add encryption and get page

internal/crypto/cipher.go

@@ -0,0 +1,32 @@
+package crypto
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+)
+
+var (
+	someDumbKey = []byte("9530e001b619e8e98a889055f06821bb")
+)
+
+func Encrypt(plaintext string) (hexed string, err error) {
+	aes, err := aes.NewCipher(someDumbKey)
+	if err != nil {
+		return "", fmt.Errorf("making new cipher: %w", err)
+	}
+	gcm, err := cipher.NewGCM(aes)
+	if err != nil {
+		return "", fmt.Errorf("making new gcm: %w", err)
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	_, err = rand.Read(nonce)
+	if err != nil {
+		return "", fmt.Errorf("generating nonce: %w", err)
+	}
+	outvalue := gcm.Seal(nonce, nonce, []byte(plaintext), nil)
+	return hex.EncodeToString(outvalue), nil
+}

internal/crypto/decrypt_off.go

@@ -0,0 +1,10 @@
+//go:build !encon
+// +build !encon
+
+package crypto
+
+import "git.loyso.art/frx/eway/internal/entity"
+
+func Decrypt(hexedcipher string) (plaintext string, err error) {
+	return "", entity.SimpleError("this feature turned off")
+}

internal/crypto/decrypt_on.go

@@ -0,0 +1,35 @@
+//go:build encon
+// +build encon
+
+package crypto
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"encoding/hex"
+	"fmt"
+)
+
+func Decrypt(hexedcipher string) (plaintext string, err error) {
+	aes, err := aes.NewCipher(someDumbKey)
+	if err != nil {
+		return "", fmt.Errorf("making new cipher: %w", err)
+	}
+	gcm, err := cipher.NewGCM(aes)
+	if err != nil {
+		return "", fmt.Errorf("making new gcm: %w", err)
+	}
+
+	nonceSize := gcm.NonceSize()
+	valueDecoded, err := hex.DecodeString(hexedcipher)
+	if err != nil {
+		return "", fmt.Errorf("decoding hexed value: %w", err)
+	}
+	nonce, cipherText := valueDecoded[:nonceSize], valueDecoded[nonceSize:]
+	plaintextRaw, err := gcm.Open(nil, []byte(nonce), []byte(cipherText), nil)
+	if err != nil {
+		return "", fmt.Errorf("opening: %w", err)
+	}
+
+	return string(plaintextRaw), nil
+}