mdw@git.distorted.org.uk Git - userv-utils/blob - ipif/service.c

   1 /*
   2  * userv service (or standalone program)
   3  * for per-user IP subranges.
   4  *
   5  * This is invoked as root, directly from userv.
   6  * Its arguments are supposed to be, in order:
   7  *  <config>
   8  *      Specifies address ranges and gids which own them.
   9  *  --  Indicates that the remaining arguments are user-supplied
  10  *      and therefore untrusted.
  11  *  <local-addr>,<peer-addr>,<mtu>,<proto>
  12  *      As for slattach.  Supported protocols are slip, cslip, and
  13  *      adaptive.  Alternatively, set to `debug' to print debugging
  14  *      info.  <local-addr> is address of the interface on chiark;
  15  *      <peer-addr> is the address of the point-to-point peer.
  16  *  <prefix>/<mask>,<prefix>/<mask>,...
  17  *      List of additional routes to add for this interface.
  18  *      May be the empty argument.
  19  *
  20  * <config> is either
  21  *    <gid>,<prefix>/<len>[,<junk>]
  22  *      indicating that that gid may allocate addresses in
  23  *      the relevant subspace (<junk> is ignored)
  24  * or #...
  25  *      which is a comment
  26  * or /<config-file-name> or ./<config-file-name> or ../<config-file-name>
  27  *      which refers to a file which contains lines which
  28  *      are each <config>
  29  * or *
  30  *      which means that anything is permitted
  31  *
  32  * Should be run from userv with no-disconnect-hup.
  33  */
  34
  35 #include <stdio.h>
  36 #include <string.h>
  37 #include <stdlib.h>
  38 #include <assert.h>
  39 #include <errno.h>
  40 #include <stdarg.h>
  41 #include <ctype.h>
  42 #include <limits.h>
  43
  44 #define NARGS 4
  45 #define MAXEXROUTES 5
  46 #define ATXTLEN 12
  47
  48 static const unsigned long gidmaxval= (unsigned long)((gid_t)-2);
  49 static const char *const protos_ok[]= { "slip", "cslip", "adaptive", 0 };
  50
  51 static const char *configstr, *proto;
  52 static unsigned long localaddr, peeraddr, mtu;
  53 static int localallow, peerallow, allallow;
  54 static int nexroutes;
  55 static struct exroute {
  56   unsigned long prefix, mask;
  57   int allow;
  58   char prefixtxt[ATXTLEN], masktxt[ATXTLEN];
  59 } exroutes[MAXEXROUTES];
  60
  61 static char localtxt[ATXTLEN];
  62 static char peertxt[ATXTLEN];
  63
  64 static struct pplace {
  65   struct pplace *parent;
  66   const char *filename;
  67   int lineno;
  68 } *cpplace;
  69
  70 static void fatal(const char *fmt, ...)
  71      __attribute__((format(printf,1,2)));
  72 static void fatal(const char *fmt, ...) {
  73   va_list al;
  74   va_start(al,fmt);
  75
  76   fputs("userv-ipif service: fatal error: ",stderr);
  77   vfprintf(stderr, fmt, al);
  78   putc('\n',stderr);
  79   exit(8);
  80 }
  81
  82 static void sysfatal(const char *fmt, ...)
  83      __attribute__((format(printf,1,2)));
  84 static void sysfatal(const char *fmt, ...) {
  85   va_list al;
  86   int e;
  87
  88   e= errno;
  89   va_start(al,fmt);
  90
  91   fputs("userv-ipif service: fatal system error",stderr);
  92   vfprintf(stderr, fmt, al);
  93   fprintf(stderr,"%s\n", strerror(e));
  94   exit(12);
  95 }
  96
  97
  98 static void badusage(const char *fmt, ...)
  99      __attribute__((format(printf,1,2)));
 100 static void badusage(const char *fmt, ...) {
 101   va_list al;
 102   struct pplace *cpp;
 103
 104   if (cpplace) {
 105     fprintf(stderr,
 106             "userv-ipif service: %s:%d: ",
 107             cpplace->filename, cpplace->lineno);
 108   } else {
 109     fputs("userv-ipif service: invalid usage: ",stderr);
 110   }
 111   va_start(al,fmt);
 112   vfprintf(stderr, fmt, al);
 113   putc('\n',stderr);
 114
 115   if (cpplace) {
 116     for (cpp=cpplace->parent; cpp; cpp=cpp->parent) {
 117       fprintf(stderr,
 118               "userv-ipif service: %s:%d: ... in file included from here\n",
 119               cpp->filename, cpp->lineno);
 120     }
 121   }
 122   exit(16);
 123 }
 124
 125 static char *ip2txt(unsigned long addr, char *buf) {
 126   sprintf(buf, "%lu.%lu.%lu.%lu",
 127           (addr>>24) & 0x0ff,
 128           (addr>>16) & 0x0ff,
 129           (addr>>8) & 0x0ff,
 130           (addr) & 0x0ff);
 131   return buf;
 132 }
 133
 134 static unsigned long eat_number(const char **argp, const char *what,
 135                                 unsigned long min, unsigned long max,
 136                                 const char *endchars, int *endchar_r) {
 137   /* If !endchars then the endchar must be a nul, otherwise it may be
 138    * a nul (resulting in *argp set to 0) or something else (*argp set
 139    * to point to after delim, *endchar_r set to delim).
 140    * *endchar_r may be 0.
 141    */
 142   unsigned long rv;
 143   char *ep;
 144   int endchar;
 145
 146   if (!*argp) { badusage("missing number %s\n",what); }
 147   rv= strtoul(*argp,&ep,0);
 148   if ((endchar= *ep)) {
 149     if (!endchars) badusage("junk after number %s\n",what);
 150     if (!strchr(endchars,endchar))
 151       badusage("invalid character or delimiter `%c' in or after number, %s:"
 152                " expected %s (or none?)\n", endchar,what,endchars);
 153     *argp= ep+1;
 154   } else {
 155     *argp= 0;
 156   }
 157   if (endchar_r) *endchar_r= endchar;
 158   if (rv < min || rv > max) badusage("number %s value %lu out of range %lu..%lu",
 159                                      what, rv, min, max);
 160   return rv;
 161 }
 162
 163 static void addrnet_mustdiffer(const char *w1, unsigned long p1, unsigned long m1,
 164                                const char *w2, unsigned long p2, unsigned long m2) {
 165   unsigned long mask;
 166
 167   mask= m1&m2;
 168   if ((p1 & mask) != (p2 & mask)) return;
 169   badusage("%s %08lx/%08lx overlaps/clashes with %s %08lx/%08lx",
 170            w1,p1,m1, w2,p2,m2);
 171 }
 172
 173 static unsigned long eat_addr(const char **argp, const char *what,
 174                               const char *endchars, int *endchar_r) {
 175   char whatbuf[100];
 176   unsigned long rv;
 177   int i;
 178
 179   for (rv=0, i=0;
 180        i<4;
 181        i++) {
 182     rv <<= 8;
 183     sprintf(whatbuf,"%s byte #%d",what,i);
 184     rv |= eat_number(argp,whatbuf, 0,255, i<3 ? "." : endchars, endchar_r);
 185   }
 186
 187   return rv;
 188 }
 189
 190 static void eat_prefixmask(const char **argp, const char *what,
 191                            const char *endchars, int *endchar_r,
 192                            unsigned long *prefix_r, unsigned long *mask_r, int *len_r) {
 193   /* mask_r and len_r may be 0 */
 194   char whatbuf[100];
 195   int len;
 196   unsigned long prefix, mask;
 197
 198   prefix= eat_addr(argp,what, "/",0);
 199   sprintf(whatbuf,"%s length",what);
 200   len= eat_number(argp,whatbuf, 0,32, endchars,endchar_r);
 201
 202   mask= (~0UL << (32-len));
 203   if (prefix & ~mask) badusage("%s prefix %08lx not fully contained in mask %08lx\n",
 204                                what,prefix,mask);
 205   *prefix_r= prefix;
 206   if (mask_r) *mask_r= mask;
 207   if (len_r) *len_r= len;
 208 }
 209
 210 static int addrnet_isin(unsigned long prefix, unsigned long mask,
 211                         unsigned long mprefix, unsigned long mmask) {
 212   return  !(~mask & mmask)  &&  (prefix & mmask) == mprefix;
 213 }
 214
 215
 216 static void permit(unsigned long pprefix, unsigned long pmask) {
 217   int i, any;
 218
 219   assert(!(pprefix & ~pmask));
 220
 221   if (!proto) fputs("permits",stdout);
 222   if (addrnet_isin(localaddr,~0UL, pprefix,pmask)) {
 223     if (!proto) fputs(" local-addr",stdout);
 224     any= localallow= 1;
 225   }
 226   if (addrnet_isin(peeraddr,~0UL, pprefix,pmask)) {
 227     if (!proto) fputs(" peer-addr",stdout);
 228     any= peerallow= 1;
 229   }
 230   for (i=0; i<nexroutes; i++) {
 231     if (addrnet_isin(exroutes[i].prefix,exroutes[i].mask, pprefix,pmask)) {
 232       if (!proto) printf(" route#%d",i);
 233       any= exroutes[i].allow= 1;
 234     }
 235   }
 236   if (!proto) {
 237     if (!any) fputs(" nothing!",stderr);
 238     putchar('\n');
 239   }
 240 }
 241
 242 static void pconfig(const char *configstr, int truncated);
 243
 244 static void pfile(const char *filename) {
 245   FILE *file;
 246   char buf[PATH_MAX];
 247   int l, truncated, c;
 248   struct pplace npp, *cpp;
 249
 250   for (cpp=cpplace; cpp; cpp=cpp->parent) {
 251     if (!strcmp(cpp->filename,filename))
 252       badusage("recursive configuration file `%s'",filename);
 253   }
 254
 255   file= fopen(filename,"r");
 256   if (!file)
 257     badusage("cannot open configuration file `%s': %s", filename, strerror(errno));
 258
 259   if (!proto) printf("config file `%s':\n",filename);
 260
 261   npp.parent= cpplace;
 262   npp.filename= filename;
 263   npp.lineno= 0;
 264   cpplace= &npp;
 265
 266   while (fgets(buf, sizeof(buf), file)) {
 267     npp.lineno++;
 268     l= strlen(buf);
 269     if (!l) continue;
 270
 271     truncated= (buf[l-1] != '\n');
 272     while (l>0 && isspace((unsigned char) buf[l-1])) l--;
 273     if (!l) continue;
 274     buf[l]= 0;
 275
 276     if (truncated) {
 277       while ((c= getc(file)) != EOF && c != '\n');
 278       if (c == EOF) break;
 279     }
 280
 281     pconfig(buf,truncated);
 282   }
 283   if (ferror(file))
 284     badusage("failed while reading configuration file: %s", strerror(errno));
 285
 286   cpplace= npp.parent;
 287 }
 288
 289 static void pconfig(const char *configstr, int truncated) {
 290   unsigned long fgid, tgid, pprefix, pmask;
 291   int plen;
 292   char ptxt[ATXTLEN];
 293   const char *gidlist;
 294
 295   switch (configstr[0]) {
 296   case '*':
 297     if (strcmp(configstr,"*")) badusage("`*' directive must be only thing on line");
 298     permit(0UL,0UL);
 299     return;
 300
 301   case '#':
 302     return;
 303
 304   case '/': case '.':
 305     if (truncated) badusage("filename too long (`%.100s...')",configstr);
 306     pfile(configstr);
 307     return;
 308
 309   default:
 310     if (!isdigit((unsigned char)configstr[0]))
 311       badusage("unknown configuration directive");
 312
 313     fgid= eat_number(&configstr,"gid", 0,gidmaxval, ",",0);
 314     eat_prefixmask(&configstr,"permitted-prefix", ",",0, &pprefix,&pmask,&plen);
 315     if (!configstr && truncated) badusage("gid,prefix/len,... spec too long");
 316
 317     if (!proto) printf(" %5lu,%s/%d: ", fgid, ip2txt(pprefix,ptxt), plen);
 318
 319     gidlist= getenv("USERV_GID");
 320     if (!gidlist) fatal("USERV_GID not set");
 321     for (;;) {
 322       if (!gidlist) {
 323         if (!proto) printf("no matching gid\n");
 324         return;
 325       }
 326       tgid= eat_number(&gidlist,"userv-gid", 0,gidmaxval, " ",0);
 327       if (tgid == fgid) break;
 328     }
 329     permit(pprefix,pmask);
 330     return;
 331   }
 332 }
 333
 334 static void checkallow(int allow, const char *what,
 335                        const char *prefixtxt, const char *masktxt) {
 336   if (allow) return;
 337   fprintf(stderr,"userv-ipif service: access denied for %s, %s/%s\n",
 338           what, prefixtxt, masktxt);
 339   allallow= 0;
 340 }
 341
 342 static void parseargs(int argc, const char *const *argv) {
 343   unsigned long routeaddr, routemask;
 344   const char *carg;
 345   const char *const *cprotop;
 346   int i;
 347   char erwhatbuf[100], erwhatbuf2[100];
 348
 349   if (argc < NARGS+1) { badusage("too few arguments"); }
 350   if (argc > NARGS+1) { badusage("too many arguments"); }
 351
 352   configstr= *++argv;
 353
 354   carg= *++argv;
 355   if (strcmp(carg,"--")) badusage("separator argument `--' not found, got `%s'",carg);
 356
 357   carg= *++argv;
 358   localaddr= eat_addr(&carg,"local-addr", ",",0);
 359   peeraddr= eat_addr(&carg,"peer-addr", ",",0);
 360   mtu= eat_number(&carg,"mtu", 576,65536, ",",0);
 361   localallow= peerallow= 0;
 362
 363   if (!strcmp(carg,"debug")) {
 364     proto= 0;
 365   } else {
 366     for (cprotop= protos_ok;
 367          (proto= *cprotop) && strcmp(proto,carg);
 368          cprotop++);
 369     if (!proto) fatal("invalid protocol");
 370   }
 371
 372   addrnet_mustdiffer("local-addr",localaddr,~0UL, "peer-addr",peeraddr,~0UL);
 373
 374   carg= *++argv;
 375   for (nexroutes=0;
 376        carg;
 377        nexroutes++) {
 378     if (nexroutes == MAXEXROUTES)
 379       fatal("too many extra routes (only %d allowed)",MAXEXROUTES);
 380     sprintf(erwhatbuf,"route#%d",nexroutes);
 381
 382     eat_prefixmask(&carg,erwhatbuf, ",",0, &routeaddr,&routemask,0);
 383     if (routemask == ~0UL) {
 384       addrnet_mustdiffer(erwhatbuf,routeaddr,routemask, "local-addr",localaddr,~0UL);
 385       addrnet_mustdiffer(erwhatbuf,routeaddr,routemask, "peer-addr",peeraddr,~0UL);
 386     }
 387     for (i=0; i<nexroutes; i++) {
 388       sprintf(erwhatbuf2,"route#%d",i);
 389       addrnet_mustdiffer(erwhatbuf,routeaddr,routemask,
 390                          erwhatbuf2,exroutes[i].prefix,exroutes[i].mask);
 391     }
 392     exroutes[nexroutes].prefix= routeaddr;
 393     exroutes[nexroutes].mask= routemask;
 394     exroutes[nexroutes].allow= 0;
 395     ip2txt(routeaddr,exroutes[nexroutes].prefixtxt);
 396     ip2txt(routemask,exroutes[nexroutes].masktxt);
 397   }
 398   ip2txt(localaddr,localtxt);
 399   ip2txt(peeraddr,peertxt);
 400 }
 401
 402 static void checkpermit(void) {
 403   int i;
 404   char erwhatbuf[100];
 405
 406   allallow= 1;
 407   checkallow(localallow,"local-addr", localtxt,"32");
 408   checkallow(peerallow,"peer-addr", peertxt,"32");
 409   for (i=0; i<nexroutes; i++) {
 410     sprintf(erwhatbuf, "route#%d", i);
 411     checkallow(exroutes[i].allow, erwhatbuf, exroutes[i].prefixtxt, exroutes[i].masktxt);
 412   }
 413   if (!allallow) fatal("access denied");
 414 }
 415
 416 static void dumpdebug(void) __attribute__((noreturn));
 417 static void dumpdebug(void) {
 418   int i;
 419   char erwhatbuf[100];
 420
 421   printf("protocol: debug\n"
 422          "local:    %08lx == %s\n"
 423          "peer:     %08lx == %s\n"
 424          "mtu:      %ld\n"
 425          "routes:   %d\n",
 426          localaddr, localtxt,
 427          peeraddr, peertxt,
 428          mtu,
 429          nexroutes);
 430   for (i=0; i<nexroutes; i++) {
 431     sprintf(erwhatbuf, "route#%d:", i);
 432     printf("%-9s %08lx/%08lx == %s/%s\n",
 433            erwhatbuf,
 434            exroutes[i].prefix, exroutes[i].mask,
 435            exroutes[i].prefixtxt, exroutes[i].masktxt);
 436   }
 437   if (ferror(stdout) || fclose(stdout)) sysfatal("flush stdout");
 438   exit(0);
 439 }
 440
 441 int main(int argc, const char *const *argv) {
 442   parseargs(argc,argv);
 443   pconfig(configstr,0);
 444   checkpermit();
 445   if (!proto) dumpdebug();
 446
 447   abort();
 448 }