this fix introduces a KeyCheck verification for the code path that te…

…sts existing user keys available in the secret vault (as opposed to the codepath that uses the passphrase to unlock the license), see #51

src/lcp-client-lib/CryptoppCryptoProvider.cpp

@@ -295,8 +295,15 @@ namespace lcp
 
             //http://www.w3.org/2009/xmlenc11#aes256-gcm
             //http://www.w3.org/2001/04/xmlenc#aes256-cbc
-            const std::string algorithm = license->Crypto()->ContentKeyAlgorithm();
+            const std::string algorithm_ = license->Crypto()->ContentKeyAlgorithm();
+            std::unique_ptr<ISymmetricAlgorithm> contentKeyAlgorithm_(profile->CreateContentKeyAlgorithm(userKey, algorithm_));
+            std::string id = contentKeyAlgorithm_->Decrypt(license->Crypto()->UserKeyCheck());
+            if (!EqualsUtf8(id, license->Id()))
+            {
+                return Status(StatusCode::ErrorDecryptionUserPassphraseNotValid, "ErrorDecryptionUserPassphraseNotValid");
+            }
 
+            const std::string algorithm = license->Crypto()->ContentKeyAlgorithm();
             std::unique_ptr<ISymmetricAlgorithm> contentKeyAlgorithm(profile->CreateContentKeyAlgorithm(userKey, algorithm));
             std::string decryptedContentKey = contentKeyAlgorithm->Decrypt(license->Crypto()->ContentKey());