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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "SandboxBrokerCommon.h"
#include "mozilla/Assertions.h"
// This file is built both within libxul and as a separate libmozsandbox
// library. We can only use profiler annotations within libxul.
#ifdef MOZILLA_INTERNAL_API
# include "mozilla/ProfilerThreadSleep.h"
#else
# define AUTO_PROFILER_THREAD_SLEEP
#endif
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#ifndef MSG_CMSG_CLOEXEC
# ifdef XP_LINUX
// As always, Android's kernel headers are somewhat old.
# define MSG_CMSG_CLOEXEC 0x40000000
# else
// Most of this code can support other POSIX OSes, but being able to
// receive fds and atomically make them close-on-exec is important,
// because this is running in a multithreaded process that can fork.
// In the future, if the broker becomes a dedicated executable, this
// can change.
# error "No MSG_CMSG_CLOEXEC?"
# endif // XP_LINUX
#endif // MSG_CMSG_CLOEXEC
namespace mozilla {
const char* SandboxBrokerCommon::OperationDescription[] = {
"open",
"access",
"stat",
"chmod",
"link",
"symlink",
"mkdir",
"rename",
"rmdir",
"unlink",
"readlink",
"connect",
"connect-abstract",
};
/* static */
ssize_t SandboxBrokerCommon::RecvWithFd(int aFd, const iovec* aIO,
size_t aNumIO, int* aPassedFdPtr) {
struct msghdr msg = {};
msg.msg_iov = const_cast<iovec*>(aIO);
msg.msg_iovlen = aNumIO;
char cmsg_buf[CMSG_SPACE(sizeof(int))];
if (aPassedFdPtr) {
msg.msg_control = cmsg_buf;
msg.msg_controllen = sizeof(cmsg_buf);
*aPassedFdPtr = -1;
}
ssize_t rv;
do {
// MSG_CMSG_CLOEXEC is needed to prevent the parent process from
// accidentally leaking a copy of the child's response socket to a
// new child process. (The child won't be able to exec, so this
// doesn't matter as much for that direction.)
AUTO_PROFILER_THREAD_SLEEP;
rv = recvmsg(aFd, &msg, MSG_CMSG_CLOEXEC);
} while (rv < 0 && errno == EINTR);
if (rv <= 0) {
return rv;
}
if (msg.msg_controllen > 0) {
MOZ_ASSERT(aPassedFdPtr);
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
int* fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
if (cmsg->cmsg_len != CMSG_LEN(sizeof(int))) {
// A client could, for example, send an extra 32-bit int if
// CMSG_SPACE pads to 64-bit size_t alignment. If so, treat
// it as an error, but also don't leak the fds.
for (size_t i = 0; CMSG_LEN(sizeof(int) * i) < cmsg->cmsg_len; ++i) {
close(fds[i]);
}
// In theory, the kernel should delete the message instead of
// giving us an empty one, if errors prevent transferring the
// fd.
MOZ_DIAGNOSTIC_ASSERT(cmsg->cmsg_len != 0);
errno = EMSGSIZE;
return -1;
}
*aPassedFdPtr = fds[0];
} else {
errno = EPROTO;
return -1;
}
}
if (msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC)) {
if (aPassedFdPtr && *aPassedFdPtr >= 0) {
close(*aPassedFdPtr);
*aPassedFdPtr = -1;
}
// MSG_CTRUNC usually means the fd was dropped due to fd
// exhaustion in the receiving process, so map that to `EMFILE`.
// MSG_TRUNC (truncation of the data part) shouldn't ever happen.
// (If the sender is malicious it can send too many bytes or fds,
// but this is about getting an accurate error message in genuine
// error cases.)
MOZ_DIAGNOSTIC_ASSERT((msg.msg_flags & MSG_TRUNC) == 0);
errno = EMFILE;
return -1;
}
return rv;
}
/* static */
ssize_t SandboxBrokerCommon::SendWithFd(int aFd, const iovec* aIO,
size_t aNumIO, int aPassedFd) {
struct msghdr msg = {};
msg.msg_iov = const_cast<iovec*>(aIO);
msg.msg_iovlen = aNumIO;
char cmsg_buf[CMSG_SPACE(sizeof(int))];
memset(cmsg_buf, 0, sizeof(cmsg_buf));
if (aPassedFd != -1) {
msg.msg_control = cmsg_buf;
msg.msg_controllen = sizeof(cmsg_buf);
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = CMSG_LEN(sizeof(int));
*reinterpret_cast<int*>(CMSG_DATA(cmsg)) = aPassedFd;
}
ssize_t rv;
do {
rv = sendmsg(aFd, &msg, MSG_NOSIGNAL);
} while (rv < 0 && errno == EINTR);
return rv;
}
} // namespace mozilla
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