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/*
* Copyright (C) 2019 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <android-base/cmsg.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/user.h>
#include <memory>
#include <android-base/logging.h>
namespace android {
namespace base {
ssize_t SendFileDescriptorVector(borrowed_fd sockfd, const void* data, size_t len,
const std::vector<int>& fds) {
size_t cmsg_space = CMSG_SPACE(sizeof(int) * fds.size());
size_t cmsg_len = CMSG_LEN(sizeof(int) * fds.size());
size_t pagesize = static_cast<size_t>(sysconf(_SC_PAGE_SIZE));
if (cmsg_space >= pagesize) {
errno = ENOMEM;
return -1;
}
alignas(struct cmsghdr) char cmsg_buf[cmsg_space];
iovec iov = {.iov_base = const_cast<void*>(data), .iov_len = len};
msghdr msg = {
.msg_name = nullptr,
.msg_namelen = 0,
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = cmsg_buf,
// We can't cast to the actual type of the field, because it's different across platforms.
.msg_controllen = static_cast<unsigned int>(cmsg_space),
.msg_flags = 0,
};
struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
cmsg->cmsg_len = cmsg_len;
int* cmsg_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
for (size_t i = 0; i < fds.size(); ++i) {
cmsg_fds[i] = fds[i];
}
#if defined(__linux__)
int flags = MSG_NOSIGNAL;
#else
int flags = 0;
#endif
return TEMP_FAILURE_RETRY(sendmsg(sockfd.get(), &msg, flags));
}
ssize_t ReceiveFileDescriptorVector(borrowed_fd sockfd, void* data, size_t len, size_t max_fds,
std::vector<unique_fd>* fds) {
fds->clear();
size_t cmsg_space = CMSG_SPACE(sizeof(int) * max_fds);
size_t pagesize = static_cast<size_t>(sysconf(_SC_PAGE_SIZE));
if (cmsg_space >= pagesize) {
errno = ENOMEM;
return -1;
}
alignas(struct cmsghdr) char cmsg_buf[cmsg_space];
iovec iov = {.iov_base = const_cast<void*>(data), .iov_len = len};
msghdr msg = {
.msg_name = nullptr,
.msg_namelen = 0,
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = cmsg_buf,
// We can't cast to the actual type of the field, because it's different across platforms.
.msg_controllen = static_cast<unsigned int>(cmsg_space),
.msg_flags = 0,
};
int flags = MSG_TRUNC | MSG_CTRUNC;
#if defined(__linux__)
flags |= MSG_CMSG_CLOEXEC | MSG_NOSIGNAL;
#endif
ssize_t rc = TEMP_FAILURE_RETRY(recvmsg(sockfd.get(), &msg, flags));
if (rc == -1) {
return -1;
}
int error = 0;
if ((msg.msg_flags & MSG_TRUNC)) {
LOG(ERROR) << "message was truncated when receiving file descriptors";
error = EMSGSIZE;
} else if ((msg.msg_flags & MSG_CTRUNC)) {
LOG(ERROR) << "control message was truncated when receiving file descriptors";
error = EMSGSIZE;
}
std::vector<unique_fd> received_fds;
struct cmsghdr* cmsg;
for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != nullptr; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
if (cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS) {
LOG(ERROR) << "received unexpected cmsg: [" << cmsg->cmsg_level << ", " << cmsg->cmsg_type
<< "]";
error = EBADMSG;
continue;
}
// There isn't a macro that does the inverse of CMSG_LEN, so hack around it ourselves, with
// some asserts to ensure that CMSG_LEN behaves as we expect.
#if defined(__linux__)
#define CMSG_ASSERT static_assert
#else
// CMSG_LEN is somehow not constexpr on darwin.
#define CMSG_ASSERT CHECK
#endif
CMSG_ASSERT(CMSG_LEN(0) + 1 * sizeof(int) == CMSG_LEN(1 * sizeof(int)));
CMSG_ASSERT(CMSG_LEN(0) + 2 * sizeof(int) == CMSG_LEN(2 * sizeof(int)));
CMSG_ASSERT(CMSG_LEN(0) + 3 * sizeof(int) == CMSG_LEN(3 * sizeof(int)));
CMSG_ASSERT(CMSG_LEN(0) + 4 * sizeof(int) == CMSG_LEN(4 * sizeof(int)));
if (cmsg->cmsg_len % sizeof(int) != 0) {
LOG(FATAL) << "cmsg_len(" << cmsg->cmsg_len << ") not aligned to sizeof(int)";
} else if (cmsg->cmsg_len <= CMSG_LEN(0)) {
LOG(FATAL) << "cmsg_len(" << cmsg->cmsg_len << ") not long enough to hold any data";
}
int* cmsg_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
size_t cmsg_fdcount = static_cast<size_t>(cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
for (size_t i = 0; i < cmsg_fdcount; ++i) {
#if !defined(__linux__)
// Linux uses MSG_CMSG_CLOEXEC instead of doing this manually.
fcntl(cmsg_fds[i], F_SETFD, FD_CLOEXEC);
#endif
received_fds.emplace_back(cmsg_fds[i]);
}
}
if (error != 0) {
errno = error;
return -1;
}
if (received_fds.size() > max_fds) {
LOG(ERROR) << "received too many file descriptors, expected " << fds->size() << ", received "
<< received_fds.size();
errno = EMSGSIZE;
return -1;
}
*fds = std::move(received_fds);
return rc;
}
} // namespace base
} // namespace android
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