internal/cryputil: combines aead and cryptutil packages.

- Refactored encrypt / decrypt methods to use aead's NonceSize() interface method.
- Add explicit GenerateKey function.
- Remove mutex on XChaCha20.

internal/cryptutil/encrypt.go

@@ -0,0 +1,175 @@
+package cryptutil // import "github.com/pomerium/pomerium/internal/cryptutil"
+
+import (
+	"bytes"
+	"compress/gzip"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/chacha20poly1305"
+)
+
+// GenerateKey generates a random 32-byte key.
+// Panics if source of randomness fails.
+func GenerateKey() []byte {
+	key := make([]byte, 32)
+	if _, err := rand.Read(key); err != nil {
+		panic(err)
+	}
+	return key
+}
+
+// Cipher provides methods to encrypt and decrypt values.
+type Cipher interface {
+	Encrypt([]byte) ([]byte, error)
+	Decrypt([]byte) ([]byte, error)
+	Marshal(interface{}) (string, error)
+	Unmarshal(string, interface{}) error
+}
+
+// XChaCha20Cipher provides methods to encrypt and decrypt values.
+// Using an AEAD is a cipher providing authenticated encryption with associated data.
+// For a description of the methodology, see https://en.wikipedia.org/wiki/Authenticated_encryption
+type XChaCha20Cipher struct {
+	aead cipher.AEAD
+}
+
+// NewCipher returns a new XChacha20poly1305 cipher.
+func NewCipher(secret []byte) (*XChaCha20Cipher, error) {
+	aead, err := chacha20poly1305.NewX(secret)
+	if err != nil {
+		return nil, err
+	}
+	return &XChaCha20Cipher{
+		aead: aead,
+	}, nil
+}
+
+// GenerateNonce generates a random nonce.
+// Panics if source of randomness fails.
+func (c *XChaCha20Cipher) GenerateNonce() []byte {
+	nonce := make([]byte, c.aead.NonceSize())
+	if _, err := rand.Read(nonce); err != nil {
+		panic(err)
+	}
+	return nonce
+}
+
+// Encrypt a value using XChaCha20-Poly1305
+func (c *XChaCha20Cipher) Encrypt(plaintext []byte) (joined []byte, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("internal/aead: error encrypting bytes: %v", r)
+		}
+	}()
+	nonce := c.GenerateNonce()
+
+	ciphertext := c.aead.Seal(nil, nonce, plaintext, nil)
+
+	// we return the nonce as part of the returned value
+	joined = append(ciphertext[:], nonce[:]...)
+	return joined, nil
+}
+
+// Decrypt a value using XChaCha20-Poly1305
+func (c *XChaCha20Cipher) Decrypt(joined []byte) ([]byte, error) {
+	if len(joined) <= c.aead.NonceSize() {
+		return nil, fmt.Errorf("internal/aead: invalid input size: %d", len(joined))
+	}
+	// grab out the nonce
+	pivot := len(joined) - c.aead.NonceSize()
+	ciphertext := joined[:pivot]
+	nonce := joined[pivot:]
+
+	plaintext, err := c.aead.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	return plaintext, nil
+}
+
+// Marshal marshals the interface state as JSON, encrypts the JSON using the cipher
+// and base64 encodes the binary value as a string and returns the result
+func (c *XChaCha20Cipher) Marshal(s interface{}) (string, error) {
+	// encode json value
+	plaintext, err := json.Marshal(s)
+	if err != nil {
+		return "", err
+	}
+	// compress the plaintext bytes
+	compressed, err := compress(plaintext)
+	if err != nil {
+		return "", err
+	}
+	// encrypt the compressed JSON bytes
+	ciphertext, err := c.Encrypt(compressed)
+	if err != nil {
+		return "", err
+	}
+	// base64-encode the result
+	encoded := base64.RawURLEncoding.EncodeToString(ciphertext)
+	return encoded, nil
+}
+
+// Unmarshal takes the marshaled string, base64-decodes into a byte slice, decrypts the
+// byte slice the passed cipher, and unmarshals the resulting JSON into the struct pointer passed
+func (c *XChaCha20Cipher) Unmarshal(value string, s interface{}) error {
+	// convert base64 string value to bytes
+	ciphertext, err := base64.RawURLEncoding.DecodeString(value)
+	if err != nil {
+		return err
+	}
+	// decrypt the bytes
+	compressed, err := c.Decrypt(ciphertext)
+	if err != nil {
+		return err
+	}
+	// decompress the unencrypted bytes
+	plaintext, err := decompress(compressed)
+	if err != nil {
+		return err
+	}
+	// unmarshal the unencrypted bytes
+	err = json.Unmarshal(plaintext, s)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func compress(data []byte) ([]byte, error) {
+	var buf bytes.Buffer
+	writer, err := gzip.NewWriterLevel(&buf, gzip.DefaultCompression)
+	if err != nil {
+		return nil, fmt.Errorf("internal/aead: failed to create a gzip writer: %q", err)
+	}
+	if writer == nil {
+		return nil, fmt.Errorf("internal/aead: failed to create a gzip writer")
+	}
+	if _, err = writer.Write(data); err != nil {
+		return nil, fmt.Errorf("internal/aead: failed to compress data with err: %q", err)
+	}
+	if err = writer.Close(); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}
+
+func decompress(data []byte) ([]byte, error) {
+	reader, err := gzip.NewReader(bytes.NewReader(data))
+	if err != nil {
+		return nil, fmt.Errorf("internal/aead: failed to create a gzip reader: %q", err)
+	}
+	defer reader.Close()
+	var buf bytes.Buffer
+	if _, err = io.Copy(&buf, reader); err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}