ct_client.c

   1 /*
   2  * curvetun - the cipherspace wormhole creator
   3  * Part of the netsniff-ng project
   4  * Copyright 2011 Daniel Borkmann <daniel@netsniff-ng.org>,
   5  * Subject to the GPL, version 2.
   6  */
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <unistd.h>
  12 #include <netdb.h>
  13 #include <fcntl.h>
  14 #include <signal.h>
  15 #include <syslog.h>
  16 #include <limits.h>
  17 #include <netinet/in.h>
  18 #include <arpa/inet.h>
  19 #include <sys/types.h>
  20 #include <sys/socket.h>
  21 #include <sys/ioctl.h>
  22 #include <sys/stat.h>
  23 #include <sys/poll.h>
  24 #include <netinet/tcp.h>
  25 #include <netinet/udp.h>
  26 #include <linux/if_tun.h>
  27
  28 #include "built_in.h"
  29 #include "die.h"
  30 #include "str.h"
  31 #include "xio.h"
  32 #include "xutils.h"
  33 #include "curve.h"
  34 #include "xmalloc.h"
  35 #include "corking.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, 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                 if (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, 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                 if (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         memset(&hdr, 0, sizeof(hdr));
 230         hdr.flags |= PROTO_FLAG_INIT;
 231
 232         memset(path, 0, sizeof(path));
 233         slprintf(path, sizeof(path), "%s/%s", home, FILE_USERNAM);
 234
 235         fd2 = open_or_die(path, O_RDONLY);
 236
 237         memset(username, 0, sizeof(username));
 238         err = read(fd2, username, sizeof(username));
 239         username[sizeof(username) - 1] = 0;
 240
 241         close(fd2);
 242
 243         token = get_serv_store_entry_auth_token();
 244         if (!token)
 245                 syslog_panic("Cannot find auth token for server!\n");
 246
 247         us_len = sizeof(struct username_struct) + crypto_box_zerobytes;
 248         us = xzmalloc(us_len);
 249
 250         err = username_msg(username, strlen(username) + 1,
 251                            us + crypto_box_zerobytes,
 252                            us_len - crypto_box_zerobytes);
 253         if (unlikely(err))
 254                 syslog_panic("Cannot create init message!\n");
 255
 256         clen = curve25519_encode(c, p, (unsigned char *) us, us_len,
 257                                  (unsigned char **) &cbuff);
 258         if (unlikely(clen <= 0))
 259                 syslog_panic("Init encrypt error!\n");
 260
 261         err = crypto_auth_hmacsha512256(auth, (unsigned char *) cbuff, clen, token);
 262         if (unlikely(err))
 263                 syslog_panic("Cannot create init hmac message!\n");
 264
 265         pad = ((uint32_t) secrand()) % 200;
 266         msg_len = clen + sizeof(auth) + pad;
 267
 268         msg = xzmalloc(msg_len);
 269         memcpy(msg, auth, sizeof(auth));
 270         memcpy(msg + sizeof(auth), cbuff, clen);
 271
 272         for (i = sizeof(auth) + clen; i < msg_len; ++i)
 273                 msg[i] = (uint8_t) secrand();
 274
 275         hdr.payload = htons((uint16_t) msg_len);
 276
 277         set_sock_cork(fd, udp);
 278
 279         write_exact(fd, &hdr, sizeof(struct ct_proto), 0);
 280         write_exact(fd, msg, msg_len, 0);
 281
 282         set_sock_uncork(fd, udp);
 283
 284         xfree(msg);
 285         xfree(us);
 286 }
 287
 288 static void notify_close(int fd)
 289 {
 290         struct ct_proto hdr;
 291
 292         memset(&hdr, 0, sizeof(hdr));
 293
 294         hdr.flags |= PROTO_FLAG_EXIT;
 295         hdr.payload = 0;
 296
 297         write_exact(fd, &hdr, sizeof(hdr), 0);
 298 }
 299
 300 int client_main(char *home, char *dev, char *host, char *port, int udp)
 301 {
 302         int fd = -1, tunfd = 0, retry_server = 0;
 303         int ret, try = 1, i;
 304         struct addrinfo hints, *ahead, *ai;
 305         struct pollfd fds[2];
 306         struct curve25519_proto *p;
 307         struct curve25519_struct *c;
 308         char *buff;
 309         size_t blen = TUNBUFF_SIZ; //FIXME
 310
 311 retry:
 312         if (!retry_server) {
 313                 openlog("curvetun", LOG_PID | LOG_CONS | LOG_NDELAY, LOG_DAEMON);
 314                 syslog(LOG_INFO, "curvetun client booting!\n");
 315         }
 316
 317         c = xmalloc(sizeof(struct curve25519_struct));
 318
 319         curve25519_alloc_or_maybe_die(c);
 320
 321         p = get_serv_store_entry_proto_inf();
 322         if (!p)
 323                 syslog_panic("Cannot proto!\n");
 324
 325         memset(&hints, 0, sizeof(hints));
 326         hints.ai_family = PF_UNSPEC;
 327         hints.ai_socktype = udp ? SOCK_DGRAM : SOCK_STREAM;
 328         hints.ai_protocol = udp ? IPPROTO_UDP : IPPROTO_TCP;
 329         hints.ai_flags = AI_NUMERICSERV;
 330
 331         ret = getaddrinfo(host, port, &hints, &ahead);
 332         if (ret < 0) {
 333                 syslog(LOG_ERR, "Cannot get address info! Retry!\n");
 334                 curve25519_free(c);
 335                 xfree(c);
 336                 fd = -1;
 337                 retry_server = 1;
 338                 closed_by_server = 0;
 339                 sleep(1);
 340                 goto retry;
 341         }
 342
 343         for (ai = ahead; ai != NULL && fd < 0; ai = ai->ai_next) {
 344                 fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 345                 if (fd < 0)
 346                         continue;
 347                 ret = connect(fd, ai->ai_addr, ai->ai_addrlen);
 348                 if (ret < 0) {
 349                         syslog(LOG_ERR, "Cannot connect to remote, try %d: %s!\n",
 350                                try++, strerror(errno));
 351                         close(fd);
 352                         fd = -1;
 353                         continue;
 354                 }
 355
 356                 set_socket_keepalive(fd);
 357                 set_mtu_disc_dont(fd);
 358                 if (!udp)
 359                         set_tcp_nodelay(fd);
 360         }
 361
 362         freeaddrinfo(ahead);
 363
 364         if (fd < 0) {
 365                 syslog(LOG_ERR, "Cannot create socket! Retry!\n");
 366                 curve25519_free(c);
 367                 xfree(c);
 368                 fd = -1;
 369                 retry_server = 1;
 370                 closed_by_server = 0;
 371                 sleep(1);
 372                 goto retry;
 373         }
 374
 375         if (!retry_server)
 376                 tunfd = tun_open_or_die(dev ? dev : DEVNAME_CLIENT,
 377                                         IFF_TUN | IFF_NO_PI);
 378
 379         set_nonblocking_sloppy(fd);
 380         set_nonblocking_sloppy(tunfd);
 381
 382         memset(fds, 0, sizeof(fds));
 383         fds[0].fd = fd;
 384         fds[1].fd = tunfd;
 385         fds[0].events = POLLIN;
 386         fds[1].events = POLLIN;
 387
 388         buff = xmalloc_aligned(blen, 64);
 389
 390         notify_init(fd, udp, p, c, home);
 391
 392         syslog(LOG_INFO, "curvetun client ready!\n");
 393
 394         while (likely(!sigint && !closed_by_server)) {
 395                 poll(fds, 2, -1);
 396                 for (i = 0; i < 2; ++i) {
 397                         if ((fds[i].revents & POLLIN) != POLLIN)
 398                                 continue;
 399                         if (fds[i].fd == tunfd) {
 400                                 if (udp)
 401                                         handler_udp_tun_to_net(tunfd, fd, p, c,
 402                                                                buff, blen);
 403                                 else
 404                                         handler_tcp_tun_to_net(tunfd, fd, p, c,
 405                                                                buff, blen);
 406                         } else if (fds[i].fd == fd) {
 407                                 if (udp)
 408                                         handler_udp_net_to_tun(fd, tunfd, p, c,
 409                                                                buff, blen);
 410                                 else
 411                                         handler_tcp_net_to_tun(fd, tunfd, p, c,
 412                                                                buff, blen);
 413                         }
 414                 }
 415         }
 416
 417         syslog(LOG_INFO, "curvetun client prepare shut down!\n");
 418
 419         if (!closed_by_server)
 420                 notify_close(fd);
 421
 422         xfree(buff);
 423         close(fd);
 424         curve25519_free(c);
 425         xfree(c);
 426
 427         /* tundev still active */
 428         if (closed_by_server && !sigint) {
 429                 syslog(LOG_ERR, "curvetun connection retry attempt!\n");
 430                 fd = -1;
 431                 retry_server = 1;
 432                 closed_by_server = 0;
 433                 sleep(1);
 434                 goto retry;
 435         }
 436
 437         close(tunfd);
 438         syslog(LOG_INFO, "curvetun client shut down!\n");
 439         closelog();
 440
 441         return 0;
 442 }