pwcache.c

/*	$OpenBSD: pwcache.c,v 1.16 2022/12/27 17:10:06 jmc Exp $	*/

/*-
 * Copyright (c) 1992 Keith Muller.
 * Copyright (c) 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Keith Muller of the University of California, San Diego.
 *
 * 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. 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.
 */

#include <sys/types.h>
#include <bsd/string.h>

#include <assert.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/*
 * Constants and data structures used to implement group and password file
 * caches.  Name lengths have been chosen to be as large as those supported
 * by the passwd and group files as well as the standard archive formats.
 * CACHE SIZES MUST BE PRIME
 */
#define UNMLEN		32	/* >= user name found in any protocol */
#define GNMLEN		32	/* >= group name found in any protocol */
#define UID_SZ		317	/* size of uid to user_name cache */
#define UNM_SZ		317	/* size of user_name to uid cache */
#define GID_SZ		251	/* size of gid to group_name cache */
#define GNM_SZ		251	/* size of group_name to gid cache */
#define VALID		1	/* entry and name are valid */
#define INVALID		2	/* entry valid, name NOT valid */

/*
 * Node structures used in the user, group, uid, and gid caches.
 */

typedef struct uidc {
	int valid;		/* is this a valid or a miss entry */
	char name[UNMLEN];	/* uid name */
	uid_t uid;		/* cached uid */
} UIDC;

typedef struct gidc {
	int valid;		/* is this a valid or a miss entry */
	char name[GNMLEN];	/* gid name */
	gid_t gid;		/* cached gid */
} GIDC;

/*
 * Routines that control user, group, uid and gid caches.
 * Traditional passwd/group cache routines perform quite poorly with
 * archives. The chances of hitting a valid lookup with an archive is quite a
 * bit worse than with files already resident on the file system. These misses
 * create a MAJOR performance cost. To address this problem, these routines
 * cache both hits and misses.
 */

static UIDC **uidtb;	/* uid to name cache */
static GIDC **gidtb;	/* gid to name cache */
static UIDC **usrtb;	/* user name to uid cache */
static GIDC **grptb;	/* group name to gid cache */

static u_int
st_hash(const char *name, size_t len, int tabsz)
{
	u_int key = 0;

	assert(name != NULL);

	while (len--) {
		key += *name++;
		key = (key << 8) | (key >> 24);
	}

	return key % tabsz;
}

/*
 * uidtb_start
 *	creates an an empty uidtb
 * Return:
 *	0 if ok, -1 otherwise
 */
static int
uidtb_start(void)
{
	static int fail = 0;

	if (uidtb != NULL)
		return 0;
	if (fail)
		return -1;
	if ((uidtb = calloc(UID_SZ, sizeof(UIDC *))) == NULL) {
		++fail;
		return -1;
	}
	return 0;
}

/*
 * gidtb_start
 *	creates an an empty gidtb
 * Return:
 *	0 if ok, -1 otherwise
 */
static int
gidtb_start(void)
{
	static int fail = 0;

	if (gidtb != NULL)
		return 0;
	if (fail)
		return -1;
	if ((gidtb = calloc(GID_SZ, sizeof(GIDC *))) == NULL) {
		++fail;
		return -1;
	}
	return 0;
}

/*
 * usrtb_start
 *	creates an an empty usrtb
 * Return:
 *	0 if ok, -1 otherwise
 */
static int
usrtb_start(void)
{
	static int fail = 0;

	if (usrtb != NULL)
		return 0;
	if (fail)
		return -1;
	if ((usrtb = calloc(UNM_SZ, sizeof(UIDC *))) == NULL) {
		++fail;
		return -1;
	}
	return 0;
}

/*
 * grptb_start
 *	creates an an empty grptb
 * Return:
 *	0 if ok, -1 otherwise
 */
static int
grptb_start(void)
{
	static int fail = 0;

	if (grptb != NULL)
		return 0;
	if (fail)
		return -1;
	if ((grptb = calloc(GNM_SZ, sizeof(GIDC *))) == NULL) {
		++fail;
		return -1;
	}
	return 0;
}

/*
 * user_from_uid()
 *	caches the name (if any) for the uid. If noname clear, we always
 *	return the stored name (if valid or invalid match).
 *	We use a simple hash table.
 * Return:
 *	Pointer to stored name (or a empty string)
 */
const char *
user_from_uid(uid_t uid, int noname)
{
	struct passwd pwstore, *pw = NULL;
	char pwbuf[BUFSIZ];
	UIDC **pptr, *ptr = NULL;

	if ((uidtb != NULL) || (uidtb_start() == 0)) {
		/*
		 * see if we have this uid cached
		 */
		pptr = uidtb + (uid % UID_SZ);
		ptr = *pptr;

		if ((ptr != NULL) && (ptr->valid > 0) && (ptr->uid == uid)) {
			/*
			 * have an entry for this uid
			 */
			if (!noname || (ptr->valid == VALID))
				return ptr->name;
			return NULL;
		}

		if (ptr == NULL)
			*pptr = ptr = malloc(sizeof(UIDC));
	}

	getpwuid_r(uid, &pwstore, pwbuf, sizeof(pwbuf), &pw);
	if (pw == NULL) {
		/*
		 * no match for this uid in the local password file
		 * a string that is the uid in numeric format
		 */
		if (ptr == NULL)
			return NULL;
		ptr->uid = uid;
		(void)snprintf(ptr->name, UNMLEN, "%u", uid);
		ptr->valid = INVALID;
		if (noname)
			return NULL;
	} else {
		/*
		 * there is an entry for this uid in the password file
		 */
		if (ptr == NULL)
			return pw->pw_name;
		ptr->uid = uid;
		(void)strlcpy(ptr->name, pw->pw_name, sizeof(ptr->name));
		ptr->valid = VALID;
	}
	return ptr->name;
}

/*
 * group_from_gid()
 *	caches the name (if any) for the gid. If noname clear, we always
 *	return the stored name (if valid or invalid match).
 *	We use a simple hash table.
 * Return:
 *	Pointer to stored name (or a empty string)
 */
const char *
group_from_gid(gid_t gid, int noname)
{
	struct group grstore, *gr = NULL;
	char grbuf[BUFSIZ];
	GIDC **pptr, *ptr = NULL;

	if ((gidtb != NULL) || (gidtb_start() == 0)) {
		/*
		 * see if we have this gid cached
		 */
		pptr = gidtb + (gid % GID_SZ);
		ptr = *pptr;

		if ((ptr != NULL) && (ptr->valid > 0) && (ptr->gid == gid)) {
			/*
			 * have an entry for this gid
			 */
			if (!noname || (ptr->valid == VALID))
				return ptr->name;
			return NULL;
		}

		if (ptr == NULL)
			*pptr = ptr = malloc(sizeof(GIDC));
	}

	getgrgid_r(gid, &grstore, grbuf, sizeof(grbuf), &gr);
	if (gr == NULL) {
		/*
		 * no match for this gid in the local group file, put in
		 * a string that is the gid in numeric format
		 */
		if (ptr == NULL)
			return NULL;
		ptr->gid = gid;
		(void)snprintf(ptr->name, GNMLEN, "%u", gid);
		ptr->valid = INVALID;
		if (noname)
			return NULL;
	} else {
		/*
		 * there is an entry for this group in the group file
		 */
		if (ptr == NULL)
			return gr->gr_name;
		ptr->gid = gid;
		(void)strlcpy(ptr->name, gr->gr_name, sizeof(ptr->name));
		ptr->valid = VALID;
	}
	return ptr->name;
}

/*
 * uid_from_user()
 *	caches the uid for a given user name. We use a simple hash table.
 * Return:
 *	0 if the user name is found (filling in uid), -1 otherwise
 */
int
uid_from_user(const char *name, uid_t *uid)
{
	struct passwd pwstore, *pw = NULL;
	char pwbuf[BUFSIZ];
	UIDC **pptr, *ptr = NULL;
	size_t namelen;

	/*
	 * return -1 for mangled names
	 */
	if (name == NULL || ((namelen = strlen(name)) == 0))
		return -1;

	if ((usrtb != NULL) || (usrtb_start() == 0)) {
		/*
		 * look up in hash table, if found and valid return the uid,
		 * if found and invalid, return a -1
		 */
		pptr = usrtb + st_hash(name, namelen, UNM_SZ);
		ptr = *pptr;

		if ((ptr != NULL) && (ptr->valid > 0) &&
		    strcmp(name, ptr->name) == 0) {
			if (ptr->valid == INVALID)
				return -1;
			*uid = ptr->uid;
			return 0;
		}

		if (ptr == NULL)
			*pptr = ptr = malloc(sizeof(UIDC));
	}

	/*
	 * no match, look it up, if no match store it as an invalid entry,
	 * or store the matching uid
	 */
	getpwnam_r(name, &pwstore, pwbuf, sizeof(pwbuf), &pw);
	if (ptr == NULL) {
		if (pw == NULL)
			return -1;
		*uid = pw->pw_uid;
		return 0;
	}
	(void)strlcpy(ptr->name, name, sizeof(ptr->name));
	if (pw == NULL) {
		ptr->valid = INVALID;
		return -1;
	}
	ptr->valid = VALID;
	*uid = ptr->uid = pw->pw_uid;
	return 0;
}

/*
 * gid_from_group()
 *	caches the gid for a given group name. We use a simple hash table.
 * Return:
 *	0 if the group name is found (filling in gid), -1 otherwise
 */
int
gid_from_group(const char *name, gid_t *gid)
{
	struct group grstore, *gr = NULL;
	char grbuf[BUFSIZ];
	GIDC **pptr, *ptr = NULL;
	size_t namelen;

	/*
	 * return -1 for mangled names
	 */
	if (name == NULL || ((namelen = strlen(name)) == 0))
		return -1;

	if ((grptb != NULL) || (grptb_start() == 0)) {
		/*
		 * look up in hash table, if found and valid return the uid,
		 * if found and invalid, return a -1
		 */
		pptr = grptb + st_hash(name, namelen, GID_SZ);
		ptr = *pptr;

		if ((ptr != NULL) && (ptr->valid > 0) &&
		    strcmp(name, ptr->name) == 0) {
			if (ptr->valid == INVALID)
				return -1;
			*gid = ptr->gid;
			return 0;
		}

		if (ptr == NULL)
			*pptr = ptr = malloc(sizeof(GIDC));
	}

	/*
	 * no match, look it up, if no match store it as an invalid entry,
	 * or store the matching gid
	 */
	getgrnam_r(name, &grstore, grbuf, sizeof(grbuf), &gr);
	if (ptr == NULL) {
		if (gr == NULL)
			return -1;
		*gid = gr->gr_gid;
		return 0;
	}

	(void)strlcpy(ptr->name, name, sizeof(ptr->name));
	if (gr == NULL) {
		ptr->valid = INVALID;
		return -1;
	}
	ptr->valid = VALID;
	*gid = ptr->gid = gr->gr_gid;
	return 0;
}