Fix post processor breaking large fields in multiple parts.

src/http_request.cpp

@@ -116,6 +116,21 @@ void http_request::populate_args() const {
     cache->args_populated = true;
 }
 
+
+void http_request::grow_last_arg(const std::string& key, const std::string& value) {
+    auto it = cache->unescaped_args.find(key);
+
+    if (it != cache->unescaped_args.end()) {
+        if (!it->second.empty()) {
+            it->second.back() += value;
+        } else {
+            it->second.push_back(value);
+        }
+    } else {
+        cache->unescaped_args[key] = {value};
+    }
+}
+
 http_arg_value http_request::get_arg(std::string_view key) const {
     populate_args();
 

src/httpserver/http_request.hpp

@@ -335,6 +335,9 @@ class http_request {
      void set_arg_flat(const std::string& key, const std::string& value) {
          cache->unescaped_args[key] = { (value.substr(0, content_size_limit)) };
      }
+
+     void grow_last_arg(const std::string& key, const std::string& value);
+
      /**
       * Method used to set the content of the request
       * @param content The content to set.

src/webserver.cpp

@@ -467,12 +467,16 @@ MHD_Result webserver::post_iterator(void *cls, enum MHD_ValueKind kind,
         const char *transfer_encoding, const char *data, uint64_t off, size_t size) {
     // Parameter needed to respect MHD interface, but not needed here.
     std::ignore = kind;
-    std::ignore = off;
 
     struct details::modded_request* mr = (struct details::modded_request*) cls;
 
     if (!filename) {
         // There is no actual file, just set the arg key/value and return.
+        if (off > 0) {
+            mr->dhr->grow_last_arg(key, std::string(data, size));
+            return MHD_YES;
+        }
+
         mr->dhr->set_arg(key, std::string(data, size));
         return MHD_YES;
     }

test/integ/basic.cpp

@@ -19,6 +19,7 @@
 */
 
 #include <curl/curl.h>
+#include <cstring>
 #include <map>
 #include <memory>
 #include <numeric>
@@ -69,6 +70,26 @@ class simple_resource : public http_resource {
      }
 };
 
+class large_post_resource_last_value : public http_resource {
+ public:
+     shared_ptr<http_response> render_GET(const http_request&) {
+         return std::make_shared<string_response>("OK", 200, "text/plain");
+     }
+     shared_ptr<http_response> render_POST(const http_request& req) {
+         return std::make_shared<string_response>(std::string(req.get_arg("arg1").get_all_values().back()), 200, "text/plain");
+     }
+};
+
+class large_post_resource_first_value : public http_resource {
+ public:
+     shared_ptr<http_response> render_GET(const http_request&) {
+         return std::make_shared<string_response>("OK", 200, "text/plain");
+     }
+     shared_ptr<http_response> render_POST(const http_request& req) {
+         return std::make_shared<string_response>(std::string(req.get_arg("arg1").get_all_values().front()), 200, "text/plain");
+     }
+};
+
 class arg_value_resource : public http_resource {
  public:
      shared_ptr<http_response> render_GET(const http_request&) {
@@ -824,6 +845,93 @@ LT_BEGIN_AUTO_TEST(basic_suite, postprocessor)
     curl_easy_cleanup(curl);
 LT_END_AUTO_TEST(postprocessor)
 
+LT_BEGIN_AUTO_TEST(basic_suite, postprocessor_large_field_last_field)
+    large_post_resource_last_value resource;
+    LT_ASSERT_EQ(true, ws->register_resource("base", &resource));
+    curl_global_init(CURL_GLOBAL_ALL);
+    string s;
+    CURL *curl = curl_easy_init();
+    CURLcode res;
+
+    const int size = 20000;
+    const char value = 'A';
+    const char* prefix = "arg1=BB&arg1=";
+
+    // Calculate the total length of the string
+    int totalLength = std::strlen(prefix) + size;
+
+    // Allocate memory for the char array
+    char* cString = new char[totalLength + 1];  // +1 for the null terminator
+
+    // Copy the prefix
+    int offset = std::snprintf(cString, totalLength + 1, "%s", prefix);
+
+    // Append 20,000 times the character 'A' to the string
+    for (int i = 0; i < size; ++i) {
+        cString[offset++] = value;
+    }
+
+    // Append the suffix
+    cString[offset] = '\0';
+
+    curl_easy_setopt(curl, CURLOPT_URL, "localhost:" PORT_STRING "/base");
+    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, cString);
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writefunc);
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &s);
+    res = curl_easy_perform(curl);
+    LT_ASSERT_EQ(res, 0);
+    LT_CHECK_EQ(s, std::string(20000, 'A'));
+
+    curl_easy_cleanup(curl);
+    delete[] cString;
+LT_END_AUTO_TEST(postprocessor_large_field_last_field)
+
+LT_BEGIN_AUTO_TEST(basic_suite, postprocessor_large_field_first_field)
+    large_post_resource_first_value resource;
+    LT_ASSERT_EQ(true, ws->register_resource("base", &resource));
+    curl_global_init(CURL_GLOBAL_ALL);
+    string s;
+    CURL *curl = curl_easy_init();
+    CURLcode res;
+
+    const int size = 20000;
+    const char value = 'A';
+    const char* prefix = "arg1=";
+    const char* middle = "&arg1=";
+    const char* suffix = "BB";
+
+    // Calculate the total length of the string
+    int totalLength = std::strlen(prefix) + size + std::strlen(middle) + std::strlen(suffix);
+
+    // Allocate memory for the char array
+    char* cString = new char[totalLength + 1];  // +1 for the null terminator
+
+    // Copy the prefix
+    int offset = std::snprintf(cString, totalLength + 1, "%s", prefix);
+
+    // Append 20,000 times the character 'A' to the string
+    for (int i = 0; i < size; ++i) {
+        cString[offset++] = value;
+    }
+
+    // Append the middle part
+    offset += std::snprintf(cString + offset, totalLength + 1 - offset, "%s", middle);
+
+    // Append the suffix
+    std::snprintf(cString + offset, totalLength + 1 - offset, "%s", suffix);
+
+    curl_easy_setopt(curl, CURLOPT_URL, "localhost:" PORT_STRING "/base");
+    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, cString);
+    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writefunc);
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, &s);
+    res = curl_easy_perform(curl);
+    LT_ASSERT_EQ(res, 0);
+    LT_CHECK_EQ(s, std::string(20000, 'A'));
+
+    curl_easy_cleanup(curl);
+    delete[] cString;
+LT_END_AUTO_TEST(postprocessor_large_field_first_field)
+
 LT_BEGIN_AUTO_TEST(basic_suite, same_key_different_value)
     arg_value_resource resource;
     LT_ASSERT_EQ(true, ws->register_resource("base", &resource));
@@ -844,7 +952,6 @@ LT_BEGIN_AUTO_TEST(basic_suite, same_key_different_value)
     curl_easy_cleanup(curl);
 LT_END_AUTO_TEST(same_key_different_value)
 
-
 LT_BEGIN_AUTO_TEST(basic_suite, same_key_different_value_plain_content)
     arg_value_resource resource;
     LT_ASSERT_EQ(true, ws->register_resource("base", &resource));