Initial checkin. Compiles but doesn't run yet.

[userv-utils] / ipif / service.c

/*
 * userv service (or standalone program)
 * for per-user IP subranges.
 *
 * This is invoked as root, directly from userv.
 * Its arguments are supposed to be, in order:
 *  <base-prefix>/<base-prefix-len>
 *      Specifies the base address and prefix to restrict the
 *      addresses used to.
 *  <gid-min>-<gid-max>:<gid-add>/<gid-mask>[,...]
 *      The ranges specified by <gid-min> are checked <gid-max> until
 *      one is found which matches at least one gid in USERV_GID.
 *      Then the gid will have <gid-add> added to it and will then be
 *      masked so that it is <gid-mask> long (higher set bits are
 *      discarded).  The result is added to the base prefix.  It is an
 *      error for no gid to match.  Alternatively, if this argument
 *      is `*' then USERV_GID is not checked.
 *  --  Indicates that the remaining arguments are user-supplied
 *      and therefore untrusted.
 *  <local-addr>,<peer-addr>,<mtu>,<proto>
 *      As for slattach.  Supported protocols are slip, cslip, and
 *      adaptive.  Alternatively, set to `debug' to print debugging
 *      info.  <local-addr> is address of the interface on chiark;
 *      <peer-addr> is the address of the point-to-point peer.
 *  <prefix>/<mask>,<prefix>/<mask>,...
 *      List of additional routes to add for this interface.
 *      May be the empty argument.
 *
 * Should be run from userv with no-disconnect-hup.
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <errno.h>

#define NARGS 5
#define MAXEXROUTES 5
#define ATXTLEN 12

static const char *proto;
static unsigned long baseprefix, basemask;
static unsigned long localaddr, peeraddr, mtu;
static int nexroutes;
static struct exroute {
  unsigned long prefix, mask;
  char prefixtxt[ATXTLEN], masktxt[ATXTLEN];
} exroutes[MAXEXROUTES];

char localtxt[ATXTLEN];
char peertxt[ATXTLEN];

static void fatal(const char *msg) {
  fprintf(stderr,"userv-ipif: service: fatal error: %s\n",msg);
  exit(8);
}
  
static void sysfatal(const char *msg) {
  fprintf(stderr,"userv-ipif: service: fatal system error: %s: %s\n",
	  msg, strerror(errno));
  exit(12);
}
  
static void badusage(void) {
  fputs("userv-ipif: service: bad usage or permission denied\n",stderr);
  exit(16);
}

static char *ip2txt(unsigned long addr, char *buf) {
  sprintf(buf, "%lu.%lu.%lu.%lu",
	  (addr>>24) & 0x0ff,
	  (addr>>16) & 0x0ff,
	  (addr>>8) & 0x0ff,
	  (addr) & 0x0ff);
  return buf;
}

static unsigned long eat_number(const char **argp, const char *what,
				unsigned long min, unsigned long max,
				const char *endchars, int *endchar_r) {
  /* If !endchars then the endchar must be a nul, otherwise it may be
   * a nul (resulting in *argp set to 0) or something else (*argp set
   * to point to after delim, *endchar_r set to delim).
   * *endchar_r may be 0.
   */
  unsigned long rv;
  char *ep;
  int endchar;

  if (!*argp) { fprintf(stderr,"missing number %s\n",what); badusage(); }
  rv= strtoul(*argp,&ep,0);
  if ((endchar= *ep)) {
    if (!endchars) { fprintf(stderr,"junk after number %s\n",what); badusage(); }
    if (!strchr(endchars,endchar)) {
      fprintf(stderr,"invalid delimiter %c after number %s: expected %s (or none?)\n",
	      endchar,what,endchars);
      badusage();
    }
    *argp= ep+1;
  } else {
    *argp= 0;
  }
  if (endchar_r) *endchar_r= endchar;
  if (rv < min || rv > max) {
    fprintf(stderr,"number %s value %lu out of range %lu..%lu",
	    what, rv, min, max);
    badusage();
  }
  return rv;
}

static void addrnet_mustbein(const char *what,
			     unsigned long prefix, unsigned long mask,
			     unsigned long mprefix, unsigned long mmask) {
  if (!(~mask & mmask) && (prefix & mmask) == mprefix) return;
  fprintf(stderr, "%s %08lx/%08lx not in required subspace %08lx/%08lx\n",
	  what, prefix, mask, mprefix, mmask);
  badusage();
}

static void addrnet_mustdiffer(const char *w1, unsigned long p1, unsigned long m1,
			       const char *w2, unsigned long p2, unsigned long m2) {
  unsigned long mask;

  mask= m1&m2;
  if ((p1 & mask) != (p2 & mask)) return;
  fprintf(stderr, "%s %08lx/%08lx overlaps/clashes with %s %08lx/%08lx",
	  w1,p1,m1, w2,p2,m2);
  badusage();
}
  
static unsigned long eat_addr(const char **argp, const char *what,
			      unsigned long mprefix, unsigned long mmask,
			      const char *endchars, int *endchar_r) {
  char whatbuf[100];
  unsigned long rv;
  int i;

  assert(!(~mmask & mprefix));

  for (rv=0, i=0;
       i<4;
       i++) {
    rv <<= 8;
    sprintf(whatbuf,"%s byte #%d",what,i);
    rv |= eat_number(argp,whatbuf, 0,255, i<3 ? "." : endchars, endchar_r);
  }

  addrnet_mustbein(what,rv,~0UL, mprefix,mmask);
  return rv;
}

static void eat_prefixmask(const char **argp, const char *what,
			   unsigned long mprefix, unsigned long mmask,
			   const char *endchars, int *endchar_r,
			   unsigned long *prefix_r, unsigned long *mask_r, int *len_r) {
  /* mask_r and len_r may be 0 */
  char whatbuf[100];
  int len;
  unsigned long prefix, mask;

  prefix= eat_addr(argp,what, 0,0, "/",0);
  sprintf(whatbuf,"%s length",what);
  len= eat_number(argp,whatbuf, 0,32, endchars,endchar_r);

  mask= (~0UL << (32-len));
  if (prefix & ~mask) {
    fprintf(stderr,"%s prefix %08lx not fully contained in mask %08lx\n",
	    what,prefix,mask);
    badusage();
  }
  addrnet_mustbein(what,prefix,mask, mprefix,mmask);
  *prefix_r= prefix;
  if (mask_r) *mask_r= mask;
  if (len_r) *len_r= len;
}
  
int main(int argc, const char *const *argv) {
  static unsigned long gidmaxval= (unsigned long)((gid_t)-2);
  static const char *const protos_ok[]= { "slip", "cslip", "adaptive", 0 };

  unsigned long gidmin, gidmax, gidadd;
  int baselen;
  unsigned long routeaddr, routemask, tgid;
  const char *carg, *gidlist;
  const char *const *cprotop;
  int gidlen, i;
  char erwhatbuf[100], erwhatbuf2[100];
  
  if (argc < NARGS+1) { fputs("too few arguments\n",stderr); badusage(); }
  if (argc > NARGS+1) { fputs("too many arguments\n",stderr); badusage(); }

  carg= *++argv;
  eat_prefixmask(&carg,"base", 0UL,0UL, 0,0, &baseprefix, &basemask, &baselen);

  carg= *++argv;
  if (!strcmp(carg,"*")) {
    for (;;) {
      if (!*carg) fatal("no gid authorised");
      gidmin= eat_number(&carg,"gid-min", 0,gidmaxval, "-",0);
      gidmax= eat_number(&carg,"gid-max", gidmin,gidmaxval, ":",0);
      gidadd= eat_number(&carg,"gid-add", 0,gidmaxval, "/",0);
      gidlen= eat_number(&carg,"gid-len", 0,32-baselen, 0,0);

      gidlist= getenv("USERV_GID");
      if (!gidlist) fatal("USERV_GID not set");
      while (gidlist) {
	tgid= eat_number(&gidlist,"userv_gid", 0,gidmaxval, " ",0);
	if (tgid >= gidmin && tgid <= gidmax) goto gid_found;
      }
    }
  gid_found:
    tgid += gidadd;
    tgid &= ((1UL << gidlen) - 1);
    baselen += gidlen;
    baseprefix |= (tgid << (32-baselen));
    basemask = (~0UL << (32-baselen));
  } else {
    tgid= 0;
  }
  
  carg= *++argv;

  localaddr= eat_addr(&carg,"local-addr", baseprefix,basemask, ",",0);
  peeraddr= eat_addr(&carg,"peer-addr", baseprefix,basemask, ",",0);
  mtu= eat_number(&carg,"mtu", 576,65536, ",",0);
  
  if (!strcmp(carg,"debug")) {
    proto= 0;
  } else {
    for (cprotop= protos_ok;
	 (proto= *cprotop) && strcmp(proto,carg);
	 cprotop++);
    if (!proto) fatal("invalid protocol");
  }
  
  addrnet_mustdiffer("local-addr",localaddr,~0UL, "peer-addr",peeraddr,~0UL);
  
  carg= *++argv;
  for (nexroutes=0;
       *carg;
       carg++, nexroutes++) {
    if (nexroutes == MAXEXROUTES) {
      fprintf(stderr,"only %d extra routes allowed\n",MAXEXROUTES);
      fatal("too many extra routes");
    }
    sprintf(erwhatbuf,"route %d",nexroutes+1);
    
    eat_prefixmask(&carg,erwhatbuf, baseprefix,basemask, ",",0, &routeaddr,&routemask,0);
    addrnet_mustdiffer(erwhatbuf,routeaddr,routemask, "local-addr",localaddr,~0UL);
    addrnet_mustdiffer(erwhatbuf,routeaddr,routemask, "peer-addr",peeraddr,~0UL);
    for (i=0; i<nexroutes; i++) {
      sprintf(erwhatbuf2,"route %d",i+1);
      addrnet_mustdiffer(erwhatbuf,routeaddr,routemask,
			 erwhatbuf2,exroutes[i].prefix,exroutes[i].mask);
    }
    exroutes[nexroutes].prefix= routeaddr;
    exroutes[nexroutes].mask= routemask;
    ip2txt(routeaddr,exroutes[nexroutes].prefixtxt);
    ip2txt(routemask,exroutes[nexroutes].masktxt);
  }
  ip2txt(localaddr,localtxt);
  ip2txt(peeraddr,peertxt);
  
  if (!proto) {
    char basetxt[ATXTLEN];
    
    printf("protocol: debug\n"
	   "base:     %08lx/%-2ld == %s/%ld\n"
	   "auth gid: %ld"
	   "local:    %08lx    == %s\n"
	   "peer:     %08lx    == %s\n"
	   "mtu:      %ld"
	   "routes:   %d",
	   baseprefix, basemask, ip2txt(baseprefix,basetxt), basemask,
	   tgid,
	   localaddr, localtxt,
	   peeraddr, peertxt,
	   mtu,
	   nexroutes);
    for (i=0; i<nexroutes; i++) {
      sprintf(erwhatbuf2, "route %d:", i+1);
      printf("%-9s %08lx/%-2ld == %s/%s\n",
	     erwhatbuf,
	     exroutes[i].prefix, exroutes[i].mask,
	     exroutes[i].prefixtxt, exroutes[i].masktxt);
    }
    if (ferror(stdout) || fclose(stdout)) sysfatal("flush stdout");
    exit(0);
  }
  abort();
}