1 /* idcache.c -- map user and group IDs, cached for speed
3 Copyright (C) 1985, 1988, 1989, 1990, 1997, 1998, 2003, 2005-2007
4 Free Software Foundation, Inc.
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software Foundation,
18 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
34 static char digits[] = "0123456789";
45 char name[FLEXIBLE_ARRAY_MEMBER];
48 /* FIXME: provide a function to free any malloc'd storage and reset lists,
49 so that an application can use code like this just before exiting:
55 static struct userid *user_alist;
57 /* Each entry on list is a user name for which the first lookup failed. */
58 static struct userid *nouser_alist;
60 /* Use the same struct as for userids. */
61 static struct userid *group_alist;
63 /* Each entry on list is a group name for which the first lookup failed. */
64 static struct userid *nogroup_alist;
66 /* Translate UID to a login name, with cache, or NULL if unresolved. */
72 struct userid *match = NULL;
74 for (tail = user_alist; tail; tail = tail->next)
76 if (tail->id.u == uid)
85 struct passwd *pwent = getpwuid (uid);
86 char const *name = pwent ? pwent->pw_name : "";
87 match = xmalloc (offsetof (struct userid, name) + strlen (name) + 1);
89 strcpy (match->name, name);
91 /* Add to the head of the list, so most recently used is first. */
92 match->next = user_alist;
96 return match->name[0] ? match->name : NULL;
99 /* Translate USER to a UID, with cache.
100 Return NULL if there is no such user.
101 (We also cache which user names have no passwd entry,
102 so we don't keep looking them up.) */
105 getuidbyname (const char *user)
108 struct passwd *pwent;
110 for (tail = user_alist; tail; tail = tail->next)
111 /* Avoid a function call for the most common case. */
112 if (*tail->name == *user && !strcmp (tail->name, user))
115 for (tail = nouser_alist; tail; tail = tail->next)
116 /* Avoid a function call for the most common case. */
117 if (*tail->name == *user && !strcmp (tail->name, user))
120 pwent = getpwnam (user);
122 /* We need to pretend to be the user USER, to make
123 pwd functions know about an arbitrary user name. */
124 if (!pwent && strspn (user, digits) < strlen (user))
126 setenv ("USER", user, 1);
127 pwent = getpwnam (user); /* now it will succeed */
131 tail = xmalloc (offsetof (struct userid, name) + strlen (user) + 1);
132 strcpy (tail->name, user);
134 /* Add to the head of the list, so most recently used is first. */
137 tail->id.u = pwent->pw_uid;
138 tail->next = user_alist;
143 tail->next = nouser_alist;
148 /* Translate GID to a group name, with cache, or NULL if unresolved. */
154 struct userid *match = NULL;
156 for (tail = group_alist; tail; tail = tail->next)
158 if (tail->id.g == gid)
167 struct group *grent = getgrgid (gid);
168 char const *name = grent ? grent->gr_name : "";
169 match = xmalloc (offsetof (struct userid, name) + strlen (name) + 1);
171 strcpy (match->name, name);
173 /* Add to the head of the list, so most recently used is first. */
174 match->next = group_alist;
178 return match->name[0] ? match->name : NULL;
181 /* Translate GROUP to a GID, with cache.
182 Return NULL if there is no such group.
183 (We also cache which group names have no group entry,
184 so we don't keep looking them up.) */
187 getgidbyname (const char *group)
192 for (tail = group_alist; tail; tail = tail->next)
193 /* Avoid a function call for the most common case. */
194 if (*tail->name == *group && !strcmp (tail->name, group))
197 for (tail = nogroup_alist; tail; tail = tail->next)
198 /* Avoid a function call for the most common case. */
199 if (*tail->name == *group && !strcmp (tail->name, group))
202 grent = getgrnam (group);
204 /* We need to pretend to belong to group GROUP, to make
205 grp functions know about an arbitrary group name. */
206 if (!grent && strspn (group, digits) < strlen (group))
208 setenv ("GROUP", group, 1);
209 grent = getgrnam (group); /* now it will succeed */
213 tail = xmalloc (offsetof (struct userid, name) + strlen (group) + 1);
214 strcpy (tail->name, group);
216 /* Add to the head of the list, so most recently used is first. */
219 tail->id.g = grent->gr_gid;
220 tail->next = group_alist;
225 tail->next = nogroup_alist;
226 nogroup_alist = tail;