Initial QSfera import

Server/vendor/github.com/lestrrat-go/jwx/v3/jwk/usage.go

@@ -0,0 +1,74 @@
+package jwk
+
+import (
+	"fmt"
+	"sync"
+	"sync/atomic"
+)
+
+var strictKeyUsage = atomic.Bool{}
+var keyUsageNames = map[string]struct{}{}
+var muKeyUsageName sync.RWMutex
+
+// RegisterKeyUsage registers a possible value that can be used for KeyUsageType.
+// Normally, key usage (or the "use" field in a JWK) is either "sig" or "enc",
+// but other values may be used.
+//
+// While this module only works with "sig" and "enc", it is possible that
+// systems choose to use other values. This function allows users to register
+// new values to be accepted as valid key usage types. Values are case sensitive.
+//
+// Furthermore, the check against registered values can be completely turned off
+// by setting the global option `jwk.WithStrictKeyUsage(false)`.
+func RegisterKeyUsage(v string) {
+	muKeyUsageName.Lock()
+	defer muKeyUsageName.Unlock()
+	keyUsageNames[v] = struct{}{}
+}
+
+func UnregisterKeyUsage(v string) {
+	muKeyUsageName.Lock()
+	defer muKeyUsageName.Unlock()
+	delete(keyUsageNames, v)
+}
+
+func init() {
+	strictKeyUsage.Store(true)
+	RegisterKeyUsage("sig")
+	RegisterKeyUsage("enc")
+}
+
+func isValidUsage(v string) bool {
+	// This function can return true if strictKeyUsage is false
+	if !strictKeyUsage.Load() {
+		return true
+	}
+
+	muKeyUsageName.RLock()
+	defer muKeyUsageName.RUnlock()
+	_, ok := keyUsageNames[v]
+	return ok
+}
+
+func (k KeyUsageType) String() string {
+	return string(k)
+}
+
+func (k *KeyUsageType) Accept(v any) error {
+	switch v := v.(type) {
+	case KeyUsageType:
+		if !isValidUsage(v.String()) {
+			return fmt.Errorf("invalid key usage type: %q", v)
+		}
+		*k = v
+		return nil
+	case string:
+		if !isValidUsage(v) {
+			return fmt.Errorf("invalid key usage type: %q", v)
+		}
+		*k = KeyUsageType(v)
+		return nil
+	}
+
+	return fmt.Errorf("invalid Go type for key usage type: %T", v)
+}