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Diffstat (limited to '')
| -rw-r--r-- | lib/idcache.c | 228 |
1 files changed, 228 insertions, 0 deletions
diff --git a/lib/idcache.c b/lib/idcache.c new file mode 100644 index 0000000..580a627 --- /dev/null +++ b/lib/idcache.c @@ -0,0 +1,228 @@ +/* idcache.c -- map user and group IDs, cached for speed + + Copyright (C) 1985, 1988-1990, 1997-1998, 2003, 2005-2007, 2009-2022 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; +} |