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authorKees Cook <keescook@chromium.org>2017-05-13 04:51:52 -0700
committerJonathan Corbet <corbet@lwn.net>2017-05-18 10:33:51 -0600
commit3db38ed76890565772fcca3279cc8d454ea6176b (patch)
treedc90106e2ea46900f53f8cb523415a1ff126f235 /Documentation/security
parent09f5412cc5b0969d428a0acd4ec5673cf5811c58 (diff)
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doc: ReSTify keys-request-key.txt
Adjusts for ReST markup and moves under keys security devel index. Cc: David Howells <dhowells@redhat.com> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/security')
-rw-r--r--Documentation/security/00-INDEX2
-rw-r--r--Documentation/security/keys/index.rst1
-rw-r--r--Documentation/security/keys/request-key.rst (renamed from Documentation/security/keys-request-key.txt)69
3 files changed, 34 insertions, 38 deletions
diff --git a/Documentation/security/00-INDEX b/Documentation/security/00-INDEX
index 08a6e7a195ef..c8dbbc227326 100644
--- a/Documentation/security/00-INDEX
+++ b/Documentation/security/00-INDEX
@@ -1,6 +1,4 @@
00-INDEX
- this file.
-keys-request-key.txt
- - description of the kernel key request service.
keys-trusted-encrypted.txt
- info on the Trusted and Encrypted keys in the kernel key ring service.
diff --git a/Documentation/security/keys/index.rst b/Documentation/security/keys/index.rst
index d34f663354bb..d7ddbc1c2502 100644
--- a/Documentation/security/keys/index.rst
+++ b/Documentation/security/keys/index.rst
@@ -7,3 +7,4 @@ Kernel Keys
core
ecryptfs
+ request-key
diff --git a/Documentation/security/keys-request-key.txt b/Documentation/security/keys/request-key.rst
index 51987bfecfed..5cdcee28479e 100644
--- a/Documentation/security/keys-request-key.txt
+++ b/Documentation/security/keys/request-key.rst
@@ -1,19 +1,19 @@
- ===================
- KEY REQUEST SERVICE
- ===================
+===================
+Key Request Service
+===================
The key request service is part of the key retention service (refer to
Documentation/security/keys.txt). This document explains more fully how
the requesting algorithm works.
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_info);
-or:
+or::
struct key *request_key_with_auxdata(const struct key_type *type,
const char *description,
@@ -21,14 +21,14 @@ or:
size_t callout_len,
void *aux);
-or:
+or::
struct key *request_key_async(const struct key_type *type,
const char *description,
const char *callout_info,
size_t callout_len);
-or:
+or::
struct key *request_key_async_with_auxdata(const struct key_type *type,
const char *description,
@@ -36,7 +36,7 @@ or:
size_t callout_len,
void *aux);
-Or by userspace invoking the request_key system call:
+Or by userspace invoking the request_key system call::
key_serial_t request_key(const char *type,
const char *description,
@@ -67,38 +67,37 @@ own upcall mechanisms. If they do, then those should be substituted for the
forking and execution of /sbin/request-key.
-===========
-THE PROCESS
+The Process
===========
A request proceeds in the following manner:
- (1) Process A calls request_key() [the userspace syscall calls the kernel
+ 1) Process A calls request_key() [the userspace syscall calls the kernel
interface].
- (2) request_key() searches the process's subscribed keyrings to see if there's
+ 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
proceeds to the next step.
- (3) request_key() sees that A doesn't have the desired key yet, so it creates
+ 3) request_key() sees that A doesn't have the desired key yet, so it creates
two things:
- (a) An uninstantiated key U of requested type and description.
+ a) An uninstantiated key U of requested type and description.
- (b) An authorisation key V that refers to key U and notes that process A
+ b) An authorisation key V that refers to key U and notes that process A
is the context in which key U should be instantiated and secured, and
from which associated key requests may be satisfied.
- (4) request_key() then forks and executes /sbin/request-key with a new session
+ 4) request_key() then forks and executes /sbin/request-key with a new session
keyring that contains a link to auth key V.
- (5) /sbin/request-key assumes the authority associated with key U.
+ 5) /sbin/request-key assumes the authority associated with key U.
- (6) /sbin/request-key execs an appropriate program to perform the actual
+ 6) /sbin/request-key execs an appropriate program to perform the actual
instantiation.
- (7) The program may want to access another key from A's context (say a
+ 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
search notes that the session keyring has auth key V in its bottom level.
@@ -110,10 +109,10 @@ A request proceeds in the following manner:
instantiate key U, using key W as a reference (perhaps it contacts a
Kerberos server using the TGT) and then instantiates key U.
- (9) Upon instantiating key U, auth key V is automatically revoked so that it
+ 9) Upon instantiating key U, auth key V is automatically revoked so that it
may not be used again.
-(10) The program then exits 0 and request_key() deletes key V and returns key
+ 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
@@ -127,8 +126,7 @@ This is because process A's keyrings can't simply be attached to
of them, and (b) it requires the same UID/GID/Groups all the way through.
-====================================
-NEGATIVE INSTANTIATION AND REJECTION
+Negative Instantiation And Rejection
====================================
Rather than instantiating a key, it is possible for the possessor of an
@@ -145,23 +143,22 @@ signal, the key under construction will be automatically negatively
instantiated for a short amount of time.
-====================
-THE SEARCH ALGORITHM
+The Search Algorithm
====================
A search of any particular keyring proceeds in the following fashion:
- (1) When the key management code searches for a key (keyring_search_aux) it
+ 1) When the key management code searches for a key (keyring_search_aux) it
firstly calls key_permission(SEARCH) on the keyring it's starting with,
if this denies permission, it doesn't search further.
- (2) It considers all the non-keyring keys within that keyring and, if any key
+ 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
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
+ 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
grants permission, it recurses, executing steps (2) and (3) on that
keyring.
@@ -173,20 +170,20 @@ returned.
When search_process_keyrings() is invoked, it performs the following searches
until one succeeds:
- (1) If extant, the process's thread keyring is searched.
+ 1) If extant, the process's thread keyring is searched.
- (2) If extant, the process's process keyring is searched.
+ 2) If extant, the process's process keyring is searched.
- (3) The process's session keyring is searched.
+ 3) The process's session keyring is searched.
- (4) If the process has assumed the authority associated with a request_key()
+ 4) If the process has assumed the authority associated with a request_key()
authorisation key then:
- (a) If extant, the calling process's thread keyring is searched.
+ a) If extant, the calling process's thread keyring is searched.
- (b) If extant, the calling process's process keyring is searched.
+ b) If extant, the calling process's process keyring is searched.
- (c) The calling process's session keyring is searched.
+ c) The calling process's session keyring is searched.
The moment one succeeds, all pending errors are discarded and the found key is
returned.
@@ -194,7 +191,7 @@ 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.
-The error priority is:
+The error priority is::
EKEYREVOKED > EKEYEXPIRED > ENOKEY