Add ALPN support

Author: torntrousers

Diff for: libraries/WiFiClientSecure/README.md

@@ -66,3 +66,18 @@ To use PSK:
   encryption for the connection
 
 Please see the WiFiClientPSK example.
+
+Specifying the ALPN Protocol
+----------------------------
+
+Application-Layer Protocol Negotiation (ALPN) is a Transport Layer Security (TLS) extension that allows 
+the application layer to negotiate which protocol should be performed over a secure connection in a manner 
+that avoids additional round trips and which is independent of the application-layer protocols.
+
+For example, this is used with AWS IoT Custom Authorizers where an MQTT client must set the ALPN protocol to ```mqtt```: 
+
+```
+const char *aws_protos[] = {"mqtt", NULL};
+...
+wiFiClient.setAlpnProtocols(aws_protos);
+```

Diff for: libraries/WiFiClientSecure/keywords.txt

@@ -29,6 +29,7 @@ connected	KEYWORD2
 setCACert	KEYWORD2
 setCertificate	KEYWORD2
 setPrivateKey	KEYWORD2
+setAlpnProtocols	KEYWORD2
 
 #######################################
 # Constants (LITERAL1)

Diff for: libraries/WiFiClientSecure/src/WiFiClientSecure.cpp

@@ -127,7 +127,7 @@ int WiFiClientSecure::connect(const char *host, uint16_t port, const char *CA_ce
     if(_timeout > 0){
         sslclient->handshake_timeout = _timeout;
     }
-    int ret = start_ssl_client(sslclient, host, port, _timeout, CA_cert, cert, private_key, NULL, NULL, _use_insecure);
+    int ret = start_ssl_client(sslclient, host, port, _timeout, CA_cert, cert, private_key, NULL, NULL, _use_insecure, _alpn_protos);
     _lastError = ret;
     if (ret < 0) {
         log_e("start_ssl_client: %d", ret);
@@ -147,7 +147,7 @@ int WiFiClientSecure::connect(const char *host, uint16_t port, const char *pskId
     if(_timeout > 0){
         sslclient->handshake_timeout = _timeout;
     }
-    int ret = start_ssl_client(sslclient, host, port, _timeout, NULL, NULL, NULL, pskIdent, psKey, _use_insecure);
+    int ret = start_ssl_client(sslclient, host, port, _timeout, NULL, NULL, NULL, pskIdent, psKey, _use_insecure, _alpn_protos);
     _lastError = ret;
     if (ret < 0) {
         log_e("start_ssl_client: %d", ret);
@@ -341,3 +341,8 @@ void WiFiClientSecure::setHandshakeTimeout(unsigned long handshake_timeout)
 {
     sslclient->handshake_timeout = handshake_timeout * 1000;
 }
+
+void WiFiClientSecure::setAlpnProtocols(const char **alpn_protos)
+{
+    _alpn_protos = alpn_protos;
+}

Diff for: libraries/WiFiClientSecure/src/WiFiClientSecure.h

@@ -39,6 +39,7 @@ class WiFiClientSecure : public WiFiClient
     const char *_private_key;
     const char *_pskIdent; // identity for PSK cipher suites
     const char *_psKey; // key in hex for PSK cipher suites
+    const char **_alpn_protos;
 
 public:
     WiFiClientSecure *next;
@@ -73,6 +74,7 @@ class WiFiClientSecure : public WiFiClient
     bool loadPrivateKey(Stream& stream, size_t size);
     bool verify(const char* fingerprint, const char* domain_name);
     void setHandshakeTimeout(unsigned long handshake_timeout);
+    void setAlpnProtocols(const char **alpn_protos);
 
     int setTimeout(uint32_t seconds){ return 0; }
 

Diff for: libraries/WiFiClientSecure/src/ssl_client.cpp

@@ -51,7 +51,7 @@ void ssl_init(sslclient_context *ssl_client)
 }
 
 
-int start_ssl_client(sslclient_context *ssl_client, const char *host, uint32_t port, int timeout, const char *rootCABuff, const char *cli_cert, const char *cli_key, const char *pskIdent, const char *psKey, bool insecure)
+int start_ssl_client(sslclient_context *ssl_client, const char *host, uint32_t port, int timeout, const char *rootCABuff, const char *cli_cert, const char *cli_key, const char *pskIdent, const char *psKey, bool insecure, const char **alpn_protos)
 {
     char buf[512];
     int ret, flags;
@@ -156,6 +156,13 @@ int start_ssl_client(sslclient_context *ssl_client, const char *host, uint32_t p
         return handle_error(ret);
     }
 
+    if (alpn_protos != NULL) {
+        log_v("Setting ALPN protocols");
+        if ((ret = mbedtls_ssl_conf_alpn_protocols(&ssl_client->ssl_conf, alpn_protos) ) != 0) {
+            return handle_error(ret);
+        }
+    }
+
     // MBEDTLS_SSL_VERIFY_REQUIRED if a CA certificate is defined on Arduino IDE and
     // MBEDTLS_SSL_VERIFY_NONE if not.
 

Diff for: libraries/WiFiClientSecure/src/ssl_client.h

@@ -29,7 +29,7 @@ typedef struct sslclient_context {
 
 
 void ssl_init(sslclient_context *ssl_client);
-int start_ssl_client(sslclient_context *ssl_client, const char *host, uint32_t port, int timeout, const char *rootCABuff, const char *cli_cert, const char *cli_key, const char *pskIdent, const char *psKey, bool insecure);
+int start_ssl_client(sslclient_context *ssl_client, const char *host, uint32_t port, int timeout, const char *rootCABuff, const char *cli_cert, const char *cli_key, const char *pskIdent, const char *psKey, bool insecure, const char **alpn_protos);
 void stop_ssl_socket(sslclient_context *ssl_client, const char *rootCABuff, const char *cli_cert, const char *cli_key);
 int data_to_read(sslclient_context *ssl_client);
 int send_ssl_data(sslclient_context *ssl_client, const uint8_t *data, size_t len);