move dependencies to vendor

vendor/github.com/docker/libtrust/hash.go

@@ -0,0 +1,56 @@
+package libtrust
+
+import (
+	"crypto"
+	_ "crypto/sha256" // Registrer SHA224 and SHA256
+	_ "crypto/sha512" // Registrer SHA384 and SHA512
+	"fmt"
+)
+
+type signatureAlgorithm struct {
+	algHeaderParam string
+	hashID         crypto.Hash
+}
+
+func (h *signatureAlgorithm) HeaderParam() string {
+	return h.algHeaderParam
+}
+
+func (h *signatureAlgorithm) HashID() crypto.Hash {
+	return h.hashID
+}
+
+var (
+	rs256 = &signatureAlgorithm{"RS256", crypto.SHA256}
+	rs384 = &signatureAlgorithm{"RS384", crypto.SHA384}
+	rs512 = &signatureAlgorithm{"RS512", crypto.SHA512}
+	es256 = &signatureAlgorithm{"ES256", crypto.SHA256}
+	es384 = &signatureAlgorithm{"ES384", crypto.SHA384}
+	es512 = &signatureAlgorithm{"ES512", crypto.SHA512}
+)
+
+func rsaSignatureAlgorithmByName(alg string) (*signatureAlgorithm, error) {
+	switch {
+	case alg == "RS256":
+		return rs256, nil
+	case alg == "RS384":
+		return rs384, nil
+	case alg == "RS512":
+		return rs512, nil
+	default:
+		return nil, fmt.Errorf("RSA Digital Signature Algorithm %q not supported", alg)
+	}
+}
+
+func rsaPKCS1v15SignatureAlgorithmForHashID(hashID crypto.Hash) *signatureAlgorithm {
+	switch {
+	case hashID == crypto.SHA512:
+		return rs512
+	case hashID == crypto.SHA384:
+		return rs384
+	case hashID == crypto.SHA256:
+		fallthrough
+	default:
+		return rs256
+	}
+}