| 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 | #include "tripe.h" |
| 32 | |
| 33 | /*----- Static variables --------------------------------------------------*/ |
| 34 | |
| 35 | static slipif *slipifs; /* List of available interfaces */ |
| 36 | |
| 37 | /*----- Main code ---------------------------------------------------------*/ |
| 38 | |
| 39 | #if TUN_TYPE != TUN_SLIP |
| 40 | # error "Tunnel type mismatch: fix the Makefile" |
| 41 | #endif |
| 42 | |
| 43 | #define SL_END 0xc0 |
| 44 | #define SL_ESC 0xdb |
| 45 | #define SL_ESCEND 0xdc |
| 46 | #define SL_ESCESC 0xdd |
| 47 | |
| 48 | /* --- @t_read@ --- * |
| 49 | * |
| 50 | * Arguments: @int fd@ = file descriptor to read |
| 51 | * @unsigned mode@ = what's happened |
| 52 | * @void *v@ = pointer to tunnel block |
| 53 | * |
| 54 | * Returns: --- |
| 55 | * |
| 56 | * Use: Reads data from the tunnel. |
| 57 | */ |
| 58 | |
| 59 | static void t_read(int fd, unsigned mode, void *v) |
| 60 | { |
| 61 | tunnel *t = v; |
| 62 | ssize_t n; |
| 63 | const octet *p, *l, *ll; |
| 64 | octet *q; |
| 65 | unsigned st; |
| 66 | octet o; |
| 67 | buf b; |
| 68 | |
| 69 | /* --- Read the input data --- */ |
| 70 | |
| 71 | n = read(fd, buf_t, sizeof(buf_t)); |
| 72 | if (n < 0) { |
| 73 | if (errno == EINTR || |
| 74 | #ifdef EWOULDBLOCK |
| 75 | errno == EWOULDBLOCK || |
| 76 | #endif |
| 77 | errno == EAGAIN) |
| 78 | return; |
| 79 | a_warn("TUN %s read-error -- %s", t->sl->name, strerror(errno)); |
| 80 | return; |
| 81 | } |
| 82 | if (!n) { |
| 83 | a_warn("TUN %s slip eof", t->sl->name); |
| 84 | t->st = SLIPST_EOF; |
| 85 | sel_rmfile(&t->f); |
| 86 | return; |
| 87 | } |
| 88 | IF_TRACING(T_TUNNEL, { |
| 89 | trace_block(T_PACKET, "tunnel: SLIP-encapsulated data", |
| 90 | buf_t, n); |
| 91 | }) |
| 92 | |
| 93 | /* --- Decapsulate the packet --- */ |
| 94 | |
| 95 | for (p = buf_t, l = p + n, st = t->st, |
| 96 | q = t->buf + t->n, ll = t->buf + sizeof(t->buf); |
| 97 | p < l; |
| 98 | p++) { |
| 99 | o = *p; |
| 100 | switch (o) { |
| 101 | case SL_END: |
| 102 | if (st & SLIPST_BAD) |
| 103 | ; |
| 104 | else if (st & SLIPST_ESC) |
| 105 | a_warn("TUN %s slip escape-end", t->sl->name); |
| 106 | else if (q == t->buf) { |
| 107 | T( trace(T_TUNNEL, "tunnel: empty packet"); ) |
| 108 | } else { |
| 109 | IF_TRACING(T_TUNNEL, { |
| 110 | trace(T_TUNNEL, "tunnel: packet arrived"); |
| 111 | trace_block(T_PACKET, "tunnel: packet contents", |
| 112 | t->buf, q - t->buf); |
| 113 | }) |
| 114 | buf_init(&b, t->buf, q - t->buf); |
| 115 | p_tun(t->p, &b); |
| 116 | } |
| 117 | q = t->buf; |
| 118 | st &= ~(SLIPST_ESC | SLIPST_BAD); |
| 119 | break; |
| 120 | case SL_ESC: |
| 121 | if ((st & SLIPST_ESC) && !(st & SLIPST_BAD)) { |
| 122 | a_warn("TUN %s slip bad-escape", t->sl->name); |
| 123 | st |= SLIPST_BAD; |
| 124 | } else |
| 125 | st |= SLIPST_ESC; |
| 126 | break; |
| 127 | case SL_ESCEND: |
| 128 | if (st & SLIPST_ESC) |
| 129 | o = SL_END; |
| 130 | goto emit; |
| 131 | case SL_ESCESC: |
| 132 | if (st & SLIPST_ESC) |
| 133 | o = SL_ESC; |
| 134 | goto emit; |
| 135 | default: |
| 136 | if ((st & SLIPST_ESC) && !(st & SLIPST_BAD)) { |
| 137 | a_warn("TUN %s slip bad-escape", t->sl->name); |
| 138 | st |= SLIPST_BAD; |
| 139 | } |
| 140 | emit: |
| 141 | if (!(st & SLIPST_BAD)) { |
| 142 | if (q < ll) |
| 143 | *q++ = o; |
| 144 | else { |
| 145 | a_warn("TUN %s slip overflow", t->sl->name); |
| 146 | st |= SLIPST_BAD; |
| 147 | } |
| 148 | } |
| 149 | st &= ~SLIPST_ESC; |
| 150 | break; |
| 151 | } |
| 152 | } |
| 153 | |
| 154 | t->n = q - t->buf; |
| 155 | t->st = st; |
| 156 | } |
| 157 | |
| 158 | /* --- @tun_init@ --- * |
| 159 | * |
| 160 | * Arguments: --- |
| 161 | * |
| 162 | * Returns: --- |
| 163 | * |
| 164 | * Use: Initializes the tunneling system. Maybe this will require |
| 165 | * opening file descriptors or something. |
| 166 | */ |
| 167 | |
| 168 | void tun_init(void) |
| 169 | { |
| 170 | char *p, *q; |
| 171 | dstr d = DSTR_INIT; |
| 172 | slipif *sl, **tail = &slipifs; |
| 173 | unsigned long uli, ulo; |
| 174 | size_t n; |
| 175 | |
| 176 | /* --- Build the list of available interfaces --- */ |
| 177 | |
| 178 | if ((p = getenv("TRIPE_SLIPIF")) == 0) |
| 179 | die(1, "no slip interfaces listed: set TRIPE_SLIPIF"); |
| 180 | dstr_puts(&d, p); |
| 181 | |
| 182 | p = d.buf; |
| 183 | for (;;) { |
| 184 | uli = strtoul(p, &q, 0); |
| 185 | if (uli > INT_MAX || q == p) |
| 186 | goto whine; |
| 187 | if (*q != ',') |
| 188 | ulo = uli; |
| 189 | else { |
| 190 | p = q + 1; |
| 191 | ulo = strtoul(p, &q, 0); |
| 192 | if (ulo > INT_MAX || q == p) |
| 193 | goto whine; |
| 194 | } |
| 195 | if (*q != '=' || (n = strcspn(q + 1, ":")) == 0) |
| 196 | goto whine; |
| 197 | sl = CREATE(slipif); |
| 198 | sl->next = 0; |
| 199 | sl->ifd = uli; |
| 200 | sl->ofd = ulo; |
| 201 | sl->name = xmalloc(n + 1); |
| 202 | sl->f = 0; |
| 203 | memcpy(sl->name, q + 1, n); |
| 204 | sl->name[n] = 0; |
| 205 | *tail = sl; |
| 206 | tail = &sl->next; |
| 207 | T( trace(T_TUNNEL, "tunnel: declared slipif %d,%d=%s", |
| 208 | sl->ifd, sl->ofd, sl->name); ) |
| 209 | p = q + n + 1; |
| 210 | if (!*p) |
| 211 | break; |
| 212 | p++; |
| 213 | } |
| 214 | return; |
| 215 | |
| 216 | whine: |
| 217 | die(1, "bad slip interface list"); |
| 218 | } |
| 219 | |
| 220 | /* --- @tun_create@ --- * |
| 221 | * |
| 222 | * Arguments: @tunnel *t@ = pointer to tunnel block |
| 223 | * @peer *p@ = pointer to peer block |
| 224 | * |
| 225 | * Returns: Zero if it worked, nonzero on failure. |
| 226 | * |
| 227 | * Use: Initializes a new tunnel. |
| 228 | */ |
| 229 | |
| 230 | int tun_create(tunnel *t, peer *p) |
| 231 | { |
| 232 | slipif *sl; |
| 233 | static const char end[] = { SL_END, SL_END }; |
| 234 | |
| 235 | for (sl = slipifs; sl; sl = sl->next) { |
| 236 | if (!(sl->f & SLIPIFF_INUSE)) |
| 237 | goto found; |
| 238 | } |
| 239 | a_warn("TUN - slip no-slip-interfaces"); |
| 240 | return (-1); |
| 241 | |
| 242 | found: |
| 243 | t->p = p; |
| 244 | t->sl = sl; |
| 245 | t->st = 0; |
| 246 | t->n = 0; |
| 247 | sl->f |= SLIPIFF_INUSE; |
| 248 | sel_initfile(&sel, &t->f, sl->ifd, SEL_READ, t_read, t); |
| 249 | sel_addfile(&t->f); |
| 250 | write(sl->ofd, end, sizeof(end)); |
| 251 | T( trace(T_TUNNEL, "tunnel: attached interface %s to peer `%s'", |
| 252 | sl->name, p_name(p)); ) |
| 253 | return (0); |
| 254 | } |
| 255 | |
| 256 | /* --- @tun_ifname@ --- * |
| 257 | * |
| 258 | * Arguments: @tunnel *t@ = pointer to tunnel block |
| 259 | * |
| 260 | * Returns: A pointer to the tunnel's interface name. |
| 261 | */ |
| 262 | |
| 263 | const char *tun_ifname(tunnel *t) |
| 264 | { |
| 265 | return (t->sl->name); |
| 266 | } |
| 267 | |
| 268 | /* --- @tun_inject@ --- * |
| 269 | * |
| 270 | * Arguments: @tunnel *t@ = pointer to tunnel block |
| 271 | * @buf *b@ = buffer to send |
| 272 | * |
| 273 | * Returns: --- |
| 274 | * |
| 275 | * Use: Injects a packet into the local network stack. |
| 276 | */ |
| 277 | |
| 278 | void tun_inject(tunnel *t, buf *b) |
| 279 | { |
| 280 | octet buf[PKBUFSZ * 2 + 2]; |
| 281 | const octet *p, *l; |
| 282 | octet *q; |
| 283 | |
| 284 | IF_TRACING(T_TUNNEL, { |
| 285 | trace(T_TUNNEL, "tunnel: inject decrypted packet"); |
| 286 | trace_block(T_PACKET, "tunnel: packet contents", BBASE(b), BLEN(b)); |
| 287 | }) |
| 288 | |
| 289 | q = buf; |
| 290 | *q++ = SL_END; |
| 291 | for (p = BBASE(b), l = BCUR(b); p < l; p++) { |
| 292 | switch (*p) { |
| 293 | case SL_END: *q++ = SL_ESC; *q++ = SL_ESCEND; break; |
| 294 | case SL_ESC: *q++ = SL_ESC; *q++ = SL_ESCESC; break; |
| 295 | default: *q++ = *p; break; |
| 296 | } |
| 297 | } |
| 298 | *q++ = SL_END; |
| 299 | IF_TRACING(T_TUNNEL, { |
| 300 | trace_block(T_PACKET, "tunnel: SLIP-encapsulated contents", |
| 301 | buf, q - buf); |
| 302 | }) |
| 303 | write(t->sl->ofd, buf, q - buf); |
| 304 | } |
| 305 | |
| 306 | /* --- @tun_destroy@ --- * |
| 307 | * |
| 308 | * Arguments: @tunnel *t@ = pointer to tunnel block |
| 309 | * |
| 310 | * Returns: --- |
| 311 | * |
| 312 | * Use: Destroys a tunnel. |
| 313 | */ |
| 314 | |
| 315 | void tun_destroy(tunnel *t) |
| 316 | { |
| 317 | /* --- If it reported EOF, leave it out-of-action --- */ |
| 318 | |
| 319 | if (!(t->st & SLIPST_EOF)) { |
| 320 | sel_rmfile(&t->f); |
| 321 | t->sl->f &= ~SLIPIFF_INUSE; |
| 322 | } |
| 323 | } |
| 324 | |
| 325 | /*----- That's all, folks -------------------------------------------------*/ |