From ab281cb7503cb85ef0f44f4f13213380b52cbce5 Mon Sep 17 00:00:00 2001
From: Giuseppe Modugno <giuseppe.modugno.loqed@gmail.com>
Date: Mon, 27 Nov 2017 09:18:41 +0100
Subject: [PATCH] httpd: move httpd_cgi_handler() call

This patch moves in advance httpd_cgi_handler() call, before assigning
variables like hs->file and hs->left.

In this way, CGI handler could prepare the reply data and set the
"file properties", like file->data and file->len. At the exit, hs->file
and hs->left is correctly assigned.

The handler prototype says it can't access file pointer, however it is
simple to obtain it after setting LWIP_HTTPD_FILE_STATE that enables a
"file state" pointer. It is sufficient to assign file->state to file
itself in fs_open_custom().

For example, I have the request GET /login.cgi?user=admin&pwd=admin and
I have to reply with some JSON data. The answer depends on parameters
user and pwd passed in the query string.
---
 src/apps/httpd/httpd.c | 42 +++++++++++++++++++++---------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/apps/httpd/httpd.c b/src/apps/httpd/httpd.c
index 88f76a17..276ec245 100644
--- a/src/apps/httpd/httpd.c
+++ b/src/apps/httpd/httpd.c
@@ -2292,6 +2292,27 @@ http_init_file(struct http_state *hs, struct fs_file *file, int is_09, const cha
     LWIP_UNUSED_ARG(tag_check);
 #endif /* LWIP_HTTPD_SSI */
     hs->handle = file;
+#if LWIP_HTTPD_CGI_SSI
+    if (params != NULL) {
+      /* URI contains parameters, call generic CGI handler */
+      int count;
+#if LWIP_HTTPD_CGI
+      if (http_cgi_paramcount >= 0) {
+        count = http_cgi_paramcount;
+      } else
+#endif
+      {
+        count = extract_uri_parameters(hs, params);
+      }
+      httpd_cgi_handler(uri, count, http_cgi_params, http_cgi_param_vals
+#if defined(LWIP_HTTPD_FILE_STATE) && LWIP_HTTPD_FILE_STATE
+                        , hs->handle->state
+#endif /* LWIP_HTTPD_FILE_STATE */
+                       );
+    }
+#else /* LWIP_HTTPD_CGI_SSI */
+    LWIP_UNUSED_ARG(params);
+#endif /* LWIP_HTTPD_CGI_SSI */
     hs->file = file->data;
     LWIP_ASSERT("File length must be positive!", (file->len >= 0));
 #if LWIP_HTTPD_CUSTOM_FILES
@@ -2323,27 +2344,6 @@ http_init_file(struct http_state *hs, struct fs_file *file, int is_09, const cha
       }
     }
 #endif /* LWIP_HTTPD_SUPPORT_V09*/
-#if LWIP_HTTPD_CGI_SSI
-    if (params != NULL) {
-      /* URI contains parameters, call generic CGI handler */
-      int count;
-#if LWIP_HTTPD_CGI
-      if (http_cgi_paramcount >= 0) {
-        count = http_cgi_paramcount;
-      } else
-#endif
-      {
-        count = extract_uri_parameters(hs, params);
-      }
-      httpd_cgi_handler(uri, count, http_cgi_params, http_cgi_param_vals
-#if defined(LWIP_HTTPD_FILE_STATE) && LWIP_HTTPD_FILE_STATE
-                        , hs->handle->state
-#endif /* LWIP_HTTPD_FILE_STATE */
-                       );
-    }
-#else /* LWIP_HTTPD_CGI_SSI */
-    LWIP_UNUSED_ARG(params);
-#endif /* LWIP_HTTPD_CGI_SSI */
   } else {
     hs->handle = NULL;
     hs->file = NULL;