Question

I recently wanted to build my own client-server system by using BSD sockets. After some point I wanted to include SSL to encrypt the data transfer. I followed this tutorial and the code compiles fine with Xcode (added linker flags: -lssl -lcrypto), but I keep getting EXC_BAD_ACCESS all the time once the program reaches the SSL_CTX_use_certificate_file() call. You can see the used code below.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <openssl/bio.h>
#include <openssl/ssl.h>
#include <openssl/err.h>

int main(int argc, const char * argv[])
{
    SSL_METHOD *method = NULL;
    SSL_CTX *ctx = NULL;
    OpenSSL_add_all_algorithms();
    SSL_load_error_strings();
    method = SSLv2_server_method();
    ctx = SSL_CTX_new(method);

    SSL_CTX_use_certificate_file(ctx, "/Users/steve/certificate.pem", SSL_FILETYPE_PEM);
    SSL_CTX_use_PrivateKey_file(ctx, "/Users/steve/key.pem", SSL_FILETYPE_PEM);

    printf("Hello, World!\n");
    return EXIT_SUCCESS;
}

If the program can’t find the certificate at the specified path it doesn’t crash but I wont have any SSL encryption of course. Could there be a problem with the certificate itself? I simply generated one with openssl by using the following commands:

# generate the key
$ openssl genrsa -out key.pem 1024

# generate request
$ openssl req -new -key key.pem -out request.pem
# fill in all the stuff ...

# generate certificate
$ openssl x509 -req -days 30 -in request.pem -signkey key.pem -out certificate.pem

Any idea?

Update: There actually are some warnings showing up when compiling with the OS X Deployment Target set to 10.7 or later, because all of this SSL stuff shows up as deprecated. Are there any recommended alternative practices to secure sockets with SSL?

Answer 1

The problem is that you need to call SSL_library_init, see the modification inside the code (It’s also a good practice to always handle errors from functions that we call :-):

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <openssl/bio.h>
#include <openssl/ssl.h>
#include <openssl/err.h>

int main(int argc, const char * argv[])
{
    //SSL_METHOD *method = NULL;
    SSL_CTX *ctx = NULL;
    OpenSSL_add_all_algorithms();
    SSL_load_error_strings();
    //method = SSLv2_server_method();
    //ctx = SSL_CTX_new(method);

    /* Without this line you got an error when calling SSL_CTX_new */
    SSL_library_init();
    ctx = SSL_CTX_new(SSLv2_server_method());
    if(!ctx) 
    {
        fprintf (stderr, "SSL_CTX_new ERROR\n");
        ERR_print_errors_fp(stderr);
        return EXIT_FAILURE;
    }

    if (!SSL_CTX_use_certificate_file(ctx, "/Users/steve/certificate.pem", SSL_FILETYPE_PEM))
    {
        fprintf (stderr, "SSL_CTX_use_certificate_file ERROR\n");
        ERR_print_errors_fp(stderr);

        return EXIT_FAILURE;
    }
    SSL_CTX_use_PrivateKey_file(ctx, "/Users/steve/key.pem", SSL_FILETYPE_PEM);

    printf("Hello, World!\n");
    return EXIT_SUCCESS;
}