Re: [PATCH v4 2/3] KEYS: Add new function key_create()

, Jarkko Sakkinen
2023-01-04T12:34:30Z

On Wed, Dec 21, 2022 at 02:08:23AM +0000, Thomas Weißschuh wrote:
> key_create() works like key_create_or_update() but does not allow
> updating an existing key, instead returning ERR_PTR(-EEXIST).
>
> key_create() will be used by the blacklist keyring which should not
> create duplicate entries or update existing entries.
> Instead a dedicated message with appropriate severity will be logged.
>
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
> include/linux/key.h | 8 +++
> security/keys/key.c | 149 +++++++++++++++++++++++++++++++++++++++-------------
> 2 files changed, 120 insertions(+), 37 deletions(-)
>
> diff --git a/include/linux/key.h b/include/linux/key.h
> index d27477faf00d..8dc7f7c3088b 100644
> --- a/include/linux/key.h
> +++ b/include/linux/key.h
> @@ -386,6 +386,14 @@ extern int wait_for_key_construction(struct key *key, bool intr);
>
> extern int key_validate(const struct key *key);
>
> +extern key_ref_t key_create(key_ref_t keyring,
> + const char *type,
> + const char *description,
> + const void *payload,
> + size_t plen,
> + key_perm_t perm,
> + unsigned long flags);
> +
> extern key_ref_t key_create_or_update(key_ref_t keyring,
> const char *type,
> const char *description,
> diff --git a/security/keys/key.c b/security/keys/key.c
> index c45afdd1dfbb..f84bcd8457f4 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -788,38 +788,18 @@ static inline key_ref_t __key_update(key_ref_t key_ref,
> goto out;
> }
>
> -/**
> - * key_create_or_update - Update or create and instantiate a key.
> - * @keyring_ref: A pointer to the destination keyring with possession flag.
> - * @type: The type of key.
> - * @description: The searchable description for the key.
> - * @payload: The data to use to instantiate or update the key.
> - * @plen: The length of @payload.
> - * @perm: The permissions mask for a new key.
> - * @flags: The quota flags for a new key.
> - *
> - * Search the destination keyring for a key of the same description and if one
> - * is found, update it, otherwise create and instantiate a new one and create a
> - * link to it from that keyring.
> - *
> - * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
> - * concocted.
> - *
> - * Returns a pointer to the new key if successful, -ENODEV if the key type
> - * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
> - * caller isn't permitted to modify the keyring or the LSM did not permit
> - * creation of the key.
> - *
> - * On success, the possession flag from the keyring ref will be tacked on to
> - * the key ref before it is returned.
> +/*
> + * Create or potentially update a key. The combined logic behind
> + * key_create_or_update() and key_create()
> */
> -key_ref_t key_create_or_update(key_ref_t keyring_ref,
> - const char *type,
> - const char *description,
> - const void *payload,
> - size_t plen,
> - key_perm_t perm,
> - unsigned long flags)
> +static key_ref_t __key_create_or_update(key_ref_t keyring_ref,
> + const char *type,
> + const char *description,
> + const void *payload,
> + size_t plen,
> + key_perm_t perm,
> + unsigned long flags,
> + bool allow_update)
> {
> struct keyring_index_key index_key = {
> .description = description,
> @@ -906,14 +886,23 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
> goto error_link_end;
> }
>
> - /* if it's possible to update this type of key, search for an existing
> - * key of the same type and description in the destination keyring and
> - * update that instead if possible
> + /* if it's requested and possible to update this type of key, search
> + * for an existing key of the same type and description in the
> + * destination keyring and update that instead if possible
> */
> - if (index_key.type->update) {
> + if (allow_update) {
> + if (index_key.type->update) {
> + key_ref = find_key_to_update(keyring_ref, &index_key);
> + if (key_ref)
> + goto found_matching_key;
> + }
> + } else {
> key_ref = find_key_to_update(keyring_ref, &index_key);
> - if (key_ref)
> - goto found_matching_key;
> + if (key_ref) {
> + key_ref_put(key_ref);
> + key_ref = ERR_PTR(-EEXIST);
> + goto error_link_end;
> + }
> }
>
> /* if the client doesn't provide, decide on the permissions we want */
> @@ -985,8 +974,94 @@ key_ref_t key_create_or_update(key_ref_t keyring_ref,
>
> goto error_free_prep;
> }
> +
> +/**
> + * key_create_or_update - Update or create and instantiate a key.
> + * @keyring_ref: A pointer to the destination keyring with possession flag.
> + * @type: The type of key.
> + * @description: The searchable description for the key.
> + * @payload: The data to use to instantiate or update the key.
> + * @plen: The length of @payload.
> + * @perm: The permissions mask for a new key.
> + * @flags: The quota flags for a new key.
> + *
> + * Search the destination keyring for a key of the same description and if one
> + * is found, update it, otherwise create and instantiate a new one and create a
> + * link to it from that keyring.
> + *
> + * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
> + * concocted.
> + *
> + * Returns a pointer to the new key if successful, -ENODEV if the key type
> + * wasn't available, -ENOTDIR if the keyring wasn't a keyring, -EACCES if the
> + * caller isn't permitted to modify the keyring or the LSM did not permit
> + * creation of the key.
> + *
> + * On success, the possession flag from the keyring ref will be tacked on to
> + * the key ref before it is returned.
> + */
> +key_ref_t key_create_or_update(key_ref_t keyring_ref,
> + const char *type,
> + const char *description,
> + const void *payload,
> + size_t plen,
> + key_perm_t perm,
> + unsigned long flags)
> +{
> + return __key_create_or_update(keyring_ref,
> + type,
> + description,
> + payload,
> + plen,
> + perm,
> + flags,
> + true);
> +}
> EXPORT_SYMBOL(key_create_or_update);
>
> +/**
> + * key_create - Create and instantiate a key.
> + * @keyring_ref: A pointer to the destination keyring with possession flag.
> + * @type: The type of key.
> + * @description: The searchable description for the key.
> + * @payload: The data to use to instantiate or update the key.
> + * @plen: The length of @payload.
> + * @perm: The permissions mask for a new key.
> + * @flags: The quota flags for a new key.
> + *
> + * Create and instantiate a new key and link to it from the destination keyring.
> + *
> + * If perm is KEY_PERM_UNDEF then an appropriate key permissions mask will be
> + * concocted.
> + *
> + * Returns a pointer to the new key if successful, -EEXIST if a key with the
> + * same description already exists, -ENODEV if the key type wasn't available,
> + * -ENOTDIR if the keyring wasn't a keyring, -EACCES if the caller isn't
> + * permitted to modify the keyring or the LSM did not permit creation of the
> + * key.
> + *
> + * On success, the possession flag from the keyring ref will be tacked on to
> + * the key ref before it is returned.
> + */
> +key_ref_t key_create(key_ref_t keyring_ref,
> + const char *type,
> + const char *description,
> + const void *payload,
> + size_t plen,
> + key_perm_t perm,
> + unsigned long flags)
> +{
> + return __key_create_or_update(keyring_ref,
> + type,
> + description,
> + payload,
> + plen,
> + perm,
> + flags,
> + false);

I'd consider:

return __key_create_or_update(keyring_ref, type, description, payload, plen, perm, flags,
false);

I don't see any logical reason to spread this to 8 lines.

> +}
> +EXPORT_SYMBOL(key_create);
> +
> /**
> * key_update - Update a key's contents.
> * @key_ref: The pointer (plus possession flag) to the key.
>
> --
> 2.39.0

BR, Jarkko