[PATCH 3/5] lwip: tls: warn when no CA exists amd log certificate validation errors

[Jerome Forissier]

Using HTTPS without root (CA) certificates is a security issue. Print a
warning in this case. Also, when certificate verification fail, print
an additional message because "HTTP client error 4" is not very
informative (4 is HTTPC_RESULT_ERR_CLOSED).

Signed-off-by: Jerome Forissier <jerome.forissier at linaro.org>
---
 lib/lwip/lwip/src/apps/altcp_tls/altcp_tls_mbedtls.c | 6 ++++++
 1 file changed, 6 insertions(+)

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 fa3d1d74fed..ef51a5ac168 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
@@ -298,6 +298,9 @@ altcp_mbedtls_lower_recv_process(struct altcp_pcb *conn, altcp_mbedtls_state_t *
     if (ret != 0) {
       LWIP_DEBUGF(ALTCP_MBEDTLS_DEBUG, ("mbedtls_ssl_handshake failed: %d\n", ret));
       /* handshake failed, connection has to be closed */
+      if (ret == MBEDTLS_ERR_X509_CERT_VERIFY_FAILED) {
+        printf("Certificate verification failed\n");
+      }
       if (conn->err) {
         conn->err(conn->arg, ERR_CLSD);
       }
@@ -841,6 +844,9 @@ altcp_tls_create_config(int is_server, u8_t cert_count, u8_t pkey_count, int hav
     altcp_mbedtls_free_config(conf);
     return NULL;
   }
+  if (authmode == MBEDTLS_SSL_VERIFY_NONE) {
+     printf("WARNING: no CA certificates, HTTPS connections not authenticated\n");
+  }
   mbedtls_ssl_conf_authmode(&conf->conf, authmode);
 
   mbedtls_ssl_conf_rng(&conf->conf, mbedtls_ctr_drbg_random, &altcp_tls_entropy_rng->ctr_drbg);
-- 
2.43.0