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getcap.c

/*-
 * Copyright (c) 1992, 1993
 *    The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Casey Leedom of Lawrence Livermore National Laboratory.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the University of
 *    California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)getcap.c      8.3 (Berkeley) 3/25/94";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
#ifdef __FBSDID
__FBSDID("$FreeBSD: src/lib/libc/gen/getcap.c,v 1.19 2003/01/02 10:19:43 thomas Exp $");
#endif

#include <sys/types.h>

#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#if 0
#include <db.h>
#endif

#include "extern.h"

#define _open open
#define _read read
#define _close close
#define reallocf realloc

#define     BFRAG       1024
#define     BSIZE       1024
#define     ESC         ('[' & 037) /* ASCII ESC */
#define     MAX_RECURSION     32          /* maximum getent recursion */
#define     SFRAG       100         /* cgetstr mallocs in SFRAG chunks */

#define RECOK     (char)0
#define TCERR     (char)1
#define     SHADOW      (char)2

static size_t      topreclen; /* toprec length */
static char *toprec;    /* Additional record specified by cgetset() */
static int   gottoprec; /* Flag indicating retrieval of toprecord */

#if 0
static int  cdbget(DB *, char **, const char *);
#endif
static int  getent(char **, u_int *, char **, int, const char *, int, char *);
static int  nfcmp(char *, char *);

/*
 * Cgetset() allows the addition of a user specified buffer to be added
 * to the database array, in effect "pushing" the buffer on top of the
 * virtual database. 0 is returned on success, -1 on failure.
 */
int
cgetset(const char *ent)
{
      if (ent == NULL) {
            if (toprec)
                  free(toprec);
                toprec = NULL;
                topreclen = 0;
                return (0);
        }
        topreclen = strlen(ent);
        if ((toprec = malloc (topreclen + 1)) == NULL) {
            errno = ENOMEM;
                return (-1);
      }
      gottoprec = 0;
        (void)strcpy(toprec, ent);
        return (0);
}

/*
 * Cgetcap searches the capability record buf for the capability cap with
 * type `type'.  A pointer to the value of cap is returned on success, NULL
 * if the requested capability couldn't be found.
 *
 * Specifying a type of ':' means that nothing should follow cap (:cap:).
 * In this case a pointer to the terminating ':' or NUL will be returned if
 * cap is found.
 *
 * If (cap, '@') or (cap, terminator, '@') is found before (cap, terminator)
 * return NULL.
 */
char *
cgetcap(char *buf, const char *cap, int type)
{
      char *bp;
      const char *cp;

      bp = buf;
      for (;;) {
            /*
             * Skip past the current capability field - it's either the
             * name field if this is the first time through the loop, or
             * the remainder of a field whose name failed to match cap.
             */
            for (;;)
                  if (*bp == '\0')
                        return (NULL);
                  else
                        if (*bp++ == ':')
                              break;

            /*
             * Try to match (cap, type) in buf.
             */
            for (cp = cap; *cp == *bp && *bp != '\0'; cp++, bp++)
                  continue;
            if (*cp != '\0')
                  continue;
            if (*bp == '@')
                  return (NULL);
            if (type == ':') {
                  if (*bp != '\0' && *bp != ':')
                        continue;
                  return(bp);
            }
            if (*bp != type)
                  continue;
            bp++;
            return (*bp == '@' ? NULL : bp);
      }
      /* NOTREACHED */
}

/*
 * Cgetent extracts the capability record name from the NULL terminated file
 * array db_array and returns a pointer to a malloc'd copy of it in buf.
 * Buf must be retained through all subsequent calls to cgetcap, cgetnum,
 * cgetflag, and cgetstr, but may then be free'd.  0 is returned on success,
 * -1 if the requested record couldn't be found, -2 if a system error was
 * encountered (couldn't open/read a file, etc.), and -3 if a potential
 * reference loop is detected.
 */
int
cgetent(char **buf, char **db_array, const char *name)
{
      u_int dummy;

      return (getent(buf, &dummy, db_array, -1, name, 0, NULL));
}

/*
 * Getent implements the functions of cgetent.  If fd is non-negative,
 * *db_array has already been opened and fd is the open file descriptor.  We
 * do this to save time and avoid using up file descriptors for tc=
 * recursions.
 *
 * Getent returns the same success/failure codes as cgetent.  On success, a
 * pointer to a malloc'ed capability record with all tc= capabilities fully
 * expanded and its length (not including trailing ASCII NUL) are left in
 * *cap and *len.
 *
 * Basic algorithm:
 *    + Allocate memory incrementally as needed in chunks of size BFRAG
 *      for capability buffer.
 *    + Recurse for each tc=name and interpolate result.  Stop when all
 *      names interpolated, a name can't be found, or depth exceeds
 *      MAX_RECURSION.
 */
static int
getent(char **cap, u_int *len, char **db_array, int fd, const char *name,
    int depth, char *nfield)
{
#if 0
      DB *capdbp;
#endif
      char *r_end, *rp, **db_p;
      int myfd, eof, foundit;
      char *record;
      int tc_not_resolved;
#if 0
      int retval, clen;
      char *cbuf, pbuf[_POSIX_PATH_MAX];
#endif

      /*
       * Return with ``loop detected'' error if we've recursed more than
       * MAX_RECURSION times.
       */
      if (depth > MAX_RECURSION)
            return (-3);

      /*
       * Check if we have a top record from cgetset().
         */
      if (depth == 0 && toprec != NULL && cgetmatch(toprec, name) == 0) {
            if ((record = malloc (topreclen + BFRAG)) == NULL) {
                  errno = ENOMEM;
                  return (-2);
            }
            (void)strcpy(record, toprec);
            myfd = 0;
            db_p = db_array;
            rp = record + topreclen + 1;
            r_end = rp + BFRAG;
            goto tc_exp;
      }
      /*
       * Allocate first chunk of memory.
       */
      if ((record = malloc(BFRAG)) == NULL) {
            errno = ENOMEM;
            return (-2);
      }
      r_end = record + BFRAG;
      foundit = 0;
      /*
       * Loop through database array until finding the record.
       */

      for (db_p = db_array; *db_p != NULL; db_p++) {
            eof = 0;

            /*
             * Open database if not already open.
             */

            if (fd >= 0) {
                  (void)lseek(fd, (off_t)0, SEEK_SET);
                  myfd = 0;
            } else {
#if 0
                  (void)snprintf(pbuf, sizeof(pbuf), "%s.db", *db_p);
                  if ((capdbp = dbopen(pbuf, O_RDONLY, 0, DB_HASH, 0))
                       != NULL) {
                        free(record);
                        retval = cdbget(capdbp, &record, name);
                        if (retval < 0) {
                              /* no record available */
                              (void)capdbp->close(capdbp);
                              return (retval);
                        }
                        /* save the data; close frees it */
                        clen = strlen(record);
                        cbuf = malloc(clen + 1);
                        memcpy(cbuf, record, clen + 1);
                        if (capdbp->close(capdbp) < 0) {
                              free(cbuf);
                              return (-2);
                        }
                        *len = clen;
                        *cap = cbuf;
                        return (retval);
                  } else
#endif
                  {
                        fd = _open(*db_p, O_RDONLY, 0);
                        if (fd < 0)
                              continue;
                        myfd = 1;
                  }
            }
            /*
             * Find the requested capability record ...
             */
            {
            char buf[BUFSIZ];
            char *b_end, *bp;
            int c;

            /*
             * Loop invariants:
             *    There is always room for one more character in record.
             *    R_end always points just past end of record.
             *    Rp always points just past last character in record.
             *    B_end always points just past last character in buf.
             *    Bp always points at next character in buf.
             */
            b_end = buf;
            bp = buf;
            for (;;) {

                  /*
                   * Read in a line implementing (\, newline)
                   * line continuation.
                   */
                  rp = record;
                  for (;;) {
                        if (bp >= b_end) {
                              int n;

                              n = _read(fd, buf, sizeof(buf));
                              if (n <= 0) {
                                    if (myfd)
                                          (void)_close(fd);
                                    if (n < 0) {
                                          free(record);
                                          return (-2);
                                    } else {
                                          fd = -1;
                                          eof = 1;
                                          break;
                                    }
                              }
                              b_end = buf+n;
                              bp = buf;
                        }

                        c = *bp++;
                        if (c == '\n') {
                              if (rp > record && *(rp-1) == '\\') {
                                    rp--;
                                    continue;
                              } else
                                    break;
                        }
                        *rp++ = c;

                        /*
                         * Enforce loop invariant: if no room
                         * left in record buffer, try to get
                         * some more.
                         */
                        if (rp >= r_end) {
                              u_int pos;
                              size_t newsize;

                              pos = rp - record;
                              newsize = r_end - record + BFRAG;
                              record = reallocf(record, newsize);
                              if (record == NULL) {
                                    errno = ENOMEM;
                                    if (myfd)
                                          (void)_close(fd);
                                    return (-2);
                              }
                              r_end = record + newsize;
                              rp = record + pos;
                        }
                  }
                        /* loop invariant let's us do this */
                  *rp++ = '\0';

                  /*
                   * If encountered eof check next file.
                   */
                  if (eof)
                        break;

                  /*
                   * Toss blank lines and comments.
                   */
                  if (*record == '\0' || *record == '#')
                        continue;

                  /*
                   * See if this is the record we want ...
                   */
                  if (cgetmatch(record, name) == 0) {
                        if (nfield == NULL || !nfcmp(nfield, record)) {
                              foundit = 1;
                              break;      /* found it! */
                        }
                  }
            }
      }
            if (foundit)
                  break;
      }

      if (!foundit) {
            free(record);
            return (-1);
      }

      /*
       * Got the capability record, but now we have to expand all tc=name
       * references in it ...
       */
tc_exp:     {
            char *newicap, *s;
            int newilen;
            u_int ilen;
            int diff, iret, tclen;
            char *icap, *scan, *tc, *tcstart, *tcend;

            /*
             * Loop invariants:
             *    There is room for one more character in record.
             *    R_end points just past end of record.
             *    Rp points just past last character in record.
             *    Scan points at remainder of record that needs to be
             *    scanned for tc=name constructs.
             */
            scan = record;
            tc_not_resolved = 0;
            for (;;) {
                  if ((tc = cgetcap(scan, "tc", '=')) == NULL)
                        break;

                  /*
                   * Find end of tc=name and stomp on the trailing `:'
                   * (if present) so we can use it to call ourselves.
                   */
                  s = tc;
                  for (;;)
                        if (*s == '\0')
                              break;
                        else
                              if (*s++ == ':') {
                                    *(s - 1) = '\0';
                                    break;
                              }
                  tcstart = tc - 3;
                  tclen = s - tcstart;
                  tcend = s;

                  iret = getent(&icap, &ilen, db_p, fd, tc, depth+1,
                              NULL);
                  newicap = icap;         /* Put into a register. */
                  newilen = ilen;
                  if (iret != 0) {
                        /* an error */
                        if (iret < -1) {
                              if (myfd)
                                    (void)_close(fd);
                              free(record);
                              return (iret);
                        }
                        if (iret == 1)
                              tc_not_resolved = 1;
                        /* couldn't resolve tc */
                        if (iret == -1) {
                              *(s - 1) = ':';
                              scan = s - 1;
                              tc_not_resolved = 1;
                              continue;

                        }
                  }
                  /* not interested in name field of tc'ed record */
                  s = newicap;
                  for (;;)
                        if (*s == '\0')
                              break;
                        else
                              if (*s++ == ':')
                                    break;
                  newilen -= s - newicap;
                  newicap = s;

                  /* make sure interpolated record is `:'-terminated */
                  s += newilen;
                  if (*(s-1) != ':') {
                        *s = ':';   /* overwrite NUL with : */
                        newilen++;
                  }

                  /*
                   * Make sure there's enough room to insert the
                   * new record.
                   */
                  diff = newilen - tclen;
                  if (diff >= r_end - rp) {
                        u_int pos, tcpos, tcposend;
                        size_t newsize;

                        pos = rp - record;
                        newsize = r_end - record + diff + BFRAG;
                        tcpos = tcstart - record;
                        tcposend = tcend - record;
                        record = reallocf(record, newsize);
                        if (record == NULL) {
                              errno = ENOMEM;
                              if (myfd)
                                    (void)_close(fd);
                              free(icap);
                              return (-2);
                        }
                        r_end = record + newsize;
                        rp = record + pos;
                        tcstart = record + tcpos;
                        tcend = record + tcposend;
                  }

                  /*
                   * Insert tc'ed record into our record.
                   */
                  s = tcstart + newilen;
                  bcopy(tcend, s, rp - tcend);
                  bcopy(newicap, tcstart, newilen);
                  rp += diff;
                  free(icap);

                  /*
                   * Start scan on `:' so next cgetcap works properly
                   * (cgetcap always skips first field).
                   */
                  scan = s-1;
            }

      }
      /*
       * Close file (if we opened it), give back any extra memory, and
       * return capability, length and success.
       */
      if (myfd)
            (void)_close(fd);
      *len = rp - record - 1; /* don't count NUL */
      if (r_end > rp)
            if ((record =
                 reallocf(record, (size_t)(rp - record))) == NULL) {
                  errno = ENOMEM;
                  return (-2);
            }

      *cap = record;
      if (tc_not_resolved)
            return (1);
      return (0);
}

#if 0
static int
cdbget(DB *capdbp, char **bp, const char *name)
{
      DBT key, data;
      char *namebuf;

      namebuf = strdup(name);
      if (namebuf == NULL)
            return (-2);
      key.data = namebuf;
      key.size = strlen(namebuf);

      for (;;) {
            /* Get the reference. */
            switch(capdbp->get(capdbp, &key, &data, 0)) {
            case -1:
                  free(namebuf);
                  return (-2);
            case 1:
                  free(namebuf);
                  return (-1);
            }

            /* If not an index to another record, leave. */
            if (((char *)data.data)[0] != SHADOW)
                  break;

            key.data = (char *)data.data + 1;
            key.size = data.size - 1;
      }

      *bp = (char *)data.data + 1;
      free(namebuf);
      return (((char *)(data.data))[0] == TCERR ? 1 : 0);
}
#endif

/*
 * Cgetmatch will return 0 if name is one of the names of the capability
 * record buf, -1 if not.
 */
int
cgetmatch(const char *buf, const char *name)
{
      const char *np, *bp;

      if (name == NULL || *name == '\0')
            return -1;

      /*
       * Start search at beginning of record.
       */
      bp = buf;
      for (;;) {
            /*
             * Try to match a record name.
             */
            np = name;
            for (;;)
                  if (*np == '\0')
                        if (*bp == '|' || *bp == ':' || *bp == '\0')
                              return (0);
                        else
                              break;
                  else
                        if (*bp++ != *np++)
                              break;

            /*
             * Match failed, skip to next name in record.
             */
            bp--; /* a '|' or ':' may have stopped the match */
            for (;;)
                  if (*bp == '\0' || *bp == ':')
                        return (-1);      /* match failed totally */
                  else
                        if (*bp++ == '|')
                              break;      /* found next name */
      }
}





#if 0
int
cgetfirst(char **buf, char **db_array)
{
      (void)cgetclose();
      return (cgetnext(buf, db_array));
}

static FILE *pfp;
static int slash;
static char **dbp;

int
cgetclose(void)
{
      if (pfp != NULL) {
            (void)fclose(pfp);
            pfp = NULL;
      }
      dbp = NULL;
      gottoprec = 0;
      slash = 0;
      return(0);
}

/*
 * Cgetnext() gets either the first or next entry in the logical database
 * specified by db_array.  It returns 0 upon completion of the database, 1
 * upon returning an entry with more remaining, and -1 if an error occurs.
 */
int
cgetnext(char **bp, char **db_array)
{
      size_t len;
      int done, hadreaderr, i, savederrno, status;
      char *cp, *line, *rp, *np, buf[BSIZE], nbuf[BSIZE];
      u_int dummy;

      if (dbp == NULL)
            dbp = db_array;

      if (pfp == NULL && (pfp = fopen(*dbp, "r")) == NULL) {
            (void)cgetclose();
            return (-1);
      }
      for(;;) {
            if (toprec && !gottoprec) {
                  gottoprec = 1;
                  line = toprec;
            } else {
                  line = fgetln(pfp, &len);
                  if (line == NULL && pfp) {
                        hadreaderr = ferror(pfp);
                        if (hadreaderr)
                              savederrno = errno;
                        fclose(pfp);
                        pfp = NULL;
                        if (hadreaderr) {
                              cgetclose();
                              errno = savederrno;
                              return (-1);
                        } else {
                              if (*++dbp == NULL) {
                                    (void)cgetclose();
                                    return (0);
                              } else if ((pfp =
                                  fopen(*dbp, "r")) == NULL) {
                                    (void)cgetclose();
                                    return (-1);
                              } else
                                    continue;
                        }
                  } else
                        line[len - 1] = '\0';
                  if (len == 1) {
                        slash = 0;
                        continue;
                  }
                  if (isspace((unsigned char)*line) ||
                      *line == ':' || *line == '#' || slash) {
                        if (line[len - 2] == '\\')
                              slash = 1;
                        else
                              slash = 0;
                        continue;
                  }
                  if (line[len - 2] == '\\')
                        slash = 1;
                  else
                        slash = 0;
            }


            /*
             * Line points to a name line.
             */
            i = 0;
            done = 0;
            np = nbuf;
            for (;;) {
                  for (cp = line; *cp != '\0'; cp++) {
                        if (*cp == ':') {
                              *np++ = ':';
                              done = 1;
                              break;
                        }
                        if (*cp == '\\')
                              break;
                        *np++ = *cp;
                  }
                  if (done) {
                        *np = '\0';
                        break;
                  } else { /* name field extends beyond the line */
                        line = fgetln(pfp, &len);
                        if (line == NULL && pfp) {
                              /* Name extends beyond the EOF! */
                              hadreaderr = ferror(pfp);
                              if (hadreaderr)
                                    savederrno = errno;
                              fclose(pfp);
                              pfp = NULL;
                              if (hadreaderr) {
                                    cgetclose();
                                    errno = savederrno;
                                    return (-1);
                              } else {
                                    cgetclose();
                                    return (-1);
                              }
                        } else
                              line[len - 1] = '\0';
                  }
            }
            rp = buf;
            for(cp = nbuf; *cp != '\0'; cp++)
                  if (*cp == '|' || *cp == ':')
                        break;
                  else
                        *rp++ = *cp;

            *rp = '\0';
            /*
             * XXX
             * Last argument of getent here should be nbuf if we want true
             * sequential access in the case of duplicates.
             * With NULL, getent will return the first entry found
             * rather than the duplicate entry record.  This is a
             * matter of semantics that should be resolved.
             */
            status = getent(bp, &dummy, db_array, -1, buf, 0, NULL);
            if (status == -2 || status == -3)
                  (void)cgetclose();

            return (status + 1);
      }
      /* NOTREACHED */
}
#endif

/*
 * Cgetstr retrieves the value of the string capability cap from the
 * capability record pointed to by buf.  A pointer to a decoded, NUL
 * terminated, malloc'd copy of the string is returned in the char *
 * pointed to by str.  The length of the string not including the trailing
 * NUL is returned on success, -1 if the requested string capability
 * couldn't be found, -2 if a system error was encountered (storage
 * allocation failure).
 */
int
cgetstr(char *buf, const char *cap, char **str)
{
      u_int m_room;
      char *bp, *mp;
      int len;
      char *mem;

      /*
       * Find string capability cap
       */
      bp = cgetcap(buf, cap, '=');
      if (bp == NULL)
            return (-1);

      /*
       * Conversion / storage allocation loop ...  Allocate memory in
       * chunks SFRAG in size.
       */
      if ((mem = malloc(SFRAG)) == NULL) {
            errno = ENOMEM;
            return (-2);      /* couldn't even allocate the first fragment */
      }
      m_room = SFRAG;
      mp = mem;

      while (*bp != ':' && *bp != '\0') {
            /*
             * Loop invariants:
             *    There is always room for one more character in mem.
             *    Mp always points just past last character in mem.
             *    Bp always points at next character in buf.
             */
            if (*bp == '^') {
                  bp++;
                  if (*bp == ':' || *bp == '\0')
                        break;      /* drop unfinished escape */
                  if (*bp == '?') {
                        *mp++ = '\177';
                        bp++;
                  } else
                        *mp++ = *bp++ & 037;
            } else if (*bp == '\\') {
                  bp++;
                  if (*bp == ':' || *bp == '\0')
                        break;      /* drop unfinished escape */
                  if ('0' <= *bp && *bp <= '7') {
                        int n, i;

                        n = 0;
                        i = 3;      /* maximum of three octal digits */
                        do {
                              n = n * 8 + (*bp++ - '0');
                        } while (--i && '0' <= *bp && *bp <= '7');
                        *mp++ = n;
                  }
                  else switch (*bp++) {
                        case 'b': case 'B':
                              *mp++ = '\b';
                              break;
                        case 't': case 'T':
                              *mp++ = '\t';
                              break;
                        case 'n': case 'N':
                              *mp++ = '\n';
                              break;
                        case 'f': case 'F':
                              *mp++ = '\f';
                              break;
                        case 'r': case 'R':
                              *mp++ = '\r';
                              break;
                        case 'e': case 'E':
                              *mp++ = ESC;
                              break;
                        case 'c': case 'C':
                              *mp++ = ':';
                              break;
                        default:
                              /*
                               * Catches '\', '^', and
                               *  everything else.
                               */
                              *mp++ = *(bp-1);
                              break;
                  }
            } else
                  *mp++ = *bp++;
            m_room--;

            /*
             * Enforce loop invariant: if no room left in current
             * buffer, try to get some more.
             */
            if (m_room == 0) {
                  size_t size = mp - mem;

                  if ((mem = reallocf(mem, size + SFRAG)) == NULL)
                        return (-2);
                  m_room = SFRAG;
                  mp = mem + size;
            }
      }
      *mp++ = '\0';     /* loop invariant let's us do this */
      m_room--;
      len = mp - mem - 1;

      /*
       * Give back any extra memory and return value and success.
       */
      if (m_room != 0)
            if ((mem = reallocf(mem, (size_t)(mp - mem))) == NULL)
                  return (-2);
      *str = mem;
      return (len);
}

/*
 * Cgetustr retrieves the value of the string capability cap from the
 * capability record pointed to by buf.  The difference between cgetustr()
 * and cgetstr() is that cgetustr does not decode escapes but rather treats
 * all characters literally.  A pointer to a  NUL terminated malloc'd
 * copy of the string is returned in the char pointed to by str.  The
 * length of the string not including the trailing NUL is returned on success,
 * -1 if the requested string capability couldn't be found, -2 if a system
 * error was encountered (storage allocation failure).
 */
int
cgetustr(char *buf, const char *cap, char **str)
{
      u_int m_room;
      char *bp, *mp;
      int len;
      char *mem;

      /*
       * Find string capability cap
       */
      if ((bp = cgetcap(buf, cap, '=')) == NULL)
            return (-1);

      /*
       * Conversion / storage allocation loop ...  Allocate memory in
       * chunks SFRAG in size.
       */
      if ((mem = malloc(SFRAG)) == NULL) {
            errno = ENOMEM;
            return (-2);      /* couldn't even allocate the first fragment */
      }
      m_room = SFRAG;
      mp = mem;

      while (*bp != ':' && *bp != '\0') {
            /*
             * Loop invariants:
             *    There is always room for one more character in mem.
             *    Mp always points just past last character in mem.
             *    Bp always points at next character in buf.
             */
            *mp++ = *bp++;
            m_room--;

            /*
             * Enforce loop invariant: if no room left in current
             * buffer, try to get some more.
             */
            if (m_room == 0) {
                  size_t size = mp - mem;

                  if ((mem = reallocf(mem, size + SFRAG)) == NULL)
                        return (-2);
                  m_room = SFRAG;
                  mp = mem + size;
            }
      }
      *mp++ = '\0';     /* loop invariant let's us do this */
      m_room--;
      len = mp - mem - 1;

      /*
       * Give back any extra memory and return value and success.
       */
      if (m_room != 0)
            if ((mem = reallocf(mem, (size_t)(mp - mem))) == NULL)
                  return (-2);
      *str = mem;
      return (len);
}

/*
 * Cgetnum retrieves the value of the numeric capability cap from the
 * capability record pointed to by buf.  The numeric value is returned in
 * the long pointed to by num.  0 is returned on success, -1 if the requested
 * numeric capability couldn't be found.
 */
int
cgetnum(char *buf, const char *cap, long *num)
{
      long n;
      int base, digit;
      char *bp;

      /*
       * Find numeric capability cap
       */
      bp = cgetcap(buf, cap, '#');
      if (bp == NULL)
            return (-1);

      /*
       * Look at value and determine numeric base:
       *    0x... or 0X...    hexadecimal,
       * else     0...        octal,
       * else                 decimal.
       */
      if (*bp == '0') {
            bp++;
            if (*bp == 'x' || *bp == 'X') {
                  bp++;
                  base = 16;
            } else
                  base = 8;
      } else
            base = 10;

      /*
       * Conversion loop ...
       */
      n = 0;
      for (;;) {
            if ('0' <= *bp && *bp <= '9')
                  digit = *bp - '0';
            else if ('a' <= *bp && *bp <= 'f')
                  digit = 10 + *bp - 'a';
            else if ('A' <= *bp && *bp <= 'F')
                  digit = 10 + *bp - 'A';
            else
                  break;

            if (digit >= base)
                  break;

            n = n * base + digit;
            bp++;
      }

      /*
       * Return value and success.
       */
      *num = n;
      return (0);
}


/*
 * Compare name field of record.
 */
static int
nfcmp(char *nf, char *rec)
{
      char *cp, tmp;
      int ret;

      for (cp = rec; *cp != ':'; cp++)
            ;

      tmp = *(cp + 1);
      *(cp + 1) = '\0';
      ret = strcmp(nf, rec);
      *(cp + 1) = tmp;

      return (ret);
}

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