[PATCH v2 2/3] KEYS: validate certificate trust only with selected owner key

From: Dmitry Kasatkin
Date: Tue Jun 17 2014 - 04:58:38 EST


Instead of allowing public keys, with certificates signed by any
key on the system trusted keyring, to be added to a trusted keyring,
this patch further restricts the certificates to those signed by a
particular key on the system keyring.

This patch defines a new kernel parameter 'keys_ownerid' to identify
the owner's key which must be used for trust validation of certificates.

Based on Mimi's "KEYS: define an owner trusted keyring" patch.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@xxxxxxxxxxx>
---
Documentation/kernel-parameters.txt | 5 +++++
crypto/asymmetric_keys/x509_public_key.c | 17 +++++++++++++++++
2 files changed, 22 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7116fda..7a810d3 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1434,6 +1434,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
use the HighMem zone if it exists, and the Normal
zone if it does not.

+ keys_ownerid=[KEYS] This parameter identifies a specific key(s) on
+ the system trusted keyring to be used for certificate
+ trust validation.
+ format: id:<keyid>
+
kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
Format: <Controller#>[,poll interval]
The controller # is the number of the ehci usb debug
diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index 7a9b386..8482d23 100644
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -24,6 +24,19 @@
#include "public_key.h"
#include "x509_parser.h"

+static char *owner_keyid;
+static int __init default_owner_keyid_set(char *str)
+{
+ if (!str) /* default system keyring */
+ return 1;
+
+ if (strncmp(str, "id:", 3) == 0)
+ owner_keyid = str; /* owner local key 'id:xxxxxx' */
+
+ return 1;
+}
+__setup("keys_ownerid=", default_owner_keyid_set);
+
/*
* Find a key in the given keyring by issuer and authority.
*/
@@ -169,6 +182,10 @@ static int x509_validate_trust(struct x509_certificate *cert,
if (!trust_keyring)
return -EOPNOTSUPP;

+ if (owner_keyid &&
+ !asymmetric_keyid_match(cert->authority, owner_keyid))
+ return -EPERM;
+
key = x509_request_asymmetric_key(trust_keyring,
cert->issuer, strlen(cert->issuer),
cert->authority,
--
1.9.1

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