CGI interface

1 files changed, 294 insertions, 0 deletions

diff --git a/plugins/cgi/cgi.cpp b/plugins/cgi/cgi.cpp
new file mode 100644
index 0000000..5921e98
--- /dev/null
+++ b/plugins/cgi/cgi.cpp
@@ -0,0 +1,294 @@
+#include "cgi.h"
+
+#include <boost/algorithm/string/predicate.hpp>
+#include <boost/coroutine2/coroutine.hpp>
+#include <boost/process.hpp>
+
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <string>
+#include <unordered_map>
+
+using namespace std::string_literals;
+namespace bp = boost::process;
+namespace fs = std::filesystem;
+
+namespace {
+
+ const std::string gateway_interface{"CGI/1.1"};
+
+ struct CGIContext
+ {
+   std::function<std::string(const std::string& key)>& GetServerParam;
+   std::function<std::string(const std::string& key)>& GetRequestParam; // request including body (POST...)
+   std::function<void(const std::string& key, const std::string& value)>& SetResponseHeader; // to be added to result string
+   fs::path& path;
+
+   CGIContext(std::function<std::string(const std::string& key)>& p_GetServerParam,
+              std::function<std::string(const std::string& key)>& p_GetRequestParam,
+              std::function<void(const std::string& key, const std::string& value)>& p_SetResponseHeader,
+              fs::path& p_path
+              )
+    : GetServerParam(p_GetServerParam)
+    , GetRequestParam(p_GetRequestParam)
+    , SetResponseHeader(p_SetResponseHeader)
+    , path(p_path)
+  {
+  }
+ };
+
+ // Return a reasonable mime type based on the extension of a file.
+ std::string mime_type(fs::path path)
+ {
+  using boost::algorithm::iequals;
+  auto const ext = [&path]
+  {
+   size_t pos = path.string().rfind(".");
+   if (pos == std::string::npos)
+    return std::string{};
+   return path.string().substr(pos);
+  }();
+  if(iequals(ext, ".htm"))  return "text/html"; // TODO: unordered_map
+  if(iequals(ext, ".html")) return "text/html";
+  if(iequals(ext, ".php"))  return "text/html";
+  if(iequals(ext, ".css"))  return "text/css";
+  if(iequals(ext, ".txt"))  return "text/plain";
+  if(iequals(ext, ".js"))   return "application/javascript";
+  if(iequals(ext, ".json")) return "application/json";
+  if(iequals(ext, ".xml"))  return "application/xml";
+  if(iequals(ext, ".swf"))  return "application/x-shockwave-flash";
+  if(iequals(ext, ".flv"))  return "video/x-flv";
+  if(iequals(ext, ".png"))  return "image/png";
+  if(iequals(ext, ".jpe"))  return "image/jpeg";
+  if(iequals(ext, ".jpeg")) return "image/jpeg";
+  if(iequals(ext, ".jpg"))  return "image/jpeg";
+  if(iequals(ext, ".gif"))  return "image/gif";
+  if(iequals(ext, ".bmp"))  return "image/bmp";
+  if(iequals(ext, ".ico"))  return "image/vnd.microsoft.icon";
+  if(iequals(ext, ".tiff")) return "image/tiff";
+  if(iequals(ext, ".tif"))  return "image/tiff";
+  if(iequals(ext, ".svg"))  return "image/svg+xml";
+  if(iequals(ext, ".svgz")) return "image/svg+xml";
+  return "application/text";
+ }
+
+ typedef boost::coroutines2::coroutine<std::string> coro_t;
+
+ // returns true iff std::string is empty or contains newline
+ bool isEmpty(const std::string& s)
+ {
+  return s.empty() || s == "\r" || s == "\n"s || s == "\r\n"s;
+ }
+
+ void trimLinebreak(std::string& s)
+ {
+  size_t pos = s.find_last_not_of("\r\n");
+  if (pos != s.npos)
+   s = s.substr(0, pos + 1);
+ }
+
+ std::unordered_map<std::string, std::function<void(std::string&, CGIContext&)>> headerMap {
+  { "Content-Type", [](std::string& v, CGIContext& c){ c.SetResponseHeader("content_type", v); } }
+ };
+
+ void handleHeader(const std::string& s, CGIContext& context)
+ {
+  size_t pos = s.find(": ");
+  if (pos == s.npos)
+   return;
+
+  std::string key {s.substr(0, pos)};
+  std::string value {s.substr(pos + 2)};
+
+
+  auto it {headerMap.find(key)};
+  if (it == headerMap.end())
+   std::cout << "Warning: Unhandled CGI header: " << s << std::endl;
+  else
+   it->second(value, context);
+ }
+
+ void setCGIEnvironment(bp::environment& env, CGIContext& c)
+ {
+  std::string authorization {c.GetRequestParam("authorization")};
+  if (!authorization.empty())
+   env["AUTH_TYPE"] = c.GetRequestParam("authorization");
+
+  env["CONTENT_LENGTH"] = c.GetRequestParam("content_length");
+  env["CONTENT_TYPE"] = c.GetRequestParam("content_type");
+  env["GATEWAY_INTERFACE"] = gateway_interface;
+
+  std::string target {c.GetRequestParam("target")};
+  size_t query_pos {target.find("?")};
+  std::string query;
+  if (query_pos != target.npos) {
+   query = target.substr(0, query_pos);
+   target = target.substr(query_pos + 1);
+  }
+
+  env["PATH_INFO"] = target;
+  env["PATH_TRANSLATED"] = c.path.string();
+  env["QUERY_STRING"] = query;
+  env["REMOTE_ADDR"] = "";
+  env["REMOTE_HOST"] = "";
+  env["REMOTE_IDENT"] = "";
+  env["REMOTE_USER"] = "";
+  env["REQUEST_METHOD"] = c.GetRequestParam("method");
+  env["SCRIPT_NAME"] = c.GetRequestParam("rel_target");
+  env["SERVER_NAME"] = c.GetRequestParam("host");
+  env["SERVER_PORT"] = c.GetServerParam("port");
+  env["SERVER_PROTOCOL"] = c.GetRequestParam("http_version");
+  env["SERVER_SOFTWARE"] = c.GetServerParam("version");
+
+  env["HTTP_ACCEPT"] = c.GetRequestParam("http_accept");
+  env["HTTP_ACCEPT_CHARSET"] = c.GetRequestParam("http_accept_charset");
+  env["HTTP_ACCEPT_ENCODING"] = c.GetRequestParam("http_accept_encoding");
+  env["HTTP_ACCEPT_LANGUAGE"] = c.GetRequestParam("http_accept_language");
+  env["HTTP_CONNECTION"] = c.GetRequestParam("http_connection");
+  env["HTTP_HOST"] = c.GetRequestParam("http_host");
+  env["HTTP_USER_AGENT"] = c.GetRequestParam("http_user_agent");
+ }
+
+ std::string executeFile(const fs::path& filename, CGIContext& context)
+ {
+  bp::opstream is_in;
+  bp::ipstream is_out;
+
+  //std::cout << "Executing " << filename << std::endl;
+  
+  bp::environment env {boost::this_process::environment()};
+  setCGIEnvironment(env, context);
+
+  bp::child child(filename.string(), env, (bp::std_out & bp::std_err) > is_out, bp::std_in < is_in);
+
+  is_in << context.GetRequestParam("body");
+
+  std::string output;
+  std::string line;
+
+  // TODO: C++20 coroutine 
+  coro_t::push_type processLine( [&](coro_t::pull_type& in){
+                                std::string line;
+                                // read header lines
+                                while (in && !isEmpty(line = in.get())) {
+                                 trimLinebreak(line);
+                                 handleHeader(line, context);
+                                 in();
+                                }
+                                
+                                // read empty line
+                                if (!isEmpty(line))
+                                 throw std::runtime_error("Missing empty line between CGI header and body");
+                                if (in)
+                                 in();
+
+                                // read remainder
+                                while (in) {
+                                 line = in.get();
+                                 output += line + '\n';
+                                 in();
+                                }
+
+                                throw std::runtime_error("Input missing on processing CGI body");
+  });
+
+  while (child.running() && std::getline(is_out, line)) {
+   processLine(line);
+  }
+
+  child.wait();
+
+  return output;
+ }
+
+ // Used to return errors by generating response page and HTTP status code
+ std::string HttpStatus(std::string status, std::string message, std::function<plugin_interface_setter_type>& SetResponseHeader)
+ {
+  SetResponseHeader("status", status);
+  SetResponseHeader("content_type", "text/html");
+  return status + " " + message;
+ }
+
+} // anonymous namespace
+
+std::string cgi_plugin::name()
+{
+ return "cgi";
+}
+
+cgi_plugin::cgi_plugin()
+{
+ //std::cout << "Plugin constructor" << std::endl;
+}
+
+cgi_plugin::~cgi_plugin()
+{
+ //std::cout << "Plugin destructor" << std::endl;
+}
+
+std::string cgi_plugin::generate_page(
+  std::function<std::string(const std::string& key)>& GetServerParam,
+  std::function<std::string(const std::string& key)>& GetRequestParam, // request including body (POST...)
+  std::function<void(const std::string& key, const std::string& value)>& SetResponseHeader // to be added to result string
+)
+{
+ try {
+  // Make sure we can handle the method
+  std::string method {GetRequestParam("method")};
+  if (method != "GET" && method != "HEAD")
+   return HttpStatus("400", "Unknown HTTP method", SetResponseHeader);
+
+  // Request path must not contain "..".
+  std::string rel_target{GetRequestParam("rel_target")};
+  size_t query_pos{rel_target.find("?")};
+  if (query_pos != rel_target.npos)
+   rel_target = rel_target.substr(0, query_pos);
+
+  std::string target{GetRequestParam("target")};
+  if (rel_target.find("..") != std::string::npos) {
+   return HttpStatus("400", "Illegal request: "s + target, SetResponseHeader);
+  }
+
+  // Build the path to the requested file
+  std::string doc_root{GetRequestParam("doc_root")};
+  fs::path path {fs::path{doc_root} / rel_target};
+  if (target.size() && target.back() != '/' && fs::is_directory(path)) {
+   std::string location{GetRequestParam("location") + "/"s};
+   SetResponseHeader("location", location);
+   return HttpStatus("301", "Correcting directory path", SetResponseHeader);
+  }
+
+  try {
+    if (!fs::is_regular_file(path)) {
+     return HttpStatus("500", "Bad Script: "s + rel_target, SetResponseHeader);
+    }
+  } catch (const std::exception& ex) {
+    return HttpStatus("500", "Bad file access: "s + rel_target, SetResponseHeader);
+  }
+
+  try {
+   if ((fs::status(path).permissions() & fs::perms::others_exec) == fs::perms::none) {
+     return HttpStatus("500", "Script not executable: "s + rel_target, SetResponseHeader);
+   }
+  } catch (const std::exception& ex) {
+    return HttpStatus("500", "Bad file status access: "s + rel_target, SetResponseHeader);
+  }
+
+  SetResponseHeader("content_type", mime_type(path));
+
+  CGIContext context(GetServerParam, GetRequestParam, SetResponseHeader, path);
+
+  try {
+   return executeFile(path, context);
+  } catch (const std::runtime_error& ex) {
+   return HttpStatus("404", "Not found: "s + GetRequestParam("target"), SetResponseHeader);
+  } catch (const std::exception& ex) {
+   return HttpStatus("500", "Internal Server Error: "s + ex.what(), SetResponseHeader);
+  }
+
+ } catch (const std::exception& ex) {
+  return HttpStatus("500", "Unknown Error: "s + ex.what(), SetResponseHeader);
+ }
+}
+