93 lines
1.9 KiB
Go
93 lines
1.9 KiB
Go
package util
|
|
|
|
import (
|
|
"crypto/aes"
|
|
"crypto/cipher"
|
|
"crypto/rand"
|
|
"encoding/base64"
|
|
"encoding/json"
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
"time"
|
|
)
|
|
|
|
var ErrStateExpired = fmt.Errorf("state expired")
|
|
|
|
const stateValidity = 2 * time.Minute
|
|
|
|
type State struct {
|
|
Time time.Time
|
|
}
|
|
|
|
func NewState() State {
|
|
return State{
|
|
Time: time.Now(),
|
|
}
|
|
}
|
|
|
|
func DecryptState(enc string, key []byte) (*State, error) {
|
|
ciphertext, err := base64.URLEncoding.DecodeString(enc)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("failed to base64 decode encrypted state: %w", err)
|
|
}
|
|
|
|
block, err := aes.NewCipher(key)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// The IV needs to be unique, but not secure. Therefore it's common to
|
|
// include it at the beginning of the ciphertext.
|
|
if len(ciphertext) < aes.BlockSize {
|
|
return nil, errors.New("ciphertext too short")
|
|
}
|
|
|
|
iv := ciphertext[:aes.BlockSize]
|
|
ciphertext = ciphertext[aes.BlockSize:]
|
|
|
|
stream := cipher.NewCFBDecrypter(block, iv)
|
|
|
|
// XORKeyStream can work in-place if the two arguments are the same.
|
|
stream.XORKeyStream(ciphertext, ciphertext)
|
|
|
|
var state State
|
|
err = json.Unmarshal(ciphertext, &state)
|
|
|
|
return &state, err
|
|
}
|
|
|
|
func (c *State) Encrypt(key []byte) string {
|
|
plain, err := json.Marshal(c)
|
|
if err != nil {
|
|
panic(err)
|
|
}
|
|
|
|
block, err := aes.NewCipher(key)
|
|
if err != nil {
|
|
panic(err)
|
|
}
|
|
|
|
// The IV needs to be unique, but not secure. Therefore it's common to
|
|
// include it at the beginning of the ciphertext.
|
|
ciphertext := make([]byte, aes.BlockSize+len(plain))
|
|
|
|
iv := ciphertext[:aes.BlockSize]
|
|
if _, err := io.ReadFull(rand.Reader, iv); err != nil {
|
|
panic(err)
|
|
}
|
|
|
|
stream := cipher.NewCFBEncrypter(block, iv)
|
|
stream.XORKeyStream(ciphertext[aes.BlockSize:], plain)
|
|
|
|
// convert to base64
|
|
return base64.URLEncoding.EncodeToString(ciphertext)
|
|
}
|
|
|
|
func (c *State) Validate() error {
|
|
if time.Since(c.Time) > stateValidity {
|
|
return nil
|
|
}
|
|
|
|
return ErrStateExpired
|
|
}
|