Re: Provider: cannot sign with ed25519-like key

On 12/08/2024 11:08, 'Bernd Ritter' via openssl-users wrote:
> I do not understand how the parameter list can change? As my debugging 
> logs are called, it seems that my get_params is called accordingly.
>

I don't really understand what you mean by this. Each invocation of your 
get_params function may request different parameters depending on which 
parameters the caller is interested in for any given context.

As I previously mentioned the "unknown max size" error comes from the 
EVP_PKEY_get_size() function, and this ultimately gets the size by 
querying the OSSL_PKEY_PARAM_MAX_SIZE parameter.

The value of this parameter is cached in the pkey. This happens here in 
OpenSSL:

https://github.com/openssl/openssl/blob/2f33265039cdbd0e4589c80970e02e208f3f94d2/crypto/evp/keymgmt_lib.c#L289-L313

This is the point in libcrypto where your provider is called and the 
OSSL_PKEY_PARAM_MAX_SIZE parameter is queried - the result of which is 
cached in the cache.size field of the pkey. All subsequent calls to 
`EVP_PEKY_get_size()` will refer to this cache and give the "unknown 
max_size" error if this cached size is <= 0.

If you are struggling to see how this fits together with what your code 
is doing then I suggest you build OpenSSL with debug symbols on and set 
a breakpoint in the `evp_keymgmt_util_cache_keyinfo` function I linked 
to above and step through what is happening in the interaction with your 
provider.

Matt

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