mdw@git.distorted.org.uk Git - tripe/blob - priv/helper.c

   1 /* -*-c-*-
   2  *
   3  * Privilege-separated helper
   4  *
   5  * (c) 2008 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Trivial IP Encryption (TrIPE).
  11  *
  12  * TrIPE is free software: you can redistribute it and/or modify it under
  13  * the terms of the GNU General Public License as published by the Free
  14  * Software Foundation; either version 3 of the License, or (at your
  15  * option) any later version.
  16  *
  17  * TrIPE is distributed in the hope that it will be useful, but WITHOUT
  18  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  19  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  20  * for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with TrIPE.  If not, see <https://www.gnu.org/licenses/>.
  24  */
  25
  26 /*----- Header files ------------------------------------------------------*/
  27
  28 #include "priv.h"
  29
  30 /*----- Helper-side utilities ---------------------------------------------*/
  31
  32 /* --- @lose@ --- *
  33  *
  34  * Arguments:   @const char *excuse@ = what went wrong
  35  *
  36  * Returns:     Doesn't.
  37  *
  38  * Use:         Reports a fatal error and quits.
  39  */
  40
  41 static void NORETURN lose(const char *excuse)
  42 {
  43   moan("helper process bailing out: %s; error: %s",
  44        excuse,
  45        errno == -1 ? "Unexpected EOF" : strerror(errno));
  46   _exit(127);
  47 }
  48
  49 /*----- Diagnostic functions ----------------------------------------------*/
  50
  51 /* --- @itrace@ --- *
  52  *
  53  * Arguments:   @unsigned mask@ = trace mask to check
  54  *              @const char *fmt@ = message format
  55  *              @...@ = values for placeholders
  56  *
  57  * Returns:     ---
  58  *
  59  * Use:         Writes a trace message.
  60  */
  61
  62 #ifndef NTRACE
  63
  64 static void PRINTF_LIKE(2, 3) itrace(unsigned mask, const char *fmt, ...)
  65 {
  66   va_list ap;
  67   dstr d = DSTR_INIT;
  68
  69   va_start(ap, fmt);
  70   dstr_vputf(&d, fmt, &ap);
  71   if (pc_putuint(PS_TRACE) ||
  72       pc_putuint(mask) ||
  73       pc_putsz(d.len) ||
  74       pc_put(d.buf, d.len))
  75     lose("write (trace)");
  76   va_end(ap);
  77   dstr_destroy(&d);
  78 }
  79
  80 #endif
  81
  82 /* --- @warn@ --- *
  83  *
  84  * Arguments:   @const char *fmt@ = message format
  85  *              @...@ = values for placeholders
  86  *
  87  * Returns:     ---
  88  *
  89  * Use:         Writes a warning message.
  90  */
  91
  92 #define A_END ((char *)0)
  93
  94 static void EXECL_LIKE(0) IGNORABLE warn(const char *fmt, ...)
  95 {
  96   va_list ap;
  97   dstr d = DSTR_INIT, dd = DSTR_INIT;
  98
  99   va_start(ap, fmt);
 100   while (fmt) {
 101     if (*fmt == '?') {
 102       if (strcmp(fmt, "?ERRNO") == 0) {
 103         dstr_putf(&d, " E%d", errno);
 104         u_quotify(&d, strerror(errno));
 105       } else
 106         abort();
 107     } else {
 108       DRESET(&dd);
 109       dstr_vputf(&dd, fmt, &ap);
 110       u_quotify(&d, dd.buf);
 111     }
 112     fmt = va_arg(ap, const char *);
 113   }
 114   va_end(ap);
 115
 116   if (pc_putuint(PS_WARN) ||
 117       pc_putsz(d.len) ||
 118       pc_put(d.buf, d.len))
 119     lose("write (warn)");
 120
 121   dstr_destroy(&d);
 122   dstr_destroy(&dd);
 123 }
 124
 125 /*----- Tunnel drivers ----------------------------------------------------*/
 126
 127 /* --- @topen_DRIVER@ --- *
 128  *
 129  * Arguments:   @char **ifn@ = where to put the interface name
 130  *
 131  * Returns:     A file descriptor, or @-1@ on failure.
 132  *
 133  * Use:         Opens a tunnel device.
 134  */
 135
 136 #ifdef TUN_LINUX
 137
 138 #include <sys/ioctl.h>
 139 #include <linux/if.h>
 140 #include <linux/if_tun.h>
 141
 142 static int topen_linux(char **ifn)
 143 {
 144   int fd;
 145   struct ifreq iff;
 146
 147   if ((fd = open("/dev/net/tun", O_RDWR)) < 0) {
 148     warn("TUN", "-", "linux",
 149          "open-error", "/dev/net/tun", "?ERRNO",
 150          A_END);
 151     return (-1);
 152   }
 153   memset(&iff, 0, sizeof(iff));
 154   iff.ifr_name[0] = 0;
 155   iff.ifr_flags = IFF_TUN | IFF_NO_PI;
 156   if (ioctl(fd, TUNSETIFF, &iff) < 0) {
 157     warn("TUN", "-", "linux", "config-error", "?ERRNO", A_END);
 158     close(fd);
 159     return (-1);
 160   }
 161   iff.ifr_name[IFNAMSIZ - 1] = 0;
 162   *ifn = xstrdup(iff.ifr_name);
 163   return (fd);
 164 }
 165
 166 #endif
 167
 168 #ifdef TUN_BSD
 169
 170 static int topen_bsd(char **ifn)
 171 {
 172   int fd;
 173   unsigned n;
 174   char buf[16];
 175
 176   n = 0;
 177   for (;;) {
 178     sprintf(buf, "/dev/tun%u", n);
 179     if ((fd = open(buf, O_RDWR)) >= 0)
 180       break;
 181     switch (errno) {
 182       case EBUSY:
 183         T( itrace(T_PRIVSEP, "tunnel device %u busy: skipping", n); )
 184         break;
 185       case ENOENT:
 186         warn("TUN", "-", "bsd", "no-tunnel-devices", A_END);
 187        return (-1);
 188       default:
 189         warn("TUN", "-", "open-error", "%s", buf, "?ERRNO", A_END);
 190         break;
 191     }
 192     n++;
 193   }
 194   return (fd);
 195 }
 196
 197 #endif
 198
 199 #ifdef TUN_UNET
 200
 201 #include <sys/ioctl.h>
 202 #include <linux/if.h>
 203 #include <unet.h>
 204
 205 static int topen_unet(char **ifn)
 206 {
 207   int fd;
 208   int f;
 209   struct unet_info uni;
 210
 211   if ((fd = open("/dev/unet", O_RDWR)) < 0) {
 212     warn("TUN", "-", "unet", "open-error", "/dev/unet", "?ERRNO", A_END);
 213     goto fail_0;
 214   }
 215   if ((f = ioctl(fd, UNIOCGIFFLAGS)) < 0 ||
 216       ioctl(fd, UNIOCSIFFLAGS, f | IFF_POINTOPOINT)) {
 217     warn("TUN", "-", "unet", "config-error", "?ERRNO", A_END);
 218     goto fail_1;
 219   }
 220   if (ioctl(fd, UNIOCGINFO, &uni)) {
 221     warn("TUN", "-", "unet", "getinfo-error", "?ERRNO", A_END);
 222     goto fail_1;
 223   }
 224   *ifn = xstrdup(uni.uni_ifname);
 225   return (fd);
 226
 227 fail_1:
 228   close(fd);
 229 fail_0:
 230   return (-1);
 231 }
 232
 233 #endif
 234
 235 static const struct tunnel {
 236   const char *name;
 237   int (*open)(char **);
 238 } tunnels[] = {
 239 #ifdef TUN_LINUX
 240   { "linux", topen_linux },
 241 #endif
 242 #ifdef TUN_BSD
 243   { "bsd", topen_bsd },
 244 #endif
 245 #ifdef TUN_UNET
 246   { "unet", topen_unet },
 247 #endif
 248   { 0, 0 }
 249 };
 250
 251 /*----- Helper process core -----------------------------------------------*/
 252
 253 int main(int argc, char *argv[])
 254 {
 255   struct sockaddr_un sun;
 256   socklen_t slen = sizeof(sun);
 257   unsigned rq;
 258   dstr d = DSTR_INIT;
 259   const struct tunnel *t;
 260   char *ifn = 0;
 261   int fd;
 262   ssize_t n;
 263
 264   ego(argv[0]);
 265   if (argc != 1 ||
 266       getpeername(0, (struct sockaddr *)&sun, &slen) ||
 267       sun.sun_family != AF_UNIX)
 268     die(EXIT_FAILURE, "please do not run this program again.");
 269
 270   for (;;) {
 271     if (pc_getuint(&rq)) {
 272       if (errno == -1) break;
 273       else lose("read (main)");
 274     }
 275     switch (rq) {
 276       case PS_TUNRQ:
 277         DRESET(&d);
 278         if (pc_getstring(&d)) lose("read (tunnel)");
 279         for (t = tunnels;; t++) {
 280           if (!t->name) lose("unknown tunnel");
 281           if (strcmp(d.buf, t->name) == 0) break;
 282         }
 283         T( itrace(T_PRIVSEP,
 284                     "privsep: received request for %s tunnel",
 285                     t->name); )
 286         if ((fd = t->open(&ifn)) < 0)
 287           goto err;
 288         rq = PS_TUNFD;
 289         n = fdpass_send(pc_fd, fd, &rq, sizeof(rq)); close(fd);
 290         if (n < 0) { xfree(ifn); goto err; }
 291         else if (n < sizeof(rq)) lose("partial write (fd-pass)");
 292         if (pc_putstring(ifn)) lose("write (ifname)");
 293         xfree(ifn);
 294         break;
 295       err:
 296         if (pc_putuint(PS_TUNERR) || pc_puterr(errno)) lose("write (error)");
 297         break;
 298       default:
 299         lose("bad request");
 300         break;
 301     }
 302   }
 303   _exit(0);
 304 }
 305
 306 /*----- That's all, folks -------------------------------------------------*/