HttpInspector: new plugin for developers to inspect KOReader (#11457)

Can be used to inspect the state of the objects in
a running KOReader.
It can also be used to execute actions (like the ones
available to associate to a gesture) with HTTP requests
from a remote computer/devices/gadgets.
The TCP server side is provided either with a new
ZeroMQ StreamMessageQueueServer (thanks bneo99),
or with a LuaSocket based SimpleTCPServer.
Minor UIManager tweak to avoid uneeded inputevent
when such a ZeroMQ module is running.

frontend/ui/message/simpletcpserver.lua

@@ -0,0 +1,68 @@
+local socket = require("socket")
+local logger = require("logger")
+
+-- Reference:
+-- https://lunarmodules.github.io/luasocket/tcp.html
+
+-- Drop-in alternative to streammessagequeueserver.lua, using
+-- LuaSocket instead of ZeroMQ.
+-- This SimpleTCPServer is still tied to HTTP, expecting lines of headers,
+-- a blank like marking the end of the input request.
+
+local SimpleTCPServer = {
+    host = nil,
+    port = nil,
+}
+
+function SimpleTCPServer:new(o)
+    o = o or {}
+    setmetatable(o, self)
+    self.__index = self
+    if o.init then o:init() end
+    return o
+end
+
+function SimpleTCPServer:start()
+    self.server = socket.bind(self.host, self.port)
+    self.server:settimeout(0.01) -- set timeout (10ms)
+    logger.dbg("SimpleTCPServer: Server listening on port " .. self.port)
+end
+
+function SimpleTCPServer:stop()
+    self.server:close()
+end
+
+function SimpleTCPServer:waitEvent()
+    local client = self.server:accept() -- wait for a client to connect
+    if client then
+        -- We expect to get all headers in 100ms. We will block during this timeframe.
+        client:settimeout(0.1, "t")
+        local lines = {}
+        while true do
+            local data = client:receive("*l") -- read a line from input
+            if not data then -- timeout
+                client:close()
+                break
+            end
+            if data == "" then -- proper empty line after request headers
+                table.insert(lines, data) -- keep it in content
+                data = table.concat(lines, "\r\n")
+                logger.dbg("SimpleTCPServer: Received data: ", data)
+                -- Give us more time to process the request and send the response
+                client:settimeout(0.5, "t")
+                self.receiveCallback(data, client)
+                    -- This should call SimpleTCPServer:send() to send
+                    -- the response and close this connection.
+            else
+                table.insert(lines, data)
+            end
+        end
+    end
+end
+
+function SimpleTCPServer:send(data, client)
+    client:send(data) -- send the response back to the client
+    client:close() -- close the connection to the client
+end
+
+return SimpleTCPServer

frontend/ui/message/streammessagequeueserver.lua

@@ -0,0 +1,86 @@
+local ffi = require("ffi")
+local logger = require("logger")
+local MessageQueue = require("ui/message/messagequeue")
+
+local _ = require("ffi/zeromq_h")
+local czmq = ffi.load("libs/libczmq.so.1")
+local C = ffi.C
+
+local StreamMessageQueueServer = MessageQueue:extend{
+    host = nil,
+    port = nil,
+}
+
+function StreamMessageQueueServer:start()
+    self.context = czmq.zctx_new()
+    self.socket = czmq.zsocket_new(self.context, C.ZMQ_STREAM)
+    self.poller = czmq.zpoller_new(self.socket, nil)
+    local endpoint = string.format("tcp://%s:%d", self.host, self.port)
+    logger.dbg("StreamMessageQueueServer: Binding to endpoint", endpoint)
+    local rc = czmq.zsocket_bind(self.socket, endpoint)
+    -- If success, rc is port number
+    if rc == -1 then
+        logger.err("StreamMessageQueueServer: Cannot bind to ", endpoint)
+    end
+end
+
+function StreamMessageQueueServer:stop()
+    if self.poller ~= nil then
+        czmq.zpoller_destroy(ffi.new('zpoller_t *[1]', self.poller))
+    end
+    if self.socket ~= nil then
+        czmq.zsocket_destroy(self.context, self.socket)
+    end
+    if self.context ~= nil then
+        czmq.zctx_destroy(ffi.new('zctx_t *[1]', self.context))
+    end
+end
+
+function StreamMessageQueueServer:handleZframe(frame)
+    local size = czmq.zframe_size(frame)
+    local data = nil
+    if size > 0 then
+        local frame_data = czmq.zframe_data(frame)
+        if frame_data ~= nil then
+            data = ffi.string(frame_data, size)
+        end
+    end
+    czmq.zframe_destroy(ffi.new('zframe_t *[1]', frame))
+    return data
+end
+
+function StreamMessageQueueServer:waitEvent()
+    local request, id
+    while czmq.zpoller_wait(self.poller, 0) ~= nil do
+        -- See about ZMQ_STREAM and these 2 frames at http://hintjens.com/blog:42
+        local id_frame = czmq.zframe_recv(self.socket)
+        if id_frame ~= nil then
+            id = id_frame
+        end
+
+        local frame = czmq.zframe_recv(self.socket)
+        if frame ~= nil then
+            local data = self:handleZframe(frame)
+            if data then
+                logger.dbg("StreamMessageQueueServer: Received data: ", data)
+                request = data
+            end
+        end
+    end
+    if self.receiveCallback and request ~= nil then
+        self.receiveCallback(request, id)
+    end
+end
+
+function StreamMessageQueueServer:send(data, id_frame)
+    czmq.zframe_send(ffi.new('zframe_t *[1]', id_frame), self.socket, C.ZFRAME_MORE + C.ZFRAME_REUSE)
+    czmq.zmq_send(self.socket, ffi.cast("unsigned char*", data), #data, C.ZFRAME_MORE)
+    -- Note: We can't use czmq.zstr_send(self.socket, data), which would stop on the first
+    -- null byte in data (Lua strings can have null bytes inside).
+
+    -- Close connection
+    czmq.zframe_send(ffi.new('zframe_t *[1]', id_frame), self.socket, C.ZFRAME_MORE)
+    czmq.zmq_send(self.socket, nil, 0, 0)
+end
+
+return StreamMessageQueueServer

frontend/ui/uimanager.lua

@@ -1439,11 +1439,13 @@ end
 
 -- Process all pending events on all registered ZMQs.
 function UIManager:processZMQs()
-    if self._zeromqs[1] then
-        self.event_hook:execute("InputEvent")
-    end
+    local sent_InputEvent = false
     for _, zeromq in ipairs(self._zeromqs) do
         for input_event in zeromq.waitEvent, zeromq do
+            if not sent_InputEvent then
+                self.event_hook:execute("InputEvent")
+                sent_InputEvent = true
+            end
             self:handleInputEvent(input_event)
         end
     end

plugins/httpinspector.koplugin/_meta.lua

@@ -0,0 +1,6 @@
+local _ = require("gettext")
+return {
+    name = "httpinspector",
+    fullname = _("HTTP KOReader Inspector"),
+    description = _([[Allow browsing KOReader internal objects over HTTP. This is aimed at developers, and may pose some security risks. Only enable this on networks you can trust.]]),
+}