From 1f9427e1d9672b93577aea4c9d5a63575ee0b525 Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Sat, 6 May 2023 19:43:17 +0200
Subject: add convenience function for content-length limiation

---
 src/exchange/taler-exchange-httpd.c | 29 ++----------------
 src/include/taler_mhd_lib.h         | 59 ++++++++++++++++++++++++++++++++-----
 src/mhd/mhd_parsing.c               | 42 ++++++++++++++++++++++++++
 3 files changed, 95 insertions(+), 35 deletions(-)

(limited to 'src')

diff --git a/src/exchange/taler-exchange-httpd.c b/src/exchange/taler-exchange-httpd.c
index ac3eae272..97cf54c86 100644
--- a/src/exchange/taler-exchange-httpd.c
+++ b/src/exchange/taler-exchange-httpd.c
@@ -1617,33 +1617,8 @@ handle_mhd_request (void *cls,
     if (0 == strcasecmp (method,
                          MHD_HTTP_METHOD_POST))
     {
-      const char *cl;
-
-      /* Maybe check for maximum upload size
-         and refuse requests if they are just too big. */
-      cl = MHD_lookup_connection_value (connection,
-                                        MHD_HEADER_KIND,
-                                        MHD_HTTP_HEADER_CONTENT_LENGTH);
-      if (NULL != cl)
-      {
-        unsigned long long cv;
-        char dummy;
-
-        if (1 != sscanf (cl,
-                         "%llu%c",
-                         &cv,
-                         &dummy))
-        {
-          /* Not valid HTTP request, just close connection. */
-          GNUNET_break_op (0);
-          return MHD_NO;
-        }
-        if (cv > TALER_MHD_REQUEST_BUFFER_MAX)
-        {
-          GNUNET_break_op (0);
-          return TALER_MHD_reply_request_too_large (connection);
-        }
-      }
+      TALER_MHD_check_content_length (connection,
+                                      TALER_MHD_REQUEST_BUFFER_MAX);
     }
   }
 
diff --git a/src/include/taler_mhd_lib.h b/src/include/taler_mhd_lib.h
index 9c7c06d9a..e4aa916e7 100644
--- a/src/include/taler_mhd_lib.h
+++ b/src/include/taler_mhd_lib.h
@@ -596,14 +596,14 @@ TALER_MHD_parse_request_header_data (struct MHD_Connection *connection,
     bool p;                                                               \
     switch (TALER_MHD_parse_request_header_data (connection, name,        \
                                                  val, sizeof (*val), &p)) \
-    {                      \
-    case GNUNET_SYSERR:    \
-      GNUNET_break (0);    \
-      return MHD_NO;       \
-    case GNUNET_NO:        \
-      GNUNET_break_op (0); \
-      return MHD_YES;      \
-    case GNUNET_OK:        \
+    {                       \
+    case GNUNET_SYSERR:     \
+      GNUNET_break (0);     \
+      return MHD_NO;        \
+    case GNUNET_NO:         \
+      GNUNET_break_op (0);  \
+      return MHD_YES;       \
+    case GNUNET_OK:         \
       if (required & (! p)) \
       return TALER_MHD_reply_with_error (   \
         connection,                         \
@@ -634,6 +634,49 @@ TALER_MHD_parse_request_header_data (struct MHD_Connection *connection,
   } while (0)
 
 
+/**
+ * Check that the 'Content-Length' header is giving
+ * a length below @a max_len. If not, return an
+ * appropriate error response and return the
+ * correct #MHD_YES/#MHD_NO value from this function.
+ *
+ * @param connection the MHD connection
+ * @param max_len maximum allowed content length
+ * @return
+ *   #GNUNET_YES if the the argument is present
+ *   #GNUNET_NO if the argument is absent or malformed
+ *   #GNUNET_SYSERR on internal error (error response could not be sent)
+ */
+enum GNUNET_GenericReturnValue
+TALER_MHD_check_content_length_ (struct MHD_Connection *connection,
+                                 unsigned long long max_len);
+
+
+/**
+ * Check that the 'Content-Length' header is giving
+ * a length below @a max_len. If not, return an
+ * appropriate error response and return the
+ * correct #MHD_YES/#MHD_NO value from this function.
+ *
+ * @param connection the MHD connection
+ * @param max_len maximum allowed content length
+ */
+#define TALER_MHD_check_content_length(connection,max_len)         \
+  do {                                                             \
+    switch (TALER_MHD_check_content_length_ (connection, max_len)) \
+    {                       \
+    case GNUNET_SYSERR:     \
+      GNUNET_break (0);     \
+      return MHD_NO;        \
+    case GNUNET_NO:         \
+      GNUNET_break_op (0);  \
+      return MHD_YES;       \
+    case GNUNET_OK:         \
+      break;                \
+    }                       \
+  } while (0)
+
+
 /**
  * Parse the configuration to determine on which port
  * or UNIX domain path we should run an HTTP service.
diff --git a/src/mhd/mhd_parsing.c b/src/mhd/mhd_parsing.c
index e76450831..b047df7d3 100644
--- a/src/mhd/mhd_parsing.c
+++ b/src/mhd/mhd_parsing.c
@@ -350,4 +350,46 @@ TALER_MHD_parse_json_array (struct MHD_Connection *connection,
 }
 
 
+enum GNUNET_GenericReturnValue
+TALER_MHD_check_content_length_ (struct MHD_Connection *connection,
+                                 unsigned long long max_len)
+{
+  const char *cl;
+  unsigned long long cv;
+  char dummy;
+
+  /* Maybe check for maximum upload size
+       and refuse requests if they are just too big. */
+  cl = MHD_lookup_connection_value (connection,
+                                    MHD_HEADER_KIND,
+                                    MHD_HTTP_HEADER_CONTENT_LENGTH);
+  if (NULL == cl)
+    return GNUNET_OK;
+  if (1 != sscanf (cl,
+                   "%llu%c",
+                   &cv,
+                   &dummy))
+  {
+    /* Not valid HTTP request, just close connection. */
+    GNUNET_break_op (0);
+    return (MHD_YES ==
+            TALER_MHD_reply_with_error (connection,
+                                        MHD_HTTP_BAD_REQUEST,
+                                        TALER_EC_GENERIC_PARAMETER_MALFORMED,
+                                        MHD_HTTP_HEADER_CONTENT_LENGTH))
+      ? GNUNET_NO
+      : GNUNET_SYSERR;
+  }
+  if (cv > TALER_MHD_REQUEST_BUFFER_MAX)
+  {
+    GNUNET_break_op (0);
+    return (MHD_YES ==
+            TALER_MHD_reply_request_too_large (connection))
+    ? GNUNET_NO
+    : GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
 /* end of mhd_parsing.c */
-- 
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