[PATCH v2 2/8] lib: crypto: add public_key_verify_signature()

[Heinrich Schuchardt]

On 16.06.20 07:26, AKASHI Takahiro wrote:
> This function will be called from x509_check_for_self_signed() and
> pkcs7_verify_one(), which will be imported from linux in a later patch.
>
> While it does exist in linux code and has a similar functionality of
> rsa_verify(), it calls further linux-specific interfaces inside.
> That could lead to more files being imported from linux.
>
> So simply re-implement it here instead of re-using the code.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> ---
>  include/crypto/public_key.h |  2 +-
>  lib/crypto/public_key.c     | 63 ++++++++++++++++++++++++++++++++++++-
>  2 files changed, 63 insertions(+), 2 deletions(-)
>
> diff --git a/include/crypto/public_key.h b/include/crypto/public_key.h
> index 436a1ee1ee64..3ba90fcc3483 100644
> --- a/include/crypto/public_key.h
> +++ b/include/crypto/public_key.h
> @@ -82,9 +82,9 @@ extern int decrypt_blob(struct kernel_pkey_params *, const void *, void *);
>  extern int create_signature(struct kernel_pkey_params *, const void *, void *);
>  extern int verify_signature(const struct key *,
>  			    const struct public_key_signature *);
> +#endif /* __UBOOT__ */
>
>  int public_key_verify_signature(const struct public_key *pkey,
>  				const struct public_key_signature *sig);
> -#endif /* !__UBOOT__ */
>
>  #endif /* _LINUX_PUBLIC_KEY_H */
> diff --git a/lib/crypto/public_key.c b/lib/crypto/public_key.c
> index e12ebbb3d0c5..013ea71a180f 100644
> --- a/lib/crypto/public_key.c
> +++ b/lib/crypto/public_key.c
> @@ -25,7 +25,10 @@
>  #include <keys/asymmetric-subtype.h>
>  #endif
>  #include <crypto/public_key.h>
> -#ifndef __UBOOT__
> +#ifdef __UBOOT__
> +#include <image.h>
> +#include <u-boot/rsa.h>
> +#else
>  #include <crypto/akcipher.h>
>  #endif
>
> @@ -80,6 +83,64 @@ void public_key_signature_free(struct public_key_signature *sig)
>  }
>  EXPORT_SYMBOL_GPL(public_key_signature_free);
>
> +/**
> + * public_key_verify_signature - Verify a signature using a public key.
> + *
> + * @pkey:	Public key
> + * @sig:	Signature
> + *
> + * Verify a signature, @sig, using a RSA public key, @pkey.
> + *
> + * Return:	0 - verified, non-zero error code - otherwise
> + */
> +int public_key_verify_signature(const struct public_key *pkey,
> +				const struct public_key_signature *sig)
> +{
> +	struct image_sign_info info;
> +	struct image_region region;
> +	int ret;
> +
> +	pr_devel("==>%s()\n", __func__);
> +
> +	if (!pkey || !sig)
> +		return -EINVAL;
> +
> +	if (pkey->key_is_private)
> +		return -EINVAL;
> +
> +	memset(&info, '\0', sizeof(info));
> +	info.padding = image_get_padding_algo("pkcs-1.5");
> +	/*
> +	 * Note: image_get_[checksum|crypto]_algo takes an string

nits

%/an string/a string/g

> +	 * argument like "<checksum>,<crypto>"
> +	 * TODO: support other hash algorithms
> +	 */
> +	if (!strcmp(sig->hash_algo, "sha1")) {

In our coding sig->key_algo can have values "rsa" or "ecrdsa". See
lib/crypto/x509_cert_parser.c:471. Please, check the value.

You can use sig->s_size * 8 to get the actual key size.

You should check the return value of image_get_checksum_algo().

if (!strcmp(sig->key_algo, "rsa")) {
	char algo[16];
	snprintf(algo, sizeof(algo), "%s,rsa%d", sig->hash_algo, 8 * sig->s_size);
	info.checksum = image_get_checksum_algo(algo);
}
if (!info.checksum)
	return -ENOPKG;
}

> +		info.checksum = image_get_checksum_algo("sha1,rsa2048");
> +		info.name = "sha1,rsa2048";
> +	} else if (!strcmp(sig->hash_algo, "sha256")) {
> +		info.checksum = image_get_checksum_algo("sha256,rsa2048");
> +		info.name = "sha256,rsa2048";
> +	} else {
> +		pr_warn("unknown msg digest algo: %s\n", sig->hash_algo);

Please, use log_warning().

> +		return -ENOPKG;
> +	}
> +	info.crypto = image_get_crypto_algo(info.name);
> +
> +	info.key = pkey->key;
> +	info.keylen = pkey->keylen;
> +
> +	region.data = sig->digest;
> +	region.size = sig->digest_size;
> +
> +	if (rsa_verify_with_pkey(&info, sig->digest, sig->s, sig->s_size))

Why warning above but no debug message here?

> +		ret = -EKEYREJECTED;
> +	else
> +		ret = 0;
> +
> +	pr_devel("<==%s() = %d\n", __func__, ret);

log_content()

Best regards

Heinrich


> +	return ret;
> +}
>  #else
>  /*
>   * Destroy a public key algorithm key.
>