From f5fc2d52b85df87a7024607e12527d59f02a590b Mon Sep 17 00:00:00 2001
From: Chocobo1 <Chocobo1@users.noreply.github.com>
Date: Tue, 20 Feb 2018 01:02:57 +0800
Subject: [PATCH] Fix loading very large torrents. Closes #8449.

`torrent_info` constructor has default limits that can't be changed via
parameters, so we handle the loading process manually and explicitly
specifiy the limits to `bdecode()`.
The token_limit is also changed to 10000000.
---
 src/base/bittorrent/torrentinfo.cpp | 48 ++++++++++++++++++++++++++---
 src/base/bittorrent/torrentinfo.h   |  3 ++
 2 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/src/base/bittorrent/torrentinfo.cpp b/src/base/bittorrent/torrentinfo.cpp
index 950d772c3..825c8c078 100644
--- a/src/base/bittorrent/torrentinfo.cpp
+++ b/src/base/bittorrent/torrentinfo.cpp
@@ -76,13 +76,51 @@ TorrentInfo TorrentInfo::load(const QByteArray &data, QString *error) noexcept
 
 TorrentInfo TorrentInfo::loadFromFile(const QString &path, QString *error) noexcept
 {
+    if (error)
+        error->clear();
+
+    QFile file {path};
+    if (!file.open(QIODevice::ReadOnly)) {
+        if (error)
+            *error = file.errorString();
+        return TorrentInfo();
+    }
+
+    const qint64 fileSizeLimit = 100 * 1024 * 1024;  // 100 MB
+    if (file.size() > fileSizeLimit) {
+        if (error)
+            *error = tr("File size exceeds max limit %1").arg(fileSizeLimit);
+        return TorrentInfo();
+    }
+
+    const QByteArray data = file.read(fileSizeLimit);
+    if (data.size() != file.size()) {
+        if (error)
+            *error = tr("Torrent file read error");
+        return TorrentInfo();
+    }
+
+    file.close();
+
+    // 2-step construction to overcome default limits of `depth_limit` & `token_limit` which are
+    // used in `torrent_info()` constructor
+    const int depthLimit = 100;
+    const int tokenLimit = 10000000;
+    libt::bdecode_node node;
     libt::error_code ec;
-    TorrentInfo info(NativePtr(new libt::torrent_info(Utils::Fs::toNativePath(path).toStdString(), ec)));
-    if (error) {
-        if (ec)
+    bdecode(data.constData(), (data.constData() + data.size()), node, ec
+        , nullptr, depthLimit, tokenLimit);
+    if (ec) {
+        if (error)
             *error = QString::fromStdString(ec.message());
-        else
-            error->clear();
+        return TorrentInfo();
+    }
+
+    TorrentInfo info {NativePtr(new libt::torrent_info(node, ec))};
+    if (ec) {
+        if (error)
+            *error = QString::fromStdString(ec.message());
+        return TorrentInfo();
     }
 
     return info;
diff --git a/src/base/bittorrent/torrentinfo.h b/src/base/bittorrent/torrentinfo.h
index cb40c3927..85c8158d5 100644
--- a/src/base/bittorrent/torrentinfo.h
+++ b/src/base/bittorrent/torrentinfo.h
@@ -29,6 +29,7 @@
 #ifndef BITTORRENT_TORRENTINFO_H
 #define BITTORRENT_TORRENTINFO_H
 
+#include <QCoreApplication>
 #include <QtGlobal>
 
 #include <libtorrent/torrent_info.hpp>
@@ -51,6 +52,8 @@ namespace BitTorrent
 
     class TorrentInfo
     {
+        Q_DECLARE_TR_FUNCTIONS("TorrentInfo")
+
     public:
 #if LIBTORRENT_VERSION_NUM < 10100
         typedef boost::intrusive_ptr<const libtorrent::torrent_info> NativeConstPtr;