keys: update the documentation with info about "logon" keys

Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>

diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 787717091421d54ec330f51bdaed0f2520749da8..d389acd31e19405410ca87acbe689739e0d35771 100644 (file)
--- 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.