Re: [RFC PATCH v1 19/38] coco: host: arm64: set_pubkey support

Jonathan Cameron
2025-07-30T14:08:09Z

On Mon, 28 Jul 2025 19:21:56 +0530
"Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org> wrote:

> Add changes to share the device's public key with the RMM.
>
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>

A few minor comments inline.

> diff --git a/drivers/virt/coco/arm-cca-host/rmm-da.c b/drivers/virt/coco/arm-cca-host/rmm-da.c
> index ec8c5bfcee35..3715e6d58c83 100644
> --- a/drivers/virt/coco/arm-cca-host/rmm-da.c
> +++ b/drivers/virt/coco/arm-cca-host/rmm-da.c
> @@ -6,6 +6,9 @@
> #include <linux/pci.h>
> #include <linux/pci-ecam.h>
> #include <asm/rmi_cmds.h>
> +#include <crypto/internal/rsa.h>
> +#include <keys/asymmetric-type.h>
> +#include <keys/x509-parser.h>
>
> #include "rmm-da.h"
>
> @@ -311,6 +314,136 @@ static int do_pdev_communicate(struct pci_tsm *tsm, int target_state)
> return do_dev_communicate(PDEV_COMMUNICATE, tsm, target_state);
> }
>
> +static int parse_certificate_chain(struct pci_tsm *tsm)
> +{
> + struct cca_host_dsc_pf0 *dsc_pf0;
> + unsigned int chain_size;
> + unsigned int offset = 0;
> + u8 *chain_data;
> + int ret = 0;
> +
> + dsc_pf0 = to_cca_dsc_pf0(tsm->pdev);
> + chain_size = dsc_pf0->cert_chain.cache.size;
> + chain_data = dsc_pf0->cert_chain.cache.buf;
> +
> + while (offset < chain_size) {
> + unsigned int cert_len =
> + x509_get_certificate_length(chain_data + offset,
> + chain_size - offset);
> + struct x509_certificate *cert =
> + x509_cert_parse(chain_data + offset, cert_len);
> +
> + if (IS_ERR(cert)) {
> + pr_warn("%s(): parsing of certificate chain not successful\n", __func__);
> + ret = PTR_ERR(cert);

Direct return looks fine here. Maybe add a DEFINE_FREE(x509_cert,...)
as then can use direct returns throughout.

> + break;
> + }
> +
> + if (offset + cert_len == chain_size) {
> + dsc_pf0->cert_chain.public_key = kzalloc(cert->pub->keylen, GFP_KERNEL);
> + if (!dsc_pf0->cert_chain.public_key) {
> + ret = -ENOMEM;
> + x509_free_certificate(cert);
> + break;
> + }
> +
> + if (!strcmp("ecdsa-nist-p256", cert->pub->pkey_algo)) {
> + dsc_pf0->rmi_signature_algorithm = RMI_SIG_ECDSA_P256;
> + } else if (!strcmp("ecdsa-nist-p384", cert->pub->pkey_algo)) {
> + dsc_pf0->rmi_signature_algorithm = RMI_SIG_ECDSA_P384;
> + } else if (!strcmp("rsa", cert->pub->pkey_algo)) {
> + dsc_pf0->rmi_signature_algorithm = RMI_SIG_RSASSA_3072;
> + } else {
> + ret = -ENXIO;
> + x509_free_certificate(cert);
> + break;
> + }
> + memcpy(dsc_pf0->cert_chain.public_key, cert->pub->key, cert->pub->keylen);
> + dsc_pf0->cert_chain.public_key_size = cert->pub->keylen;
> + }
> +
> + x509_free_certificate(cert);
> +
> + offset += cert_len;
> + }
> +
> + if (ret == 0)
> + dsc_pf0->cert_chain.valid = true;
if (ret)
return ret;

dsc_pf0->cert_chain.valid = true;

return 0;

would be my preference for style here but others may disagree.
> +
> + return ret;
> +}
> +
> +static int pdev_set_public_key(struct pci_tsm *tsm)
> +{
> + struct rmi_public_key_params *key_shared;
> + unsigned long expected_key_len = 0;

Don't set this. It's only used in places where it is explicitly set and
if it is used anywhere else we want the compiler to tell us.

> + struct cca_host_dsc_pf0 *dsc_pf0;
> + int ret;
> +
> + dsc_pf0 = to_cca_dsc_pf0(tsm->pdev);
> + /* Check that all the necessary information was captured from communication */
> + if (!dsc_pf0->cert_chain.valid)
> + return -EINVAL;
> +
> + key_shared = (struct rmi_public_key_params *)get_zeroed_page(GFP_KERNEL);
> + if (!key_shared)
> + return -ENOMEM;
> +
> + key_shared->rmi_signature_algorithm = dsc_pf0->rmi_signature_algorithm;
> +
> + switch (key_shared->rmi_signature_algorithm) {
> + case RMI_SIG_ECDSA_P384:
> + expected_key_len = 97;
> +
> + if (dsc_pf0->cert_chain.public_key_size != expected_key_len)
> + return -EINVAL;
> + key_shared->public_key_len = dsc_pf0->cert_chain.public_key_size;
> + memcpy(key_shared->public_key,
> + dsc_pf0->cert_chain.public_key,
> + dsc_pf0->cert_chain.public_key_size);
> + key_shared->metadata_len = 0;
> + break;
> + case RMI_SIG_ECDSA_P256:
> + expected_key_len = 65;
> +
> + if (dsc_pf0->cert_chain.public_key_size != expected_key_len)
> + return -EINVAL;
> + key_shared->public_key_len = dsc_pf0->cert_chain.public_key_size;
> + memcpy(key_shared->public_key,
> + dsc_pf0->cert_chain.public_key,
> + dsc_pf0->cert_chain.public_key_size);
> + key_shared->metadata_len = 0;
> + break;
> + case RMI_SIG_RSASSA_3072:
> + expected_key_len = 385;
> + struct rsa_key rsa_key = {0};

Shouldn't define this inline. Maybe move up a line and add some {}
to set the scope to this case statement.

> + int ret_rsa_parse = rsa_parse_pub_key(&rsa_key,
> + dsc_pf0->cert_chain.public_key,
> + dsc_pf0->cert_chain.public_key_size);
> + /* This also checks the key_len */
> + if (ret_rsa_parse)
> + return ret_rsa_parse;
> + /*
> + * exponent is usally 65537 (size = 24bits) but in rare cases
> + * it size can be as large as the modulus
> + */
> + if (rsa_key.e_sz > expected_key_len)
> + return -EINVAL;
> + key_shared->public_key_len = rsa_key.n_sz;
> + key_shared->metadata_len = rsa_key.e_sz;
> + memcpy(key_shared->public_key, (unsigned char *)rsa_key.n, rsa_key.n_sz);

Why is the cast needed?

> + memcpy(key_shared->metadata, (unsigned char *)rsa_key.e, rsa_key.e_sz);
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + ret = rmi_pdev_set_pubkey(virt_to_phys(dsc_pf0->rmm_pdev),
> + virt_to_phys(key_shared));
> + free_page((unsigned long)key_shared);
> + return ret;
> +}