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, 1 insertions, 0 deletions

diff --git a/lib/events/encryptedfile.cpp b/lib/events/encryptedfile.cpp
index 9cc3a0c8..140dca7f 100644
--- a/lib/events/encryptedfile.cpp
+++ b/lib/events/encryptedfile.cpp
@@ -67,6 +67,7 @@ std::pair<EncryptedFile, QByteArray> EncryptedFile::encryptFile(const QByteArray
     QByteArray cipherText(plainText.size() + EVP_MAX_BLOCK_LENGTH - 1, '\0');
     EVP_EncryptInit_ex(ctx, EVP_aes_256_ctr(), nullptr, reinterpret_cast<const unsigned char*>(k.data()),reinterpret_cast<const unsigned char*>(iv.data()));
     EVP_EncryptUpdate(ctx, reinterpret_cast<unsigned char*>(cipherText.data()), &length, reinterpret_cast<const unsigned char*>(plainText.data()), plainText.size());
+    cipherText.resize(length);
     EVP_EncryptFinal_ex(ctx, reinterpret_cast<unsigned char*>(cipherText.data()) + length, &length);
     EVP_CIPHER_CTX_free(ctx);