Re: [PATCH v2 2/3] KEYS: Add key_create()

[Jarkko Sakkinen <jarkko@kernel.org>]

On Wed, Nov 09, 2022 at 03:50:18AM +0100, Thomas Weißschuh wrote:
> This function works like key_create_or_update() but does not allow
> updating an existing key instead returning -EEXIST.
> 
> This new function will be used by the blacklist keyring.

How?

> 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);
> +}
> +EXPORT_SYMBOL(key_create);
> +
>  /**
>   * key_update - Update a key's contents.
>   * @key_ref: The pointer (plus possession flag) to the key.
> -- 
> 2.38.1
> 

BR, Jarkko