Awesome, I'm trying to do this with Elektron machines, the Digitakt.
Remote code execution via MIDI messages
61–70 of 86 posts
Re: Remote code execution via MIDI messages
#62Earlier quoted context omitted.
I wish it was somehow possible to perform a piece of music that would cause remote code execution. It’d be so cool to plug in a MIDI keyboard, play an Am6,9/G# and have it open a terminal window with root access.
That doesn't make much sense as note on and note off messages are very simple and you can't insert arbitrary bytes with them, unless maybe you use some very particular run mode.
Note on/off are just messages. We by convention map them to notes, but note 69 is A-440 on most keyboards, but you could see note 69 and play a C instead (this is somewhat common - have the computer transpose so you can play with others who play the music in a different key - better players can do this in their head but it is not a universal skill even with great players)
There is no reason you can't take a sequence of notes and do something else - pop up a root window for example. It isn't normally done because it would confuse everyone for no reason. (IIRC The original MIDI spec from the 1980s didn't have conventions of nearly as much and some midi devices did really weird things from note commands)
Re: Remote code execution via MIDI messages
#63Earlier quoted context omitted.
Oh there definitely is some MIDI device out there that will get a buffer overrun from a particular set of just regular note inputs. Maybe 11 notes at once due to the programmer thinking "humans have only 10 fingers, a static array of 10 elements is enough to hold all notes currently playing".
More notes or voices playing than the player has fingers is quite common, a note doesn't stop just because you let go of the key. Sometimes you want it to ring out so most synthesizers handle that case. Some even let you configure the behaviour, for example you could reallocate the longest playing note or the closest note.
Many synthesizers have limits on how many sounds they can support. Midi was originally started because 1970's (analog) synthesizers could only produce one sound and so they wanted a way to have several synthesizers connected together. Before midi was finished synthesizers (now digital) could play more than one note. Though hardware limitations (not just software) didn't support infinite notes and so until around 2000 that synthesizers could generally play enough notes that players wouldn't run out in the real world.
Re: Remote code execution via MIDI messages
#64> Now, we have to get a little philosophical here. In my eyes, RE is like a game of minesweeper. You start with an empty field not knowing the state of any of the cells, i.e. not knowing whether each individual cell contains a landmine or not. When you discover the state of a cell, you have the context to deduce the state of its neighbor cells. In minesweeper, you don’t have a particular direction in which you progre…
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Re: Remote code execution via MIDI messages
#65[dead]
Re: Remote code execution via MIDI messages
#66This is such a ludicrous premise, I'm amazed you pulled it off. You mention "another packing optimization". I'm wondering, how are you transferring frames? The dot matrix is eight 7x5 characters, i.e. 280 bits in total, which amounts to 40 7-bit groups per frame. You seem to be using twice that space in transmission, is it wasted on some control data or is the transmission just slightly suboptimal?
Thanks! The dot matrix is actually eight 5x8 characters, or 320 bits in total. I'm packing those 320 bits into the the 4 bits per byte that are available to us in this shell protocol. Plus, another 9 bytes for the packet header and footer. Looks like I wrote 92 in the article, I must have miscalculated that. I'm not using the full 7 bits because figuring out a way to do so turned out to be way too hard for me, so I o…
Another option might be to modify the baud rate of the MIDI interface. MIDI is terribly slow at 1M/32 bps, and most UARTs can go at least 115200. That would also mean changing the baud rate on your PC software at that point in transmission, and would not allow a standard MIDI file to be used.
Re: Remote code execution via MIDI messages
#67Of course it is SysEx. SysEx is to standard MIDI what inline assembler is to Python. A world of undocumented proprietary stuff lurks within just about every MIDI device !
SysEx is awesome. I'm quite sad modern synths seem to use it less and less (Roland!!!). Though Behringer is still quite good with it. E.g. their Deepmind can be pretty much 100% programmed with it, on top of already good MIDI CC scope.
Roland using less SysEx ? Here is a 26 pages PDF full of unofficial TB-3 SysEx documented by Dope Robot: https://www.doperobot.com/TB-3%20Sysex%20Implementation%20v1... - Roland's official documentation just scratches the surface.
Re: Remote code execution via MIDI messages
#68Re: Remote code execution via MIDI messages
#69Earlier quoted context omitted.
More notes or voices playing than the player has fingers is quite common, a note doesn't stop just because you let go of the key. Sometimes you want it to ring out so most synthesizers handle that case. Some even let you configure the behaviour, for example you could reallocate the longest playing note or the closest note.
Many synthesizers have limits on how many sounds they can support. Midi was originally started because 1970's (analog) synthesizers could only produce one sound and so they wanted a way to have several synthesizers connected together. Before midi was finished synthesizers (now digital) could play more than one note. Though hardware limitations (not just software) didn't support infinite notes and so until around 2000…
The companies that came together to make MIDI all had analog polysynths capable of true polyphony before the MIDI standard was even finished. (distinct osc/amp/filter outputs per note and not just paraphonic synths that shared AMP/Filter circuits between OSCs)
MIDI was more about unifying the entire studio of synths, samplers, drum machines, and recording equipment. And creating interoperability between various manufacturers of music equipment. It was a solution to the multiple control voltage standards that predated it and made it troublesome to tie equipment together.
Re: Remote code execution via MIDI messages
#70On the off chance any of the HN crowd is in Armenia: Porta will be giving a talk about this on January 10th at the Hacker Embassy. You should definitely come: https://t.me/hackerembassy/17