code exchange fixes

pkg/oidc/token.go

@@ -1,14 +1,10 @@
 package oidc
 
 import (
-	"crypto/sha256"
-	"crypto/sha512"
-	"encoding/base64"
 	"encoding/json"
-	"fmt"
-	"hash"
 	"time"
 
+	"github.com/caos/oidc/pkg/utils"
 	"golang.org/x/oauth2"
 	"gopkg.in/square/go-jose.v2"
 )
@@ -94,25 +90,10 @@ type Tokens struct {
 }
 
 func ClaimHash(claim string, sigAlgorithm jose.SignatureAlgorithm) (string, error) {
-	hash, err := getHashAlgorithm(sigAlgorithm)
+	hash, err := utils.GetHashAlgorithm(sigAlgorithm)
 	if err != nil {
 		return "", err
 	}
 
-	hash.Write([]byte(claim)) // hash documents that Write will never return an error
-	sum := hash.Sum(nil)[:hash.Size()/2]
-	return base64.RawURLEncoding.EncodeToString(sum), nil
-}
-
-func getHashAlgorithm(sigAlgorithm jose.SignatureAlgorithm) (hash.Hash, error) {
-	switch sigAlgorithm {
-	case jose.RS256, jose.ES256, jose.PS256:
-		return sha256.New(), nil
-	case jose.RS384, jose.ES384, jose.PS384:
-		return sha512.New384(), nil
-	case jose.RS512, jose.ES512, jose.PS512:
-		return sha512.New(), nil
-	default:
-		return nil, fmt.Errorf("oidc: unsupported signing algorithm %q", sigAlgorithm)
-	}
+	return utils.HashString(hash, claim), nil
 }