Add DES CBC decryption for wrapped key imports

README.md

@@ -18,7 +18,8 @@ AES-CBC does not authenticate ciphertext. Callers must authenticate the initiali
 ### DES
 
 - factory methods to construct an DES or 3DES cipher from the raw key bytes or hex text
-- encrypt & decrypt methods
+- ECB encrypt & decrypt methods
+- CBC decryption with an explicit 8-byte IV, without padding removal or authentication
 - verify the constructed cipher against the check value
 
 ### KEK Bundle

VERSION.txt

@@ -1 +1 @@
-1.14.0
+1.15.0

des/des_cbc_cipher.go

@@ -0,0 +1,33 @@
+/*
+	Licensed under the Apache License, Version 2.0 (the "License");
+	you may not use this file except in compliance with the License.
+	You may obtain a copy of the License at
+		http://www.apache.org/licenses/LICENSE-2.0
+	Unless required by applicable law or agreed to in writing, software
+	distributed under the License is distributed on an "AS IS" BASIS,
+	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+	See the License for the specific language governing permissions and
+	limitations under the License.
+*/
+package des
+
+import (
+	"crypto/cipher"
+	"fmt"
+)
+
+// DecryptCBC decrypts non-empty, block-aligned ciphertext using the supplied IV.
+// It does not remove padding or authenticate the ciphertext.
+func (c *Cipher) DecryptCBC(cipherBytes, iv []byte) ([]byte, error) {
+	blockSize := c.KeyBlock.BlockSize()
+	if len(iv) != blockSize {
+		return nil, fmt.Errorf("IV must be %d bytes", blockSize)
+	}
+	if len(cipherBytes) == 0 || len(cipherBytes)%blockSize != 0 {
+		return nil, fmt.Errorf("ciphertext must be a non-empty multiple of %d bytes", blockSize)
+	}
+
+	plainBytes := make([]byte, len(cipherBytes))
+	cipher.NewCBCDecrypter(c.KeyBlock, iv).CryptBlocks(plainBytes, cipherBytes)
+	return plainBytes, nil
+}

des/des_cbc_cipher_test.go

@@ -0,0 +1,81 @@
+/*
+	Licensed under the Apache License, Version 2.0 (the "License");
+	you may not use this file except in compliance with the License.
+	You may obtain a copy of the License at
+		http://www.apache.org/licenses/LICENSE-2.0
+	Unless required by applicable law or agreed to in writing, software
+	distributed under the License is distributed on an "AS IS" BASIS,
+	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+	See the License for the specific language governing permissions and
+	limitations under the License.
+*/
+package des
+
+import (
+	"bytes"
+	"encoding/hex"
+	"testing"
+)
+
+func TestTripleDESDecryptCBC(t *testing.T) {
+	// Independent Python cryptography/OpenSSL vectors: plaintext bytes 00..1f,
+	// no padding. The first two cases use double-length 3DES (K1, K2, K1).
+	tests := []struct {
+		name, key, iv, ciphertext string
+	}{
+		{"double-length zero IV", "0123456789ABCDEFFEDCBA9876543210", "0000000000000000", "52c5c0705d9089e1fd2f0cf61dd3bc0ac0a3e54b8860076a1ec9453c5a31bf0f"},
+		{"double-length nonzero IV", "0123456789ABCDEFFEDCBA9876543210", "1234567890abcdef", "188508514eeb60d24f8e125f9c2754e977bcc79e1c71911de0f7ed47b084f209"},
+		{"triple-length zero IV", "0123456789ABCDEFFEDCBA987654321089ABCDEF01234567", "0000000000000000", "98f447d72bee8df72fc757753238f778ad817caff7455eadc9121c8a11c8ad16"},
+		{"triple-length nonzero IV", "0123456789ABCDEFFEDCBA987654321089ABCDEF01234567", "1234567890abcdef", "dab10e76a31ef60dda6931da2244e63db6eec753a1774b4e7a6663c9805ff5f6"},
+	}
+	expected := make([]byte, 32)
+	for i := range expected {
+		expected[i] = byte(i)
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c, err := CreateFromTripleDESKeyString(tt.key)
+			if err != nil {
+				t.Fatal(err)
+			}
+			iv, _ := hex.DecodeString(tt.iv)
+			ciphertext, _ := hex.DecodeString(tt.ciphertext)
+			for i := 0; i < 2; i++ {
+				plaintext, err := c.DecryptCBC(ciphertext, iv)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if !bytes.Equal(plaintext, expected) {
+					t.Fatal("plaintext does not match the independent vector")
+				}
+			}
+			if hex.EncodeToString(ciphertext) != tt.ciphertext || hex.EncodeToString(iv) != tt.iv {
+				t.Fatal("decryption modified the ciphertext or IV")
+			}
+		})
+	}
+}
+
+func TestDecryptCBCRejectsInvalidInput(t *testing.T) {
+	c, err := CreateFromTripleDESKeyString("0123456789ABCDEFFEDCBA9876543210")
+	if err != nil {
+		t.Fatal(err)
+	}
+	tests := []struct {
+		name           string
+		ciphertext, iv []byte
+	}{
+		{"missing IV", make([]byte, 8), nil},
+		{"short IV", make([]byte, 8), make([]byte, 7)},
+		{"long IV", make([]byte, 8), make([]byte, 9)},
+		{"empty ciphertext", nil, make([]byte, 8)},
+		{"unaligned ciphertext", make([]byte, 9), make([]byte, 8)},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if plaintext, err := c.DecryptCBC(tt.ciphertext, tt.iv); err == nil || plaintext != nil {
+				t.Fatal("expected an error and no plaintext")
+			}
+		})
+	}
+}