Simple CyaSSL Server Side Example

The three steps to using CyaSSL in a server side application

Introduction

The information on this page is nearly identical to that found on the Simple CyaSSL Client Side Example page. It is repeated here for consistency - with the differences highlighted where they exist.

Header files

#include "cyassl/ssl.h" The header file that must be included in all source files that use the CyaSSL library

Initialising the library and creating a CyaSSL context

Next, a variable of type CYASSL_CTX is required to store context information, and can be created using CyaSSL_CTX_new(). The SSL or TLS protocol to use is specified as the context is created using the function's parameter. Options include SSLv3, TLSv1, TLSv1.1, TLSv1.2, or DTLS. This example demonstrates the TLSv1 server protocol being selected (the client side example selects TLSv1 client). The values to use to select the other protocol options are listed in the user manual.

The client side example demonstrated a Certificate Authority (CA) file being loaded into the CyaSSL context. In addition to the CA, the server context must also be loaded with the server certificate, and a key file. This allows the server to send its certificate to the client for verification. CyaSSL_CTX_load_verify_locations() is called to load the CA, CyaSSL_CTX_use_certificate_file() to load the certificate, and CyaSSL_CTX_use_PrivateKey_file to load the private key file.

/* Define a structure to hold the CyaSSL context. */ CYASSL_CTX* xCyaSSL_Context; /* Initialise CyaSSL. This must be done before any other CyaSSL functions are called. */ CyaSSL_Init(); /* Attempt to create a context that uses the TLS V1 server protocol. */ xCyaSSL_Context = CyaSSL_CTX_new( CyaTLSv1_server_method() ); if( xCyaSSL_Context != NULL ) { /* Load the CA certificate. Real applications should ensure that CyaSSL_CTX_load_verify_locations() returns SSL_SUCCESS before proceeding. */ CyaSSL_CTX_load_verify_locations( xCyaSSL_Context, "ca-cert.pem", 0 ); /* Again, checking of the return values is omitted from this example, just for clarity. Real applications must ensure the following two functions return SSL_SUCCESS. */ CyaSSL_CTX_use_certificate_file( xCyaSSL_Context, "server-cert.pem", SSL_FILETYPE_PEM ); CyaSSL_CTX_use_PrivateKey_file( xCyaSSL_Context, "server-key.pem", SSL_FILETYPE_PEM ); } Library initialisation, protocol selection, and loading the CA certificate, server certificate and private key into the CyaSSL context.

Associating a CyaSSL object with a connected socket

CYASSL* xCyaSSL_Object; /* A connection has been accepted by the server. Create a CyaSSL object for use with the newly connected socket. */ xCyaSSL_Object = CyaSSL_new( xCyaSSL_Context ); if( xCyaSSL_Object != NULL ) { /* Associate the created CyaSSL object with the connected socket (sockfd). */ CyaSSL_set_fd( xCyaSSL_Object, sockfd ); } Creating a CyaSSL object, and associating it with an accepted connection

Using the socket

Note that the first parameter to both CyaSSL_write() and CyaSSL_read() is not the socket descriptor, but the CyaSSL object that is associated with the socket descriptor.

char ucTxBuf[ MAXLINE ], ucRxBuf[ MAXLINE ]; if( CyaSSL_write( xCyaSSL_Object, ucTxBuf, strlen( ucTxBuf ) ) != strlen( ucTxBuf ) ) { /* Send failed. */ } if( CyaSSL_read( xCyaSSL_Object, ucRxBuf, MAXLINE ) <= 0 ) { /* Read failed. */ } Writing to and reading from a socket using the CyaSSL API

Deleting allocated resources

/* CyaSSL objects should be deleted when they are no longer required. */ CyaSSL_free( xCyaSSL_Object ); /* The CyaSSL context should be deleted if it is no longer required. However, because most deeply embedded applications will keep the context for the lifetime of the application, and only ever be restarted when the system is rebooted, it might be that the context is never explicitly freed. */ CyaSSL_CTX_free( xCyaSSL_Context ); /* The library itself should be shut down cleanly if it too is no longer required. Again, because most deeply embedded applications will require the library for the lifetime of the application, and only ever be restarted when the system is rebooted, it might be that the library is never explicitly closed. */ CyaSSL_Cleanup(); Deleting objects that were dynamically allocated in this example