[PATCH RFC 01/10] common: Move host-only logic in image-sig.c to separate file

[Alex G.]

On 5/15/21 10:20 AM, Simon Glass wrote:
> Hi Alexandru,
> 
> On Fri, 14 May 2021 at 13:46, Alexandru Gagniuc <mr.nuke.me at gmail.com> wrote:
>>
>> image-sig.c is used to map a hash or crypto algorithm name to a
>> handler of that algorithm. There is some similarity between the host
>> and target variants, with the differences worked out by #ifdefs. The
>> purpose of this change is to remove those ifdefs.
>>
>> First, copy the file to a host-only version, and remove target
>> specific code. Although it looks like we are duplicating code,
>> subsequent patches will change the way target algorithms are searched.
>> Besides we are only duplicating three string to struct mapping
>> functions. This isn't something to fuss about.
>> ---
>>   common/image-sig-host.c | 134 ++++++++++++++++++++++++++++++++++++++++
>>   tools/Makefile          |   2 +-
>>   2 files changed, 135 insertions(+), 1 deletion(-)
>>   create mode 100644 common/image-sig-host.c
> 
> Will we never support signing in the board code? So far it is true,
> but I wonder if it will remain so, as things get more and more
> complicated. For example, we may want to sign the devicetree (somehow)
> after fix-ups. The current code structure makes it possible to add
> signing if needed. If we decided we wanted to sign on the board, how
> would we refactor things with this approach?

We'd have the logistics of keeping private keys available to firmware 
and only to firmware, but those are orthogonal to the problem. Assuming 
we implemented a device-side *_sign(), then we would add it to the 
linker list, via the proposed U_BOOT_CRYPTO_ALGO():


int rsa_device_side_sign(...)
{
	if (!CONFIG_IS_ENABLED(RSA_SIGN_ON_DEVICE))
		return -EIEIO;
	
	return do_rsa_device_side_sign(...);
}

  U_BOOT_CRYPTO_ALGO(rsa2048) = {
  	.name = "rsa2048",
  	.key_len = RSA2048_BYTES,
  	.verify = rsa_verify,
  	.sign = rsa_device_side_sign,
  };

> If this is host code, can we move it to tools/ ?

Definitely!