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Refuse to load a module if it is owned by anyone else than root or the 

arbitrator or it is writable by group or other.


git-svn-id: svn+ssh://svn.openpam.org/svn/openpam/trunk@493 185d5e19-27fe-0310-9dcf-9bff6b9f3609
This commit is contained in:
Dag-Erling Smørgrav 2011-11-20 02:28:15 +00:00
parent b011e58526
commit d98f755c25
1 changed files with 64 additions and 8 deletions
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72
lib/openpam_dynamic.c
View File

@ -39,10 +39,16 @@
# include "config.h"
#endif
#include <sys/types.h>
#include <sys/stat.h>
#include <dlfcn.h>
#include <errno.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <security/pam_appl.h>
@ -52,6 +58,57 @@
#define RTLD_NOW RTLD_LAZY
#endif
/*
* OpenPAM internal
*
* Verify that a file or directory is owned by either root or the
* arbitrator and that it is not writable by group or other.
*/
static int
check_owner_perms(const char *path)
{
struct stat sb;
if (stat(path, &sb) != 0)
return (-1);
if ((sb.st_uid != 0 && sb.st_uid != geteuid()) ||
(sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) {
openpam_log(PAM_LOG_ERROR,
"%s: insecure ownership or permissions", path);
errno = EPERM;
return (-1);
}
return (0);
}
/*
* OpenPAM internal
*
* Perform sanity checks and attempt to load a module
*/
static void *
try_dlopen(const char *modfn)
{
char *moddn;
int ok, serrno;
/*
* BSD dirname(3) returns a pointer to a static buffer, while GNU
* dirname(3) modifies the input string. Use a copy of the string
* so both cases work.
*/
if ((moddn = strdup(modfn)) == NULL)
return (NULL);
ok = (check_owner_perms(dirname(moddn)) == 0 &&
check_owner_perms(modfn) == 0);
serrno = errno;
free(moddn);
errno = serrno;
return (ok ? dlopen(modfn, RTLD_NOW) : NULL);
}
/*
* OpenPAM internal
*
@ -66,7 +123,7 @@ openpam_dynamic(const char *path)
const char *prefix;
char *vpath;
void *dlh;
int i;
int i, serrno;
dlh = NULL;
@ -79,16 +136,15 @@ openpam_dynamic(const char *path)
/* try versioned module first, then unversioned module */
if (asprintf(&vpath, "%s%s.%d", prefix, path, LIB_MAJ) < 0)
goto err;
if ((dlh = dlopen(vpath, RTLD_NOW)) == NULL) {
openpam_log(PAM_LOG_DEBUG, "%s: %s", vpath, dlerror());
if ((dlh = try_dlopen(vpath)) == NULL && errno == ENOENT) {
*strrchr(vpath, '.') = '\0';
if ((dlh = dlopen(vpath, RTLD_NOW)) == NULL) {
openpam_log(PAM_LOG_DEBUG, "%s: %s", vpath, dlerror());
FREE(vpath);
return (NULL);
}
dlh = try_dlopen(vpath);
}
serrno = errno;
FREE(vpath);
errno = serrno;
if (dlh == NULL)
goto err;
if ((module = calloc(1, sizeof *module)) == NULL)
goto buf_err;
if ((module->path = strdup(path)) == NULL)