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| 15:01 |
kilbith |
this is an interesting lib for MT: https://github.com/yuri/lua-colors/blob/master/lua/colors.lua |
| 15:01 |
kilbith |
and it is MIT licensed. |
| 15:19 |
MTDiscord |
<luatic> meh |
| 15:45 |
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| 16:16 |
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| 17:17 |
erlehmann |
rubenwardy, is it possible to push updates to minetest game via contentdb? |
| 17:17 |
rubenwardy |
If they install it via ContentDB, yes |
| 17:17 |
rubenwardy |
Otherwise no |
| 17:17 |
erlehmann |
rubenwardy, i am asking because of https://github.com/minetest/minetest_game/blob/5875820542c739ff223a8a6ef8a3e698685b6405/mods/fire/init.lua#L170 |
| 17:18 |
erlehmann |
you see, the minetest.find_nodes_in_area() call there is exploitable by griefers |
| 17:18 |
erlehmann |
they can crash or hang the server |
| 17:18 |
erlehmann |
i am working on a lua workaround |
| 17:19 |
erlehmann |
but the question is how to get the lua wrapper for minetest.find_nodes_in_area() to the people |
| 17:19 |
erlehmann |
rubenwardy, so you'd say it makes sense to put the minetest.find_nodes_in_area() wrapper in minetest_game once it is finished? |
| 17:21 |
erlehmann |
btw, it seems from a very lazy review, that there are a bunch of other bugs lurking in the space between MAX_MAPGEN_LIMIT and the limits of s16, that were never found |
| 17:23 |
erlehmann |
therefore, in the interest of stability, i want to urge everyone who works on stuff that takes coordinates as s16 or whatever to make sure those function work up to the limits of the underlying data type, not to the limits of “what makes sense in normal usage” |
| 17:23 |
erlehmann |
griefers do not care about normal usage |
| 17:24 |
erlehmann |
they just want to destroy & crash/hang servers |
| 17:26 |
MTDiscord |
<luatic> In that spirit, you probably shouldn't output warnings |
| 17:33 |
rubenwardy |
MTG is released at the same time as the engine |
| 17:33 |
rubenwardy |
Makes sense to just fix the engine |
| 17:35 |
erlehmann |
rubenwardy, ok let me say it that way: at the moment cora & me publish our reproduction on how to do it, everyone can see in our bug tracker how to crash every current minetest server that uses mcl2, mcl5 or minetest game, except the ones running mineclonia or games that do not copy code from minetest game |
| 17:36 |
erlehmann |
and ofc a bug fix needs to have instructions how to verify that it works |
| 17:36 |
erlehmann |
so not publishing it is not an option |
| 17:45 |
sfan5 |
you seem to be missing a crucial step, how do people get out of bounds? |
| 17:45 |
erlehmann |
sfan5 minetest for good reason does not limit falling speed |
| 17:46 |
erlehmann |
(don't limit it now that i have said it, you'll break things) |
| 17:46 |
sfan5 |
oh yea I forgot |
| 17:46 |
erlehmann |
i.e. it is trivial to just fall out of the world |
| 17:46 |
erlehmann |
and if you hit exactly the right cordinates, shit happens |
| 17:47 |
erlehmann |
the thing is, i think the only way to prevent shit happening is to define one boundary and make everything in it well-behaved and everything out of it illegal. naturally, that would be s16. |
| 17:48 |
erlehmann |
all other ways might work, but create additional boundaries (i.e. mod code needs to check more than if a value is out of s16) |
| 17:48 |
erlehmann |
and the more boundaries you have, the more trouble |
| 17:50 |
erlehmann |
i mean, the thing with player positions being float vectors that then crash the server if you give them to a lua function is an example of a boundary where one part of the code checks it (and crashes), but the other one does not |
| 17:50 |
erlehmann |
oh, also ppl are already abusing “teleport player to 0,0,0 if coordinates are illegal” bugfixes to travel far on servers |
| 17:51 |
erlehmann |
just in case anyone thinks that is a solution |
| 17:52 |
rubenwardy |
We have patch releases for thid |
| 17:52 |
erlehmann |
thid? |
| 17:52 |
erlehmann |
sfan5, other ways to get out of bounds usually involve attachment/unattachment shenanigans, flinging a player with high speed in some direction |
| 17:52 |
erlehmann |
etc. pp. |
| 17:53 |
erlehmann |
there are a lot of issues and i think papering over each of those is a lot more work than just defining one boundary and then run unit tests to ensure it is well behaved |
| 17:54 |
erlehmann |
there are only about 65536³ = 281474976710656 possible v3s16, that means it is possible to check them all in unit tests |
| 17:54 |
sfan5 |
before I leave for the evening I just want to point out that we have never done a patch release for bugs like this |
| 17:55 |
erlehmann |
well i am thinking long term |
| 17:55 |
erlehmann |
basically, i want minetest servers to not crash, even with the stupidest possible mod code |
| 17:56 |
erlehmann |
and fixing all the integer overflows would go a long way towards it |
| 17:56 |
erlehmann |
and making sure that all coordinate conversions roundtrip |
| 17:57 |
erlehmann |
i have abandoned my plan of client-sent server mods btw |
| 17:57 |
erlehmann |
clearly fixing the holes is much more important |
| 17:57 |
erlehmann |
bc the bad ppl are stupid, but not that stupid |
| 18:22 |
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| 19:00 |
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| 19:57 |
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| 19:58 |
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| 21:53 |
MTDiscord |
<luatic> "basically, i want minetest servers to not crash, even with the stupidest possible mod code" - a logging error handler would allow for this, but I think it's a bad idea; erroring is preferrable over working with an inconsistent state |
| 21:53 |
erlehmann |
luatic, what is an inconsistent state? |
| 21:54 |
MTDiscord |
<luatic> Consider a = 1 + trueas "most stupid mod code". What should the value of a be afterwards, if you're not going to error? |
| 21:54 |
erlehmann |
oh no, i mean different stuff |
| 21:54 |
MTDiscord |
<luatic> "there are only about 65536³ = 281474976710656 possible v3s16, that means it is possible to check them all in unit tests" - possible but not reasonable; it would take way too long - only edge cases should be checked, fuzzing should be used |
| 21:55 |
erlehmann |
you only need to test the boundaries, but come on, computers are fast. |
| 21:55 |
MTDiscord |
<luatic> Not that fast |
| 21:55 |
MTDiscord |
<luatic> My rule of thumb: It's fine as long as it's roughly about 10^9 (10^12 tops) |
| 21:56 |
erlehmann |
regarding stupid mod code: for example, it is known that the lua mapgen is very racy. essentially, you can not be sure that stuff you do in lua mapgen is not deleted by a process that kay27 calls “mapgen griefing”. |
| 21:56 |
erlehmann |
there exist a lot of lua workarounds that essentially a) place stuff b) try to figure out if it actually got placed |
| 21:57 |
erlehmann |
so they try it again |
| 21:58 |
erlehmann |
this is of course a bit stupid, but what should they do? i am of the impression almost everyone thinks thread safety and signed integer overflow are not *that* of a big deal (until they cause crashes) |
| 21:59 |
erlehmann |
i have over the time seen a lot of mapgen weirdness (up to “a stone cube hangs in the sky”) that can be explained very well by the mapgen being unreliable |
| 22:00 |
erlehmann |
i am not saying the way mod authors deal with it is nice, but the code is out there |
| 22:01 |
erlehmann |
tbh the first time kay27 brought this up i thought he was seeing ghosts |
| 22:01 |
erlehmann |
because his workarounds are *really* crazy |
| 22:09 |
Extex |
Came up with an idea yesterday, add an optional wherein to .register_decoration |
| 22:10 |
Extex |
And by doing that you can say for example: in stone and on air |
| 22:10 |
Extex |
To make roof decorations |
| 22:20 |
erlehmann |
OH LOL |
| 22:23 |
erlehmann |
sfan5 i just found out that for a crash-related test case i might need an area that is guaranteed to *NEVER* be touched by mapgen but other stuff should work. does such an area even exist? can i exclude mapgen from some mapblocks maybe using lua? |
| 22:24 |
erlehmann |
“use singlenode and always create a new world” is a bit cumbersome (then the test case can not be run on existing worlds) |
| 22:43 |
erlehmann |
nice, while writing my test case i found another boundary bug |
| 23:40 |
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