Add ability to set challenge password in mbedtls_x509write_csr

[yachoor]

Suggested enhancement

There's no way to set additional attributes in CSR, only extensions.
I need to generate CSR with challenge password (PKCS#9 OID 1.2.840.113549.1.9.7).
Right now I have custom serialization to DER to add that attribute, but all fields of mbedtls_x509write_csr are private in 3.0.

Justification

I need it for certificate enrollment/renewal using SCEP

[paul-elliott-arm]

Hi!

Seeing as you already have code to do this, if you were to submit your custom serialization as a PR to the library, then this field would not have to be public, and this is likely the fastest way this would get resolved., so I would definitely encourage you to do that.