Adjusts for ReST markup and moves under LSM admin guide.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
--- /dev/null
+====
+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
+============
+
+As Linux grows in popularity, it will become a larger target for
+malware. One particularly troubling weakness of the Linux process
+interfaces is that a single user is able to examine the memory and
+running state of any of their processes. For example, if one application
+(e.g. Pidgin) was compromised, it would be possible for an attacker to
+attach to other running processes (e.g. Firefox, SSH sessions, GPG agent,
+etc) to extract additional credentials and continue to expand the scope
+of their attack without resorting to user-assisted phishing.
+
+This is not a theoretical problem. SSH session hijacking
+(http://www.storm.net.nz/projects/7) and arbitrary code injection
+(http://c-skills.blogspot.com/2007/05/injectso.html) attacks already
+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
+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"
+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``
+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, ...)``
+so that any otherwise allowed process (even those in external pid namespaces)
+may attach.
+
+The sysctl settings (writable only with ``CAP_SYS_PTRACE``) are:
+
+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
+ unchanged.
+
+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.
+
+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.
+
+The original children-only logic was based on the restrictions in grsecurity.
apparmor
SELinux
tomoyo
+ Yama
- 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
+++ /dev/null
-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
-
-==============================================================
-
-ptrace_scope:
-
-As Linux grows in popularity, it will become a larger target for
-malware. One particularly troubling weakness of the Linux process
-interfaces is that a single user is able to examine the memory and
-running state of any of their processes. For example, if one application
-(e.g. Pidgin) was compromised, it would be possible for an attacker to
-attach to other running processes (e.g. Firefox, SSH sessions, GPG agent,
-etc) to extract additional credentials and continue to expand the scope
-of their attack without resorting to user-assisted phishing.
-
-This is not a theoretical problem. SSH session hijacking
-(http://www.storm.net.nz/projects/7) and arbitrary code injection
-(http://c-skills.blogspot.com/2007/05/injectso.html) attacks already
-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
-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"
-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
-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, ...)
-so that any otherwise allowed process (even those in external pid namespaces)
-may attach.
-
-The sysctl settings (writable only with CAP_SYS_PTRACE) are:
-
-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
- unchanged.
-
-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.
-
-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.
-
-The original children-only logic was based on the restrictions in grsecurity.
-
-==============================================================
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>
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.
projects / mirror_ubuntu-artful-kernel.git / commitdiff