> Would it be possible to add setter methods for 'sig_alg' and 'signature'?
New setter methods are probably needed. For now all you can do is
obtain the DER encoding of the X509_REQ_INFO, and creat from it the
DER encoding of the enclosing X509_REQ, by prepending a sequence
tag and length, and appending the signature OID, any parameters and
signature. You can then, if desired, recover an X509_REQ object