blob: 1879d447318846f1950d7bad0ea57861d86a290e [file] [log] [blame]
Josh Gao14f95002019-01-07 19:16:21 -08001/*
2 * Copyright (C) 2019 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <android-base/cmsg.h>
18
19#include <alloca.h>
20#include <errno.h>
21#include <malloc.h>
22#include <stdlib.h>
23#include <sys/socket.h>
24#include <sys/user.h>
25
26#include <memory>
27
28#include <android-base/logging.h>
29
30namespace android {
31namespace base {
32
33ssize_t SendFileDescriptorVector(int sockfd, const void* data, size_t len,
34 const std::vector<int>& fds) {
35 size_t cmsg_space = CMSG_SPACE(sizeof(int) * fds.size());
36 size_t cmsg_len = CMSG_LEN(sizeof(int) * fds.size());
37 if (cmsg_space >= PAGE_SIZE) {
38 errno = ENOMEM;
39 return -1;
40 }
41
42 alignas(struct cmsghdr) char cmsg_buf[cmsg_space];
43 iovec iov = {.iov_base = const_cast<void*>(data), .iov_len = len};
44 msghdr msg = {
45 .msg_name = nullptr,
46 .msg_namelen = 0,
47 .msg_iov = &iov,
48 .msg_iovlen = 1,
49 .msg_control = cmsg_buf,
50 .msg_controllen = cmsg_space,
51 .msg_flags = 0,
52 };
53
54 struct cmsghdr* cmsg = CMSG_FIRSTHDR(&msg);
55 cmsg->cmsg_level = SOL_SOCKET;
56 cmsg->cmsg_type = SCM_RIGHTS;
57 cmsg->cmsg_len = cmsg_len;
58
59 int* cmsg_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
60 for (size_t i = 0; i < fds.size(); ++i) {
61 cmsg_fds[i] = fds[i];
62 }
63
64 return TEMP_FAILURE_RETRY(sendmsg(sockfd, &msg, MSG_NOSIGNAL));
65}
66
67ssize_t ReceiveFileDescriptorVector(int sockfd, void* data, size_t len, size_t max_fds,
68 std::vector<unique_fd>* fds) {
69 fds->clear();
70
71 size_t cmsg_space = CMSG_SPACE(sizeof(int) * max_fds);
72 if (cmsg_space >= PAGE_SIZE) {
73 errno = ENOMEM;
74 return -1;
75 }
76
77 alignas(struct cmsghdr) char cmsg_buf[cmsg_space];
78 iovec iov = {.iov_base = const_cast<void*>(data), .iov_len = len};
79 msghdr msg = {
80 .msg_name = nullptr,
81 .msg_namelen = 0,
82 .msg_iov = &iov,
83 .msg_iovlen = 1,
84 .msg_control = cmsg_buf,
85 .msg_controllen = cmsg_space,
86 .msg_flags = 0,
87 };
88
89 ssize_t rc = TEMP_FAILURE_RETRY(
90 recvmsg(sockfd, &msg, MSG_TRUNC | MSG_CTRUNC | MSG_CMSG_CLOEXEC | MSG_NOSIGNAL));
91 if (rc == -1) {
92 return -1;
93 }
94
95 int error = 0;
96 if ((msg.msg_flags & MSG_TRUNC)) {
97 LOG(ERROR) << "message was truncated when receiving file descriptors";
98 error = EMSGSIZE;
99 } else if ((msg.msg_flags & MSG_CTRUNC)) {
100 LOG(ERROR) << "control message was truncated when receiving file descriptors";
101 error = EMSGSIZE;
102 }
103
104 std::vector<unique_fd> received_fds;
105 struct cmsghdr* cmsg;
106 for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != nullptr; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
107 if (cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS) {
108 LOG(ERROR) << "received unexpected cmsg: [" << cmsg->cmsg_level << ", " << cmsg->cmsg_type
109 << "]";
110 error = EBADMSG;
111 continue;
112 }
113
114 // There isn't a macro that does the inverse of CMSG_LEN, so hack around it ourselves, with
115 // some static asserts to ensure that CMSG_LEN behaves as we expect.
116 static_assert(CMSG_LEN(0) + 1 * sizeof(int) == CMSG_LEN(1 * sizeof(int)));
117 static_assert(CMSG_LEN(0) + 2 * sizeof(int) == CMSG_LEN(2 * sizeof(int)));
118 static_assert(CMSG_LEN(0) + 3 * sizeof(int) == CMSG_LEN(3 * sizeof(int)));
119 static_assert(CMSG_LEN(0) + 4 * sizeof(int) == CMSG_LEN(4 * sizeof(int)));
120
121 if (cmsg->cmsg_len % sizeof(int) != 0) {
122 LOG(FATAL) << "cmsg_len(" << cmsg->cmsg_len << ") not aligned to sizeof(int)";
123 } else if (cmsg->cmsg_len <= CMSG_LEN(0)) {
124 LOG(FATAL) << "cmsg_len(" << cmsg->cmsg_len << ") not long enough to hold any data";
125 }
126
127 int* cmsg_fds = reinterpret_cast<int*>(CMSG_DATA(cmsg));
128 size_t cmsg_fdcount = static_cast<size_t>(cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int);
129 for (size_t i = 0; i < cmsg_fdcount; ++i) {
130 received_fds.emplace_back(cmsg_fds[i]);
131 }
132 }
133
134 if (error != 0) {
135 errno = error;
136 return -1;
137 }
138
139 if (received_fds.size() > max_fds) {
140 LOG(ERROR) << "received too many file descriptors, expected " << fds->size() << ", received "
141 << received_fds.size();
142 errno = EMSGSIZE;
143 return -1;
144 }
145
146 *fds = std::move(received_fds);
147 return rc;
148}
149
150} // namespace base
151} // namespace android