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List:       linux-keyrings
Subject:    Re: [RFC PATCH 2/2] dm-crypt: Use any key type which is registered
From:       Maik Otto <m.otto () phytec ! de>
Date:       2020-01-17 11:52:21
Message-ID: 97ab8779-1351-0030-7a9f-fababe1f57c2 () phytec ! de
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Hi

little bug fix, because this version chrashed with access violation
on an i.MX6Quad with a Mainline Kernel 4.19.88

> There was only 2 key_type supported by dm-crypt which limits other
> implementations.
> 
> This patch allows to use any key_type which is registered obtaining
> the key_type from key framework.
> 
> This also remove the compilation dependency between dm-crypt and
> key implementations.
> 
> Signed-off-by: Franck LENORMAND <franck.lenormand@nxp.com>
> ---
> drivers/md/dm-crypt.c    | 11 ++++++-----
> include/linux/key-type.h |  2 ++
> security/keys/key.c      | 42 ++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 50 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
> index dd538e6..e25efc2 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -35,6 +35,7 @@
> #include <crypto/authenc.h>
> #include <linux/rtnetlink.h> /* for struct rtattr and RTA macros only */
> #include <keys/user-type.h>
> +#include <linux/key-type.h>
> 
> #include <linux/device-mapper.h>
> 
> @@ -2010,6 +2011,7 @@ static int crypt_set_keyring_key(struct crypt_config *cc, \
> const char *key_string  int ret;
> 	struct key *key;
> 	const struct user_key_payload *ukp;
> +	struct key_type *type;
> 
> 	/*
> 	 * Reject key_string with whitespace. dm core currently lacks code for
> @@ -2025,16 +2027,15 @@ static int crypt_set_keyring_key(struct crypt_config *cc, \
> const char *key_string  if (!key_desc || key_desc == key_string || !strlen(key_desc \
> + 1))  return -EINVAL;
> 
> -	if (strncmp(key_string, "logon:", key_desc - key_string + 1) &&
> -	    strncmp(key_string, "user:", key_desc - key_string + 1))
> -		return -EINVAL;
> +	type = get_key_type(key_string, key_desc - key_string);
> +	if (!type)
> +		return -ENOENT;
> 
> 	new_key_string = kstrdup(key_string, GFP_KERNEL);
> 	if (!new_key_string)
> 		return -ENOMEM;
> 
> -	key = request_key(key_string[0] == 'l' ? &key_type_logon : &key_type_user,
> -			  key_desc + 1, NULL);
> +	key = request_key(type, key_desc + 1, NULL);
> 	if (IS_ERR(key)) {
> 		kzfree(new_key_string);
> 		return PTR_ERR(key);
> diff --git a/include/linux/key-type.h b/include/linux/key-type.h
> index bc9af55..2b2167b 100644
> --- a/include/linux/key-type.h
> +++ b/include/linux/key-type.h
> @@ -176,6 +176,8 @@ extern struct key_type key_type_keyring;
> extern int register_key_type(struct key_type *ktype);
> extern void unregister_key_type(struct key_type *ktype);
> 
> +extern struct key_type *get_key_type(const char *type_name, size_t string_size);
> +
> extern int key_payload_reserve(struct key *key, size_t datalen);
> extern int key_instantiate_and_link(struct key *key,
> 				    const void *data,
> diff --git a/security/keys/key.c b/security/keys/key.c
> index 44a80d6..ef76114 100644
> --- a/security/keys/key.c
> +++ b/security/keys/key.c
> @@ -1156,6 +1156,48 @@ void unregister_key_type(struct key_type *ktype)
> }
> EXPORT_SYMBOL(unregister_key_type);
> 
> +/**
> + * get_key_type - Get the type of key using its name
> + * @type_name: Name of the key type to get
> + * @string_size: Size of the string to match
> + *
> + * The functions support null ended string (string_size == 0) as well as
> + * pointer on a string matching a number of characters (string_size > 0)
> + *
> + * Returns a pointer on the key type if successful, -ENOENT if the key type
> + * is not registered.
> + */
> +struct key_type *get_key_type(const char *type_name, size_t string_size)
> +{
> +	struct key_type *p;
> +	struct key_type *ktype = ERR_PTR(-ENOENT);
> +
> +	if (!type_name)
> +		return ktype;
> +
> +	down_write(&key_types_sem);

down_write(&key_types_sem);   changed to down_read(&key_types_sem);

> +
> +	/* Search the key type in the list */
> +	list_for_each_entry(p, &key_types_list, link) {
> +		if (string_size) {
> +			if (strncmp(p->name, type_name, string_size) == 0) {
> +				ktype = p;
> +				break;
> +			}
> +		} else {
> +			if (strcmp(p->name, type_name) == 0) {
> +				ktype = p;
> +				break;
> +			}
> +		}
> +	}
> +
> +	up_read(&key_types_sem);
> +
> +	return ktype;
> +}
> +EXPORT_SYMBOL(get_key_type);
> +
> /*
> * Initialise the key management state.
> */
> 


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