arch/arm/mach-socfpga/secure_vab.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2020 Intel Corporation <www.intel.com>
 *
 */

#include <asm/arch/mailbox_s10.h>
#include <asm/arch/secure_vab.h>
#include <asm/arch/smc_api.h>
#include <asm/unaligned.h>
#include <exports.h>
#include <linux/errno.h>
#include <linux/intel-smc.h>
#include <log.h>

#define CHUNKSZ_PER_WD_RESET		(256 * SZ_1K)

/*
 * Read the length of the VAB certificate from the end of image
 * and calculate the actual image size (excluding the VAB certificate).
 */
static size_t get_img_size(u8 *img_buf, size_t img_buf_sz)
{
	u8 *img_buf_end = img_buf + img_buf_sz;
	u32 cert_sz = get_unaligned_le32(img_buf_end - sizeof(u32));
	u8 *p = img_buf_end - cert_sz - sizeof(u32);

	/* Ensure p is pointing within the img_buf */
	if (p < img_buf || p > (img_buf_end - VAB_CERT_HEADER_SIZE))
		return 0;

	if (get_unaligned_le32(p) == SDM_CERT_MAGIC_NUM)
		return (size_t)(p - img_buf);

	return 0;
}

/*
 * Vendor Authorized Boot (VAB) is a security feature for authenticating
 * the images such as U-Boot, ARM trusted Firmware, Linux kernel,
 * device tree blob and etc loaded from FIT. User can also trigger
 * the VAB authentication from U-Boot command.
 *
 * This function extracts the VAB certificate and signature block
 * appended at the end of the image, then send to Secure Device Manager
 * (SDM) for authentication. This function will validate the SHA384
 * of the image against the SHA384 hash stored in the VAB certificate
 * before sending the VAB certificate to SDM for authentication.
 *
 * RETURN
 * 0 if authentication success or
 *   if authentication is not required and bypassed on a non-secure device
 * negative error code if authentication fail
 */
int socfpga_vendor_authentication(void **p_image, size_t *p_size)
{
	int retry_count = 20;
	u8 hash384[SHA384_SUM_LEN];
	u64 img_addr, mbox_data_addr;
	size_t img_sz, mbox_data_sz;
	u8 *cert_hash_ptr, *mbox_relocate_data_addr;
	u32 resp = 0, resp_len = 1;
	int ret;

	img_addr = (uintptr_t)*p_image;

	debug("Authenticating image at address 0x%016llx (%ld bytes)\n",
	      img_addr, *p_size);

	img_sz = get_img_size((u8 *)img_addr, *p_size);
	debug("img_sz = %ld\n", img_sz);

	if (!img_sz) {
		puts("VAB certificate not found in image!\n");
		return -ENOKEY;
	}

	if (!IS_ALIGNED(img_sz, sizeof(u32))) {
		printf("Image size (%ld bytes) not aliged to 4 bytes!\n",
		       img_sz);
		return -EBFONT;
	}

	/* Generate HASH384 from the image */
	sha384_csum_wd((u8 *)img_addr, img_sz, hash384, CHUNKSZ_PER_WD_RESET);

	cert_hash_ptr = (u8 *)(img_addr + img_sz + VAB_CERT_MAGIC_OFFSET +
			       VAB_CERT_FIT_SHA384_OFFSET);

	/*
	 * Compare the SHA384 found in certificate against the SHA384
	 * calculated from image
	 */
	if (memcmp(hash384, cert_hash_ptr, SHA384_SUM_LEN)) {
		puts("SHA384 not match!\n");
		return -EKEYREJECTED;
	}

	mbox_data_addr = img_addr + img_sz - sizeof(u32);
	/* Size in word (32bits) */
	mbox_data_sz = (ALIGN(*p_size - img_sz, sizeof(u32))) >> 2;

	debug("mbox_data_addr = 0x%016llx\n", mbox_data_addr);
	debug("mbox_data_sz = %ld words\n", mbox_data_sz);

	/*
	 * Relocate certificate to first memory block before trigger SMC call
	 * to send mailbox command because ATF only able to access first
	 * memory block.
	 */
	mbox_relocate_data_addr = (u8 *)malloc(mbox_data_sz * sizeof(u32));
	if (!mbox_relocate_data_addr) {
		puts("Out of memory for VAB certificate relocation!\n");
		return -ENOMEM;
	}

	memcpy(mbox_relocate_data_addr, (u8 *)mbox_data_addr, mbox_data_sz * sizeof(u32));
	*(u32 *)mbox_relocate_data_addr = 0;

	debug("mbox_relocate_data_addr = 0x%p\n", mbox_relocate_data_addr);

	do {
		if (!IS_ENABLED(CONFIG_SPL_BUILD) && IS_ENABLED(CONFIG_SPL_ATF)) {
			/* Invoke SMC call to ATF to send the VAB certificate to SDM */
			ret  = smc_send_mailbox(MBOX_VAB_SRC_CERT, mbox_data_sz,
						(u32 *)mbox_relocate_data_addr, 0, &resp_len,
						&resp);
		} else {
			/* Send the VAB certficate to SDM for authentication */
			ret = mbox_send_cmd(MBOX_ID_UBOOT, MBOX_VAB_SRC_CERT,
					    MBOX_CMD_DIRECT, mbox_data_sz,
					    (u32 *)mbox_relocate_data_addr, 0, &resp_len,
					    &resp);
		}
		/* If SDM is not available, just delay 50ms and retry again */
		if (ret == MBOX_RESP_DEVICE_BUSY)
			mdelay(50);
		else
			break;
	} while (--retry_count);

	/* Free the relocate certificate memory space */
	free(mbox_relocate_data_addr);

	/* Exclude the size of the VAB certificate from image size */
	*p_size = img_sz;

	debug("ret = 0x%08x, resp = 0x%08x, resp_len = %d\n", ret, resp,
	      resp_len);

	if (ret) {
		/*
		 * Unsupported mailbox command or device not in the
		 * owned/secure state
		 */
		if (ret == MBOX_RESP_NOT_ALLOWED_UNDER_SECURITY_SETTINGS) {
			/* SDM bypass authentication */
			printf("%s 0x%016llx (%ld bytes)\n",
			       "Image Authentication bypassed at address",
			       img_addr, img_sz);
			return 0;
		}
		puts("VAB certificate authentication failed in SDM");
		if (ret == MBOX_RESP_DEVICE_BUSY) {
			puts(" (SDM busy timeout)\n");
			return -ETIMEDOUT;
		} else if (ret == MBOX_RESP_UNKNOWN) {
			puts(" (Not supported)\n");
			return -ESRCH;
		}
		puts("\n");
		return -EKEYREJECTED;
	} else {
		/* If Certificate Process Status has error */
		if (resp) {
			puts("VAB certificate process failed\n");
			return -ENOEXEC;
		}
	}

	printf("%s 0x%016llx (%ld bytes)\n",
	       "Image Authentication passed at address", img_addr, img_sz);

	return 0;
}