Date: Tue, 08 Feb 2022 09:41:28 +0100 From: Alexander Leidinger <Alexander@leidinger.net> To: hackers@freebsd.org Subject: Behavior of /dev/pts in a jail? Message-ID: <20220208094128.Horde.LqeAS3LDe4RHYSV3IH2XY96@webmail.leidinger.net>
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Hi, I'm debugging a problem with gnupg on -current (as of Jan 20, but I see this problem since several months). The pinentry-tty program fails to ask for a PW. One of the gnupg authors found a bug which makes the pinentry-tty program segfault (fixed in v1.2.0), but this doesn't solve the problem (converts the segfault into a error output). We narrowed the problem down to gpg-agent not being able to see anything in /dev/pts and as such not being able to open my tty. So: - a jail with devfs - login into the jail via "jexec <id> zsh" followed by "su - <user>" - a shell-wrapper for pinentry-tty which "ls -la /dev/pts" into a logfile - in the user-zsh inside the jail, I can see /dev/pts/2 (my tty) as being rw for me in "ls -la /dev/pts" with the same uid as my user (the user id inside the jail and the user id to which I ssh-ed on the jail-host are the same) - executing gpg in this same shell in a way which is supposed to ask for a PW results in the pinentry-wrapper being called and /dev/pts being completely empty in the ls output in the logfile -> no PW being asked - doing a ls of /dev/pts afterwards inside the shell still shows /dev/pts/2 Neither gpg nor gpg-agent are SUID. This behavior surprises me. The non-root shell I use inside the jail sees /dev/pts/2. This shell forks gpg which forks gpg-agent which forks pinentry-tty. As such I would expect /dev/pts/2 being visible to pinentry-tty. For me either this entry in the FS should be visible to all processes of this user, or to none. What am I missing here? Gnupg ticket: https://dev.gnupg.org/T5814 Workaround if someone has the same problem: "gpg --pinentry-mode=loopback ..." Bye, Alexander. -- http://www.Leidinger.net Alexander@Leidinger.net: PGP 0x8F31830F9F2772BF http://www.FreeBSD.org netchild@FreeBSD.org : PGP 0x8F31830F9F2772BF
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