lkml.org 
[lkml]   [2017]   [May]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 11/17] doc: ReSTify Yama.txt
Date
Adjusts for ReST markup and moves under LSM admin guide.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
.../Yama.txt => admin-guide/LSM/Yama.rst} | 55 ++++++++++++----------
Documentation/admin-guide/LSM/index.rst | 1 +
Documentation/security/00-INDEX | 2 -
MAINTAINERS | 1 +
security/yama/Kconfig | 3 +-
5 files changed, 33 insertions(+), 29 deletions(-)
rename Documentation/{security/Yama.txt => admin-guide/LSM/Yama.rst} (60%)

diff --git a/Documentation/security/Yama.txt b/Documentation/admin-guide/LSM/Yama.rst
similarity index 60%
rename from Documentation/security/Yama.txt
rename to Documentation/admin-guide/LSM/Yama.rst
index d9ee7d7a6c7f..13468ea696b7 100644
--- a/Documentation/security/Yama.txt
+++ b/Documentation/admin-guide/LSM/Yama.rst
@@ -1,13 +1,14 @@
+====
+Yama
+====
+
Yama is a Linux Security Module that collects system-wide DAC security
protections that are not handled by the core kernel itself. This is
-selectable at build-time with CONFIG_SECURITY_YAMA, and can be controlled
-at run-time through sysctls in /proc/sys/kernel/yama:
-
-- ptrace_scope
+selectable at build-time with ``CONFIG_SECURITY_YAMA``, and can be controlled
+at run-time through sysctls in ``/proc/sys/kernel/yama``:

-==============================================================
-
-ptrace_scope:
+ptrace_scope
+============

As Linux grows in popularity, it will become a larger target for
malware. One particularly troubling weakness of the Linux process
@@ -25,47 +26,49 @@ exist and remain possible if ptrace is allowed to operate as before.
Since ptrace is not commonly used by non-developers and non-admins, system
builders should be allowed the option to disable this debugging system.

-For a solution, some applications use prctl(PR_SET_DUMPABLE, ...) to
+For a solution, some applications use ``prctl(PR_SET_DUMPABLE, ...)`` to
specifically disallow such ptrace attachment (e.g. ssh-agent), but many
do not. A more general solution is to only allow ptrace directly from a
parent to a child process (i.e. direct "gdb EXE" and "strace EXE" still
-work), or with CAP_SYS_PTRACE (i.e. "gdb --pid=PID", and "strace -p PID"
+work), or with ``CAP_SYS_PTRACE`` (i.e. "gdb --pid=PID", and "strace -p PID"
still work as root).

In mode 1, software that has defined application-specific relationships
between a debugging process and its inferior (crash handlers, etc),
-prctl(PR_SET_PTRACER, pid, ...) can be used. An inferior can declare which
-other process (and its descendants) are allowed to call PTRACE_ATTACH
+``prctl(PR_SET_PTRACER, pid, ...)`` can be used. An inferior can declare which
+other process (and its descendants) are allowed to call ``PTRACE_ATTACH``
against it. Only one such declared debugging process can exists for
each inferior at a time. For example, this is used by KDE, Chromium, and
Firefox's crash handlers, and by Wine for allowing only Wine processes
to ptrace each other. If a process wishes to entirely disable these ptrace
-restrictions, it can call prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, ...)
+restrictions, it can call ``prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, ...)``
so that any otherwise allowed process (even those in external pid namespaces)
may attach.

-The sysctl settings (writable only with CAP_SYS_PTRACE) are:
+The sysctl settings (writable only with ``CAP_SYS_PTRACE``) are:

-0 - classic ptrace permissions: a process can PTRACE_ATTACH to any other
+0 - classic ptrace permissions:
+ a process can ``PTRACE_ATTACH`` to any other
process running under the same uid, as long as it is dumpable (i.e.
did not transition uids, start privileged, or have called
- prctl(PR_SET_DUMPABLE...) already). Similarly, PTRACE_TRACEME is
+ ``prctl(PR_SET_DUMPABLE...)`` already). Similarly, ``PTRACE_TRACEME`` is
unchanged.

-1 - restricted ptrace: a process must have a predefined relationship
- with the inferior it wants to call PTRACE_ATTACH on. By default,
+1 - restricted ptrace:
+ a process must have a predefined relationship
+ with the inferior it wants to call ``PTRACE_ATTACH`` on. By default,
this relationship is that of only its descendants when the above
classic criteria is also met. To change the relationship, an
- inferior can call prctl(PR_SET_PTRACER, debugger, ...) to declare
- an allowed debugger PID to call PTRACE_ATTACH on the inferior.
- Using PTRACE_TRACEME is unchanged.
+ inferior can call ``prctl(PR_SET_PTRACER, debugger, ...)`` to declare
+ an allowed debugger PID to call ``PTRACE_ATTACH`` on the inferior.
+ Using ``PTRACE_TRACEME`` is unchanged.

-2 - admin-only attach: only processes with CAP_SYS_PTRACE may use ptrace
- with PTRACE_ATTACH, or through children calling PTRACE_TRACEME.
+2 - admin-only attach:
+ only processes with ``CAP_SYS_PTRACE`` may use ptrace
+ with ``PTRACE_ATTACH``, or through children calling ``PTRACE_TRACEME``.

-3 - no attach: no processes may use ptrace with PTRACE_ATTACH nor via
- PTRACE_TRACEME. Once set, this sysctl value cannot be changed.
+3 - no attach:
+ no processes may use ptrace with ``PTRACE_ATTACH`` nor via
+ ``PTRACE_TRACEME``. Once set, this sysctl value cannot be changed.

The original children-only logic was based on the restrictions in grsecurity.
-
-==============================================================
diff --git a/Documentation/admin-guide/LSM/index.rst b/Documentation/admin-guide/LSM/index.rst
index 6aa4e0dc588b..e5ba2c69b8ef 100644
--- a/Documentation/admin-guide/LSM/index.rst
+++ b/Documentation/admin-guide/LSM/index.rst
@@ -36,3 +36,4 @@ the one "major" module (e.g. SELinux) if there is one configured.
apparmor
SELinux
tomoyo
+ Yama
diff --git a/Documentation/security/00-INDEX b/Documentation/security/00-INDEX
index 04ef62511ea1..a55f781be0dd 100644
--- a/Documentation/security/00-INDEX
+++ b/Documentation/security/00-INDEX
@@ -2,8 +2,6 @@
- this file.
Smack.txt
- documentation on the Smack Linux Security Module.
-Yama.txt
- - documentation on the Yama Linux Security Module.
keys-ecryptfs.txt
- description of the encryption keys for the ecryptfs filesystem.
keys-request-key.txt
diff --git a/MAINTAINERS b/MAINTAINERS
index 184cdd32a67e..c72830e888f1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11573,6 +11573,7 @@ M: Kees Cook <keescook@chromium.org>
T: git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git yama/tip
S: Supported
F: security/yama/
+F: Documentation/admin-guide/LSM/Yama.rst

SENSABLE PHANTOM
M: Jiri Slaby <jirislaby@gmail.com>
diff --git a/security/yama/Kconfig b/security/yama/Kconfig
index 90c605eea892..96b27405558a 100644
--- a/security/yama/Kconfig
+++ b/security/yama/Kconfig
@@ -7,6 +7,7 @@ config SECURITY_YAMA
system-wide security settings beyond regular Linux discretionary
access controls. Currently available is ptrace scope restriction.
Like capabilities, this security module stacks with other LSMs.
- Further information can be found in Documentation/security/Yama.txt.
+ Further information can be found in
+ Documentation/admin-guide/LSM/Yama.rst.

If you are unsure how to answer this question, answer N.
--
2.7.4
\
 
 \ /
  Last update: 2017-05-13 13:53    [W:0.147 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site