Improve error report when user passes a private key (#22726)

The error reported when a user passes a private ssh key as their ssh
public key is not very nice.

This PR improves this slightly.

Ref #22693

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: delvh <dev.lh@web.de>

models/asymkey/error.go

@@ -24,6 +24,9 @@ func (err ErrKeyUnableVerify) Error() string {
 	return fmt.Sprintf("Unable to verify key content [result: %s]", err.Result)
 }
 
+// ErrKeyIsPrivate is returned when the provided key is a private key not a public key
+var ErrKeyIsPrivate = util.NewSilentWrapErrorf(util.ErrInvalidArgument, "the provided key is a private key")
+
 // ErrKeyNotExist represents a "KeyNotExist" kind of error.
 type ErrKeyNotExist struct {
 	ID int64

models/asymkey/ssh_key_parse.go

@@ -96,6 +96,9 @@ func parseKeyString(content string) (string, error) {
 			if block == nil {
 				return "", fmt.Errorf("failed to parse PEM block containing the public key")
 			}
+			if strings.Contains(block.Type, "PRIVATE") {
+				return "", ErrKeyIsPrivate
+			}
 
 			pub, err := x509.ParsePKIXPublicKey(block.Bytes)
 			if err != nil {