OpenSSL segfault - c++

Question

I have this simple program:
int main ()
{
/* INITIALIZING OPENSSL */
SSL_library_init();
SSL_load_error_strings();
ERR_load_BIO_strings();
OpenSSL_add_all_algorithms();
BIO *bio;
connectServerSSL(bio);
login(bio);
}
And this functions:
void connectServerSSL (BIO *bio)
{
SSL_CTX * ctx = SSL_CTX_new(SSLv23_client_method());
SSL * ssl;
if(! SSL_CTX_load_verify_locations(ctx, NULL, "/etc/ssl/certs"))
{
callError(ERR_LOADCERT);
}
bio = BIO_new_ssl_connect(ctx);
BIO_get_ssl(bio, &ssl);
SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
BIO_set_conn_hostname(bio, hostnamePort);
if(BIO_do_connect(bio) <= 0)
{
callError(ERR_CONNECTION);
}
if(SSL_get_verify_result(ssl) != X509_V_OK)
{
callError(ERR_VALIDCERT);
}
}
When I use this:
BIO_write(bio, request.c_str(), request.size())
In function connectServerSSL it works OK.
But when i want to use it in some other function:
void login (BIO *bio)
{
BIO_write(bio, request.c_str(), request.size());
}
I get Segmentation fault (core dumped).

Answer 1

In C and C++, even pointers are passed by value. So you need to either change the parameter of connectServerSSL to a BIO *& or else redefine it in the C-style of things:
void connectServerSSL (BIO ** bio_ptr)
{
SSL_CTX * ctx = SSL_CTX_new(SSLv23_client_method());
SSL * ssl;
if(! SSL_CTX_load_verify_locations(ctx, NULL, "/etc/ssl/certs"))
{
callError(ERR_LOADCERT);
}
BIO * bio = BIO_new_ssl_connect(ctx);
BIO_get_ssl(bio, &ssl);
SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY);
BIO_set_conn_hostname(bio, hostnamePort);
if(BIO_do_connect(bio) <= 0)
{
callError(ERR_CONNECTION);
}
if(SSL_get_verify_result(ssl) != X509_V_OK)
{
callError(ERR_VALIDCERT);
}
*bio_ptr = bio;
}
// Example usage:
void example()
{
BIO * bio;
connectServerSSL(&bio);
BIO_write(bio, request.c_str(), request.size());
}

Answer 2

Your connectServerSSL() function has a parameter named bio, and it writes only to this temporary variable, not to the bio variable in main(), which is uninitialized.
Change the signature of connectServerSSL() to BIO* connectServerSSL(void) and call it with bio = connectServerSSL(). You could also call the function with a BIO** newbio argument, call it with &bio, and set *newbio, which will update the bio variable in main().
Some good habits to help avoid bugs like this: initialize your variables to default values, use assertions to check that your inputs are valid, and single-step through in a debugger. If you’d initialized the variable in main() to BIO* bio = NULL, or better yet, BIO* const bio = connectServerSSL(), then it would have been obvious in the debugger that it was still uninitialized on return.