[RFC,3/4] PCI/CMA: Initial support for Component Measurement and Authentication ECN

This currently very much a PoC.  Currently the SPDM library only provides
a single function to allow a challenge / authentication of the PCI EP.

SPDM exchanges must occur in one of a small set of valid squences over
which the message digest used in authentication is built up.
Placing that complexity in the SPDM library seems like a good way
to enforce that logic, without having to do it for each transport.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/pci/Kconfig     | 9 +++++++++
 drivers/pci/Makefile    | 1 +
 drivers/pci/doe.c       | 2 --
 include/linux/pci-doe.h | 2 ++
 4 files changed, 12 insertions(+), 2 deletions(-)

On Thu, 5 Aug 2021 00:18:38 +0800
Jonathan Cameron <Jonathan.Cameron@huawei.com> wrote:

> This currently very much a PoC.  Currently the SPDM library only provides
> a single function to allow a challenge / authentication of the PCI EP.
> 
> SPDM exchanges must occur in one of a small set of valid squences over
> which the message digest used in authentication is built up.
> Placing that complexity in the SPDM library seems like a good way
> to enforce that logic, without having to do it for each transport.
> 
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

This is far more likely to work if I actually include the missing drivers/pci/cma.c
I'll send a v2 next week, but in the meantime it should look like this.

From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
To: <jonathan.cameron@huawei.com>
Subject: [PATCH] pci/cma: Missing file
Date: Sat, 18 Sep 2021 00:16:00 +0800
X-Mailer: git-send-email 2.19.1

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/pci/cma.c | 102 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)

diff --git a/drivers/pci/cma.c b/drivers/pci/cma.c
new file mode 100644
index 000000000000..58fef73674fe
--- /dev/null
+++ b/drivers/pci/cma.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Component Measurement and Authentication was added as an ECN to the
+ * PCIe r5.0 spec.
+ *
+ * Copyright (C) 2021 Huawei
+ *     Jonathan Cameron <Jonathan.Cameron@huawei.com>
+ */
+
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/pci-cma.h>
+#include <linux/pci-doe.h>
+#include <linux/spdm.h>
+
+/* Keyring that userspace can poke certs into */
+static struct key *cma_keyring;
+
+static int cma_spdm_ex(void *priv, struct spdm_exchange *spdm_ex)
+{
+	size_t request_padded_sz, response_padded_sz;
+	struct pci_doe_exchange ex = {
+		.vid = PCI_VENDOR_ID_PCI_SIG,
+		.protocol = PCI_DOE_PROTOCOL_CMA,
+	};
+	struct pci_doe *doe = priv;
+	int rc;
+
+	/* DOE requires that response and request are padded to a multiple of 4 bytes */
+	request_padded_sz = ALIGN(spdm_ex->request_pl_sz, sizeof(u32));
+	if (request_padded_sz != spdm_ex->request_pl_sz) {
+		ex.request_pl = kzalloc(request_padded_sz, GFP_KERNEL);
+		if (!ex.request_pl)
+			return -ENOMEM;
+		memcpy(ex.request_pl, spdm_ex->request_pl, spdm_ex->request_pl_sz);
+		ex.request_pl_sz = request_padded_sz;
+	} else {
+		ex.request_pl = (u32 *)spdm_ex->request_pl;
+		ex.request_pl_sz = spdm_ex->request_pl_sz;
+	}
+
+	response_padded_sz = ALIGN(spdm_ex->response_pl_sz, sizeof(u32));
+	if (response_padded_sz != spdm_ex->response_pl_sz) {
+		ex.response_pl = kzalloc(response_padded_sz, GFP_KERNEL);
+		if (!ex.response_pl) {
+			rc = -ENOMEM;
+			goto err_free_req;
+		}
+		ex.response_pl_sz = response_padded_sz;
+	} else {
+		ex.response_pl = (u32 *)spdm_ex->response_pl;
+		ex.response_pl_sz = spdm_ex->response_pl_sz;
+	}
+
+	rc = pci_doe_exchange_sync(doe, &ex);
+	if (rc < 0)
+		goto err_free_rsp;
+
+	if (response_padded_sz != spdm_ex->response_pl_sz)
+		memcpy(spdm_ex->response_pl, ex.response_pl, spdm_ex->response_pl_sz);
+
+err_free_rsp:
+	if (response_padded_sz != spdm_ex->response_pl_sz)
+		kfree(ex.response_pl);
+err_free_req:
+	if (request_padded_sz != spdm_ex->request_pl_sz)
+		kfree(ex.request_pl);
+
+	return rc;
+}
+
+void pci_cma_init(struct pci_doe *doe, struct spdm_state *spdm_state)
+{
+	memset(spdm_state, 0, sizeof(*spdm_state));
+	spdm_state->transport_ex = cma_spdm_ex;
+	spdm_state->transport_priv = doe;
+	spdm_state->dev = &doe->pdev->dev;
+	spdm_state->root_keyring = cma_keyring;
+}
+EXPORT_SYMBOL_GPL(pci_cma_init);
+
+int pci_cma_authenticate(struct spdm_state *spdm_state)
+{
+	return spdm_authenticate(spdm_state);
+}
+EXPORT_SYMBOL_GPL(pci_cma_authenticate);
+
+__init static int cma_keyring_init(void)
+{
+	cma_keyring = keyring_alloc("_cma",
+				    KUIDT_INIT(0), KGIDT_INIT(0),
+				    current_cred(),
+				    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+				    KEY_USR_VIEW | KEY_USR_READ | KEY_USR_WRITE | KEY_USR_SEARCH,
+				    KEY_ALLOC_NOT_IN_QUOTA | KEY_ALLOC_SET_KEEP, NULL, NULL);
+	if (IS_ERR(cma_keyring))
+		pr_err("Could not allocate cma keyring\n");
+
+	return 0;
+}
+device_initcall(cma_keyring_init);
+MODULE_LICENSE("GPL v2");