rpi-sign-bootcode: debug: Extract signature block fields

[timg236]

For test/debug and options to extract and parse the signature blocks.

Usage:
Take the signed pieeprom.bin from secure-boot-recovery5

rpi-eeprom-config -x pieeprom.bin
rpi-sign-bootcode -c 2712 -e bootcode.bin

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@tdewey-rpi @ghollingworth @mathewb64 - might be useful when debugging code signing issues on SB provisioner

$ rpi-eeprom-config -x pieeprom.bin
$ rpi-sign-bootcode -c 2712 -e bootcode.bin

(.venv) pi@tim-pi5-trixie:~/temp $ ../rpi-eeprom/tools/rpi-sign-bootcode -c 2712 -e bootcode.bin
sig_type: customer
length: 25984
keynum: 16
version: 0
rsa_sig: 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
pubkey_n: 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
pubkey_e: 0100010000000000
-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA+l3E+h/QNjrIR1cG6Npz
P0fBwp2UDpuQAafXDS5yryrfCPDYTO9DvzAfOk9Dz/putDfHV0RTOFXv1tmc4nqO
gU6nKx7tTdsjTiY4CgG3vXRMuAmDGX5ssJFCVmljGuILt1INlCmtun7Ow35VTxOc
RDDfrBDKnSitzOTf6KTR7xJhqFFhdMpIg8hW4bDBKMavyt38pRvDaO1o01qaQT/G
gAPmJm27y5RKNAe6iVTqsm4TMAhKC6P4XyRAbe6OMdFZyEWEk7Asexuc7uZlVHsU
I6pebSW/07O+5l/U7/3k6r//hO/HDFOBUUW55EjzzC1BhTlWHWfZNI+5+NdN8o32
3QIDAQAB
-----END PUBLIC KEY-----

sig_type: rpi
length: 25452
keynum: 0
version: 1
rsa_sig: 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
pubkey_n: 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
pubkey_e: 0100010000000000
-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEArl2m2S/qR1WrxRal/KXh
o+S1v3cJ48yG5sLzG9ffioVuM2EH6067veYNixTrzDlJIMZkKmlT9JAPL3yMPOXm
Tr8PmHg4TtEeu5zk2MSgmNKELCWZO9I3g7E9udcab14yInTEOHNU4qD31mJjzbga
Q77TjgXfdQ3iPFkMERF+6bMInniDCki7wIZzBE7Lp8fGh2d/5d0Qts9Yzj2tazqp
tnbAO1IQ5X4MNSvDP5QnRi1yjgbTXnDyWFOJZmpYhn0mAJuGWOntni7aqz+i/ITc
gwMPnWDxo7IlCevPA9X9aO4sOQPzVklHQj1hnovpBa4vYrZZ/WmTRj2MQFj0ShWu
9QIDAQAB
-----END PUBLIC KEY-----