From 703b3f89ef54d9d40c9117788d0920b6b745bd62 Mon Sep 17 00:00:00 2001
From: Tobias Fella <fella@posteo.de>
Date: Sat, 12 Jun 2021 23:04:17 +0200
Subject: Implement (meg)olm key caching, megolm decrypting, EncryptedEvent
 decryption, handling of encrypted redactions and replies

---
 lib/encryptionmanager.cpp | 72 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 71 insertions(+), 1 deletion(-)

(limited to 'lib/encryptionmanager.cpp')

diff --git a/lib/encryptionmanager.cpp b/lib/encryptionmanager.cpp
index 48e6701c..d36d5a7a 100644
--- a/lib/encryptionmanager.cpp
+++ b/lib/encryptionmanager.cpp
@@ -31,7 +31,6 @@ using std::move;
 class EncryptionManager::Private {
 public:
     explicit Private()
-        : q(nullptr)
     {
     }
     ~Private() = default;
@@ -51,6 +50,73 @@ public:
             }
         }
     }
+    void loadSessions() {
+        QFile file { static_cast<Connection *>(q->parent())->stateCacheDir().filePath("olmsessions.json") };
+        if(!file.exists() || !file.open(QIODevice::ReadOnly)) {
+            qCDebug(E2EE) << "No sessions cache exists.";
+            return;
+        }
+        auto data = file.readAll();
+        const auto json = data.startsWith('{')
+            ? QJsonDocument::fromJson(data).object()
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
+            : QCborValue::fromCbor(data).toJsonValue().toObject()
+#else
+            : QJsonDocument::fromBinaryData(data).object()
+#endif
+            ;
+        if (json.isEmpty()) {
+            qCWarning(MAIN) << "Sessions cache is empty";
+            return;
+        }
+        for(const auto &senderKey : json["sessions"].toObject().keys()) {
+            auto pickle = json["sessions"].toObject()[senderKey].toString();
+            auto sessionResult = QOlmSession::unpickle(pickle.toLatin1(), Unencrypted{});
+            if(std::holds_alternative<QOlmError>(sessionResult)) {
+                qCWarning(E2EE) << "Failed to unpickle olm session";
+                continue;
+            }
+            sessions[senderKey] = std::move(std::get<std::unique_ptr<QOlmSession>>(sessionResult));
+        }
+    }
+    void saveSessions() {
+        QFile outFile { static_cast<Connection *>(q->parent())->stateCacheDir().filePath("olmsessions.json") };
+        if (!outFile.open(QFile::WriteOnly)) {
+            qCWarning(E2EE) << "Error opening" << outFile.fileName() << ":"
+                            << outFile.errorString();
+            qCWarning(E2EE) << "Failed to write olm sessions";
+            return;
+        }
+
+        QJsonObject rootObj {
+            { QStringLiteral("cache_version"),
+            QJsonObject {
+                { QStringLiteral("major"), 1 },
+                { QStringLiteral("minor"), 0 } } }
+        };
+        {
+            QJsonObject sessionsJson;
+            for (const auto &session : sessions) {
+                auto pickleResult = session.second->pickle(Unencrypted{});
+                if(std::holds_alternative<QOlmError>(pickleResult)) {
+                    qCWarning(E2EE) << "Failed to pickle session";
+                    continue;
+                }
+                sessionsJson[session.first] = QString(std::get<QByteArray>(pickleResult));
+            }
+            rootObj.insert(QStringLiteral("sessions"), sessionsJson);
+        }
+
+    #if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
+        const auto data = QJsonDocument(rootObj).toJson(QJsonDocument::Compact);
+    #else
+        QJsonDocument json { rootObj };
+        const auto data = json.toJson(QJsonDocument::Compact);
+    #endif
+
+        outFile.write(data.data(), data.size());
+        qCDebug(E2EE) << "Sessions saved to" << outFile.fileName();
+    }
     QString sessionDecryptPrekey(const QOlmMessage& message, const QString &senderKey, std::unique_ptr<QOlmAccount>& olmAccount)
     {
         Q_ASSERT(message.type() == QOlmMessage::PreKey);
@@ -60,6 +126,7 @@ public:
                 qCDebug(E2EE) << "Found inbound session";
                 const auto result = session.second->decrypt(message);
                 if(std::holds_alternative<QString>(result)) {
+                    saveSessions();
                     return std::get<QString>(result);
                 } else {
                     qCDebug(E2EE) << "Failed to decrypt prekey message";
@@ -79,6 +146,7 @@ public:
         const auto result = newSession->decrypt(message);
         sessions[senderKey] = std::move(newSession);
         if(std::holds_alternative<QString>(result)) {
+            saveSessions();
             return std::get<QString>(result);
         } else {
             qCDebug(E2EE) << "Failed to decrypt prekey message with new session";
@@ -91,6 +159,7 @@ public:
         for(auto& session : sessions) {
             const auto result = session.second->decrypt(message);
             if(std::holds_alternative<QString>(result)) {
+                saveSessions();
                 return std::get<QString>(result);
             }
         }
@@ -104,6 +173,7 @@ EncryptionManager::EncryptionManager(QObject* parent)
     , d(std::make_unique<Private>())
 {
     d->q = this;
+    d->loadSessions();
 }
 
 EncryptionManager::~EncryptionManager() = default;
-- 
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