src/ct_client.c

   1 /*
   2  * curvetun - the cipherspace wormhole creator
   3  * Part of the netsniff-ng project
   4  * By Daniel Borkmann <daniel@netsniff-ng.org>
   5  * Copyright 2011 Daniel Borkmann <daniel@netsniff-ng.org>,
   6  * Subject to the GPL, version 2.
   7  */
   8
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <unistd.h>
  13 #include <netdb.h>
  14 #include <fcntl.h>
  15 #include <signal.h>
  16 #include <syslog.h>
  17 #include <limits.h>
  18 #include <netinet/in.h>
  19 #include <arpa/inet.h>
  20 #include <sys/types.h>
  21 #include <sys/socket.h>
  22 #include <sys/ioctl.h>
  23 #include <sys/stat.h>
  24 #include <sys/poll.h>
  25 #include <netinet/tcp.h>
  26 #include <netinet/udp.h>
  27 #include <linux/if_tun.h>
  28
  29 #include "built_in.h"
  30 #include "die.h"
  31 #include "xio.h"
  32 #include "xutils.h"
  33 #include "curve.h"
  34 #include "mtrand.h"
  35 #include "xmalloc.h"
  36 #include "curvetun.h"
  37 #include "ct_servmgmt.h"
  38 #include "ct_usermgmt.h"
  39 #include "crypto_auth_hmacsha512256.h"
  40
  41 extern volatile sig_atomic_t sigint;
  42 static volatile sig_atomic_t closed_by_server = 0;
  43
  44 static void handler_udp_tun_to_net(int sfd, int dfd, struct curve25519_proto *p,
  45                                    struct curve25519_struct *c, char *buff,
  46                                    size_t len)
  47 {
  48         char *cbuff;
  49         ssize_t rlen, clen;
  50         struct ct_proto *hdr;
  51         size_t off = sizeof(struct ct_proto) + crypto_box_zerobytes;
  52
  53         if (!buff || len <= off)
  54                 return;
  55
  56         memset(buff, 0, len);
  57         while ((rlen = read(sfd, buff + off, len - off)) > 0) {
  58                 hdr = (struct ct_proto *) buff;
  59
  60                 memset(hdr, 0, sizeof(*hdr));
  61                 hdr->flags = 0;
  62
  63                 clen = curve25519_encode(c, p, (unsigned char *) (buff + off -
  64                                          crypto_box_zerobytes), (rlen +
  65                                          crypto_box_zerobytes), (unsigned char **)
  66                                          &cbuff);
  67                 if (unlikely(clen <= 0))
  68                         goto close;
  69
  70                 hdr->payload = htons((uint16_t) clen);
  71
  72                 set_udp_cork(dfd);
  73
  74                 write_exact(dfd, hdr, sizeof(struct ct_proto), 0);
  75                 write_exact(dfd, cbuff, clen, 0);
  76
  77                 set_udp_uncork(dfd);
  78
  79                 memset(buff, 0, len);
  80         }
  81
  82         return;
  83 close:
  84         closed_by_server = 1;
  85 }
  86
  87 static void handler_udp_net_to_tun(int sfd, int dfd, struct curve25519_proto *p,
  88                                    struct curve25519_struct *c, char *buff,
  89                                    size_t len)
  90 {
  91         char *cbuff;
  92         ssize_t rlen, err, clen;
  93         struct ct_proto *hdr;
  94         struct sockaddr_storage naddr;
  95
  96         socklen_t nlen = sizeof(naddr);
  97
  98         if (!buff || !len)
  99                 return;
 100
 101         memset(&naddr, 0, sizeof(naddr));
 102         while ((rlen = recvfrom(sfd, buff, len, 0, (struct sockaddr *) &naddr,
 103                                 &nlen)) > 0) {
 104                 hdr = (struct ct_proto *) buff;
 105
 106                 if (unlikely(rlen < sizeof(struct ct_proto)))
 107                         goto close;
 108                 if (unlikely(rlen - sizeof(*hdr) != ntohs(hdr->payload)))
 109                         goto close;
 110                 if (unlikely(ntohs(hdr->payload) == 0))
 111                         goto close;
 112                 if (hdr->flags & PROTO_FLAG_EXIT)
 113                         goto close;
 114
 115                 clen = curve25519_decode(c, p, (unsigned char *) buff +
 116                                          sizeof(struct ct_proto),
 117                                          rlen - sizeof(struct ct_proto),
 118                                          (unsigned char **) &cbuff, NULL);
 119                 if (unlikely(clen <= 0))
 120                         goto close;
 121
 122                 cbuff += crypto_box_zerobytes;
 123                 clen -= crypto_box_zerobytes;
 124
 125                 err = write(dfd, cbuff, clen);
 126         }
 127
 128         return;
 129 close:
 130         closed_by_server = 1;
 131 }
 132
 133 static void handler_tcp_tun_to_net(int sfd, int dfd, struct curve25519_proto *p,
 134                                    struct curve25519_struct *c, char *buff,
 135                                    size_t len)
 136 {
 137         char *cbuff;
 138         ssize_t rlen, clen;
 139         struct ct_proto *hdr;
 140         size_t off = sizeof(struct ct_proto) + crypto_box_zerobytes;
 141
 142         if (!buff || len <= off)
 143                 return;
 144
 145         memset(buff, 0, len);
 146         while ((rlen = read(sfd, buff + off, len - off)) > 0) {
 147                 hdr = (struct ct_proto *) buff;
 148
 149                 memset(hdr, 0, sizeof(*hdr));
 150                 hdr->flags = 0;
 151
 152                 clen = curve25519_encode(c, p, (unsigned char *) (buff + off -
 153                                          crypto_box_zerobytes), (rlen +
 154                                          crypto_box_zerobytes), (unsigned char **)
 155                                          &cbuff);
 156                 if (unlikely(clen <= 0))
 157                         goto close;
 158
 159                 hdr->payload = htons((uint16_t) clen);
 160
 161                 set_tcp_cork(dfd);
 162
 163                 write_exact(dfd, hdr, sizeof(struct ct_proto), 0);
 164                 write_exact(dfd, cbuff, clen, 0);
 165
 166                 set_tcp_uncork(dfd);
 167
 168                 memset(buff, 0, len);
 169         }
 170
 171         return;
 172 close:
 173         closed_by_server = 1;
 174 }
 175
 176 extern ssize_t handler_tcp_read(int fd, char *buff, size_t len);
 177
 178 static void handler_tcp_net_to_tun(int sfd, int dfd, struct curve25519_proto *p,
 179                                    struct curve25519_struct *c, char *buff,
 180                                    size_t len)
 181 {
 182         char *cbuff;
 183         ssize_t rlen, err, clen;
 184         struct ct_proto *hdr;
 185
 186         if (!buff || !len)
 187                 return;
 188
 189         while ((rlen = handler_tcp_read(sfd, buff, len)) > 0) {
 190                 hdr = (struct ct_proto *) buff;
 191
 192                 if (unlikely(rlen < sizeof(struct ct_proto)))
 193                         goto close;
 194                 if (unlikely(rlen - sizeof(*hdr) != ntohs(hdr->payload)))
 195                         goto close;
 196                 if (unlikely(ntohs(hdr->payload) == 0))
 197                         goto close;
 198                 if (hdr->flags & PROTO_FLAG_EXIT)
 199                         goto close;
 200
 201                 clen = curve25519_decode(c, p, (unsigned char *) buff +
 202                                          sizeof(struct ct_proto),
 203                                          rlen - sizeof(struct ct_proto),
 204                                          (unsigned char **) &cbuff, NULL);
 205                 if (unlikely(clen <= 0))
 206                         goto close;
 207
 208                 cbuff += crypto_box_zerobytes;
 209                 clen -= crypto_box_zerobytes;
 210
 211                 err = write(dfd, cbuff, clen);
 212         }
 213
 214         return;
 215 close:
 216         closed_by_server = 1;
 217 }
 218
 219 static void notify_init(int fd, int udp, struct curve25519_proto *p,
 220                         struct curve25519_struct *c, char *home)
 221 {
 222         int fd2, i;
 223         ssize_t err, clen;
 224         size_t us_len, msg_len, pad;
 225         struct ct_proto hdr;
 226         char username[256], path[PATH_MAX], *us, *cbuff, *msg;
 227         unsigned char auth[crypto_auth_hmacsha512256_BYTES], *token;
 228
 229         mt_init_by_random_device();
 230
 231         memset(&hdr, 0, sizeof(hdr));
 232         hdr.flags |= PROTO_FLAG_INIT;
 233
 234         memset(path, 0, sizeof(path));
 235         slprintf(path, sizeof(path), "%s/%s", home, FILE_USERNAM);
 236
 237         fd2 = open_or_die(path, O_RDONLY);
 238
 239         memset(username, 0, sizeof(username));
 240         err = read(fd2, username, sizeof(username));
 241         username[sizeof(username) - 1] = 0;
 242
 243         close(fd2);
 244
 245         token = get_serv_store_entry_auth_token();
 246         if (!token)
 247                 syslog_panic("Cannot find auth token for server!\n");
 248
 249         us_len = sizeof(struct username_struct) + crypto_box_zerobytes;
 250         us = xzmalloc(us_len);
 251
 252         err = username_msg(username, strlen(username) + 1,
 253                            us + crypto_box_zerobytes,
 254                            us_len - crypto_box_zerobytes);
 255         if (unlikely(err))
 256                 syslog_panic("Cannot create init message!\n");
 257
 258         clen = curve25519_encode(c, p, (unsigned char *) us, us_len,
 259                                  (unsigned char **) &cbuff);
 260         if (unlikely(clen <= 0))
 261                 syslog_panic("Init encrypt error!\n");
 262
 263         err = crypto_auth_hmacsha512256(auth, (unsigned char *) cbuff, clen, token);
 264         if (unlikely(err))
 265                 syslog_panic("Cannot create init hmac message!\n");
 266
 267         pad = mt_rand_int32() % 200;
 268         msg_len = clen + sizeof(auth) + pad;
 269
 270         msg = xzmalloc(msg_len);
 271         memcpy(msg, auth, sizeof(auth));
 272         memcpy(msg + sizeof(auth), cbuff, clen);
 273
 274         for (i = sizeof(auth) + clen; i < msg_len; ++i)
 275                 msg[i] = (uint8_t) mt_rand_int32();
 276
 277         hdr.payload = htons((uint16_t) msg_len);
 278
 279         set_sock_cork(fd, udp);
 280
 281         write_exact(fd, &hdr, sizeof(struct ct_proto), 0);
 282         write_exact(fd, msg, msg_len, 0);
 283
 284         set_sock_uncork(fd, udp);
 285
 286         xfree(msg);
 287         xfree(us);
 288 }
 289
 290 static void notify_close(int fd)
 291 {
 292         struct ct_proto hdr;
 293
 294         memset(&hdr, 0, sizeof(hdr));
 295
 296         hdr.flags |= PROTO_FLAG_EXIT;
 297         hdr.payload = 0;
 298
 299         write_exact(fd, &hdr, sizeof(hdr), 0);
 300 }
 301
 302 int client_main(char *home, char *dev, char *host, char *port, int udp)
 303 {
 304         int fd = -1, tunfd = 0, retry_server = 0;
 305         int ret, try = 1, i;
 306         struct addrinfo hints, *ahead, *ai;
 307         struct sockaddr_in6 *saddr6;
 308         struct pollfd fds[2];
 309         struct curve25519_proto *p;
 310         struct curve25519_struct *c;
 311         char *buff;
 312         size_t blen = TUNBUFF_SIZ; //FIXME
 313
 314 retry:
 315         if (!retry_server) {
 316                 openlog("curvetun", LOG_PID | LOG_CONS | LOG_NDELAY, LOG_DAEMON);
 317                 syslog(LOG_INFO, "curvetun client booting!\n");
 318         }
 319
 320         c = xmalloc(sizeof(struct curve25519_struct));
 321
 322         ret = curve25519_alloc_or_maybe_die(c);
 323         if (ret < 0)
 324                 syslog_panic("Cannot init curve!\n");
 325
 326         p = get_serv_store_entry_proto_inf();
 327         if (!p)
 328                 syslog_panic("Cannot proto!\n");
 329
 330         memset(&hints, 0, sizeof(hints));
 331         hints.ai_family = PF_UNSPEC;
 332         hints.ai_socktype = udp ? SOCK_DGRAM : SOCK_STREAM;
 333         hints.ai_protocol = udp ? IPPROTO_UDP : IPPROTO_TCP;
 334         hints.ai_flags = AI_NUMERICSERV;
 335
 336         ret = getaddrinfo(host, port, &hints, &ahead);
 337         if (ret < 0) {
 338                 syslog(LOG_ERR, "Cannot get address info! Retry!\n");
 339                 curve25519_free(c);
 340                 xfree(c);
 341                 fd = -1;
 342                 retry_server = 1;
 343                 closed_by_server = 0;
 344                 sleep(1);
 345                 goto retry;
 346         }
 347
 348         for (ai = ahead; ai != NULL && fd < 0; ai = ai->ai_next) {
 349                 if (ai->ai_family == PF_INET6)
 350                         saddr6 = (struct sockaddr_in6 *) ai->ai_addr;
 351                 fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 352                 if (fd < 0)
 353                         continue;
 354                 ret = connect(fd, ai->ai_addr, ai->ai_addrlen);
 355                 if (ret < 0) {
 356                         syslog(LOG_ERR, "Cannot connect to remote, try %d: %s!\n",
 357                                try++, strerror(errno));
 358                         close(fd);
 359                         fd = -1;
 360                         continue;
 361                 }
 362
 363                 set_socket_keepalive(fd);
 364                 set_mtu_disc_dont(fd);
 365                 if (!udp)
 366                         set_tcp_nodelay(fd);
 367         }
 368
 369         freeaddrinfo(ahead);
 370
 371         if (fd < 0) {
 372                 syslog(LOG_ERR, "Cannot create socket! Retry!\n");
 373                 curve25519_free(c);
 374                 xfree(c);
 375                 fd = -1;
 376                 retry_server = 1;
 377                 closed_by_server = 0;
 378                 sleep(1);
 379                 goto retry;
 380         }
 381
 382         if (!retry_server)
 383                 tunfd = tun_open_or_die(dev ? dev : DEVNAME_CLIENT,
 384                                         IFF_TUN | IFF_NO_PI);
 385
 386         set_nonblocking_sloppy(fd);
 387         set_nonblocking_sloppy(tunfd);
 388
 389         memset(fds, 0, sizeof(fds));
 390         fds[0].fd = fd;
 391         fds[1].fd = tunfd;
 392         fds[0].events = POLLIN;
 393         fds[1].events = POLLIN;
 394
 395         buff = xmalloc_aligned(blen, 64);
 396
 397         notify_init(fd, udp, p, c, home);
 398
 399         syslog(LOG_INFO, "curvetun client ready!\n");
 400
 401         while (likely(!sigint && !closed_by_server)) {
 402                 poll(fds, 2, -1);
 403                 for (i = 0; i < 2; ++i) {
 404                         if ((fds[i].revents & POLLIN) != POLLIN)
 405                                 continue;
 406                         if (fds[i].fd == tunfd) {
 407                                 if (udp)
 408                                         handler_udp_tun_to_net(tunfd, fd, p, c,
 409                                                                buff, blen);
 410                                 else
 411                                         handler_tcp_tun_to_net(tunfd, fd, p, c,
 412                                                                buff, blen);
 413                         } else if (fds[i].fd == fd) {
 414                                 if (udp)
 415                                         handler_udp_net_to_tun(fd, tunfd, p, c,
 416                                                                buff, blen);
 417                                 else
 418                                         handler_tcp_net_to_tun(fd, tunfd, p, c,
 419                                                                buff, blen);
 420                         }
 421                 }
 422         }
 423
 424         syslog(LOG_INFO, "curvetun client prepare shut down!\n");
 425
 426         if (!closed_by_server)
 427                 notify_close(fd);
 428
 429         xfree(buff);
 430         close(fd);
 431         curve25519_free(c);
 432         xfree(c);
 433
 434         /* tundev still active */
 435         if (closed_by_server && !sigint) {
 436                 syslog(LOG_ERR, "curvetun connection retry attempt!\n");
 437                 fd = -1;
 438                 retry_server = 1;
 439                 closed_by_server = 0;
 440                 sleep(1);
 441                 goto retry;
 442         }
 443
 444         close(tunfd);
 445         syslog(LOG_INFO, "curvetun client shut down!\n");
 446         closelog();
 447
 448         return 0;
 449 }