For fun I thought I would see how hard it is to write an engine for OpenSSL. There are several existing ones that you can look at. I started by seeing how the opensc engine worked. This code shows the first step.
#include <stdio.h>
#include <string.h>
#include <openssl/crypto.h>
#include <openssl/objects.h>
#include <openssl/engine.h>
static int bind_fn(ENGINE * e, const char *id)
{
if (!ENGINE_set_id(e, "simple") ||
!ENGINE_set_name(e, "simple engine")) {
return 0;
} else {
return 1;
}
}
IMPLEMENT_DYNAMIC_CHECK_FN();
IMPLEMENT_DYNAMIC_BIND_FN(bind_fn);
Compile it like this
gcc -c -fpic simple_engine.c
gcc -shared -o simple_engine.so simple_engine.o
Make openssl.cnf look like this
openssl_conf = openssl_def
[openssl_def]
engines = engine_section
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