Need publick key (RSA bits) from self signed certificate progmatically

Question

Hi,

I have created a self signed certificate for my web application using the openssl functions. In the browser when the certificate is viewed there is a field "Public Key" whose value is set to "RSA(2048)".

What are the openssl function calls present to retrieve this "public key" field of the certificate from my application ? For example , we have openssl function call X509_get_subject_name() to retrieve the value of "Subject" field from the self signed certificate.

I want to validate the certificate based on the "public key" value i.e if the value is changed to RSA(1024 or 512) (maybe changed by other application) , I want to display a warning.

Thanks,