Add seccomp sandbox for non-SFI NaCl

components/nacl/loader/nacl_helper_linux.cc

Index: components/nacl/loader/nacl_helper_linux.cc
diff --git a/components/nacl/loader/nacl_helper_linux.cc b/components/nacl/loader/nacl_helper_linux.cc
index c8139bf25ecaa557b0627d5179e7a696ad58bcf1..33bd65ff71401e317294625f7ef5202faee3799a 100644
--- a/components/nacl/loader/nacl_helper_linux.cc
+++ b/components/nacl/loader/nacl_helper_linux.cc
@@ -47,15 +47,24 @@ struct NaClLoaderSystemInfo {
 // side of the fork. See zygote_main_linux.cc:HandleForkRequest from
 //   if (!child) {
 void BecomeNaClLoader(const std::vector<int>& child_fds,
-                      const NaClLoaderSystemInfo& system_info) {
+                      const NaClLoaderSystemInfo& system_info,
+                      bool uses_nonsfi) {
   VLOG(1) << "NaCl loader: setting up IPC descriptor";
   // don't need zygote FD any more

[jln (very slow on Chromium), 2014/03/20 00:54:53]

We need to refactor a bunch of this logic, but in the meantime, let's make
absolutely sure that we're always under the setuid sandbox in nonsfi mode.

const bool setuid_sandbox_enabled = IsSandboxed();
if (uses_nonsfi) CHECK(setuid_sandbox_enabled);

[hamaji, 2014/03/24 15:56:37]

Done. However, this essentially disables --no-sandbox option. We want to use BMM
mode + no sandbox mode for our internal development and deprecate our trusted
plugin mode. So, we'd like to have a way to disable sandbox even on non-SFI
NaCl.

Does this make sense to add an environment variable like
NACL_DANGEROUS_NO_SANDBOX_ON_NONSFI_MODE and disable sandbox only when both
--no-sandbox and NACL_DANGEROUS_NO_SANDBOX_ON_NONSFI_MODE are specified, for
example?

   if (IGNORE_EINTR(close(kNaClZygoteDescriptor)) != 0)
     LOG(ERROR) << "close(kNaClZygoteDescriptor) failed.";
-  bool sandbox_initialized = InitializeBPFSandbox();
+  bool sandbox_initialized = false;

[jln (very slow on Chromium), 2014/03/20 00:54:53]

rename to bpf_sandbox_initialized.

[hamaji, 2014/03/24 15:56:37]

Done.

+  if (uses_nonsfi)
+    sandbox_initialized = InitializeBPFSandboxForNonSfi();
+  else
+    sandbox_initialized = InitializeBPFSandbox();
   if (!sandbox_initialized) {
     LOG(ERROR) << "Could not initialize NaCl's second "
       << "layer sandbox (seccomp-bpf).";
+    // We really depend on seccomp sandbox for non-SFI mode. We do not
+    // run any program without seccomp sandbox.
+    if (uses_nonsfi)
+      _exit(1);
   }
   base::GlobalDescriptors::GetInstance()->Set(
       kPrimaryIPCChannel,
@@ -71,7 +80,8 @@ void BecomeNaClLoader(const std::vector<int>& child_fds,
 
 // Start the NaCl loader in a child created by the NaCl loader Zygote.
 void ChildNaClLoaderInit(const std::vector<int>& child_fds,
-                         const NaClLoaderSystemInfo& system_info) {
+                         const NaClLoaderSystemInfo& system_info,
+                         bool uses_nonsfi) {
   const int parent_fd = child_fds[content::ZygoteForkDelegate::kParentFDIndex];
   const int dummy_fd = child_fds[content::ZygoteForkDelegate::kDummyFDIndex];
   bool validack = false;
@@ -103,7 +113,7 @@ void ChildNaClLoaderInit(const std::vector<int>& child_fds,
   if (IGNORE_EINTR(close(parent_fd)) != 0)
     LOG(ERROR) << "close(parent_fd) failed";
   if (validack) {
-    BecomeNaClLoader(child_fds, system_info);
+    BecomeNaClLoader(child_fds, system_info, uses_nonsfi);
   } else {
     LOG(ERROR) << "Failed to synch with zygote";
   }
@@ -115,7 +125,14 @@ void ChildNaClLoaderInit(const std::vector<int>& child_fds,
 // content/browser/zygote_main_linux.cc:ForkWithRealPid()
 bool HandleForkRequest(const std::vector<int>& child_fds,
                        const NaClLoaderSystemInfo& system_info,
+                       PickleIterator* input_iter,
                        Pickle* output_pickle) {
+  bool uses_nonsfi;
+  if (!input_iter->ReadBool(&uses_nonsfi)) {
+    LOG(ERROR) << "Could not read uses_nonsfi status";
+    return false;
+  }
+
   if (content::ZygoteForkDelegate::kNumPassedFDs != child_fds.size()) {
     LOG(ERROR) << "nacl_helper: unexpected number of fds, got "
         << child_fds.size();
@@ -129,7 +146,7 @@ bool HandleForkRequest(const std::vector<int>& child_fds,
   }
 
   if (child_pid == 0) {
-    ChildNaClLoaderInit(child_fds, system_info);
+    ChildNaClLoaderInit(child_fds, system_info, uses_nonsfi);
     NOTREACHED();
   }
 
@@ -201,6 +218,7 @@ bool HonorRequestAndReply(int reply_fd,
   switch (command_type) {
     case nacl::kNaClForkRequest:
       have_to_reply = HandleForkRequest(attached_fds, system_info,
+                                        input_iter,
                                         &write_pickle);
       break;
     case nacl::kNaClGetTerminationStatusRequest: