Parse DER x509 in C or C++

Question

I am writting a program in C/C++ on a linux plattofrm to parse X509. Most importantly right now is the public key but I might need other info as well. I have used the code (in Open SSL) from this post http://www.zedwood.com/article/c-openssl-parse-x509-certificate-pem and it works fine, but my certifcates are in DER format and I therefore need to convert them prior to this (which I can do in the command prompt). What I need is to do this conversion in code, or other code that does the same on DER certificate directly. I have tried to replace som components in the code to make it DER instad of PEM but no luck (have been trying to use some id2 commands but I am not even sure if that is correct). Any help would be apprectiated.

Answer 1

simply use d2i_X509_bio instead of PEM_read_bio_X509 to read the certificate. See how to convert the Certificate String into X509 structure.? and http://www.openssl.org/docs/crypto/d2i_X509.html