3 files changed, 95 insertions, 5 deletions
diff --git a/SwifTools/AutoUpdater/AutoUpdater.h b/SwifTools/AutoUpdater/AutoUpdater.h
index a125229..fdd3a91 100644
--- a/SwifTools/AutoUpdater/AutoUpdater.h
+++ b/SwifTools/AutoUpdater/AutoUpdater.h
@@ -30,2 +30,3 @@ namespace Swift {
             virtual State getCurrentState() = 0;
+            virtual bool applicationInstallationLocationWritable() = 0;
 
diff --git a/SwifTools/AutoUpdater/SparkleAutoUpdater.h b/SwifTools/AutoUpdater/SparkleAutoUpdater.h
index 48b75e5..26e08da 100644
--- a/SwifTools/AutoUpdater/SparkleAutoUpdater.h
+++ b/SwifTools/AutoUpdater/SparkleAutoUpdater.h
@@ -23,7 +23,8 @@ namespace Swift {
             SparkleAutoUpdater(const std::string& appcastFeed);
-            ~SparkleAutoUpdater();
+            ~SparkleAutoUpdater() override;
 
-            void setAppcastFeed(const std::string& appcastFeed);
-            void checkForUpdates();
-            State getCurrentState();
+            void setAppcastFeed(const std::string& appcastFeed) override;
+            void checkForUpdates() override;
+            State getCurrentState() override;
+            bool applicationInstallationLocationWritable() override;
 
diff --git a/SwifTools/AutoUpdater/SparkleAutoUpdater.mm b/SwifTools/AutoUpdater/SparkleAutoUpdater.mm
index 4cf5837..b4a4c05 100644
--- a/SwifTools/AutoUpdater/SparkleAutoUpdater.mm
+++ b/SwifTools/AutoUpdater/SparkleAutoUpdater.mm
@@ -8,2 +8,6 @@
 
+
+#include <boost/filesystem.hpp>
+#include <boost/filesystem/fstream.hpp>
+
 #include <Cocoa/Cocoa.h>
@@ -11,2 +15,4 @@
 
+#include <Swiften/Base/Log.h>
+
 #include <SwifTools/AutoUpdater/SparkleAutoUpdaterDelegate.h>
@@ -36,3 +42,9 @@ SparkleAutoUpdater::SparkleAutoUpdater(const std::string& appcastFeed) : d(new P
     [d->updater setUpdateCheckInterval: 86400];
-    [d->updater setAutomaticallyDownloadsUpdates: true];
+
+    auto canDoSilentUpdates = applicationInstallationLocationWritable();
+    [d->updater setAutomaticallyDownloadsUpdates: canDoSilentUpdates];
+
+    SWIFT_LOG(debug) << (canDoSilentUpdates ?
+        "The current running user has enough permissions to do a silent update." :
+        "The current running user has insufficient permissions to do a silent update.") << std::endl;
 
@@ -69,2 +81,78 @@ AutoUpdater::State SparkleAutoUpdater::getCurrentState() {
 
+bool Swift::SparkleAutoUpdater::applicationInstallationLocationWritable() {
+    auto bundlePath = ns2StdString([[NSBundle mainBundle] bundlePath]);
+
+    auto createTemporaryFile = [](const boost::filesystem::path& parentFolder) {
+        boost::optional<boost::filesystem::path> tempFilePath;
+        boost::system::error_code error;
+
+        if (!boost::filesystem::is_directory(parentFolder, error) || error) {
+            return tempFilePath;
+        }
+        auto uniquePath = boost::filesystem::unique_path("%%%%-%%%%-%%%%-%%%%", error);
+        if (error) {
+            return tempFilePath;
+        }
+        auto testFilePath = parentFolder / uniquePath;
+
+        boost::filesystem::ofstream testFile(testFilePath, std::ios::in | std::ios::out | std::ios::binary | std::ios::trunc);
+        if (testFile) {
+            testFile.close();
+            tempFilePath = testFilePath;
+        }
+
+        return tempFilePath;
+    };
+
+    auto isDirectoryWritable = [&](const boost::filesystem::path& path) {
+        auto bundleTestFilePath = createTemporaryFile(path);
+        if (!bundleTestFilePath) {
+            return false;
+        }
+
+        boost::system::error_code error;
+        if (!boost::filesystem::remove(bundleTestFilePath.get(), error) || error) {
+            // File did not exist in the first place or error while removing it.
+            return false;
+        }
+
+        return true;
+    };
+
+    auto applyMatchingPermissions = [](const boost::filesystem::path& permissionsFrom, const boost::filesystem::path& applyTo) {
+        auto permissions = boost::filesystem::status(permissionsFrom).permissions();
+
+        boost::system::error_code error;
+        boost::filesystem::permissions(applyTo, permissions, error);
+
+        return !error;
+    };
+
+    auto canChangePermissionsOnTemporaryFile = [&](const boost::filesystem::path& pathToCreateTemporaryFileUnder, const boost::filesystem::path& pathToTakePermissionsFrom) {
+        auto temporaryFilePath = createTemporaryFile(pathToCreateTemporaryFileUnder);
+        if (!temporaryFilePath) {
+            return false;
+        }
+
+        boost::system::error_code error;
+        auto fileExists = boost::filesystem::exists(temporaryFilePath.get(), error);
+        if (!fileExists || error) {
+            return false;
+        }
+
+        auto successfullPermissionCopy = applyMatchingPermissions(pathToTakePermissionsFrom, temporaryFilePath.get());
+
+        boost::filesystem::remove(temporaryFilePath.get(), error);
+
+        return successfullPermissionCopy;
+    };
+
+    auto bundleBoostPath = boost::filesystem::path(bundlePath);
+    if (!isDirectoryWritable(bundleBoostPath.parent_path()) || !isDirectoryWritable(bundleBoostPath)) {
+        return false;
+    }
+
+    return canChangePermissionsOnTemporaryFile(bundleBoostPath.parent_path(), bundleBoostPath);
+}
+
 }