vendor mint

vendor/github.com/bifurcation/mint/cookie-protector.go

@@ -0,0 +1,86 @@
+package mint
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"crypto/sha256"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/hkdf"
+)
+
+// CookieProtector is used to create and verify a cookie
+type CookieProtector interface {
+	// NewToken creates a new token
+	NewToken([]byte) ([]byte, error)
+	// DecodeToken decodes a token
+	DecodeToken([]byte) ([]byte, error)
+}
+
+const cookieSecretSize = 32
+const cookieNonceSize = 32
+
+// The DefaultCookieProtector is a simple implementation for the CookieProtector.
+type DefaultCookieProtector struct {
+	secret []byte
+}
+
+var _ CookieProtector = &DefaultCookieProtector{}
+
+// NewDefaultCookieProtector creates a source for source address tokens
+func NewDefaultCookieProtector() (CookieProtector, error) {
+	secret := make([]byte, cookieSecretSize)
+	if _, err := rand.Read(secret); err != nil {
+		return nil, err
+	}
+	return &DefaultCookieProtector{secret: secret}, nil
+}
+
+// NewToken encodes data into a new token.
+func (s *DefaultCookieProtector) NewToken(data []byte) ([]byte, error) {
+	nonce := make([]byte, cookieNonceSize)
+	if _, err := rand.Read(nonce); err != nil {
+		return nil, err
+	}
+	aead, aeadNonce, err := s.createAEAD(nonce)
+	if err != nil {
+		return nil, err
+	}
+	return append(nonce, aead.Seal(nil, aeadNonce, data, nil)...), nil
+}
+
+// DecodeToken decodes a token.
+func (s *DefaultCookieProtector) DecodeToken(p []byte) ([]byte, error) {
+	if len(p) < cookieNonceSize {
+		return nil, fmt.Errorf("Token too short: %d", len(p))
+	}
+	nonce := p[:cookieNonceSize]
+	aead, aeadNonce, err := s.createAEAD(nonce)
+	if err != nil {
+		return nil, err
+	}
+	return aead.Open(nil, aeadNonce, p[cookieNonceSize:], nil)
+}
+
+func (s *DefaultCookieProtector) createAEAD(nonce []byte) (cipher.AEAD, []byte, error) {
+	h := hkdf.New(sha256.New, s.secret, nonce, []byte("mint cookie source"))
+	key := make([]byte, 32) // use a 32 byte key, in order to select AES-256
+	if _, err := io.ReadFull(h, key); err != nil {
+		return nil, nil, err
+	}
+	aeadNonce := make([]byte, 12)
+	if _, err := io.ReadFull(h, aeadNonce); err != nil {
+		return nil, nil, err
+	}
+	c, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, nil, err
+	}
+	aead, err := cipher.NewGCM(c)
+	if err != nil {
+		return nil, nil, err
+	}
+	return aead, aeadNonce, nil
+}