src/bridge.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU General Public License as published by
  10   the Free Software Foundation; either version 2 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <sys/socket.h>
  23 #include <sys/un.h>
  24 #include <sys/types.h>
  25 #include <fcntl.h>
  26 #include <unistd.h>
  27 #include <string.h>
  28 #include <errno.h>
  29 #include <sys/epoll.h>
  30 #include <stddef.h>
  31
  32 #include "log.h"
  33 #include "util.h"
  34 #include "socket-util.h"
  35
  36 #define BUFFER_SIZE (64*1024)
  37 #define EXTRA_SIZE 16
  38
  39 static bool initial_nul = false;
  40 static bool auth_over = false;
  41
  42 static void format_uid(char *buf, size_t l) {
  43         char text[20 + 1]; /* enough space for a 64bit integer plus NUL */
  44         unsigned j;
  45
  46         assert(l > 0);
  47
  48         snprintf(text, sizeof(text)-1, "%llu", (unsigned long long) geteuid());
  49         text[sizeof(text)-1] = 0;
  50
  51         memset(buf, 0, l);
  52
  53         for (j = 0; text[j] && j*2+2 < l; j++) {
  54                 buf[j*2]   = hexchar(text[j] >> 4);
  55                 buf[j*2+1] = hexchar(text[j] & 0xF);
  56         }
  57
  58         buf[j*2] = 0;
  59 }
  60
  61 static size_t patch_in_line(char *line, size_t l, size_t left) {
  62         size_t r;
  63
  64         if (line[0] == 0 && !initial_nul) {
  65                 initial_nul = true;
  66                 line += 1;
  67                 l -= 1;
  68                 r = 1;
  69         } else
  70                 r = 0;
  71
  72         if (l == 5 && strncmp(line, "BEGIN", 5) == 0) {
  73                 r += l;
  74                 auth_over = true;
  75
  76         } else if (l == 17 && strncmp(line, "NEGOTIATE_UNIX_FD", 17) == 0) {
  77                 memmove(line + 13, line + 17, left);
  78                 memcpy(line, "NEGOTIATE_NOP", 13);
  79                 r += 13;
  80
  81         } else if (l >= 14 && strncmp(line, "AUTH EXTERNAL ", 14) == 0) {
  82                 char uid[20*2 + 1];
  83                 size_t len;
  84
  85                 format_uid(uid, sizeof(uid));
  86                 len = strlen(uid);
  87                 assert(len <= EXTRA_SIZE);
  88
  89                 memmove(line + 14 + len, line + l, left);
  90                 memcpy(line + 14, uid, len);
  91
  92                 r += 14 + len;
  93         } else
  94                 r += l;
  95
  96         return r;
  97 }
  98
  99 static size_t patch_in_buffer(char* in_buffer, size_t *in_buffer_full) {
 100         size_t i, good = 0;
 101
 102         if (*in_buffer_full <= 0)
 103                 return *in_buffer_full;
 104
 105         /* If authentication is done, we don't touch anything anymore */
 106         if (auth_over)
 107                 return *in_buffer_full;
 108
 109         if (*in_buffer_full < 2)
 110                 return 0;
 111
 112         for (i = 0; i <= *in_buffer_full - 2; i ++) {
 113
 114                 /* Fully lines can be send on */
 115                 if (in_buffer[i] == '\r' && in_buffer[i+1] == '\n') {
 116                         if (i > good) {
 117                                 size_t old_length, new_length;
 118
 119                                 old_length = i - good;
 120                                 new_length = patch_in_line(in_buffer+good, old_length, *in_buffer_full - i);
 121                                 *in_buffer_full = *in_buffer_full + new_length - old_length;
 122
 123                                 good += new_length + 2;
 124
 125                         } else
 126                                 good = i+2;
 127                 }
 128
 129                 if (auth_over)
 130                         break;
 131         }
 132
 133         return good;
 134 }
 135
 136 int main(int argc, char *argv[]) {
 137         int r = EXIT_FAILURE, fd = -1, ep = -1;
 138         union sockaddr_union sa;
 139         char in_buffer[BUFFER_SIZE+EXTRA_SIZE], out_buffer[BUFFER_SIZE+EXTRA_SIZE];
 140         size_t in_buffer_full = 0, out_buffer_full = 0;
 141         struct epoll_event stdin_ev, stdout_ev, fd_ev;
 142         bool stdin_readable = false, stdout_writable = false, fd_readable = false, fd_writable = false;
 143         bool stdin_rhup = false, stdout_whup = false, fd_rhup = false, fd_whup = false;
 144
 145         if (argc > 1) {
 146                 log_error("This program takes no argument.");
 147                 return EXIT_FAILURE;
 148         }
 149
 150         log_set_target(LOG_TARGET_SYSLOG_OR_KMSG);
 151         log_parse_environment();
 152         log_open();
 153
 154         if ((fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0)) < 0) {
 155                 log_error("Failed to create socket: %s", strerror(errno));
 156                 goto finish;
 157         }
 158
 159         zero(sa);
 160         sa.un.sun_family = AF_UNIX;
 161         strncpy(sa.un.sun_path, "/run/dbus/system_bus_socket", sizeof(sa.un.sun_path));
 162
 163         if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + 1 + strlen(sa.un.sun_path+1)) < 0) {
 164                 log_error("Failed to connect: %m");
 165                 goto finish;
 166         }
 167
 168         fd_nonblock(STDIN_FILENO, 1);
 169         fd_nonblock(STDOUT_FILENO, 1);
 170
 171         if ((ep = epoll_create1(EPOLL_CLOEXEC)) < 0) {
 172                 log_error("Failed to create epoll: %m");
 173                 goto finish;
 174         }
 175
 176         zero(stdin_ev);
 177         stdin_ev.events = EPOLLIN|EPOLLET;
 178         stdin_ev.data.fd = STDIN_FILENO;
 179
 180         zero(stdout_ev);
 181         stdout_ev.events = EPOLLOUT|EPOLLET;
 182         stdout_ev.data.fd = STDOUT_FILENO;
 183
 184         zero(fd_ev);
 185         fd_ev.events = EPOLLIN|EPOLLOUT|EPOLLET;
 186         fd_ev.data.fd = fd;
 187
 188         if (epoll_ctl(ep, EPOLL_CTL_ADD, STDIN_FILENO, &stdin_ev) < 0 ||
 189             epoll_ctl(ep, EPOLL_CTL_ADD, STDOUT_FILENO, &stdout_ev) < 0 ||
 190             epoll_ctl(ep, EPOLL_CTL_ADD, fd, &fd_ev) < 0) {
 191                 log_error("Failed to regiser fds in epoll: %m");
 192                 goto finish;
 193         }
 194
 195         do {
 196                 struct epoll_event ev[16];
 197                 ssize_t k;
 198                 int i, nfds;
 199
 200                 if ((nfds = epoll_wait(ep, ev, ELEMENTSOF(ev), -1)) < 0) {
 201
 202                         if (errno == EINTR || errno == EAGAIN)
 203                                 continue;
 204
 205                         log_error("epoll_wait(): %m");
 206                         goto finish;
 207                 }
 208
 209                 assert(nfds >= 1);
 210
 211                 for (i = 0; i < nfds; i++) {
 212                         if (ev[i].data.fd == STDIN_FILENO) {
 213
 214                                 if (!stdin_rhup && (ev[i].events & (EPOLLHUP|EPOLLIN)))
 215                                         stdin_readable = true;
 216
 217                         } else if (ev[i].data.fd == STDOUT_FILENO) {
 218
 219                                 if (ev[i].events & EPOLLHUP) {
 220                                         stdout_writable = false;
 221                                         stdout_whup = true;
 222                                 }
 223
 224                                 if (!stdout_whup && (ev[i].events & EPOLLOUT))
 225                                         stdout_writable = true;
 226
 227                         } else if (ev[i].data.fd == fd) {
 228
 229                                 if (ev[i].events & EPOLLHUP) {
 230                                         fd_writable = false;
 231                                         fd_whup = true;
 232                                 }
 233
 234                                 if (!fd_rhup && (ev[i].events & (EPOLLHUP|EPOLLIN)))
 235                                         fd_readable = true;
 236
 237                                 if (!fd_whup && (ev[i].events & EPOLLOUT))
 238                                         fd_writable = true;
 239                         }
 240                 }
 241
 242                 while ((stdin_readable && in_buffer_full <= 0) ||
 243                        (fd_writable && patch_in_buffer(in_buffer, &in_buffer_full) > 0) ||
 244                        (fd_readable && out_buffer_full <= 0) ||
 245                        (stdout_writable && out_buffer_full > 0)) {
 246
 247                         size_t in_buffer_good = 0;
 248
 249                         if (stdin_readable && in_buffer_full < BUFFER_SIZE) {
 250
 251                                 if ((k = read(STDIN_FILENO, in_buffer + in_buffer_full, BUFFER_SIZE - in_buffer_full)) < 0) {
 252
 253                                         if (errno == EAGAIN)
 254                                                 stdin_readable = false;
 255                                         else if (errno == EPIPE || errno == ECONNRESET)
 256                                                 k = 0;
 257                                         else {
 258                                                 log_error("read(): %m");
 259                                                 goto finish;
 260                                         }
 261                                 } else
 262                                         in_buffer_full += (size_t) k;
 263
 264                                 if (k == 0) {
 265                                         stdin_rhup = true;
 266                                         stdin_readable = false;
 267                                         shutdown(STDIN_FILENO, SHUT_RD);
 268                                         close_nointr_nofail(STDIN_FILENO);
 269                                 }
 270                         }
 271
 272                         in_buffer_good = patch_in_buffer(in_buffer, &in_buffer_full);
 273
 274                         if (fd_writable && in_buffer_good > 0) {
 275
 276                                 if ((k = write(fd, in_buffer, in_buffer_good)) < 0) {
 277
 278                                         if (errno == EAGAIN)
 279                                                 fd_writable = false;
 280                                         else if (errno == EPIPE || errno == ECONNRESET) {
 281                                                 fd_whup = true;
 282                                                 fd_writable = false;
 283                                                 shutdown(fd, SHUT_WR);
 284                                         } else {
 285                                                 log_error("write(): %m");
 286                                                 goto finish;
 287                                         }
 288
 289                                 } else {
 290                                         assert(in_buffer_full >= (size_t) k);
 291                                         memmove(in_buffer, in_buffer + k, in_buffer_full - k);
 292                                         in_buffer_full -= k;
 293                                 }
 294                         }
 295
 296                         if (fd_readable && out_buffer_full < BUFFER_SIZE) {
 297
 298                                 if ((k = read(fd, out_buffer + out_buffer_full, BUFFER_SIZE - out_buffer_full)) < 0) {
 299
 300                                         if (errno == EAGAIN)
 301                                                 fd_readable = false;
 302                                         else if (errno == EPIPE || errno == ECONNRESET)
 303                                                 k = 0;
 304                                         else {
 305                                                 log_error("read(): %m");
 306                                                 goto finish;
 307                                         }
 308                                 }  else
 309                                         out_buffer_full += (size_t) k;
 310
 311                                 if (k == 0) {
 312                                         fd_rhup = true;
 313                                         fd_readable = false;
 314                                         shutdown(fd, SHUT_RD);
 315                                 }
 316                         }
 317
 318                         if (stdout_writable && out_buffer_full > 0) {
 319
 320                                 if ((k = write(STDOUT_FILENO, out_buffer, out_buffer_full)) < 0) {
 321
 322                                         if (errno == EAGAIN)
 323                                                 stdout_writable = false;
 324                                         else if (errno == EPIPE || errno == ECONNRESET) {
 325                                                 stdout_whup = true;
 326                                                 stdout_writable = false;
 327                                                 shutdown(STDOUT_FILENO, SHUT_WR);
 328                                                 close_nointr(STDOUT_FILENO);
 329                                         } else {
 330                                                 log_error("write(): %m");
 331                                                 goto finish;
 332                                         }
 333
 334                                 } else {
 335                                         assert(out_buffer_full >= (size_t) k);
 336                                         memmove(out_buffer, out_buffer + k, out_buffer_full - k);
 337                                         out_buffer_full -= k;
 338                                 }
 339                         }
 340                 }
 341
 342                 if (stdin_rhup && in_buffer_full <= 0 && !fd_whup) {
 343                         fd_whup = true;
 344                         fd_writable = false;
 345                         shutdown(fd, SHUT_WR);
 346                 }
 347
 348                 if (fd_rhup && out_buffer_full <= 0 && !stdout_whup) {
 349                         stdout_whup = true;
 350                         stdout_writable = false;
 351                         shutdown(STDOUT_FILENO, SHUT_WR);
 352                         close_nointr(STDOUT_FILENO);
 353                 }
 354
 355         } while (!stdout_whup || !fd_whup);
 356
 357         r = EXIT_SUCCESS;
 358
 359 finish:
 360         if (fd >= 0)
 361                 close_nointr_nofail(fd);
 362
 363         if (ep >= 0)
 364                 close_nointr_nofail(ep);
 365
 366         return r;
 367 }