vtls: added support for mbedTLS

closes #496

11 files changed, 950 insertions, 9 deletions

diff --git a/configure.ac b/configure.ac
index 3bab4a55d..e78270a40 100644
--- a/configure.ac
+++ b/configure.ac
@@ -149,7 +149,7 @@ AC_SUBST(PKGADD_VENDOR)
 
 dnl
 dnl initialize all the info variables
-    curl_ssl_msg="no      (--with-{ssl,gnutls,nss,polarssl,cyassl,axtls,winssl,darwinssl} )"
+    curl_ssl_msg="no      (--with-{ssl,gnutls,nss,polarssl,mbedtls,cyassl,axtls,winssl,darwinssl} )"
     curl_ssh_msg="no      (--with-libssh2)"
    curl_zlib_msg="no      (--with-zlib)"
     curl_gss_msg="no      (--with-gssapi)"
@@ -1977,6 +1977,93 @@ if test "$curl_ssl_msg" = "$init_ssl_msg"; then
 fi
 
 dnl ----------------------------------------------------
+dnl check for mbedTLS
+dnl ----------------------------------------------------
+
+OPT_MBEDTLS=no
+
+_cppflags=$CPPFLAGS
+_ldflags=$LDFLAGS
+AC_ARG_WITH(mbedtls,dnl
+AC_HELP_STRING([--with-mbedtls=PATH],[where to look for mbedTLS, PATH points to the installation root])
+AC_HELP_STRING([--without-mbedtls], [disable mbedTLS detection]),
+  OPT_MBEDTLS=$withval)
+
+if test "$curl_ssl_msg" = "$init_ssl_msg"; then
+
+  if test X"$OPT_MBEDTLS" != Xno; then
+
+    if test "$OPT_MBEDTLS" = "yes"; then
+      OPT_MBEDTLS=""
+    fi
+
+    if test -z "$OPT_MBEDTLS" ; then
+      dnl check for lib first without setting any new path
+
+      AC_CHECK_LIB(mbedtls, mbedtls_havege_init,
+      dnl libmbedtls found, set the variable
+       [
+         AC_DEFINE(USE_MBEDTLS, 1, [if mbedTLS is enabled])
+         AC_SUBST(USE_MBEDTLS, [1])
+         MBEDTLS_ENABLED=1
+         USE_MBEDTLS="yes"
+         curl_ssl_msg="enabled (mbedTLS)"
+        ], [], -lmbedx509 -lmbedcrypto)
+    fi
+
+    addld=""
+    addlib=""
+    addcflags=""
+    mbedtlslib=""
+
+    if test "x$USE_MBEDTLS" != "xyes"; then
+      dnl add the path and test again
+      addld=-L$OPT_MBEDTLS/lib$libsuff
+      addcflags=-I$OPT_MBEDTLS/include
+      mbedtlslib=$OPT_MBEDTLS/lib$libsuff
+
+      LDFLAGS="$LDFLAGS $addld"
+      if test "$addcflags" != "-I/usr/include"; then
+         CPPFLAGS="$CPPFLAGS $addcflags"
+      fi
+
+      AC_CHECK_LIB(mbedtls, mbedtls_ssl_init,
+       [
+       AC_DEFINE(USE_MBEDTLS, 1, [if mbedTLS is enabled])
+       AC_SUBST(USE_MBEDTLS, [1])
+       MBEDTLS_ENABLED=1
+       USE_MBEDTLS="yes"
+       curl_ssl_msg="enabled (mbedTLS)"
+       ],
+       [
+         CPPFLAGS=$_cppflags
+         LDFLAGS=$_ldflags
+       ], -lmbedx509 -lmbedcrypto)
+    fi
+
+    if test "x$USE_MBEDTLS" = "xyes"; then
+      AC_MSG_NOTICE([detected mbedTLS])
+
+      LIBS="-lmbedtls -lmbedx509 -lmbedcrypto $LIBS"
+
+      if test -n "$mbedtlslib"; then
+        dnl when shared libs were found in a path that the run-time
+        dnl linker doesn't search through, we need to add it to
+        dnl LD_LIBRARY_PATH to prevent further configure tests to fail
+        dnl due to this
+        if test "x$cross_compiling" != "xyes"; then
+          LD_LIBRARY_PATH="$LD_LIBRARY_PATH:$mbedtlslib"
+          export LD_LIBRARY_PATH
+          AC_MSG_NOTICE([Added $mbedtlslib to LD_LIBRARY_PATH])
+        fi
+      fi
+    fi
+
+  fi dnl mbedTLS not disabled
+
+fi
+
+dnl ----------------------------------------------------
 dnl check for CyaSSL
 dnl ----------------------------------------------------
 
@@ -2300,7 +2387,7 @@ if test "$curl_ssl_msg" = "$init_ssl_msg"; then
   fi
 fi
 
-if test "x$OPENSSL_ENABLED$GNUTLS_ENABLED$NSS_ENABLED$POLARSSL_ENABLED$AXTLS_ENABLED$CYASSL_ENABLED$WINSSL_ENABLED$DARWINSSL_ENABLED" = "x"; then
+if test "x$OPENSSL_ENABLED$GNUTLS_ENABLED$NSS_ENABLED$POLARSSL_ENABLED$MBEDTLS_ENABLED$AXTLS_ENABLED$CYASSL_ENABLED$WINSSL_ENABLED$DARWINSSL_ENABLED" = "x"; then
   AC_MSG_WARN([SSL disabled, you will not be able to use HTTPS, FTPS, NTLM and more.])
   AC_MSG_WARN([Use --with-ssl, --with-gnutls, --with-polarssl, --with-cyassl, --with-nss, --with-axtls, --with-winssl, or --with-darwinssl to address this.])
 else
diff --git a/docs/libcurl/symbols-in-versions b/docs/libcurl/symbols-in-versions
index 5a3068ec1..5f6d7e504 100644
--- a/docs/libcurl/symbols-in-versions
+++ b/docs/libcurl/symbols-in-versions
@@ -629,6 +629,7 @@ CURLSSLBACKEND_CYASSL           7.34.0
 CURLSSLBACKEND_DARWINSSL        7.34.0
 CURLSSLBACKEND_GNUTLS           7.34.0
 CURLSSLBACKEND_GSKIT            7.34.0
+CURLSSLBACKEND_MBEDTLS          7.46.0
 CURLSSLBACKEND_NONE             7.34.0
 CURLSSLBACKEND_NSS              7.34.0
 CURLSSLBACKEND_OPENSSL          7.34.0
diff --git a/include/curl/curl.h b/include/curl/curl.h
index 11d90f018..2d482750d 100644
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@@ -2076,7 +2076,8 @@ typedef enum {
   CURLSSLBACKEND_CYASSL = 7,
   CURLSSLBACKEND_SCHANNEL = 8,
   CURLSSLBACKEND_DARWINSSL = 9,
-  CURLSSLBACKEND_AXTLS = 10
+  CURLSSLBACKEND_AXTLS = 10,
+  CURLSSLBACKEND_MBEDTLS = 11
 } curl_sslbackend;
 
 /* Information about the SSL library used and the respective internal SSL
diff --git a/lib/Makefile.inc b/lib/Makefile.inc
index d444a6b21..74176f96f 100644
--- a/lib/Makefile.inc
+++ b/lib/Makefile.inc
@@ -22,11 +22,13 @@
 
 LIB_VTLS_CFILES = vtls/openssl.c vtls/gtls.c vtls/vtls.c vtls/nss.c     \
   vtls/polarssl.c vtls/polarssl_threadlock.c vtls/axtls.c               \
-  vtls/cyassl.c vtls/schannel.c vtls/darwinssl.c vtls/gskit.c
+  vtls/cyassl.c vtls/schannel.c vtls/darwinssl.c vtls/gskit.c           \
+  vtls/mbedtls.c
 
 LIB_VTLS_HFILES = vtls/openssl.h vtls/vtls.h vtls/gtls.h                \
   vtls/nssg.h vtls/polarssl.h vtls/polarssl_threadlock.h vtls/axtls.h   \
-  vtls/cyassl.h vtls/schannel.h vtls/darwinssl.h vtls/gskit.h
+  vtls/cyassl.h vtls/schannel.h vtls/darwinssl.h vtls/gskit.h           \
+  vtls/mbedtls.h
 
 LIB_CFILES = file.c timeval.c base64.c hostip.c progress.c formdata.c   \
   cookie.c http.c sendf.c ftp.c url.c dict.c if2ip.c speedcheck.c       \
diff --git a/lib/curl_setup.h b/lib/curl_setup.h
index a21b96196..827c506db 100644
--- a/lib/curl_setup.h
+++ b/lib/curl_setup.h
@@ -605,7 +605,7 @@ int netware_init(void);
 #define LIBIDN_REQUIRED_VERSION "0.4.1"
 
 #if defined(USE_GNUTLS) || defined(USE_OPENSSL) || defined(USE_NSS) || \
-    defined(USE_POLARSSL) || defined(USE_AXTLS) || \
+    defined(USE_POLARSSL) || defined(USE_AXTLS) || defined(USE_MBEDTLS) || \
     defined(USE_CYASSL) || defined(USE_SCHANNEL) || \
     defined(USE_DARWINSSL) || defined(USE_GSKIT)
 #define USE_SSL    /* SSL support has been enabled */
diff --git a/lib/http.c b/lib/http.c
index 59f6436fe..b652c2e8b 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -1394,7 +1394,8 @@ static CURLcode https_connecting(struct connectdata *conn, bool *done)
 #endif
 
 #if defined(USE_OPENSSL) || defined(USE_GNUTLS) || defined(USE_SCHANNEL) || \
-    defined(USE_DARWINSSL) || defined(USE_POLARSSL) || defined(USE_NSS)
+    defined(USE_DARWINSSL) || defined(USE_POLARSSL) || defined(USE_NSS) || \
+    defined(USE_MBEDTLS)
 /* This function is for OpenSSL, GnuTLS, darwinssl, schannel and polarssl only.
    It should be made to query the generic SSL layer instead. */
 static int https_getsock(struct connectdata *conn,
diff --git a/lib/urldata.h b/lib/urldata.h
index 66bcfbdf8..b467e503e 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -93,7 +93,15 @@
 #include <gnutls/gnutls.h>
 #endif
 
-#ifdef USE_POLARSSL
+#ifdef USE_MBEDTLS
+
+#include <mbedtls/ssl.h>
+#include <mbedtls/version.h>
+#include <mbedtls/entropy.h>
+#include <mbedtls/ctr_drbg.h>
+
+#elif defined USE_POLARSSL
+
 #include <polarssl/ssl.h>
 #include <polarssl/version.h>
 #if POLARSSL_VERSION_NUMBER<0x01010000
@@ -102,6 +110,7 @@
 #include <polarssl/entropy.h>
 #include <polarssl/ctr_drbg.h>
 #endif /* POLARSSL_VERSION_NUMBER<0x01010000 */
+
 #endif /* USE_POLARSSL */
 
 #ifdef USE_CYASSL
@@ -280,6 +289,19 @@ struct ssl_connect_data {
 #endif
   ssl_connect_state connecting_state;
 #endif /* USE_GNUTLS */
+#ifdef USE_MBEDTLS
+  mbedtls_ctr_drbg_context ctr_drbg;
+  mbedtls_entropy_context entropy;
+  mbedtls_ssl_context ssl;
+  mbedtls_ssl_session ssn;
+  int server_fd;
+  mbedtls_x509_crt cacert;
+  mbedtls_x509_crt clicert;
+  mbedtls_x509_crl crl;
+  mbedtls_pk_context pk;
+  ssl_connect_state connecting_state;
+  mbedtls_ssl_config config;
+#endif /* USE_MBEDTLS */
 #ifdef USE_POLARSSL
   ctr_drbg_context ctr_drbg;
   entropy_context entropy;
diff --git a/lib/vtls/mbedtls.c b/lib/vtls/mbedtls.c
new file mode 100644
index 000000000..b7d84cac6
--- /dev/null
+++ b/lib/vtls/mbedtls.c
@@ -0,0 +1,753 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2010 - 2011, Hoi-Ho Chan, <hoiho.chan@gmail.com>
+ * Copyright (C) 2012 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+/*
+ * Source file for all mbedTSL-specific code for the TLS/SSL layer. No code
+ * but vtls.c should ever call or use these functions.
+ *
+ */
+
+#include "curl_setup.h"
+
+#ifdef USE_MBEDTLS
+
+#include <mbedtls/net.h>
+#include <mbedtls/ssl.h>
+#include <mbedtls/certs.h>
+#include <mbedtls/x509.h>
+#include <mbedtls/version.h>
+
+#include <mbedtls/error.h>
+#include <mbedtls/entropy.h>
+#include <mbedtls/ctr_drbg.h>
+
+#include "urldata.h"
+#include "sendf.h"
+#include "inet_pton.h"
+#include "mbedtls.h"
+#include "vtls.h"
+#include "parsedate.h"
+#include "connect.h" /* for the connect timeout */
+#include "select.h"
+#include "rawstr.h"
+#include "polarssl_threadlock.h"
+
+#define _MPRINTF_REPLACE /* use our functions only */
+#include <curl/mprintf.h>
+#include "curl_memory.h"
+/* The last #include file should be: */
+#include "memdebug.h"
+
+/* apply threading? */
+#if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
+#define THREADING_SUPPORT
+#endif
+
+#if defined(THREADING_SUPPORT)
+static mbedtls_entropy_context entropy;
+
+static int  entropy_init_initialized  = 0;
+
+/* start of entropy_init_mutex() */
+static void entropy_init_mutex(mbedtls_entropy_context *ctx)
+{
+  /* lock 0 = entropy_init_mutex() */
+  polarsslthreadlock_lock_function(0);
+  if(entropy_init_initialized == 0) {
+    mbedtls_entropy_init(ctx);
+    entropy_init_initialized = 1;
+  }
+  polarsslthreadlock_unlock_function(0);
+}
+/* end of entropy_init_mutex() */
+
+/* start of entropy_func_mutex() */
+static int entropy_func_mutex(void *data, unsigned char *output, size_t len)
+{
+  int ret;
+  /* lock 1 = entropy_func_mutex() */
+  polarsslthreadlock_lock_function(1);
+  ret = mbedtls_entropy_func(data, output, len);
+  polarsslthreadlock_unlock_function(1);
+
+  return ret;
+}
+/* end of entropy_func_mutex() */
+
+#endif /* THREADING_SUPPORT */
+
+/* Define this to enable lots of debugging for mbedTLS */
+#undef MBEDTLS_DEBUG
+
+#ifdef MBEDTLS_DEBUG
+static void mbedtls_debug(void *context, int level, const char *line)
+{
+  struct SessionHandle *data = NULL;
+
+  if(!context)
+    return;
+
+  data = (struct SessionHandle *)context;
+
+  infof(data, "%s", line);
+  (void) level;
+}
+#else
+#endif
+
+/* ALPN for http2? */
+#ifdef USE_NGHTTP2
+#  undef HAS_ALPN
+#  ifdef MBEDTLS_SSL_ALPN
+#    define HAS_ALPN
+#  endif
+#endif
+
+static Curl_recv mbedtls_recv;
+static Curl_send mbedtls_send;
+
+static CURLcode
+mbedtls_connect_step1(struct connectdata *conn,
+                     int sockindex)
+{
+  struct SessionHandle *data = conn->data;
+  struct ssl_connect_data* connssl = &conn->ssl[sockindex];
+
+  bool sni = TRUE; /* default is SNI enabled */
+  int ret = -1;
+#ifdef ENABLE_IPV6
+  struct in6_addr addr;
+#else
+  struct in_addr addr;
+#endif
+  void *old_session = NULL;
+  size_t old_session_size = 0;
+  char errorbuf[128];
+  errorbuf[0]=0;
+
+  /* mbedTLS only supports SSLv3 and TLSv1 */
+  if(data->set.ssl.version == CURL_SSLVERSION_SSLv2) {
+    failf(data, "mbedTLS does not support SSLv2");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+  else if(data->set.ssl.version == CURL_SSLVERSION_SSLv3)
+    sni = FALSE; /* SSLv3 has no SNI */
+
+#ifdef THREADING_SUPPORT
+  entropy_init_mutex(&entropy);
+
+  if((ret = mbedtls_ctr_drbg_init(&connssl->ctr_drbg, entropy_func_mutex,
+                                  &entropy, connssl->ssn.id,
+                                  connssl->ssn.length)) != 0) {
+#ifdef MBEDTLS_ERROR_C
+     mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
+#endif /* MBEDTLS_ERROR_C */
+     failf(data, "Failed - mbedTLS: ctr_drbg_init returned (-0x%04X) %s\n",
+                                                            -ret, errorbuf);
+  }
+#else
+  mbedtls_entropy_init(&connssl->entropy);
+  mbedtls_ctr_drbg_init(&connssl->ctr_drbg);
+
+  ret = mbedtls_ctr_drbg_seed(&connssl->ctr_drbg, mbedtls_entropy_func,
+                              &connssl->entropy, connssl->ssn.id,
+                              connssl->ssn.id_len);
+  if(ret) {
+#ifdef MBEDTLS_ERROR_C
+    mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
+#endif /* MBEDTLS_ERROR_C */
+    failf(data, "Failed - mbedTLS: ctr_drbg_init returned (-0x%04X) %s\n",
+          -ret, errorbuf);
+  }
+#endif /* THREADING_SUPPORT */
+
+  /* Load the trusted CA */
+  memset(&connssl->cacert, 0, sizeof(mbedtls_x509_crt));
+
+  if(data->set.str[STRING_SSL_CAFILE]) {
+    ret = mbedtls_x509_crt_parse_file(&connssl->cacert,
+                                      data->set.str[STRING_SSL_CAFILE]);
+
+    if(ret<0) {
+#ifdef MBEDTLS_ERROR_C
+      mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
+#endif /* MBEDTLS_ERROR_C */
+      failf(data, "Error reading ca cert file %s - mbedTLS: (-0x%04X) %s",
+            data->set.str[STRING_SSL_CAFILE], -ret, errorbuf);
+
+      if(data->set.ssl.verifypeer)
+        return CURLE_SSL_CACERT_BADFILE;
+    }
+  }
+
+  if(data->set.str[STRING_SSL_CAPATH]) {
+    ret = mbedtls_x509_crt_parse_path(&connssl->cacert,
+                                      data->set.str[STRING_SSL_CAPATH]);
+
+    if(ret<0) {
+#ifdef MBEDTLS_ERROR_C
+      mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
+#endif /* MBEDTLS_ERROR_C */
+      failf(data, "Error reading ca cert path %s - mbedTLS: (-0x%04X) %s",
+            data->set.str[STRING_SSL_CAPATH], -ret, errorbuf);
+
+      if(data->set.ssl.verifypeer)
+        return CURLE_SSL_CACERT_BADFILE;
+    }
+  }
+
+  /* Load the client certificate */
+  memset(&connssl->clicert, 0, sizeof(mbedtls_x509_crt));
+
+  if(data->set.str[STRING_CERT]) {
+    ret = mbedtls_x509_crt_parse_file(&connssl->clicert,
+                                      data->set.str[STRING_CERT]);
+
+    if(ret) {
+#ifdef MBEDTLS_ERROR_C
+      mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
+#endif /* MBEDTLS_ERROR_C */
+      failf(data, "Error reading client cert file %s - mbedTLS: (-0x%04X) %s",
+            data->set.str[STRING_CERT], -ret, errorbuf);
+
+      return CURLE_SSL_CERTPROBLEM;
+    }
+  }
+
+  /* Load the client private key */
+  if(data->set.str[STRING_KEY]) {
+    mbedtls_pk_init(&connssl->pk);
+    ret = mbedtls_pk_parse_keyfile(&connssl->pk, data->set.str[STRING_KEY],
+                                   data->set.str[STRING_KEY_PASSWD]);
+    if(ret == 0 && !mbedtls_pk_can_do(&connssl->pk, MBEDTLS_PK_RSA))
+      ret = MBEDTLS_ERR_PK_TYPE_MISMATCH;
+
+    if(ret) {
+#ifdef MBEDTLS_ERROR_C
+      mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
+#endif /* MBEDTLS_ERROR_C */
+      failf(data, "Error reading private key %s - mbedTLS: (-0x%04X) %s",
+            data->set.str[STRING_KEY], -ret, errorbuf);
+
+      return CURLE_SSL_CERTPROBLEM;
+    }
+  }
+
+  /* Load the CRL */
+  memset(&connssl->crl, 0, sizeof(mbedtls_x509_crl));
+
+  if(data->set.str[STRING_SSL_CRLFILE]) {
+    ret = mbedtls_x509_crl_parse_file(&connssl->crl,
+                              data->set.str[STRING_SSL_CRLFILE]);
+
+    if(ret) {
+#ifdef MBEDTLS_ERROR_C
+      mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
+#endif /* MBEDTLS_ERROR_C */
+      failf(data, "Error reading CRL file %s - mbedTLS: (-0x%04X) %s",
+            data->set.str[STRING_SSL_CRLFILE], -ret, errorbuf);
+
+      return CURLE_SSL_CRL_BADFILE;
+    }
+  }
+
+  infof(data, "mbedTLS: Connecting to %s:%d\n",
+        conn->host.name, conn->remote_port);
+
+
+  mbedtls_ssl_config_init(&connssl->config);
+
+  mbedtls_ssl_init(&connssl->ssl);
+  if(mbedtls_ssl_setup(&connssl->ssl, &connssl->config)) {
+    failf(data, "mbedTLS: ssl_init failed");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+  ret = mbedtls_ssl_config_defaults(&connssl->config,
+                                    MBEDTLS_SSL_IS_CLIENT,
+                                    MBEDTLS_SSL_TRANSPORT_STREAM,
+                                    MBEDTLS_SSL_PRESET_DEFAULT);
+  if(ret) {
+    failf(data, "mbedTLS: ssl_config failed");
+    return CURLE_SSL_CONNECT_ERROR;
+  }
+
+  switch(data->set.ssl.version) {
+  case CURL_SSLVERSION_SSLv3:
+    mbedtls_ssl_conf_min_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
+                                 MBEDTLS_SSL_MINOR_VERSION_0);
+    infof(data, "mbedTLS: Forced min. SSL Version to be SSLv3\n");
+    break;
+  case CURL_SSLVERSION_TLSv1_0:
+    mbedtls_ssl_conf_min_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
+                                 MBEDTLS_SSL_MINOR_VERSION_1);
+    infof(data, "mbedTLS: Forced min. SSL Version to be TLS 1.0\n");
+    break;
+  case CURL_SSLVERSION_TLSv1_1:
+    mbedtls_ssl_conf_min_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
+                                 MBEDTLS_SSL_MINOR_VERSION_2);
+    infof(data, "mbedTLS: Forced min. SSL Version to be TLS 1.1\n");
+    break;
+  case CURL_SSLVERSION_TLSv1_2:
+    mbedtls_ssl_conf_min_version(&connssl->config, MBEDTLS_SSL_MAJOR_VERSION_3,
+                                 MBEDTLS_SSL_MINOR_VERSION_3);
+    infof(data, "mbedTLS: Forced min. SSL Version to be TLS 1.2\n");
+    break;
+  }
+
+  mbedtls_ssl_conf_authmode(&connssl->config, MBEDTLS_SSL_VERIFY_OPTIONAL);
+
+  mbedtls_ssl_conf_rng(&connssl->config, mbedtls_ctr_drbg_random,
+              &connssl->ctr_drbg);
+  mbedtls_ssl_set_bio(&connssl->ssl, &conn->sock[sockindex],
+              mbedtls_net_send,
+              mbedtls_net_recv,
+              NULL /*  rev_timeout() */);
+
+  mbedtls_ssl_conf_ciphersuites(&connssl->config,
+                                mbedtls_ssl_list_ciphersuites());
+  if(!Curl_ssl_getsessionid(conn, &old_session, &old_session_size)) {
+    memcpy(&connssl->ssn, old_session, old_session_size);
+    infof(data, "mbedTLS re-using session\n");
+  }
+
+  mbedtls_ssl_set_session(&connssl->ssl,
+                  &connssl->ssn);
+
+  mbedtls_ssl_conf_ca_chain(&connssl->config,
+                   &connssl->cacert,
+                   &connssl->crl);
+
+  if(data->set.str[STRING_KEY]) {
+    mbedtls_ssl_conf_own_cert(&connssl->config,
+                         &connssl->clicert, &connssl->pk);
+  }
+  if(!Curl_inet_pton(AF_INET, conn->host.name, &addr) &&
+#ifdef ENABLE_IPV6
+     !Curl_inet_pton(AF_INET6, conn->host.name, &addr) &&
+#endif
+     sni && mbedtls_ssl_set_hostname(&connssl->ssl, conn->host.name)) {
+     infof(data, "WARNING: failed to configure "
+                 "server name indication (SNI) TLS extension\n");
+  }
+
+#ifdef HAS_ALPN
+  if(data->set.httpversion == CURL_HTTP_VERSION_2_0) {
+    if(data->set.ssl_enable_alpn) {
+      static const char* protocols[] = {
+        NGHTTP2_PROTO_VERSION_ID, ALPN_HTTP_1_1, NULL
+      };
+      mbedtls_ssl_conf_alpn_protocols(&connssl->config, protocols);
+      infof(data, "ALPN, offering %s, %s\n", protocols[0],
+            protocols[1]);
+    }
+  }
+#endif
+
+#ifdef MBEDTLS_DEBUG
+  mbedtls_ssl_conf_dbg(&connssl->ssl, mbedtls_debug, data);
+#endif
+
+  connssl->connecting_state = ssl_connect_2;
+
+  return CURLE_OK;
+}
+
+static CURLcode
+mbedtls_connect_step2(struct connectdata *conn,
+                     int sockindex)
+{
+  int ret;
+  struct SessionHandle *data = conn->data;
+  struct ssl_connect_data* connssl = &conn->ssl[sockindex];
+  char buffer[1024];
+
+#ifdef HAS_ALPN
+  const char* next_protocol;
+#endif
+
+  char errorbuf[128];
+  errorbuf[0] = 0;
+
+  conn->recv[sockindex] = mbedtls_recv;
+  conn->send[sockindex] = mbedtls_send;
+
+  for(;;) {
+    if(!(ret = mbedtls_ssl_handshake(&connssl->ssl)))
+      break;
+    else if(ret != MBEDTLS_ERR_SSL_WANT_READ &&
+            ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
+#ifdef MBEDTLS_ERROR_C
+     mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
+#endif /* MBEDTLS_ERROR_C */
+     failf(data, "ssl_handshake returned - mbedTLS: (-0x%04X) %s",
+                                                    -ret, errorbuf);
+
+     return CURLE_SSL_CONNECT_ERROR;
+    }
+    else {
+      if(ret == MBEDTLS_ERR_SSL_WANT_READ) {
+        connssl->connecting_state = ssl_connect_2_reading;
+        return CURLE_OK;
+      }
+      if(ret == MBEDTLS_ERR_SSL_WANT_WRITE) {
+        connssl->connecting_state = ssl_connect_2_writing;
+        return CURLE_OK;
+      }
+      failf(data, "SSL_connect failed with error %d.", ret);
+      return CURLE_SSL_CONNECT_ERROR;
+
+    }
+  }
+
+  infof(data, "mbedTLS: Handshake complete, cipher is %s\n",
+        mbedtls_ssl_get_ciphersuite(&conn->ssl[sockindex].ssl)
+    );
+
+  ret = mbedtls_ssl_get_verify_result(&conn->ssl[sockindex].ssl);
+
+  if(ret && data->set.ssl.verifypeer) {
+    if(ret & MBEDTLS_X509_BADCERT_EXPIRED)
+      failf(data, "Cert verify failed: BADCERT_EXPIRED");
+
+    if(ret & MBEDTLS_X509_BADCERT_REVOKED) {
+      failf(data, "Cert verify failed: BADCERT_REVOKED");
+      return CURLE_SSL_CACERT;
+    }
+
+    if(ret & MBEDTLS_X509_BADCERT_CN_MISMATCH)
+      failf(data, "Cert verify failed: BADCERT_CN_MISMATCH");
+
+    if(ret & MBEDTLS_X509_BADCERT_NOT_TRUSTED)
+      failf(data, "Cert verify failed: BADCERT_NOT_TRUSTED");
+
+    return CURLE_PEER_FAILED_VERIFICATION;
+  }
+
+  if(mbedtls_ssl_get_peer_cert(&(connssl->ssl))) {
+    /* If the session was resumed, there will be no peer certs */
+    memset(buffer, 0, sizeof(buffer));
+
+    if(mbedtls_x509_crt_info(buffer, sizeof(buffer), (char *)"* ",
+                     mbedtls_ssl_get_peer_cert(&(connssl->ssl))) != -1)
+      infof(data, "Dumping cert info:\n%s\n", buffer);
+  }
+
+#ifdef HAS_ALPN
+  if(data->set.ssl_enable_alpn) {
+    next_protocol = mbedtls_ssl_get_alpn_protocol(&connssl->ssl);
+
+    if(next_protocol != NULL) {
+      infof(data, "ALPN, server accepted to use %s\n", next_protocol);
+
+      if(strncmp(next_protocol, NGHTTP2_PROTO_VERSION_ID,
+                  NGHTTP2_PROTO_VERSION_ID_LEN)) {
+        conn->negnpn = CURL_HTTP_VERSION_2_0;
+      }
+      else if(strncmp(next_protocol, ALPN_HTTP_1_1, ALPN_HTTP_1_1_LENGTH)) {
+        conn->negnpn = CURL_HTTP_VERSION_1_1;
+      }
+    }
+    else {
+      infof(data, "ALPN, server did not agree to a protocol\n");
+    }
+  }
+#endif
+
+  connssl->connecting_state = ssl_connect_3;
+  infof(data, "SSL connected\n");
+
+  return CURLE_OK;
+}
+
+static CURLcode
+mbedtls_connect_step3(struct connectdata *conn,
+                     int sockindex)
+{
+  CURLcode retcode = CURLE_OK;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  struct SessionHandle *data = conn->data;
+  void *old_ssl_sessionid = NULL;
+  mbedtls_ssl_session *our_ssl_sessionid = &conn->ssl[sockindex].ssn;
+  int incache;
+
+  DEBUGASSERT(ssl_connect_3 == connssl->connecting_state);
+
+  /* Save the current session data for possible re-use */
+  incache = !(Curl_ssl_getsessionid(conn, &old_ssl_sessionid, NULL));
+  if(incache) {
+    if(old_ssl_sessionid != our_ssl_sessionid) {
+      infof(data, "old SSL session ID is stale, removing\n");
+      Curl_ssl_delsessionid(conn, old_ssl_sessionid);
+      incache = FALSE;
+    }
+  }
+  if(!incache) {
+    void *new_session = malloc(sizeof(mbedtls_ssl_session));
+
+    if(new_session) {
+      memcpy(new_session, our_ssl_sessionid,
+             sizeof(mbedtls_ssl_session));
+
+      retcode = Curl_ssl_addsessionid(conn, new_session,
+                                   sizeof(mbedtls_ssl_session));
+    }
+    else {
+      retcode = CURLE_OUT_OF_MEMORY;
+    }
+
+    if(retcode) {
+      failf(data, "failed to store ssl session");
+      return retcode;
+    }
+  }
+
+  connssl->connecting_state = ssl_connect_done;
+
+  return CURLE_OK;
+}
+
+static ssize_t mbedtls_send(struct connectdata *conn,
+                             int sockindex,
+                             const void *mem,
+                             size_t len,
+                             CURLcode *curlcode)
+{
+  int ret = -1;
+
+  ret = mbedtls_ssl_write(&conn->ssl[sockindex].ssl,
+                  (unsigned char *)mem, len);
+
+  if(ret < 0) {
+    *curlcode = (ret == MBEDTLS_ERR_SSL_WANT_WRITE) ?
+      CURLE_AGAIN : CURLE_SEND_ERROR;
+    ret = -1;
+  }
+
+  return ret;
+}
+
+void Curl_mbedtls_close_all(struct SessionHandle *data)
+{
+  (void)data;
+}
+
+void Curl_mbedtls_close(struct connectdata *conn, int sockindex)
+{
+  /* mbedtls_rsa_free(&conn->ssl[sockindex].rsa); */
+  mbedtls_x509_crt_free(&conn->ssl[sockindex].clicert);
+  mbedtls_x509_crt_free(&conn->ssl[sockindex].cacert);
+  mbedtls_x509_crl_free(&conn->ssl[sockindex].crl);
+  mbedtls_ssl_free(&conn->ssl[sockindex].ssl);
+}
+
+static ssize_t mbedtls_recv(struct connectdata *conn,
+                             int num,
+                             char *buf,
+                             size_t buffersize,
+                             CURLcode *curlcode)
+{
+  int ret = -1;
+  ssize_t len = -1;
+
+  memset(buf, 0, buffersize);
+  ret = mbedtls_ssl_read(&conn->ssl[num].ssl, (unsigned char *)buf,
+                         buffersize);
+
+  if(ret <= 0) {
+    if(ret == MBEDTLS_ERR_SSL_PEER_CLOSE_NOTIFY)
+      return 0;
+
+    *curlcode = (ret == MBEDTLS_ERR_SSL_WANT_READ) ?
+      CURLE_AGAIN : CURLE_RECV_ERROR;
+    return -1;
+  }
+
+  len = ret;
+
+  return len;
+}
+
+void Curl_mbedtls_session_free(void *ptr)
+{
+  free(ptr);
+}
+
+size_t Curl_mbedtls_version(char *buffer, size_t size)
+{
+  unsigned int version = mbedtls_version_get_number();
+  return snprintf(buffer, size, "mbedTLS/%d.%d.%d", version>>24,
+                  (version>>16)&0xff, (version>>8)&0xff);
+}
+
+static CURLcode
+mbedtls_connect_common(struct connectdata *conn,
+                        int sockindex,
+                        bool nonblocking,
+                        bool *done)
+{
+  CURLcode retcode;
+  struct SessionHandle *data = conn->data;
+  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
+  curl_socket_t sockfd = conn->sock[sockindex];
+  long timeout_ms;
+  int what;
+
+  /* check if the connection has already been established */
+  if(ssl_connection_complete == connssl->state) {
+    *done = TRUE;
+    return CURLE_OK;
+  }
+
+  if(ssl_connect_1==connssl->connecting_state) {
+    /* Find out how much more time we're allowed */
+    timeout_ms = Curl_timeleft(data, NULL, TRUE);
+
+    if(timeout_ms < 0) {
+      /* no need to continue if time already is up */
+      failf(data, "SSL connection timeout");
+      return CURLE_OPERATION_TIMEDOUT;
+    }
+    retcode = mbedtls_connect_step1(conn, sockindex);
+    if(retcode)
+      return retcode;
+  }
+
+  while(ssl_connect_2 == connssl->connecting_state ||
+        ssl_connect_2_reading == connssl->connecting_state ||
+        ssl_connect_2_writing == connssl->connecting_state) {
+
+    /* check allowed time left */
+    timeout_ms = Curl_timeleft(data, NULL, TRUE);
+
+    if(timeout_ms < 0) {
+      /* no need to continue if time already is up */
+      failf(data, "SSL connection timeout");
+      return CURLE_OPERATION_TIMEDOUT;
+    }
+
+    /* if ssl is expecting something, check if it's available. */
+    if(connssl->connecting_state == ssl_connect_2_reading
+       || connssl->connecting_state == ssl_connect_2_writing) {
+
+      curl_socket_t writefd = ssl_connect_2_writing==
+        connssl->connecting_state?sockfd:CURL_SOCKET_BAD;
+      curl_socket_t readfd = ssl_connect_2_reading==
+        connssl->connecting_state?sockfd:CURL_SOCKET_BAD;
+
+      what = Curl_socket_ready(readfd, writefd, nonblocking ? 0 : timeout_ms);
+      if(what < 0) {
+        /* fatal error */
+        failf(data, "select/poll on SSL socket, errno: %d", SOCKERRNO);
+        return CURLE_SSL_CONNECT_ERROR;
+      }
+      else if(0 == what) {
+        if(nonblocking) {
+          *done = FALSE;
+          return CURLE_OK;
+        }
+        else {
+          /* timeout */
+          failf(data, "SSL connection timeout");
+          return CURLE_OPERATION_TIMEDOUT;
+        }
+      }
+      /* socket is readable or writable */
+    }
+
+    /* Run transaction, and return to the caller if it failed or if
+     * this connection is part of a multi handle and this loop would
+     * execute again. This permits the owner of a multi handle to
+     * abort a connection attempt before step2 has completed while
+     * ensuring that a client using select() or epoll() will always
+     * have a valid fdset to wait on.
+     */
+    retcode = mbedtls_connect_step2(conn, sockindex);
+    if(retcode || (nonblocking &&
+                   (ssl_connect_2 == connssl->connecting_state ||
+                    ssl_connect_2_reading == connssl->connecting_state ||
+                    ssl_connect_2_writing == connssl->connecting_state)))
+      return retcode;
+
+  } /* repeat step2 until all transactions are done. */
+
+  if(ssl_connect_3==connssl->connecting_state) {
+    retcode = mbedtls_connect_step3(conn, sockindex);
+    if(retcode)
+      return retcode;
+  }
+
+  if(ssl_connect_done==connssl->connecting_state) {
+    connssl->state = ssl_connection_complete;
+    conn->recv[sockindex] = mbedtls_recv;
+    conn->send[sockindex] = mbedtls_send;
+    *done = TRUE;
+  }
+  else
+    *done = FALSE;
+
+  /* Reset our connect state machine */
+  connssl->connecting_state = ssl_connect_1;
+
+  return CURLE_OK;
+}
+
+CURLcode
+Curl_mbedtls_connect_nonblocking(struct connectdata *conn,
+                                int sockindex,
+                                bool *done)
+{
+  return mbedtls_connect_common(conn, sockindex, TRUE, done);
+}
+
+
+CURLcode
+Curl_mbedtls_connect(struct connectdata *conn,
+                    int sockindex)
+{
+  CURLcode retcode;
+  bool done = FALSE;
+
+  retcode = mbedtls_connect_common(conn, sockindex, FALSE, &done);
+  if(retcode)
+    return retcode;
+
+  DEBUGASSERT(done);
+
+  return CURLE_OK;
+}
+
+/*
+ * return 0 error initializing SSL
+ * return 1 SSL initialized successfully
+ */
+int mbedtls_init(void)
+{
+  return polarsslthreadlock_thread_setup();
+}
+
+void mbedtls_cleanup(void)
+{
+  (void)polarsslthreadlock_thread_cleanup();
+}
+
+#endif /* USE_MBEDTLS */
diff --git a/lib/vtls/mbedtls.h b/lib/vtls/mbedtls.h
new file mode 100644
index 000000000..b930c1000
--- /dev/null
+++ b/lib/vtls/mbedtls.h
@@ -0,0 +1,73 @@
+#ifndef HEADER_CURL_MBEDTLS_H
+#define HEADER_CURL_MBEDTLS_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2010, Hoi-Ho Chan, <hoiho.chan@gmail.com>
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "curl_setup.h"
+
+#ifdef USE_MBEDTLS
+
+/* Called on first use mbedTLS, setup threading if supported */
+int  mbedtls_init(void);
+void mbedtls_cleanup(void);
+
+
+CURLcode Curl_mbedtls_connect(struct connectdata *conn, int sockindex);
+
+CURLcode Curl_mbedtls_connect_nonblocking(struct connectdata *conn,
+                                           int sockindex,
+                                           bool *done);
+
+/* tell mbedTLS to close down all open information regarding connections (and
+   thus session ID caching etc) */
+void Curl_mbedtls_close_all(struct SessionHandle *data);
+
+ /* close a SSL connection */
+void Curl_mbedtls_close(struct connectdata *conn, int sockindex);
+
+void Curl_mbedtls_session_free(void *ptr);
+size_t Curl_mbedtls_version(char *buffer, size_t size);
+int Curl_mbedtls_shutdown(struct connectdata *conn, int sockindex);
+
+/* API setup for mbedTLS */
+#define curlssl_init() mbedtls_init()
+#define curlssl_cleanup() mbedtls_cleanup()
+#define curlssl_connect Curl_mbedtls_connect
+#define curlssl_connect_nonblocking Curl_mbedtls_connect_nonblocking
+#define curlssl_session_free(x)  Curl_mbedtls_session_free(x)
+#define curlssl_close_all Curl_mbedtls_close_all
+#define curlssl_close Curl_mbedtls_close
+#define curlssl_shutdown(x,y) 0
+#define curlssl_set_engine(x,y) (x=x, y=y, CURLE_NOT_BUILT_IN)
+#define curlssl_set_engine_default(x) (x=x, CURLE_NOT_BUILT_IN)
+#define curlssl_engines_list(x) (x=x, (struct curl_slist *)NULL)
+#define curlssl_version Curl_mbedtls_version
+#define curlssl_check_cxn(x) (x=x, -1)
+#define curlssl_data_pending(x,y) (x=x, y=y, 0)
+#define CURL_SSL_BACKEND CURLSSLBACKEND_MBEDTLS
+
+/* This might cause libcurl to use a weeker random!
+   TODO: implement proper use of Polarssl's CTR-DRBG or HMAC-DRBG and use that
+*/
+#define curlssl_random(x,y,z) (x=x, y=y, z=z, CURLE_NOT_BUILT_IN)
+
+#endif /* USE_MBEDTLS */
+#endif /* HEADER_CURL_MBEDTLS_H */
diff --git a/lib/vtls/polarssl_threadlock.h b/lib/vtls/polarssl_threadlock.h
index b67b3f9ab..461479911 100644
--- a/lib/vtls/polarssl_threadlock.h
+++ b/lib/vtls/polarssl_threadlock.h
@@ -24,7 +24,7 @@
  ***************************************************************************/
 #include "curl_setup.h"
 
-#ifdef USE_POLARSSL
+#if (defined USE_POLARSSL) || (defined USE_MBEDTLS)
 
 #if defined(USE_THREADS_POSIX)
 #  define POLARSSL_MUTEX_T       pthread_mutex_t
diff --git a/lib/vtls/vtls.h b/lib/vtls/vtls.h
index d6224903a..e3cd5142f 100644
--- a/lib/vtls/vtls.h
+++ b/lib/vtls/vtls.h
@@ -32,6 +32,7 @@
 #include "cyassl.h"         /* CyaSSL versions */
 #include "schannel.h"       /* Schannel SSPI version */
 #include "darwinssl.h"      /* SecureTransport (Darwin) version */
+#include "mbedtls.h"        /* mbedTLS versions */
 
 #ifndef MAX_PINNED_PUBKEY_SIZE
 #define MAX_PINNED_PUBKEY_SIZE 1048576 /* 1MB */