135 lines
3.6 KiB
Go
135 lines
3.6 KiB
Go
package cryptography
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import (
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"crypto/aes"
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"crypto/cipher"
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"crypto/rand"
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"errors"
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"io"
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)
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const (
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// AES key sizes in bytes
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AES128KeySize = 16 // 128 bits
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AES192KeySize = 24 // 192 bits
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AES256KeySize = 32 // 256 bits
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// Default to AES-256
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DefaultKeySize = AES256KeySize
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)
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// GenerateAESKey generates a random AES key of the specified size
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func GenerateAESKey(keySize int) ([]byte, error) {
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if keySize != AES128KeySize && keySize != AES192KeySize && keySize != AES256KeySize {
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return nil, errors.New("invalid key size: must be 16, 24, or 32 bytes")
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}
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key := make([]byte, keySize)
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if _, err := io.ReadFull(rand.Reader, key); err != nil {
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return nil, err
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}
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return key, nil
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}
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// GenerateAES256Key generates a random AES-256 key (default)
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func GenerateAES256Key() ([]byte, error) {
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return GenerateAESKey(AES256KeySize)
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}
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// EncryptAES256CBC encrypts data using AES-256 in CBC mode
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func EncryptAES256CBC(key, plaintext []byte) ([]byte, error) {
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if len(key) != AES256KeySize {
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return nil, errors.New("key must be 32 bytes for AES-256")
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}
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return EncryptAESCBC(key, plaintext)
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}
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// DecryptAES256CBC decrypts data using AES-256 in CBC mode
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func DecryptAES256CBC(key, ciphertext []byte) ([]byte, error) {
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if len(key) != AES256KeySize {
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return nil, errors.New("key must be 32 bytes for AES-256")
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}
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return DecryptAESCBC(key, ciphertext)
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}
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// EncryptAESCBC encrypts data using AES in CBC mode (accepts any valid AES key size)
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func EncryptAESCBC(key, plaintext []byte) ([]byte, error) {
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// Validate key size
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if len(key) != AES128KeySize && len(key) != AES192KeySize && len(key) != AES256KeySize {
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return nil, errors.New("invalid key size: must be 16, 24, or 32 bytes")
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}
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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// Generate IV
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iv := make([]byte, aes.BlockSize)
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if _, err := io.ReadFull(rand.Reader, iv); err != nil {
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return nil, err
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}
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// Add PKCS7 padding
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padding := aes.BlockSize - len(plaintext)%aes.BlockSize
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padtext := make([]byte, len(plaintext)+padding)
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copy(padtext, plaintext)
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for i := len(plaintext); i < len(padtext); i++ {
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padtext[i] = byte(padding)
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}
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// Encrypt
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mode := cipher.NewCBCEncrypter(block, iv)
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ciphertext := make([]byte, len(padtext))
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mode.CryptBlocks(ciphertext, padtext)
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return append(iv, ciphertext...), nil
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}
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// DecryptAESCBC decrypts data using AES in CBC mode (accepts any valid AES key size)
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func DecryptAESCBC(key, ciphertext []byte) ([]byte, error) {
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// Validate key size
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if len(key) != AES128KeySize && len(key) != AES192KeySize && len(key) != AES256KeySize {
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return nil, errors.New("invalid key size: must be 16, 24, or 32 bytes")
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}
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block, err := aes.NewCipher(key)
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if err != nil {
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return nil, err
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}
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if len(ciphertext) < aes.BlockSize {
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return nil, errors.New("ciphertext too short")
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}
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iv := ciphertext[:aes.BlockSize]
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ciphertext = ciphertext[aes.BlockSize:]
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if len(ciphertext)%aes.BlockSize != 0 {
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return nil, errors.New("ciphertext is not a multiple of block size")
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}
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mode := cipher.NewCBCDecrypter(block, iv)
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plaintext := make([]byte, len(ciphertext))
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mode.CryptBlocks(plaintext, ciphertext)
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// Remove PKCS7 padding
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if len(plaintext) == 0 {
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return nil, errors.New("invalid padding: empty plaintext")
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}
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padding := int(plaintext[len(plaintext)-1])
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if padding == 0 || padding > aes.BlockSize || padding > len(plaintext) {
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return nil, errors.New("invalid PKCS7 padding")
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}
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// Verify all padding bytes are correct
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for i := len(plaintext) - padding; i < len(plaintext); i++ {
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if plaintext[i] != byte(padding) {
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return nil, errors.New("invalid PKCS7 padding")
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}
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}
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return plaintext[:len(plaintext)-padding], nil
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}
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