cmd/stdiscosrv: New discovery server (fixes #4618)

This is a new revision of the discovery server. Relevant changes and
non-changes:

- Protocol towards clients is unchanged.

- Recommended large scale design is still to be deployed nehind nginx (I
  tested, and it's still a lot faster at terminating TLS).

- Database backend is leveldb again, only. It scales enough, is easy to
  setup, and we don't need any backend to take care of.

- Server supports replication. This is a simple TCP channel - protect it
  with a firewall when deploying over the internet. (We deploy this within
  the same datacenter, and with firewall.) Any incoming client announces
  are sent over the replication channel(s) to other peer discosrvs.
  Incoming replication changes are applied to the database as if they came
  from clients, but without the TLS/certificate overhead.

- Metrics are exposed using the prometheus library, when enabled.

- The database values and replication protocol is protobuf, because JSON
  was quite CPU intensive when I tried that and benchmarked it.

- The "Retry-After" value for failed lookups gets slowly increased from
  a default of 120 seconds, by 5 seconds for each failed lookup,
  independently by each discosrv. This lowers the query load over time for
  clients that are never seen. The Retry-After maxes out at 3600 after a
  couple of weeks of this increase. The number of failed lookups is
  stored in the database, now and then (avoiding making each lookup a
  database put).

All in all this means clients can be pointed towards a cluster using
just multiple A / AAAA records to gain both load sharing and redundancy
(if one is down, clients will talk to the remaining ones).

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4648

vendor/github.com/minio/minio-go/pkg/encrypt/cbc.go

@@ -0,0 +1,294 @@
+/*
+ * Minio Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package encrypt
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
+	"io"
+)
+
+// Crypt mode - encryption or decryption
+type cryptMode int
+
+const (
+	encryptMode cryptMode = iota
+	decryptMode
+)
+
+// CBCSecureMaterials encrypts/decrypts data using AES CBC algorithm
+type CBCSecureMaterials struct {
+
+	// Data stream to encrypt/decrypt
+	stream io.Reader
+
+	// Last internal error
+	err error
+
+	// End of file reached
+	eof bool
+
+	// Holds initial data
+	srcBuf *bytes.Buffer
+
+	// Holds transformed data (encrypted or decrypted)
+	dstBuf *bytes.Buffer
+
+	// Encryption algorithm
+	encryptionKey Key
+
+	// Key to encrypts/decrypts data
+	contentKey []byte
+
+	// Encrypted form of contentKey
+	cryptedKey []byte
+
+	// Initialization vector
+	iv []byte
+
+	// matDesc - currently unused
+	matDesc []byte
+
+	// Indicate if we are going to encrypt or decrypt
+	cryptMode cryptMode
+
+	// Helper that encrypts/decrypts data
+	blockMode cipher.BlockMode
+}
+
+// NewCBCSecureMaterials builds new CBC crypter module with
+// the specified encryption key (symmetric or asymmetric)
+func NewCBCSecureMaterials(key Key) (*CBCSecureMaterials, error) {
+	if key == nil {
+		return nil, errors.New("Unable to recognize empty encryption properties")
+	}
+	return &CBCSecureMaterials{
+		srcBuf:        bytes.NewBuffer([]byte{}),
+		dstBuf:        bytes.NewBuffer([]byte{}),
+		encryptionKey: key,
+		matDesc:       []byte("{}"),
+	}, nil
+
+}
+
+// Close implements closes the internal stream.
+func (s *CBCSecureMaterials) Close() error {
+	closer, ok := s.stream.(io.Closer)
+	if ok {
+		return closer.Close()
+	}
+	return nil
+}
+
+// SetupEncryptMode - tells CBC that we are going to encrypt data
+func (s *CBCSecureMaterials) SetupEncryptMode(stream io.Reader) error {
+	// Set mode to encrypt
+	s.cryptMode = encryptMode
+
+	// Set underlying reader
+	s.stream = stream
+
+	s.eof = false
+	s.srcBuf.Reset()
+	s.dstBuf.Reset()
+
+	var err error
+
+	// Generate random content key
+	s.contentKey = make([]byte, aes.BlockSize*2)
+	if _, err := rand.Read(s.contentKey); err != nil {
+		return err
+	}
+	// Encrypt content key
+	s.cryptedKey, err = s.encryptionKey.Encrypt(s.contentKey)
+	if err != nil {
+		return err
+	}
+	// Generate random IV
+	s.iv = make([]byte, aes.BlockSize)
+	if _, err = rand.Read(s.iv); err != nil {
+		return err
+	}
+	// New cipher
+	encryptContentBlock, err := aes.NewCipher(s.contentKey)
+	if err != nil {
+		return err
+	}
+
+	s.blockMode = cipher.NewCBCEncrypter(encryptContentBlock, s.iv)
+
+	return nil
+}
+
+// SetupDecryptMode - tells CBC that we are going to decrypt data
+func (s *CBCSecureMaterials) SetupDecryptMode(stream io.Reader, iv string, key string) error {
+	// Set mode to decrypt
+	s.cryptMode = decryptMode
+
+	// Set underlying reader
+	s.stream = stream
+
+	// Reset
+	s.eof = false
+	s.srcBuf.Reset()
+	s.dstBuf.Reset()
+
+	var err error
+
+	// Get IV
+	s.iv, err = base64.StdEncoding.DecodeString(iv)
+	if err != nil {
+		return err
+	}
+
+	// Get encrypted content key
+	s.cryptedKey, err = base64.StdEncoding.DecodeString(key)
+	if err != nil {
+		return err
+	}
+
+	// Decrypt content key
+	s.contentKey, err = s.encryptionKey.Decrypt(s.cryptedKey)
+	if err != nil {
+		return err
+	}
+
+	// New cipher
+	decryptContentBlock, err := aes.NewCipher(s.contentKey)
+	if err != nil {
+		return err
+	}
+
+	s.blockMode = cipher.NewCBCDecrypter(decryptContentBlock, s.iv)
+	return nil
+}
+
+// GetIV - return randomly generated IV (per S3 object), base64 encoded.
+func (s *CBCSecureMaterials) GetIV() string {
+	return base64.StdEncoding.EncodeToString(s.iv)
+}
+
+// GetKey - return content encrypting key (cek) in encrypted form, base64 encoded.
+func (s *CBCSecureMaterials) GetKey() string {
+	return base64.StdEncoding.EncodeToString(s.cryptedKey)
+}
+
+// GetDesc - user provided encryption material description in JSON (UTF8) format.
+func (s *CBCSecureMaterials) GetDesc() string {
+	return string(s.matDesc)
+}
+
+// Fill buf with encrypted/decrypted data
+func (s *CBCSecureMaterials) Read(buf []byte) (n int, err error) {
+	// Always fill buf from bufChunk at the end of this function
+	defer func() {
+		if s.err != nil {
+			n, err = 0, s.err
+		} else {
+			n, err = s.dstBuf.Read(buf)
+		}
+	}()
+
+	// Return
+	if s.eof {
+		return
+	}
+
+	// Fill dest buffer if its length is less than buf
+	for !s.eof && s.dstBuf.Len() < len(buf) {
+
+		srcPart := make([]byte, aes.BlockSize)
+		dstPart := make([]byte, aes.BlockSize)
+
+		// Fill src buffer
+		for s.srcBuf.Len() < aes.BlockSize*2 {
+			_, err = io.CopyN(s.srcBuf, s.stream, aes.BlockSize)
+			if err != nil {
+				break
+			}
+		}
+
+		// Quit immediately for errors other than io.EOF
+		if err != nil && err != io.EOF {
+			s.err = err
+			return
+		}
+
+		// Mark current encrypting/decrypting as finished
+		s.eof = (err == io.EOF)
+
+		if s.eof && s.cryptMode == encryptMode {
+			if srcPart, err = pkcs5Pad(s.srcBuf.Bytes(), aes.BlockSize); err != nil {
+				s.err = err
+				return
+			}
+		} else {
+			_, _ = s.srcBuf.Read(srcPart)
+		}
+
+		// Crypt srcPart content
+		for len(srcPart) > 0 {
+
+			// Crypt current part
+			s.blockMode.CryptBlocks(dstPart, srcPart[:aes.BlockSize])
+
+			// Unpad when this is the last part and we are decrypting
+			if s.eof && s.cryptMode == decryptMode {
+				dstPart, err = pkcs5Unpad(dstPart, aes.BlockSize)
+				if err != nil {
+					s.err = err
+					return
+				}
+			}
+
+			// Send crypted data to dstBuf
+			if _, wErr := s.dstBuf.Write(dstPart); wErr != nil {
+				s.err = wErr
+				return
+			}
+			// Move to the next part
+			srcPart = srcPart[aes.BlockSize:]
+		}
+	}
+	return
+}
+
+// Unpad a set of bytes following PKCS5 algorithm
+func pkcs5Unpad(buf []byte, blockSize int) ([]byte, error) {
+	len := len(buf)
+	if len == 0 {
+		return nil, errors.New("buffer is empty")
+	}
+	pad := int(buf[len-1])
+	if pad > len || pad > blockSize {
+		return nil, errors.New("invalid padding size")
+	}
+	return buf[:len-pad], nil
+}
+
+// Pad a set of bytes following PKCS5 algorithm
+func pkcs5Pad(buf []byte, blockSize int) ([]byte, error) {
+	len := len(buf)
+	pad := blockSize - (len % blockSize)
+	padText := bytes.Repeat([]byte{byte(pad)}, pad)
+	return append(buf, padText...), nil
+}

vendor/github.com/minio/minio-go/pkg/encrypt/interface.go

@@ -0,0 +1,54 @@
+/*
+ * Minio Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Package encrypt implements a generic interface to encrypt any stream of data.
+// currently this package implements two types of encryption
+// - Symmetric encryption using AES.
+// - Asymmetric encrytion using RSA.
+package encrypt
+
+import "io"
+
+// Materials - provides generic interface to encrypt any stream of data.
+type Materials interface {
+
+	// Closes the wrapped stream properly, initiated by the caller.
+	Close() error
+
+	// Returns encrypted/decrypted data, io.Reader compatible.
+	Read(b []byte) (int, error)
+
+	// Get randomly generated IV, base64 encoded.
+	GetIV() (iv string)
+
+	// Get content encrypting key (cek) in encrypted form, base64 encoded.
+	GetKey() (key string)
+
+	// Get user provided encryption material description in
+	// JSON (UTF8) format. This is not used, kept for future.
+	GetDesc() (desc string)
+
+	// Setup encrypt mode, further calls of Read() function
+	// will return the encrypted form of data streamed
+	// by the passed reader
+	SetupEncryptMode(stream io.Reader) error
+
+	// Setup decrypted mode, further calls of Read() function
+	// will return the decrypted form of data streamed
+	// by the passed reader
+	SetupDecryptMode(stream io.Reader, iv string, key string) error
+}

vendor/github.com/minio/minio-go/pkg/encrypt/keys.go

@@ -0,0 +1,166 @@
+/*
+ * Minio Go Library for Amazon S3 Compatible Cloud Storage
+ * Copyright 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package encrypt
+
+import (
+	"crypto/aes"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/x509"
+	"errors"
+)
+
+// Key - generic interface to encrypt/decrypt a key.
+// We use it to encrypt/decrypt content key which is the key
+// that encrypt/decrypt object data.
+type Key interface {
+	// Encrypt data using to the set encryption key
+	Encrypt([]byte) ([]byte, error)
+	// Decrypt data using to the set encryption key
+	Decrypt([]byte) ([]byte, error)
+}
+
+// SymmetricKey - encrypts data with a symmetric master key
+type SymmetricKey struct {
+	masterKey []byte
+}
+
+// Encrypt passed bytes
+func (s *SymmetricKey) Encrypt(plain []byte) ([]byte, error) {
+	// Initialize an AES encryptor using a master key
+	keyBlock, err := aes.NewCipher(s.masterKey)
+	if err != nil {
+		return []byte{}, err
+	}
+
+	// Pad the key before encryption
+	plain, _ = pkcs5Pad(plain, aes.BlockSize)
+
+	encKey := []byte{}
+	encPart := make([]byte, aes.BlockSize)
+
+	// Encrypt the passed key by block
+	for {
+		if len(plain) < aes.BlockSize {
+			break
+		}
+		// Encrypt the passed key
+		keyBlock.Encrypt(encPart, plain[:aes.BlockSize])
+		// Add the encrypted block to the total encrypted key
+		encKey = append(encKey, encPart...)
+		// Pass to the next plain block
+		plain = plain[aes.BlockSize:]
+	}
+	return encKey, nil
+}
+
+// Decrypt passed bytes
+func (s *SymmetricKey) Decrypt(cipher []byte) ([]byte, error) {
+	// Initialize AES decrypter
+	keyBlock, err := aes.NewCipher(s.masterKey)
+	if err != nil {
+		return nil, err
+	}
+
+	var plain []byte
+	plainPart := make([]byte, aes.BlockSize)
+
+	// Decrypt the encrypted data block by block
+	for {
+		if len(cipher) < aes.BlockSize {
+			break
+		}
+		keyBlock.Decrypt(plainPart, cipher[:aes.BlockSize])
+		// Add the decrypted block to the total result
+		plain = append(plain, plainPart...)
+		// Pass to the next cipher block
+		cipher = cipher[aes.BlockSize:]
+	}
+
+	// Unpad the resulted plain data
+	plain, err = pkcs5Unpad(plain, aes.BlockSize)
+	if err != nil {
+		return nil, err
+	}
+
+	return plain, nil
+}
+
+// NewSymmetricKey generates a new encrypt/decrypt crypto using
+// an AES master key password
+func NewSymmetricKey(b []byte) *SymmetricKey {
+	return &SymmetricKey{masterKey: b}
+}
+
+// AsymmetricKey - struct which encrypts/decrypts data
+// using RSA public/private certificates
+type AsymmetricKey struct {
+	publicKey  *rsa.PublicKey
+	privateKey *rsa.PrivateKey
+}
+
+// Encrypt data using public key
+func (a *AsymmetricKey) Encrypt(plain []byte) ([]byte, error) {
+	cipher, err := rsa.EncryptPKCS1v15(rand.Reader, a.publicKey, plain)
+	if err != nil {
+		return nil, err
+	}
+	return cipher, nil
+}
+
+// Decrypt data using public key
+func (a *AsymmetricKey) Decrypt(cipher []byte) ([]byte, error) {
+	cipher, err := rsa.DecryptPKCS1v15(rand.Reader, a.privateKey, cipher)
+	if err != nil {
+		return nil, err
+	}
+	return cipher, nil
+}
+
+// NewAsymmetricKey - generates a crypto module able to encrypt/decrypt
+// data using a pair for private and public key
+func NewAsymmetricKey(privData []byte, pubData []byte) (*AsymmetricKey, error) {
+	// Parse private key from passed data
+	priv, err := x509.ParsePKCS8PrivateKey(privData)
+	if err != nil {
+		return nil, err
+	}
+	privKey, ok := priv.(*rsa.PrivateKey)
+	if !ok {
+		return nil, errors.New("not a valid private key")
+	}
+
+	// Parse public key from passed data
+	pub, err := x509.ParsePKIXPublicKey(pubData)
+	if err != nil {
+		return nil, err
+	}
+
+	pubKey, ok := pub.(*rsa.PublicKey)
+	if !ok {
+		return nil, errors.New("not a valid public key")
+	}
+
+	// Associate the private key with the passed public key
+	privKey.PublicKey = *pubKey
+
+	return &AsymmetricKey{
+		publicKey:  pubKey,
+		privateKey: privKey,
+	}, nil
+}