aboutsummaryrefslogtreecommitdiffstatshomepage
path: root/contrib/nat-hole-punching/nat-punch-client.c
blob: a72b5f614bd9a0c83ea15fffd6f915483ce8eb2b (plain) (blame)
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
/* Example only. Do not run in production. */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/udp.h>
#include <netinet/ip.h>
#include <linux/filter.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdarg.h>
#include <string.h>
#include <resolv.h>
#include <stdint.h>
#include <stdbool.h>

enum { MAX_PEERS = 65536, PORT = 49918 };

static struct {
	uint8_t base64_key[45];
	bool have_seen;
} peers[MAX_PEERS];
static unsigned int total_peers;

static const char *cmd(const char *line, ...)
{
	static char buf[2048];
	char full_cmd[2048] = { 0 };
	size_t len;
	FILE *f;
	va_list args;
	va_start(args, line);
	vsnprintf(full_cmd, 2047, line, args);
	va_end(args);
	f = popen(full_cmd, "r");
	if (!f) {
		perror("popen");
		exit(errno);
	}
	if (!fgets(buf, 2048, f)) {
		pclose(f);
		return NULL;
	}
	pclose(f);
	len = strlen(buf);
	if (!len)
		return NULL;
	if (buf[len - 1] == '\n')
		buf[len - 1] = '\0';
	return buf;
}

static void read_peers(const char *interface)
{
	char full_cmd[2048] = { 0 };
	size_t len;
	FILE *f;
	snprintf(full_cmd, 2047, "wg show %s peers", interface);
	f = popen(full_cmd, "r");
	if (!f) {
		perror("popen");
		exit(errno);
	}
	for (;;) {
		if (!fgets(peers[total_peers].base64_key, 45, f))
			break;
		len = strlen(peers[total_peers].base64_key);
		if (len != 44 && len != 45)
			continue;
		if (peers[total_peers].base64_key[len - 1] == '\n')
			peers[total_peers].base64_key[len - 1] = '\0';
		++total_peers;
	}
	pclose(f);
}

static void unbase64(uint8_t dstkey[32], const char *srckey)
{
	uint8_t buf[33];
	if (b64_pton(srckey, buf, 33) != 32) {
		fprintf(stderr, "Could not parse base64 key: %s\n", srckey);
		exit(EINVAL);
	}
	memcpy(dstkey, buf, 32);
}

static void apply_bpf(int sock, uint16_t port, uint32_t ip)
{
	struct sock_filter filter[] = {
		BPF_STMT(BPF_LD + BPF_W + BPF_ABS, 12 /* src ip */),
		BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ip, 0, 5),
		BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20 /* src port */),
		BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, PORT, 0, 3),
		BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 22 /* dst port */),
		BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, port, 0, 1),
		BPF_STMT(BPF_RET + BPF_K, -1),
		BPF_STMT(BPF_RET + BPF_K, 0)
	};
	struct sock_fprog filter_prog = {
		.len = sizeof(filter) / sizeof(filter[0]),
		.filter = filter
	};
	if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog, sizeof(filter_prog)) < 0) {
		perror("setsockopt(bpf)");
		exit(errno);
	}
}

int main(int argc, char *argv[])
{
	struct sockaddr_in addr = {
		.sin_family = AF_INET
	};
	struct {
		struct udphdr udp;
		uint8_t my_pubkey[32];
		uint8_t their_pubkey[32];
	} __attribute__((packed)) packet = {
		.udp = {
			.len = htons(sizeof(packet)),
			.dest = htons(PORT)
		}
	};
	struct {
		struct iphdr iphdr;
		struct udphdr udp;
		uint32_t ip;
		uint16_t port;
	} __attribute__((packed)) reply;
	ssize_t len;
	int sock, i;
	bool repeat;
	struct hostent *ent;
	const char *server = argv[1], *interface = argv[2];

	if (argc < 3) {
		fprintf(stderr, "Usage: %s SERVER WIREGUARD_INTERFACE\nExample:\n    %s demo.wireguard.io wg0\n", argv[0], argv[0]);
		return EINVAL;
	}

	if (getuid() != 0) {
		fprintf(stderr, "Must be root!\n");
		return EPERM;
	}

	ent = gethostbyname2(server, AF_INET);
	if (!ent) {
		herror("gethostbyname2");
		return h_errno;
	}
	addr.sin_addr = *(struct in_addr *)ent->h_addr;
	read_peers(interface);
	cmd("ip link set %s up", interface);
	unbase64(packet.my_pubkey, cmd("wg show %s public-key", interface));
	packet.udp.source = htons(atoi(cmd("wg show %s listen-port", interface)));

	/* We use raw sockets so that the WireGuard interface can actually own the real socket. */
	sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
	if (sock < 0) {
		perror("socket");
		return errno;
	}
	apply_bpf(sock, ntohs(packet.udp.source), ntohl(addr.sin_addr.s_addr));

check_again:
	repeat = false;
	for (i = 0; i < total_peers; ++i) {
		if (peers[i].have_seen)
			continue;
		printf("[+] Requesting IP and port of %s: ", peers[i].base64_key);
		unbase64(packet.their_pubkey, peers[i].base64_key);
		if (sendto(sock, &packet, sizeof(packet), 0, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
			putchar('\n');
			perror("sendto");
			return errno;
		}
		len = recv(sock, &reply, sizeof(reply), 0);
		if (len < 0) {
			putchar('\n');
			perror("recv");
			return errno;
		}
		if (len != sizeof(reply)) {
			printf("server does not yet have it\n");
			repeat = true;
		} else {
			printf("%s:%d\n", inet_ntoa(*(struct in_addr *)&reply.ip), ntohs(reply.port));
			peers[i].have_seen = true;
			cmd("wg set %s peer %s persistent-keepalive 25 endpoint %s:%d", interface, peers[i].base64_key, inet_ntoa(*(struct in_addr *)&reply.ip), ntohs(reply.port));
		}
	}
	if (repeat) {
		sleep(2);
		goto check_again;
	}

	close(sock);
	return 0;
}