Initial QSfera import

Server/vendor/github.com/lestrrat-go/dsig/validation.go

@@ -0,0 +1,66 @@
+package dsig
+
+import (
+	"crypto/ecdsa"
+	"crypto/ed25519"
+	"crypto/rsa"
+)
+
+// isValidRSAKey validates that the provided key type is appropriate for RSA algorithms.
+// It returns false if the key is clearly incompatible (e.g., ECDSA or EdDSA keys).
+func isValidRSAKey(key any) bool {
+	switch key.(type) {
+	case
+		ecdsa.PrivateKey, *ecdsa.PrivateKey,
+		ed25519.PrivateKey:
+		// these are NOT ok for RSA algorithms
+		return false
+	}
+	return true
+}
+
+// isValidECDSAKey validates that the provided key type is appropriate for ECDSA algorithms.
+// It returns false if the key is clearly incompatible (e.g., RSA or EdDSA keys).
+func isValidECDSAKey(key any) bool {
+	switch key.(type) {
+	case
+		ed25519.PrivateKey,
+		rsa.PrivateKey, *rsa.PrivateKey:
+		// these are NOT ok for ECDSA algorithms
+		return false
+	}
+	return true
+}
+
+// isValidEDDSAKey validates that the provided key type is appropriate for EdDSA algorithms.
+// It returns false if the key is clearly incompatible (e.g., RSA or ECDSA keys).
+func isValidEDDSAKey(key any) bool {
+	switch key.(type) {
+	case
+		ecdsa.PrivateKey, *ecdsa.PrivateKey,
+		rsa.PrivateKey, *rsa.PrivateKey:
+		// these are NOT ok for EdDSA algorithms
+		return false
+	}
+	return true
+}
+
+// VerificationError represents an error that occurred during signature verification.
+type VerificationError struct {
+	message string
+}
+
+func (e *VerificationError) Error() string {
+	return e.message
+}
+
+// NewVerificationError creates a new verification error with the given message.
+func NewVerificationError(message string) error {
+	return &VerificationError{message: message}
+}
+
+// IsVerificationError checks if the given error is a verification error.
+func IsVerificationError(err error) bool {
+	_, ok := err.(*VerificationError)
+	return ok
+}