

	if key1 == key2 {
		t.Error("DeriveKey() should produce different keys for different salts")
	}
}

func TestDeriveKey_DifferentMasterKeys(t *testing.T) {
	t.Parallel()

	salt := "test-salt"

	key1, err := seal.DeriveKey([]byte("master-key-1"), salt)
	if err != nil {
		t.Fatalf("DeriveKey() error = %v", err)
	}

	key2, err := seal.DeriveKey([]byte("master-key-2"), salt)
	if err != nil {
		t.Fatalf("DeriveKey() error = %v", err)
	}

	if key1 == key2 {
		t.Error("DeriveKey() should produce different keys for different master keys")
	}
}

func TestEncryptDecrypt_RoundTrip(t *testing.T) {
	t.Parallel()

	key, err := seal.DeriveKey([]byte("test-key"), "test-salt")
	if err != nil {
		t.Fatalf("DeriveKey() error = %v", err)
	}

	plaintext := []byte("hello, world! this is a test message.")

	ciphertext, err := seal.Encrypt(key, plaintext)
	if err != nil {
		t.Fatalf("Encrypt() error = %v", err)
	}

	decrypted, err := seal.Decrypt(key, ciphertext)
	if err != nil {
		t.Fatalf("Decrypt() error = %v", err)
	}

	if !bytes.Equal(plaintext, decrypted) {
		t.Errorf("Decrypt() = %q, want %q", decrypted, plaintext)
	}
}

func TestEncryptDecrypt_EmptyPlaintext(t *testing.T) {
	t.Parallel()

	key, _ := seal.DeriveKey([]byte("test-key"), "test-salt")
	plaintext := []byte{}

	ciphertext, err := seal.Encrypt(key, plaintext)
	if err != nil {
		t.Fatalf("Encrypt() error = %v", err)
	}

	decrypted, err := seal.Decrypt(key, ciphertext)
	if err != nil {
		t.Fatalf("Decrypt() error = %v", err)
	}

	if !bytes.Equal(plaintext, decrypted) {
		t.Errorf("Decrypt() = %q, want %q", decrypted, plaintext)
	}
}

func TestDecrypt_WrongKey(t *testing.T) {
	t.Parallel()

	key1, _ := seal.DeriveKey([]byte("key-1"), "salt")
	key2, _ := seal.DeriveKey([]byte("key-2"), "salt")

	plaintext := []byte("secret message")

	ciphertext, err := seal.Encrypt(key1, plaintext)
	if err != nil {
		t.Fatalf("Encrypt() error = %v", err)
	}

	_, err = seal.Decrypt(key2, ciphertext)
	if err == nil {
		t.Error("Decrypt() should fail with wrong key")
	}

	if !errors.Is(err, seal.ErrDecryptionFailed) {
		t.Errorf("Decrypt() error = %v, want %v", err, seal.ErrDecryptionFailed)
	}
}

func TestDecrypt_TamperedCiphertext(t *testing.T) {
	t.Parallel()

	key, _ := seal.DeriveKey([]byte("test-key"), "test-salt")
	plaintext := []byte("secret message")

	ciphertext, err := seal.Encrypt(key, plaintext)
	if err != nil {
		t.Fatalf("Encrypt() error = %v", err)
	}

	// Tamper with the ciphertext (flip a bit in the middle)
	tampered := []byte(ciphertext)
	if len(tampered) > 10 {
		tampered[10] ^= 0x01
	}

	_, err = seal.Decrypt(key, string(tampered))
	if err == nil {
		t.Error("Decrypt() should fail with tampered ciphertext")
	}
}

func TestDecrypt_InvalidBase64(t *testing.T) {
	t.Parallel()

	key, _ := seal.DeriveKey([]byte("test-key"), "test-salt")

	_, err := seal.Decrypt(key, "not-valid-base64!!!")
	if err == nil {
		t.Error("Decrypt() should fail with invalid base64")
	}

	if !errors.Is(err, seal.ErrInvalidPayload) {
		t.Errorf("Decrypt() error = %v, want %v", err, seal.ErrInvalidPayload)
	}
}

func TestDecrypt_TooShort(t *testing.T) {
	t.Parallel()

	key, _ := seal.DeriveKey([]byte("test-key"), "test-salt")

	// Create a base64 string that's too short to contain nonce + auth tag
	_, err := seal.Decrypt(key, "dG9vLXNob3J0")
	if err == nil {
		t.Error("Decrypt() should fail with too-short ciphertext")
	}

	if !errors.Is(err, seal.ErrInvalidPayload) {
		t.Errorf("Decrypt() error = %v, want %v", err, seal.ErrInvalidPayload)
	}
}

func TestEncrypt_ProducesDifferentCiphertexts(t *testing.T) {
	t.Parallel()

	key, _ := seal.DeriveKey([]byte("test-key"), "test-salt")
	plaintext := []byte("same message")

	ciphertext1, _ := seal.Encrypt(key, plaintext)
	ciphertext2, _ := seal.Encrypt(key, plaintext)

	if ciphertext1 == ciphertext2 {
		t.Error("Encrypt() should produce different ciphertexts due to random nonce")
	}
}