Add Lua interface to HTTPFetchRequest

This allows mods to perform both asynchronous and synchronous HTTP
requests. Mods are only granted access to HTTP APIs if either mod
security is disabled or if they are whitelisted in any of the
the secure.http_mods and secure.trusted_mods settings.

Adds httpfetch_caller_alloc_secure to generate random, non-predictable
caller IDs so that lua mods cannot spy on each others HTTP queries.

1 files changed, 54 insertions, 0 deletions

diff --git a/doc/lua_api.txt b/doc/lua_api.txt
index 2df0cac7c..aee3674d0 100644
--- a/doc/lua_api.txt
+++ b/doc/lua_api.txt
@@ -2330,6 +2330,26 @@ These functions return the leftover itemstack.
     * If `lua_num_indent_spaces` is a nonzero number and `format` is "lua", the Lua code generated
     * will use that number of spaces as indentation instead of a tab character.
 
+### HTTP Requests:
+* `minetest.request_http_api()`:
+    * returns `HTTPApiTable` containing http functions if the calling mod has been granted
+      access by being listed in the `secure.http_mods` or `secure.trusted_mods` setting,
+      otherwise returns `nil`.
+    * The returned table contains the functions `fetch`, `fetch_async` and `fetch_async_get`
+      described below.
+    * Only works at init time.
+    * Function only exists if minetest server was built with cURL support.
+    * **DO NOT ALLOW ANY OTHER MODS TO ACCESS THE RETURNED TABLE, STORE IT IN
+      A LOCAL VARIABLE!**
+* `HTTPApiTable.fetch(HTTPRequest req, callback)`
+    * Performs given request asynchronously and calls callback upon completion
+    * callback: `function(HTTPRequestResult res)`
+    * Use this HTTP function if you are unsure, the others are for advanced use.
+* `HTTPApiTable.fetch_async(HTTPRequest req)`: returns handle
+    * Performs given request asynchronously and returns handle for `minetest.http_fetch_async_get`
+* `HTTPApiTable.fetch_async_get(handle)`: returns HTTPRequestResult
+    * Return response data for given asynchronous HTTP request
+
 ### Misc.
 * `minetest.get_connected_players()`: returns list of `ObjectRefs`
 * `minetest.hash_node_position({x=,y=,z=})`: returns an 48-bit integer
@@ -3837,3 +3857,37 @@ Definition tables
         playername = "singleplayer"
     --  ^ Playername is optional, if specified spawns particle only on the player's client
     }
+
+### `HTTPRequest` definition (`http_fetch`, `http_fetch_async`)
+
+    {
+        url = "http://example.org",
+        timeout = 10,
+     -- ^ Timeout for connection in seconds. Default is 3 seconds.
+        post_data = "Raw POST request data string" OR { field1 = "data1", field2 = "data2" },
+     -- ^ Optional, if specified a POST request with post_data is performed.
+     -- ^ Accepts both a string and a table. If a table is specified, encodes table
+     -- ^ as x-www-form-urlencoded key-value pairs.
+     -- ^ If post_data ist not specified, a GET request is performed instead.
+        user_agent = "ExampleUserAgent",
+     -- ^ Optional, if specified replaces the default minetest user agent with given string
+        extra_headers = { "Accept-Language: en-us", "Accept-Charset: utf-8" },
+     -- ^ Optional, if specified adds additional headers to the HTTP request. You must make sure
+     -- ^ that the header strings follow HTTP specification ("Key: Value").
+        multipart = boolean
+     -- ^ Optional, if true performs a multipart HTTP request. Default is false.
+    }
+
+### `HTTPRequestResult` definition (`http_fetch` callback, `http_fetch_async_get`)
+
+    {
+        completed = true,
+     -- ^ If true, the request has finished (either succeeded, failed or timed out)
+        succeeded = true,
+     -- ^ If true, the request was succesful
+        timeout = false,
+     -- ^ If true, the request timed out
+        code = 200,
+     -- ^ HTTP status code
+        data = "response"
+    }