Djam/kernel-6.6
1
0
Fork 0
mirror of https://abf.rosa.ru/djam/kernel-6.6.git synced 2025-02-25 03:42:46 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions
kernel-6.6/0205-AltHa-handle-setcap-binaries-in-the-same-way-as-setu.patch

150 lines
6.6 KiB
Diff
Raw Blame History

From c71405f7352fd1929313360a34c1431613e92fb6 Mon Sep 17 00:00:00 2001
From: "Vladimir D. Seleznev" <vseleznv@altlinux.org>
Date: Fri, 3 Jun 2022 16:44:41 +0000
Subject: [PATCH] AltHa: handle setcap binaries in the same way as setuid ones
altha.nosuid facility controls what binaries can raise user privilleges.
Prior to this commit it only handled setuid binaries, but it was still
possible to raise privilleges via setcaps. Now it handles both setuid
and setcap binaries.
Signed-off-by: Vladimir D. Seleznev <vseleznv@altlinux.org>
Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
---
Documentation/admin-guide/LSM/AltHa.rst | 6 ++--
security/altha/Kconfig | 2 +-
security/altha/altha_lsm.c | 47 ++++++++++++++++++++-----
3 files changed, 43 insertions(+), 12 deletions(-)
diff --git a/Documentation/admin-guide/LSM/AltHa.rst b/Documentation/admin-guide/LSM/AltHa.rst
index 34d010740bda..fc3ba1486194 100644
--- a/Documentation/admin-guide/LSM/AltHa.rst
+++ b/Documentation/admin-guide/LSM/AltHa.rst
@@ -3,7 +3,7 @@ AltHa
====
AltHa is a Linux Security Module currently has three userspace hardening options:
- * ignore SUID on binaries (with exceptions possible);
+ * ignore SUID and setcaps on binaries (with exceptions possible);
* prevent running selected script interpreters in interactive mode;
* disable open file unlinking in selected dirs.
@@ -14,12 +14,12 @@ through sysctls in ``/proc/sys/kernel/altha``.
NoSUID
============
-Modern Linux systems can be used with minimal (or even zero at least for OWL and ALT) usage of SUID programms, but in many cases in full-featured desktop or server systems there are plenty of them: uncounted and sometimes unnecessary. Privileged programms are always an attack surface, but mounting filesystems with ``nosuid`` flag doesn't provide enough granularity in SUID binaries management. This LSM module provides a single control point for all SUID binaries. When this submodule is enabled, SUID bits on all binaries except explicitly listed are system-wide ignored.
+Modern Linux systems can be used with minimal (or even zero at least for OWL and ALT) usage of SUID programms, but in many cases in full-featured desktop or server systems there are plenty of them: uncounted and sometimes unnecessary. Privileged programms are always an attack surface, but mounting filesystems with ``nosuid`` flag doesn't provide enough granularity in SUID binaries management. This LSM module provides a single control point for all SUID and setcap binaries. When this submodule is enabled, SUID and setcap bits on all binaries except explicitly listed are system-wide ignored.
Sysctl parameters and defaults:
* ``kernel.altha.nosuid.enabled = 0``, set to 1 to enable
-* ``kernel.altha.nosuid.exceptions =``, colon-separated list of enabled SUID binaries, for example: ``/bin/su:/usr/libexec/hasher-priv/hasher-priv``
+* ``kernel.altha.nosuid.exceptions =``, colon-separated list of enabled SUID and setcap binaries, for example: ``/bin/su:/usr/libexec/hasher-priv/hasher-priv``
RestrScript
============
diff --git a/security/altha/Kconfig b/security/altha/Kconfig
index 4bafdef4e58e..cd1dd69cc48d 100644
--- a/security/altha/Kconfig
+++ b/security/altha/Kconfig
@@ -4,7 +4,7 @@ config SECURITY_ALTHA
default n
help
Some hardening options:
- * ignore SUID on binaries (with exceptions possible);
+ * ignore SUID and setcap on binaries (with exceptions possible);
* prevent running selected script interprers in interactive move;
* WxorX for filesystems (with exceptions possible);
diff --git a/security/altha/altha_lsm.c b/security/altha/altha_lsm.c
index 0dfccddb4d45..dc0fec452821 100644
--- a/security/altha/altha_lsm.c
+++ b/security/altha/altha_lsm.c
@@ -11,6 +11,7 @@
#include <linux/lsm_hooks.h>
#include <linux/cred.h>
+#include <linux/capability.h>
#include <linux/sysctl.h>
#include <linux/binfmts.h>
#include <linux/file.h>
@@ -241,6 +242,7 @@ int is_olock_dir(struct inode *inode)
static int altha_bprm_creds_from_file(struct linux_binprm *bprm, struct file * fi)
{
struct altha_list_struct *node;
+ char *setuidcap_str = "setuid";
/* when it's not a shebang issued script interpreter */
if (rstrscript_enabled && bprm->executable == bprm->interpreter) {
char *path_p;
@@ -267,11 +269,37 @@ static int altha_bprm_creds_from_file(struct linux_binprm *bprm, struct file * f
up_read(&interpreters_sem);
kfree(path_buffer);
}
- if (unlikely(nosuid_enabled &&
- !uid_eq(bprm->cred->uid, bprm->cred->euid))) {
+ if (nosuid_enabled) {
char *path_p;
char *path_buffer;
- uid_t cur_uid;
+ int is_setuid = 0, is_setcap = 0;
+ uid_t cur_uid, cur_euid;
+
+ /*
+ * While nosuid is supposed to prevent switching to superuser,
+ * it does not check swtiching to a non-privileged user because
+ * it is almost never used.
+ */
+ is_setuid = !uid_eq(bprm->cred->uid, bprm->cred->euid);
+
+ if (!is_setuid) {
+ cur_euid = from_kuid(bprm->cred->user_ns, bprm->cred->euid);
+ /*
+ * Check capabilities only for effectivly non-superuser
+ * processes: superuser processess always have
+ * capabilities, should keep them so these processes
+ * continue working correctly.
+ */
+ if (cur_euid != (uid_t) 0)
+ is_setcap = !(cap_isclear(bprm->cred->cap_permitted)
+ && cap_isclear(bprm->cred->cap_effective));
+
+ setuidcap_str = "setcap";
+ }
+
+ /* If no suid and no caps detected, exit. */
+ if (!is_setuid && !is_setcap)
+ return 0;
path_buffer = kmalloc(PATH_MAX, GFP_KERNEL);
if (!path_buffer)
@@ -283,8 +311,8 @@ static int altha_bprm_creds_from_file(struct linux_binprm *bprm, struct file * f
list_for_each_entry(node, &nosuid_exceptions_list, list) {
if (strcmp(path_p, node->spath) == 0) {
pr_notice_ratelimited
- ("AltHa/NoSUID: %s permitted to setuid from %d\n",
- bprm->filename, cur_uid);
+ ("AltHa/NoSUID: %s permitted to %s from %d\n",
+ bprm->filename, setuidcap_str, cur_uid);
up_read(&nosuid_exceptions_sem);
kfree(path_buffer);
return 0;
@@ -292,9 +320,12 @@ static int altha_bprm_creds_from_file(struct linux_binprm *bprm, struct file * f
}
up_read(&nosuid_exceptions_sem);
pr_notice_ratelimited
- ("AltHa/NoSUID: %s prevented to setuid from %d\n",
- bprm->filename, cur_uid);
- bprm->cred->euid = bprm->cred->uid;
+ ("AltHa/NoSUID: %s prevented to %s from %d\n",
+ bprm->filename, setuidcap_str, cur_uid);
+ if (is_setuid)
+ bprm->cred->euid = bprm->cred->uid;
+ cap_clear(bprm->cred->cap_permitted);
+ cap_clear(bprm->cred->cap_effective);
kfree(path_buffer);
}
return 0;
--
2.40.1
Reference in a new issue View git blame Copy permalink