87 lines
2.2 KiB
Go
87 lines
2.2 KiB
Go
package mint
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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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"crypto/sha256"
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"fmt"
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"io"
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"golang.org/x/crypto/hkdf"
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)
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// CookieProtector is used to create and verify a cookie
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type CookieProtector interface {
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// NewToken creates a new token
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NewToken([]byte) ([]byte, error)
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// DecodeToken decodes a token
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DecodeToken([]byte) ([]byte, error)
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}
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const cookieSecretSize = 32
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const cookieNonceSize = 32
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// The DefaultCookieProtector is a simple implementation for the CookieProtector.
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type DefaultCookieProtector struct {
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secret []byte
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}
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var _ CookieProtector = &DefaultCookieProtector{}
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// NewDefaultCookieProtector creates a source for source address tokens
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func NewDefaultCookieProtector() (CookieProtector, error) {
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secret := make([]byte, cookieSecretSize)
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if _, err := rand.Read(secret); err != nil {
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return nil, err
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}
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return &DefaultCookieProtector{secret: secret}, nil
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}
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// NewToken encodes data into a new token.
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func (s *DefaultCookieProtector) NewToken(data []byte) ([]byte, error) {
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nonce := make([]byte, cookieNonceSize)
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if _, err := rand.Read(nonce); err != nil {
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return nil, err
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}
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aead, aeadNonce, err := s.createAEAD(nonce)
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if err != nil {
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return nil, err
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}
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return append(nonce, aead.Seal(nil, aeadNonce, data, nil)...), nil
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}
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// DecodeToken decodes a token.
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func (s *DefaultCookieProtector) DecodeToken(p []byte) ([]byte, error) {
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if len(p) < cookieNonceSize {
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return nil, fmt.Errorf("Token too short: %d", len(p))
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}
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nonce := p[:cookieNonceSize]
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aead, aeadNonce, err := s.createAEAD(nonce)
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if err != nil {
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return nil, err
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}
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return aead.Open(nil, aeadNonce, p[cookieNonceSize:], nil)
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}
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func (s *DefaultCookieProtector) createAEAD(nonce []byte) (cipher.AEAD, []byte, error) {
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h := hkdf.New(sha256.New, s.secret, nonce, []byte("mint cookie source"))
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key := make([]byte, 32) // use a 32 byte key, in order to select AES-256
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if _, err := io.ReadFull(h, key); err != nil {
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return nil, nil, err
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}
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aeadNonce := make([]byte, 12)
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if _, err := io.ReadFull(h, aeadNonce); err != nil {
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return nil, nil, err
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}
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c, err := aes.NewCipher(key)
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if err != nil {
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return nil, nil, err
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}
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aead, err := cipher.NewGCM(c)
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if err != nil {
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return nil, nil, err
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}
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return aead, aeadNonce, nil
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}
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