KEYS: Add payload preparsing opportunity prior to key instantiate or update

Give the key type the opportunity to preparse the payload prior to the
instantiation and update routines being called.  This is done with the
provision of two new key type operations:

	int (*preparse)(struct key_preparsed_payload *prep);
	void (*free_preparse)(struct key_preparsed_payload *prep);

If the first operation is present, then it is called before key creation (in
the add/update case) or before the key semaphore is taken (in the update and
instantiate cases).  The second operation is called to clean up if the first
was called.

preparse() is given the opportunity to fill in the following structure:

	struct key_preparsed_payload {
		char		*description;
		void		*type_data[2];
		void		*payload;
		const void	*data;
		size_t		datalen;
		size_t		quotalen;
	};

Before the preparser is called, the first three fields will have been cleared,
the payload pointer and size will be stored in data and datalen and the default
quota size from the key_type struct will be stored into quotalen.

The preparser may parse the payload in any way it likes and may store data in
the type_data[] and payload fields for use by the instantiate() and update()
ops.

The preparser may also propose a description for the key by attaching it as a
string to the description field.  This can be used by passing a NULL or ""
description to the add_key() system call or the key_create_or_update()
function.  This cannot work with request_key() as that required the description
to tell the upcall about the key to be created.

This, for example permits keys that store PGP public keys to generate their own
name from the user ID and public key fingerprint in the key.

The instantiate() and update() operations are then modified to look like this:

	int (*instantiate)(struct key *key, struct key_preparsed_payload *prep);
	int (*update)(struct key *key, struct key_preparsed_payload *prep);

and the new payload data is passed in *prep, whether or not it was preparsed.

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

7 files changed, 129 insertions, 63 deletions

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index 2d1bb8af7696..9e1e005c7596 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -773,8 +773,8 @@ static int encrypted_init(struct encrypted_key_payload *epayload,
  *
  * On success, return 0. Otherwise return errno.
  */
-static int encrypted_instantiate(struct key *key, const void *data,
-                                 size_t datalen)
+static int encrypted_instantiate(struct key *key,
+                                 struct key_preparsed_payload *prep)
 {
         struct encrypted_key_payload *epayload = NULL;
         char *datablob = NULL;
@@ -782,16 +782,17 @@ static int encrypted_instantiate(struct key *key, const void *data,
         char *master_desc = NULL;
         char *decrypted_datalen = NULL;
         char *hex_encoded_iv = NULL;
+        size_t datalen = prep->datalen;
         int ret;
 
-        if (datalen <= 0 || datalen > 32767 || !data)
+        if (datalen <= 0 || datalen > 32767 || !prep->data)
                 return -EINVAL;
 
         datablob = kmalloc(datalen + 1, GFP_KERNEL);
         if (!datablob)
                 return -ENOMEM;
         datablob[datalen] = 0;
-        memcpy(datablob, data, datalen);
+        memcpy(datablob, prep->data, datalen);
         ret = datablob_parse(datablob, &format, &master_desc,
                              &decrypted_datalen, &hex_encoded_iv);
         if (ret < 0)
@@ -834,16 +835,17 @@ static void encrypted_rcu_free(struct rcu_head *rcu)
  *
  * On success, return 0. Otherwise return errno.
  */
-static int encrypted_update(struct key *key, const void *data, size_t datalen)
+static int encrypted_update(struct key *key, struct key_preparsed_payload *prep)
 {
         struct encrypted_key_payload *epayload = key->payload.data;
         struct encrypted_key_payload *new_epayload;
         char *buf;
         char *new_master_desc = NULL;
         const char *format = NULL;
+        size_t datalen = prep->datalen;
         int ret = 0;
 
-        if (datalen <= 0 || datalen > 32767 || !data)
+        if (datalen <= 0 || datalen > 32767 || !prep->data)
                 return -EINVAL;
 
         buf = kmalloc(datalen + 1, GFP_KERNEL);
@@ -851,7 +853,7 @@ static int encrypted_update(struct key *key, const void *data, size_t datalen)
                 return -ENOMEM;
 
         buf[datalen] = 0;
-        memcpy(buf, data, datalen);
+        memcpy(buf, prep->data, datalen);
         ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL);
         if (ret < 0)
                 goto out;
diff --git a/security/keys/key.c b/security/keys/key.c
index 50d96d4e06f2..1d039af99f50 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -412,8 +412,7 @@ EXPORT_SYMBOL(key_payload_reserve);
  * key_construction_mutex.
  */
 static int __key_instantiate_and_link(struct key *key,
-                                      const void *data,
-                                      size_t datalen,
+                                      struct key_preparsed_payload *prep,
                                       struct key *keyring,
                                       struct key *authkey,
                                       unsigned long *_prealloc)
@@ -431,7 +430,7 @@ static int __key_instantiate_and_link(struct key *key,
         /* can't instantiate twice */
         if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
                 /* instantiate the key */
-                ret = key->type->instantiate(key, data, datalen);
+                ret = key->type->instantiate(key, prep);
 
                 if (ret == 0) {
                         /* mark the key as being instantiated */
@@ -482,22 +481,37 @@ int key_instantiate_and_link(struct key *key,
                              struct key *keyring,
                              struct key *authkey)
 {
+        struct key_preparsed_payload prep;
         unsigned long prealloc;
         int ret;
 
+        memset(&prep, 0, sizeof(prep));
+        prep.data = data;
+        prep.datalen = datalen;
+        prep.quotalen = key->type->def_datalen;
+        if (key->type->preparse) {
+                ret = key->type->preparse(&prep);
+                if (ret < 0)
+                        goto error;
+        }
+
         if (keyring) {
                 ret = __key_link_begin(keyring, key->type, key->description,
                                        &prealloc);
                 if (ret < 0)
-                        return ret;
+                        goto error_free_preparse;
         }
 
-        ret = __key_instantiate_and_link(key, data, datalen, keyring, authkey,
+        ret = __key_instantiate_and_link(key, &prep, keyring, authkey,
                                          &prealloc);
 
         if (keyring)
                 __key_link_end(keyring, key->type, prealloc);
 
+error_free_preparse:
+        if (key->type->preparse)
+                key->type->free_preparse(&prep);
+error:
         return ret;
 }
 
@@ -706,7 +720,7 @@ void key_type_put(struct key_type *ktype)
  * if we get an error.
  */
 static inline key_ref_t __key_update(key_ref_t key_ref,
-                                     const void *payload, size_t plen)
+                                     struct key_preparsed_payload *prep)
 {
         struct key *key = key_ref_to_ptr(key_ref);
         int ret;
@@ -722,7 +736,7 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
 
         down_write(&key->sem);