doc/README.esbc_validate

SPDX-License-Identifier: GPL-2.0+
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 * (C) Copyright 2015
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esbc_validate command
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1. esbc_validate command is meant for validating header and
    signature of images (Boot Script and ESBC uboot client).
    SHA-256 and RSA operations are performed using SEC block in HW.
    This command works on both PBL based and Non PBL based Freescale
    platforms.
   Command usage:
    esbc_validate img_hdr_addr [pub_key_hash]
    esbc_validate hdr_addr <hash_val>
     Validates signature using RSA verification.
     $hdr_addr Address of header of the image to be validated.
     $hash_val -Optional. It provides Hash of public/srk key to be
       used to verify signature.

2. ESBC uboot client can be linux. Additionally, rootfs and device
    tree blob can also be signed.
3. In the event of header or signature failure in validation,
    ITS and ITF bits determine further course of action.
4. In case of soft failure, appropriate error is dumped on console.
5. In case of hard failure, SoC is issued RESET REQUEST after
    dumping error on the console.
6. KEY REVOCATION Feature:
    QorIQ platforms like B4/T4 have support of srk key table and key
    revocation in ISBC code in Silicon.
    The srk key table allows the user to have a key table with multiple
    keys and revoke any key in case of particular key gets compromised.
    In case the ISBC code uses the key revocation and srk key table to
    verify the u-boot code, the subsequent chain of trust should also
    use the same.
6. ISBC KEY EXTENSION Feature:
    This feature allows large number of keys to be used for esbc validation
    of images. A set of public keys is being signed and validated by ISBC
    which can be further used for esbc validation of images.