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 "sock.h"
  32 #include "ioops.h"
  33 #include "curve.h"
  34 #include "xmalloc.h"
  35 #include "corking.h"
  36 #include "ioexact.h"
  37 #include "curvetun.h"
  38 #include "ct_servmgmt.h"
  39 #include "ct_usermgmt.h"
  40 #include "crypto_auth_hmacsha512256.h"
  41
  42 extern volatile sig_atomic_t sigint;
  43 static volatile sig_atomic_t closed_by_server = 0;
  44
  45 static void handler_udp_tun_to_net(int sfd, int dfd, struct curve25519_proto *p,
  46                                    struct curve25519_struct *c, char *buff,
  47                                    size_t len)
  48 {
  49         char *cbuff;
  50         ssize_t rlen, clen;
  51         struct ct_proto *hdr;
  52         size_t off = sizeof(struct ct_proto) + crypto_box_zerobytes;
  53
  54         if (!buff || len <= off)
  55                 return;
  56
  57         memset(buff, 0, len);
  58         while ((rlen = read(sfd, buff + off, len - off)) > 0) {
  59                 hdr = (struct ct_proto *) buff;
  60
  61                 memset(hdr, 0, sizeof(*hdr));
  62                 hdr->flags = 0;
  63
  64                 clen = curve25519_encode(c, p, (unsigned char *) (buff + off -
  65                                          crypto_box_zerobytes), (rlen +
  66                                          crypto_box_zerobytes), (unsigned char **)
  67                                          &cbuff);
  68                 if (unlikely(clen <= 0))
  69                         goto close;
  70
  71                 hdr->payload = htons((uint16_t) clen);
  72
  73                 set_udp_cork(dfd);
  74
  75                 write_exact(dfd, hdr, sizeof(struct ct_proto), 0);
  76                 write_exact(dfd, cbuff, clen, 0);
  77
  78                 set_udp_uncork(dfd);
  79
  80                 memset(buff, 0, len);
  81         }
  82
  83         return;
  84 close:
  85         closed_by_server = 1;
  86 }
  87
  88 static void handler_udp_net_to_tun(int sfd, int dfd, struct curve25519_proto *p,
  89                                    struct curve25519_struct *c, char *buff,
  90                                    size_t len)
  91 {
  92         char *cbuff;
  93         ssize_t rlen, clen;
  94         struct ct_proto *hdr;
  95         struct sockaddr_storage naddr;
  96
  97         socklen_t nlen = sizeof(naddr);
  98
  99         if (!buff || !len)
 100                 return;
 101
 102         memset(&naddr, 0, sizeof(naddr));
 103         while ((rlen = recvfrom(sfd, buff, len, 0, (struct sockaddr *) &naddr,
 104                                 &nlen)) > 0) {
 105                 hdr = (struct ct_proto *) buff;
 106
 107                 if (unlikely(rlen < sizeof(struct ct_proto)))
 108                         goto close;
 109                 if (unlikely(rlen - sizeof(*hdr) != ntohs(hdr->payload)))
 110                         goto close;
 111                 if (unlikely(ntohs(hdr->payload) == 0))
 112                         goto close;
 113                 if (hdr->flags & PROTO_FLAG_EXIT)
 114                         goto close;
 115
 116                 clen = curve25519_decode(c, p, (unsigned char *) buff +
 117                                          sizeof(struct ct_proto),
 118                                          rlen - sizeof(struct ct_proto),
 119                                          (unsigned char **) &cbuff, NULL);
 120                 if (unlikely(clen <= 0))
 121                         goto close;
 122
 123                 cbuff += crypto_box_zerobytes;
 124                 clen -= crypto_box_zerobytes;
 125
 126                 if (write(dfd, cbuff, clen)) { ; }
 127         }
 128
 129         return;
 130 close:
 131         closed_by_server = 1;
 132 }
 133
 134 static void handler_tcp_tun_to_net(int sfd, int dfd, struct curve25519_proto *p,
 135                                    struct curve25519_struct *c, char *buff,
 136                                    size_t len)
 137 {
 138         char *cbuff;
 139         ssize_t rlen, clen;
 140         struct ct_proto *hdr;
 141         size_t off = sizeof(struct ct_proto) + crypto_box_zerobytes;
 142
 143         if (!buff || len <= off)
 144                 return;
 145
 146         memset(buff, 0, len);
 147         while ((rlen = read(sfd, buff + off, len - off)) > 0) {
 148                 hdr = (struct ct_proto *) buff;
 149
 150                 memset(hdr, 0, sizeof(*hdr));
 151                 hdr->flags = 0;
 152
 153                 clen = curve25519_encode(c, p, (unsigned char *) (buff + off -
 154                                          crypto_box_zerobytes), (rlen +
 155                                          crypto_box_zerobytes), (unsigned char **)
 156                                          &cbuff);
 157                 if (unlikely(clen <= 0))
 158                         goto close;
 159
 160                 hdr->payload = htons((uint16_t) clen);
 161
 162                 set_tcp_cork(dfd);
 163
 164                 write_exact(dfd, hdr, sizeof(struct ct_proto), 0);
 165                 write_exact(dfd, cbuff, clen, 0);
 166
 167                 set_tcp_uncork(dfd);
 168
 169                 memset(buff, 0, len);
 170         }
 171
 172         return;
 173 close:
 174         closed_by_server = 1;
 175 }
 176
 177 extern ssize_t handler_tcp_read(int fd, char *buff, size_t len);
 178
 179 static void handler_tcp_net_to_tun(int sfd, int dfd, struct curve25519_proto *p,
 180                                    struct curve25519_struct *c, char *buff,
 181                                    size_t len)
 182 {
 183         char *cbuff;
 184         ssize_t rlen, clen;
 185         struct ct_proto *hdr;
 186
 187         if (!buff || !len)
 188                 return;
 189
 190         while ((rlen = handler_tcp_read(sfd, buff, len)) > 0) {
 191                 hdr = (struct ct_proto *) buff;
 192
 193                 if (unlikely(rlen < sizeof(struct ct_proto)))
 194                         goto close;
 195                 if (unlikely(rlen - sizeof(*hdr) != ntohs(hdr->payload)))
 196                         goto close;
 197                 if (unlikely(ntohs(hdr->payload) == 0))
 198                         goto close;
 199                 if (hdr->flags & PROTO_FLAG_EXIT)
 200                         goto close;
 201
 202                 clen = curve25519_decode(c, p, (unsigned char *) buff +
 203                                          sizeof(struct ct_proto),
 204                                          rlen - sizeof(struct ct_proto),
 205                                          (unsigned char **) &cbuff, NULL);
 206                 if (unlikely(clen <= 0))
 207                         goto close;
 208
 209                 cbuff += crypto_box_zerobytes;
 210                 clen -= crypto_box_zerobytes;
 211
 212                 if (write(dfd, cbuff, clen)) { ; }
 213         }
 214
 215         return;
 216 close:
 217         closed_by_server = 1;
 218 }
 219
 220 static void notify_init(int fd, int udp, struct curve25519_proto *p,
 221                         struct curve25519_struct *c, char *home)
 222 {
 223         int fd2, i;
 224         ssize_t err, clen;
 225         size_t us_len, msg_len, pad;
 226         struct ct_proto hdr;
 227         char username[256], path[PATH_MAX], *us, *cbuff, *msg;
 228         unsigned char auth[crypto_auth_hmacsha512256_BYTES], *token;
 229
 230         memset(&hdr, 0, sizeof(hdr));
 231         hdr.flags |= PROTO_FLAG_INIT;
 232
 233         memset(path, 0, sizeof(path));
 234         slprintf(path, sizeof(path), "%s/%s", home, FILE_USERNAM);
 235
 236         fd2 = open_or_die(path, O_RDONLY);
 237
 238         memset(username, 0, sizeof(username));
 239         err = read(fd2, username, sizeof(username));
 240         username[sizeof(username) - 1] = 0;
 241
 242         close(fd2);
 243
 244         token = get_serv_store_entry_auth_token();
 245         if (!token)
 246                 syslog_panic("Cannot find auth token for server!\n");
 247
 248         us_len = sizeof(struct username_struct) + crypto_box_zerobytes;
 249         us = xzmalloc(us_len);
 250
 251         err = username_msg(username, strlen(username) + 1,
 252                            us + crypto_box_zerobytes,
 253                            us_len - crypto_box_zerobytes);
 254         if (unlikely(err))
 255                 syslog_panic("Cannot create init message!\n");
 256
 257         clen = curve25519_encode(c, p, (unsigned char *) us, us_len,
 258                                  (unsigned char **) &cbuff);
 259         if (unlikely(clen <= 0))
 260                 syslog_panic("Init encrypt error!\n");
 261
 262         err = crypto_auth_hmacsha512256(auth, (unsigned char *) cbuff, clen, token);
 263         if (unlikely(err))
 264                 syslog_panic("Cannot create init hmac message!\n");
 265
 266         pad = ((uint32_t) secrand()) % 200;
 267         msg_len = clen + sizeof(auth) + pad;
 268
 269         msg = xzmalloc(msg_len);
 270         memcpy(msg, auth, sizeof(auth));
 271         memcpy(msg + sizeof(auth), cbuff, clen);
 272
 273         for (i = sizeof(auth) + clen; i < msg_len; ++i)
 274                 msg[i] = (uint8_t) secrand();
 275
 276         hdr.payload = htons((uint16_t) msg_len);
 277
 278         set_sock_cork(fd, udp);
 279
 280         write_exact(fd, &hdr, sizeof(struct ct_proto), 0);
 281         write_exact(fd, msg, msg_len, 0);
 282
 283         set_sock_uncork(fd, udp);
 284
 285         xfree(msg);
 286         xfree(us);
 287 }
 288
 289 static void notify_close(int fd)
 290 {
 291         struct ct_proto hdr;
 292
 293         memset(&hdr, 0, sizeof(hdr));
 294
 295         hdr.flags |= PROTO_FLAG_EXIT;
 296         hdr.payload = 0;
 297
 298         write_exact(fd, &hdr, sizeof(hdr), 0);
 299 }
 300
 301 int client_main(char *home, char *dev, char *host, char *port, int udp)
 302 {
 303         int fd = -1, tunfd = 0, retry_server = 0;
 304         int ret, try = 1, i;
 305         struct addrinfo hints, *ahead, *ai;
 306         struct pollfd fds[2];
 307         struct curve25519_proto *p;
 308         struct curve25519_struct *c;
 309         char *buff;
 310         size_t blen = TUNBUFF_SIZ; //FIXME
 311
 312 retry:
 313         if (!retry_server) {
 314                 openlog("curvetun", LOG_PID | LOG_CONS | LOG_NDELAY, LOG_DAEMON);
 315                 syslog(LOG_INFO, "curvetun client booting!\n");
 316         }
 317
 318         c = curve25519_tfm_alloc();
 319         p = get_serv_store_entry_proto_inf();
 320         if (!p)
 321                 syslog_panic("Cannot proto!\n");
 322
 323         memset(&hints, 0, sizeof(hints));
 324         hints.ai_family = PF_UNSPEC;
 325         hints.ai_socktype = udp ? SOCK_DGRAM : SOCK_STREAM;
 326         hints.ai_protocol = udp ? IPPROTO_UDP : IPPROTO_TCP;
 327         hints.ai_flags = AI_NUMERICSERV;
 328
 329         ret = getaddrinfo(host, port, &hints, &ahead);
 330         if (ret < 0) {
 331                 syslog(LOG_ERR, "Cannot get address info! Retry!\n");
 332                 curve25519_tfm_free(c);
 333                 fd = -1;
 334                 retry_server = 1;
 335                 closed_by_server = 0;
 336                 sleep(1);
 337                 goto retry;
 338         }
 339
 340         for (ai = ahead; ai != NULL && fd < 0; ai = ai->ai_next) {
 341                 fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 342                 if (fd < 0)
 343                         continue;
 344                 ret = connect(fd, ai->ai_addr, ai->ai_addrlen);
 345                 if (ret < 0) {
 346                         syslog(LOG_ERR, "Cannot connect to remote, try %d: %s!\n",
 347                                try++, strerror(errno));
 348                         close(fd);
 349                         fd = -1;
 350                         continue;
 351                 }
 352
 353                 set_socket_keepalive(fd);
 354                 set_mtu_disc_dont(fd);
 355                 if (!udp)
 356                         set_tcp_nodelay(fd);
 357         }
 358
 359         freeaddrinfo(ahead);
 360
 361         if (fd < 0) {
 362                 syslog(LOG_ERR, "Cannot create socket! Retry!\n");
 363                 curve25519_tfm_free(c);
 364                 fd = -1;
 365                 retry_server = 1;
 366                 closed_by_server = 0;
 367                 sleep(1);
 368                 goto retry;
 369         }
 370
 371         if (!retry_server)
 372                 tunfd = tun_open_or_die(dev ? dev : DEVNAME_CLIENT,
 373                                         IFF_TUN | IFF_NO_PI);
 374
 375         set_nonblocking_sloppy(fd);
 376         set_nonblocking_sloppy(tunfd);
 377
 378         memset(fds, 0, sizeof(fds));
 379         fds[0].fd = fd;
 380         fds[1].fd = tunfd;
 381         fds[0].events = POLLIN;
 382         fds[1].events = POLLIN;
 383
 384         buff = xmalloc_aligned(blen, 64);
 385
 386         notify_init(fd, udp, p, c, home);
 387
 388         syslog(LOG_INFO, "curvetun client ready!\n");
 389
 390         while (likely(!sigint && !closed_by_server)) {
 391                 poll(fds, 2, -1);
 392                 for (i = 0; i < 2; ++i) {
 393                         if ((fds[i].revents & POLLIN) != POLLIN)
 394                                 continue;
 395                         if (fds[i].fd == tunfd) {
 396                                 if (udp)
 397                                         handler_udp_tun_to_net(tunfd, fd, p, c,
 398                                                                buff, blen);
 399                                 else
 400                                         handler_tcp_tun_to_net(tunfd, fd, p, c,
 401                                                                buff, blen);
 402                         } else if (fds[i].fd == fd) {
 403                                 if (udp)
 404                                         handler_udp_net_to_tun(fd, tunfd, p, c,
 405                                                                buff, blen);
 406                                 else
 407                                         handler_tcp_net_to_tun(fd, tunfd, p, c,
 408                                                                buff, blen);
 409                         }
 410                 }
 411         }
 412
 413         syslog(LOG_INFO, "curvetun client prepare shut down!\n");
 414
 415         if (!closed_by_server)
 416                 notify_close(fd);
 417
 418         xfree(buff);
 419         close(fd);
 420         curve25519_tfm_free(c);
 421
 422         /* tundev still active */
 423         if (closed_by_server && !sigint) {
 424                 syslog(LOG_ERR, "curvetun connection retry attempt!\n");
 425                 fd = -1;
 426                 retry_server = 1;
 427                 closed_by_server = 0;
 428                 sleep(1);
 429                 goto retry;
 430         }
 431
 432         close(tunfd);
 433         syslog(LOG_INFO, "curvetun client shut down!\n");
 434         closelog();
 435
 436         return 0;
 437 }