From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Raymond Zhao <raymondzhao@microsoft.com>
Date: Tue, 7 Sep 2021 14:54:25 -0700
Subject: feat: Add data parameter to ProcessSingleton

This patch adds an additional_data parameter to the constructor of
ProcessSingleton, so that the second instance can send additional
data over to the first instance while requesting the ProcessSingleton
lock.

On the Electron side, we then expose an extra parameter to the
app.requestSingleInstanceLock API so that users can pass in a JSON
object for the second instance to send to the first instance.

diff --git a/chrome/browser/process_singleton.h b/chrome/browser/process_singleton.h
index 9de82e5422428d6419a24401e0479fbd19a15147..a30b3aae436bbe762ada1bdae69ef83127f0144b 100644
--- a/chrome/browser/process_singleton.h
+++ b/chrome/browser/process_singleton.h
@@ -18,6 +18,7 @@
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
 #include "base/process/process.h"
+#include "base/containers/span.h"
 #include "ui/gfx/native_widget_types.h"
 
 #if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_ANDROID)
@@ -99,22 +100,25 @@ class ProcessSingleton {
   // handled within the current browser instance or false if the remote process
   // should handle it (i.e., because the current process is shutting down).
   using NotificationCallback =
-      base::RepeatingCallback<bool(const base::CommandLine& command_line,
-                                   const base::FilePath& current_directory)>;
+       base::RepeatingCallback<bool(const base::CommandLine& command_line,
+                                   const base::FilePath& current_directory,
+                                   const std::vector<const uint8_t> additional_data)>;
 
 #if BUILDFLAG(IS_WIN)
   ProcessSingleton(const std::string& program_name,
                    const base::FilePath& user_data_dir,
+                   const base::span<const uint8_t> additional_data,
                    bool is_sandboxed,
                    const NotificationCallback& notification_callback);
 #else
   ProcessSingleton(const base::FilePath& user_data_dir,
+                   const base::span<const uint8_t> additional_data,
                    const NotificationCallback& notification_callback);
+#endif
 
   ProcessSingleton(const ProcessSingleton&) = delete;
   ProcessSingleton& operator=(const ProcessSingleton&) = delete;
 
-#endif
   ~ProcessSingleton();
 
   // Notify another process, if available. Otherwise sets ourselves as the
@@ -178,7 +182,10 @@ class ProcessSingleton {
 #endif
 
  private:
+  // A callback to run when the first instance receives data from the second.
   NotificationCallback notification_callback_;  // Handler for notifications.
+  // Custom data to pass to the other instance during notify.
+  base::span<const uint8_t> additional_data_;
 
 #if BUILDFLAG(IS_WIN)
   bool EscapeVirtualization(const base::FilePath& user_data_dir);
diff --git a/chrome/browser/process_singleton_posix.cc b/chrome/browser/process_singleton_posix.cc
index 99b42b0e8f81c6a5696d56fede3e168cfc282cc3..c205a14239eb9aa2b422a45755d3b07935f379c8 100644
--- a/chrome/browser/process_singleton_posix.cc
+++ b/chrome/browser/process_singleton_posix.cc
@@ -607,6 +607,7 @@ class ProcessSingleton::LinuxWatcher
   // |reader| is for sending back ACK message.
   void HandleMessage(const std::string& current_dir,
                      const std::vector<std::string>& argv,
+                     const std::vector<const uint8_t> additional_data,
                      SocketReader* reader);
 
  private:
@@ -661,13 +662,16 @@ void ProcessSingleton::LinuxWatcher::StartListening(int socket) {
 }
 
 void ProcessSingleton::LinuxWatcher::HandleMessage(
-    const std::string& current_dir, const std::vector<std::string>& argv,
+    const std::string& current_dir,
+    const std::vector<std::string>& argv,
+    const std::vector<const uint8_t> additional_data,
     SocketReader* reader) {
   DCHECK(ui_task_runner_->BelongsToCurrentThread());
   DCHECK(reader);
 
   if (parent_->notification_callback_.Run(base::CommandLine(argv),
-                                          base::FilePath(current_dir))) {
+                                          base::FilePath(current_dir),
+                                          std::move(additional_data))) {
     // Send back "ACK" message to prevent the client process from starting up.
     reader->FinishWithACK(kACKToken, std::size(kACKToken) - 1);
   } else {
@@ -715,7 +719,8 @@ void ProcessSingleton::LinuxWatcher::SocketReader::
     }
   }
 
-  // Validate the message.  The shortest message is kStartToken\0x\0x
+  // Validate the message.  The shortest message kStartToken\0\00
+  // The shortest message with additional data is kStartToken\0\00\00\0.
   const size_t kMinMessageLength = std::size(kStartToken) + 4;
   if (bytes_read_ < kMinMessageLength) {
     buf_[bytes_read_] = 0;
@@ -745,10 +750,28 @@ void ProcessSingleton::LinuxWatcher::SocketReader::
   tokens.erase(tokens.begin());
   tokens.erase(tokens.begin());
 
+  size_t num_args;
+  base::StringToSizeT(tokens[0], &num_args);
+  std::vector<std::string> command_line(tokens.begin() + 1, tokens.begin() + 1 + num_args);
+
+  std::vector<const uint8_t> additional_data;
+  if (tokens.size() >= 3 + num_args) {
+    size_t additional_data_size;
+    base::StringToSizeT(tokens[1 + num_args], &additional_data_size);
+    std::string remaining_args = base::JoinString(
+        base::make_span(tokens.begin() + 2 + num_args, tokens.end()),
+        std::string(1, kTokenDelimiter));
+    const uint8_t* additional_data_bits =
+        reinterpret_cast<const uint8_t*>(remaining_args.c_str());
+    additional_data = std::vector<const uint8_t>(
+        additional_data_bits, additional_data_bits + additional_data_size);
+  }
+
   // Return to the UI thread to handle opening a new browser tab.
   ui_task_runner_->PostTask(
       FROM_HERE, base::BindOnce(&ProcessSingleton::LinuxWatcher::HandleMessage,
-                                parent_, current_dir, tokens, this));
+                                parent_, current_dir, command_line,
+                                std::move(additional_data), this));
   fd_watch_controller_.reset();
 
   // LinuxWatcher::HandleMessage() is in charge of destroying this SocketReader
@@ -777,8 +800,10 @@ void ProcessSingleton::LinuxWatcher::SocketReader::FinishWithACK(
 //
 ProcessSingleton::ProcessSingleton(
     const base::FilePath& user_data_dir,
+    const base::span<const uint8_t> additional_data,
     const NotificationCallback& notification_callback)
     : notification_callback_(notification_callback),
+      additional_data_(additional_data),
       current_pid_(base::GetCurrentProcId()) {
   socket_path_ = user_data_dir.Append(chrome::kSingletonSocketFilename);
   lock_path_ = user_data_dir.Append(chrome::kSingletonLockFilename);
@@ -896,7 +921,8 @@ ProcessSingleton::NotifyResult ProcessSingleton::NotifyOtherProcessWithTimeout(
              sizeof(socket_timeout));
 
   // Found another process, prepare our command line
-  // format is "START\0<current dir>\0<argv[0]>\0...\0<argv[n]>".
+  // format is "START\0<current-dir>\0<n-args>\0<argv[0]>\0...\0<argv[n]>
+  // \0<additional-data-length>\0<additional-data>".
   std::string to_send(kStartToken);
   to_send.push_back(kTokenDelimiter);
 
@@ -906,11 +932,21 @@ ProcessSingleton::NotifyResult ProcessSingleton::NotifyOtherProcessWithTimeout(
   to_send.append(current_dir.value());
 
   const std::vector<std::string>& argv = cmd_line.argv();
+  to_send.push_back(kTokenDelimiter);
+  to_send.append(base::NumberToString(argv.size()));
   for (auto it = argv.begin(); it != argv.end(); ++it) {
     to_send.push_back(kTokenDelimiter);
     to_send.append(*it);
   }
 
+  size_t data_to_send_size = additional_data_.size_bytes();
+  if (data_to_send_size) {
+    to_send.push_back(kTokenDelimiter);
+    to_send.append(base::NumberToString(data_to_send_size));
+    to_send.push_back(kTokenDelimiter);
+    to_send.append(reinterpret_cast<const char*>(additional_data_.data()), data_to_send_size);
+  }
+
   // Send the message
   if (!WriteToSocket(socket.fd(), to_send.data(), to_send.length())) {
     // Try to kill the other process, because it might have been dead.
diff --git a/chrome/browser/process_singleton_win.cc b/chrome/browser/process_singleton_win.cc
index c375a587abd3d575b5c75a0863b01c9611e8287c..33948d69a4a3bf098187b1c383821d1d67be5818 100644
--- a/chrome/browser/process_singleton_win.cc
+++ b/chrome/browser/process_singleton_win.cc
@@ -80,10 +80,12 @@ BOOL CALLBACK BrowserWindowEnumeration(HWND window, LPARAM param) {
 
 bool ParseCommandLine(const COPYDATASTRUCT* cds,
                       base::CommandLine* parsed_command_line,
-                      base::FilePath* current_directory) {
+                      base::FilePath* current_directory,
+                      std::vector<const uint8_t>* parsed_additional_data) {
   // We should have enough room for the shortest command (min_message_size)
   // and also be a multiple of wchar_t bytes. The shortest command
-  // possible is L"START\0\0" (empty current directory and command line).
+  // possible is L"START\0\0" (empty command line, current directory,
+  // and additional data).
   static const int min_message_size = 7;
   if (cds->cbData < min_message_size * sizeof(wchar_t) ||
       cds->cbData % sizeof(wchar_t) != 0) {
@@ -133,6 +135,37 @@ bool ParseCommandLine(const COPYDATASTRUCT* cds,
     const std::wstring cmd_line =
         msg.substr(second_null + 1, third_null - second_null);
     *parsed_command_line = base::CommandLine::FromString(cmd_line);
+
+    const std::wstring::size_type fourth_null =
+        msg.find_first_of(L'\0', third_null + 1);
+    if (fourth_null == std::wstring::npos ||
+        fourth_null == msg.length()) {
+      // No additional data was provided.
+      return true;
+    }
+
+    // Get length of the additional data.
+    const std::wstring additional_data_length_string =
+        msg.substr(third_null + 1, fourth_null - third_null);
+    size_t additional_data_length;
+    base::StringToSizeT(additional_data_length_string, &additional_data_length);
+
+    const std::wstring::size_type fifth_null =
+        msg.find_first_of(L'\0', fourth_null + 1);
+    if (fifth_null == std::wstring::npos ||
+        fifth_null == msg.length()) {
+      LOG(WARNING) << "Invalid format for start command, we need a string in 6 "
+        "parts separated by NULLs";
+    }
+
+    // Get the actual additional data.
+    const std::wstring additional_data =
+        msg.substr(fourth_null + 1, fifth_null - fourth_null);
+    const uint8_t* additional_data_bytes =
+        reinterpret_cast<const uint8_t*>(additional_data.c_str());
+    *parsed_additional_data = std::vector<const uint8_t>(additional_data_bytes,
+        additional_data_bytes + additional_data_length);
+
     return true;
   }
   return false;
@@ -154,13 +187,14 @@ bool ProcessLaunchNotification(
 
   base::CommandLine parsed_command_line(base::CommandLine::NO_PROGRAM);
   base::FilePath current_directory;
-  if (!ParseCommandLine(cds, &parsed_command_line, &current_directory)) {
+  std::vector<const uint8_t> additional_data;
+  if (!ParseCommandLine(cds, &parsed_command_line, &current_directory, &additional_data)) {
     *result = TRUE;
     return true;
   }
 
-  *result = notification_callback.Run(parsed_command_line, current_directory) ?
-      TRUE : FALSE;
+  *result = notification_callback.Run(parsed_command_line,
+      current_directory, std::move(additional_data)) ? TRUE : FALSE;
   return true;
 }
 
@@ -261,9 +295,11 @@ bool ProcessSingleton::EscapeVirtualization(
 ProcessSingleton::ProcessSingleton(
     const std::string& program_name,
     const base::FilePath& user_data_dir,
+    const base::span<const uint8_t> additional_data,
     bool is_app_sandboxed,
     const NotificationCallback& notification_callback)
     : notification_callback_(notification_callback),
+      additional_data_(additional_data),
       program_name_(program_name),
       is_app_sandboxed_(is_app_sandboxed),
       is_virtualized_(false),
@@ -290,7 +326,7 @@ ProcessSingleton::NotifyResult ProcessSingleton::NotifyOtherProcess() {
     return PROCESS_NONE;
   }
 
-  switch (chrome::AttemptToNotifyRunningChrome(remote_window_)) {
+  switch (chrome::AttemptToNotifyRunningChrome(remote_window_, additional_data_)) {
     case chrome::NOTIFY_SUCCESS:
       return PROCESS_NOTIFIED;
     case chrome::NOTIFY_FAILED:
diff --git a/chrome/browser/win/chrome_process_finder.cc b/chrome/browser/win/chrome_process_finder.cc
index b64ed1d155a30582e48c9cdffcee9d0f25a53a6a..cfdb2d75532d270e3dd548eb7475a6cdbddf1016 100644
--- a/chrome/browser/win/chrome_process_finder.cc
+++ b/chrome/browser/win/chrome_process_finder.cc
@@ -36,7 +36,9 @@ HWND FindRunningChromeWindow(const base::FilePath& user_data_dir) {
   return base::win::MessageWindow::FindWindow(user_data_dir.value());
 }
 
-NotifyChromeResult AttemptToNotifyRunningChrome(HWND remote_window) {
+NotifyChromeResult AttemptToNotifyRunningChrome(
+    HWND remote_window,
+    const base::span<const uint8_t> additional_data) {
   TRACE_EVENT0("startup", "AttemptToNotifyRunningChrome");
 
   DCHECK(remote_window);
@@ -50,7 +52,8 @@ NotifyChromeResult AttemptToNotifyRunningChrome(HWND remote_window) {
   }
 
   // Send the command line to the remote chrome window.
-  // Format is "START\0<<<current directory>>>\0<<<commandline>>>".
+  // Format is
+  // "START\0<current-directory>\0<command-line>\0<additional-data-length>\0<additional-data>".
   std::wstring to_send(L"START\0", 6);  // want the NULL in the string.
   base::FilePath cur_dir;
   if (!base::GetCurrentDirectory(&cur_dir)) {
@@ -64,6 +67,22 @@ NotifyChromeResult AttemptToNotifyRunningChrome(HWND remote_window) {
       base::CommandLine::ForCurrentProcess()->GetCommandLineString());
   to_send.append(L"\0", 1);  // Null separator.
 
+  size_t additional_data_size = additional_data.size_bytes();
+  if (additional_data_size) {
+    // Send over the size, because the reinterpret cast to wchar_t could
+    // add padding.
+    to_send.append(base::UTF8ToWide(base::NumberToString(additional_data_size)));
+    to_send.append(L"\0", 1);  // Null separator.
+
+    size_t padded_size = additional_data_size / sizeof(wchar_t);
+    if (additional_data_size % sizeof(wchar_t) != 0) {
+      padded_size++;
+    }
+    to_send.append(reinterpret_cast<const wchar_t*>(additional_data.data()),
+                   padded_size);
+    to_send.append(L"\0", 1);  // Null separator.
+  }
+
   // Allow the current running browser window to make itself the foreground
   // window (otherwise it will just flash in the taskbar).
   ::AllowSetForegroundWindow(process_id);
diff --git a/chrome/browser/win/chrome_process_finder.h b/chrome/browser/win/chrome_process_finder.h
index 5516673cee019f6060077091e59498bf9038cd6e..8edea5079b46c2cba67833114eb9c21d85cfc22d 100644
--- a/chrome/browser/win/chrome_process_finder.h
+++ b/chrome/browser/win/chrome_process_finder.h
@@ -7,6 +7,7 @@
 
 #include <windows.h>
 
+#include "base/containers/span.h"
 #include "base/time/time.h"
 
 namespace base {
@@ -27,7 +28,9 @@ HWND FindRunningChromeWindow(const base::FilePath& user_data_dir);
 // Attempts to send the current command line to an already running instance of
 // Chrome via a WM_COPYDATA message.
 // Returns true if a running Chrome is found and successfully notified.
-NotifyChromeResult AttemptToNotifyRunningChrome(HWND remote_window);
+NotifyChromeResult AttemptToNotifyRunningChrome(
+    HWND remote_window,
+    const base::span<const uint8_t> additional_data);
 
 // Changes the notification timeout to |new_timeout|, returns the old timeout.
 base::TimeDelta SetNotificationTimeoutForTesting(base::TimeDelta new_timeout);
