From 5341e4d62ab3ff635af98c5fc2326ae9f717322f Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Sun, 21 Jun 2020 12:05:56 +0200
Subject: address 413 fixme

---
 src/backend/taler-merchant-httpd.c                 | 51 ++++++++++++++++++++++
 src/backend/taler-merchant-httpd.h                 | 11 +++++
 .../taler-merchant-httpd_private-post-reserves.c   |  1 +
 3 files changed, 63 insertions(+)

diff --git a/src/backend/taler-merchant-httpd.c b/src/backend/taler-merchant-httpd.c
index f3d8d757..314e65a4 100644
--- a/src/backend/taler-merchant-httpd.c
+++ b/src/backend/taler-merchant-httpd.c
@@ -66,6 +66,11 @@
  */
 #define UNIX_BACKLOG 500
 
+/**
+ * Default maximum upload size permitted.  Can be overridden
+ * per handler.
+ */
+#define DEFAULT_MAX_UPLOAD_SIZE (16 * 1024)
 
 /**
  * Which currency do we use?
@@ -1029,6 +1034,22 @@ url_handler (void *cls,
     {
       int res;
 
+      if ( (hc->total_upload + *upload_data_size < hc->total_upload) ||
+           (hc->total_upload + *upload_data_size > hc->rh->max_upload) )
+      {
+        /* Client exceeds upload limit. Should _usually_ be checked earlier
+           when we look at the MHD_HTTP_HEADER_CONTENT_LENGTH, alas with
+           chunked encoding an uploader MAY have ommitted this, and thus
+           not permitted us to check on time. In this case, we just close
+           the connection once it exceeds our limit (instead of waiting
+           for the upload to complete and then fail). This could theoretically
+           cause some clients to retry, alas broken or malicious clients
+           are likely to retry anyway, so little we can do about it, and
+           failing earlier seems the best option here.  *///
+        GNUNET_break_op (0);
+        return MHD_NO;
+      }
+      hc->total_upload += *upload_data_size;
       res = TALER_MHD_parse_post_json (connection,
                                        &hc->json_parse_context,
                                        upload_data,
@@ -1265,6 +1286,36 @@ url_handler (void *cls,
                                      MHD_HTTP_METHOD_PATCH)) );
   if (hc->has_body)
   {
+    const char *cl;
+
+    cl = MHD_lookup_connection_value (connection,
+                                      MHD_HEADER_KIND,
+                                      MHD_HTTP_HEADER_CONTENT_LENGTH);
+    if (NULL != cl)
+    {
+      unsigned long long cv;
+      size_t mul = hc->rh->max_upload;
+
+      if (0 == mul)
+        mul = DEFAULT_MAX_UPLOAD_SIZE;
+      if (1 != sscanf (cl,
+                       "%llu",
+                       &cv))
+      {
+        /* Not valid HTTP request, just close connection. */
+        GNUNET_break_op (0);
+        return MHD_NO;
+      }
+      if (cv > mul)
+      {
+        GNUNET_break_op (0);
+        return TALER_MHD_reply_with_error (connection,
+                                           MHD_HTTP_PAYLOAD_TOO_LARGE,
+                                           TALER_EC_UPLOAD_EXCEEDS_LIMIT,
+                                           "upload exceeds limit");
+      }
+    }
+
     /* FIXME: Maybe check for maximum upload size here
        and refuse if it is too big? (Note: maximum upload
        size may need to vary based on the handler.) */
diff --git a/src/backend/taler-merchant-httpd.h b/src/backend/taler-merchant-httpd.h
index 7e1090d3..42d86d3f 100644
--- a/src/backend/taler-merchant-httpd.h
+++ b/src/backend/taler-merchant-httpd.h
@@ -197,6 +197,12 @@ struct TMH_RequestHandler
    */
   size_t data_size;
 
+  /**
+   * Maximum upload size allowed for this handler.
+   * 0 for DEFAULT_MAX_UPLOAD_SIZE
+   */
+  size_t max_upload;
+
   /**
    * Handler to be called for this URL/METHOD combination.
    *
@@ -285,6 +291,11 @@ struct TMH_HandlerContext
    */
   void *json_parse_context;
 
+  /**
+   * Total size of the upload so far.
+   */
+  uint64_t total_upload;
+
   /**
    * Set to true if this is an #MHD_HTTP_METHOD_POST or #MHD_HTTP_METHOD_PATCH request.
    * (In principle #MHD_HTTP_METHOD_PUT may also belong, but we do not have PUTs
diff --git a/src/backend/taler-merchant-httpd_private-post-reserves.c b/src/backend/taler-merchant-httpd_private-post-reserves.c
index 01bba5d4..5a691f4d 100644
--- a/src/backend/taler-merchant-httpd_private-post-reserves.c
+++ b/src/backend/taler-merchant-httpd_private-post-reserves.c
@@ -25,6 +25,7 @@
 #include "platform.h"
 #include "taler-merchant-httpd_exchanges.h"
 #include "taler-merchant-httpd_private-post-reserves.h"
+#include "taler-merchant-httpd_reserves.h"
 #include <taler/taler_json_lib.h>
 
 
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