| 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 -------------------------------------------------*/ |