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Commit 97d3aa0f authored by Mat Martineau's avatar Mat Martineau
Browse files

KEYS: Add a lookup_restriction function for the asymmetric key type 



Look up asymmetric keyring restriction information using the key-type
lookup_restrict hook.

Signed-off-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
parent 6563c91f

Documentation/crypto/asymmetric-keys.txt

+35 −0
Original line number Diff line number Diff line
@@ -311,3 +311,38 @@ Functions are provided to register and unregister parsers: 


Parsers may not have the same name.  The names are otherwise only used for

displaying in debugging messages.





=========================

KEYRING LINK RESTRICTIONS

=========================



Keyrings created from userspace using add_key can be configured to check the

signature of the key being linked.



Several restriction methods are available:



 (1) Restrict using the kernel builtin trusted keyring



     - Option string used with KEYCTL_RESTRICT_KEYRING:

       - "builtin_trusted"



     The kernel builtin trusted keyring will be searched for the signing

     key. The ca_keys kernel parameter also affects which keys are used for

     signature verification.



 (2) Restrict using the kernel builtin and secondary trusted keyrings



     - Option string used with KEYCTL_RESTRICT_KEYRING:

       - "builtin_and_secondary_trusted"



     The kernel builtin and secondary trusted keyrings will be searched for the

     signing key. The ca_keys kernel parameter also affects which keys are used

     for signature verification.



In all of these cases, if the signing key is found the signature of the key to

be linked will be verified using the signing key.  The requested key is added

to the keyring only if the signature is successfully verified.  -ENOKEY is

returned if the parent certificate could not be found, or -EKEYREJECTED is

returned if the signature check fails or the key is blacklisted.  Other errors

may be returned if the signature check could not be performed.

crypto/asymmetric_keys/asymmetric_type.c

+44 −8
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/module.h>

#include <linux/slab.h>

#include <linux/ctype.h>

#include <keys/system_keyring.h>

#include "asymmetric_keys.h"



MODULE_LICENSE("GPL");
@@ -451,6 +452,40 @@ static void asymmetric_key_destroy(struct key *key) 
	asymmetric_key_free_kids(kids);

}



static struct key_restriction *asymmetric_restriction_alloc(

	key_restrict_link_func_t check,

	struct key *key)

{

	struct key_restriction *keyres =

		kzalloc(sizeof(struct key_restriction), GFP_KERNEL);



	if (!keyres)

		return ERR_PTR(-ENOMEM);



	keyres->check = check;

	keyres->key = key;

	keyres->keytype = &key_type_asymmetric;



	return keyres;

}



/*

 * look up keyring restrict functions for asymmetric keys

 */

static struct key_restriction *asymmetric_lookup_restriction(

	const char *restriction)

{

	if (strcmp("builtin_trusted", restriction) == 0)

		return asymmetric_restriction_alloc(

			restrict_link_by_builtin_trusted, NULL);



	if (strcmp("builtin_and_secondary_trusted", restriction) == 0)

		return asymmetric_restriction_alloc(

			restrict_link_by_builtin_and_secondary_trusted, NULL);



	return ERR_PTR(-EINVAL);

}



struct key_type key_type_asymmetric = {

	.name			= "asymmetric",

	.preparse		= asymmetric_key_preparse,
@@ -460,6 +495,7 @@ struct key_type key_type_asymmetric = { 
	.match_free		= asymmetric_key_match_free,

	.destroy		= asymmetric_key_destroy,

	.describe		= asymmetric_key_describe,

	.lookup_restriction	= asymmetric_lookup_restriction,

};

EXPORT_SYMBOL_GPL(key_type_asymmetric);