Truncate ciphertext buffer to actual size during file encryption

The ciphertext for AES CTR is exactly as large as the plaintext (not
necessarily a multiple of the blocksize!). By truncating the ciphertext,
we do not send bytes that will be decrypted to gibberish.

As a side node, we probably do not need to initialize the ciphertext
buffer larger than the plaintext size at all, but the OpenSSL docs are a
bit vague about that.

1 files changed, 3 insertions, 1 deletions

diff --git a/autotests/testfilecrypto.cpp b/autotests/testfilecrypto.cpp
index e6bec1fe..5d549b89 100644
--- a/autotests/testfilecrypto.cpp
+++ b/autotests/testfilecrypto.cpp
@@ -12,6 +12,8 @@ void TestFileCrypto::encryptDecryptData()
     QByteArray data = "ABCDEF";
     auto [file, cipherText] = EncryptedFile::encryptFile(data);
     auto decrypted = file.decryptFile(cipherText);
-    QCOMPARE(data, decrypted);
+    QCOMPARE(cipherText.size(), data.size());
+    QCOMPARE(decrypted.size(), data.size());
+    QCOMPARE(decrypted, data);
 }
 QTEST_APPLESS_MAIN(TestFileCrypto)