Verify the signatures of spotify blob files downloaded at runtime. Should protect against MITM attacks, and compromises of our server.

CMakeLists.txt

@@ -68,6 +68,7 @@ pkg_check_modules(LIBMTP libmtp>=1.0)
 pkg_check_modules(INDICATEQT indicate-qt)
 pkg_check_modules(SPOTIFY libspotify>=0.0.8)
 pkg_check_modules(CDIO libcdio)
+pkg_check_modules(QCA qca2)
 
 if (WIN32)
   find_package(ZLIB REQUIRED)
@@ -233,9 +234,9 @@ if(ENABLE_BREAKPAD)
   set(HAVE_BREAKPAD ON)
 endif(ENABLE_BREAKPAD)
 
-if(ENABLE_SPOTIFY AND PROTOBUF_FOUND AND PROTOBUF_PROTOC_EXECUTABLE)
+if(ENABLE_SPOTIFY AND PROTOBUF_FOUND AND PROTOBUF_PROTOC_EXECUTABLE AND QCA_FOUND)
   set(HAVE_SPOTIFY ON)
-endif(ENABLE_SPOTIFY AND PROTOBUF_FOUND AND PROTOBUF_PROTOC_EXECUTABLE)
+endif(ENABLE_SPOTIFY AND PROTOBUF_FOUND AND PROTOBUF_PROTOC_EXECUTABLE AND QCA_FOUND)
 
 if(ENABLE_SPOTIFY_BLOB AND PROTOBUF_FOUND AND PROTOBUF_PROTOC_EXECUTABLE AND SPOTIFY_FOUND)
   set(HAVE_SPOTIFY_BLOB ON)

data/clementine-spotify-public.pem

@@ -0,0 +1,9 @@
+-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAqAvoUlyct8cM/dM5OBwP
+sqXNJEbxdMsbtX8fXErcj+r1qSlOG1KtFZmVXw8FZtq3WQddgb95w/T8zvP1v0dt
+6ZbsYlsE+TqTiTcN1rpbVi33SpcWGZ7d2o+bbTEaVagVuwccPDvfMu005/zzFl0f
+iRVg2zLkFYuLRDZpOwbgw7KBKTVqaB/aeRK/sjXSjaZdizuxW4WnmKYWML3h4RpZ
+kg5+faMQiG9sA0iH27PzXPZWVG9Py2ypyVA4pSQIZFveYbr9XpcxPhcEalXbxNU8
+S7OzDbWmjNIh7KCMy2F7NxnW92b+7WRUcjp953U2LKtcppZK3AOlnETzkHcmB7cD
+sQIDAQAB
+-----END PUBLIC KEY-----

data/data.qrc

@@ -329,5 +329,6 @@
         <file>providers/grooveshark.png</file>
         <file>allthethings.png</file>
         <file>globalsearch.css</file>
+        <file>clementine-spotify-public.pem</file>
     </qresource>
 </RCC>

src/CMakeLists.txt

@@ -709,6 +709,8 @@ optional_source(HAVE_SPOTIFY
     internet/spotifyservice.h
     internet/spotifysettingspage.h
     resolvers/spotifyresolver.h
+  INCLUDE_DIRECTORIES
+    ${QCA_INCLUDE_DIRS}
 )
 
 # Platform specific - OS X
@@ -1047,6 +1049,7 @@ if(HAVE_SPOTIFY)
   target_link_libraries(clementine_lib
     clementine-spotifyblob-messages
     gstspotifytcpsrc
+    ${QCA_LIBRARIES}
   )
 endif(HAVE_SPOTIFY)
 

src/internet/spotifyblobdownloader.cpp

@@ -19,11 +19,16 @@
 #include "spotifyservice.h"
 #include "core/logging.h"
 #include "core/network.h"
+#include "core/utilities.h"
 
 #include <QDir>
 #include <QMessageBox>
 #include <QNetworkReply>
 #include <QProgressDialog>
+#include <QtCrypto>
+
+const char* SpotifyBlobDownloader::kSignatureSuffix = ".sha1";
+
 
 SpotifyBlobDownloader::SpotifyBlobDownloader(
       const QString& version, const QString& path, QObject* parent)
@@ -56,7 +61,10 @@ void SpotifyBlobDownloader::Start() {
   qDeleteAll(replies_);
   replies_.clear();
 
-  const QStringList filenames = QStringList() << "blob" << "libspotify.so.8";
+  const QStringList filenames = QStringList()
+      << "blob"
+      << "blob" + QString(kSignatureSuffix)
+      << "libspotify.so.8";
 
   foreach (const QString& filename, filenames) {
     const QUrl url(SpotifyService::kBlobDownloadUrl + version_ + "/" + filename);
@@ -87,12 +95,14 @@ void SpotifyBlobDownloader::ReplyFinished() {
     }
   }
 
-  // Make the destination directory and write the files into it
-  QDir().mkpath(path_);
+  // Let's verify signatures in a temporary directory first, before we write
+  // anything into its final position.
+  QString temp_directory = Utilities::MakeTempDir();
+  QStringList signatures;
 
   foreach (QNetworkReply* reply, replies_) {
     const QString filename = reply->url().path().section('/', -1, -1);
-    const QString path = path_ + "/" + filename;
+    const QString path = temp_directory + "/" + filename;
 
     qLog(Info) << "Saving file" << path;
     QFile file(path);
@@ -101,10 +111,69 @@ void SpotifyBlobDownloader::ReplyFinished() {
       return;
     }
 
+    if (path.endsWith(kSignatureSuffix)) {
+      signatures << path;
+    }
+
     file.setPermissions(QFile::Permissions(0x7755));
     file.write(reply->readAll());
   }
 
+  // Load the public key
+  QCA::ConvertResult conversion_result;
+  QCA::PublicKey key = QCA::PublicKey::fromPEMFile(":/clementine-spotify-public.pem",
+                                                   &conversion_result);
+  if (QCA::ConvertGood != conversion_result) {
+    ShowError("Failed to load Spotify public key");
+    return;
+  }
+
+  // Verify signatures
+  foreach (const QString& signature_filename, signatures) {
+    QString filename = signature_filename;
+    filename.remove(kSignatureSuffix);
+
+    qLog(Debug) << "Verifying" << filename << "against" << signature_filename;
+
+    QFile actual_file(filename);
+    if (!actual_file.open(QIODevice::ReadOnly))
+      return;
+
+    QFile signature_file(signature_filename);
+    if (!signature_file.open(QIODevice::ReadOnly))
+      return;
+
+    if (!key.verifyMessage(actual_file.readAll(), signature_file.readAll(),
+                           QCA::EMSA3_SHA1)) {
+      ShowError("Invalid signature: " + filename);
+      return;
+    }
+
+    qLog(Debug) << "Verification OK";
+  }
+
+  // Make the destination directory and write the files into it
+  QDir().mkpath(path_);
+
+  foreach (QNetworkReply* reply, replies_) {
+    const QString filename = reply->url().path().section('/', -1, -1);
+    const QString source_path = temp_directory + "/" + filename;
+    const QString dest_path = path_ + "/" + filename;
+
+    if (filename.endsWith(kSignatureSuffix))
+      continue;
+
+    qLog(Info) << "Moving" << source_path << "to" << dest_path;
+
+    if (!QFile::rename(source_path, dest_path)) {
+      ShowError("Writing file failed: " + dest_path);
+      return;
+    }
+  }
+
+  // Remove the temporary directory
+  Utilities::RemoveRecursive(temp_directory);
+
   EmitFinished();
 }
 

src/internet/spotifyblobdownloader.h

@@ -32,6 +32,8 @@ public:
                         QObject* parent = 0);
   ~SpotifyBlobDownloader();
 
+  static const char* kSignatureSuffix;
+
   static bool Prompt();
 
   void Start();

src/main.cpp

@@ -78,6 +78,10 @@ using boost::scoped_ptr;
 
 #include <echonest/Config.h>
 
+#ifdef HAVE_SPOTIFY
+  #include <QtCrypto>
+#endif
+
 #ifdef Q_OS_DARWIN
   #include <sys/resource.h>
   #include <sys/sysctl.h>
@@ -369,6 +373,10 @@ int main(int argc, char *argv[]) {
   }
 #endif
 
+#ifdef HAVE_SPOTIFY
+  QCA::Initializer qca_initializer;
+#endif
+
   // Resources
   Q_INIT_RESOURCE(data);
   Q_INIT_RESOURCE(translations);

src/translations/translations.pot

@@ -566,7 +566,7 @@ msgstr ""
 msgid "Always start playing"
 msgstr ""
 
-#: internet/spotifyblobdownloader.cpp:50
+#: internet/spotifyblobdownloader.cpp:55
 msgid ""
 "An additional plugin is required to use Spotify in Clementine.  Would you "
 "like to download and install it now?"
@@ -793,7 +793,7 @@ msgstr ""
 msgid "CUE sheet support"
 msgstr ""
 
-#: internet/spotifyblobdownloader.cpp:34
+#: internet/spotifyblobdownloader.cpp:39
 msgid "Cancel"
 msgstr ""
 
@@ -1432,7 +1432,7 @@ msgstr ""
 msgid "Downloading Magnatune catalogue"
 msgstr ""
 
-#: internet/spotifyblobdownloader.cpp:34
+#: internet/spotifyblobdownloader.cpp:39
 msgid "Downloading Spotify plugin"
 msgstr ""
 
@@ -1584,7 +1584,7 @@ msgstr ""
 msgid "Error deleting songs"
 msgstr ""
 
-#: internet/spotifyblobdownloader.cpp:137
+#: internet/spotifyblobdownloader.cpp:205
 msgid "Error downloading Spotify plugin"
 msgstr ""
 
@@ -3696,7 +3696,7 @@ msgstr ""
 msgid "Spotify plugin"
 msgstr ""
 
-#: internet/spotifyblobdownloader.cpp:49
+#: internet/spotifyblobdownloader.cpp:54
 msgid "Spotify plugin not installed"
 msgstr ""