Re: [PATCH v3 02/14] rsa: add parser of raw format

["Jarkko Sakkinen" <jarkko@kernel.org>]

On Wed Sep 11, 2024 at 3:28 PM EEST, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> Parse the RSA key with RAW format if the ASN.1 parser returns an error, to
> avoid passing somehow the key format as parameter.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
>  crypto/rsa.c                  | 14 ++++--
>  crypto/rsa_helper.c           | 83 ++++++++++++++++++++++++++++++++++-
>  include/crypto/internal/rsa.h |  6 +++
>  3 files changed, 97 insertions(+), 6 deletions(-)
>
> diff --git a/crypto/rsa.c b/crypto/rsa.c
> index d9be9e86097e..66d42974d47d 100644
> --- a/crypto/rsa.c
> +++ b/crypto/rsa.c
> @@ -272,8 +272,11 @@ static int rsa_set_pub_key(struct crypto_akcipher *tfm, const void *key,
>  	rsa_free_mpi_key(mpi_key);
>  
>  	ret = rsa_parse_pub_key(&raw_key, key, keylen);
> -	if (ret)
> -		return ret;
> +	if (ret) {
> +		ret = rsa_parse_pub_key_raw(&raw_key, key, keylen);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	mpi_key->e = mpi_read_raw_data(raw_key.e, raw_key.e_sz);
>  	if (!mpi_key->e)
> @@ -311,8 +314,11 @@ static int rsa_set_priv_key(struct crypto_akcipher *tfm, const void *key,
>  	rsa_free_mpi_key(mpi_key);
>  
>  	ret = rsa_parse_priv_key(&raw_key, key, keylen);
> -	if (ret)
> -		return ret;
> +	if (ret) {
> +		ret = rsa_parse_priv_key_raw(&raw_key, key, keylen);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	mpi_key->d = mpi_read_raw_data(raw_key.d, raw_key.d_sz);
>  	if (!mpi_key->d)
> diff --git a/crypto/rsa_helper.c b/crypto/rsa_helper.c
> index 94266f29049c..40a17ebc972f 100644
> --- a/crypto/rsa_helper.c
> +++ b/crypto/rsa_helper.c
> @@ -9,6 +9,7 @@
>  #include <linux/export.h>
>  #include <linux/err.h>
>  #include <linux/fips.h>
> +#include <linux/mpi.h>
>  #include <crypto/internal/rsa.h>
>  #include "rsapubkey.asn1.h"
>  #include "rsaprivkey.asn1.h"
> @@ -148,6 +149,42 @@ int rsa_get_qinv(void *context, size_t hdrlen, unsigned char tag,
>  	return 0;
>  }
>  

/*
 * Please, document me.
 */
> +typedef int (*rsa_get_func)(void *, size_t, unsigned char,
> +			    const void *, size_t);
> +
> +static int rsa_parse_key_raw(struct rsa_key *rsa_key,
> +			     const void *key, unsigned int key_len,
> +			     rsa_get_func *func, int n_func)
> +{
> +	unsigned int nbytes, len = key_len;
> +	const void *key_ptr = key;
> +	int ret, i;
> +
> +	for (i = 0; i < n_func; i++) {
> +		if (key_len < 2)
> +			return -EINVAL;
> +
> +		ret = mpi_key_length(key_ptr, len, NULL, &nbytes);
> +		if (ret < 0)
> +			return ret;
> +
> +		key_ptr += 2;
> +		key_len -= 2;
> +
> +		if (key_len < nbytes)
> +			return -EINVAL;
> +
> +		ret = func[i](rsa_key, 0, 0, key_ptr, nbytes);
> +		if (ret < 0)
> +			return ret;
> +
> +		key_ptr += nbytes;
> +		key_len -= nbytes;
> +	}
> +
> +	return 0;
> +}
> +
>  /**
>   * rsa_parse_pub_key() - decodes the BER encoded buffer and stores in the
>   *                       provided struct rsa_key, pointers to the raw key as is,
> @@ -157,7 +194,7 @@ int rsa_get_qinv(void *context, size_t hdrlen, unsigned char tag,
>   * @key:	key in BER format
>   * @key_len:	length of key
>   *
> - * Return:	0 on success or error code in case of error
> + * Return:	0 on success or error code in case of error.
>   */
>  int rsa_parse_pub_key(struct rsa_key *rsa_key, const void *key,
>  		      unsigned int key_len)
> @@ -166,6 +203,27 @@ int rsa_parse_pub_key(struct rsa_key *rsa_key, const void *key,
>  }
>  EXPORT_SYMBOL_GPL(rsa_parse_pub_key);
>  
> +/**
> + * rsa_parse_pub_key_raw() - parse the RAW key and store in the provided struct
> + *                           rsa_key, pointers to the raw key as is, so that
> + *                           the caller can copy it or MPI parse it, etc.
> + *
> + * @rsa_key:	struct rsa_key key representation
> + * @key:	key in RAW format
> + * @key_len:	length of key
> + *
> + * Return:	0 on success or error code in case of error.
> + */
> +int rsa_parse_pub_key_raw(struct rsa_key *rsa_key, const void *key,
> +			  unsigned int key_len)
> +{
> +	rsa_get_func pub_func[] = {rsa_get_n, rsa_get_e};
> +
> +	return rsa_parse_key_raw(rsa_key, key, key_len,
> +				 pub_func, ARRAY_SIZE(pub_func));
> +}
> +EXPORT_SYMBOL_GPL(rsa_parse_pub_key_raw);
> +
>  /**
>   * rsa_parse_priv_key() - decodes the BER encoded buffer and stores in the
>   *                        provided struct rsa_key, pointers to the raw key
> @@ -176,7 +234,7 @@ EXPORT_SYMBOL_GPL(rsa_parse_pub_key);
>   * @key:	key in BER format
>   * @key_len:	length of key
>   *
> - * Return:	0 on success or error code in case of error
> + * Return:	0 on success or error code in case of error.
>   */
>  int rsa_parse_priv_key(struct rsa_key *rsa_key, const void *key,
>  		       unsigned int key_len)
> @@ -184,3 +242,24 @@ int rsa_parse_priv_key(struct rsa_key *rsa_key, const void *key,
>  	return asn1_ber_decoder(&rsaprivkey_decoder, rsa_key, key, key_len);
>  }
>  EXPORT_SYMBOL_GPL(rsa_parse_priv_key);
> +
> +/**
> + * rsa_parse_priv_key_raw() - parse the RAW key and store in the provided struct
> + *                            rsa_key, pointers to the raw key as is, so that
> + *                            the caller can copy it or MPI parse it, etc.

This belongs after the parameters, here a one-liner would be a better
choice:

https://www.kernel.org/doc/Documentation/kernel-doc-nano-HOWTO.txt

Try to avoid "etc" in documentation because then I have no choice than
stop reading your documentation and read source code instead.

Just enumerate everything that makes sense, no aim for perfection but
it is like a stamp that I tried my best, and then we will refine the
description.

"etc" in the documentation encompasses also all the future changes,
which does not encourage accuracy :-) Imcompleteness is less of a
devil than entropy, or at least that is how I weight these matters.

> + *
> + * @rsa_key:	struct rsa_key key representation
> + * @key:	key in RAW format
> + * @key_len:	length of key
> + *
> + * Return:	0 on success or error code in case of error.
> + */
> +int rsa_parse_priv_key_raw(struct rsa_key *rsa_key, const void *key,
> +			   unsigned int key_len)
> +{
> +	rsa_get_func priv_func[] = {rsa_get_n, rsa_get_e, rsa_get_d};
> +
> +	return rsa_parse_key_raw(rsa_key, key, key_len,
> +				 priv_func, ARRAY_SIZE(priv_func));
> +}
> +EXPORT_SYMBOL_GPL(rsa_parse_priv_key_raw);
> diff --git a/include/crypto/internal/rsa.h b/include/crypto/internal/rsa.h
> index e870133f4b77..7141e806ceea 100644
> --- a/include/crypto/internal/rsa.h
> +++ b/include/crypto/internal/rsa.h
> @@ -50,8 +50,14 @@ struct rsa_key {
>  int rsa_parse_pub_key(struct rsa_key *rsa_key, const void *key,
>  		      unsigned int key_len);
>  
> +int rsa_parse_pub_key_raw(struct rsa_key *rsa_key, const void *key,
> +			  unsigned int key_len);
> +
>  int rsa_parse_priv_key(struct rsa_key *rsa_key, const void *key,
>  		       unsigned int key_len);
>  
> +int rsa_parse_priv_key_raw(struct rsa_key *rsa_key, const void *key,
> +			   unsigned int key_len);
> +
>  extern struct crypto_template rsa_pkcs1pad_tmpl;
>  #endif


BR, Jarkko