1 /*
2  * Copyright (C) 2016 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 <errno.h>
18 #include <string.h>
19 
20 #include "LeakPipe.h"
21 
22 #include "log.h"
23 
24 namespace android {
25 
26 bool LeakPipe::SendFd(int sock, int fd) {
27   struct msghdr hdr {};
28   struct iovec iov {};
29   unsigned int data = 0xfdfdfdfd;
30   alignas(struct cmsghdr) char cmsgbuf[CMSG_SPACE(sizeof(int))];
31 
32   hdr.msg_iov = &iov;
33   hdr.msg_iovlen = 1;
34   iov.iov_base = &data;
35   iov.iov_len = sizeof(data);
36 
37   hdr.msg_control = cmsgbuf;
38   hdr.msg_controllen = CMSG_LEN(sizeof(int));
39 
40   struct cmsghdr* cmsg = CMSG_FIRSTHDR(&hdr);
41   cmsg->cmsg_len = CMSG_LEN(sizeof(int));
42   cmsg->cmsg_level = SOL_SOCKET;
43   cmsg->cmsg_type = SCM_RIGHTS;
44 
45   *(int*)CMSG_DATA(cmsg) = fd;
46 
47   int ret = sendmsg(sock, &hdr, 0);
48   if (ret < 0) {
49     MEM_ALOGE("failed to send fd: %s", strerror(errno));
50     return false;
51   }
52   if (ret == 0) {
53     MEM_ALOGE("eof when sending fd");
54     return false;
55   }
56 
57   return true;
58 }
59 
60 int LeakPipe::ReceiveFd(int sock) {
61   struct msghdr hdr {};
62   struct iovec iov {};
63   unsigned int data;
64   alignas(struct cmsghdr) char cmsgbuf[CMSG_SPACE(sizeof(int))];
65 
66   hdr.msg_iov = &iov;
67   hdr.msg_iovlen = 1;
68   iov.iov_base = &data;
69   iov.iov_len = sizeof(data);
70 
71   hdr.msg_control = cmsgbuf;
72   hdr.msg_controllen = CMSG_LEN(sizeof(int));
73 
74   int ret = recvmsg(sock, &hdr, 0);
75   if (ret < 0) {
76     MEM_ALOGE("failed to receive fd: %s", strerror(errno));
77     return -1;
78   }
79   if (ret == 0) {
80     MEM_ALOGE("eof when receiving fd");
81     return -1;
82   }
83 
84   struct cmsghdr* cmsg = CMSG_FIRSTHDR(&hdr);
85   if (cmsg == NULL || cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS) {
86     MEM_ALOGE("missing fd while receiving fd");
87     return -1;
88   }
89 
90   return *(int*)CMSG_DATA(cmsg);
91 }
92 
93 }  // namespace android
94