Merge to Fedora kernel-2.6.18-1.2224_FC5 patched with stable patch-2.6.18.1-vs2.0...

[linux-2.6.git] / Documentation / keys-request-key.txt

diff --git a/Documentation/keys-request-key.txt b/Documentation/keys-request-key.txt
index 22488d7..c1f64fd 100644 (file)
--- a/Documentation/keys-request-key.txt
+++ b/Documentation/keys-request-key.txt
@@ -3,16 +3,23 @@
                              ===================
 
 The key request service is part of the key retention service (refer to
                              ===================
 
 The key request service is part of the key retention service (refer to

-Documentation/keys.txt). This document explains more fully how that the
-requesting algorithm works.
+Documentation/keys.txt).  This document explains more fully how the requesting
+algorithm works.

 
 The process starts by either the kernel requesting a service by calling
 
 The process starts by either the kernel requesting a service by calling

-request_key():
+request_key*():

 
        struct key *request_key(const struct key_type *type,
                                const char *description,
                                const char *callout_string);
 
 
        struct key *request_key(const struct key_type *type,
                                const char *description,
                                const char *callout_string);
 

+or:
+
+       struct key *request_key_with_auxdata(const struct key_type *type,
+                                            const char *description,
+                                            const char *callout_string,
+                                            void *aux);
+

 Or by userspace invoking the request_key system call:
 
        key_serial_t request_key(const char *type,
 Or by userspace invoking the request_key system call:
 
        key_serial_t request_key(const char *type,


@@ -20,16 +27,26 @@ Or by userspace invoking the request_key system call:
                                 const char *callout_info,
                                 key_serial_t dest_keyring);
 
                                 const char *callout_info,
                                 key_serial_t dest_keyring);
 

-The main difference between the two access points is that the in-kernel
-interface does not need to link the key to a keyring to prevent it from being
-immediately destroyed. The kernel interface returns a pointer directly to the
-key, and it's up to the caller to destroy the key.
+The main difference between the access points is that the in-kernel interface
+does not need to link the key to a keyring to prevent it from being immediately
+destroyed.  The kernel interface returns a pointer directly to the key, and
+it's up to the caller to destroy the key.
+
+The request_key_with_auxdata() call is like the in-kernel request_key() call,
+except that it permits auxiliary data to be passed to the upcaller (the default
+is NULL).  This is only useful for those key types that define their own upcall
+mechanism rather than using /sbin/request-key.

 
 The userspace interface links the key to a keyring associated with the process
 to prevent the key from going away, and returns the serial number of the key to
 the caller.
 
 
 
 The userspace interface links the key to a keyring associated with the process
 to prevent the key from going away, and returns the serial number of the key to
 the caller.
 
 

+The following example assumes that the key types involved don't define their
+own upcall mechanisms.  If they do, then those should be substituted for the
+forking and execution of /sbin/request-key.
+
+

 ===========
 THE PROCESS
 ===========
 ===========
 THE PROCESS
 ===========


@@ -40,8 +57,8 @@ A request proceeds in the following manner:
      interface].
 
  (2) request_key() searches the process's subscribed keyrings to see if there's
      interface].
 
  (2) request_key() searches the process's subscribed keyrings to see if there's

-     a suitable key there. If there is, it returns the key. If there isn't, and
-     callout_info is not set, an error is returned. Otherwise the process
+     a suitable key there.  If there is, it returns the key.  If there isn't,
+     and callout_info is not set, an error is returned.  Otherwise the process

      proceeds to the next step.
 
  (3) request_key() sees that A doesn't have the desired key yet, so it creates
      proceeds to the next step.
 
  (3) request_key() sees that A doesn't have the desired key yet, so it creates


@@ -62,7 +79,7 @@ A request proceeds in the following manner:
      instantiation.
 
  (7) The program may want to access another key from A's context (say a
      instantiation.
 
  (7) The program may want to access another key from A's context (say a

-     Kerberos TGT key). It just requests the appropriate key, and the keyring
+     Kerberos TGT key).  It just requests the appropriate key, and the keyring

      search notes that the session keyring has auth key V in its bottom level.
 
      This will permit it to then search the keyrings of process A with the
      search notes that the session keyring has auth key V in its bottom level.
 
      This will permit it to then search the keyrings of process A with the


@@ -79,10 +96,11 @@ A request proceeds in the following manner:
 (10) The program then exits 0 and request_key() deletes key V and returns key
      U to the caller.
 
 (10) The program then exits 0 and request_key() deletes key V and returns key
      U to the caller.
 

-This also extends further. If key W (step 7 above) didn't exist, key W would be
-created uninstantiated, another auth key (X) would be created (as per step 3)
-and another copy of /sbin/request-key spawned (as per step 4); but the context
-specified by auth key X will still be process A, as it was in auth key V.
+This also extends further.  If key W (step 7 above) didn't exist, key W would
+be created uninstantiated, another auth key (X) would be created (as per step
+3) and another copy of /sbin/request-key spawned (as per step 4); but the
+context specified by auth key X will still be process A, as it was in auth key
+V.

 
 This is because process A's keyrings can't simply be attached to
 /sbin/request-key at the appropriate places because (a) execve will discard two
 
 This is because process A's keyrings can't simply be attached to
 /sbin/request-key at the appropriate places because (a) execve will discard two


@@ -118,17 +136,17 @@ A search of any particular keyring proceeds in the following fashion:
 
  (2) It considers all the non-keyring keys within that keyring and, if any key
      matches the criteria specified, calls key_permission(SEARCH) on it to see
 
  (2) It considers all the non-keyring keys within that keyring and, if any key
      matches the criteria specified, calls key_permission(SEARCH) on it to see

-     if the key is allowed to be found. If it is, that key is returned; if
+     if the key is allowed to be found.  If it is, that key is returned; if

      not, the search continues, and the error code is retained if of higher
      priority than the one currently set.
 
  (3) It then considers all the keyring-type keys in the keyring it's currently
      not, the search continues, and the error code is retained if of higher
      priority than the one currently set.
 
  (3) It then considers all the keyring-type keys in the keyring it's currently

-     searching. It calls key_permission(SEARCH) on each keyring, and if this
+     searching.  It calls key_permission(SEARCH) on each keyring, and if this

      grants permission, it recurses, executing steps (2) and (3) on that
      keyring.
 
 The process stops immediately a valid key is found with permission granted to
      grants permission, it recurses, executing steps (2) and (3) on that
      keyring.
 
 The process stops immediately a valid key is found with permission granted to

-use it. Any error from a previous match attempt is discarded and the key is
+use it.  Any error from a previous match attempt is discarded and the key is

 returned.
 
 When search_process_keyrings() is invoked, it performs the following searches
 returned.
 
 When search_process_keyrings() is invoked, it performs the following searches


@@ -153,7 +171,7 @@ The moment one succeeds, all pending errors are discarded and the found key is
 returned.
 
 Only if all these fail does the whole thing fail with the highest priority
 returned.
 
 Only if all these fail does the whole thing fail with the highest priority

-error. Note that several errors may have come from LSM.
+error.  Note that several errors may have come from LSM.

 
 The error priority is:
 
 
 The error priority is: