Update project structure and build process

libwallet/aescbc/aescbc.go

@@ -0,0 +1,83 @@
+package aescbc
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"errors"
+	"fmt"
+)
+
+const KeySize = 32
+
+func EncryptPkcs7(key []byte, iv []byte, plaintext []byte) ([]byte, error) {
+	plaintext = pkcs7Padding(plaintext)
+	return EncryptNoPadding(key, iv, plaintext)
+}
+
+func EncryptNoPadding(key []byte, iv []byte, plaintext []byte) ([]byte, error) {
+	if len(key) != KeySize {
+		return nil, fmt.Errorf("invalid key size, expected %v, got %v", KeySize, len(key))
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	ciphertext := make([]byte, len(plaintext))
+
+	mode := cipher.NewCBCEncrypter(block, iv)
+	mode.CryptBlocks(ciphertext, plaintext)
+
+	return ciphertext, nil
+}
+
+func DecryptPkcs7(key []byte, iv []byte, cypertext []byte) ([]byte, error) {
+	paddedPlaintext, err := DecryptNoPadding(key, iv, cypertext)
+	if err != nil {
+		return nil, err
+	}
+
+	return pkcs7UnPadding(paddedPlaintext)
+}
+
+func DecryptNoPadding(key []byte, iv []byte, cypertext []byte) ([]byte, error) {
+	if len(key) != KeySize {
+		return nil, fmt.Errorf("invalid key size, expected %v, got %v", KeySize, len(key))
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	plaintext := make([]byte, len(cypertext))
+
+	mode := cipher.NewCBCDecrypter(block, iv)
+	mode.CryptBlocks(plaintext, cypertext)
+
+	return plaintext, nil
+}
+
+func pkcs7Padding(src []byte) []byte {
+	padding := aes.BlockSize - len(src)%aes.BlockSize
+	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
+	return append(src, padtext...)
+}
+
+func pkcs7UnPadding(src []byte) ([]byte, error) {
+	length := len(src)
+	unpadding := int(src[length-1])
+
+	if unpadding > aes.BlockSize || unpadding == 0 {
+		return nil, errors.New("invalid pkcs7 padding (unpadding > aes.BlockSize || unpadding == 0)")
+	}
+
+	pad := src[len(src)-unpadding:]
+	for i := 0; i < unpadding; i++ {
+		if pad[i] != byte(unpadding) {
+			return nil, errors.New("invalid pkcs7 padding (pad[i] != unpadding)")
+		}
+	}
+
+	return src[:(length - unpadding)], nil
+}

libwallet/aescbc/aescbc_test.go

@@ -0,0 +1,36 @@
+package aescbc
+
+import (
+	"bytes"
+	"crypto/rand"
+	"testing"
+)
+
+func TestEncryptionWithPkcs7Padding(t *testing.T) {
+	key := randomBytes(32)
+	iv := randomBytes(16)
+
+	plaintext := []byte("foobar")
+	ciphertext, err := EncryptPkcs7(key, iv, plaintext)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	decrypted, err := DecryptPkcs7(key, iv, ciphertext)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(decrypted, plaintext) {
+		t.Fatalf("expected decrypted text to match plaintext")
+	}
+}
+
+func randomBytes(count int) []byte {
+	buf := make([]byte, count)
+	_, err := rand.Read(buf)
+	if err != nil {
+		panic("couldn't read random bytes")
+	}
+
+	return buf
+}