vquic: add support for GnuTLS backend of ngtcp2

Currently, the TLS backend used by vquic/ngtcp2.c is selected at compile
time. Therefore OpenSSL support needs to be explicitly disabled.

Signed-off-by: Daiki Ueno <dueno@redhat.com>
Closes #5148

4 files changed, 412 insertions, 28 deletions

diff --git a/configure.ac b/configure.ac
index 90a678ec8..889617ffa 100755
--- a/configure.ac
+++ b/configure.ac
@@ -3528,7 +3528,7 @@ if test X"$want_tcp2" != Xno; then
 
 fi
 
-if test "x$NGTCP2_ENABLED" = "x1"; then
+if test "x$NGTCP2_ENABLED" = "x1" -a "x$OPENSSL_ENABLED" = "x1"; then
   dnl backup the pre-ngtcp2_crypto_openssl variables
   CLEANLDFLAGS="$LDFLAGS"
   CLEANCPPFLAGS="$CPPFLAGS"
@@ -3583,6 +3583,61 @@ if test "x$NGTCP2_ENABLED" = "x1"; then
   fi
 fi
 
+if test "x$NGTCP2_ENABLED" = "x1" -a "x$GNUTLS_ENABLED" = "x1"; then
+  dnl backup the pre-ngtcp2_crypto_gnutls variables
+  CLEANLDFLAGS="$LDFLAGS"
+  CLEANCPPFLAGS="$CPPFLAGS"
+  CLEANLIBS="$LIBS"
+
+  CURL_CHECK_PKGCONFIG(libngtcp2_crypto_gnutls, $want_tcp2_path)
+
+  if test "$PKGCONFIG" != "no" ; then
+    LIB_NGTCP2_CRYPTO_GNUTLS=`CURL_EXPORT_PCDIR([$want_tcp2_path])
+      $PKGCONFIG --libs-only-l libngtcp2_crypto_gnutls`
+    AC_MSG_NOTICE([-l is $LIB_NGTCP2_CRYPTO_GNUTLS])
+
+    CPP_NGTCP2_CRYPTO_GNUTLS=`CURL_EXPORT_PCDIR([$want_tcp2_path]) dnl
+      $PKGCONFIG --cflags-only-I libngtcp2_crypto_gnutls`
+    AC_MSG_NOTICE([-I is $CPP_NGTCP2_CRYPTO_GNUTLS])
+
+    LD_NGTCP2_CRYPTO_GNUTLS=`CURL_EXPORT_PCDIR([$want_tcp2_path])
+      $PKGCONFIG --libs-only-L libngtcp2_crypto_gnutls`
+    AC_MSG_NOTICE([-L is $LD_NGTCP2_CRYPTO_GNUTLS])
+
+    LDFLAGS="$LDFLAGS $LD_NGTCP2_CRYPTO_GNUTLS"
+    CPPFLAGS="$CPPFLAGS $CPP_NGTCP2_CRYPTO_GNUTLS"
+    LIBS="$LIB_NGTCP2_CRYPTO_GNUTLS $LIBS"
+
+    if test "x$cross_compiling" != "xyes"; then
+      DIR_NGTCP2_CRYPTO_GNUTLS=`echo $LD_NGTCP2_CRYPTO_GNUTLS | $SED -e 's/-L//'`
+    fi
+    AC_CHECK_LIB(ngtcp2_crypto_gnutls, ngtcp2_crypto_ctx_initial,
+      [
+       AC_CHECK_HEADERS(ngtcp2/ngtcp2_crypto.h,
+          NGTCP2_ENABLED=1
+          AC_DEFINE(USE_NGTCP2_CRYPTO_GNUTLS, 1, [if ngtcp2_crypto_gnutls is in use])
+          AC_SUBST(USE_NGTCP2_CRYPTO_GNUTLS, [1])
+          CURL_LIBRARY_PATH="$CURL_LIBRARY_PATH:$DIR_NGTCP2_CRYPTO_GNUTLS"
+          export CURL_LIBRARY_PATH
+          AC_MSG_NOTICE([Added $DIR_NGTCP2_CRYPTO_GNUTLS to CURL_LIBRARY_PATH])
+       )
+      ],
+        dnl not found, revert back to clean variables
+        LDFLAGS=$CLEANLDFLAGS
+        CPPFLAGS=$CLEANCPPFLAGS
+        LIBS=$CLEANLIBS
+    )
+
+  else
+    dnl no ngtcp2_crypto_gnutls pkg-config found, deal with it
+    if test X"$want_tcp2" != Xdefault; then
+      dnl To avoid link errors, we do not allow --with-ngtcp2 without
+      dnl a pkgconfig file
+      AC_MSG_ERROR([--with-ngtcp2 was specified but could not find ngtcp2_crypto_gnutls pkg-config file.])
+    fi
+  fi
+fi
+
 dnl **********************************************************************
 dnl Check for nghttp3 (HTTP/3 with ngtcp2)
 dnl **********************************************************************
diff --git a/docs/HTTP3.md b/docs/HTTP3.md
index 55bdd0263..2769439d6 100644
--- a/docs/HTTP3.md
+++ b/docs/HTTP3.md
@@ -29,7 +29,7 @@ in the master branch using pull-requests, just like ordinary changes.
 
 # ngtcp2 version
 
-## Build
+## Build with OpenSSL
 
 Build (patched) OpenSSL
 
@@ -68,6 +68,46 @@ Build curl
      % LDFLAGS="-Wl,-rpath,<somewhere1>/lib" ./configure --with-ssl=<somewhere1> --with-nghttp3=<somewhere2> --with-ngtcp2=<somewhere3> --enable-alt-svc
      % make
 
+## Build with GnuTLS
+
+Build (patched) GnuTLS
+
+     % git clone --depth 1 -b tmp-quic https://gitlab.com/gnutls/gnutls.git
+     % cd gnutls
+     % ./bootstrap
+     % ./configure --disable-doc --prefix=<somewhere1>
+     % make
+     % make install
+
+Build nghttp3
+
+     % cd ..
+     % git clone https://github.com/ngtcp2/nghttp3
+     % cd nghttp3
+     % autoreconf -i
+     % ./configure --prefix=<somewhere2> --enable-lib-only
+     % make
+     % make install
+
+Build ngtcp2
+
+     % cd ..
+     % git clone https://github.com/ngtcp2/ngtcp2
+     % cd ngtcp2
+     % autoreconf -i
+     % ./configure PKG_CONFIG_PATH=<somewhere1>/lib/pkgconfig:<somewhere2>/lib/pkgconfig LDFLAGS="-Wl,-rpath,<somewhere1>/lib" --prefix=<somewhere3>
+     % make
+     % make install
+
+Build curl
+
+     % cd ..
+     % git clone https://github.com/curl/curl
+     % cd curl
+     % ./buildconf
+     % ./configure --without-ssl --with-gnutls=<somewhere1> --with-nghttp3=<somewhere2> --with-ngtcp2=<somewhere3> --enable-alt-svc
+     % make
+
 # quiche version
 
 ## build
diff --git a/lib/vquic/ngtcp2.c b/lib/vquic/ngtcp2.c
index 22aa53b29..5f7b6e2e0 100644
--- a/lib/vquic/ngtcp2.c
+++ b/lib/vquic/ngtcp2.c
@@ -26,7 +26,9 @@
 #include <ngtcp2/ngtcp2.h>
 #include <ngtcp2/ngtcp2_crypto.h>
 #include <nghttp3/nghttp3.h>
+#ifdef USE_OPENSSL
 #include <openssl/err.h>
+#endif
 #include "urldata.h"
 #include "sendf.h"
 #include "strdup.h"
@@ -69,10 +71,18 @@ struct h3out {
 #define QUIC_MAX_STREAMS (256*1024)
 #define QUIC_MAX_DATA (1*1024*1024)
 #define QUIC_IDLE_TIMEOUT 60000 /* milliseconds */
+
+#ifdef USE_OPENSSL
 #define QUIC_CIPHERS                                                          \
   "TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384:TLS_CHACHA20_"               \
   "POLY1305_SHA256:TLS_AES_128_CCM_SHA256"
 #define QUIC_GROUPS "P-256:X25519:P-384:P-521"
+#elif defined(USE_GNUTLS)
+#define QUIC_PRIORITY \
+  "NORMAL:-VERS-ALL:+VERS-TLS1.3:-CIPHER-ALL:+AES-128-GCM:+AES-256-GCM:" \
+  "+CHACHA20-POLY1305:+AES-128-CCM:-GROUP-ALL:+GROUP-SECP256R1:" \
+  "+GROUP-X25519:+GROUP-SECP384R1:+GROUP-SECP521R1"
+#endif
 
 static CURLcode ng_process_ingress(struct connectdata *conn,
                                    curl_socket_t sockfd,
@@ -101,6 +111,7 @@ static void quic_printf(void *user_data, const char *fmt, ...)
 }
 #endif
 
+#ifdef USE_OPENSSL
 static ngtcp2_crypto_level
 quic_from_ossl_level(OSSL_ENCRYPTION_LEVEL ossl_level)
 {
@@ -117,6 +128,24 @@ quic_from_ossl_level(OSSL_ENCRYPTION_LEVEL ossl_level)
     assert(0);
   }
 }
+#elif defined(USE_GNUTLS)
+static ngtcp2_crypto_level
+quic_from_gtls_level(gnutls_record_encryption_level_t gtls_level)
+{
+  switch(gtls_level) {
+  case GNUTLS_ENCRYPTION_LEVEL_INITIAL:
+    return NGTCP2_CRYPTO_LEVEL_INITIAL;
+  case GNUTLS_ENCRYPTION_LEVEL_EARLY:
+    return NGTCP2_CRYPTO_LEVEL_EARLY;
+  case GNUTLS_ENCRYPTION_LEVEL_HANDSHAKE:
+    return NGTCP2_CRYPTO_LEVEL_HANDSHAKE;
+  case GNUTLS_ENCRYPTION_LEVEL_APPLICATION:
+    return NGTCP2_CRYPTO_LEVEL_APP;
+  default:
+    assert(0);
+  }
+}
+#endif
 
 static int setup_initial_crypto_context(struct quicsocket *qs)
 {
@@ -150,6 +179,7 @@ static void quic_settings(ngtcp2_settings *s,
 }
 
 static FILE *keylog_file; /* not thread-safe */
+#ifdef USE_OPENSSL
 static void keylog_callback(const SSL *ssl, const char *line)
 {
   (void)ssl;
@@ -157,41 +187,52 @@ static void keylog_callback(const SSL *ssl, const char *line)
   fputc('\n', keylog_file);
   fflush(keylog_file);
 }
-
-static int init_ngh3_conn(struct quicsocket *qs);
-
-static int quic_set_encryption_secrets(SSL *ssl,
-                                       OSSL_ENCRYPTION_LEVEL ossl_level,
-                                       const uint8_t *rx_secret,
-                                       const uint8_t *tx_secret,
-                                       size_t secretlen)
+#elif defined(USE_GNUTLS)
+static int keylog_callback(gnutls_session_t session, const char *label,
+                    const gnutls_datum_t *secret)
 {
-  struct quicsocket *qs = (struct quicsocket *)SSL_get_app_data(ssl);
-  int level = quic_from_ossl_level(ossl_level);
-
-  if(level != NGTCP2_CRYPTO_LEVEL_EARLY &&
-     ngtcp2_crypto_derive_and_install_rx_key(
-         qs->qconn, ssl, NULL, NULL, NULL, level, rx_secret, secretlen) != 0)
-    return 0;
+  gnutls_datum_t crandom;
+  gnutls_datum_t srandom;
+  gnutls_datum_t crandom_hex = { NULL, 0 };
+  gnutls_datum_t secret_hex = { NULL, 0 };
+  int rc = 0;
+
+  gnutls_session_get_random(session, &crandom, &srandom);
+  if(crandom.size != 32) {
+    return -1;
+  }
 
-  if(ngtcp2_crypto_derive_and_install_tx_key(
-         qs->qconn, ssl, NULL, NULL, NULL, level, tx_secret, secretlen) != 0)
-    return 0;
+  rc = gnutls_hex_encode2(&crandom, &crandom_hex);
+  if(rc < 0) {
+    fprintf(stderr, "gnutls_hex_encode2 failed: %s\n",
+            gnutls_strerror(rc));
+    goto out;
+  }
 
-  if(level == NGTCP2_CRYPTO_LEVEL_APP) {
-    if(init_ngh3_conn(qs) != CURLE_OK)
-      return 0;
+  rc = gnutls_hex_encode2(secret, &secret_hex);
+  if(rc < 0) {
+    fprintf(stderr, "gnutls_hex_encode2 failed: %s\n",
+            gnutls_strerror(rc));
+    goto out;
   }
 
-  return 1;
+  fprintf(keylog_file, "%s %s %s\n", label, crandom_hex.data, secret_hex.data);
+  fflush(keylog_file);
+
+ out:
+  gnutls_free(crandom_hex.data);
+  gnutls_free(secret_hex.data);
+  return rc;
 }
+#endif
 
-static int quic_add_handshake_data(SSL *ssl, OSSL_ENCRYPTION_LEVEL ossl_level,
-                                   const uint8_t *data, size_t len)
+static int init_ngh3_conn(struct quicsocket *qs);
+
+static int write_client_handshake(struct quicsocket *qs,
+                                  ngtcp2_crypto_level level,
+                                  const uint8_t *data, size_t len)
 {
-  struct quicsocket *qs = (struct quicsocket *)SSL_get_app_data(ssl);
   struct quic_handshake *crypto_data;
-  ngtcp2_crypto_level level = quic_from_ossl_level(ossl_level);
   int rv;
 
   crypto_data = &qs->crypto_data[level];
@@ -220,6 +261,42 @@ static int quic_add_handshake_data(SSL *ssl, OSSL_ENCRYPTION_LEVEL ossl_level,
   return 1;
 }
 
+#ifdef USE_OPENSSL
+static int quic_set_encryption_secrets(SSL *ssl,
+                                       OSSL_ENCRYPTION_LEVEL ossl_level,
+                                       const uint8_t *rx_secret,
+                                       const uint8_t *tx_secret,
+                                       size_t secretlen)
+{
+  struct quicsocket *qs = (struct quicsocket *)SSL_get_app_data(ssl);
+  int level = quic_from_ossl_level(ossl_level);
+
+  if(level != NGTCP2_CRYPTO_LEVEL_EARLY &&
+     ngtcp2_crypto_derive_and_install_rx_key(
+         qs->qconn, ssl, NULL, NULL, NULL, level, rx_secret, secretlen) != 0)
+    return 0;
+
+  if(ngtcp2_crypto_derive_and_install_tx_key(
+         qs->qconn, ssl, NULL, NULL, NULL, level, tx_secret, secretlen) != 0)
+    return 0;
+
+  if(level == NGTCP2_CRYPTO_LEVEL_APP) {
+    if(init_ngh3_conn(qs) != CURLE_OK)
+      return 0;
+  }
+
+  return 1;
+}
+
+static int quic_add_handshake_data(SSL *ssl, OSSL_ENCRYPTION_LEVEL ossl_level,
+                                   const uint8_t *data, size_t len)
+{
+  struct quicsocket *qs = (struct quicsocket *)SSL_get_app_data(ssl);
+  ngtcp2_crypto_level level = quic_from_ossl_level(ossl_level);
+
+  return write_client_handshake(qs, level, data, len);
+}
+
 static int quic_flush_flight(SSL *ssl)
 {
   (void)ssl;
@@ -307,6 +384,193 @@ static int quic_init_ssl(struct quicsocket *qs)
   SSL_set_tlsext_host_name(qs->ssl, hostname);
   return 0;
 }
+#elif defined(USE_GNUTLS)
+static int secret_func(gnutls_session_t ssl,
+                       gnutls_record_encryption_level_t gtls_level,
+                       const void *rx_secret,
+                       const void *tx_secret, size_t secretlen)
+{
+  struct quicsocket *qs = gnutls_session_get_ptr(ssl);
+  int level = quic_from_gtls_level(gtls_level);
+
+  if(level != NGTCP2_CRYPTO_LEVEL_EARLY &&
+     ngtcp2_crypto_derive_and_install_rx_key(
+         qs->qconn, ssl, NULL, NULL, NULL, level, rx_secret, secretlen) != 0)
+    return 0;
+
+  if(ngtcp2_crypto_derive_and_install_tx_key(
+         qs->qconn, ssl, NULL, NULL, NULL, level, tx_secret, secretlen) != 0)
+    return 0;
+
+  if(level == NGTCP2_CRYPTO_LEVEL_APP) {
+    if(init_ngh3_conn(qs) != CURLE_OK)
+      return -1;
+  }
+
+  return 0;
+}
+
+static int read_func(gnutls_session_t ssl,
+                     gnutls_record_encryption_level_t gtls_level,
+                     gnutls_handshake_description_t htype, const void *data,
+                     size_t len)
+{
+  struct quicsocket *qs = gnutls_session_get_ptr(ssl);
+  ngtcp2_crypto_level level = quic_from_gtls_level(gtls_level);
+  int rv;
+
+  if(htype == GNUTLS_HANDSHAKE_CHANGE_CIPHER_SPEC)
+    return 0;
+
+  rv = write_client_handshake(qs, level, data, len);
+  if(rv == 0)
+    return -1;
+
+  return 0;
+}
+
+static int alert_read_func(gnutls_session_t ssl,
+                           gnutls_record_encryption_level_t gtls_level,
+                           gnutls_alert_level_t alert_level,
+                           gnutls_alert_description_t alert_desc)
+{
+  struct quicsocket *qs = gnutls_session_get_ptr(ssl);
+  (void)gtls_level;
+  (void)alert_level;
+
+  qs->tls_alert = alert_desc;
+  return 1;
+}
+
+static int tp_recv_func(gnutls_session_t ssl, const uint8_t *data,
+                        size_t data_size)
+{
+  struct quicsocket *qs = gnutls_session_get_ptr(ssl);
+  ngtcp2_transport_params params;
+
+  if(ngtcp2_decode_transport_params(
+         &params, NGTCP2_TRANSPORT_PARAMS_TYPE_ENCRYPTED_EXTENSIONS,
+         data, data_size) != 0)
+    return -1;
+
+  if(ngtcp2_conn_set_remote_transport_params(qs->qconn, &params) != 0)
+    return -1;
+
+  return 0;
+}
+
+static int tp_send_func(gnutls_session_t ssl, gnutls_buffer_t extdata)
+{
+  struct quicsocket *qs = gnutls_session_get_ptr(ssl);
+  uint8_t paramsbuf[64];
+  ngtcp2_transport_params params;
+  ssize_t nwrite;
+  int rc;
+
+  ngtcp2_conn_get_local_transport_params(qs->qconn, &params);
+  nwrite = ngtcp2_encode_transport_params(
+    paramsbuf, sizeof(paramsbuf), NGTCP2_TRANSPORT_PARAMS_TYPE_CLIENT_HELLO,
+    &params);
+  if(nwrite < 0) {
+    fprintf(stderr, "ngtcp2_encode_transport_params: %s\n",
+          ngtcp2_strerror((int)nwrite));
+    return -1;
+  }
+
+  rc = gnutls_buffer_append_data(extdata, paramsbuf, nwrite);
+  if(rc < 0)
+    return rc;
+
+  return (int)nwrite;
+}
+
+static int quic_init_ssl(struct quicsocket *qs)
+{
+  gnutls_datum_t alpn = {NULL, 0};
+  /* this will need some attention when HTTPS proxy over QUIC get fixed */
+  const char * const hostname = qs->conn->host.name;
+  const char *keylog_filename;
+  int rc;
+
+  if(qs->ssl)
+    gnutls_deinit(qs->ssl);
+
+  gnutls_init(&qs->ssl, GNUTLS_CLIENT);
+  gnutls_session_set_ptr(qs->ssl, qs);
+
+  rc = gnutls_priority_set_direct(qs->ssl, QUIC_PRIORITY, NULL);
+  if(rc < 0) {
+    fprintf(stderr, "gnutls_priority_set_direct failed: %s\n",
+            gnutls_strerror(rc));
+    return 1;
+  }
+
+  gnutls_handshake_set_secret_function(qs->ssl, secret_func);
+  gnutls_handshake_set_read_function(qs->ssl, read_func);
+  gnutls_alert_set_read_function(qs->ssl, alert_read_func);
+
+  rc = gnutls_session_ext_register(qs->ssl, "QUIC Transport Parameters",
+                                   0xffa5, GNUTLS_EXT_TLS,
+                                   tp_recv_func, tp_send_func,
+                                   NULL, NULL, NULL,
+                                   GNUTLS_EXT_FLAG_TLS |
+                                   GNUTLS_EXT_FLAG_CLIENT_HELLO |
+                                   GNUTLS_EXT_FLAG_EE);
+  if(rc < 0) {
+    fprintf(stderr, "gnutls_session_ext_register failed: %s\n",
+            gnutls_strerror(rc));
+    return 1;
+  }
+
+  keylog_filename = getenv("SSLKEYLOGFILE");
+  if(keylog_filename) {
+    keylog_file = fopen(keylog_filename, "wb");
+    if(keylog_file) {
+      gnutls_session_set_keylog_function(qs->ssl, keylog_callback);
+    }
+  }
+
+  if(qs->cred)
+    gnutls_certificate_free_credentials(qs->cred);
+
+  rc = gnutls_certificate_allocate_credentials(&qs->cred);
+  if(rc < 0) {
+    fprintf(stderr, "gnutls_certificate_allocate_credentials failed: %s\n",
+            gnutls_strerror(rc));
+    return 1;
+  }
+
+  rc = gnutls_certificate_set_x509_system_trust(qs->cred);
+  if(rc < 0) {
+    fprintf(stderr, "gnutls_certificate_set_x509_system_trust failed: %s\n",
+            gnutls_strerror(rc));
+    return 1;
+  }
+
+  rc = gnutls_credentials_set(qs->ssl, GNUTLS_CRD_CERTIFICATE, qs->cred);
+  if(rc < 0) {
+    fprintf(stderr, "gnutls_credentials_set failed: %s\n",
+            gnutls_strerror(rc));
+    return 1;
+  }
+
+  switch(qs->version) {
+#ifdef NGTCP2_PROTO_VER
+  case NGTCP2_PROTO_VER:
+    /* strip the first byte from NGTCP2_ALPN_H3 */
+    alpn.data = (unsigned char *)NGTCP2_ALPN_H3 + 1;
+    alpn.size = sizeof(NGTCP2_ALPN_H3) - 2;
+    break;
+#endif
+  }
+  if(alpn.data)
+    gnutls_alpn_set_protocols(qs->ssl, &alpn, 1, 0);
+
+  /* set SNI */
+  gnutls_server_name_set(qs->ssl, GNUTLS_NAME_DNS, hostname, strlen(hostname));
+  return 0;
+}
+#endif
 
 static int cb_initial(ngtcp2_conn *quic, void *user_data)
 {
@@ -560,9 +824,11 @@ CURLcode Curl_quic_connect(struct connectdata *conn,
   struct quicsocket *qs = &conn->hequic[sockindex];
   char ipbuf[40];
   long port;
+#ifdef USE_OPENSSL
   uint8_t paramsbuf[64];
   ngtcp2_transport_params params;
   ssize_t nwrite;
+#endif
 
   qs->conn = conn;
 
@@ -578,9 +844,11 @@ CURLcode Curl_quic_connect(struct connectdata *conn,
         sockfd, ipbuf, port);
 
   qs->version = NGTCP2_PROTO_VER;
+#ifdef USE_OPENSSL
   qs->sslctx = quic_ssl_ctx(data);
   if(!qs->sslctx)
     return CURLE_QUIC_CONNECT_ERROR;
+#endif
 
   if(quic_init_ssl(qs))
     return CURLE_QUIC_CONNECT_ERROR;
@@ -617,6 +885,7 @@ CURLcode Curl_quic_connect(struct connectdata *conn,
   if(rc)
     return CURLE_QUIC_CONNECT_ERROR;
 
+#ifdef USE_OPENSSL
   ngtcp2_conn_get_local_transport_params(qs->qconn, &params);
   nwrite = ngtcp2_encode_transport_params(
     paramsbuf, sizeof(paramsbuf), NGTCP2_TRANSPORT_PARAMS_TYPE_CLIENT_HELLO,
@@ -629,6 +898,7 @@ CURLcode Curl_quic_connect(struct connectdata *conn,
 
   if(!SSL_set_quic_transport_params(qs->ssl, paramsbuf, nwrite))
     return CURLE_QUIC_CONNECT_ERROR;
+#endif
 
   rc = setup_initial_crypto_context(qs);
   if(rc)
@@ -680,12 +950,22 @@ static CURLcode ng_disconnect(struct connectdata *conn,
   struct quicsocket *qs = &conn->hequic[0];
   (void)dead_connection;
   if(qs->ssl)
+#ifdef USE_OPENSSL
     SSL_free(qs->ssl);
+#elif defined(USE_GNUTLS)
+    gnutls_deinit(qs->ssl);
+#endif
+#ifdef USE_GNUTLS
+  if(qs->cred)
+    gnutls_certificate_free_credentials(qs->cred);
+#endif
   for(i = 0; i < 3; i++)
     free(qs->crypto_data[i].buf);
   nghttp3_conn_del(qs->h3conn);
   ngtcp2_conn_del(qs->qconn);
+#ifdef USE_OPENSSL
   SSL_CTX_free(qs->sslctx);
+#endif
   return CURLE_OK;
 }
 
diff --git a/lib/vquic/ngtcp2.h b/lib/vquic/ngtcp2.h
index 30d442fdd..862a00107 100644
--- a/lib/vquic/ngtcp2.h
+++ b/lib/vquic/ngtcp2.h
@@ -28,7 +28,11 @@
 
 #include <ngtcp2/ngtcp2.h>
 #include <nghttp3/nghttp3.h>
+#ifdef USE_OPENSSL
 #include <openssl/ssl.h>
+#elif defined(USE_GNUTLS)
+#include <gnutls/gnutls.h>
+#endif
 
 struct quic_handshake {
   char *buf;       /* pointer to the buffer */
@@ -44,8 +48,13 @@ struct quicsocket {
   ngtcp2_cid scid;
   uint32_t version;
   ngtcp2_settings settings;
+#ifdef USE_OPENSSL
   SSL_CTX *sslctx;
   SSL *ssl;
+#elif defined(USE_GNUTLS)
+  gnutls_certificate_credentials_t cred;
+  gnutls_session_t ssl;
+#endif
   struct quic_handshake crypto_data[3];
   /* the last TLS alert description generated by the local endpoint */
   uint8_t tls_alert;