qemu/hw/9pfs/9p-posix-acl.c
Greg Kurz 72f0d0bf51 9pfs: local: lremovexattr: don't follow symlinks
The local_lremovexattr() callback is vulnerable to symlink attacks because
it calls lremovexattr() which follows symbolic links in all path elements
but the rightmost one.

This patch introduces a helper to emulate the non-existing fremovexattrat()
function: it is implemented with /proc/self/fd which provides a trusted
path that can be safely passed to lremovexattr().

local_lremovexattr() is converted to use this helper and opendir_nofollow().

This partly fixes CVE-2016-9602.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-28 11:21:15 +01:00

157 lines
4.1 KiB
C

/*
* 9p system.posix* xattr callback
*
* Copyright IBM, Corp. 2010
*
* Authors:
* Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qemu/xattr.h"
#include "9p.h"
#include "fsdev/file-op-9p.h"
#include "9p-xattr.h"
#define MAP_ACL_ACCESS "user.virtfs.system.posix_acl_access"
#define MAP_ACL_DEFAULT "user.virtfs.system.posix_acl_default"
#define ACL_ACCESS "system.posix_acl_access"
#define ACL_DEFAULT "system.posix_acl_default"
static ssize_t mp_pacl_getxattr(FsContext *ctx, const char *path,
const char *name, void *value, size_t size)
{
return local_getxattr_nofollow(ctx, path, MAP_ACL_ACCESS, value, size);
}
static ssize_t mp_pacl_listxattr(FsContext *ctx, const char *path,
char *name, void *value, size_t osize)
{
ssize_t len = sizeof(ACL_ACCESS);
if (!value) {
return len;
}
if (osize < len) {
errno = ERANGE;
return -1;
}
/* len includes the trailing NUL */
memcpy(value, ACL_ACCESS, len);
return 0;
}
static int mp_pacl_setxattr(FsContext *ctx, const char *path, const char *name,
void *value, size_t size, int flags)
{
return local_setxattr_nofollow(ctx, path, MAP_ACL_ACCESS, value, size,
flags);
}
static int mp_pacl_removexattr(FsContext *ctx,
const char *path, const char *name)
{
int ret;
ret = local_removexattr_nofollow(ctx, path, MAP_ACL_ACCESS);
if (ret == -1 && errno == ENODATA) {
/*
* We don't get ENODATA error when trying to remove a
* posix acl that is not present. So don't throw the error
* even in case of mapped security model
*/
errno = 0;
ret = 0;
}
return ret;
}
static ssize_t mp_dacl_getxattr(FsContext *ctx, const char *path,
const char *name, void *value, size_t size)
{
return local_getxattr_nofollow(ctx, path, MAP_ACL_DEFAULT, value, size);
}
static ssize_t mp_dacl_listxattr(FsContext *ctx, const char *path,
char *name, void *value, size_t osize)
{
ssize_t len = sizeof(ACL_DEFAULT);
if (!value) {
return len;
}
if (osize < len) {
errno = ERANGE;
return -1;
}
/* len includes the trailing NUL */
memcpy(value, ACL_DEFAULT, len);
return 0;
}
static int mp_dacl_setxattr(FsContext *ctx, const char *path, const char *name,
void *value, size_t size, int flags)
{
return local_setxattr_nofollow(ctx, path, MAP_ACL_DEFAULT, value, size,
flags);
}
static int mp_dacl_removexattr(FsContext *ctx,
const char *path, const char *name)
{
int ret;
ret = local_removexattr_nofollow(ctx, path, MAP_ACL_DEFAULT);
if (ret == -1 && errno == ENODATA) {
/*
* We don't get ENODATA error when trying to remove a
* posix acl that is not present. So don't throw the error
* even in case of mapped security model
*/
errno = 0;
ret = 0;
}
return ret;
}
XattrOperations mapped_pacl_xattr = {
.name = "system.posix_acl_access",
.getxattr = mp_pacl_getxattr,
.setxattr = mp_pacl_setxattr,
.listxattr = mp_pacl_listxattr,
.removexattr = mp_pacl_removexattr,
};
XattrOperations mapped_dacl_xattr = {
.name = "system.posix_acl_default",
.getxattr = mp_dacl_getxattr,
.setxattr = mp_dacl_setxattr,
.listxattr = mp_dacl_listxattr,
.removexattr = mp_dacl_removexattr,
};
XattrOperations passthrough_acl_xattr = {
.name = "system.posix_acl_",
.getxattr = pt_getxattr,
.setxattr = pt_setxattr,
.listxattr = pt_listxattr,
.removexattr = pt_removexattr,
};
XattrOperations none_acl_xattr = {
.name = "system.posix_acl_",
.getxattr = notsup_getxattr,
.setxattr = notsup_setxattr,
.listxattr = notsup_listxattr,
.removexattr = notsup_removexattr,
};