I was testing loading public key and failed.

At first, I create a private key and public key using openssl as follow.

$ openssl genrsa -out test-priv.pem 4096
$ openssl req -subj '/C=US/ST=Texas/L=Fort Worth/O=ABC Corporation, Inc./OU=Software/CN=abc_corp.com' -x509 -nodes -key test-priv.pem -out test-public.pem -days 365 -addext keyUsage=digitalSignature -addext extendedKeyUsage=codeSigning,emailProtection

The test code is as follow.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#include <openssl/pem.h>

EVP_PKEY *load_pubkey(const char *file)
{
   BIO *key = NULL;
   EVP_PKEY *pkey = NULL;

   if (file == NULL)
   {
      printf("no keyfile specifiedn");
      goto end;
   }

   key = BIO_new(BIO_s_file());
   if (key == NULL)
   {
      goto end;
   }

   if (BIO_read_filename(key, file) <= 0)
   {
      printf("Error opening : %sn", file);
      goto end;
   }

   pkey = PEM_read_bio_PUBKEY(key, NULL, NULL, NULL);

end:
   if (key != NULL)
      BIO_free(key);

   if (pkey == NULL)
      printf("Unable to load key filename : %sn", file);

   return (pkey);
}

int main(int argc, char *argv[])
{
   load_pubkey((const char *)argv[1]);
   return 0;
}

I compiled this test code like below.

$ gcc key_test.c -l ssl -l crypto -o key_test

Then run the program like below.

$ key_test test-public.pem

And the error message I got is “Unable to load key filename : test-public.pem”.
Do you see anything I did something wrong?