What is SECO API?

[minsiklee]

Hi,

I'm currently developing a secure boot solution for one of our customers using i.MX8DXL

why the SECO API (sc_seco_authenticate() api) inside the authenticate_os_container() api from the NXP Guide is called 3 times?

authenticate_os_container api code:

int authenticate_os_container(ulong addr)
{
	struct container_hdr *phdr;
	int i, ret = 0;
	int err;
	sc_rm_mr_t mr;
	sc_faddr_t start, end;
	u16 length;
	struct boot_img_t *img;
	unsigned long s, e;

	if (addr % 4) {
		puts("Error: Image's address is not 4 byte aligned\n");
		return -EINVAL;
	}
              .....
              .....

	err = sc_seco_authenticate(-1, SC_SECO_AUTH_CONTAINER,
				   SECO_LOCAL_SEC_SEC_SECURE_RAM_BASE);

	for (i = 0; i < phdr->num_images; i++) {
		img = (struct boot_img_t *)(addr +
					    sizeof(struct container_hdr) +
					    i * sizeof(struct boot_img_t));

		debug("img %d, dst 0x%x, src 0x%x, size 0x%x\n",
		      i, (uint32_t) img->dst, img->offset + addr, img->size);

		memcpy((void *)img->dst, (const void *)(img->offset + addr),
		       img->size);
                   ......
                   .....

err = sc_seco_authenticate(-1, SC_SECO_VERIFY_IMAGE,
					   (1 << i));
		if (err) {
			printf("Authenticate img %d failed, return %d\n",
			       i, err);
			ret = -EIO;
		}

exit:
	if (sc_seco_authenticate(-1, SC_SECO_REL_CONTAINER, 0) != SC_ERR_NONE)
		printf("Error: release container failed!\n");

	return ret;
}

What do the sc_seco_authenticate apis called 3 times authenticate the signed image?
(At each step, which part of the signed image is authenticated?)

1. sc_seco_authenticate(ipc, SC_SECO_AUTH_CONTAINER ) : Authenticate whether an image is a container or not?
2. sc_seco_authenticate(ipc, SC_SECO_VERIFY_IMAGE) : Hash value authentication of container internal image?
3. sc_seco_authenticate(ipc, SC_SECO_REL_CONTAINER) : ?

Regards,
Duncan