getcap.c

早期freebsd实现

/*-
 * 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/types.h>

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

#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 */

static int	cdbget __P((DB *, char **, char *));
static int 	getent __P((char **, u_int *, char **, int, char *, int, char *));
static int	nfcmp __P((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(ent)
	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(buf, cap, type)
	char *buf, *cap;
	int type;
{
	register char *bp, *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(buf, db_array, name)
	char **buf, **db_array, *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(cap, len, db_array, fd, name, depth, nfield)
	char **cap, **db_array, *name, *nfield;
	u_int *len;
	int fd, depth;
{
	DB *capdbp;
	DBT key, data;
	register char *r_end, *rp, **db_p;
	int myfd, eof, foundit, retval, clen;
	char *record, *cbuf;
	int tc_not_resolved;
	char pbuf[_POSIX_PATH_MAX];
	
	/*
	 * 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, L_SET);
			myfd = 0;
		} else {
			(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 {
				fd = open(*db_p, O_RDONLY, 0);
				if (fd < 0) {
					/* No error on unfound file. */
					if (errno == ENOENT)
						continue;
					free(record);
					return (-2);
				}
				myfd = 1;
			}
		}
		/*
		 * Find the requested capability record ...
		 */
		{
		char buf[BUFSIZ];
		register char *b_end, *bp;
		register 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 = realloc(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)
		return (-1);

	/*
	 * Got the capability record, but now we have to expand all tc=name
	 * references in it ...
	 */
tc_exp:	{
		register char *newicap, *s;
		register 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 = realloc(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 */