hello, when dropbear server runs on host
$ echo hi | ssh user@host 'cat'
works as expected (so reading stdin works), but
$ echo hi | ssh user@host 'cat /proc/self/fd/0'
fails with EPERM (the open syscall in cat that is).
it seems the /proc file is user owned but it's a magic symlink
to a pipe that is owned by root so reopening it fails:
$ ssh user@host 'stat -L /proc/self/fd/0'
File: /proc/self/fd/0
Size: 0 Blocks: 0 IO Block: 4096 fifo
Device: bh/11d Inode: 7193 Links: 1
Access: (0600/prw-------) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2020-04-30 18:29:01.000000000
Modify: 2020-04-30 18:29:01.000000000
Change: 2020-04-30 18:29:01.000000000
i haven't seen this behaviour with openssh and affects some
scripts that use /dev/stdin, /dev/stdout, /dev/stderr
(which just point to /proc/self/fd/{1,2,3})
if there is a simple workaround i'd like to hear about it.
thanks
