Passing pointer to function causes segmentation fault when trying to retrieve value

Question

I am getting a segmentation fault with the following code. I am pretty sure it is because a function is trying to use the address of a variable instead of it's value. I am a bit new to pointers.

int main(int argc, char *argv[])
{

    EVP_PKEY        priv_key_p;
    X509_REQ        req_p;
    X509            cert;
    PKCS7           pkcs7;

        /*Need to store value in req_p and priv_key_p*/
    makecsr(&req_p, &priv_key_p, passphrase);

        /*Need to use value of req_p and priv_key_p*/
    create_cert(&req_p, &cert, &priv_key_p, passphrase);
}


int create_cert(X509_REQ *req_p, X509 *cert, EVP_PKEY *priv_key_p, char *passphrase)
{
    int i;
    long serial = 1;
    EVP_PKEY *pkey;
    const EVP_MD *digest;
    X509_NAME *name;
    X509V3_CTX ctx;

    /* verify signature on the request */
    if (!(pkey = X509_REQ_get_pubkey (req_p))) <--- Segmentation fault here!
        int_error ("Error getting public key from request");
    ....
}

Using GDB, after makecsr has executed, I can print the value of priv_key_p and req_p no problem.

However, inside the create_cert function, I can only print the value by writing p *priv_key_p / *req_p

Error

Program received signal SIGSEGV, Segmentation fault.
0xb7ebb747 in X509_REQ_get_pubkey ()
   from /lib/i386-linux-gnu/libcrypto.so.1.0.0

Answer 1

The error was because I was passing in a wrong pointer type for req_p into create_cert.

Solution was to change create_cert to this:

int create_cert(X509 *req_p, X509 **cert, EVP_PKEY **priv_key_p, char * passphrase)

Answer 2

your code:

if (!(pkey = X509_REQ_get_pubkey (req_p))) <--- Segementation fault here!
    int_error ("Error getting public key from request");
    ....

try this one:

if (!(pkey == X509_REQ_get_pubkey (req_p))) <--- Segementation fault here!
    int_error ("Error getting public key from request");
    ....