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