status-go/protocol/encryption/helpers.go

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package encryption
import (
"crypto/aes"
"crypto/cipher"
"crypto/ecdsa"
"crypto/rand"
"encoding/binary"
"errors"
"io"
"time"
"github.com/status-im/status-go/eth-node/crypto"
"github.com/status-im/status-go/eth-node/crypto/ecies"
)
const keyBumpValue = uint64(10)
// GetCurrentTime64 returns the current unix time in milliseconds
func GetCurrentTime() uint64 {
return (uint64)(time.Now().UnixNano() / int64(time.Millisecond))
}
// bumpKeyID takes a timestampID and returns its value incremented by the keyBumpValue
func bumpKeyID(timestampID uint64) uint64 {
return timestampID + keyBumpValue
}
func generateHashRatchetKeyID(groupID []byte, timestamp uint64, keyBytes []byte) []byte {
var keyMaterial []byte
keyMaterial = append(keyMaterial, groupID...)
timestampBytes := make([]byte, 8) // 8 bytes for a uint64
binary.LittleEndian.PutUint64(timestampBytes, timestamp)
keyMaterial = append(keyMaterial, timestampBytes...)
keyMaterial = append(keyMaterial, keyBytes...)
return crypto.Keccak256(keyMaterial)
}
func publicKeyMostRelevantBytes(key *ecdsa.PublicKey) uint32 {
keyBytes := crypto.FromECDSAPub(key)
return binary.LittleEndian.Uint32(keyBytes[1:5])
}
func encrypt(plaintext []byte, key []byte, reader io.Reader) ([]byte, error) {
c, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
gcm, err := cipher.NewGCM(c)
if err != nil {
return nil, err
}
nonce := make([]byte, gcm.NonceSize())
if _, err = io.ReadFull(reader, nonce); err != nil {
return nil, err
}
return gcm.Seal(nonce, nonce, plaintext, nil), nil
}
func generateSharedKey(privateKey *ecdsa.PrivateKey, publicKey *ecdsa.PublicKey) ([]byte, error) {
const encryptedPayloadKeyLength = 16
return ecies.ImportECDSA(privateKey).GenerateShared(
ecies.ImportECDSAPublic(publicKey),
encryptedPayloadKeyLength,
encryptedPayloadKeyLength,
)
}
// buildGroupRekeyMessage builds a set of message with maxKeys in each message.
// each key adds roughly 70 bytes to the size of the message, so we want to stay
// clear of 1 MB / 70 keys (~14K keys)
func buildGroupRekeyMessage(privateKey *ecdsa.PrivateKey, groupID []byte, timestamp uint64, keyMaterial []byte, keys []*ecdsa.PublicKey, maxKeys int) ([]*RekeyGroup, error) {
message := &RekeyGroup{
Timestamp: timestamp,
}
message.Keys = make(map[uint32][]byte)
length := len(keys)
var messages []*RekeyGroup
for i := 0; i < length; i += maxKeys {
end := i + maxKeys
if end > length {
end = length
}
for _, k := range keys[i:end] {
sharedKey, err := generateSharedKey(privateKey, k)
if err != nil {
return nil, err
}
encryptedKey, err := encrypt(keyMaterial, sharedKey, rand.Reader)
if err != nil {
return nil, err
}
kBytes := publicKeyMostRelevantBytes(k)
if message.Keys[kBytes] == nil {
message.Keys[kBytes] = encryptedKey
} else {
message.Keys[kBytes] = append(message.Keys[kBytes], encryptedKey...)
}
}
messages = append(messages, message)
}
return messages, nil
}
const nonceLength = 12
func decrypt(cyphertext []byte, key []byte) ([]byte, error) {
if len(cyphertext) < nonceLength {
return nil, errors.New("invalid cyphertext length")
}
c, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
gcm, err := cipher.NewGCM(c)
if err != nil {
return nil, err
}
nonce := cyphertext[:nonceLength]
return gcm.Open(nil, nonce, cyphertext[nonceLength:], nil)
}
const keySize = 60
func decryptGroupRekeyMessage(privateKey *ecdsa.PrivateKey, publicKey *ecdsa.PublicKey, message *RekeyGroup) ([]byte, error) {
kBytes := publicKeyMostRelevantBytes(&privateKey.PublicKey)
if message.Keys == nil || message.Keys[kBytes] == nil {
return nil, nil
}
sharedKey, err := generateSharedKey(privateKey, publicKey)
if err != nil {
return nil, err
}
keys := message.Keys[kBytes]
nKeys := len(keys) / keySize
var decryptedKey []byte
for i := 0; i < nKeys; i++ {
encryptedKey := keys[i*keySize : i*keySize+keySize]
decryptedKey, err = decrypt(encryptedKey, sharedKey)
if err != nil {
continue
} else {
break
}
}
return decryptedKey, nil
}