[BRLTTY] Console open error on recent Arch Linux

[Aura Kelloniemi]

Hello,

I'm running BRLTTY as a systemd service under current Arch Linux with kernel
6.16.8-arch3-1. BRLTTY fails to open many devices it tries as the permissions
are not liberal enough.

BRLTTY also tries to create device nodes in /run/brltty, which fails. I really
don't want programs to be able to create devices under /run/ so I'm happy this
fails, and I would prefer BRLTTY not trying it at all.

I have not tampered the udev rules provided by Arch. Here are the permissions
of all device files whic BRLTTY tries to open during its execution:

# grep --only-matching '/dev/[a-zA-Z0-9/]*' brltty-priv-error.log | sort -u | xargs ls -ld
drwxr-xr-x  10 root root       200 24. 9. 08:18 /dev/bus/usb
crw-------   1 root root  244,   0 24. 9. 08:18 /dev/hidraw0
crw-------   1 root root  244,   1 24. 9. 08:18 /dev/hidraw1
crw-------   1 root root  244,  10 24. 9. 08:18 /dev/hidraw10
crw-------   1 root root  244,  11 24. 9. 08:18 /dev/hidraw11
crw-------+  1 root root  244,  12 24. 9. 08:31 /dev/hidraw12
crw-------   1 root root  244,  13 24. 9. 08:18 /dev/hidraw13
crw-------   1 root root  244,  14 24. 9. 08:18 /dev/hidraw14
crw-------   1 root root  244,   2 24. 9. 08:18 /dev/hidraw2
crw-------   1 root root  244,   3 24. 9. 08:18 /dev/hidraw3
crw-------   1 root root  244,   4 24. 9. 08:18 /dev/hidraw4
crw-------   1 root root  244,   5 24. 9. 08:18 /dev/hidraw5
crw-------   1 root root  244,   6 24. 9. 08:18 /dev/hidraw6
crw-------   1 root root  244,   7 24. 9. 08:18 /dev/hidraw7
crw-------+  1 root root  244,   8 24. 9. 08:31 /dev/hidraw8
crw-------   1 root root  244,   9 24. 9. 08:18 /dev/hidraw9
crw-rw----   1 root input  13,  63 24. 9. 08:18 /dev/input/mice
crw-rw----   1 root audio 116,   1 24. 9. 08:18 /dev/snd/seq
crw-------   1 root tty     4,   0 24. 9. 08:31 /dev/tty0
crw-------   1 aura tty     4,   1 24. 9. 08:31 /dev/tty1
crw-rw----   1 root uucp    4,  64 24. 9. 08:18 /dev/ttyS0
crw-------   1 root root   10, 223 24. 9. 08:18 /dev/uinput
crw-rw----   1 root tty     7,   1 24. 9. 08:18 /dev/vcs1
crw-rw----   1 root tty     7, 128 24. 9. 08:18 /dev/vcsa
crw-rw----   1 root tty     7,  64 24. 9. 08:18 /dev/vcsu

Based on this, it seems that BRLTTY would need to run as root to be able to
open the console. This list also raises some questions: why BRLTTY either
tries to open or checks permissions of

- /dev/snd/seq even though I have alert tunes and speech disabled
- /dev/input/... even though I have keyboard table disabled
- /dev/uinput even though I have keyboard table disabled
- /dev/ttyS0 even though I have not configured any serial displays
- /dev/bus/usb even though it did not try to connect to any USB display?

The full log file is attached.

I fixed the issue by supplying --stay-privileged to BRLTTY and changing the
user from brltty to root. This of course is not an ideal solution. I don't
know why Arch developers have decided on such a strict device permissions, but
I suppose they had some reasons for doing it. Do you have any suggestions for
solving the issue?

Thanks in advance!

-- 
Aura Kelloniemi

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