On 3/1/22 12:36, Eric Snowberg wrote:
Add a new link restriction. Restrict the addition of keys in a keyring
based on the key to be added being a CA.
Signed-off-by: Eric Snowberg <eric.snowberg@xxxxxxxxxx>
---
crypto/asymmetric_keys/restrict.c | 43 +++++++++++++++++++++++++++++++
include/crypto/public_key.h | 15 +++++++++++
2 files changed, 58 insertions(+)
diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c
index 6b1ac5f5896a..49bb2ea7f609 100644
--- a/crypto/asymmetric_keys/restrict.c
+++ b/crypto/asymmetric_keys/restrict.c
@@ -108,6 +108,49 @@ int restrict_link_by_signature(struct key *dest_keyring,
return ret;
}
+/**
+ * restrict_link_by_ca - Restrict additions to a ring of CA keys
+ * @dest_keyring: Keyring being linked to.
+ * @type: The type of key being added.
+ * @payload: The payload of the new key.
+ * @trust_keyring: Unused.
+ *
+ * Check if the new certificate is a CA. If it is a CA, then mark the new
+ * certificate as being ok to link.
CA = root CA here, right?
+ *
+ * Returns 0 if the new certificate was accepted, -ENOKEY if the
+ * certificate is not a CA. -ENOPKG if the signature uses unsupported
+ * crypto, or some other error if there is a matching certificate but
+ * the signature check cannot be performed.
+ */
+int restrict_link_by_ca(struct key *dest_keyring,
+ const struct key_type *type,
+ const union key_payload *payload,
+ struct key *trust_keyring)
This function needs to correspond to the key_restrict_link_func_t and
therefore has 4 parameter. Call the unused 'trust_keyring' 'unused' instead?
+{
+ const struct public_key_signature *sig;
+ const struct public_key *pkey;
+
+ if (type != &key_type_asymmetric)
+ return -EOPNOTSUPP;
+
+ sig = payload->data[asym_auth];
+ if (!sig)
+ return -ENOPKG;
+
+ if (!sig->auth_ids[0] && !sig->auth_ids[1])
+ return -ENOKEY;
+
+ pkey = payload->data[asym_crypto];
+ if (!pkey)
+ return -ENOPKG;
+
+ if (!pkey->key_is_ca)
+ return -ENOKEY;
+
+ return public_key_verify_signature(pkey, sig);
+}
+
Comparing this to 'restrict_link_by_signature'... looks good.
static bool match_either_id(const struct asymmetric_key_id **pair,
const struct asymmetric_key_id *single)
{
diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
index 0521241764b7..5eadb182a400 100644
--- a/include/crypto/public_key.h
+++ b/include/crypto/public_key.h
@@ -72,6 +72,21 @@ extern int restrict_link_by_key_or_keyring_chain(struct key *trust_keyring,
const union key_payload *payload,
struct key *trusted);
+#if IS_REACHABLE(CONFIG_ASYMMETRIC_KEY_TYPE)
+extern int restrict_link_by_ca(struct key *dest_keyring,
+ const struct key_type *type,
+ const union key_payload *payload,
+ struct key *trust_keyring);
+#else
+static inline int restrict_link_by_ca(struct key *dest_keyring,
+ const struct key_type *type,
+ const union key_payload *payload,
+ struct key *trust_keyring)
+{
+ return 0;
+}
+#endif
+
extern int query_asymmetric_key(const struct kernel_pkey_params *,
struct kernel_pkey_query *);
