switch to go vendoring

vendor/github.com/MicahParks/keyfunc/keyfunc.go

@@ -0,0 +1,41 @@
+package keyfunc
+
+import (
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/golang-jwt/jwt/v4"
+)
+
+var (
+	// ErrKID indicates that the JWT had an invalid kid.
+	ErrKID = errors.New("the JWT has an invalid kid")
+)
+
+// Keyfunc matches the signature of github.com/golang-jwt/jwt/v4's jwt.Keyfunc function.
+func (j *JWKS) Keyfunc(token *jwt.Token) (interface{}, error) {
+	kidInter, ok := token.Header["kid"]
+	if !ok {
+		return nil, fmt.Errorf("%w: could not find kid in JWT header", ErrKID)
+	}
+	kid, ok := kidInter.(string)
+	if !ok {
+		return nil, fmt.Errorf("%w: could not convert kid in JWT header to string", ErrKID)
+	}
+
+	return j.getKey(kid)
+}
+
+// base64urlTrailingPadding removes trailing padding before decoding a string from base64url. Some non-RFC compliant
+// JWKS contain padding at the end values for base64url encoded public keys.
+//
+// Trailing padding is required to be removed from base64url encoded keys.
+// RFC 7517 defines base64url the same as RFC 7515 Section 2:
+// https://datatracker.ietf.org/doc/html/rfc7517#section-1.1
+// https://datatracker.ietf.org/doc/html/rfc7515#section-2
+func base64urlTrailingPadding(s string) ([]byte, error) {
+	s = strings.TrimRight(s, "=")
+	return base64.RawURLEncoding.DecodeString(s)
+}