[become] / src / netg.c

/* -*-c-*-
 *
 * $Id: netg.c,v 1.1 1997/08/07 09:45:00 mdw Exp $
 *
 * A local database of netgroups
 *
 * (c) 1997 EBI
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of `become'
 *
 * `Become' is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * `Become' is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with `become'; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------*
 *
 * $Log: netg.c,v $
 * Revision 1.1  1997/08/07 09:45:00  mdw
 * New source file added to maintain a netgroups database.
 *
 */

/*----- Header files ------------------------------------------------------*/

/* --- ANSI headers --- */

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* --- Unix headers --- */

#include "config.h"

#include <sys/types.h>

#ifdef HAVE_YP
#  include <rpc/rpc.h>
#  include <rpcsvc/ypclnt.h>
#  include <rpcsvc/yp_prot.h>
#endif

#include <netinet/in.h>

#include <arpa/inet.h>

#include <pwd.h>
#include <netdb.h>
#include <unistd.h>

/* --- Local headers --- */

#include "become.h"
#include "config.h"
#include "netg.h"
#include "sym.h"
#include "userdb.h"
#include "utils.h"

/*----- Type definitions --------------------------------------------------*/

/* --- Quick discussion --- *
 *
 * I've just noticed: netgroups are horrible.  They form a directed graph
 * which is really horrible; I'll have to try and turn it into something
 * more sensible (which will essentially involve cutting cycles).
 *
 * The structure looks a little bit like a good ol' List (see Knuth 1 or
 * any decent Lisp manual), but with more information in the cons cells.
 */

/* --- @netg__cons@ --- */

typedef struct netg__cons {
  unsigned f;
  union {
    struct netg__cons *cons;
    struct netg__atom *atom;
  } car;
  struct netg__cons *cdr;
} netg__cons;

enum {
  f_cons = 1,                           /* The @car@ is a cons cell */
  f_visit = 2,                          /* Currently threaded on this cell */
  f_uncycled = 4                        /* Cycles removed from here on in */
};

/* --- @netg__atom@ --- */

typedef struct netg__atom {
  char *n;                              /* Unresolved netgroup reference */
  char *h;                              /* Matched hostname */
  char *u;                              /* Matched user name */
  char *d;                              /* Matched domain name */
} netg__atom;

/* --- @netg__sym@ --- */

typedef struct netg__sym {
  sym_base _base;
  netg__cons *cons;
} netg__sym;

/* --- Token types for the netgroup parser --- */

enum {
  tok_string = 256,
  tok_eof
};

/*----- Static variables --------------------------------------------------*/

static sym_table netg__table;           /* Netgroup table */
static sym_iter netg__iter;             /* Iterator object for users */

/*----- Main code ---------------------------------------------------------*/

/* --- @netg__lex@ --- *
 *
 * Arguments:   @const char **p@ = pointer to next unscanned character
 *              @char *q@ = pointer to output buffer
 *
 * Returns:     Token type (either character code or a magic number).
 *
 * Use:         Lexes a netgroups line into tokens.
 */

static int netg__lex(char **p, char *q)
{
  /* --- Skip any leading whitespace --- */

  while (isspace((unsigned char)**p))
    (*p)++;

  /* --- Now work out what we've got --- */

  if (**p == 0)
    return (tok_eof);
  if (**p == '(' || **p == ')' || **p == ',')
    return (*(*p)++);
  do
    *q++ = *(*p)++;
  while (**p != 0 && **p != '(' && **p != ')' &&
         **p != ',' && !isspace((unsigned char)**p));
  *q++ = 0;
  return (tok_string);
}

/* --- @netg__foreach@ --- *
 *
 * Arguments:   @int st@ = YP protocol-level status code
 *              @char *k@ = pointer to string containing the key
 *              @int ksz@ = length of the key string
 *              @char *v@ = pointer to string containing the value
 *              @int vsz@ = length of the value string
 *              @char *data@ = pointer to my data information
 *
 * Returns:     Zero to continue, nonzero for no more entries.
 *
 * Use:         Handles each incoming netgroup, attaching it to the table.
 */

static int netg__foreach(int st, char *k, int ksz,
                         char *v, int vsz, char *data)
{
  char *kc, *vc;
  unsigned f;
  netg__sym *sng;
  netg__cons *c, **link;
  char *p;
  int t;

  /* --- If something is amiss, then quit now --- */

  if (st != YP_TRUE)
    return (-1);

  /* --- Ignore empty lines from the original file --- */

  if (!ksz || !vsz)
    return (0);

  /* --- Build my own trashable copies of the key and value --- *
   *
   * Note the oddness when I copy the value string.  The extra byte at the
   * beginning allows me to use the same area of memory as an output buffer
   * for the lexer.  It must be big enough; the lexer doesn't back up; and
   * that extra byte gives me somewhere to put a terminating null byte.
   */

  kc = xmalloc(ksz + 1);
  memcpy(kc, k, ksz);
  kc[ksz] = 0;

  vc = xmalloc(vsz + 2);
  memcpy(vc + 1, v, vsz);
  vc[vsz + 1] = 0;

  T( trace(TRACE_DEBUG, "debug: netgroup `%s': `%s'", kc, vc + 1); )

  /* --- Allocate a symbol in my table --- */

  sng = sym_find(&netg__table, kc, -1, sizeof(*sng), &f);
  if (!f)
    sng->cons = 0;

  /* --- Run to the end of the list --- */

  for (link = &sng->cons; *link; link = &((*link)->cdr))
    ;

  /* --- Now start the tricky bit --- *
   *
   * I have to start parsing the netgroup value string.  Oh, well, it
   * could be worse.
   *
   * The parser is written so as to avoid saying things more often than
   * necessary.  This tends to involve @goto@s.  You've been warned.
   */

  p = vc + 1;
  t = netg__lex(&p, vc);

  for (;;) {

    /* --- Start with a fresh cons cell, with an empty atom attached --- */

    c = xmalloc(sizeof(*c));
    c->car.atom = xmalloc(sizeof(*c->car.atom));

    /* --- Restart here after an error --- *
     *
     * If I restart here, I can avoid freeing the cons cell reallocating
     * it, which is a little silly.
     */

  duff_restart:
    c->car.atom->n = c->car.atom->h = c->car.atom->u = c->car.atom->d = 0;
    c->f = 0;
    c->cdr = 0;

    /* --- Handle end-of-line --- */

    if (t == tok_eof)
      break;

    /* --- Handle a netgroup reference --- */

    if (t == tok_string) {
      T( trace(TRACE_DEBUG, "debug: add reference to `%s'", vc); )
      c->car.atom->n = xstrdup(vc);
      *link = c;
      link = &c->cdr;
      t = netg__lex(&p, vc);
      continue;
    }

    /* --- Parse our merry way through the host--user--domain triple --- */

    if (t != '(')
      goto duff;
    t = netg__lex(&p, vc);

    if (t == tok_string) {
      T( trace(TRACE_DEBUG, "debug: add host `%s'", vc); )
      c->car.atom->h = xstrdup(vc);
      t = netg__lex(&p, vc);
    }

    if (t != ',')
      goto duff_paren;
    t = netg__lex(&p, vc);

    if (t == tok_string) {
      T( trace(TRACE_DEBUG, "debug: add user `%s'", vc); )
      c->car.atom->u = xstrdup(vc);
      t = netg__lex(&p, vc);
    }

    if (t != ',')
      goto duff_paren;
    t = netg__lex(&p, vc);

    if (t == tok_string) {
      T( trace(TRACE_DEBUG, "debug: add domain `%s'", vc); )
      c->car.atom->d = xstrdup(vc);
      t = netg__lex(&p, vc);
    }

    if (t != ')')
      goto duff_paren;
    t = netg__lex(&p, vc);

    /* --- Finished that, so insert this cons cell into the list --- */

    *link = c;
    link = &c->cdr;
    continue;

    /* --- Tidy up during scanning of a triple --- *
     *
     * I'll search for the closing paren, and hope that I won't miss out too
     * much.
     */

  duff_paren:
    while (t != tok_eof && t != ')')
      t = netg__lex(&p, vc);

    /* --- Other syntax oddnesses come out here --- *
     *
     * Snarf the token which caused the error.
     */

  duff:
    moan("syntax error in netgroups line for `%s'", kc);
    if (c->car.atom->n) free(c->car.atom->n);
    if (c->car.atom->h) free(c->car.atom->h);
    if (c->car.atom->u) free(c->car.atom->u);
    if (c->car.atom->d) free(c->car.atom->d);
    t = netg__lex(&p, vc);
    goto duff_restart;
  }

  free(kc);
  free(vc);
  return (0);
}

/* --- @netg__dumpGroup@ ---  *
 *
 * Arguments:   @netg__cons *c@ = pointer to a list head
 *              @int lev@ = indentation level
 *
 * Returns:     ---
 *
 * Use:         Dumps the netgroup given.
 */

#ifdef TRACING

static void netg__dumpGroup(netg__cons *c, int lev)
{
  netg__cons *cc;

  if (!c)
    return;

  /* --- Check for a cycle --- */

  if (c->f & f_visit) {
    trace(TRACE_DEBUG, "debug: %*scycle!", lev * 2, "");
    return;
  }

  /* --- Dump the netgroup --- */

  c->f |= f_visit;

  for (cc = c; cc; cc = cc->cdr) {
    if (cc->f & f_cons) {
      trace(TRACE_DEBUG, "debug: %*ssubnetgroup...", lev * 2, "");
      netg__dumpGroup(cc->car.cons, lev + 1);
    } else if (cc->car.atom->n) {
      trace(TRACE_DEBUG, "debug: %*sunresolved subgroup `%s'",
            lev * 2, "", cc->car.atom->n);
    } else {
      trace(TRACE_DEBUG, "debug: %*s(%s, %s, %s)", lev * 2, "",
            cc->car.atom->h ? cc->car.atom->h : "<all-hosts>",
            cc->car.atom->u ? cc->car.atom->u : "<all-users>",
            cc->car.atom->d ? cc->car.atom->d : "<all-domains>");
    }
  }

  c->f &= ~f_visit;
}

#endif

/* --- @netg__dump@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Dumps the netgroups table.
 */

static void netg__dump(void)
{
  sym_iter i;
  netg__sym *sng;

#ifdef TRACING
  trace(TRACE_DEBUG, "debug: dumping netgroups file");
  for (sym_createIter(&i, &netg__table); (sng = sym_next(&i)) != 0; ) {
    trace(TRACE_DEBUG, "debug: netgroup `%s'...", sng->_base.name);
    sng->cons->f &= ~f_visit;
    netg__dumpGroup(sng->cons, 1);
  }
#endif
}

/* --- @netg_iterate@, @netg_iterate_r@ --- *
 *
 * Arguments:   @netg_iter *i@ = pointer to a netgroup iterator object
 *
 * Returns:     ---
 *
 * Use:         Starts iterating over the netgroups.
 */

void netg_iterate(void) { netg_iterate_r(&netg__iter); }
void netg_iterate_r(netg_iter *i) { sym_createIter(i, &netg__table); }

/* --- @netg_next@, @netg_next_r@ --- *
 *
 * Arguments:   @netg_iter *i@ = pointer to a netgroup iterator object
 *
 * Returns:     An opaque pointer to the next item, or null.
 *
 * Use:         Returns the next netgroup.
 */

netg *netg_next(void) { return (netg_next_r(&netg__iter)); }
netg *netg_next_r(netg_iter *i) { return (sym_next(i)); }

/* --- @netg_name@ --- *
 *
 * Arguments:   @netg *n@ = netgroup handle returned by @netg_next@.
 *
 * Returns:     A pointer to the name; you may not modify this string.
 *
 * Use:         Returns the name of a netgroup.
 */

const char *netg_name(netg *n) { return (n->_base.name); }

/* --- @netg_scan@ --- *
 *
 * Arguments:   @netg *n@ = a netgroup handle returned by @netg_next@
 *              @int (*proc)(netg *n, const char *host, const char *user,@
 *                      @const char *domain, void *ctx)@ = function to call
 *                              for each member.
 *              @void *ctx@ = context pointer to pass to @proc@.
 *
 * Returns:     Zero if all went well, or the nonzero return value from
 *              @proc@.
 *
 * Use:         Passes all the members of the netgroup to a given function.
 *              The function is given the names, directly from the NIS
 *              netgroup map, except that any empty entries are passed as
 *              null pointers rather than empty strings.  You may not modify
 *              any of the strings.  The enumeration function, @proc@, may
 *              return nonzero to stop itself from being called any more;
 *              if this happens, the value it returns becomes the result of
 *              this function.  If all the items are enumerated OK, this
 *              function returns zero.
 */

static int netg__doScan(netg__cons *c,
                        netg *n,
                        int (*proc)(netg */*n*/, const char */*host*/,
                                    const char */*user*/,
                                    const char */*domain*/, void */*ctx*/),
                        void *ctx)
{
  int e;

  while (c) {
    if (c->f & f_cons)
      e = netg__doScan(c->car.cons, n, proc, ctx);
    else
      e = proc(n, c->car.atom->h, c->car.atom->u, c->car.atom->d, ctx);
    if (e)
      return (e);
    c = c->cdr;
  }
  return (0);
}

int netg_scan(netg *n,
              int (*proc)(netg */*n*/, const char */*host*/,
                          const char */*user*/, const char */*domain*/,
                          void */*ctx*/),
              void *ctx)
{
  return (netg__doScan(n->cons, n, proc, ctx));
}

/* --- @netg__breakCycle@ --- *
 *
 * Arguments:   @netg__cons *c@ = pointer to a list
 *
 * Returns:     ---
 *
 * Use:         Scans the given list (recursively) and breaks any cycles it
 *              finds.
 */

static void netg__breakCycle(netg__cons *c)
{
  netg__cons *cc;

  if (!c || c->f & f_uncycled)
    return;

  c->f |= f_visit;
  for (cc = c; cc; cc = cc->cdr) {
    if (~cc->f & f_cons)
      continue;
    if (cc->car.cons->f & f_visit) {
      T( trace(TRACE_DEBUG, "debug: cycle in netgroups"); )
      cc->car.cons = 0;
    } else
      netg__breakCycle(cc->car.cons);
  }
  c->f &= ~f_visit;
  c->f |= f_uncycled;
}

/* --- @netg_init@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Reads the netgroup database and turns it into something nice.
 */

void netg_init(void)
{
  char *ypdom;

  /* --- Initialise my symbol table --- */

  sym_createTable(&netg__table);

  /* --- Bind myself unto a YP server --- */

  if (yp_get_default_domain(&ypdom) ||
      yp_bind(ypdom))
    return;
  
  /* --- Now try to read all the netgroup entries --- */

  {
    static struct ypall_callback ncb = { netg__foreach, 0 };
    yp_all(ypdom, "netgroup", &ncb);
  }

  /* --- Unbind from the server --- */

  yp_unbind(ypdom);

  /* --- Dump the table --- */

  IF_TRACING(TRACE_DEBUG, netg__dump(); )

  /* --- Now resolve all the remaining references --- */

  {
    sym_iter i;
    netg__sym *sng, *ng;
    netg__cons *c;
    netg__atom *a;

    for (sym_createIter(&i, &netg__table); (sng = sym_next(&i)) != 0; ) {
      for (c = sng->cons; c; c = c->cdr) {
        if ((c->f & f_cons) == 0 && c->car.atom->n) {
          a = c->car.atom;
          ng = sym_find(&netg__table, a->n, -1, 0, 0);
          if (!ng) {
            moan("undefined netgroup `%s' (ignored)", a->n);
            c->car.atom = 0;
          } else {
            c->car.cons = ng->cons;
            c->f |= f_cons;
          }
          free(a->n);
          free(a);
        }
      }
    }
  }

  /* --- Remove cycles in the netgroups table --- */

  {
    sym_iter i;
    netg__sym *sng;

    for (sym_createIter(&i, &netg__table); (sng = sym_next(&i)) != 0; )
      sng->cons->f &= ~f_uncycled;
    for (sym_createIter(&i, &netg__table); (sng = sym_next(&i)) != 0; )
      netg__breakCycle(sng->cons);
  }    

  /* --- Dump the table again --- */

  IF_TRACING(TRACE_DEBUG, netg__dump(); )
}

/* --- @netg_reinit@ --- *
 *
 * Arguments:   ---
 *
 * Returns:     ---
 *
 * Use:         Forces a re-read of the netgroups file.
 */

void netg_reinit(void)
{
  sym_iter i;
  netg__sym *sng;
  netg__cons *c, *cc;

  /* --- Remove all the old netgroups rubbish --- */

  for (sym_createIter(&i, &netg__table); (sng = sym_next(&i)) != 0; ) {
    c = sng->cons;
    while (c) {
      cc = c->cdr;
      if (~c->f & f_cons) {
        if (c->car.atom->n) free(c->car.atom->n);
        if (c->car.atom->h) free(c->car.atom->h);
        if (c->car.atom->u) free(c->car.atom->u);
        if (c->car.atom->d) free(c->car.atom->d);
      }
      free(c);
      c = cc;
    }
    sym_remove(&netg__table, sng);
  }

  /* --- Now rebuild the world --- */

  netg_init();
}

/*----- Test driver -------------------------------------------------------*/

#ifdef TEST_RIG

int scanner(netg *n, const char *h, const char *u, const char *d, void *c)
{
  fprintf(stderr, "  %s, %s, %s\n",
          h ? h : "<any>", u ? u : "<any>", d ? d : "<any>");
  return (0);
}

int main(void)
{
  netg *n;
  ego("netg-test");
  traceon(stderr, TRACE_ALL);
  netg_init();
  for (netg_iterate(); (n = netg_next()) != 0; ) {
    fprintf(stderr, "netgroup %s\n", netg_name(n));
    netg_scan(n, scanner, 0);
  }
  return (0);
}

#endif

/*----- That's all, folks -------------------------------------------------*/