// ParsePEMPrivateKey returns a data.PrivateKey from a PEM encoded private key. It
// only supports RSA (PKCS#1) and attempts to decrypt using the passphrase, if encrypted.
func ParsePEMPrivateKey(pemBytes []byte, passphrase string) (*data.PrivateKey, error) {
	block, _ := pem.Decode(pemBytes)
	if block == nil {
		return nil, errors.New("no valid private key found")
	}

	switch block.Type {
	case "RSA PRIVATE KEY":
		var privKeyBytes []byte
		var err error

		if x509.IsEncryptedPEMBlock(block) {
			privKeyBytes, err = x509.DecryptPEMBlock(block, []byte(passphrase))
			if err != nil {
				return nil, errors.New("could not decrypt private key")
			}
		} else {
			privKeyBytes = block.Bytes
		}

		rsaPrivKey, err := x509.ParsePKCS1PrivateKey(privKeyBytes)
		if err != nil {
			return nil, fmt.Errorf("could not parse DER encoded key: %v", err)
		}

		tufRSAPrivateKey, err := RSAToPrivateKey(rsaPrivKey, data.RSAKey)
		if err != nil {
			return nil, fmt.Errorf("could not convert rsa.PrivateKey to data.PrivateKey: %v", err)
		}

		return tufRSAPrivateKey, nil
	case "EC PRIVATE KEY":
		var privKeyBytes []byte
		var err error

		if x509.IsEncryptedPEMBlock(block) {
			privKeyBytes, err = x509.DecryptPEMBlock(block, []byte(passphrase))
			if err != nil {
				return nil, errors.New("could not decrypt private key")
			}
		} else {
			privKeyBytes = block.Bytes
		}

		ecdsaPrivKey, err := x509.ParseECPrivateKey(privKeyBytes)
		if err != nil {
			return nil, fmt.Errorf("could not parse DER encoded private key: %v", err)
		}

		tufECDSAPrivateKey, err := ECDSAToPrivateKey(ecdsaPrivKey, data.ECDSAKey)
		if err != nil {
			return nil, fmt.Errorf("could not convert ecdsa.PrivateKey to data.PrivateKey: %v", err)
		}

		return tufECDSAPrivateKey, nil

	default:
		return nil, fmt.Errorf("unsupported key type %q", block.Type)
	}
}

// Read a PEM file and ask for a password to decrypt it if needed
func ReadPEMData(pemFile string, pemPass []byte) ([]byte, error) {
	pemData, err := ioutil.ReadFile(pemFile)
	if err != nil {
		return pemData, err
	}

	// We should really just get the pem.Block back here, if there's other
	// junk on the end, warn about it.
	pemBlock, rest := pem.Decode(pemData)
	if len(rest) > 0 {
		log.Warning("Didn't parse all of", pemFile)
	}

	if x509.IsEncryptedPEMBlock(pemBlock) {
		// Decrypt and get the ASN.1 DER bytes here
		pemData, err = x509.DecryptPEMBlock(pemBlock, pemPass)
		if err != nil {
			return pemData, err
		} else {
			log.Info("Decrypted", pemFile, "successfully")
		}
		// Shove the decrypted DER bytes into a new pem Block with blank headers
		var newBlock pem.Block
		newBlock.Type = pemBlock.Type
		newBlock.Bytes = pemData
		// This is now like reading in an uncrypted key from a file and stuffing it
		// into a byte stream
		pemData = pem.EncodeToMemory(&newBlock)
	}
	return pemData, nil
}

// PEMtoPublicKey unmarshals a pem to public key
func PEMtoPublicKey(raw []byte, pwd []byte) (interface{}, error) {
	if len(raw) == 0 {
		return nil, errors.New("Invalid PEM. It must be diffrent from nil.")
	}
	block, _ := pem.Decode(raw)
	if block == nil {
		return nil, fmt.Errorf("Failed decoding. Block must be different from nil. [% x]", raw)
	}

	// TODO: derive from header the type of the key
	if x509.IsEncryptedPEMBlock(block) {
		if len(pwd) == 0 {
			return nil, errors.New("Encrypted Key. Password must be different from nil")
		}

		decrypted, err := x509.DecryptPEMBlock(block, pwd)
		if err != nil {
			return nil, fmt.Errorf("Failed PEM decryption. [%s]", err)
		}

		key, err := DERToPublicKey(decrypted)
		if err != nil {
			return nil, err
		}
		return key, err
	}

	cert, err := DERToPublicKey(block.Bytes)
	if err != nil {
		return nil, err
	}
	return cert, err
}

// readKey returns the decrypted key pem bytes, and enforces the KEK if applicable
// (writes it back with the correct encryption if it is not correctly encrypted)
func (k *KeyReadWriter) readKey() (*pem.Block, error) {
	keyBlock, err := k.readKeyblock()
	if err != nil {
		return nil, err
	}

	if !x509.IsEncryptedPEMBlock(keyBlock) {
		return keyBlock, nil
	}

	// If it's encrypted, we can't read without a passphrase (we're assuming
	// empty passphrases iare invalid)
	if k.kekData.KEK == nil {
		return nil, ErrInvalidKEK{Wrapped: x509.IncorrectPasswordError}
	}

	derBytes, err := x509.DecryptPEMBlock(keyBlock, k.kekData.KEK)
	if err != nil {
		return nil, ErrInvalidKEK{Wrapped: err}
	}
	// remove encryption PEM headers
	headers := make(map[string]string)
	mergePEMHeaders(headers, keyBlock.Headers)

	return &pem.Block{
		Type:    keyBlock.Type, // the key type doesn't change
		Bytes:   derBytes,
		Headers: headers,
	}, nil
}

func addKeyAuth(auths []ssh.AuthMethod, keypath string) []ssh.AuthMethod {
	if len(keypath) == 0 {
		return auths
	}

	keypath = expandPath(keypath)

	// read the file
	pemBytes, err := ioutil.ReadFile(keypath)
	if err != nil {
		log.Print(err)
		os.Exit(1)
	}

	// get first pem block
	block, _ := pem.Decode(pemBytes)
	if block == nil {
		log.Printf("no key found in %s", keypath)
		return auths
	}

	// handle plain and encrypted keyfiles
	if x509.IsEncryptedPEMBlock(block) {
		log.Printf("warning: ignoring encrypted key '%s'", keypath)
		return auths
	} else {
		signer, err := ssh.ParsePrivateKey(pemBytes)
		if err != nil {
			log.Print(err)
			return auths
		}
		return append(auths, ssh.PublicKeys(signer))
	}
}

// PEMtoPublicKey unmarshals a pem to public key
func PEMtoPublicKey(raw []byte, pwd []byte) (interface{}, error) {
	if len(raw) == 0 {
		return nil, utils.ErrNilArgument
	}
	block, _ := pem.Decode(raw)
	if block == nil {
		return nil, fmt.Errorf("Failed decoding [% x]", raw)
	}

	// TODO: derive from header the type of the key
	if x509.IsEncryptedPEMBlock(block) {
		if len(pwd) == 0 {
			return nil, errors.New("Encrypted Key. Need a password!!!")
		}

		decrypted, err := x509.DecryptPEMBlock(block, pwd)
		if err != nil {
			return nil, errors.New("Failed decryption!!!")
		}

		key, err := DERToPublicKey(decrypted)
		if err != nil {
			return nil, err
		}
		return key, err
	}

	cert, err := DERToPublicKey(block.Bytes)
	if err != nil {
		return nil, err
	}
	return cert, err
}

// ReadPrivateKey attempts to read your private key and possibly decrypt it if it
// requires a passphrase.
// This function will prompt for a passphrase on STDIN if the environment variable (`IDENTITY_PASSPHRASE`),
// is not set.
func ReadPrivateKey(path string) ([]byte, error) {
	privateKey, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("failed to load identity: %v", err)
	}

	block, rest := pem.Decode(privateKey)
	if len(rest) > 0 {
		return nil, fmt.Errorf("extra data when decoding private key")
	}
	if !x509.IsEncryptedPEMBlock(block) {
		return privateKey, nil
	}

	passphrase := os.Getenv("IDENTITY_PASSPHRASE")
	if passphrase == "" {
		passphrase, err = gopass.GetPass("Enter passphrase: ")
		if err != nil {
			return nil, fmt.Errorf("couldn't read passphrase: %v", err)
		}
	}
	der, err := x509.DecryptPEMBlock(block, []byte(passphrase))
	if err != nil {
		return nil, fmt.Errorf("decrypt failed: %v", err)
	}

	privateKey = pem.EncodeToMemory(&pem.Block{
		Type:  block.Type,
		Bytes: der,
	})

	return privateKey, nil
}

// PEMtoPublicKey unmarshals a pem to public key
func PEMtoPublicKey(raw []byte, pwd []byte) (interface{}, error) {
	block, _ := pem.Decode(raw)
	// TODO: derive from header the type of the key

	if x509.IsEncryptedPEMBlock(block) {
		if pwd == nil {
			return nil, errors.New("Encrypted Key. Need a password!!!")
		}

		decrypted, err := x509.DecryptPEMBlock(block, pwd)
		if err != nil {
			return nil, errors.New("Failed decryption!!!")
		}

		key, err := DERToPublicKey(decrypted)
		if err != nil {
			return nil, err
		}
		return key, err
	}

	cert, err := DERToPublicKey(block.Bytes)
	if err != nil {
		return nil, err
	}
	return cert, err
}

// SSHConfigPubKeyFile is a convience function that takes a username, private key
// and passphrase and returns a new ssh.ClientConfig setup to pass credentials
// to DialSSH
func SSHConfigPubKeyFile(user string, file string, passphrase string) (*ssh.ClientConfig, error) {
	buf, err := ioutil.ReadFile(file)
	if err != nil {
		return nil, err
	}
	block, rest := pem.Decode(buf)
	if len(rest) > 0 {
		return nil, fmt.Errorf("pem: unable to decode file %s", file)
	}

	if x509.IsEncryptedPEMBlock(block) {
		b := block.Bytes
		b, err = x509.DecryptPEMBlock(block, []byte(passphrase))
		if err != nil {
			return nil, err
		}
		buf = pem.EncodeToMemory(&pem.Block{
			Type:  block.Type,
			Bytes: b,
		})
	}

	key, err := ssh.ParsePrivateKey(buf)
	if err != nil {
		return nil, err
	}
	return &ssh.ClientConfig{
		User: user,
		Auth: []ssh.AuthMethod{
			ssh.PublicKeys(key),
		},
	}, nil

}

// processPrivateKeyFile takes a private key file and an optional passphrase
// and decodes it to a byte slice.
func processPrivateKeyFile(privateKeyFile, passphrase string) ([]byte, error) {
	rawPrivateKeyBytes, err := ioutil.ReadFile(privateKeyFile)
	if err != nil {
		return nil, fmt.Errorf("Failed loading private key file: %s", err)
	}

	PEMBlock, _ := pem.Decode(rawPrivateKeyBytes)
	if PEMBlock == nil {
		return nil, fmt.Errorf(
			"%s does not contain a vaild private key", privateKeyFile)
	}

	if x509.IsEncryptedPEMBlock(PEMBlock) {
		if passphrase == "" {
			return nil, errors.New("a passphrase must be specified when using an encrypted private key")
		}

		decryptedPrivateKeyBytes, err := x509.DecryptPEMBlock(PEMBlock, []byte(passphrase))
		if err != nil {
			return nil, fmt.Errorf("Failed decrypting private key: %s", err)
		}

		b := &pem.Block{
			Type:  "RSA PRIVATE KEY",
			Bytes: decryptedPrivateKeyBytes,
		}
		return pem.EncodeToMemory(b), nil
	}

	return rawPrivateKeyBytes, nil
}

func server(config Config) {

	// open receive port
	readSocket := openUDPSocket(`r`, net.UDPAddr{
		IP:   net.IPv4(0, 0, 0, 0),
		Port: config.Port,
	})
	fmt.Printf("Listening on UDP port %d...\n", config.Port)
	defer readSocket.Close()

	// main loop
	for {
		data := make([]byte, UDP_MSG_SIZE)
		size, clientAddr, err := readSocket.ReadFromUDP(data)
		if err != nil {
			fmt.Println("Error reading from receive port: ", err)
		}
		clientMsg := data[0:size]
		if string(clientMsg) == KEY_REQUEST_TEXT {
			fmt.Printf("Received key request from %s, sending key.\n",
				clientAddr.IP)
			// reply to the client on the same port
			writeSocket := openUDPSocket(`w`, net.UDPAddr{
				IP:   clientAddr.IP,
				Port: clientAddr.Port + 1,
			})
			var keyData []byte
			keyData = []byte(os.Getenv(KEY_DATA_ENV_VAR))
			if len(keyData) == 0 {
				keyData, err = ioutil.ReadFile(config.KeyPath)
				if err != nil {
					fmt.Printf("ERROR reading keyfile %s: %s!\n", config.KeyPath, err)
				}
			}
			pemBlock, _ := pem.Decode(keyData)
			if pemBlock != nil {
				if x509.IsEncryptedPEMBlock(pemBlock) {
					fmt.Println("Decrypting private key with passphrase...")
					decoded, err := x509.DecryptPEMBlock(pemBlock, []byte(config.Pwd))
					if err == nil {
						header := `PRIVATE KEY` // default key type in header
						matcher := regexp.MustCompile("-----BEGIN (.*)-----")
						if matches := matcher.FindSubmatch(keyData); len(matches) > 1 {
							header = string(matches[1])
						}
						keyData = pem.EncodeToMemory(
							&pem.Block{Type: header, Bytes: decoded})
					} else {
						fmt.Printf("Error decrypting PEM-encoded secret: %s\n", err)
					}
				}
			}
			_, err = writeSocket.Write(keyData)
			if err != nil {
				fmt.Printf("ERROR writing data to socket:%s!\n", err)
			}
			writeSocket.Close()
		}
	}
}

func readPEMFile(path, passphrase string) ([]byte, error) {
	pass := []byte(passphrase)
	var blocks []*pem.Block

	content, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, err
	}

	for len(content) > 0 {
		var block *pem.Block

		block, content = pem.Decode(content)
		if block == nil {
			if len(blocks) == 0 {
				return nil, errors.New("no pem file")
			}
			break
		}

		if x509.IsEncryptedPEMBlock(block) {
			var buffer []byte
			var err error
			if len(pass) == 0 {
				err = errors.New("No passphrase available")
			} else {
				// Note, decrypting pem might succeed even with wrong password, but
				// only noise will be stored in buffer in this case.
				buffer, err = x509.DecryptPEMBlock(block, pass)
			}

			if err != nil {
				logp.Err("Dropping encrypted pem '%v' block read from %v. %v",
					block.Type, path, err)
				continue
			}

			// DEK-Info contains encryption info. Remove header to mark block as
			// unencrypted.
			delete(block.Headers, "DEK-Info")
			block.Bytes = buffer
		}
		blocks = append(blocks, block)
	}

	if len(blocks) == 0 {
		return nil, errors.New("no PEM blocks")
	}

	// re-encode available, decrypted blocks
	buffer := bytes.NewBuffer(nil)
	for _, block := range blocks {
		err := pem.Encode(buffer, block)
		if err != nil {
			return nil, err
		}
	}
	return buffer.Bytes(), nil
}

// ParsePEMPrivateKey returns a data.PrivateKey from a PEM encoded private key. It
// only supports RSA (PKCS#1) and attempts to decrypt using the passphrase, if encrypted.
func ParsePEMPrivateKey(pemBytes []byte, passphrase string) (data.PrivateKey, error) {
	block, _ := pem.Decode(pemBytes)
	if block == nil {
		return nil, errors.New("no valid private key found")
	}

	var privKeyBytes []byte
	var err error
	if x509.IsEncryptedPEMBlock(block) {
		privKeyBytes, err = x509.DecryptPEMBlock(block, []byte(passphrase))
		if err != nil {
			return nil, errors.New("could not decrypt private key")
		}
	} else {
		privKeyBytes = block.Bytes
	}

	switch block.Type {
	case "RSA PRIVATE KEY":
		rsaPrivKey, err := x509.ParsePKCS1PrivateKey(privKeyBytes)
		if err != nil {
			return nil, fmt.Errorf("could not parse DER encoded key: %v", err)
		}

		tufRSAPrivateKey, err := RSAToPrivateKey(rsaPrivKey)
		if err != nil {
			return nil, fmt.Errorf("could not convert rsa.PrivateKey to data.PrivateKey: %v", err)
		}

		return tufRSAPrivateKey, nil
	case "EC PRIVATE KEY":
		ecdsaPrivKey, err := x509.ParseECPrivateKey(privKeyBytes)
		if err != nil {
			return nil, fmt.Errorf("could not parse DER encoded private key: %v", err)
		}

		tufECDSAPrivateKey, err := ECDSAToPrivateKey(ecdsaPrivKey)
		if err != nil {
			return nil, fmt.Errorf("could not convert ecdsa.PrivateKey to data.PrivateKey: %v", err)
		}

		return tufECDSAPrivateKey, nil
	case "ED25519 PRIVATE KEY":
		// We serialize ED25519 keys by concatenating the private key
		// to the public key and encoding with PEM. See the
		// ED25519ToPrivateKey function.
		tufECDSAPrivateKey, err := ED25519ToPrivateKey(privKeyBytes)
		if err != nil {
			return nil, fmt.Errorf("could not convert ecdsa.PrivateKey to data.PrivateKey: %v", err)
		}

		return tufECDSAPrivateKey, nil

	default:
		return nil, fmt.Errorf("unsupported key type %q", block.Type)
	}
}

func unencryptPrivateKey(block *pem.Block, password string) (crypto.PrivateKey, error) {
	if x509.IsEncryptedPEMBlock(block) {
		bytes, err := x509.DecryptPEMBlock(block, []byte(password))
		if err != nil {
			return nil, ErrFailedToDecryptKey
		}
		return parsePrivateKey(bytes)
	}
	return parsePrivateKey(block.Bytes)
}

// Determine if PEM file is encrypted
func IsEncryptedPEM(pemFile string) bool {
	pemData, err := ioutil.ReadFile(pemFile)
	if err != nil {
		return false
	}
	pemBlock, _ := pem.Decode(pemData)
	if len(pemBlock.Bytes) == 0 {
		return false
	}
	return x509.IsEncryptedPEMBlock(pemBlock)
}

func loadPrivateKey(path string) (ssh.AuthMethod, error) {
	// Read file
	keyData, err := ioutil.ReadFile(path)
	if err != nil {
		log.Printf("error: could not read key file '%s': %s", path, err)
		return nil, err
	}

	// Get first PEM block
	block, _ := pem.Decode(keyData)
	if err != nil {
		log.Printf("error: no key found in file '%s': %s", path, err)
		return nil, err
	}

	// If it's encrypted...
	var (
		signer    ssh.Signer
		signerErr error
	)

	if x509.IsEncryptedPEMBlock(block) {
		// Get the passphrase
		prompt := fmt.Sprintf("Enter passphrase for key '%s': ", path)
		pass, err := speakeasy.Ask(prompt)
		if err != nil {
			log.Printf("error: error getting passphrase: %s", err)
			return nil, err
		}

		block.Bytes, err = x509.DecryptPEMBlock(block, []byte(pass))
		if err != nil {
			log.Printf("error: error decrypting key: %s", err)
			return nil, err
		}

		key, err := ParsePEMBlock(block)
		if err != nil {
			log.Printf("error: could not parse PEM block: %s", err)
			return nil, err
		}

		signer, signerErr = ssh.NewSignerFromKey(key)
	} else {
		signer, signerErr = ssh.ParsePrivateKey(keyData)
	}

	if signerErr != nil {
		log.Printf("error: error parsing private key '%s': %s", path, signerErr)
		return nil, signerErr
	}

	return ssh.PublicKeys(signer), nil
}

// checkRootKeyIsEncrypted makes sure the root key is encrypted. We have
// internal assumptions that depend on this.
func checkRootKeyIsEncrypted(pemBytes []byte) error {
	block, _ := pem.Decode(pemBytes)
	if block == nil {
		return ErrNoValidPrivateKey
	}

	if !x509.IsEncryptedPEMBlock(block) {
		return ErrRootKeyNotEncrypted
	}

	return nil
}

func (a *SAuth) signInWithKey() (*signinResponse, error) {
	body := struct {
		PublicKey string `json:"publicKey"`
		Signature string `json:"signature"`
	}{}

	bytes, err := ioutil.ReadFile(a.Settings.PrivateKeyPath)
	if err != nil {
		return nil, err
	}
	block, _ := pem.Decode(bytes)
	if block == nil {
		return nil, errors.New("Private key is not PEM-encoded")
	}
	bytes = block.Bytes
	if x509.IsEncryptedPEMBlock(block) {
		passphrase := a.Prompts.KeyPassphrase(a.Settings.PrivateKeyPath)
		bytes, err = x509.DecryptPEMBlock(block, []byte(passphrase))
		if err != nil {
			return nil, err
		}
	}
	privateKey, err := x509.ParsePKCS1PrivateKey(bytes)
	if err != nil {
		return nil, err
	}
	publicKey, err := ioutil.ReadFile(a.Settings.PrivateKeyPath + ".pub")
	if err != nil {
		return nil, err
	}
	body.PublicKey = string(publicKey)

	headers := httpclient.GetHeaders(a.Settings.SessionToken, a.Settings.Version, a.Settings.Pod, a.Settings.UsersID)
	message := fmt.Sprintf("%s&%s", headers["X-Request-Nonce"][0], headers["X-Request-Timestamp"][0])
	hashedMessage := sha256.Sum256([]byte(message))
	signature, err := privateKey.Sign(rand.Reader, hashedMessage[:], crypto.SHA256)
	if err != nil {
		return nil, err
	}
	body.Signature = base64.StdEncoding.EncodeToString(signature)

	b, err := json.Marshal(body)
	if err != nil {
		return nil, err
	}
	resp, statusCode, err := httpclient.Post(b, fmt.Sprintf("%s%s/auth/signin/key", a.Settings.AuthHost, a.Settings.AuthHostVersion), headers)
	if err != nil {
		return nil, err
	}
	signinResp := &signinResponse{}
	return signinResp, httpclient.ConvertResp(resp, statusCode, signinResp)
}

func parseKey(block *pem.Block, passphrase []byte) (*rsa.PrivateKey, error) {
	var blockBytes []byte
	if x509.IsEncryptedPEMBlock(block) {
		b, err := x509.DecryptPEMBlock(block, passphrase)
		if err != nil {
			return nil, err
		}
		blockBytes = b
	} else {
		blockBytes = block.Bytes
	}
	return x509.ParsePKCS1PrivateKey(blockBytes)
}

func addKeyAuth(auths []ssh.AuthMethod, keypath string) []ssh.AuthMethod {
	if len(keypath) == 0 {
		return auths
	}

	// read the file
	pemBytes, err := ioutil.ReadFile(keypath)
	if err != nil {
		log.Print(err)
		os.Exit(1)
	}

	// get first pem block
	block, _ := pem.Decode(pemBytes)
	if block == nil {
		log.Printf("no key found in %s", keypath)
		return auths
	}

	// handle plain and encrypted keyfiles
	if x509.IsEncryptedPEMBlock(block) {
		prompt := fmt.Sprintf("Enter passphrase for key '%s': ", keypath)
		pass, err := getpass(prompt)
		if err != nil {
			return auths
		}
		block.Bytes, err = x509.DecryptPEMBlock(block, []byte(pass))
		if err != nil {
			log.Print(err)
			return auths
		}
		key, err := ParsePemBlock(block)
		if err != nil {
			log.Print(err)
			return auths
		}
		signer, err := ssh.NewSignerFromKey(key)
		if err != nil {
			log.Print(err)
			return auths
		}
		return append(auths, ssh.PublicKeys(signer))
	} else {
		signer, err := ssh.ParsePrivateKey(pemBytes)
		if err != nil {
			log.Print(err)
			return auths
		}
		return append(auths, ssh.PublicKeys(signer))
	}
}