docker/cli · error

provided file %s is not a supported private key - to add a s

Error message

provided file %s is not a supported private key - to add a signer's public key use docker trust signer add

What it means

Error "provided file %s is not a supported private key - to add a signer's public key use docker trust signer add" thrown in docker/cli.

Source

Thrown at cmd/docker-trust/trust/key_load.go:96

		}
		if fileInfo.Mode()&nonOwnerReadWriteMask != 0 {
			return nil, fmt.Errorf("private key file %s must not be readable or writable by others", keyPath)
		}
	}

	from, err := os.OpenFile(keyPath, os.O_RDONLY, notary.PrivExecPerms)
	if err != nil {
		return nil, err
	}
	defer from.Close()

	return io.ReadAll(from)
}

func loadPrivKeyBytesToStore(privKeyBytes []byte, privKeyImporters []trustmanager.Importer, keyPath, keyName string, passRet notary.PassRetriever) error {
	var err error
	if _, _, err = tufutils.ExtractPrivateKeyAttributes(privKeyBytes); err != nil {
		return fmt.Errorf("provided file %s is not a supported private key - to add a signer's public key use docker trust signer add", keyPath)
	}
	if privKeyBytes, err = decodePrivKeyIfNecessary(privKeyBytes, passRet); err != nil {
		return fmt.Errorf("cannot load key from provided file %s: %w", keyPath, err)
	}
	// Make a reader, rewind the file pointer
	return trustmanager.ImportKeys(bytes.NewReader(privKeyBytes), privKeyImporters, keyName, "", passRet)
}

func decodePrivKeyIfNecessary(privPemBytes []byte, passRet notary.PassRetriever) ([]byte, error) {
	pemBlock, _ := pem.Decode(privPemBytes)
	_, containsDEKInfo := pemBlock.Headers["DEK-Info"]
	if containsDEKInfo || pemBlock.Type == "ENCRYPTED PRIVATE KEY" {
		// if we do not have enough information to properly import, try to decrypt the key
		if _, ok := pemBlock.Headers["path"]; !ok {
			privKey, _, err := trustmanager.GetPasswdDecryptBytes(passRet, privPemBytes, "", "encrypted")
			if err != nil {
				return []byte{}, errors.New("could not decrypt key")
			}

View on GitHub (pinned to e9452d6e78)

When it happens

Trigger: Thrown at cmd/docker-trust/trust/key_load.go:96 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of docker/cli@e9452d6e78 (2026-08-01). Data as JSON: /data/errors/ec25eef693280181.json. Report an issue: GitHub.