| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id$ |
| 4 | * |
| 5 | * Tunnel packets via SLIP |
| 6 | * |
| 7 | * (c) 2005 Straylight/Edgeware |
| 8 | */ |
| 9 | |
| 10 | /*----- Licensing notice --------------------------------------------------* |
| 11 | * |
| 12 | * This file is part of Trivial IP Encryption (TrIPE). |
| 13 | * |
| 14 | * TrIPE is free software; you can redistribute it and/or modify |
| 15 | * it under the terms of the GNU General Public License as published by |
| 16 | * the Free Software Foundation; either version 2 of the License, or |
| 17 | * (at your option) any later version. |
| 18 | * |
| 19 | * TrIPE is distributed in the hope that it will be useful, |
| 20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 22 | * GNU General Public License for more details. |
| 23 | * |
| 24 | * You should have received a copy of the GNU General Public License |
| 25 | * along with TrIPE; if not, write to the Free Software Foundation, |
| 26 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 27 | */ |
| 28 | |
| 29 | /*----- Header files ------------------------------------------------------*/ |
| 30 | |
| 31 | #define TUN_INTERNALS |
| 32 | |
| 33 | #include "tripe.h" |
| 34 | |
| 35 | /*----- Data structures ---------------------------------------------------*/ |
| 36 | |
| 37 | typedef struct slipif { |
| 38 | struct slipif *next; /* Next one in the list */ |
| 39 | int ifd, ofd; /* File descriptors to talk on */ |
| 40 | char *name; /* Interface name */ |
| 41 | pid_t kid; /* Child process id */ |
| 42 | unsigned f; /* Various flags */ |
| 43 | # define F_INUSE 1u /* Interface is in use */ |
| 44 | # define F_DYNAMIC 2u /* Interface found dynamically */ |
| 45 | } slipif; |
| 46 | |
| 47 | struct tunnel { |
| 48 | const tunnel_ops *ops; /* Pointer to operations */ |
| 49 | slipif *sl; /* My interface record */ |
| 50 | sel_file f; /* Selector for SLIP tty */ |
| 51 | struct peer *p; /* Pointer to my peer */ |
| 52 | unsigned st; /* Current parser state */ |
| 53 | # define ST_ESC 1u /* Last saw an escape character */ |
| 54 | # define ST_BAD 2u /* This packet is malformed */ |
| 55 | # define ST_EOF 4u /* File descriptor reported EOF */ |
| 56 | size_t n; /* Number of bytes used in buffer */ |
| 57 | octet buf[PKBUFSZ]; /* Buffer for incoming data */ |
| 58 | }; |
| 59 | |
| 60 | /*----- Static variables --------------------------------------------------*/ |
| 61 | |
| 62 | static slipif *slipifs; /* List of available interfaces */ |
| 63 | static const char *slipcmd; /* Script to make new interfaces */ |
| 64 | |
| 65 | /*----- Main code ---------------------------------------------------------*/ |
| 66 | |
| 67 | #define SL_END 0xc0 |
| 68 | #define SL_ESC 0xdb |
| 69 | #define SL_ESCEND 0xdc |
| 70 | #define SL_ESCESC 0xdd |
| 71 | |
| 72 | /* --- @t_read@ --- * |
| 73 | * |
| 74 | * Arguments: @int fd@ = file descriptor to read |
| 75 | * @unsigned mode@ = what's happened |
| 76 | * @void *v@ = pointer to tunnel block |
| 77 | * |
| 78 | * Returns: --- |
| 79 | * |
| 80 | * Use: Reads data from the tunnel. |
| 81 | */ |
| 82 | |
| 83 | static void t_read(int fd, unsigned mode, void *v) |
| 84 | { |
| 85 | tunnel *t = v; |
| 86 | ssize_t n; |
| 87 | const octet *p, *l, *ll; |
| 88 | octet *q; |
| 89 | unsigned st; |
| 90 | octet o; |
| 91 | buf b; |
| 92 | |
| 93 | /* --- Read the input data --- */ |
| 94 | |
| 95 | n = read(fd, buf_t, sizeof(buf_t)); |
| 96 | if (n < 0) { |
| 97 | if (errno == EINTR || |
| 98 | #if defined(EWOULDBLOCK) && EWOULDBLOCK != EAGAIN |
| 99 | errno == EWOULDBLOCK || |
| 100 | #endif |
| 101 | errno == EAGAIN) |
| 102 | return; |
| 103 | a_warn("TUN %s read-error -- %s", t->sl->name, strerror(errno)); |
| 104 | return; |
| 105 | } |
| 106 | if (!n) { |
| 107 | a_warn("TUN %s slip eof", t->sl->name); |
| 108 | t->st = ST_EOF; |
| 109 | sel_rmfile(&t->f); |
| 110 | return; |
| 111 | } |
| 112 | IF_TRACING(T_TUNNEL, { |
| 113 | trace_block(T_PACKET, "tunnel: SLIP-encapsulated data", |
| 114 | buf_t, n); |
| 115 | }) |
| 116 | |
| 117 | /* --- Decapsulate the packet --- */ |
| 118 | |
| 119 | for (p = buf_t, l = p + n, st = t->st, |
| 120 | q = t->buf + t->n, ll = t->buf + sizeof(t->buf); |
| 121 | p < l; |
| 122 | p++) { |
| 123 | o = *p; |
| 124 | switch (o) { |
| 125 | case SL_END: |
| 126 | if (st & ST_BAD) |
| 127 | ; |
| 128 | else if (st & ST_ESC) |
| 129 | a_warn("TUN %s slip escape-end", t->sl->name); |
| 130 | else if (q == t->buf) { |
| 131 | T( trace(T_TUNNEL, "tunnel: empty packet"); ) |
| 132 | } else { |
| 133 | IF_TRACING(T_TUNNEL, { |
| 134 | trace(T_TUNNEL, "tunnel: packet arrived"); |
| 135 | trace_block(T_PACKET, "tunnel: packet contents", |
| 136 | t->buf, q - t->buf); |
| 137 | }) |
| 138 | buf_init(&b, t->buf, q - t->buf); |
| 139 | p_tun(t->p, &b); |
| 140 | } |
| 141 | q = t->buf; |
| 142 | st &= ~(ST_ESC | ST_BAD); |
| 143 | break; |
| 144 | case SL_ESC: |
| 145 | if ((st & ST_ESC) && !(st & ST_BAD)) { |
| 146 | a_warn("TUN %s slip bad-escape", t->sl->name); |
| 147 | st |= ST_BAD; |
| 148 | } else |
| 149 | st |= ST_ESC; |
| 150 | break; |
| 151 | case SL_ESCEND: |
| 152 | if (st & ST_ESC) |
| 153 | o = SL_END; |
| 154 | goto emit; |
| 155 | case SL_ESCESC: |
| 156 | if (st & ST_ESC) |
| 157 | o = SL_ESC; |
| 158 | goto emit; |
| 159 | default: |
| 160 | if ((st & ST_ESC) && !(st & ST_BAD)) { |
| 161 | a_warn("TUN %s slip bad-escape", t->sl->name); |
| 162 | st |= ST_BAD; |
| 163 | } |
| 164 | emit: |
| 165 | if (!(st & ST_BAD)) { |
| 166 | if (q < ll) |
| 167 | *q++ = o; |
| 168 | else { |
| 169 | a_warn("TUN %s slip overflow", t->sl->name); |
| 170 | st |= ST_BAD; |
| 171 | } |
| 172 | } |
| 173 | st &= ~ST_ESC; |
| 174 | break; |
| 175 | } |
| 176 | } |
| 177 | |
| 178 | t->n = q - t->buf; |
| 179 | t->st = st; |
| 180 | } |
| 181 | |
| 182 | /* --- @t_init@ --- * |
| 183 | * |
| 184 | * Arguments: --- |
| 185 | * |
| 186 | * Returns: --- |
| 187 | * |
| 188 | * Use: Initializes the tunneling system. Maybe this will require |
| 189 | * opening file descriptors or something. |
| 190 | */ |
| 191 | |
| 192 | static void t_init(void) |
| 193 | { |
| 194 | char *p, *q; |
| 195 | dstr d = DSTR_INIT; |
| 196 | slipif *sl, **tail = &slipifs; |
| 197 | unsigned long uli, ulo; |
| 198 | size_t n; |
| 199 | |
| 200 | if ((p = getenv("TRIPE_SLIPIF")) == 0) |
| 201 | return; |
| 202 | |
| 203 | /* --- Build the list of available interfaces --- */ |
| 204 | |
| 205 | dstr_puts(&d, p); |
| 206 | |
| 207 | p = d.buf; |
| 208 | for (;;) { |
| 209 | if (*p == '/' || *p == '.') { |
| 210 | slipcmd = p; |
| 211 | T( trace(T_TUNNEL, "tunnel: declared slip command `%s'", slipcmd); ) |
| 212 | break; |
| 213 | } |
| 214 | uli = strtoul(p, &q, 0); |
| 215 | if (uli > INT_MAX || q == p) |
| 216 | goto whine; |
| 217 | if (*q != ',') |
| 218 | ulo = uli; |
| 219 | else { |
| 220 | p = q + 1; |
| 221 | ulo = strtoul(p, &q, 0); |
| 222 | if (ulo > INT_MAX || q == p) |
| 223 | goto whine; |
| 224 | } |
| 225 | if (*q != '=' || (n = strcspn(q + 1, ":")) == 0) |
| 226 | goto whine; |
| 227 | sl = CREATE(slipif); |
| 228 | sl->next = 0; |
| 229 | sl->ifd = uli; |
| 230 | fdflags(sl->ifd, O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
| 231 | fdflags(sl->ofd, O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC); |
| 232 | sl->ofd = ulo; |
| 233 | sl->name = xmalloc(n + 1); |
| 234 | sl->kid = -1; |
| 235 | sl->f = 0; |
| 236 | memcpy(sl->name, q + 1, n); |
| 237 | sl->name[n] = 0; |
| 238 | *tail = sl; |
| 239 | tail = &sl->next; |
| 240 | T( trace(T_TUNNEL, "tunnel: declared slipif %d,%d=%s", |
| 241 | sl->ifd, sl->ofd, sl->name); ) |
| 242 | p = q + n + 1; |
| 243 | if (!*p) |
| 244 | break; |
| 245 | p++; |
| 246 | } |
| 247 | return; |
| 248 | |
| 249 | whine: |
| 250 | moan("bad slip interface list"); |
| 251 | } |
| 252 | |
| 253 | /* --- @t_create@ --- * |
| 254 | * |
| 255 | * Arguments: @peer *p@ = pointer to peer block |
| 256 | * |
| 257 | * Returns: A tunnel block if it worked, or null on failure. |
| 258 | * |
| 259 | * Use: Initializes a new tunnel. |
| 260 | */ |
| 261 | |
| 262 | static tunnel *t_create(peer *p) |
| 263 | { |
| 264 | slipif *sl = 0; |
| 265 | int pin[2] = { -1, -1 }, pout[2] = { -1, -1 }; |
| 266 | pid_t kid = -1; |
| 267 | dstr d = DSTR_INIT; |
| 268 | unsigned char ch; |
| 269 | tunnel *t; |
| 270 | static const char end[] = { SL_END, SL_END }; |
| 271 | |
| 272 | /* --- Try to find a spare static interface --- */ |
| 273 | |
| 274 | for (sl = slipifs; sl; sl = sl->next) { |
| 275 | if (!(sl->f & F_INUSE)) { |
| 276 | T( trace(T_TUNNEL, "tunnel: %s using static slipif %s", |
| 277 | p_name(p), sl->name); ) |
| 278 | goto found; |
| 279 | } |
| 280 | } |
| 281 | |
| 282 | /* --- If no dynamic interfaces are available, give up --- */ |
| 283 | |
| 284 | if (!slipcmd) { |
| 285 | a_warn("TUN - slip no-slip-interfaces"); |
| 286 | goto fail; |
| 287 | } |
| 288 | |
| 289 | /* --- Fork off a child process to create a dynamic SLIP interface --- */ |
| 290 | |
| 291 | if (pipe(pin) || pipe(pout)) { |
| 292 | a_warn("TUN - slip pipe-error -- %s", strerror(errno)); |
| 293 | goto fail; |
| 294 | } |
| 295 | if ((kid = fork()) < 0) { |
| 296 | a_warn("TUN - slip fork-error -- %s", strerror(errno)); |
| 297 | goto fail; |
| 298 | } |
| 299 | if (!kid) { |
| 300 | close(pin[1]); |
| 301 | close(pout[0]); |
| 302 | dup2(pin[0], STDIN_FILENO); |
| 303 | dup2(pout[1], STDOUT_FILENO); |
| 304 | execlp(slipcmd, slipcmd, p_name(p), (char *)0); |
| 305 | _exit(127); |
| 306 | } |
| 307 | |
| 308 | /* --- Read the interface name --- */ |
| 309 | |
| 310 | sl = CREATE(slipif); |
| 311 | close(pin[0]); pin[0] = -1; |
| 312 | close(pout[1]); pout[1] = -1; |
| 313 | for (;;) { |
| 314 | errno = EIO; |
| 315 | if (read(pout[0], &ch, 1) != 1 || ch == SL_END) { |
| 316 | a_warn("TUN - slip read-ifname-failed -- %s", strerror(errno)); |
| 317 | goto fail; |
| 318 | } |
| 319 | if (ch == '\n') |
| 320 | break; |
| 321 | DPUTC(&d, (char)ch); |
| 322 | } |
| 323 | DPUTZ(&d); |
| 324 | sl->name = xstrdup(d.buf); |
| 325 | sl->ifd = pout[0]; |
| 326 | sl->ofd = pin[1]; |
| 327 | sl->kid = kid; |
| 328 | sl->next = 0; |
| 329 | sl->f = F_DYNAMIC; |
| 330 | T( trace(T_TUNNEL, "tunnel: %s using dynamic slipif %s", |
| 331 | p_name(p), sl->name); ) |
| 332 | fdflags(pout[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC); |
| 333 | fdflags(pin[1], O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC); |
| 334 | |
| 335 | /* --- Set up the new tunnel --- */ |
| 336 | |
| 337 | found: |
| 338 | t = CREATE(tunnel); |
| 339 | t->ops = &tun_slip; |
| 340 | t->p = p; |
| 341 | t->sl = sl; |
| 342 | t->st = 0; |
| 343 | t->n = 0; |
| 344 | sl->f |= F_INUSE; |
| 345 | sel_initfile(&sel, &t->f, sl->ifd, SEL_READ, t_read, t); |
| 346 | sel_addfile(&t->f); |
| 347 | write(sl->ofd, end, sizeof(end)); |
| 348 | dstr_destroy(&d); |
| 349 | return (t); |
| 350 | |
| 351 | /* --- Tidy up after a failure --- */ |
| 352 | |
| 353 | fail: |
| 354 | #define CLOSE(fd) do if (fd != -1) close(fd); while (0) |
| 355 | CLOSE(pin[0]); CLOSE(pout[0]); |
| 356 | CLOSE(pin[1]); CLOSE(pout[1]); |
| 357 | #undef CLOSE |
| 358 | if (kid != -1) kill(kid, SIGTERM); |
| 359 | if (sl && (sl->f & F_DYNAMIC)) DESTROY(sl); |
| 360 | dstr_destroy(&d); |
| 361 | return (0); |
| 362 | } |
| 363 | |
| 364 | /* --- @t_ifname@ --- * |
| 365 | * |
| 366 | * Arguments: @tunnel *t@ = pointer to tunnel block |
| 367 | * |
| 368 | * Returns: A pointer to the tunnel's interface name. |
| 369 | */ |
| 370 | |
| 371 | static const char *t_ifname(tunnel *t) { return (t->sl->name); } |
| 372 | |
| 373 | /* --- @t_inject@ --- * |
| 374 | * |
| 375 | * Arguments: @tunnel *t@ = pointer to tunnel block |
| 376 | * @buf *b@ = buffer to send |
| 377 | * |
| 378 | * Returns: --- |
| 379 | * |
| 380 | * Use: Injects a packet into the local network stack. |
| 381 | */ |
| 382 | |
| 383 | static void t_inject(tunnel *t, buf *b) |
| 384 | { |
| 385 | octet buf[PKBUFSZ * 2 + 2]; |
| 386 | const octet *p, *l; |
| 387 | octet *q; |
| 388 | |
| 389 | IF_TRACING(T_TUNNEL, { |
| 390 | trace(T_TUNNEL, "tunnel: inject decrypted packet"); |
| 391 | trace_block(T_PACKET, "tunnel: packet contents", BBASE(b), BLEN(b)); |
| 392 | }) |
| 393 | |
| 394 | q = buf; |
| 395 | *q++ = SL_END; |
| 396 | for (p = BBASE(b), l = BCUR(b); p < l; p++) { |
| 397 | switch (*p) { |
| 398 | case SL_END: *q++ = SL_ESC; *q++ = SL_ESCEND; break; |
| 399 | case SL_ESC: *q++ = SL_ESC; *q++ = SL_ESCESC; break; |
| 400 | default: *q++ = *p; break; |
| 401 | } |
| 402 | } |
| 403 | *q++ = SL_END; |
| 404 | IF_TRACING(T_TUNNEL, { |
| 405 | trace_block(T_PACKET, "tunnel: SLIP-encapsulated contents", |
| 406 | buf, q - buf); |
| 407 | }) |
| 408 | write(t->sl->ofd, buf, q - buf); |
| 409 | } |
| 410 | |
| 411 | /* --- @t_destroy@ --- * |
| 412 | * |
| 413 | * Arguments: @tunnel *t@ = pointer to tunnel block |
| 414 | * |
| 415 | * Returns: --- |
| 416 | * |
| 417 | * Use: Destroys a tunnel. |
| 418 | */ |
| 419 | |
| 420 | static void t_destroy(tunnel *t) |
| 421 | { |
| 422 | slipif *sl = t->sl; |
| 423 | |
| 424 | /* --- If it reported EOF, leave it out-of-action --- */ |
| 425 | |
| 426 | if (!(t->st & ST_EOF)) { |
| 427 | sel_rmfile(&t->f); |
| 428 | sl->f &= ~F_INUSE; |
| 429 | } |
| 430 | if (sl && (sl->f & F_DYNAMIC)) { |
| 431 | T( trace(T_TUNNEL, "tunnel: releasing dynamic slipif %s", sl->name); ) |
| 432 | close(sl->ofd); |
| 433 | close(sl->ifd); |
| 434 | kill(sl->kid, SIGTERM); |
| 435 | xfree(sl->name); |
| 436 | DESTROY(sl); |
| 437 | } |
| 438 | DESTROY(t); |
| 439 | } |
| 440 | |
| 441 | const tunnel_ops tun_slip = { |
| 442 | "slip", |
| 443 | t_init, |
| 444 | t_create, |
| 445 | t_ifname, |
| 446 | t_inject, |
| 447 | t_destroy |
| 448 | }; |
| 449 | |
| 450 | /*----- That's all, folks -------------------------------------------------*/ |