openssh unix dev - Jul 2014 - Read-only on /dev/tty causes ssh-add to show passwords when typed and ssh'ing to new hosts to fail

When permissions on /dev/tty are crw------- and owner root:root, ssh-add
will echo passwords to the terminal (sudo does not) and ssh fails with a
"Host key verification failed." error.

ssh -v -v -v provided a "debug1: read_passphrase: can't open /dev/tty:
Permission denied" which is how I figured out that /dev/tty had weird
permission issues.

I would have expected that error print without need the -v option and
ssh-add to fail so that my password would not show (or use another
method, if possible).

This happens with binaries compiled from source from openssh-6.6p1
obtained from
http://openbsd.mirrors.pair.com/OpenSSH/portable/openssh-6.6p1.tar.gz

Thank you,
Jim Keener

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On Fri, 18 Jul 2014, James Keener wrote:
> When permissions on /dev/tty are crw------- and owner root:root, ssh-add
> will echo passwords to the terminal (sudo does not) and ssh fails with a
> "Host key verification failed." error.
I would expect that ssh can't successfully issue termios calls to turn off
tty echo when /dev/tty isn't writable to the user. sudo will work because
it is setuid root.

There isn't much ssh can do with bad permissions on /dev/tty.

-d