mdw@git.distorted.org.uk Git - yaid/blob - policy.c

   1 /* -*-c-*-
   2  *
   3  * Policy parsing and implementation
   4  *
   5  * (c) 2012 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Yet Another Ident Daemon (YAID).
  11  *
  12  * YAID is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * YAID is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with YAID; if not, write to the Free Software Foundation,
  24  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25  */
  26
  27 /*----- Header files ------------------------------------------------------*/
  28
  29 #include "yaid.h"
  30
  31 /*----- Memory management -------------------------------------------------*/
  32
  33 /* Initialize a policy structure.  In this state, it doesn't actually have
  34  * any resources allocated (so can be simply discarded) but it's safe to free
  35  * (using `free_policy').
  36  */
  37 void init_policy(struct policy *p) { p->act.act = A_LIMIT; }
  38
  39 /* Free an action structure, resetting it to a safe state.  This function is
  40  * idempotent.
  41  */
  42 static void free_action(struct action *a)
  43 {
  44   switch (a->act) {
  45     case A_LIE:
  46       xfree(a->u.lie);
  47       break;
  48   }
  49   a->act = A_LIMIT;
  50 }
  51
  52 /* Free a policy structure, resetting it to its freshly-initialized state.
  53  * This function is idempotent.
  54  */
  55 void free_policy(struct policy *p)
  56   { free_action(&p->act); }
  57
  58 /*----- Diagnostics -------------------------------------------------------*/
  59
  60 static void print_addrpat(const struct addrops *ao, const struct addrpat *ap)
  61 {
  62   char buf[ADDRLEN];
  63
  64   if (ap->len == 0)
  65     putchar('*');
  66   else {
  67     printf("%s/%u",
  68            inet_ntop(ao->af, &ap->addr, buf, sizeof(buf)),
  69            ap->len);
  70   }
  71 }
  72
  73 static void print_portpat(const struct portpat *pp)
  74 {
  75   if (pp->lo == 0 && pp->hi == 65535) putchar('*');
  76   else if (pp->lo == pp->hi) printf("%u", pp->lo);
  77   else printf("%u-%u", pp->lo, pp->hi);
  78 }
  79
  80 static void print_sockpat(const struct addrops *ao, const struct sockpat *sp)
  81   { print_addrpat(ao, &sp->addr); putchar(' '); print_portpat(&sp->port); }
  82
  83 static const char *const acttab[] = {
  84 #define DEFACT(tag, name) name,
  85   ACTIONS(DEFACT)
  86 #undef DEFACT
  87   0
  88 };
  89
  90 static void print_action(const struct action *act)
  91 {
  92   assert(act->act < A_LIMIT);
  93   printf("%s", acttab[act->act]);
  94   switch (act->act) {
  95     case A_USER: {
  96       int i;
  97       unsigned m;
  98       for (i = 0, m = 1; i < A_LIMIT; i++, m <<= 1)
  99         if (act->u.user & m) printf(" %s", acttab[i]);
 100     } break;
 101     case A_LIE:
 102       printf(" %s", act->u.lie);
 103       break;
 104   }
 105 }
 106
 107 /* Print a policy rule to standard output. */
 108 void print_policy(const struct policy *p)
 109 {
 110   print_sockpat(p->ao, &p->sp[L]); putchar(' ');
 111   print_sockpat(p->ao, &p->sp[R]); putchar(' ');
 112   print_action(&p->act); putchar('\n');
 113 }
 114
 115 /*----- Matching ----------------------------------------------------------*/
 116
 117 /* Return true if the port matches the pattern. */
 118 static int match_portpat(const struct portpat *pp, unsigned port)
 119   { return (pp->lo <= port && port <= pp->hi); }
 120
 121 /* Return true if the socket matches the pattern. */
 122 static int match_sockpat(const struct addrops *ao,
 123                          const struct sockpat *sp, const struct socket *s)
 124 {
 125   return (ao->match_addrpat(&sp->addr, &s->addr) &&
 126           match_portpat(&sp->port, s->port));
 127 }
 128
 129 /* Return true if the query matches the patterns in the policy rule. */
 130 int match_policy(const struct policy *p, const struct query *q)
 131 {
 132   return ((!p->ao || p->ao == q->ao) &&
 133           match_sockpat(q->ao, &p->sp[L], &q->s[L]) &&
 134           match_sockpat(q->ao, &p->sp[R], &q->s[R]));
 135 }
 136
 137 /*----- Parsing -----------------------------------------------------------*/
 138
 139 /* Advance FP to the next line. */
 140 static void nextline(FILE *fp)
 141 {
 142   for (;;) {
 143     int ch = getc(fp);
 144     if (ch == '\n' || ch == EOF) break;
 145   }
 146 }
 147
 148 /* Scan a whitespace-separated token from FP, writing it to BUF.  The token
 149  * must fit in a buffer of size SZ, including a terminating null.  Return
 150  * an appropriate T_* error code.
 151  */
 152 static int scan(FILE *fp, char *buf, size_t sz)
 153 {
 154   int ch;
 155
 156 skip_ws:
 157   /* Before we start grabbing a token proper, find out what's in store. */
 158   ch = getc(fp);
 159   switch (ch) {
 160
 161     case '\n':
 162     newline:
 163       /* Found a newline.  Leave it where it is and report it. */
 164       ungetc(ch, fp);
 165       return (T_EOL);
 166
 167     case EOF:
 168     eof:
 169       /* Found end-of-file, or an I/O error.  Return an appropriate code. */
 170       return (ferror(fp) ? T_ERROR : T_EOF);
 171
 172     case '#':
 173       /* Found a comment.  Consume it, and continue appropriately: it must
 174        * be terminated either by a newline or end-of-file.
 175        */
 176       for (;;) {
 177         ch = getc(fp);
 178         if (ch == '\n') goto newline;
 179         else if (ch == EOF) goto eof;
 180       }
 181
 182     default:
 183       /* Whitespace means we just continue around.  Anything else and we
 184        * start snarfing.
 185        */
 186       if (isspace(ch)) goto skip_ws;
 187       break;
 188   }
 189
 190   for (;;) {
 191
 192     /* If there's buffer space left, store the character. */
 193     if (sz) { *buf++ = ch; sz--; }
 194
 195     /* Get a new one, and find out what to do about it. */
 196     ch = getc(fp);
 197     switch (ch) {
 198       case '\n':
 199         ungetc(ch, fp);
 200         goto done;
 201       case EOF:
 202         goto done;
 203       default:
 204         if (isspace(ch)) goto done;
 205         break;
 206     }
 207   }
 208
 209 done:
 210   /* If there's no space for a terminating null then report an error. */
 211   if (!sz) return (T_ERROR);
 212
 213   /* All done. */
 214   *buf++ = 0; sz--;
 215   return (T_OK);
 216 }
 217
 218 /* Parse an action name, storing the code in *ACT.  Return an appropriate T_*
 219  * code.
 220  */
 221 static int parse_actname(FILE *fp, unsigned *act)
 222 {
 223   char buf[32];
 224   int t;
 225   const char *const *p;
 226
 227   if ((t = scan(fp, buf, sizeof(buf))) != 0) return (t);
 228   for (p = acttab; *p; p++)
 229     if (strcmp(buf, *p) == 0) { *act = p - acttab; return (0); }
 230   return (T_ERROR);
 231 }
 232
 233 /* Parse an action, returning a T_* code. */
 234 static int parse_action(FILE *fp, struct action *act)
 235 {
 236   char buf[32];
 237   int t;
 238   unsigned a;
 239   unsigned long m;
 240
 241   /* Collect the action name. */
 242   if ((t = parse_actname(fp, &a)) != 0) return (t);
 243
 244   /* Parse parameters, if there are any. */
 245   switch (a) {
 246
 247     case A_USER:
 248       /* `user ACTION ACTION ...': store permitted actions in a bitmask. */
 249       m = 0;
 250       for (;;) {
 251         if ((t = parse_actname(fp, &a)) != 0) break;
 252         m |= (1 << a);
 253       }
 254       if (t != T_EOL && t != T_EOF) return (t);
 255       act->act = A_USER;
 256       act->u.user = m;
 257       break;
 258
 259     case A_TOKEN:
 260     case A_NAME:
 261     case A_DENY:
 262     case A_HIDE:
 263       /* Dull actions which don't accept parameters. */
 264       act->act = a;
 265       break;
 266
 267     case A_LIE:
 268       /* `lie NAME': store the string we're to report. */
 269       if ((t = scan(fp, buf, sizeof(buf))) != 0) return (t);
 270       act->act = a;
 271       act->u.lie = xstrdup(buf);
 272       break;
 273   }
 274
 275   /* Make sure we've reached the end of the line. */
 276   t = scan(fp, buf, sizeof(buf));
 277   if (t != T_EOF && t != T_EOL) {
 278     free_action(act);
 279     return (T_ERROR);
 280   }
 281
 282   /* Done. */
 283   return (0);
 284 }
 285
 286 /* Parse an address pattern, writing it to AP.  If the pattern has an
 287  * identifiable address family, update *AOP to point to its operations table;
 288  * if *AOP is already set to something different then report an error.
 289  */
 290 static int parse_addrpat(FILE *fp, const struct addrops **aop,
 291                          struct addrpat *ap)
 292 {
 293   char buf[64];
 294   int t;
 295   const struct addrops *ao;
 296   long n;
 297   char *delim;
 298
 299   /* Scan a token for the address pattern. */
 300   if ((t = scan(fp, buf, sizeof(buf))) != 0) return (t);
 301
 302   /* If this is a wildcard, then leave everything as it is. */
 303   if (strcmp(buf, "*") == 0) {
 304     ap->len = 0;
 305     return (T_OK);
 306   }
 307
 308   /* Decide what kind of address this must be.  A bit grim, sorry. */
 309   if (strchr(buf, ':'))
 310     ao = &addroptab[ADDR_IPV6];
 311   else
 312     ao = &addroptab[ADDR_IPV4];
 313
 314   /* Update the caller's idea of the address family in use. */
 315   if (!*aop) *aop = ao;
 316   else if (*aop != ao) return (T_ERROR);
 317
 318   /* See whether there's a prefix length.  If so, clobber it. */
 319   delim = strchr(buf, '/');
 320   if (delim) *delim++ = 0;
 321
 322   /* Parse the address. */
 323   if (!inet_pton(ao->af, buf, &ap->addr)) return (T_ERROR);
 324
 325   /* Parse the prefix length, or use the maximum one. */
 326   if (!delim) n = ao->len;
 327   else n = strtol(delim, 0, 10);
 328   if (n < 0 || n > ao->len) return (T_ERROR);
 329   ap->len = n;
 330
 331   /* Done. */
 332   return (T_OK);
 333 }
 334
 335 static int parse_portpat(FILE *fp, struct portpat *pp)
 336 {
 337   char buf[64];
 338   int t;
 339   long n;
 340   char *delim;
 341
 342   /* Parse a token for the pattern. */
 343   if ((t = scan(fp, buf, sizeof(buf))) != 0) return (T_ERROR);
 344
 345   /* If this is a wildcard, then we're done. */
 346   if (strcmp(buf, "*") == 0) {
 347     pp->lo = 0;
 348     pp->hi = 65535;
 349     return (T_OK);
 350   }
 351
 352   /* Find a range delimiter. */
 353   delim = strchr(buf, '-');
 354   if (delim) *delim++ = 0;
 355
 356   /* Parse the only or low end of the range. */
 357   n = strtol(buf, 0, 0);
 358   if (n < 0 || n > 65535) return (T_ERROR);
 359   pp->lo = n;
 360
 361   /* If there's no delimiter, then the high end is equal to the low end;
 362    * otherwise, parse the high end.
 363    */
 364   if (!delim)
 365     pp->hi = n;
 366   else {
 367     n = strtol(delim, 0, 0);
 368     if (n < pp->lo || n > 65535) return (T_ERROR);
 369     pp->hi = n;
 370   }
 371
 372   /* Done. */
 373   return (T_OK);
 374 }
 375
 376 /* Parse a socket pattern, writing it to SP. */
 377 static int parse_sockpat(FILE *fp, const struct addrops **aop,
 378                          struct sockpat *sp)
 379 {
 380   int t;
 381
 382   if ((t = parse_addrpat(fp, aop, &sp->addr)) != 0) return (t);
 383   if ((t = parse_portpat(fp, &sp->port)) != 0) return (T_ERROR);
 384   return (T_OK);
 385 }
 386
 387 /* Parse a policy rule line, writing it to P. */
 388 static int parse_policy(FILE *fp, struct policy *p)
 389 {
 390   int t;
 391
 392   p->ao = 0;
 393   free_policy(p);
 394
 395   if ((t = parse_sockpat(fp, &p->ao, &p->sp[L])) != 0) goto fail;
 396   if ((t = parse_sockpat(fp, &p->ao, &p->sp[R])) != 0) goto err;
 397   if ((t = parse_action(fp, &p->act)) != 0) goto err;
 398   return (0);
 399
 400 err:
 401   t = T_ERROR;
 402 fail:
 403   free_policy(p);
 404   return (t);
 405 }
 406
 407 /* Open a policy file by NAME.  The description WHAT and query Q are used for
 408  * formatting error messages for the log.
 409  */
 410 int open_policy_file(struct policy_file *pf, const char *name,
 411                      const char *what, const struct query *q)
 412 {
 413   if ((pf->fp = fopen(name, "r")) == 0) {
 414     logmsg(q, LOG_ERR, "failed to open %s `%s': %s",
 415            what, name, strerror(errno));
 416     return (-1);
 417   }
 418
 419   pf->name = name;
 420   pf->what = what;
 421   pf->q = q;
 422   pf->err = 0;
 423   pf->lno = 0;
 424   init_policy(&pf->p);
 425   return (0);
 426 }
 427
 428 /* Read a policy rule from the file, storing it in PF->p.  Return one of the
 429  * T_* codes.
 430  */
 431 int read_policy_file(struct policy_file *pf)
 432 {
 433   int t;
 434
 435   for (;;) {
 436     pf->lno++;
 437     t = parse_policy(pf->fp, &pf->p);
 438     switch (t) {
 439       case T_OK:
 440         nextline(pf->fp);
 441         return (0);
 442       case T_ERROR:
 443         logmsg(pf->q, LOG_ERR, "%s:%d: parse error in %s",
 444                pf->name, pf->lno, pf->what);
 445         pf->err = 1;
 446         break;
 447       case T_EOF:
 448         if (ferror(pf->fp)) {
 449           logmsg(pf->q, LOG_ERR, "failed to read %s `%s': %s",
 450                  pf->what, pf->name, strerror(errno));
 451         }
 452         return (-1);
 453       case T_EOL:
 454         nextline(pf->fp);
 455         break;
 456       default:
 457         abort();
 458     }
 459   }
 460 }
 461
 462 /* Close a policy file.  It doesn't matter whether the file was completely
 463  * read.
 464  */
 465 void close_policy_file(struct policy_file *pf)
 466 {
 467   fclose(pf->fp);
 468   free_policy(&pf->p);
 469 }
 470
 471 /* Load a policy file, writing a vector of records into PV.  If the policy
 472  * file has errors, then leave PV unchanged and return nonzero.
 473  */
 474 int load_policy_file(const char *file, policy_v *pv)
 475 {
 476   struct policy_file pf;
 477   policy_v v = DA_INIT;
 478
 479   if (open_policy_file(&pf, file, "policy file", 0))
 480     return (-1);
 481   while (!read_policy_file(&pf)) {
 482     DA_PUSH(&v, pf.p);
 483     init_policy(&pf.p);
 484   }
 485   close_policy_file(&pf);
 486   if (!pf.err) {
 487     DA_DESTROY(pv);
 488     *pv = v;
 489     return (0);
 490   } else {
 491     DA_DESTROY(&v);
 492     return (-1);
 493   }
 494 }
 495
 496 /*----- That's all, folks -------------------------------------------------*/