Swapped AES-CBC for GCM for all symmetric encryption; bolstered TLS configs

crypto/gcm.go

@@ -0,0 +1,60 @@
+package crypto
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"errors"
+	"fmt"
+	"io"
+)
+
+func GCMEncrypt(key []byte, plaintext []byte) ([]byte, error) {
+	if len(key) != 32 {
+		return nil, fmt.Errorf("key is not 32 bytes")
+	}
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	_, err = io.ReadFull(rand.Reader, nonce)
+	if err != nil {
+		return nil, err
+	}
+
+	return gcm.Seal(nonce, nonce, plaintext, nil), nil
+}
+
+func GCMDecrypt(key []byte, ciphertext []byte) ([]byte, error) {
+	if len(key) != 32 {
+		return nil, fmt.Errorf("key is not 32 bytes")
+	}
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(ciphertext) < gcm.NonceSize() {
+		return nil, errors.New("malformed ciphertext")
+	}
+
+	return gcm.Open(nil,
+		ciphertext[:gcm.NonceSize()],
+		ciphertext[gcm.NonceSize():],
+		nil,
+	)
+}