wg-quick: add android implementation

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/src/wg-quick/android.c b/src/wg-quick/android.c
new file mode 100644 (file)
index 0000000..25f8f5f
--- /dev/null
+++ b/src/wg-quick/android.c
@@ -0,0 +1,666 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2015-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This is a shell script written in C. It very intentionally still functions like
+ * a shell script, calling out to external executables such as ip(8).
+ */
+
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include <strings.h>
+#include <stdarg.h>
+#include <ctype.h>
+#include <time.h>
+#include <unistd.h>
+#include <errno.h>
+#include <regex.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <sys/param.h>
+
+#ifndef WG_CONFIG_SEARCH_PATHS
+#define WG_CONFIG_SEARCH_PATHS "/data/misc/wireguard /data/data/com.wireguard.android/files"
+#endif
+
+#define _printf_(x, y) __attribute__((format(printf, x, y)))
+#define _cleanup_(x) __attribute__((cleanup(x)))
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
+
+static bool is_exiting = false;
+
+static void *xmalloc(size_t size)
+{
+       void *ret = malloc(size);
+       if (ret)
+               return ret;
+       perror("Error: malloc");
+       exit(errno);
+}
+
+static void *xstrdup(const char *str)
+{
+       char *ret = strdup(str);
+       if (ret)
+               return ret;
+       perror("Error: strdup");
+       exit(errno);
+}
+
+static void xregcomp(regex_t *preg, const char *regex, int cflags)
+{
+       if (regcomp(preg, regex, cflags)) {
+               fprintf(stderr, "Error: Regex compilation error\n");
+               exit(EBADR);
+       }
+}
+
+static char *concat(char *first, ...)
+{
+       va_list args;
+       size_t len = 0;
+       char *ret;
+
+       va_start(args, first);
+       for (char *i = first; i; i = va_arg(args, char *))
+               len += strlen(i);
+       va_end(args);
+
+       ret = xmalloc(len + 1);
+       ret[0] = '\0';
+
+       va_start(args, first);
+       for (char *i = first; i; i = va_arg(args, char *))
+               strcat(ret, i);
+       va_end(args);
+
+       return ret;
+}
+
+static char *concat_and_free(char *orig, const char *delim, const char *new_line)
+{
+       char *ret;
+
+       if (!orig)
+               ret = xstrdup(new_line);
+       else
+               ret = concat(orig, delim, new_line, NULL);
+       free(orig);
+       return ret;
+}
+
+struct command_buffer {
+       char *line;
+       size_t len;
+       FILE *stream;
+};
+
+static void free_command_buffer(struct command_buffer *c)
+{
+       if (!c)
+               return;
+       if (c->stream)
+               pclose(c->stream);
+       free(c->line);
+}
+
+static void freep(void *p)
+{
+       free(*(void **)p);
+}
+static void fclosep(FILE **f)
+{
+       if (*f)
+               fclose(*f);
+}
+#define _cleanup_free_ _cleanup_(freep)
+#define _cleanup_fclose_ _cleanup_(fclosep)
+
+#define DEFINE_CMD(name) _cleanup_(free_command_buffer) struct command_buffer name = { 0 };
+
+static char *vcmd_ret(struct command_buffer *c, const char *cmd_fmt, va_list args)
+{
+       _cleanup_free_ char *cmd = NULL;
+
+       if (!c->stream && !cmd_fmt)
+               return NULL;
+       if (c->stream && cmd_fmt)
+               pclose(c->stream);
+
+       if (cmd_fmt) {
+               if (vasprintf(&cmd, cmd_fmt, args) < 0) {
+                       perror("Error: vasprintf");
+                       exit(errno);
+               }
+
+               c->stream = popen(cmd, "r");
+               if (!c->stream) {
+                       perror("Error: popen");
+                       exit(errno);
+               }
+       }
+       errno = 0;
+       if (getline(&c->line, &c->len, c->stream) < 0) {
+               if (errno) {
+                       perror("Error: getline");
+                       exit(errno);
+               }
+               return NULL;
+       }
+       return c->line;
+}
+
+_printf_(1, 2) static void cmd(const char *cmd_fmt, ...)
+{
+       _cleanup_free_ char *cmd = NULL;
+       va_list args;
+       int ret;
+
+       va_start(args, cmd_fmt);
+       if (vasprintf(&cmd, cmd_fmt, args) < 0) {
+               perror("Error: vasprintf");
+               exit(errno);
+       }
+       va_end(args);
+
+       printf("[#] %s\n", cmd);
+       ret = system(cmd);
+
+       if (ret < 0)
+               ret = ESRCH;
+       else if (ret > 0)
+               ret = WIFEXITED(ret) ? WEXITSTATUS(ret) : EIO;
+
+       if (ret && !is_exiting)
+               exit(ret);
+}
+
+_printf_(2, 3) static char *cmd_ret(struct command_buffer *c, const char *cmd_fmt, ...)
+{
+       va_list args;
+       char *ret;
+
+       va_start(args, cmd_fmt);
+       ret = vcmd_ret(c, cmd_fmt, args);
+       va_end(args);
+       return ret;
+}
+
+_printf_(1, 2) static void cndc(const char *cmd_fmt, ...)
+{
+       DEFINE_CMD(c);
+       int error_code;
+       char *ret;
+       va_list args;
+       _cleanup_free_ char *ndc_fmt = concat("ndc ", cmd_fmt, NULL);
+
+       va_start(args, cmd_fmt);
+       printf("[#] ");
+       vprintf(ndc_fmt, args);
+       printf("\n");
+       va_end(args);
+
+       va_start(args, cmd_fmt);
+       ret = vcmd_ret(&c, ndc_fmt, args);
+       va_end(args);
+
+       if (!ret) {
+               fprintf(stderr, "Error: could not call ndc\n");
+               exit(ENOSYS);
+       }
+
+       error_code = atoi(ret);
+       if (error_code >= 400 && error_code < 600) {
+               fprintf(stderr, "Error: %s\n", ret);
+               exit(ENONET);
+       }
+}
+
+static void auto_su(int argc, char *argv[])
+{
+       char *args[argc + 4];
+
+       if (!getuid())
+               return;
+
+       args[0] = "su";
+       args[1] = "-p";
+       args[2] = "-c";
+       memcpy(&args[3], argv, argc * sizeof(*args));
+       args[argc + 3] = NULL;
+
+       printf("[$] su -p -c ");
+       for (int i = 0; i < argc; ++i)
+               printf("%s%c", argv[i], i == argc - 1 ? '\n' : ' ');
+
+       execvp("su", args);
+       exit(errno);
+}
+
+static void add_if(const char *iface)
+{
+       cmd("ip link add %s type wireguard", iface);
+}
+
+static void del_if(const char *iface)
+{
+       DEFINE_CMD(c);
+       regex_t reg;
+       regmatch_t matches[2];
+       char *netid = NULL;
+       _cleanup_free_ char *regex = concat("0xc([0-9a-f]+)/0xcffff lookup ", iface, NULL);
+
+       xregcomp(&reg, regex, REG_EXTENDED);
+
+       cmd("ip link del %s", iface);
+       for (char *ret = cmd_ret(&c, "ip rule show"); ret; ret = cmd_ret(&c, NULL)) {
+               if (!regexec(&reg, ret, ARRAY_SIZE(matches), matches, 0)) {
+                       ret[matches[1].rm_eo] = '\0';
+                       netid = &ret[matches[1].rm_so];
+                       break;
+               }
+       }
+
+       if (netid)
+               cndc("network destroy %lu", strtoul(netid, NULL, 16));
+}
+
+static void up_if(unsigned int *netid, const char *iface)
+{
+       srandom(time(NULL) ^ getpid()); /* Not real randomness. */
+
+       while (*netid < 4096)
+               *netid = random() & 0xfffe;
+
+       cmd("wg set %s fwmark 0x20000", iface);
+       cndc("interface setcfg %s up", iface);
+       cndc("network create %u vpn 1 1", *netid);
+       cndc("network interface add %u %s", *netid, iface);
+       cndc("network users add %u 0-99999", *netid);
+}
+
+static void set_dnses(unsigned int netid, const char *dnses)
+{
+       size_t len = strlen(dnses);
+       if (len > (1<<16))
+               return;
+       _cleanup_free_ char *mutable = xstrdup(dnses);
+       _cleanup_free_ char *arglist = xmalloc(len * 4 + 1);
+       _cleanup_free_ char *arg = xmalloc(len + 4);
+
+       if (!len)
+               return;
+       arglist[0] = '\0';
+
+       for (char *dns = strtok(mutable, ", \t\n"); dns; dns = strtok(NULL, ", \t\n")) {
+               if (strchr(dns, '\'') || strchr(dns, '\\'))
+                       continue;
+               snprintf(arg, len + 3, "'%s' ", dns);
+               strncat(arglist, arg, len * 4 - 1);
+       }
+       if (!strlen(arglist))
+               return;
+       cndc("resolver setnetdns %u '' %s", netid, arglist);
+}
+
+static void add_addr(const char *iface, const char *addr)
+{
+       if (strchr(addr, ':')) {
+               cndc("interface ipv6 %s enable", iface);
+               cmd("ip -6 addr add '%s' dev %s", addr, iface);
+       } else {
+               _cleanup_free_ char *mut_addr = strdup(addr);
+               char *slash = strchr(mut_addr, '/');
+               unsigned char mask = 32;
+
+               if (slash) {
+                       *slash = '\0';
+                       mask = atoi(slash + 1);
+               }
+               cndc("interface setcfg %s '%s' %u", iface, mut_addr, mask);
+       }
+}
+
+static void set_addr(const char *iface, const char *addrs)
+{
+       _cleanup_free_ char *mutable = xstrdup(addrs);
+
+       for (char *addr = strtok(mutable, ", \t\n"); addr; addr = strtok(NULL, ", \t\n")) {
+               if (strchr(addr, '\'') || strchr(addr, '\\'))
+                       continue;
+               add_addr(iface, addr);
+       }
+}
+
+static int get_route_mtu(const char *endpoint)
+{
+       DEFINE_CMD(c_route);
+       DEFINE_CMD(c_dev);
+       regmatch_t matches[2];
+       regex_t regex_mtu, regex_dev;
+       char *route, *mtu, *dev;
+
+       xregcomp(&regex_mtu, "mtu ([0-9]+)", REG_EXTENDED);
+       xregcomp(&regex_dev, "dev ([^ ]+)", REG_EXTENDED);
+
+       if (strcmp(endpoint, "default"))
+               route = cmd_ret(&c_route, "ip -o route get %s", endpoint);
+       else
+               route = cmd_ret(&c_route, "ip -o route show %s", endpoint);
+       if (!route)
+               return -1;
+
+       if (!regexec(&regex_mtu, route, ARRAY_SIZE(matches), matches, 0)) {
+               route[matches[1].rm_eo] = '\0';
+               mtu = &route[matches[1].rm_so];
+       } else if (!regexec(&regex_dev, route, ARRAY_SIZE(matches), matches, 0)) {
+               route[matches[1].rm_eo] = '\0';
+               dev = &route[matches[1].rm_so];
+               route = cmd_ret(&c_dev, "ip -o link show dev %s", dev);
+               if (!route)
+                       return -1;
+               if (regexec(&regex_mtu, route, ARRAY_SIZE(matches), matches, 0))
+                       return -1;
+               route[matches[1].rm_eo] = '\0';
+               mtu = &route[matches[1].rm_so];
+       } else
+               return -1;
+       return atoi(mtu);
+}
+
+static void set_mtu(const char *iface, unsigned int mtu)
+{
+       DEFINE_CMD(c_endpoints);
+       regex_t regex_endpoint;
+       regmatch_t matches[2];
+       int endpoint_mtu, next_mtu;
+
+       if (mtu) {
+               cndc("interface setmtu %s %u", iface, mtu);
+               return;
+       }
+
+       xregcomp(&regex_endpoint, "^\\[?([a-z0-9:.]+)\\]?:[0-9]+$", REG_EXTENDED);
+
+       endpoint_mtu = get_route_mtu("default");
+       if (endpoint_mtu == -1)
+               endpoint_mtu = 1500;
+
+       for (char *endpoint = cmd_ret(&c_endpoints, "wg show %s endpoints", iface); endpoint; endpoint = cmd_ret(&c_endpoints, NULL)) {
+               if (regexec(&regex_endpoint, endpoint, ARRAY_SIZE(matches), matches, 0))
+                       continue;
+               endpoint[matches[1].rm_eo] = '\0';
+               endpoint = &endpoint[matches[1].rm_so];
+
+               next_mtu = get_route_mtu(endpoint);
+               if (next_mtu > 0 && next_mtu < endpoint_mtu)
+                       endpoint_mtu = next_mtu;
+       }
+
+       cndc("interface setmtu %s %d", iface, endpoint_mtu - 80);
+}
+
+static void add_route(const char *iface, unsigned int netid, const char *route)
+{
+       cndc("network route add %u %s %s", netid, iface, route);
+}
+
+static void set_routes(const char *iface, unsigned int netid)
+{
+       DEFINE_CMD(c);
+
+       for (char *allowedips = cmd_ret(&c, "wg show %s allowed-ips", iface); allowedips; allowedips = cmd_ret(&c, NULL)) {
+               char *start = strchr(allowedips, '\t');
+
+               if (!start)
+                       continue;
+               ++start;
+               for (char *allowedip = strtok(start, " \n"); allowedip; allowedip = strtok(NULL, " \n"))
+                       add_route(iface, netid, allowedip);
+       }
+}
+
+static void set_config(const char *iface, const char *config)
+{
+       FILE *config_writer;
+       _cleanup_free_ char *cmd = concat("wg setconf ", iface, " /proc/self/fd/0", NULL);
+       int ret;
+
+       printf("[#] %s\n", cmd);
+
+       config_writer = popen(cmd, "w");
+       if (!config_writer) {
+               perror("Error: popen");
+               exit(errno);
+       }
+       if (fputs(config, config_writer) < 0) {
+               perror("Error: fputs");
+               exit(errno);
+       }
+       ret = pclose(config_writer);
+       if (ret)
+               exit(WIFEXITED(ret) ? WEXITSTATUS(ret) : EIO);
+}
+
+static void broadcast_change(void)
+{
+       const char *pkg = getenv("CALLING_PACKAGE");
+
+       if (!pkg || strcmp(pkg, "com.wireguard.android"))
+               cmd("am broadcast -a com.wireguard.android.WGQUICK_CHANGE com.wireguard.android");
+}
+
+static void print_search_paths(FILE *file, const char *prefix)
+{
+       _cleanup_free_ char *paths = strdup(WG_CONFIG_SEARCH_PATHS);
+
+       for (char *path = strtok(paths, " "); path; path = strtok(NULL, " "))
+               fprintf(file, "%s%s\n", prefix, path);
+}
+
+static void cmd_usage(const char *program)
+{
+       printf( "Usage: %s [ up | down ] [ CONFIG_FILE | INTERFACE ]\n"
+               "\n"
+               "  CONFIG_FILE is a configuration file, whose filename is the interface name\n"
+               "  followed by `.conf'. Otherwise, INTERFACE is an interface name, with\n"
+               "  configuration found at:\n\n", program);
+       print_search_paths(stdout, "  - ");
+       printf( "\n  It is to be readable by wg(8)'s `setconf' sub-command, with the exception\n"
+               "  of the following additions to the [Interface] section, which are handled by\n"
+               "  this program:\n\n"
+               "  - Address: may be specified one or more times and contains one or more\n"
+               "    IP addresses (with an optional CIDR mask) to be set for the interface.\n"
+               "  - MTU: an optional MTU for the interface; if unspecified, auto-calculated.\n"
+               "  - DNS: an optional DNS server to use while the device is up.\n\n"
+               "  See wg-quick(8) for more info and examples.\n");
+}
+
+static char *cleanup_iface = NULL;
+
+static void cmd_up_cleanup(void)
+{
+       is_exiting = true;
+       if (cleanup_iface)
+               del_if(cleanup_iface);
+       free(cleanup_iface);
+}
+
+static void cmd_up(const char *iface, const char *config, unsigned int mtu, const char *addrs, const char *dnses)
+{
+       DEFINE_CMD(c);
+       unsigned int netid = 0;
+
+       if (cmd_ret(&c, "ip link show dev %s 2>/dev/null", iface)) {
+               fprintf(stderr, "Error: %s already exists\n", iface);
+               exit(EEXIST);
+       }
+
+       cleanup_iface = xstrdup(iface);
+       atexit(cmd_up_cleanup);
+
+       add_if(iface);
+       set_config(iface, config);
+       set_addr(iface, addrs);
+       up_if(&netid, iface);
+       set_dnses(netid, dnses);
+       set_routes(iface, netid);
+       set_mtu(iface, mtu);
+       broadcast_change();
+
+       free(cleanup_iface);
+       cleanup_iface = NULL;
+       exit(EXIT_SUCCESS);
+}
+
+static void cmd_down(const char *iface)
+{
+       DEFINE_CMD(c);
+       bool found = false;
+
+       char *ifaces = cmd_ret(&c, "wg show interfaces");
+       if (ifaces) {
+               for (char *eiface = strtok(ifaces, " \n"); eiface; eiface = strtok(NULL, " \n")) {
+                       if (!strcmp(iface, eiface)) {
+                               found = true;
+                               break;
+                       }
+               }
+       }
+       if (!found) {
+               fprintf(stderr, "Error: %s is not a WireGuard interface\n", iface);
+               exit(EMEDIUMTYPE);
+       }
+
+       del_if(iface);
+       broadcast_change();
+       exit(EXIT_SUCCESS);
+}
+
+static void parse_options(char **iface, char **config, unsigned int *mtu, char **addrs, char **dnses, const char *arg)
+{
+       _cleanup_fclose_ FILE *file = NULL;
+       _cleanup_free_ char *line = NULL;
+       _cleanup_free_ char *filename = NULL;
+       _cleanup_free_ char *paths = strdup(WG_CONFIG_SEARCH_PATHS);
+       regex_t regex_iface, regex_conf;
+       regmatch_t matches[2];
+       struct stat sbuf;
+       size_t n = 0;
+       bool in_interface_section = false;
+
+       *iface = *config = *addrs = *dnses = NULL;
+       *mtu = 0;
+
+       xregcomp(&regex_iface, "^[a-zA-Z0-9_=+.-]{1,15}$", REG_EXTENDED | REG_NOSUB);
+       xregcomp(&regex_conf, "/?([a-zA-Z0-9_=+.-]{1,15})\\.conf$", REG_EXTENDED);
+
+       if (!regexec(&regex_iface, arg, 0, NULL, 0)) {
+               for (char *path = strtok(paths, " "); path; path = strtok(NULL, " ")) {
+                       free(filename);
+                       if (asprintf(&filename, "%s/%s.conf", path, arg) < 0) {
+                               perror("Error: asprintf");
+                               exit(errno);
+                       }
+                       file = fopen(filename, "r");
+                       if (file)
+                               break;
+               }
+               if (!file) {
+                       fprintf(stderr, "Error: Unable to find configuration file for `%s' in:\n", arg);
+                       print_search_paths(stderr, "- ");
+                       exit(errno);
+               }
+       } else {
+               filename = xstrdup(arg);
+               file = fopen(filename, "r");
+               if (!file) {
+                       fprintf(stderr, "Error: Unable to find configuration file at `%s'\n", filename);
+                       exit(errno);
+               }
+       }
+
+       if (regexec(&regex_conf, filename, ARRAY_SIZE(matches), matches, 0)) {
+               fprintf(stderr, "Error: The config file must be a valid interface name, followed by .conf\n");
+               exit(EINVAL);
+       }
+
+       if (fstat(fileno(file), &sbuf) < 0) {
+               perror("Error: fstat");
+               exit(errno);
+       }
+       if (sbuf.st_mode & 0007)
+               fprintf(stderr, "Warning: `%s' is world accessible\n", filename);
+
+       filename[matches[1].rm_eo] = 0;
+       *iface = xstrdup(&filename[matches[1].rm_so]);
+
+       while (getline(&line, &n, file) >= 0) {
+               size_t len = strlen(line), j = 0;
+               if (len > (1<<16))
+                       return;
+               _cleanup_free_ char *clean = xmalloc(len + 1);
+
+               for (size_t i = 0; i < len; ++i) {
+                       if (!isspace(line[i]))
+                               clean[j++] = line[i];
+               }
+               clean[j] = '\0';
+
+               if (clean[0] == '[')
+                       in_interface_section = false;
+               if (!strcasecmp(clean, "[Interface]"))
+                       in_interface_section = true;
+               if (in_interface_section) {
+                       if (!strncasecmp(clean, "Address=", 8) && j > 8) {
+                               *addrs = concat_and_free(*addrs, ",", clean + 8);
+                               continue;
+                       } else if (!strncasecmp(clean, "DNS=", 4) && j > 4) {
+                               *dnses = concat_and_free(*dnses, ",", clean + 4);
+                               continue;
+                       } else if (!strncasecmp(clean, "MTU=", 4) && j > 4) {
+                               *mtu = atoi(clean + 4);
+                               continue;
+                       }
+               }
+               *config = concat_and_free(*config, "", line);
+       }
+
+       if (!*iface)
+               *iface = xstrdup("");
+       if (!*config)
+               *config = xstrdup("");
+       if (!*addrs)
+               *addrs = xstrdup("");
+       if (!*dnses)
+               *dnses = xstrdup("");
+}
+
+int main(int argc, char *argv[])
+{
+       _cleanup_free_ char *iface = NULL;
+       _cleanup_free_ char *config = NULL;
+       _cleanup_free_ char *addrs = NULL;
+       _cleanup_free_ char *dnses = NULL;
+       unsigned int mtu;
+
+       if (argc == 2 && (!strcmp(argv[1], "help") || !strcmp(argv[1], "--help") || !strcmp(argv[1], "-h")))
+               cmd_usage(argv[0]);
+       else if (argc == 3 && !strcmp(argv[1], "up")) {
+               auto_su(argc, argv);
+               parse_options(&iface, &config, &mtu, &addrs, &dnses, argv[2]);
+               cmd_up(iface, config, mtu, addrs, dnses);
+       } else if (argc == 3 && !strcmp(argv[1], "down")) {
+               auto_su(argc, argv);
+               parse_options(&iface, &config, &mtu, &addrs, &dnses, argv[2]);
+               cmd_down(iface);
+       } else {
+               cmd_usage(argv[0]);
+               return 1;
+       }
+       return 0;
+}