new helpers for drive decryption (#73)

* new helpers for drive decryption

* modular helper functions and reciprocals

* removed duplicates helper functions

* added mobile wrapper

* unit tests for new helpers

Co-authored-by: wussler <aron@wussler.it>

helper/helper_test.go

@@ -1,6 +1,7 @@
 package helper
 
 import (
+	"bytes"
 	"testing"
 
 	"github.com/ProtonMail/gopenpgp/v2/crypto"
@@ -154,3 +155,64 @@ func TestArmoredBinaryMessageEncryption(t *testing.T) {
 
 	assert.Exactly(t, plainData, decrypted)
 }
+
+func TestEncryptSignArmoredDetached(t *testing.T) {
+	plainData := []byte("Secret message")
+	privateKeyString := readTestFile("keyring_privateKey", false)
+	privateKey, err := crypto.NewKeyFromArmored(privateKeyString)
+	if err != nil {
+		t.Fatal("Error reading the test private key: ", err)
+	}
+	publicKeyString, err := privateKey.GetArmoredPublicKey()
+	if err != nil {
+		t.Fatal("Error reading the test public key: ", err)
+	}
+	armoredCiphertext, armoredSignature, err := EncryptSignArmoredDetached(
+		publicKeyString,
+		privateKeyString,
+		testMailboxPassword, // Password defined in base_test
+		plainData,
+	)
+	if err != nil {
+		t.Fatal("Expected no error while encrypting and signing, got:", err)
+	}
+
+	decrypted, err := DecryptVerifyArmoredDetached(
+		publicKeyString,
+		privateKeyString,
+		testMailboxPassword,
+		armoredCiphertext,
+		armoredSignature,
+	)
+
+	if err != nil {
+		t.Fatal("Expected no error while decrypting and verifying, got:", err)
+	}
+
+	if !bytes.Equal(decrypted, plainData) {
+		t.Error("Decrypted is not equal to the plaintext")
+	}
+
+	_, modifiedSignature, err := EncryptSignArmoredDetached(
+		publicKeyString,
+		privateKeyString,
+		testMailboxPassword, // Password defined in base_test
+		[]byte("Different message"),
+	)
+
+	if err != nil {
+		t.Fatal("Expected no error while encrypting and signing, got:", err)
+	}
+
+	_, err = DecryptVerifyArmoredDetached(
+		publicKeyString,
+		privateKeyString,
+		testMailboxPassword,
+		armoredCiphertext,
+		modifiedSignature,
+	)
+
+	if err == nil {
+		t.Fatal("Expected an error while decrypting and verifying with a wrong signature")
+	}
+}