[PATCH 3/5] lib: ecdsa: Implement signature verification for crypto_algo API

[Patrick DELAUNAY]

Hi,

On 1/11/21 4:41 PM, Alexandru Gagniuc wrote:
> Implement the crypto_algo .verify() function for ecdsa256. Because
> it backends on UCLASS_ECDSA, this change is focused on parsing the
> keys from devicetree and passing this information to the specific
> UCLASS driver.
>
> Signed-off-by: Alexandru Gagniuc<mr.nuke.me at gmail.com>
> ---
>   lib/ecdsa/ecdsa-verify.c | 117 ++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 116 insertions(+), 1 deletion(-)
>
> diff --git a/lib/ecdsa/ecdsa-verify.c b/lib/ecdsa/ecdsa-verify.c
> index d2e6a40f4a..d84f6eb093 100644
> --- a/lib/ecdsa/ecdsa-verify.c
> +++ b/lib/ecdsa/ecdsa-verify.c
> @@ -1,13 +1,128 @@
>   // SPDX-License-Identifier: GPL-2.0+
>   /*
> + * ECDSA signature verification for u-boot
> + *
> + * This implements the firmware-side wrapper for ECDSA verification. It bridges
> + * the struct crypto_algo API to the ECDSA uclass implementations.
> + *
>    * Copyright (c) 2020, Alexandru Gagniuc<mr.nuke.me at gmail.com>
>    */
>   

http://www.denx.de/wiki/U-Boot/CodingStyle #Include files

#include <crypto/ecdsa-uclass.h>

it is normally the first in alphabetic order of directory

> +#include <dm/uclass.h>
>   #include <u-boot/ecdsa.h>
> +#include <crypto/ecdsa-uclass.h>
> +
> +/*
> + * Derive size of an ECDSA key from the curve name
> + *
> + * While it's possible to extract the key size by using string manipulation,
> + * use a list of known curves for the time being.
> + */
> +static int ecdsa_key_size(const char *curve_name)
> +{
> +	if (!strcmp(curve_name, "prime256v1"))
> +		return 256;
> +	else
> +		return 0;
> +}
> +


To prepare the future can you parse a array of supported curves with 
associated ID

used as parameter of ECDSA parameter = enum ECDSA_CURVES

for example: char * name, int size, enum ECDSA_CURVES

const [] = {
{"prime256v1", 256, ECDSA_PRIME256V1 },

}


> +static int fdt_get_key(struct ecdsa_public_key *key, const void *fdt, int node)
> +{
> +	int x_len, y_len;
> +
> +	key->curve_name = fdt_getprop(fdt, node, "ecdsa,curve", NULL);
> +	key->size_bits = ecdsa_key_size(key->curve_name);
> +	if (key->size_bits == 0) {
> +		debug("Unknown ECDSA curve '%s'", key->curve_name);
> +		return -EINVAL;
> +	}
> +
> +	key->x = fdt_getprop(fdt, node, "ecdsa,x-point", &x_len);
> +	key->y = fdt_getprop(fdt, node, "ecdsa,y-point", &y_len);
> +
> +	if (!key->x || !key->y)
> +		return -EINVAL;
> +
> +	if (x_len != (key->size_bits / 8) || y_len != (key->size_bits / 8)) {
> +		printf("%s: node=%d, curve@%p x@%p+%i y@%p+%i\n", __func__,
> +		       node, key->curve_name, key->x, x_len, key->y, y_len);
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static int ecdsa_verify_hash(struct udevice *dev,
> +			     const struct image_sign_info *info,
> +			     const void *hash, const void *sig, uint sig_len)
> +{
> +	const struct ecdsa_ops *ops = device_get_ops(dev);
> +	const struct checksum_algo *algo = info->checksum;
> +	struct ecdsa_public_key key;
> +	int sig_node, key_node, ret;
> +
> +	if (!ops || !ops->verify)
> +		return -ENODEV;
> +
> +	if (info->required_keynode > 0) {
> +		ret = fdt_get_key(&key, info->fdt_blob, info->required_keynode);
> +		if (ret < 0)
> +			return ret;
> +
> +		return ops->verify(dev, &key, hash, algo->checksum_len,
> +				   sig, sig_len);


Need to indicate the used curve here as parameter of the verify opts ?


> +	}
> +
> +	sig_node = fdt_subnode_offset(info->fdt_blob, 0, FIT_SIG_NODENAME);
> +	if (sig_node < 0)
> +		return -ENOENT;
> +
> +	/* Try all possible keys under the "/signature" node */
> +	fdt_for_each_subnode(key_node, info->fdt_blob, sig_node) {
> +		ret = fdt_get_key(&key, info->fdt_blob, key_node);
> +		if (ret < 0)
> +			continue;
> +
> +		ret = ops->verify(dev, &key, hash, algo->checksum_len,
> +				  sig, sig_len);
> +
> +		/* On success, don't worry about remaining keys */
> +		if (ret == 0)


issue raised by chekpatch I think

if (!ret)


> +			return 0;
> +	}
> +
> +	return -EPERM;
> +}
>   
>   int ecdsa_verify(struct image_sign_info *info,
>   		 const struct image_region region[], int region_count,
>   		 uint8_t *sig, uint sig_len)
>   {
> -	return -EOPNOTSUPP;
> +	const struct checksum_algo *algo = info->checksum;
> +	uint8_t hash[algo->checksum_len];
> +	struct udevice *dev;
> +	int ret;
> +
> +	ret = uclass_first_device(UCLASS_ECDSA, &dev);
> +	if (ret) {
> +		debug("ECDSA: Could not find ECDSA implementation: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = algo->calculate(algo->name, region, region_count, hash);
> +	if (ret < 0)
> +		return -EINVAL;
> +
> +	return ecdsa_verify_hash(dev, info, hash, sig, sig_len);
>   }
> +
> +/*
> + * uclass definition for ECDSA API
> + *
> + * We don't implement any wrappers around ecdsa_ops->verify() because it's
> + * trivial to call ops->verify().
> + */
> +UCLASS_DRIVER(ecdsa) = {
> +	.id		= UCLASS_ECDSA,
> +	.name		= "ecdsa_verifier",
> +};


Regards

Patrick