Merge branch 'keyctl-restrict' of git://git.kernel.org/pub/scm/linux/kernel/git/martineau/linux into keys-next

To quote Mat Martineau:

"""
Keyrings recently acquired the ability to validate keys before they are
linked using kernel internal APIs. This patch set enables configuration
of restricted keyrings from userspace.

These patches apply to linux-fs/keys-misc and are also available here:

    https://git.kernel.org/cgit/linux/kernel/git/martineau/linux.git/log/?h=keyctl-restrict

v13: Detect and avoid cycles in restriction references, and change
restrictions to store a single key pointer rather than arbitrary data.

v12: Rework the KEYCTL_RESTRICT_KEYRING command to take an additional
parameter, renamed some functions based on feedback, and dropped an
unnecessary locking change (patch 1 in previous set).

v11: Configure restrictions using KEYCTL_RESTRICT_KEYRING instead of
using a keyring payload at creation time. Make the garbage collector
aware of restrictions.

v10: Fixups from maintainer feedback. Added some missing documentation.

v9: Rebased on linux-fs/keys-misc (v4.9-rc5)

v8: Add option to look for signing keys within the destination keyring.
Fix a consistency issue with keyring locking and restriction checks.

v7: Rework key restriction payload syntax. Move key-type-specific payload
parsing to the key-type. Attach more restriction information to keyrings
(restriction function, data, and data free) so future restrictions are not
limited to storing a key ID to use for key validation. Validate key before
using it to verify another key. Modify key type locking model to allow key
type lookup during keyring creation.

v6: Return error if only restrict_key is supplied, address misc. review
comments.

v5: Fixed signature bypass problem in patch 3/6

v4: Added userspace restriction options based on builtin keyrings.
restrict_link_by_signature implementation is no longer modified. Split
up v3's patch 2/5 to isolate the change to key.h.

v3: Updated commit message for patch 2/5 (restrict_link_by_signature_indirect)

v2: Payload is now preparsed
"""

Signed-off-by: David Howells <dhowells@redhat.com>

2 files changed, 252 insertions, 11 deletions

diff --git a/crypto/asymmetric_keys/asymmetric_type.c b/crypto/asymmetric_keys/asymmetric_type.c
index 6600181d..e4b0ed38 100644
--- a/crypto/asymmetric_keys/asymmetric_type.c
+++ b/crypto/asymmetric_keys/asymmetric_type.c
@@ -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");
@@ -451,15 +452,100 @@ 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)
+{
+	char *restrict_method;
+	char *parse_buf;
+	char *next;
+	struct key_restriction *ret = ERR_PTR(-EINVAL);
+
+	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);
+
+	parse_buf = kstrndup(restriction, PAGE_SIZE, GFP_KERNEL);
+	if (!parse_buf)
+		return ERR_PTR(-ENOMEM);
+
+	next = parse_buf;
+	restrict_method = strsep(&next, ":");
+
+	if ((strcmp(restrict_method, "key_or_keyring") == 0) && next) {
+		char *key_text;
+		key_serial_t serial;
+		struct key *key;
+		key_restrict_link_func_t link_fn =
+			restrict_link_by_key_or_keyring;
+		bool allow_null_key = false;
+
+		key_text = strsep(&next, ":");
+
+		if (next) {
+			if (strcmp(next, "chain") != 0)
+				goto out;
+
+			link_fn = restrict_link_by_key_or_keyring_chain;
+			allow_null_key = true;
+		}
+
+		if (kstrtos32(key_text, 0, &serial) < 0)
+			goto out;
+
+		if ((serial == 0) && allow_null_key) {
+			key = NULL;
+		} else {
+			key = key_lookup(serial);
+			if (IS_ERR(key)) {
+				ret = ERR_CAST(key);
+				goto out;
+			}
+		}
+
+		ret = asymmetric_restriction_alloc(link_fn, key);
+		if (IS_ERR(ret))
+			key_put(key);
+	}
+
+out:
+	kfree(parse_buf);
+	return ret;
+}
+
 struct key_type key_type_asymmetric = {
-	.name		= "asymmetric",
-	.preparse	= asymmetric_key_preparse,
-	.free_preparse	= asymmetric_key_free_preparse,
-	.instantiate	= generic_key_instantiate,
-	.match_preparse	= asymmetric_key_match_preparse,
-	.match_free	= asymmetric_key_match_free,
-	.destroy	= asymmetric_key_destroy,
-	.describe	= asymmetric_key_describe,
+	.name			= "asymmetric",
+	.preparse		= asymmetric_key_preparse,
+	.free_preparse		= asymmetric_key_free_preparse,
+	.instantiate		= generic_key_instantiate,
+	.match_preparse		= asymmetric_key_match_preparse,
+	.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);
 
diff --git a/crypto/asymmetric_keys/restrict.c b/crypto/asymmetric_keys/restrict.c
index 19d1afb9..86fb6850 100644
--- a/crypto/asymmetric_keys/restrict.c
+++ b/crypto/asymmetric_keys/restrict.c
@@ -56,9 +56,10 @@ __setup("ca_keys=", ca_keys_setup);
 
 /**
  * restrict_link_by_signature - Restrict additions to a ring of public keys
- * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
+ * @dest_keyring: Keyring being linked to.
  * @type: The type of key being added.
  * @payload: The payload of the new key.
+ * @trust_keyring: A ring of keys that can be used to vouch for the new cert.
  *
  * Check the new certificate against the ones in the trust keyring.  If one of
  * those is the signing key and validates the new certificate, then mark the
@@ -69,9 +70,10 @@ __setup("ca_keys=", ca_keys_setup);
  * signature check fails or the key is blacklisted and some other error if
  * there is a matching certificate but the signature check cannot be performed.
  */
-int restrict_link_by_signature(struct key *trust_keyring,
+int restrict_link_by_signature(struct key *dest_keyring,
 			       const struct key_type *type,
-			       const union key_payload *payload)
+			       const union key_payload *payload,
+			       struct key *trust_keyring)
 {
 	const struct public_key_signature *sig;
 	struct key *key;
@@ -106,3 +108,156 @@ int restrict_link_by_signature(struct key *trust_keyring,
 	key_put(key);
 	return ret;
 }
+
+static bool match_either_id(const struct asymmetric_key_ids *pair,
+			    const struct asymmetric_key_id *single)
+{
+	return (asymmetric_key_id_same(pair->id[0], single) ||
+		asymmetric_key_id_same(pair->id[1], single));
+}
+
+static int key_or_keyring_common(struct key *dest_keyring,
+				 const struct key_type *type,
+				 const union key_payload *payload,
+				 struct key *trusted, bool check_dest)
+{
+	const struct public_key_signature *sig;
+	struct key *key = NULL;
+	int ret;
+
+	pr_devel("==>%s()\n", __func__);
+
+	if (!dest_keyring)
+		return -ENOKEY;
+	else if (dest_keyring->type != &key_type_keyring)
+		return -EOPNOTSUPP;
+
+	if (!trusted && !check_dest)
+		return -ENOKEY;
+
+	if (type != &key_type_asymmetric)
+		return -EOPNOTSUPP;
+
+	sig = payload->data[asym_auth];
+	if (!sig->auth_ids[0] && !sig->auth_ids[1])
+		return -ENOKEY;
+
+	if (trusted) {
+		if (trusted->type == &key_type_keyring) {
+			/* See if we have a key that signed this one. */
+			key = find_asymmetric_key(trusted, sig->auth_ids[0],
+						  sig->auth_ids[1], false);
+			if (IS_ERR(key))
+				key = NULL;
+		} else if (trusted->type == &key_type_asymmetric) {
+			const struct asymmetric_key_ids *signer_ids;
+
+			signer_ids = asymmetric_key_ids(trusted);
+
+			/*
+			 * The auth_ids come from the candidate key (the
+			 * one that is being considered for addition to
+			 * dest_keyring) and identify the key that was
+			 * used to sign.
+			 *
+			 * The signer_ids are identifiers for the
+			 * signing key specified for dest_keyring.
+			 *
+			 * The first auth_id is the preferred id, and
+			 * the second is the fallback. If only one
+			 * auth_id is present, it may match against
+			 * either signer_id. If two auth_ids are
+			 * present, the first auth_id must match one
+			 * signer_id and the second auth_id must match
+			 * the second signer_id.
+			 */
+			if (!sig->auth_ids[0] || !sig->auth_ids[1]) {
+				const struct asymmetric_key_id *auth_id;
+
+				auth_id = sig->auth_ids[0] ?: sig->auth_ids[1];
+				if (match_either_id(signer_ids, auth_id))
+					key = __key_get(trusted);
+
+			} else if (asymmetric_key_id_same(signer_ids->id[1],
+							  sig->auth_ids[1]) &&
+				   match_either_id(signer_ids,
+						   sig->auth_ids[0])) {
+				key = __key_get(trusted);
+			}
+		} else {
+			return -EOPNOTSUPP;
+		}
+	}
+
+	if (check_dest && !key) {
+		/* See if the destination has a key that signed this one. */
+		key = find_asymmetric_key(dest_keyring, sig->auth_ids[0],
+					  sig->auth_ids[1], false);
+		if (IS_ERR(key))
+			key = NULL;
+	}
+
+	if (!key)
+		return -ENOKEY;
+
+	ret = key_validate(key);
+	if (ret == 0)
+		ret = verify_signature(key, sig);
+
+	key_put(key);
+	return ret;
+}
+
+/**
+ * restrict_link_by_key_or_keyring - Restrict additions to a ring of public
+ * keys using the restrict_key information stored in the ring.
+ * @dest_keyring: Keyring being linked to.
+ * @type: The type of key being added.
+ * @payload: The payload of the new key.
+ * @trusted: A key or ring of keys that can be used to vouch for the new cert.
+ *
+ * Check the new certificate only against the key or keys passed in the data
+ * parameter. If one of those is the signing key and validates the new
+ * certificate, then mark the new certificate as being ok to link.
+ *
+ * Returns 0 if the new certificate was accepted, -ENOKEY if we
+ * couldn't find a matching parent certificate in the trusted list,
+ * -EKEYREJECTED if the signature check fails, and some other error if
+ * there is a matching certificate but the signature check cannot be
+ * performed.
+ */
+int restrict_link_by_key_or_keyring(struct key *dest_keyring,
+				    const struct key_type *type,
+				    const union key_payload *payload,
+				    struct key *trusted)
+{
+	return key_or_keyring_common(dest_keyring, type, payload, trusted,
+				     false);
+}
+
+/**
+ * restrict_link_by_key_or_keyring_chain - Restrict additions to a ring of
+ * public keys using the restrict_key information stored in the ring.
+ * @dest_keyring: Keyring being linked to.
+ * @type: The type of key being added.
+ * @payload: The payload of the new key.
+ * @trusted: A key or ring of keys that can be used to vouch for the new cert.
+ *
+ * Check the new certificate only against the key or keys passed in the data
+ * parameter. If one of those is the signing key and validates the new
+ * certificate, then mark the new certificate as being ok to link.
+ *
+ * Returns 0 if the new certificate was accepted, -ENOKEY if we
+ * couldn't find a matching parent certificate in the trusted list,
+ * -EKEYREJECTED if the signature check fails, and some other error if
+ * there is a matching certificate but the signature check cannot be
+ * performed.
+ */
+int restrict_link_by_key_or_keyring_chain(struct key *dest_keyring,
+					  const struct key_type *type,
+					  const union key_payload *payload,
+					  struct key *trusted)
+{
+	return key_or_keyring_common(dest_keyring, type, payload, trusted,
+				     true);
+}