mdw@git.distorted.org.uk Git - secnet/blob - slip.c

   1 /* When dealing with SLIP (to a pty, or ipif) we have separate rx, tx
   2    and client buffers.  When receiving we may read() any amount, not
   3    just whole packets.  When transmitting we need to bytestuff anyway,
   4    and may be part-way through receiving. */
   5
   6 /*
   7  * This file is part of secnet.
   8  * See README for full list of copyright holders.
   9  *
  10  * secnet is free software; you can redistribute it and/or modify it
  11  * under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 3 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * secnet is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * version 3 along with secnet; if not, see
  22  * https://www.gnu.org/licenses/gpl.html.
  23  */
  24
  25 #include "secnet.h"
  26 #include "util.h"
  27 #include "netlink.h"
  28 #include "process.h"
  29 #include "unaligned.h"
  30 #include <stdio.h>
  31 #include <string.h>
  32 #include <unistd.h>
  33 #include <errno.h>
  34 #include <fcntl.h>
  35
  36 #define SLIP_END    192
  37 #define SLIP_ESC    219
  38 #define SLIP_ESCEND 220
  39 #define SLIP_ESCESC 221
  40
  41 struct slip {
  42     struct netlink nl;
  43     struct buffer_if *buff; /* We unstuff received packets into here
  44                                and send them to the netlink code. */
  45     bool_t pending_esc;
  46     bool_t ignoring_packet; /* If this packet was corrupt or overlong,
  47                                we ignore everything up to the next END */
  48     netlink_deliver_fn *netlink_to_tunnel;
  49 };
  50
  51 /* Generic SLIP mangling code */
  52
  53 static void slip_write(int fd, const uint8_t *p, size_t l)
  54 {
  55     while (l) {
  56         ssize_t written=write(fd,p,l);
  57         if (written<0) {
  58             if (errno==EINTR) {
  59                 continue;
  60             } else if (iswouldblock(errno)) {
  61                 lg_perror(0,"slip",0,M_ERR,errno,"write() (packet(s) lost)");
  62                 return;
  63             } else {
  64                 fatal_perror("slip_stuff: write()");
  65             }
  66         }
  67         assert(written>0);
  68         assert((size_t)written<=l);
  69         p+=written;
  70         l-=written;
  71     }
  72 }
  73
  74 static void slip_stuff(struct slip *st, struct buffer_if *buf, int fd)
  75 {
  76     uint8_t txbuf[DEFAULT_BUFSIZE];
  77     uint8_t *i;
  78     int32_t j=0;
  79
  80     BUF_ASSERT_USED(buf);
  81
  82     /* There's probably a much more efficient way of implementing this */
  83     txbuf[j++]=SLIP_END;
  84     for (i=buf->start; i<(buf->start+buf->size); i++) {
  85         switch (*i) {
  86         case SLIP_END:
  87             txbuf[j++]=SLIP_ESC;
  88             txbuf[j++]=SLIP_ESCEND;
  89             break;
  90         case SLIP_ESC:
  91             txbuf[j++]=SLIP_ESC;
  92             txbuf[j++]=SLIP_ESCESC;
  93             break;
  94         default:
  95             txbuf[j++]=*i;
  96             break;
  97         }
  98         if ((j+2)>DEFAULT_BUFSIZE) {
  99             slip_write(fd,txbuf,j);
 100             j=0;
 101         }
 102     }
 103     txbuf[j++]=SLIP_END;
 104     slip_write(fd,txbuf,j);
 105     BUF_FREE(buf);
 106 }
 107
 108 static void slip_unstuff(struct slip *st, uint8_t *buf, uint32_t l)
 109 {
 110     uint32_t i;
 111
 112     BUF_ASSERT_USED(st->buff);
 113     for (i=0; i<l; i++) {
 114         int outputchr;
 115         enum { OUTPUT_END = 256, OUTPUT_NOTHING = 257 };
 116
 117         if (!st->buff->size)
 118             buffer_init(st->buff,calculate_max_start_pad());
 119
 120         if (st->pending_esc) {
 121             st->pending_esc=False;
 122             switch(buf[i]) {
 123             case SLIP_ESCEND:
 124                 outputchr=SLIP_END;
 125                 break;
 126             case SLIP_ESCESC:
 127                 outputchr=SLIP_ESC;
 128                 break;
 129             default:
 130                 if (!st->ignoring_packet) {
 131                     Message(M_WARNING, "userv_afterpoll: bad SLIP escape"
 132                             " character, dropping packet\n");
 133                 }
 134                 st->ignoring_packet=True;
 135                 outputchr=OUTPUT_NOTHING;
 136                 break;
 137             }
 138         } else {
 139             switch (buf[i]) {
 140             case SLIP_END:
 141                 outputchr=OUTPUT_END;
 142                 break;
 143             case SLIP_ESC:
 144                 st->pending_esc=True;
 145                 outputchr=OUTPUT_NOTHING;
 146                 break;
 147             default:
 148                 outputchr=buf[i];
 149                 break;
 150             }
 151         }
 152
 153         if (st->ignoring_packet) {
 154             if (outputchr == OUTPUT_END) {
 155                 st->ignoring_packet=False;
 156                 st->buff->size=0;
 157             }
 158         } else {
 159             if (outputchr == OUTPUT_END) {
 160                 if (st->buff->size>0) {
 161                     st->netlink_to_tunnel(&st->nl,st->buff);
 162                     BUF_ALLOC(st->buff,"userv_afterpoll");
 163                 }
 164                 st->buff->size=0;
 165             } else if (outputchr != OUTPUT_NOTHING) {
 166                 if (buf_remaining_space(st->buff)) {
 167                     buf_append_uint8(st->buff,outputchr);
 168                 } else {
 169                     Message(M_WARNING, "userv_afterpoll: dropping overlong"
 170                             " SLIP packet\n");
 171                     st->ignoring_packet=True;
 172                 }
 173             }
 174         }
 175     }
 176 }
 177
 178 static void slip_init(struct slip *st, struct cloc loc, dict_t *dict,
 179                       cstring_t name, netlink_deliver_fn *to_host)
 180 {
 181     st->netlink_to_tunnel=
 182         netlink_init(&st->nl,st,loc,dict,
 183                      "netlink-userv-ipif",NULL,to_host);
 184     st->buff=find_cl_if(dict,"buffer",CL_BUFFER,True,"name",loc);
 185     BUF_ALLOC(st->buff,"slip_init");
 186     st->pending_esc=False;
 187     st->ignoring_packet=False;
 188 }
 189
 190 /* Connection to the kernel through userv-ipif */
 191
 192 struct userv {
 193     struct slip slip;
 194     int txfd; /* We transmit to userv */
 195     int rxfd; /* We receive from userv */
 196     cstring_t userv_path;
 197     cstring_t service_user;
 198     cstring_t service_name;
 199     pid_t pid;
 200     bool_t expecting_userv_exit;
 201 };
 202
 203 static int userv_beforepoll(void *sst, struct pollfd *fds, int *nfds_io,
 204                             int *timeout_io)
 205 {
 206     struct userv *st=sst;
 207
 208     if (st->rxfd!=-1) {
 209         BEFOREPOLL_WANT_FDS(2);
 210         fds[0].fd=st->txfd;
 211         fds[0].events=0; /* Might want to pick up POLLOUT sometime */
 212         fds[1].fd=st->rxfd;
 213         fds[1].events=POLLIN;
 214     } else {
 215         BEFOREPOLL_WANT_FDS(0);
 216     }
 217     return 0;
 218 }
 219
 220 static void userv_afterpoll(void *sst, struct pollfd *fds, int nfds)
 221 {
 222     struct userv *st=sst;
 223     uint8_t rxbuf[DEFAULT_BUFSIZE];
 224     int l;
 225
 226     if (nfds==0) return;
 227
 228     if (fds[1].revents&POLLERR) {
 229         Message(M_ERR,"%s: userv_afterpoll: POLLERR!\n",st->slip.nl.name);
 230     }
 231     if (fds[1].revents&POLLIN) {
 232         l=read(st->rxfd,rxbuf,DEFAULT_BUFSIZE);
 233         if (l<0) {
 234             if (errno!=EINTR && !iswouldblock(errno))
 235                 fatal_perror("%s: userv_afterpoll: read(rxfd)",
 236                              st->slip.nl.name);
 237         } else if (l==0) {
 238             fatal("%s: userv_afterpoll: read(rxfd)=0; userv gone away?",
 239                   st->slip.nl.name);
 240         } else slip_unstuff(&st->slip,rxbuf,l);
 241     }
 242 }
 243
 244 /* Send buf to the kernel. Free buf before returning. */
 245 static void userv_deliver_to_kernel(void *sst, struct buffer_if *buf)
 246 {
 247     struct userv *st=sst;
 248
 249     if (buf->size > st->slip.nl.mtu) {
 250         Message(M_ERR,"%s: packet of size %"PRIu32" exceeds mtu %"PRIu32":"
 251                 " cannot be injected into kernel, dropped\n",
 252                 st->slip.nl.name, buf->size, st->slip.nl.mtu);
 253         BUF_FREE(buf);
 254         return;
 255     }
 256
 257     slip_stuff(&st->slip,buf,st->txfd);
 258 }
 259
 260 static void userv_userv_callback(void *sst, pid_t pid, int status)
 261 {
 262     struct userv *st=sst;
 263
 264     if (pid!=st->pid) {
 265         Message(M_WARNING,"userv_callback called unexpectedly with pid %d "
 266                 "(expected %d)\n",pid,st->pid);
 267         return;
 268     }
 269     if (!(st->expecting_userv_exit &&
 270           (!status ||
 271            (WIFSIGNALED(status) && WTERMSIG(status)==SIGTERM)))) {
 272         lg_exitstatus(0,st->slip.nl.name,0,
 273                       st->expecting_userv_exit ? M_WARNING : M_FATAL,
 274                       status,"userv");
 275     }
 276     st->pid=0;
 277 }
 278
 279 struct userv_entry_rec {
 280     cstring_t path;
 281     const char **argv;
 282     int in;
 283     int out;
 284     /* XXX perhaps we should collect and log stderr? */
 285 };
 286
 287 static void userv_entry(void *sst)
 288 {
 289     struct userv_entry_rec *st=sst;
 290
 291     dup2(st->in,0);
 292     dup2(st->out,1);
 293
 294     setsid();
 295     execvp(st->path,(char *const*)st->argv);
 296     perror("userv-entry: execvp()");
 297     exit(1);
 298 }
 299
 300 static void userv_invoke_userv(struct userv *st)
 301 {
 302     struct userv_entry_rec er[1];
 303     int c_stdin[2];
 304     int c_stdout[2];
 305     string_t nets;
 306     string_t s;
 307     struct netlink_client *r;
 308     struct ipset *allnets;
 309     struct subnet_list *snets;
 310     int i, nread;
 311     uint8_t confirm;
 312
 313     if (st->pid) {
 314         fatal("userv_invoke_userv: already running");
 315     }
 316
 317     /* This is where we actually invoke userv - all the networks we'll
 318        be using should already have been registered. */
 319
 320     char addrs[512];
 321     snprintf(addrs,sizeof(addrs),"%s,%s,%d,slip",
 322              ipaddr_to_string(st->slip.nl.local_address),
 323              ipaddr_to_string(st->slip.nl.secnet_address),st->slip.nl.mtu);
 324
 325     allnets=ipset_new();
 326     for (r=st->slip.nl.clients; r; r=r->next) {
 327         if (r->link_quality > LINK_QUALITY_UNUSED) {
 328             struct ipset *nan;
 329             r->kup=True;
 330             nan=ipset_union(allnets,r->networks);
 331             ipset_free(allnets);
 332             allnets=nan;
 333         }
 334     }
 335     snets=ipset_to_subnet_list(allnets);
 336     ipset_free(allnets);
 337     nets=safe_malloc(20*snets->entries,"userv_invoke_userv:nets");
 338     *nets=0;
 339     for (i=0; i<snets->entries; i++) {
 340         s=subnet_to_string(snets->list[i]);
 341         strcat(nets,s);
 342         strcat(nets,",");
 343     }
 344     nets[strlen(nets)-1]=0;
 345     subnet_list_free(snets);
 346
 347     Message(M_INFO,"%s: about to invoke: %s %s %s %s %s\n",st->slip.nl.name,
 348             st->userv_path,st->service_user,st->service_name,addrs,nets);
 349
 350     st->slip.pending_esc=False;
 351
 352     /* Invoke userv */
 353     pipe_cloexec(c_stdin);
 354     pipe_cloexec(c_stdout);
 355     st->txfd=c_stdin[1];
 356     st->rxfd=c_stdout[0];
 357
 358     er->in=c_stdin[0];
 359     er->out=c_stdout[1];
 360     /* The arguments are:
 361        userv
 362        service-user
 363        service-name
 364        local-addr,secnet-addr,mtu,protocol
 365        route1,route2,... */
 366     const char *er_argv[6];
 367     er->argv=er_argv;
 368     er->argv[0]=st->userv_path;
 369     er->argv[1]=st->service_user;
 370     er->argv[2]=st->service_name;
 371     er->argv[3]=addrs;
 372     er->argv[4]=nets;
 373     er->argv[5]=NULL;
 374     er->path=st->userv_path;
 375
 376     st->pid=makesubproc(userv_entry, userv_userv_callback,
 377                         er, st, st->slip.nl.name);
 378     close(er->in);
 379     close(er->out);
 380     free(nets);
 381     Message(M_INFO,"%s: userv-ipif pid is %d\n",st->slip.nl.name,st->pid);
 382     /* Read a single character from the pipe to confirm userv-ipif is
 383        running. If we get a SIGCHLD at this point then we'll get EINTR. */
 384     if ((nread=read(st->rxfd,&confirm,1))!=1) {
 385         if (errno==EINTR) {
 386             Message(M_WARNING,"%s: read of confirmation byte was "
 387                     "interrupted\n",st->slip.nl.name);
 388         } else {
 389             if (nread<0) {
 390                 fatal_perror("%s: error reading confirmation byte",
 391                              st->slip.nl.name);
 392             } else {
 393                 fatal("%s: unexpected EOF instead of confirmation byte"
 394                       " - userv ipif failed?", st->slip.nl.name);
 395             }
 396         }
 397     } else {
 398         if (confirm!=SLIP_END) {
 399             fatal("%s: bad confirmation byte %d from userv-ipif",
 400                   st->slip.nl.name,confirm);
 401         }
 402     }
 403     setnonblock(st->txfd);
 404     setnonblock(st->rxfd);
 405
 406     add_hook(PHASE_CHILDPERSIST,childpersist_closefd_hook,&st->txfd);
 407     add_hook(PHASE_CHILDPERSIST,childpersist_closefd_hook,&st->rxfd);
 408 }
 409
 410 static void userv_kill_userv(struct userv *st)
 411 {
 412     if (st->pid) {
 413         kill(-st->pid,SIGTERM);
 414         st->expecting_userv_exit=True;
 415     }
 416 }
 417
 418 static void userv_phase_hook(void *sst, uint32_t newphase)
 419 {
 420     struct userv *st=sst;
 421     /* We must wait until signal processing has started before forking
 422        userv */
 423     if (newphase==PHASE_RUN) {
 424         userv_invoke_userv(st);
 425         /* Register for poll() */
 426         register_for_poll(st, userv_beforepoll, userv_afterpoll,
 427                           st->slip.nl.name);
 428     }
 429     if (newphase==PHASE_SHUTDOWN) {
 430         userv_kill_userv(st);
 431     }
 432 }
 433
 434 static list_t *userv_apply(closure_t *self, struct cloc loc, dict_t *context,
 435                            list_t *args)
 436 {
 437     struct userv *st;
 438     item_t *item;
 439     dict_t *dict;
 440
 441     NEW(st);
 442
 443     /* First parameter must be a dict */
 444     item=list_elem(args,0);
 445     if (!item || item->type!=t_dict)
 446         cfgfatal(loc,"userv-ipif","parameter must be a dictionary\n");
 447
 448     dict=item->data.dict;
 449
 450     slip_init(&st->slip,loc,dict,"netlink-userv-ipif",
 451               userv_deliver_to_kernel);
 452
 453     st->userv_path=dict_read_string(dict,"userv-path",False,"userv-netlink",
 454                                     loc);
 455     st->service_user=dict_read_string(dict,"service-user",False,
 456                                       "userv-netlink",loc);
 457     st->service_name=dict_read_string(dict,"service-name",False,
 458                                       "userv-netlink",loc);
 459     if (!st->userv_path) st->userv_path="userv";
 460     if (!st->service_user) st->service_user="root";
 461     if (!st->service_name) st->service_name="ipif";
 462     st->rxfd=-1; st->txfd=-1;
 463     st->pid=0;
 464     st->expecting_userv_exit=False;
 465     add_hook(PHASE_RUN,userv_phase_hook,st);
 466     add_hook(PHASE_SHUTDOWN,userv_phase_hook,st);
 467
 468     return new_closure(&st->slip.nl.cl);
 469 }
 470
 471 void slip_module(dict_t *dict)
 472 {
 473     add_closure(dict,"userv-ipif",userv_apply);
 474 }