esp8266/compat

If you are using LWIP raw tcp mode and want to add SSL support below are the steps that can help you to achieve this with the help of axTLS.

First you have to include the lwipr_compat.h header.

#include "compat/lwipr_compat.h"

Then in the code block where you initialize the tcp raw connection you should call axl_init. Take a look at the example below:

lwip_init();

/* 
 * The line below should be added AFTER the lwip_init code
 * AND BEFORE the call to tcp_new()
 * The parameter value 10 specifies how many SSL connections are expected
 */ 
axl_init(10);

// .. some more code
tcp = tcp_new();
tcp_sent(tcp, staticOnSent);
tcp_recv(tcp, staticOnReceive);
tcp_err(tcp, staticOnError);
tcp_poll(tcp, staticOnPoll, 4);
// ... and even more code 
res = tcp_connect(tcp, &addr, port, staticOnConnected);

Now we should add in our staticOnConnected funciton code to create new ssl context and ssl object. In the example below the sslObj and sslContext are defined as global

// global definitions
SSL *sslObj = NULL;
SSLCTX* sslContext = NULL;

// and some more code...

err_t staticOnConnected(void *arg, struct tcp_pcb *tcp, err_t err)
{
	int clientfd = -1;
	uint32_t options = 0;

	if (tcp == NULL) {
		/* @TODO: Take care to handle error conditions */
		return -1;
	}

	clientfd = axl_append(tcp);
	if(clientfd == -1) {
		printf("Unable to add LWIP tcp -> clientfd mapping\n");
		return ERR_OK;
	}
	
	printf("Connected: ClientId: %d\n", clientfd);
#ifdef SSL_DEBUG
	options |= SSL_DISPLAY_STATES | SSL_DISPLAY_BYTES;
#endif	
	
	// if you want to verify the server certificate later you can also add the following option
	options |= SSL_SERVER_VERIFY_LATER
	
	sslContext = ssl_ctx_new(SSL_CONNECT_IN_PARTS | options, 1); // !!! SSL_CONNECT_IN_PARTS must be in the flags !!!
	sslObj = ssl_client_new(sslContext, clientfd, NULL, 0);

	return ERR_OK;
}

Once we are connected we can send and receive information. For the receiving part we can do the following

err_t staticOnReceive(void *arg, struct tcp_pcb *tcp, struct pbuf *p, err_t err)
{
	uint8_t *read_buf = NULL;
	int read_bytes = 0;

	printf("Err: %d\n", err);

	if(tcp == NULL || p == NULL) {
		/* @TODO: Take care to handle error conditions */
		return -1;
	}

	read_bytes = axl_ssl_read(sslObj, &read_buf, tcp, p);
	if(read_bytes > 0) {
		printf("Got data: %s", read_buf);
		// @TODO: Do something useful with the read_buf 
	}

	return ERR_OK;
}

In the receiving part you can also add debug code to display more information about the SSL handshake, once it was successul.

err_t staticOnReceive(void *arg, struct tcp_pcb *tcp, struct pbuf *p, err_t err)
{
	static int show_info = 0;
	const char *common_name = NULL;
	
	// ..
	read_bytes = axl_ssl_read(sslObj, &read_buf, tcp, p);
	if(read_bytes > 0) {
		printf("Got data: %s", read_buf);
		// @TODO: Do something useful with the read_buf 
	}
	
	if(!show_info && ssl_handshake_status(sslObj) == SSL_OK) {
		common_name = ssl_get_cert_dn(sslObj, SSL_X509_CERT_COMMON_NAME);
		if (common_name) {
			printf("Common Name:\t\t\t%s\n", common_name);
		}

		// These two funcitons below can be found in the axtls examples
		display_session_id(sslObj); 
		display_cipher(sslObj);
		show_info = 1;
	}
	
	return ERR_OK;
}

And for the sending part we can use the following code sample as a start

void someSendingfunction() {
	uint8_t *out_buf;
	int out_bytes = 0;
	
	// ... take care to store something in the out_buf
	
	axl_ssl_write(sslObj, out_buf, out_bytes);
}

Good luck and send your success stories at slaff@attachix.com.