On Tue, Jun 11, 2019 at 1:58 PM Josef Moellers <jmoellers@xxxxxxx> wrote:
On 11.06.19 12:45, Mantas Mikulėnas wrote:
> On Tue, Jun 11, 2019 at 1:08 PM Josef Moellers <jmoellers@xxxxxxx
> <mailto:jmoellers@xxxxxxx>> wrote:
>
> Hi,
>
> We have seen this problem: when you open a gnome-terminal, then the
> shell in that terminal will not have the same keyring (created by
> pam_keyinit.so) as the one eg in an xterm. This is due to the fact that
> the xterm ist started by the standard fork/exec mechanism which passes
> the keyring down to the children and the gnome-teminal (actually
> gnome-terminal-server) is started by sending a dbus message to some
> instance which the starts the terminal process.
>
> AAMOF the gnome-terminal does not even have a keyring, so if one asks
> for it ("keyctl show @s"), it is created on the fly. This causes the
> kernel to create a keyring as a "user session keyring" while the GNOME
> session (and thus the xterm) has a "session keyring".
>
> Has anyone seen this and/or, most important question, does anyone have
> an idea how to solve this?
>
> I know that, strictly speaking, this is not a systemd question, but
> we're trying to probe many sources to see if anyone has a solution.
>
>
> IIRC the usual advice by Lennart is to use the user-wide @u keyring
> instead of session keyrings. (Programs searching in @s should
> automatically find credentials added to @u, as pam_keyinit creates the
> link by default.)
Thanks Mantas,
It's not the fact that the user keyring is missing, which it isn't, but
it's the fact that a "user session keyring" rather than a "session
keyring" is produced:
That is not what I was talking about...
ssh:
Keyring
69871887 --alswrv 1000 100 keyring: _ses
105956722 --alswrv 1000 65534 \_ keyring: _uid.1000
-> Session Keyring (_ses) linked to User Keyring (_uid.<UID>)
gnome-terminal-server:
Keyring
219457014 --alswrv 1000 65534 keyring: _uid_ses.1000
105956722 --alswrv 1000 65534 \_ keyring: _uid.1000
-> User Session Keyring (_uid_ses.<UID>) linked to User Keyring (_uid.<UID>)
User Keyring is identical with User Keyring in ssh
xterm:
Keyring
633373159 --alswrv 1000 100 keyring: _ses
105956722 --alswrv 1000 65534 \_ keyring: _uid.1000
-> Session Keyring (_ses) linked to User Keyring (_uid.<UID>)
User Keyring is identical with User Keyring in ssh
-end of output-
I'm not THAT familiar with the keyring mechanism, especially not with
the actualy usage of them, but I don't know if one application or the
other might later choke on the top level NOT being a "session keyring"
but a "user session keyring".
Only if they do an explicit check for no good reason. AFAIK, other than the name, both kinds of keyrings otherwise behave identically from a program's perspective, and whenever the program asks for @s and there isn't one, the kernel just automatically substitutes @us.
The only real issue is that programs won't be able to find *the actual credentials* that were added to a different keyring.
> You could probably alter pam_keyinit.so to allow joining an existing
> session keyring (which is IIRC possible in the API). That way your
> graphical sessions Ipam.d/gdm) would join the same @s created by systemd
> --user instance (pam.d/systemd-user), which is the same one used by
> dbus-daemon.
The point is that in the gnome-terminal case, pam_keyinit.so is not
involved.
It is. The systemd --user instance (from which dbus-daemon and gnome-terminal-server descend) has its own PAM stack and can call pam_keyinit.so if needed.
Mantas Mikulėnas
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