[PATCH v3 3/6] net: lwip: Add Support Server Name Indication support

[Ilias Apalodimas]

From: Javier Tia <javier.tia at linaro.org>

SNI, or Server Name Indication, is an addition to the TLS encryption
protocol that enables a client device to specify the domain name it is
trying to reach in the first step of the TLS handshake, preventing
common name mismatch errors and not reaching to HTTPS server that
enforce this condition. Since most of the websites require it nowadays
add support for it.

It's worth noting that this is already sent to lwIP [0]

[0] https://github.com/lwip-tcpip/lwip/pull/47

Signed-off-by: Javier Tia <javier.tia at linaro.org>
Reviewed-by: Jerome Forissier <jerome.forissier at linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---
 .../lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c    | 14 +++++++++-----
 lib/lwip/lwip/src/core/tcp_out.c                   |  2 +-
 lib/lwip/lwip/src/include/lwip/altcp_tls.h         |  2 +-
 3 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/lib/lwip/lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c b/lib/lwip/lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c
index ef19821b89e0..6643b05ee94d 100644
--- a/lib/lwip/lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c
+++ b/lib/lwip/lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c
@@ -3,7 +3,7 @@
  * Application layered TCP/TLS connection API (to be used from TCPIP thread)
  *
  * This file provides a TLS layer using mbedTLS
- *
+ * 
  * This version is currently compatible with the 2.x.x branch (current LTS).
  */
 
@@ -106,6 +106,7 @@ struct altcp_tls_config {
   u8_t pkey_count;
   u8_t pkey_max;
   mbedtls_x509_crt *ca;
+  char host[256];
 #if defined(MBEDTLS_SSL_CACHE_C) && ALTCP_MBEDTLS_USE_SESSION_CACHE
   /** Inter-connection cache for fast connection startup */
   struct mbedtls_ssl_cache_context cache;
@@ -642,6 +643,7 @@ altcp_mbedtls_setup(void *conf, struct altcp_pcb *conn, struct altcp_pcb *inner_
   /* tell mbedtls about our I/O functions */
   mbedtls_ssl_set_bio(&state->ssl_context, conn, altcp_mbedtls_bio_send, altcp_mbedtls_bio_recv, NULL);
 
+  mbedtls_ssl_set_hostname(&state->ssl_context, config->host);
   altcp_mbedtls_setup_callbacks(conn, inner_conn);
   conn->inner_conn = inner_conn;
   conn->fns = &altcp_mbedtls_functions;
@@ -951,7 +953,7 @@ altcp_tls_create_config_server_privkey_cert(const u8_t *privkey, size_t privkey_
 }
 
 static struct altcp_tls_config *
-altcp_tls_create_config_client_common(const u8_t *ca, size_t ca_len, int is_2wayauth)
+altcp_tls_create_config_client_common(const u8_t *ca, size_t ca_len, int is_2wayauth, char *host)
 {
   int ret;
   struct altcp_tls_config *conf = altcp_tls_create_config(0, (is_2wayauth) ? 1 : 0, (is_2wayauth) ? 1 : 0, ca != NULL);
@@ -973,13 +975,15 @@ altcp_tls_create_config_client_common(const u8_t *ca, size_t ca_len, int is_2way
 
     mbedtls_ssl_conf_ca_chain(&conf->conf, conf->ca, NULL);
   }
+  strlcpy(conf->host, host, sizeof(conf->host));
+
   return conf;
 }
 
 struct altcp_tls_config *
-altcp_tls_create_config_client(const u8_t *ca, size_t ca_len)
+altcp_tls_create_config_client(const u8_t *ca, size_t ca_len, char *host)
 {
-  return altcp_tls_create_config_client_common(ca, ca_len, 0);
+  return altcp_tls_create_config_client_common(ca, ca_len, 0, host);
 }
 
 struct altcp_tls_config *
@@ -995,7 +999,7 @@ altcp_tls_create_config_client_2wayauth(const u8_t *ca, size_t ca_len, const u8_
     return NULL;
   }
 
-  conf = altcp_tls_create_config_client_common(ca, ca_len, 1);
+  conf = altcp_tls_create_config_client_common(ca, ca_len, 1, NULL);
   if (conf == NULL) {
     return NULL;
   }
diff --git a/lib/lwip/lwip/src/core/tcp_out.c b/lib/lwip/lwip/src/core/tcp_out.c
index b5d312137368..6dbc5f96b60e 100644
--- a/lib/lwip/lwip/src/core/tcp_out.c
+++ b/lib/lwip/lwip/src/core/tcp_out.c
@@ -2028,7 +2028,7 @@ tcp_rst(const struct tcp_pcb *pcb, u32_t seqno, u32_t ackno,
         u16_t local_port, u16_t remote_port)
 {
   struct pbuf *p;
-
+  
   p = tcp_rst_common(pcb, seqno, ackno, local_ip, remote_ip, local_port, remote_port);
   if (p != NULL) {
     tcp_output_control_segment(pcb, p, local_ip, remote_ip);
diff --git a/lib/lwip/lwip/src/include/lwip/altcp_tls.h b/lib/lwip/lwip/src/include/lwip/altcp_tls.h
index fcb784d89d70..fb0618234481 100644
--- a/lib/lwip/lwip/src/include/lwip/altcp_tls.h
+++ b/lib/lwip/lwip/src/include/lwip/altcp_tls.h
@@ -92,7 +92,7 @@ struct altcp_tls_config *altcp_tls_create_config_server_privkey_cert(const u8_t
 /** @ingroup altcp_tls
  * Create an ALTCP_TLS client configuration handle
  */
-struct altcp_tls_config *altcp_tls_create_config_client(const u8_t *cert, size_t cert_len);
+struct altcp_tls_config *altcp_tls_create_config_client(const u8_t *cert, size_t cert_len, char *host);
 
 /** @ingroup altcp_tls
  * Create an ALTCP_TLS client configuration handle with two-way server/client authentication
-- 
2.43.0