[PATCH v4 03/12] KEYS: CA link restriction

Eric Snowberg
2021-08-19T00:22:10Z

Add a new link restriction. Restrict the addition of keys in a keyring
based on the key to be added being a CA (self-signed).

Signed-off-by: Eric Snowberg <eric.snowberg@oracle.com>
---
v1: Initial version
v2: Removed secondary keyring references
v3: Removed restrict_link_by_system_trusted_or_ca
Simplify restrict_link_by_ca - only see if the key is a CA
Did not add __init in front of restrict_link_by_ca in case
restriction could be resued in the future
v4: Unmodified from v3
---
crypto/asymmetric_keys/restrict.c | 40 +++++++++++++++++++++++++++++++
include/crypto/public_key.h | 5 ++++
2 files changed, 45 insertions(+)

diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c
index 84cefe3b3585..9ae43d3f862b 100644
--- a/crypto/asymmetric_keys/restrict.c
+++ b/crypto/asymmetric_keys/restrict.c
@@ -108,6 +108,46 @@ 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.
+ * @trusted: Unused.
+ *
+ * Check if the new certificate is a CA. If it is a CA, then mark the new
+ * certificate as being ok to link.
+ *
+ * Returns 0 if the new certificate was accepted, -ENOKEY if we could not find
+ * a matching parent certificate in the trusted list. -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)
+{
+ 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;
+
+ return public_key_verify_signature(pkey, sig);
+}
+
static bool match_either_id(const struct asymmetric_key_ids *pair,
const struct asymmetric_key_id *single)
{
diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
index 47accec68cb0..545af1ea57de 100644
--- a/include/crypto/public_key.h
+++ b/include/crypto/public_key.h
@@ -71,6 +71,11 @@ extern int restrict_link_by_key_or_keyring_chain(struct key *trust_keyring,
const union key_payload *payload,
struct key *trusted);

+extern int restrict_link_by_ca(struct key *dest_keyring,
+ const struct key_type *type,
+ const union key_payload *payload,
+ struct key *trust_keyring);
+
extern int query_asymmetric_key(const struct kernel_pkey_params *,
struct kernel_pkey_query *);

--
2.18.4