What is the main purpose of openssl's SSL_CTX_use_certificate_file?

Question

The man page did not clearly specify this. But looking at openssl's apps implementations, SSL_CTX_use_PrivateKey* calls are usually made after SSL_CTX_use_certificate_file succeeded. I assume this is mostly used at the server side.

I recently confused the above function with SSL_CTX_load_verify_locations wherein you could specify a CA certificate file and path. It turned out that SSL_CTX_load_verify_locations is the one I needed to verify a server certificate which is signed by a Trusted Authority.

Answer 1

SSL_CTX_use_certificate_file() is used to load the certificates into the CTX object either in PEM or DER format. The certificates can be chained ultimately ending at the root certificates. SSL_CTX_use_certificate_file API loads the first certificate into the CTX context;not the entire chain of certificates. If you prefer that thorough check of certificates is needed then you need to opt for SSL_CTX_use_certificate_chain_file()

http://publib.boulder.ibm.com/infocenter/tpfhelp/current/index.jsp?topic=/com.ibm.ztpf-ztpfdf.doc_put.cur/gtpc2/cpp_ssl_ctx_use_certificate_file.html