[RFC PATCH v3 3/4] PCI/CMA: Initial support for Component Measurement and Authentication ECN

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

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     |  13 +++++
 drivers/pci/Makefile    |   1 +
 drivers/pci/cma.c       | 117 ++++++++++++++++++++++++++++++++++++++++
 include/linux/pci-cma.h |  21 ++++++++
 4 files changed, 152 insertions(+)

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 55c028af4bd9..b25e97a1e771 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -118,6 +118,19 @@ config XEN_PCIDEV_FRONTEND
 	  The PCI device frontend driver allows the kernel to import arbitrary
 	  PCI devices from a PCI backend to support PCI driver domains.
 
+config PCI_CMA
+	tristate "PCI Component Measurement and Authentication"
+	select PCI_DOE
+	select ASN1_ENCODER
+	select SPDM
+	help
+	  This enables library support for the PCI Component Measurement and
+	  Authentication introduce in PCI r6.0 sec 6.31. A PCI DOE mailbox is
+	  used as the transport for DMTF SPDM based attestation, measurement
+	  and secure channel establishment.
+
+	  If built as a module will be called cma.ko.
+
 config PCI_ATS
 	bool
 
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 2680e4c92f0a..d2e38b2baeae 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_PCI_P2PDMA)	+= p2pdma.o
 obj-$(CONFIG_XEN_PCIDEV_FRONTEND) += xen-pcifront.o
 obj-$(CONFIG_VGA_ARB)		+= vgaarb.o
 obj-$(CONFIG_PCI_DOE)		+= doe.o
+obj-$(CONFIG_PCI_CMA)		+= cma.o
 
 # Endpoint library must be initialized before its users
 obj-$(CONFIG_PCI_ENDPOINT)	+= endpoint/
diff --git a/drivers/pci/cma.c b/drivers/pci/cma.c
new file mode 100644
index 000000000000..b38b7a688266
--- /dev/null
+++ b/drivers/pci/cma.c
@@ -0,0 +1,117 @@
+// 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>
+
+#define PCI_DOE_PROTOCOL_CMA 1
+/* Keyring that userspace can poke certs into */
+static struct key *cma_keyring;
+
+static void cxl_doe_task_complete(struct pci_doe_task *task)
+{
+	complete(task->private);
+}
+
+static int cma_spdm_ex(void *priv, struct spdm_exchange *spdm_ex)
+{
+	size_t request_padded_sz, response_padded_sz;
+	struct completion c = COMPLETION_INITIALIZER_ONSTACK(c);
+	struct pci_doe_task task = {
+		.prot = {
+			.vid = PCI_VENDOR_ID_PCI_SIG,
+			.type = PCI_DOE_PROTOCOL_CMA,
+		},
+		.complete = cxl_doe_task_complete,
+		.private = &c,
+	};
+	struct pci_doe_mb *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_sz, sizeof(u32));
+	if (request_padded_sz != spdm_ex->request_sz) {
+		task.request_pl = kzalloc(request_padded_sz, GFP_KERNEL);
+		if (!task.request_pl)
+			return -ENOMEM;
+		memcpy(task.request_pl, spdm_ex->request, spdm_ex->request_sz);
+		task.request_pl_sz = request_padded_sz;
+	} else {
+		task.request_pl = (u32 *)spdm_ex->request;
+		task.request_pl_sz = spdm_ex->request_sz;
+	}
+
+	response_padded_sz = ALIGN(spdm_ex->response_sz, sizeof(u32));
+	if (response_padded_sz != spdm_ex->response_sz) {
+		task.response_pl = kzalloc(response_padded_sz, GFP_KERNEL);
+		if (!task.response_pl) {
+			rc = -ENOMEM;
+			goto err_free_req;
+		}
+		task.response_pl_sz = response_padded_sz;
+	} else {
+		task.response_pl = (u32 *)spdm_ex->response;
+		task.response_pl_sz = spdm_ex->response_sz;
+	}
+
+	rc = pci_doe_submit_task(doe, &task);
+	if (rc < 0)
+		goto err_free_rsp;
+
+	wait_for_completion(&c);
+	if (response_padded_sz != spdm_ex->response_sz)
+		memcpy(spdm_ex->response, task.response_pl, spdm_ex->response_sz);
+
+	rc = task.rv;
+err_free_rsp:
+	if (response_padded_sz != spdm_ex->response_sz)
+		kfree(task.response_pl);
+err_free_req:
+	if (request_padded_sz != spdm_ex->request_sz)
+		kfree(task.request_pl);
+
+	return rc;
+}
+
+struct spdm_state *pci_cma_create(struct device *dev, struct pci_doe_mb *doe)
+{
+	return spdm_create(cma_spdm_ex, doe, dev, cma_keyring);
+}
+EXPORT_SYMBOL_GPL(pci_cma_create);
+
+void pci_cma_destroy(struct spdm_state *spdm_state)
+{
+	kfree(spdm_state);
+}
+EXPORT_SYMBOL_GPL(pci_cma_destroy);
+
+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");
diff --git a/include/linux/pci-cma.h b/include/linux/pci-cma.h
new file mode 100644
index 000000000000..d2a0a84973bf
--- /dev/null
+++ b/include/linux/pci-cma.h
@@ -0,0 +1,21 @@
+/* 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>
+ */
+
+#ifndef _PCI_CMA_H_
+#define _PCI_CMA_H_
+struct pci_doe_mb;
+struct spdm_state;
+struct device;
+
+struct spdm_state *pci_cma_create(struct device *dev, struct pci_doe_mb *doe);
+void pci_cma_destroy(struct spdm_state *spdm_state);
+
+int pci_cma_authenticate(struct spdm_state *spdm_state);
+
+#endif
-- 
2.32.0