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// Copyright (c) 2011 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.
// A mini-zygote specifically for Native Client.
#include "chrome/common/nacl_helper_linux.h"
#include <errno.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <string>
#include <vector>
#include "base/at_exit.h"
#include "base/eintr_wrapper.h"
#include "base/logging.h"
#include "base/message_loop.h"
#include "base/rand_util.h"
#include "chrome/nacl/nacl_listener.h"
#include "content/common/main_function_params.h"
#include "content/common/unix_domain_socket_posix.h"
#include "ipc/ipc_switches.h"
namespace {
bool g_suid_sandbox_active;
// The child must mimic the behavior of zygote_main_linux.cc on the child
// side of the fork. See zygote_main_linux.cc:HandleForkRequest from
// if (!child) {
// Note: this code doesn't attempt to support SELINUX or the SECCOMP sandbox.
void BecomeNaClLoader(const std::vector<int>& child_fds) {
VLOG(1) << "NaCl loader: setting up IPC descriptor";
// don't need zygote FD any more
if (HANDLE_EINTR(close(kNaClZygoteDescriptor)) != 0)
LOG(ERROR) << "close(kNaClZygoteDescriptor) failed.";
// Set up browser descriptor as expected by Chrome on fd 3
// The zygote takes care of putting the sandbox IPC channel on fd 5
int zfd = dup2(child_fds[kNaClBrowserFDIndex], kNaClBrowserDescriptor);
if (zfd != kNaClBrowserDescriptor) {
LOG(ERROR) << "Could not initialize kNaClBrowserDescriptor";
_exit(-1);
}
MessageLoopForIO main_message_loop;
NaClListener *listener = new NaClListener();
listener->Listen();
_exit(0);
}
// Some of this code was lifted from
// content/browser/zygote_main_linux.cc:ForkWithRealPid()
void HandleForkRequest(const std::vector<int>& child_fds) {
VLOG(1) << "nacl_helper: forking";
pid_t childpid = fork();
if (childpid < 0) {
perror("fork");
LOG(ERROR) << "*** HandleForkRequest failed\n";
// fall through to parent case below
} else if (childpid == 0) { // In the child process.
bool validack = false;
const size_t kMaxReadSize = 1024;
char buffer[kMaxReadSize];
// Wait until the parent process has discovered our PID. We
// should not fork any child processes (which the seccomp
// sandbox does) until then, because that can interfere with the
// parent's discovery of our PID.
const int nread = HANDLE_EINTR(read(child_fds[kNaClParentFDIndex], buffer,
kMaxReadSize));
const std::string switch_prefix = std::string("--") +
switches::kProcessChannelID + std::string("=");
const size_t len = switch_prefix.length();
if (nread < 0) {
perror("read");
LOG(ERROR) << "read returned " << nread;
} else if (nread > static_cast<int>(len)) {
if (switch_prefix.compare(0, len, buffer, 0, len) == 0) {
VLOG(1) << "NaCl loader is synchronised with Chrome zygote";
CommandLine::ForCurrentProcess()->AppendSwitchASCII(
switches::kProcessChannelID,
std::string(&buffer[len], nread - len));
validack = true;
}
}
if (HANDLE_EINTR(close(child_fds[kNaClDummyFDIndex])) != 0)
LOG(ERROR) << "close(child_fds[kNaClDummyFDIndex]) failed";
if (HANDLE_EINTR(close(child_fds[kNaClParentFDIndex])) != 0)
LOG(ERROR) << "close(child_fds[kNaClParentFDIndex]) failed";
if (validack) {
BecomeNaClLoader(child_fds);
} else {
LOG(ERROR) << "Failed to synch with zygote";
}
// NOTREACHED
return;
}
// I am the parent.
// First, close the dummy_fd so the sandbox won't find me when
// looking for the child's pid in /proc. Also close other fds.
for (size_t i = 0; i < child_fds.size(); i++) {
if (HANDLE_EINTR(close(child_fds[i])) != 0)
LOG(ERROR) << "close(child_fds[i]) failed";
}
VLOG(1) << "nacl_helper: childpid is " << childpid;
// Now tell childpid to the Chrome zygote.
if (HANDLE_EINTR(send(kNaClZygoteDescriptor,
&childpid, sizeof(childpid), MSG_EOR))
!= sizeof(childpid)) {
LOG(ERROR) << "*** send() to zygote failed";
}
}
} // namespace
static const void* g_nacl_reserved_space = NULL;
extern "C" __attribute__((visibility("default")))
const void* nacl_helper_get_1G_address() {
return g_nacl_reserved_space;
}
// nacl_helper_init does the real work of this module. It is invoked as
// a static constructor and never returns, preventing main() from the
// nacl_helper_bootstrap program from being called.
//
// NOTE This routine must not return.
extern "C" __attribute__((visibility("default")))
void nacl_helper_init(int argc, char *argv[],
const char *nacl_reserved_space) {
CommandLine::Init(argc, argv);
base::AtExitManager exit_manager;
base::RandUint64(); // acquire /dev/urandom fd before sandbox is raised
std::vector<int> empty; // for SendMsg() calls
g_suid_sandbox_active = (NULL != getenv("SBX_D"));
g_nacl_reserved_space = nacl_reserved_space;
if (!nacl_reserved_space) {
VLOG(1) << "nacl_reserved_space is NULL";
} else {
VLOG(1) << "nacl_reserved_space is at "
<< (void *)nacl_reserved_space;
}
// Send the zygote a message to let it know we are ready to help
if (!UnixDomainSocket::SendMsg(kNaClZygoteDescriptor,
kNaClHelperStartupAck,
sizeof(kNaClHelperStartupAck), empty)) {
LOG(ERROR) << "*** send() to zygote failed";
}
while (true) {
int badpid = -1;
std::vector<int> fds;
static const unsigned kMaxMessageLength = 2048;
char buf[kMaxMessageLength];
const ssize_t msglen = UnixDomainSocket::RecvMsg(kNaClZygoteDescriptor,
&buf, sizeof(buf), &fds);
if (msglen == 0 || (msglen == -1 && errno == ECONNRESET)) {
// EOF from the browser. Goodbye!
_exit(0);
}
if (msglen == sizeof(kNaClForkRequest) - 1 &&
memcmp(buf, kNaClForkRequest, msglen) == 0) {
if (kNaClParentFDIndex + 1 == fds.size()) {
HandleForkRequest(fds);
continue; // fork succeeded. Note: child does not return
} else {
LOG(ERROR) << "nacl_helper: unexpected number of fds, got "
<< fds.size();
}
} else {
if (msglen != 0) {
LOG(ERROR) << "nacl_helper unrecognized request: %s";
_exit(-1);
}
}
// if fork fails, send PID=-1 to zygote
if (!UnixDomainSocket::SendMsg(kNaClZygoteDescriptor, &badpid,
sizeof(badpid), empty)) {
LOG(ERROR) << "*** send() to zygote failed";
}
}
CHECK(false); // This routine must not return
}
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