Add support for getting the real process id from within the suid sandbox. The...

chrome/browser/zygote_host_linux.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/zygote_host_linux.h"
 
-#include <unistd.h>
-#include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
 
 #include "base/command_line.h"
 #include "base/eintr_wrapper.h"
+#include "base/linux_util.h"
 #include "base/logging.h"
 #include "base/path_service.h"
 #include "base/pickle.h"
 #include "base/process_util.h"
 #include "base/string_util.h"
 #include "base/unix_domain_socket_posix.h"
 
 #include "chrome/browser/renderer_host/render_sandbox_host_linux.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_switches.h"
+#include "chrome/common/process_watcher.h"
 
 #include "sandbox/linux/suid/suid_unsafe_environment_variables.h"
 
 static void SaveSUIDUnsafeEnvironmentVariables() {
   // The ELF loader will clear many environment variables so we save them to
   // different names here so that the SUID sandbox can resolve them for the
   // renderer.
 
   for (unsigned i = 0; kSUIDUnsafeEnvironmentVariables[i]; ++i) {
     const char* const envvar = kSUIDUnsafeEnvironmentVariables[i];
     char* const saved_envvar = SandboxSavedEnvironmentVariable(envvar);
     if (!saved_envvar)
       continue;
 
     const char* const value = getenv(envvar);
     if (value)
       setenv(saved_envvar, value, 1 /* overwrite */);
     else
       unsetenv(saved_envvar);
 
     free(saved_envvar);
   }
 }
 
-ZygoteHost::ZygoteHost() {
+ZygoteHost::ZygoteHost()
+    : pid_(-1),
+      init_(false) {
+}
+
+ZygoteHost::~ZygoteHost() {
+  if (init_)
+    close(control_fd_);
+}
+
+void ZygoteHost::Init(const std::string& sandbox_cmd) {
+  DCHECK(!init_);
+  init_ = true;
+
   FilePath chrome_path;
   CHECK(PathService::Get(base::FILE_EXE, &chrome_path));
   CommandLine cmd_line(chrome_path);
 
   cmd_line.AppendSwitchWithValue(switches::kProcessType,
                                  switches::kZygoteProcess);
 
   int fds[2];
   CHECK(socketpair(PF_UNIX, SOCK_SEQPACKET, 0, fds) == 0);
   base::file_handle_mapping_vector fds_to_map;
@@ skipping 16 matching lines @@
                                    browser_command_line.GetSwitchValue(
                                        switches::kLoggingLevel));
   }
   if (browser_command_line.HasSwitch(switches::kEnableLogging)) {
     // Append with value to support --enable-logging=stderr.
     cmd_line.AppendSwitchWithValue(switches::kEnableLogging,
                                    browser_command_line.GetSwitchValue(
                                        switches::kEnableLogging));
   }
 
-  const char* sandbox_binary = NULL;
+  const char* sandbox_binary = sandbox_cmd.c_str();
   struct stat st;
 
-  // In Chromium branded builds, developers can set an environment variable to
-  // use the development sandbox. See
-  // http://code.google.com/p/chromium/wiki/LinuxSUIDSandboxDevelopment
-  if (stat("/proc/self/exe", &st) == 0 &&
-      st.st_uid == getuid()) {
-    sandbox_binary = getenv("CHROME_DEVEL_SANDBOX");
-  }
-
-#if defined(LINUX_SANDBOX_PATH)
-  if (!sandbox_binary)
-    sandbox_binary = LINUX_SANDBOX_PATH;
-#endif
-
-  if (sandbox_binary && stat(sandbox_binary, &st) == 0) {
+  bool using_suid_sandbox = false;
+  if (!sandbox_cmd.empty() && stat(sandbox_binary, &st) == 0) {
     if (access(sandbox_binary, X_OK) == 0 &&
         (st.st_mode & S_ISUID) &&
         (st.st_mode & S_IXOTH)) {
+      using_suid_sandbox = true;
       cmd_line.PrependWrapper(ASCIIToWide(sandbox_binary));
 
       SaveSUIDUnsafeEnvironmentVariables();
     } else {
       LOG(FATAL) << "The SUID sandbox helper binary was found, but is not "
                     "configured correctly. Rather than run without sandboxing "
                     "I'm aborting now. You need to make sure that "
                  << sandbox_binary << " is mode 4755.";
     }
   }
 
   // Start up the sandbox host process and get the file descriptor for the
   // renderers to talk to it.
   const int sfd = Singleton<RenderSandboxHostLinux>()->GetRendererSocket();
   fds_to_map.push_back(std::make_pair(sfd, 5));
 
+  int dummy_fd = -1;
+  if (using_suid_sandbox) {
+    dummy_fd = socket(PF_UNIX, SOCK_DGRAM, 0);
+    CHECK(dummy_fd >= 0);
+    fds_to_map.push_back(std::make_pair(dummy_fd, 7));
+  }
+
   base::ProcessHandle process;
   base::LaunchApp(cmd_line.argv(), fds_to_map, false, &process);
   CHECK(process != -1) << "Failed to launch zygote process";
 
-  pid_ = process;
+  if (using_suid_sandbox) {
+    // In the SUID sandbox, the real zygote is forked from the sandbox.
+    // We need to look for it.
+    // But first, wait for the zygote to tell us it's running.
+    // The sending code is in chrome/browser/zygote_main_linux.cc.
+    std::vector<int> fds_vec;
+    const int kExpectedLength = sizeof(kZygoteMagic);
+    char buf[kExpectedLength];
+    const ssize_t len = base::RecvMsg(fds[0], buf, sizeof(buf), &fds_vec);
+    CHECK(len == kExpectedLength) << "Incorrect zygote magic length";
+    CHECK(0 == strcmp(buf, kZygoteMagic)) << "Incorrect zygote magic";
+
+    std::string inode_output;
+    ino_t inode = 0;
+    // Figure out the inode for |dummy_fd|, close |dummy_fd| on our end,
+    // and find the zygote process holding |dummy_fd|.
+    if (base::FileDescriptorGetInode(&inode, dummy_fd)) {
+      close(dummy_fd);
+      std::vector<std::string> get_inode_cmdline;
+      get_inode_cmdline.push_back(sandbox_binary);
+      get_inode_cmdline.push_back(base::kFindInodeSwitch);
+      get_inode_cmdline.push_back(IntToString(inode));
+      CommandLine get_inode_cmd(get_inode_cmdline);
+      if (base::GetAppOutput(get_inode_cmd, &inode_output)) {
+        StringToInt(inode_output, &pid_);
+      }
+    }
+    CHECK(pid_ > 0) << "Did not find zygote process";
+
+    if (process != pid_) {
+      // Reap the sandbox.
+      ProcessWatcher::EnsureProcessGetsReaped(process);
+    }
+  } else {
+    // Not using the SUID sandbox.
+    pid_ = process;
+  }
+
   close(fds[1]);
   control_fd_ = fds[0];
 }
 
-ZygoteHost::~ZygoteHost() {
-  close(control_fd_);
-}
-
 pid_t ZygoteHost::ForkRenderer(
     const std::vector<std::string>& argv,
     const base::GlobalDescriptors::Mapping& mapping) {
+  DCHECK(init_);
   Pickle pickle;
 
   pickle.WriteInt(kCmdFork);
   pickle.WriteInt(argv.size());
   for (std::vector<std::string>::const_iterator
        i = argv.begin(); i != argv.end(); ++i)
     pickle.WriteString(*i);
 
   pickle.WriteInt(mapping.size());
 
   std::vector<int> fds;
   for (base::GlobalDescriptors::Mapping::const_iterator
        i = mapping.begin(); i != mapping.end(); ++i) {
     pickle.WriteUInt32(i->first);
     fds.push_back(i->second);
   }
 
   if (!base::SendMsg(control_fd_, pickle.data(), pickle.size(), fds))
     return -1;
 
   pid_t pid;
   if (HANDLE_EINTR(read(control_fd_, &pid, sizeof(pid))) != sizeof(pid))
     return -1;
 
   return pid;
 }
 
 void ZygoteHost::EnsureProcessTerminated(pid_t process) {
+  DCHECK(init_);
   Pickle pickle;
 
   pickle.WriteInt(kCmdReap);
   pickle.WriteInt(process);
 
   HANDLE_EINTR(write(control_fd_, pickle.data(), pickle.size()));
 }
 
 bool ZygoteHost::DidProcessCrash(base::ProcessHandle handle,
                                  bool* child_exited) {
+  DCHECK(init_);
   Pickle pickle;
   pickle.WriteInt(kCmdDidProcessCrash);
   pickle.WriteInt(handle);
 
   HANDLE_EINTR(write(control_fd_, pickle.data(), pickle.size()));
 
   static const unsigned kMaxMessageLength = 128;
   char buf[kMaxMessageLength];
   const ssize_t len = HANDLE_EINTR(read(control_fd_, buf, sizeof(buf)));
 
@@ skipping 12 matching lines @@
       !read_pickle.ReadBool(&iter, &tmp_child_exited)) {
     LOG(WARNING) << "Error parsing DidProcessCrash response from zygote.";
     return false;
   }
 
   if (child_exited)
     *child_exited = tmp_child_exited;
 
   return did_crash;
 }