KEYS: validate certificate trust only with builtin keys

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 only by
builtin keys on the system keyring.

This patch defines a new option 'builtin' for the kernel parameter
'keys_ownerid' to allow trust validation using builtin keys.

Simplified Mimi's "KEYS: define an owner trusted keyring" patch

Changelog v7:
- rename builtin_keys to use_builtin_keys

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bdb193a..90c12c5 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -569,7 +569,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
        ca_keys=        [KEYS] This parameter identifies a specific key(s) on
                        the system trusted keyring to be used for certificate
                        trust validation.
-                       format: id:<keyid>
+                       format: { id:<keyid> | builtin }
 
        ccw_timeout_log [S390]
                        See Documentation/s390/CommonIO for details.

diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
index d376195..927ce75 100644 (file)
--- a/crypto/asymmetric_keys/x509_public_key.c
+++ b/crypto/asymmetric_keys/x509_public_key.c
@@ -24,6 +24,7 @@
 #include "public_key.h"
 #include "x509_parser.h"
 
+static bool use_builtin_keys;
 static char *ca_keyid;
 
 #ifndef MODULE
@@ -34,6 +35,8 @@ static int __init ca_keys_setup(char *str)
 
        if (strncmp(str, "id:", 3) == 0)
                ca_keyid = str; /* owner key 'id:xxxxxx' */
+       else if (strcmp(str, "builtin") == 0)
+               use_builtin_keys = true;
 
        return 1;
 }
@@ -180,7 +183,6 @@ EXPORT_SYMBOL_GPL(x509_check_signature);
 static int x509_validate_trust(struct x509_certificate *cert,
                               struct key *trust_keyring)
 {
-       const struct public_key *pk;
        struct key *key;
        int ret = 1;
 
@@ -195,8 +197,9 @@ static int x509_validate_trust(struct x509_certificate *cert,
                                          cert->authority,
                                          strlen(cert->authority));
        if (!IS_ERR(key))  {
-               pk = key->payload.data;
-               ret = x509_check_signature(pk, cert);
+               if (!use_builtin_keys
+                   || test_bit(KEY_FLAG_BUILTIN, &key->flags))
+                       ret = x509_check_signature(key->payload.data, cert);
                key_put(key);
        }
        return ret;

diff --git a/include/linux/key.h b/include/linux/key.h
index 017b082..65316f7 100644 (file)
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -170,6 +170,7 @@ struct key {
 #define KEY_FLAG_INVALIDATED   7       /* set if key has been invalidated */
 #define KEY_FLAG_TRUSTED       8       /* set if key is trusted */
 #define KEY_FLAG_TRUSTED_ONLY  9       /* set if keyring only accepts links to trusted keys */
+#define KEY_FLAG_BUILTIN       10      /* set if key is builtin */
 
        /* the key type and key description string
         * - the desc is used to match a key against search criteria

diff --git a/kernel/system_keyring.c b/kernel/system_keyring.c
index 52ebc70..875f64e 100644 (file)
--- a/kernel/system_keyring.c
+++ b/kernel/system_keyring.c
@@ -89,6 +89,7 @@ static __init int load_system_certificate_list(void)
                        pr_err("Problem loading in-kernel X.509 certificate (%ld)\n",
                               PTR_ERR(key));
                } else {
+                       set_bit(KEY_FLAG_BUILTIN, &key_ref_to_ptr(key)->flags);
                        pr_notice("Loaded X.509 cert '%s'\n",
                                  key_ref_to_ptr(key)->description);
                        key_ref_put(key);