135 lines
3.4 KiB
Go
135 lines
3.4 KiB
Go
package crypto
|
|
|
|
import (
|
|
"crypto/aes"
|
|
"crypto/cipher"
|
|
"crypto/rand"
|
|
"encoding/binary"
|
|
"fmt"
|
|
"math"
|
|
)
|
|
|
|
type AESGCMHelper struct {
|
|
key []byte
|
|
gcm cipher.AEAD
|
|
}
|
|
|
|
func NewAESGCMHelper(key []byte) (*AESGCMHelper, error) {
|
|
if len(key) != 32 {
|
|
return nil, fmt.Errorf("unsupported AES key length (got=%d expected=32)", len(key))
|
|
}
|
|
block, err := aes.NewCipher(key)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
gcm, err := cipher.NewGCM(block)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return &AESGCMHelper{key: key, gcm: gcm}, nil
|
|
}
|
|
|
|
func (c *AESGCMHelper) encryptChunk(data []byte, aad []byte) []byte {
|
|
nonce := make([]byte, c.gcm.NonceSize(), c.gcm.NonceSize()+len(data))
|
|
_, err := rand.Read(nonce)
|
|
if err != nil {
|
|
panic(fmt.Errorf("out of randomness: %w", err))
|
|
}
|
|
|
|
// Pass nonce as the dest, so we have it pre-appended to the output
|
|
return c.gcm.Seal(nonce, nonce, data, aad)
|
|
}
|
|
|
|
func (c *AESGCMHelper) decryptChunk(data []byte, aad []byte) ([]byte, error) {
|
|
if len(data) < c.gcm.NonceSize() {
|
|
return nil, fmt.Errorf("invalid encrypted data length (got=%d)", len(data))
|
|
}
|
|
|
|
nonce := data[:c.gcm.NonceSize()]
|
|
ciphertext := data[c.gcm.NonceSize():]
|
|
|
|
decrypted, err := c.gcm.Open(nil, nonce, ciphertext, aad)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return decrypted, nil
|
|
}
|
|
|
|
const outgoingRawChunkSize = 1 << 15
|
|
|
|
func (c *AESGCMHelper) EncryptData(data []byte) ([]byte, error) {
|
|
chunkOverhead := c.gcm.NonceSize() + c.gcm.Overhead()
|
|
chunkSize := outgoingRawChunkSize - chunkOverhead
|
|
|
|
chunkCount := int(math.Ceil(float64(len(data)) / float64(chunkSize)))
|
|
encrypted := make([]byte, 2, 2+len(data)+28*chunkCount)
|
|
encrypted[0] = 0
|
|
encrypted[1] = byte(math.Log2(float64(outgoingRawChunkSize)))
|
|
|
|
var chunkIndex uint32
|
|
for i := 0; i < len(data); i += chunkSize {
|
|
isLastChunk := false
|
|
if i+chunkSize >= len(data) {
|
|
chunkSize = len(data) - i
|
|
isLastChunk = true
|
|
}
|
|
|
|
chunk := make([]byte, chunkSize)
|
|
copy(chunk, data[i:i+chunkSize])
|
|
|
|
aad := c.calculateAAD(chunkIndex, isLastChunk)
|
|
encrypted = append(encrypted, c.encryptChunk(data[i:i+chunkSize], aad)...)
|
|
chunkIndex++
|
|
}
|
|
|
|
return encrypted, nil
|
|
}
|
|
|
|
func (c *AESGCMHelper) DecryptData(encryptedData []byte) ([]byte, error) {
|
|
if len(encryptedData) == 0 || len(c.key) != 32 {
|
|
return encryptedData, nil
|
|
}
|
|
if encryptedData[0] != 0 {
|
|
return nil, fmt.Errorf("invalid first-byte header signature (got=%o , expected=%o)", encryptedData[0], 0)
|
|
}
|
|
|
|
chunkSize := 1 << encryptedData[1]
|
|
encryptedData = encryptedData[2:]
|
|
|
|
var chunkIndex uint32
|
|
chunkCount := int(math.Ceil(float64(len(encryptedData)) / float64(chunkSize)))
|
|
decryptedData := make([]byte, 0, len(encryptedData)-28*chunkCount)
|
|
|
|
for i := 0; i < len(encryptedData); i += chunkSize {
|
|
isLastChunk := false
|
|
if i+chunkSize >= len(encryptedData) {
|
|
chunkSize = len(encryptedData) - i
|
|
isLastChunk = true
|
|
}
|
|
|
|
chunk := make([]byte, chunkSize)
|
|
copy(chunk, encryptedData[i:i+chunkSize])
|
|
|
|
aad := c.calculateAAD(chunkIndex, isLastChunk)
|
|
decryptedChunk, err := c.decryptChunk(chunk, aad)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("failed to decrypt chunk #%d: %w", chunkIndex+1, err)
|
|
}
|
|
decryptedData = append(decryptedData, decryptedChunk...)
|
|
chunkIndex++
|
|
}
|
|
|
|
return decryptedData, nil
|
|
}
|
|
|
|
func (c *AESGCMHelper) calculateAAD(index uint32, isLastChunk bool) []byte {
|
|
aad := make([]byte, 5)
|
|
binary.BigEndian.PutUint32(aad[1:5], index)
|
|
if isLastChunk {
|
|
aad[0] = 1
|
|
}
|
|
return aad
|
|
}
|