1 files changed, 133 insertions, 0 deletions
diff --git a/src/util/mhd.c b/src/util/mhd.c
new file mode 100644
index 000000000..e615de696
--- /dev/null
+++ b/src/util/mhd.c
@@ -0,0 +1,133 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2014-2020 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file mhd.c
+ * @brief MHD utility functions (used by the merchant backend)
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "taler_util.h"
+
+
+/**
+ * Find out if an MHD connection is using HTTPS (either
+ * directly or via proxy).
+ *
+ * @param connection MHD connection
+ * @returns #GNUNET_YES if the MHD connection is using https,
+ *          #GNUNET_NO if the MHD connection is using http,
+ *          #GNUNET_SYSERR if the connection type couldn't be determined
+ */
+int
+TALER_mhd_is_https (struct MHD_Connection *connection)
+{
+  const union MHD_ConnectionInfo *ci;
+  const union MHD_DaemonInfo *di;
+  const char *forwarded_proto = MHD_lookup_connection_value (connection,
+                                                             MHD_HEADER_KIND,
+                                                             "X-Forwarded-Proto");
+
+  if (NULL != forwarded_proto)
+  {
+    if (0 == strcmp (forwarded_proto,
+                     "https"))
+      return GNUNET_YES;
+    if (0 == strcmp (forwarded_proto,
+                     "http"))
+      return GNUNET_NO;
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  /* likely not reverse proxy, figure out if we are
+     http by asking MHD */
+  ci = MHD_get_connection_info (connection,
+                                MHD_CONNECTION_INFO_DAEMON);
+  if (NULL == ci)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  di = MHD_get_daemon_info (ci->daemon,
+                            MHD_DAEMON_INFO_FLAGS);
+  if (NULL == di)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  if (0 != (di->flags & MHD_USE_TLS))
+    return GNUNET_YES;
+  return GNUNET_NO;
+}
+
+
+/**
+ * Make an absolute URL for a given MHD connection.
+ *
+ * @param connection the connection to get the URL for
+ * @param path path of the url
+ * @param ... NULL-terminated key-value pairs (char *) for query parameters,
+ *        the value will be url-encoded
+ * @returns the URL, must be freed with #GNUNET_free
+ */
+char *
+TALER_url_absolute_mhd (struct MHD_Connection *connection,
+                        const char *path,
+                        ...)
+{
+  /* By default we assume we're running under HTTPS */
+  const char *proto;
+  const char *host;
+  const char *forwarded_host;
+  const char *prefix;
+  va_list args;
+  char *result;
+
+  if (GNUNET_YES == TALER_mhd_is_https (connection))
+    proto = "https";
+  else
+    proto = "http";
+
+  host = MHD_lookup_connection_value (connection, MHD_HEADER_KIND, "Host");
+  forwarded_host = MHD_lookup_connection_value (connection,
+                                                MHD_HEADER_KIND,
+                                                "X-Forwarded-Host");
+
+  prefix = MHD_lookup_connection_value (connection,
+                                        MHD_HEADER_KIND,
+                                        "X-Forwarded-Prefix");
+  if (NULL == prefix)
+    prefix = "";
+
+  if (NULL != forwarded_host)
+    host = forwarded_host;
+
+  if (NULL == host)
+  {
+    /* Should never happen, at last the host header should be defined */
+    GNUNET_break (0);
+    return NULL;
+  }
+
+  va_start (args,
+            path);
+  result = TALER_url_absolute_raw_va (proto,
+                                      host,
+                                      prefix,
+                                      path,
+                                      args);
+  va_end (args);
+  return result;
+}