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>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 82 insertions, 32 deletions

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);
 
-        ret = key->type->update(key, payload, plen);
+        ret = key->type->update(key, prep);
         if (ret == 0)
                 /* updating a negative key instantiates it */
                 clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
@@ -774,6 +788,7 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
                                unsigned long flags)
 {
         unsigned long prealloc;
+        struct key_preparsed_payload prep;
         const struct cred *cred = current_cred();
         struct key_type *ktype;
         struct key *keyring, *key = NULL;
@@ -789,8 +804,9 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
         }
 
         key_ref = ERR_PTR(-EINVAL);
-        if (!ktype->match || !ktype->instantiate)
-                goto error_2;
+        if (!ktype->match || !ktype->instantiate ||
+            (!description && !ktype->preparse))
+                goto error_put_type;
 
         keyring = key_ref_to_ptr(keyring_ref);
 
@@ -798,18 +814,37 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
 
         key_ref = ERR_PTR(-ENOTDIR);
         if (keyring->type != &key_type_keyring)
-                goto error_2;
+                goto error_put_type;
+
+        memset(&prep, 0, sizeof(prep));
+        prep.data = payload;
+        prep.datalen = plen;
+        prep.quotalen = ktype->def_datalen;
+        if (ktype->preparse) {
+                ret = ktype->preparse(&prep);
+                if (ret < 0) {
+                        key_ref = ERR_PTR(ret);
+                        goto error_put_type;
+                }
+                if (!description)
+                        description = prep.description;
+                key_ref = ERR_PTR(-EINVAL);
+                if (!description)
+                        goto error_free_prep;
+        }
 
         ret = __key_link_begin(keyring, ktype, description, &prealloc);
-        if (ret < 0)
-                goto error_2;
+        if (ret < 0) {
+                key_ref = ERR_PTR(ret);
+                goto error_free_prep;
+        }
 
         /* if we're going to allocate a new key, we're going to have
          * to modify the keyring */
         ret = key_permission(keyring_ref, KEY_WRITE);
         if (ret < 0) {
                 key_ref = ERR_PTR(ret);
-                goto error_3;
+                goto error_link_end;
         }
 
         /* if it's possible to update this type of key, search for an existing
@@ -840,25 +875,27 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
                         perm, flags);
         if (IS_ERR(key)) {
                 key_ref = ERR_CAST(key);
-                goto error_3;
+                goto error_link_end;
         }
 
         /* instantiate it and link it into the target keyring */
-        ret = __key_instantiate_and_link(key, payload, plen, keyring, NULL,
-                                         &prealloc);
+        ret = __key_instantiate_and_link(key, &prep, keyring, NULL, &prealloc);
         if (ret < 0) {
                 key_put(key);
                 key_ref = ERR_PTR(ret);
-                goto error_3;
+                goto error_link_end;
         }
 
         key_ref = make_key_ref(key, is_key_possessed(keyring_ref));
 
- error_3:
+error_link_end:
         __key_link_end(keyring, ktype, prealloc);
- error_2:
+error_free_prep:
+        if (ktype->preparse)
+                ktype->free_preparse(&prep);
+error_put_type:
         key_type_put(ktype);
- error:
+error:
         return key_ref;
 
  found_matching_key:
@@ -866,10 +903,9 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
          * - we can drop the locks first as we have the key pinned
          */
         __key_link_end(keyring, ktype, prealloc);
-        key_type_put(ktype);
 
-        key_ref = __key_update(key_ref, payload, plen);
-        goto error;
+        key_ref = __key_update(key_ref, &prep);
+        goto error_free_prep;
 }
 EXPORT_SYMBOL(key_create_or_update);
 
@@ -888,6 +924,7 @@ EXPORT_SYMBOL(key_create_or_update);
  */
 int 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;
 
@@ -900,18 +937,31 @@ int key_update(key_ref_t key_ref, const void *payload, size_t plen)
 
         /* attempt to update it if supported */
         ret = -EOPNOTSUPP;
-        if (key->type->update) {
-                down_write(&key->sem);
-
-                ret = key->type->update(key, payload, plen);
-                if (ret == 0)
-                        /* updating a negative key instantiates it */
-                        clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
+        if (!key->type->update)
+                goto error;
 
-                up_write(&key->sem);
+        memset(&prep, 0, sizeof(prep));
+        prep.data = payload;
+        prep.datalen = plen;
+        prep.quotalen = key->type->def_datalen;
+        if (key->type->preparse) {
+                ret = key->type->preparse(&prep);
+                if (ret < 0)
+                        goto error;
         }
 
- error:
+        down_write(&key->sem);
+
+        ret = key->type->update(key, &prep);
+        if (ret == 0)
+                /* updating a negative key instantiates it */
+                clear_bit(KEY_FLAG_NEGATIVE, &key->flags);
+
+        up_write(&key->sem);
+
+        if (key->type->preparse)
+                key->type->free_preparse(&prep);
+error:
         return ret;
 }
 EXPORT_SYMBOL(key_update);