path: root/Documentation/security
diff options
authorAnton Arapov <>2012-06-08 12:58:00 +0200
committerAnton Arapov <>2012-06-08 12:58:00 +0200
commit6792a3f47a2e42d7164292bf7f1a55cfc4c91652 (patch)
treeb90c002bfbbeaec92f5d8a2383dcabf6524016f7 /Documentation/security
parentfe2895d3d55146cac65b273c0f83e2c7e543cd0e (diff)
fedora kernel: b920e9b748c595f970bf80ede7832d39f8d567dav3.4.1-2
Signed-off-by: Anton Arapov <>
Diffstat (limited to 'Documentation/security')
5 files changed, 83 insertions, 4 deletions
diff --git a/Documentation/security/00-INDEX b/Documentation/security/00-INDEX
index 99b85d39751..eeed1de546d 100644
--- a/Documentation/security/00-INDEX
+++ b/Documentation/security/00-INDEX
@@ -6,6 +6,8 @@ SELinux.txt
- how to get started with the SELinux security enhancement.
- documentation on the Smack Linux Security Module.
+ - documentation on the Yama Linux Security Module.
- documentation on the AppArmor security extension.
diff --git a/Documentation/security/Smack.txt b/Documentation/security/Smack.txt
index e9dab41c0fe..d2f72ae6643 100644
--- a/Documentation/security/Smack.txt
+++ b/Documentation/security/Smack.txt
@@ -536,6 +536,6 @@ writing a single character to the /smack/logging file :
3 : log denied & accepted
Events are logged as 'key=value' pairs, for each event you at least will get
-the subjet, the object, the rights requested, the action, the kernel function
+the subject, the object, the rights requested, the action, the kernel function
that triggered the event, plus other pairs depending on the type of event
diff --git a/Documentation/security/Yama.txt b/Documentation/security/Yama.txt
new file mode 100644
index 00000000000..a9511f17906
--- /dev/null
+++ b/Documentation/security/Yama.txt
@@ -0,0 +1,65 @@
+Yama is a Linux Security Module that collects a number of system-wide DAC
+security protections that are not handled by the core kernel itself. To
+select it at boot time, specify "security=yama" (though this will disable
+any other LSM).
+Yama is controlled through sysctl 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
+( and arbitrary code injection
+( 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).
+For 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 descendents) 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 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).
+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.
+The original children-only logic was based on the restrictions in grsecurity.
diff --git a/Documentation/security/keys-trusted-encrypted.txt b/Documentation/security/keys-trusted-encrypted.txt
index c9e4855ed3d..e105ae97a4f 100644
--- a/Documentation/security/keys-trusted-encrypted.txt
+++ b/Documentation/security/keys-trusted-encrypted.txt
@@ -1,7 +1,7 @@
Trusted and Encrypted Keys
Trusted and Encrypted Keys are two new key types added to the existing kernel
-key ring service. Both of these new types are variable length symmetic keys,
+key ring service. Both of these new types are variable length symmetric keys,
and in both cases all keys are created in the kernel, and user space sees,
stores, and loads only encrypted blobs. Trusted Keys require the availability
of a Trusted Platform Module (TPM) chip for greater security, while Encrypted
diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 713ec232c56..d389acd31e1 100644
--- a/Documentation/security/keys.txt
+++ b/Documentation/security/keys.txt
@@ -123,7 +123,7 @@ KEY SERVICE OVERVIEW
The key service provides a number of features besides keys:
- (*) The key service defines two special key types:
+ (*) The key service defines three special key types:
(+) "keyring"
@@ -137,6 +137,18 @@ The key service provides a number of features besides keys:
blobs of data. These can be created, updated and read by userspace,
and aren't intended for use by kernel services.
+ (+) "logon"
+ Like a "user" key, a "logon" key has a payload that is an arbitrary
+ blob of data. It is intended as a place to store secrets which are
+ accessible to the kernel but not to userspace programs.
+ The description can be arbitrary, but must be prefixed with a non-zero
+ length string that describes the key "subclass". The subclass is
+ separated from the rest of the description by a ':'. "logon" keys can
+ be created and updated from userspace, but the payload is only
+ readable from kernel space.
(*) Each process subscribes to three keyrings: a thread-specific keyring, a
process-specific keyring, and a session-specific keyring.
@@ -672,7 +684,7 @@ The keyctl syscall functions are:
If the kernel calls back to userspace to complete the instantiation of a
key, userspace should use this call mark the key as negative before the
- invoked process returns if it is unable to fulfil the request.
+ invoked process returns if it is unable to fulfill the request.
The process must have write access on the key to be able to instantiate
it, and the key must be uninstantiated.