summaryrefslogtreecommitdiffstats
path: root/src/android_ctrl_sock.c
blob: 8be17a59b7fae4549b1d67384c9b53aaf5135274 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
/***************************************************************************
 * libancillary - black magic on Unix domain sockets
 * (C) Nicolas George
 ***************************************************************************/

/*
 * fastd Android port
 * Copyright (c) 2014-2015, Haofeng "Rick" Lei <ricklei@gmail.com>
 * All rights reserved.
 */

/*
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  1. Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/* libancillary code from:
 *   http://www.normalesup.org/~george/comp/libancillary/
 * with minor indent/style adjusts to fit fastd project
 */
/* vim: set noexpandtab ts=8 sw=8 sts=8 */

/**
   \file

   Android specific methods for communicating with GUI
*/

#ifdef __ANDROID__

#include "fastd.h"

#include <sys/un.h>


/** declare a work buffer for sending/receiving \e n handles */
#define ANCIL_FD_BUFFER(n) \
	struct { \
		struct cmsghdr h; \
		int fd[n]; \
	}

/** receive \e n_fds handles from unix domain socket \e sock and store in \e fds  */
static int ancil_recv_fds_with_buffer(int sock, int *fds, unsigned n_fds, void *buffer) {
	struct msghdr msghdr;
	char nothing;
	struct iovec nothing_ptr;
	struct cmsghdr *cmsg;
	int i;

	nothing_ptr.iov_base = &nothing;
	nothing_ptr.iov_len = 1;
	msghdr.msg_name = NULL;
	msghdr.msg_namelen = 0;
	msghdr.msg_iov = &nothing_ptr;
	msghdr.msg_iovlen = 1;
	msghdr.msg_flags = 0;
	msghdr.msg_control = buffer;
	msghdr.msg_controllen = sizeof(struct cmsghdr) + sizeof(int) * n_fds;
	cmsg = CMSG_FIRSTHDR(&msghdr);
	cmsg->cmsg_len = msghdr.msg_controllen;
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;
	for (i = 0; i < n_fds; i++) {
		((int *)CMSG_DATA(cmsg))[i] = -1;
	}

	if (recvmsg(sock, &msghdr, 0) < 0) {
		return(-1);
	}
	for (i = 0; i < n_fds; i++) {
		fds[i] = ((int *)CMSG_DATA(cmsg))[i];
	}
	n_fds = (cmsg->cmsg_len - sizeof(struct cmsghdr)) / sizeof(int);
	return n_fds;
}

/** shortcut for receiving only one \e fd from \e sock */
static int ancil_recv_fd(int sock, int *fd) {
	ANCIL_FD_BUFFER(1) buffer;

	return ancil_recv_fds_with_buffer(sock, fd, 1, &buffer) == 1 ? 0 : -1;
}

/** send \e n_fds handles in \e fds to unix domain socket \e sock */
static int ancil_send_fds_with_buffer(int sock, const int *fds, unsigned n_fds, void *buffer) {
	struct msghdr msghdr;
	char nothing = '!';
	struct iovec nothing_ptr;
	struct cmsghdr *cmsg;
	int i;

	nothing_ptr.iov_base = &nothing;
	nothing_ptr.iov_len = 1;
	msghdr.msg_name = NULL;
	msghdr.msg_namelen = 0;
	msghdr.msg_iov = &nothing_ptr;
	msghdr.msg_iovlen = 1;
	msghdr.msg_flags = 0;
	msghdr.msg_control = buffer;
	msghdr.msg_controllen = sizeof(struct cmsghdr) + sizeof(int) * n_fds;
	cmsg = CMSG_FIRSTHDR(&msghdr);
	cmsg->cmsg_len = msghdr.msg_controllen;
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;
	for (i = 0; i < n_fds; i++) {
		((int *)CMSG_DATA(cmsg))[i] = fds[i];
	}
	return sendmsg(sock, &msghdr, 0) >= 0 ? 0 : -1;
}

/** shortcut for sending only one \e fd to \e sock */
static int ancil_send_fd(int sock, int fd)
{
	ANCIL_FD_BUFFER(1) buffer;

	return ancil_send_fds_with_buffer(sock, &fd, 1, &buffer);
}

/*
 * libancillary end
 */


/** name of unix domain socket for communication with Android FastdVpnService */
#define CTRL_SOCK_NAME "fastd_tun_sock"

/** message sent by Android FastdVpnService to indicate successful protection of socket */
#define PROTECT_OK 'X'

/** message sent by Android FastdVpnService when protecting socket failed */
#define PROTECT_ERROR 'E'

/** establish the unix domain socket with Android GUI */
static void init_ctrl_sock(void) {
	/* Must keep consistent with FastdVpnService */
	struct sockaddr_un addr;

	if ((ctx.android_ctrl_sock_fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
		exit_errno("could not create unix domain socket");
	}

	memset(&addr, 0, sizeof(addr));
	addr.sun_family = AF_UNIX;
	addr.sun_path[0] = 0;     /* Linux's abstract unix domain socket name */
	strncpy(addr.sun_path + 1, CTRL_SOCK_NAME, sizeof(addr.sun_path) - 2);
	int socklen = offsetof(struct sockaddr_un, sun_path) + strlen(CTRL_SOCK_NAME) + 1;

	if (connect(ctx.android_ctrl_sock_fd, (struct sockaddr*)&addr, socklen) == -1) {
		exit_errno("could not connect to Android LocalServerSocket");
	}
}

/** receive TUN fd from Android GUI; this is the only way to open TUN device on non-rooted Android */
int fastd_android_receive_tunfd(void) {
	init_ctrl_sock();

	int handle;
	if (ancil_recv_fd(ctx.android_ctrl_sock_fd, &handle)) {
		exit_errno("could not receive TUN handle from Android");
	} else {
		pr_debug("received fd: %u", handle);
	}

	return handle;
}

/** send fastd pid to Android GUI for later signal sending (HUP, TERM etc) */
void fastd_android_send_pid(void) {
	char pid[20];
	snprintf(pid, sizeof(pid), "%u", (unsigned)getpid());
	if (write(ctx.android_ctrl_sock_fd, pid, strlen(pid)) != strlen(pid)) {
		exit_errno("send pid");
	}
}

/** report \e fd to Android GUI to be protected (i.e. not to be routed via TUN) */
bool fastd_android_protect_socket(int fd) {
	if (!conf.android_integration) {
		/* rooted/non-GUI mode */
		return true;
	}

	pr_debug("sending fd to protect");
	if (ancil_send_fd(ctx.android_ctrl_sock_fd, fd) == -1) {
		exit_errno("could not send handle to Android for protecting");
	}

	char buf[20];
	if (read(ctx.android_ctrl_sock_fd, buf, sizeof(buf)) == -1) {
		exit_errno("read ack");
	}
	return buf[0] == PROTECT_OK;
}

#endif /* __ANDROID__ */