diff mbox

[v10,07/11] KEYS: Parse keyring payload for restrict options

Message ID 20161129004432.17926-8-mathew.j.martineau@linux.intel.com
State New
Headers show

Commit Message

Mat Martineau Nov. 29, 2016, 12:44 a.m. UTC
Keyrings recently gained restrict_link capabilities that allow
individual keys to be validated prior to linking.  This functionality
was only available using internal kernel APIs.

Configuring keyring restrictions from userspace must work around these
constraints:

 - The restrict_link pointer must be set through keyring_alloc().
 - The add_key system call has a fixed set of parameters.

When creating keyrings, the payload was previously required to be
NULL.  To support restrict_link configuration, the payload is now
parsed for keyring options if a payload is provided.  The expected
option payload format is:

  "restrict=<key type>[:<restriction options>]"

The format of the restriction information is specified by each key
type.

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 Documentation/security/keys.txt | 13 +++++-
 security/keys/keyring.c         | 88 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 96 insertions(+), 5 deletions(-)
diff mbox

Patch

diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt
index 8163295..74d878d 100644
--- a/Documentation/security/keys.txt
+++ b/Documentation/security/keys.txt
@@ -418,8 +418,17 @@  The main syscalls are:
      the type. The payload is plen in size, and plen can be zero for an empty
      payload.
 
-     A new keyring can be generated by setting type "keyring", the keyring name
-     as the description (or NULL) and setting the payload to NULL.
+     A new keyring can be generated by setting type "keyring" and the keyring
+     name as the description (or NULL).  The payload can be NULL or contain
+     keyring link restriction parameters using the following format:
+
+	"restrict=<type>:<options>"
+
+     "type" is a registered key type. "options" vary depending on the key type,
+     and are passed to the lookup_restrict function for the requested type.
+     The options may specify a specific method and relevant data for the
+     restriction (such as signature verification or constraints on key
+     payload).
 
      User defined keys can be created by specifying type "user". It is
      recommended that a user defined key's description by prefixed with a type
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 07f680b..72d0a7e 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -23,6 +23,13 @@ 
 #include "internal.h"
 
 /*
+ * Layout of preparse payload
+ */
+enum {
+	keyring_restrict_link,
+};
+
+/*
  * When plumbing the depths of the key tree, this sets a hard limit
  * set on how deep we're willing to go.
  */
@@ -126,28 +133,103 @@  static void keyring_publish_name(struct key *keyring)
 }
 
 /*
+ * Parse the keyring options and fill in the required keyring members.
+ *
+ * Expected format is: "restrict=<key_type>[:<options>]"
+ *
+ * Returns 0 if the option string is valid (including the empty case),
+ * otherwise -EINVAL.
+ */
+static int keyring_datablob_parse(char *datablob,
+				  struct key_preparsed_payload *prep)
+{
+	char *type_name;
+	struct key_type *restrict_type = NULL;
+	struct key_restriction *restrict_link;
+	int ret = -EINVAL;
+	static const char restrict_prefix[] = "restrict=";
+
+	if (*datablob == '\0')
+		return 0;
+
+	if (!strstarts(datablob, restrict_prefix))
+		return -EINVAL;
+
+	datablob += sizeof(restrict_prefix) - 1;
+
+	type_name = strsep(&datablob, ":");
+
+	restrict_type = key_type_lookup(type_name);
+	if (IS_ERR(restrict_type))
+		return -EINVAL;
+
+	if (!restrict_type->lookup_restrict)
+		goto error;
+
+	restrict_link = restrict_type->lookup_restrict(datablob);
+	if (IS_ERR(restrict_link))
+		goto error;
+
+	prep->payload.data[keyring_restrict_link] = restrict_link;
+	ret = 0;
+
+error:
+	key_type_put(restrict_type);
+
+	return ret;
+}
+
+/*
  * Preparse a keyring payload
  */
 static int keyring_preparse(struct key_preparsed_payload *prep)
 {
-	return prep->datalen != 0 ? -EINVAL : 0;
+	char *datablob;
+	size_t datalen = prep->datalen;
+	int ret = 0;
+
+	if (datalen) {
+		datablob = kmalloc(datalen + 1, GFP_KERNEL);
+		if (!datablob)
+			return -ENOMEM;
+
+		memcpy(datablob, prep->data, datalen);
+		datablob[datalen] = '\0';
+
+		ret = keyring_datablob_parse(datablob, prep);
+
+		kfree(datablob);
+	}
+
+	return ret;
 }
 
 /*
- * Free a preparse of a user defined key payload
+ * Free a preparse of a keyring payload
  */
 static void keyring_free_preparse(struct key_preparsed_payload *prep)
 {
+	struct key_restriction *keyres;
+
+	keyres = prep->payload.data[keyring_restrict_link];
+
+	if (keyres && keyres->free_data) {
+		keyres->free_data(keyres->data);
+		kfree(keyres);
+	}
 }
 
 /*
  * Initialise a keyring.
  *
- * Returns 0 on success, -EINVAL if given any data.
+ * Returns 0 on success.
  */
 static int keyring_instantiate(struct key *keyring,
 			       struct key_preparsed_payload *prep)
 {
+	keyring->restrict_link = prep->payload.data[keyring_restrict_link];
+	prep->payload.data[keyring_restrict_link] = NULL;
+
 	assoc_array_init(&keyring->keys);
 	/* make the keyring available by name if it has one */
 	keyring_publish_name(keyring);