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/* idcache.c -- map user and group IDs, cached for speed
Copyright (C) 1985, 1988-1990, 1997-1998, 2003, 2005-2007, 2009-2023 Free
Software Foundation, Inc.
This program 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 3 of the License, or
(at your option) any later version.
This program 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 this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
#include "idcache.h"
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <pwd.h>
#include <grp.h>
#include <unistd.h>
#include "flexmember.h"
#include "xalloc.h"
#ifdef __DJGPP__
static char digits[] = "0123456789";
#endif
struct userid
{
union
{
uid_t u;
gid_t g;
} id;
struct userid *next;
char name[FLEXIBLE_ARRAY_MEMBER];
};
/* FIXME: provide a function to free any malloc'd storage and reset lists,
so that an application can use code like this just before exiting:
#if defined GCC_LINT || defined lint
idcache_clear ();
#endif
*/
static struct userid *user_alist;
/* Each entry on list is a user name for which the first lookup failed. */
static struct userid *nouser_alist;
/* Use the same struct as for userids. */
static struct userid *group_alist;
/* Each entry on list is a group name for which the first lookup failed. */
static struct userid *nogroup_alist;
/* Translate UID to a login name, with cache, or NULL if unresolved. */
char *
getuser (uid_t uid)
{
struct userid *tail;
struct userid *match = NULL;
for (tail = user_alist; tail; tail = tail->next)
{
if (tail->id.u == uid)
{
match = tail;
break;
}
}
if (match == NULL)
{
struct passwd *pwent = getpwuid (uid);
char const *name = pwent ? pwent->pw_name : "";
match = xmalloc (FLEXSIZEOF (struct userid, name, strlen (name) + 1));
match->id.u = uid;
strcpy (match->name, name);
/* Add to the head of the list, so most recently used is first. */
match->next = user_alist;
user_alist = match;
}
return match->name[0] ? match->name : NULL;
}
/* Translate USER to a UID, with cache.
Return NULL if there is no such user.
(We also cache which user names have no passwd entry,
so we don't keep looking them up.) */
uid_t *
getuidbyname (const char *user)
{
struct userid *tail;
struct passwd *pwent;
for (tail = user_alist; tail; tail = tail->next)
/* Avoid a function call for the most common case. */
if (*tail->name == *user && !strcmp (tail->name, user))
return &tail->id.u;
for (tail = nouser_alist; tail; tail = tail->next)
/* Avoid a function call for the most common case. */
if (*tail->name == *user && !strcmp (tail->name, user))
return NULL;
pwent = getpwnam (user);
#ifdef __DJGPP__
/* We need to pretend to be the user USER, to make
pwd functions know about an arbitrary user name. */
if (!pwent && strspn (user, digits) < strlen (user))
{
setenv ("USER", user, 1);
pwent = getpwnam (user); /* now it will succeed */
}
#endif
tail = xmalloc (FLEXSIZEOF (struct userid, name, strlen (user) + 1));
strcpy (tail->name, user);
/* Add to the head of the list, so most recently used is first. */
if (pwent)
{
tail->id.u = pwent->pw_uid;
tail->next = user_alist;
user_alist = tail;
return &tail->id.u;
}
tail->next = nouser_alist;
nouser_alist = tail;
return NULL;
}
/* Translate GID to a group name, with cache, or NULL if unresolved. */
char *
getgroup (gid_t gid)
{
struct userid *tail;
struct userid *match = NULL;
for (tail = group_alist; tail; tail = tail->next)
{
if (tail->id.g == gid)
{
match = tail;
break;
}
}
if (match == NULL)
{
struct group *grent = getgrgid (gid);
char const *name = grent ? grent->gr_name : "";
match = xmalloc (FLEXSIZEOF (struct userid, name, strlen (name) + 1));
match->id.g = gid;
strcpy (match->name, name);
/* Add to the head of the list, so most recently used is first. */
match->next = group_alist;
group_alist = match;
}
return match->name[0] ? match->name : NULL;
}
/* Translate GROUP to a GID, with cache.
Return NULL if there is no such group.
(We also cache which group names have no group entry,
so we don't keep looking them up.) */
gid_t *
getgidbyname (const char *group)
{
struct userid *tail;
struct group *grent;
for (tail = group_alist; tail; tail = tail->next)
/* Avoid a function call for the most common case. */
if (*tail->name == *group && !strcmp (tail->name, group))
return &tail->id.g;
for (tail = nogroup_alist; tail; tail = tail->next)
/* Avoid a function call for the most common case. */
if (*tail->name == *group && !strcmp (tail->name, group))
return NULL;
grent = getgrnam (group);
#ifdef __DJGPP__
/* We need to pretend to belong to group GROUP, to make
grp functions know about an arbitrary group name. */
if (!grent && strspn (group, digits) < strlen (group))
{
setenv ("GROUP", group, 1);
grent = getgrnam (group); /* now it will succeed */
}
#endif
tail = xmalloc (FLEXSIZEOF (struct userid, name, strlen (group) + 1));
strcpy (tail->name, group);
/* Add to the head of the list, so most recently used is first. */
if (grent)
{
tail->id.g = grent->gr_gid;
tail->next = group_alist;
group_alist = tail;
return &tail->id.g;
}
tail->next = nogroup_alist;
nogroup_alist = tail;
return NULL;
}
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