Re: [PATCH v2 19/19] fit: Add ecdsa support

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 01.08.24 07:57, Sascha Hauer wrote:
> This adds ECDSA signing support to the FIT image code.
> 
> Previously we unconditionally called into rsa_verify() as this was the
> only option. Now with ECDSA support we first have to check the type of
> the signature, so we start evaluating the signature type in given in the
> FIT image and call rsa_verify() or ecdsa_verify() depending on it.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

> ---
>  common/image-fit.c | 112 +++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 94 insertions(+), 18 deletions(-)
> 
> diff --git a/common/image-fit.c b/common/image-fit.c
> index 6002440e7e..599d969a38 100644
> --- a/common/image-fit.c
> +++ b/common/image-fit.c
> @@ -21,6 +21,7 @@
>  #include <linux/err.h>
>  #include <stringlist.h>
>  #include <rsa.h>
> +#include <ecdsa.h>
>  #include <uncompress.h>
>  #include <image-fit.h>
>  
> @@ -253,13 +254,11 @@ static struct digest *fit_alloc_digest(struct device_node *sig_node,
>  	return digest;
>  }
>  
> -static int fit_check_rsa_signature(struct device_node *sig_node,
> -				   enum hash_algo algo, void *hash)
> +static int fit_check_rsa_signature(const void *signature, size_t sig_len,
> +				   enum hash_algo algo, void *hash,
> +				   const char *key_name)
>  {
>  	const struct rsa_public_key *key;
> -	const char *key_name = NULL;
> -	int sig_len;
> -	const char *sig_value;
>  	int ret;
>  
>  	if (!IS_ENABLED(CONFIG_CRYPTO_RSA)) {
> @@ -267,17 +266,10 @@ static int fit_check_rsa_signature(struct device_node *sig_node,
>  		return -EOPNOTSUPP;
>  	}
>  
> -	sig_value = of_get_property(sig_node, "value", &sig_len);
> -	if (!sig_value) {
> -		pr_err("signature value not found in %pOF\n", sig_node);
> -		return -EINVAL;
> -	}
> -
> -	of_property_read_string(sig_node, "key-name-hint", &key_name);
>  	if (key_name) {
>  		key = rsa_get_key(key_name);
>  		if (key) {
> -			ret = rsa_verify(key, sig_value, sig_len, hash, algo);
> +			ret = rsa_verify(key, signature, sig_len, hash, algo);
>  			if (!ret)
>  				goto ok;
>  		}
> @@ -287,20 +279,104 @@ static int fit_check_rsa_signature(struct device_node *sig_node,
>  		if (key_name && !strcmp(key->key_name_hint, key_name))
>  			continue;
>  
> -		ret = rsa_verify(key, sig_value, sig_len, hash, algo);
> +		ret = rsa_verify(key, signature, sig_len, hash, algo);
>  		if (!ret)
>  			goto ok;
>  	}
>  
> -	pr_err("image signature BAD\n");
> +	pr_err("image RSA signature BAD\n");
>  
>  	return -EBADMSG;
>  ok:
> -	pr_info("image signature OK\n");
> +	pr_info("image RSA signature OK\n");
>  
>  	return 0;
>  }
>  
> +static int fit_check_ecdsa_signature(const void *signature, size_t sig_len,
> +				     enum hash_algo algo, void *hash,
> +				     const char *key_name)
> +{
> +	const struct ecdsa_public_key *key;
> +	int ret;
> +
> +	if (!IS_ENABLED(CONFIG_CRYPTO_ECDSA)) {
> +		pr_err("ECDSA support is disabled, Cannot verify image\n");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	for_each_ecdsa_key(key) {
> +		ret = ecdsa_verify(key, signature, sig_len, hash);
> +		if (!ret) {
> +			pr_info("image ECDSA signature OK\n");
> +			return 0;
> +		}
> +	}
> +
> +	pr_err("image ECDSA signature BAD\n");
> +
> +	return -EBADMSG;
> +}
> +
> +struct crypto_algo {
> +	const char *name;
> +	int (*verify)(const void *signature, size_t sig_len, enum hash_algo algo,
> +		      void *hash, const char *key_name);
> +};
> +
> +static struct crypto_algo crypto_algos[] = {
> +	{
> +		.name = "rsa2048",
> +		.verify = fit_check_rsa_signature,
> +	}, {
> +		.name = "rsa3072",
> +		.verify = fit_check_rsa_signature,
> +	}, {
> +		.name = "rsa4096",
> +		.verify = fit_check_rsa_signature,
> +	}, {
> +		.name = "ecdsa256",
> +		.verify = fit_check_ecdsa_signature,
> +	},
> +};
> +
> +static int fit_check_signature(struct device_node *sig_node,
> +			       enum hash_algo algo, void *hash)
> +{
> +	int sig_len, i;
> +	const char *sig_value;
> +	const char *algo_name;
> +	const char *key_name = NULL;
> +	const char *str;
> +
> +	sig_value = of_get_property(sig_node, "value", &sig_len);
> +	if (!sig_value) {
> +		pr_err("signature value not found in %pOF\n", sig_node);
> +		return -EINVAL;
> +	}
> +
> +	of_property_read_string(sig_node, "key-name-hint", &key_name);
> +
> +	if (of_property_read_string(sig_node, "algo", &algo_name)) {
> +		pr_err("algo property not found\n");
> +		return -EINVAL;
> +	}
> +
> +	str = strchr(algo_name, ',');
> +	if (!str)
> +		return -EINVAL;
> +	str++;
> +
> +	for (i = 0; i < ARRAY_SIZE(crypto_algos); i++) {
> +		struct crypto_algo *ca = &crypto_algos[i];
> +
> +		if (!strcmp(ca->name, str))
> +			return ca->verify(sig_value, sig_len, algo, hash, key_name);
> +	}
> +
> +	return -EINVAL;
> +}
> +
>  /*
>   * The consistency of the FTD structure was already checked by of_unflatten_dtb()
>   */
> @@ -346,7 +422,7 @@ static int fit_verify_signature(struct device_node *sig_node, const void *fit)
>  	hash = xzalloc(digest_length(digest));
>  	digest_final(digest, hash);
>  
> -	ret = fit_check_rsa_signature(sig_node, algo, hash);
> +	ret = fit_check_signature(sig_node, algo, hash);
>  	if (ret)
>  		goto out_free_hash;
>  
> @@ -469,7 +545,7 @@ static int fit_image_verify_signature(struct fit_handle *handle,
>  	hash = xzalloc(digest_length(digest));
>  	digest_final(digest, hash);
>  
> -	ret = fit_check_rsa_signature(sig_node, algo, hash);
> +	ret = fit_check_signature(sig_node, algo, hash);
>  
>  	free(hash);
>  

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