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login: extract get_hushlogin_status 

Signed-off-by: Ondrej Oprala <ooprala@redhat.com>
This commit is contained in:
Ondrej Oprala 2014-04-08 13:26:33 +02:00 committed by Karel Zak
parent 914e20a00a
commit 78dd745089
3 changed files with 124 additions and 118 deletions
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118
login-utils/login.c
View File

@ -920,124 +920,6 @@ static void loginpam_session(struct login_context *cxt)
}
}
/*
* We need to check the effective UID/GID. For example, $HOME could be on a
* root-squashed NFS or on an NFS with UID mapping, and access(2) uses the
* real UID/GID. Then open(2) seems as the surest solution.
* -- kzak@redhat.com (10-Apr-2009)
*/
static int effective_access(const char *path, int mode)
{
int fd = open(path, mode);
if (fd != -1)
close(fd);
return fd == -1 ? -1 : 0;
}
/*
* Check the per-account or the global hush-login setting.
*
* Hushed mode is enabled:
*
* a) if a global (e.g. /etc/hushlogins) hush file exists:
* 1) for ALL ACCOUNTS if the file is empty
* 2) for the current user if the username or shell is found in the file
*
* b) if a ~/.hushlogin file exists
*
* The ~/.hushlogin file is ignored if the global hush file exists.
*
* The HUSHLOGIN_FILE login.def variable overrides the default hush filename.
*
* Note that shadow-utils login(1) does not support "a1)". The "a1)" is
* necessary if you want to use PAM for "Last login" message.
*
* -- Karel Zak <kzak@redhat.com> (26-Aug-2011)
*
*
* The per-account check requires some explanation: As root we may not be able
* to read the directory of the user if it is on an NFS-mounted filesystem. We
* temporarily set our effective uid to the user-uid, making sure that we keep
* root privileges in the real uid.
*
* A portable solution would require a fork(), but we rely on Linux having the
* BSD setreuid().
*/
static int get_hushlogin_status(struct passwd *pwd)
{
const char *files[] = { _PATH_HUSHLOGINS, _PATH_HUSHLOGIN, NULL };
const char *file;
char buf[BUFSIZ];
int i;
file = getlogindefs_str("HUSHLOGIN_FILE", NULL);
if (file) {
if (!*file)
return 0; /* empty HUSHLOGIN_FILE defined */
files[0] = file;
files[1] = NULL;
}
for (i = 0; files[i]; i++) {
int ok = 0;
file = files[i];
/* global hush-file */
if (*file == '/') {
struct stat st;
FILE *f;
if (stat(file, &st) != 0)
continue; /* file does not exist */
if (st.st_size == 0)
return 1; /* for all accounts */
f = fopen(file, "r");
if (!f)
continue; /* ignore errors... */
while (ok == 0 && fgets(buf, sizeof(buf), f)) {
buf[strlen(buf) - 1] = '\0';
ok = !strcmp(buf, *buf == '/' ? pwd->pw_shell :
pwd->pw_name);
}
fclose(f);
if (ok)
return 1; /* found username/shell */
return 0; /* ignore per-account files */
}
/* per-account setting */
if (strlen(pwd->pw_dir) + sizeof(file) + 2 > sizeof(buf))
continue;
else {
uid_t ruid = getuid();
gid_t egid = getegid();
sprintf(buf, "%s/%s", pwd->pw_dir, file);
if (setregid(-1, pwd->pw_gid) == 0 &&
setreuid(0, pwd->pw_uid) == 0)
ok = effective_access(buf, O_RDONLY) == 0;
if (setuid(0) != 0 ||
setreuid(ruid, 0) != 0 ||
setregid(-1, egid) != 0) {
syslog(LOG_ALERT, _("hush login status: restore original IDs failed"));
exit(EXIT_FAILURE);
}
if (ok)
return 1; /* enabled by user */
}
}
return 0;
}
/*
* Detach the controlling terminal, fork, restore syslog stuff, and create
* a new session.

122
login-utils/logindefs.c
View File

@ -27,6 +27,9 @@
#include <stdlib.h>
#include <string.h>
#include <sys/syslog.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <pwd.h>
#include "c.h"
#include "closestream.h"
@ -259,6 +262,125 @@ int logindefs_setenv(const char *name, const char *conf, const char *dflt)
return val ? setenv(name, val, 1) : -1;
}
/*
* We need to check the effective UID/GID. For example, $HOME could be on a
* root-squashed NFS or on an NFS with UID mapping, and access(2) uses the
* real UID/GID. Then open(2) seems as the surest solution.
* -- kzak@redhat.com (10-Apr-2009)
*/
int effective_access(const char *path, int mode)
{
int fd = open(path, mode);
if (fd != -1)
close(fd);
return fd == -1 ? -1 : 0;
}
/*
* Check the per-account or the global hush-login setting.
*
* Hushed mode is enabled:
*
* a) if a global (e.g. /etc/hushlogins) hush file exists:
* 1) for ALL ACCOUNTS if the file is empty
* 2) for the current user if the username or shell is found in the file
*
* b) if a ~/.hushlogin file exists
*
* The ~/.hushlogin file is ignored if the global hush file exists.
*
* The HUSHLOGIN_FILE login.def variable overrides the default hush filename.
*
* Note that shadow-utils login(1) does not support "a1)". The "a1)" is
* necessary if you want to use PAM for "Last login" message.
*
* -- Karel Zak <kzak@redhat.com> (26-Aug-2011)
*
*
* The per-account check requires some explanation: As root we may not be able
* to read the directory of the user if it is on an NFS-mounted filesystem. We
* temporarily set our effective uid to the user-uid, making sure that we keep
* root privileges in the real uid.
*
* A portable solution would require a fork(), but we rely on Linux having the
* BSD setreuid().
*/
int get_hushlogin_status(struct passwd *pwd)
{
const char *files[] = { _PATH_HUSHLOGINS, _PATH_HUSHLOGIN, NULL };
const char *file;
char buf[BUFSIZ];
int i;
file = getlogindefs_str("HUSHLOGIN_FILE", NULL);
if (file) {
if (!*file)
return 0; /* empty HUSHLOGIN_FILE defined */
files[0] = file;
files[1] = NULL;
}
for (i = 0; files[i]; i++) {
int ok = 0;
file = files[i];
/* global hush-file */
if (*file == '/') {
struct stat st;
FILE *f;
if (stat(file, &st) != 0)
continue; /* file does not exist */
if (st.st_size == 0)
return 1; /* for all accounts */
f = fopen(file, "r");
if (!f)
continue; /* ignore errors... */
while (ok == 0 && fgets(buf, sizeof(buf), f)) {
buf[strlen(buf) - 1] = '\0';
ok = !strcmp(buf, *buf == '/' ? pwd->pw_shell :
pwd->pw_name);
}
fclose(f);
if (ok)
return 1; /* found username/shell */
return 0; /* ignore per-account files */
}
/* per-account setting */
if (strlen(pwd->pw_dir) + sizeof(file) + 2 > sizeof(buf))
continue;
else {
uid_t ruid = getuid();
gid_t egid = getegid();
sprintf(buf, "%s/%s", pwd->pw_dir, file);
if (setregid(-1, pwd->pw_gid) == 0 &&
setreuid(0, pwd->pw_uid) == 0)
ok = effective_access(buf, O_RDONLY) == 0;
if (setuid(0) != 0 ||
setreuid(ruid, 0) != 0 ||
setregid(-1, egid) != 0) {
syslog(LOG_ALERT, _("hush login status: restore original IDs failed"));
exit(EXIT_FAILURE);
}
if (ok)
return 1; /* enabled by user */
}
}
return 0;
}
#ifdef TEST_PROGRAM
int main(int argc, char *argv[])
{

2
login-utils/logindefs.h
View File

@ -8,5 +8,7 @@ extern unsigned long getlogindefs_num(const char *name, long dflt);
extern const char *getlogindefs_str(const char *name, const char *dflt);
extern void free_getlogindefs_data(void);
extern int logindefs_setenv(const char *name, const char *conf, const char *dflt);
extern int effective_access(const char *path, int mode);
extern int get_hushlogin_status(struct passwd *pwd);
#endif /* UTIL_LINUX_LOGINDEFS_H */