Red Hat Bugzilla – Bug 805342
F16-xfce4 pinentry-gtk-2 consumes CPU, does not fall back to pinentry-curses.
Last modified: 2014-09-28 20:21:47 EDT
Description of problem:
pinentry-gtk-2 fails to drop down to pinentry-curses if no X display is available. Instead, it consumes all available CPU and must be -KILLed.
If an X display is available via ssh port forwarding, pinentry-gtk-2 fails to use the forwarded display.
The combination of factors means that it is impossible to use gpg2 over a remote connection (e.g., via ssh).
Version-Release number of selected component (if applicable):
* Fedora 16 XFCE spin
* gpg2 (GnuPG) 2.0.18
* gpg-agent (GnuPG) 2.0.18
* pinentry-gtk2 0.8.1
* pinentry-curses (pinentry) 0.8.1
* All updates applied as of 20-Mar-2012
Attempt to decrypt a PGP encrypted file from a non-X terminal session, e.g., a console login or ssh session with X11 forwarding disabled.
Steps to Reproduce:
1. Create or obtain a PGP-encrypted file, encrypted with a public key for
which you have the private key (on your GPG secret keyring).
$ ls -l | gpg2 --encrypt -a >pinentry.test.asc
(Select an appropriate public key when prompted.)
2. From an Xterminal shell, decrypt the file:
$ echo $DISPLAY
$ gpg2 --decrypt <pinentry.test.asc
3. Either wait until the cache has timed out (default 10 minutes) or kill
4. From a console terminal (e.g., press Ctrl+Alt+F3, or so), decrypt the file:
$ echo $DISPLAY
$ gpg2 --decrypt <pinentry.test.asc
Anything you type at this point will appear on the screen, but it is not
taken as input by the pinentry program.
5. Run 'top -i'
top - 17:48:31 up 1:44, 4 users, load average: 0.90, 0.33, 0.16
Tasks: 178 total, 2 running, 176 sleeping, 0 stopped, 0 zombie
Cpu(s): 19.2%us, 5.9%sy, 0.0%ni, 74.8%id, 0.0%wa, 0.2%hi, 0.0%si, 0.0%st
Mem: 4015444k total, 1553796k used, 2461648k free, 58964k buffers
Swap: 4194300k total, 0k used, 4194300k free, 707244k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2763 crh 20 0 100m 2724 2208 R 99.4 0.1 1:47.22 pinentry-gtk-2
2765 crh 20 0 15260 1268 908 R 0.0 0.0 0:00.03 top
When run from a console terminal (with no cached passphrase), the pinentry-gtk-2 program does not fall back to pinentry-curses as it should.
It consumes CPU resources until killed with -KILL.
1) The pinentry-gtk-2 module should fall back to pinentry-curses if there is
no $DISPLAY value.
2) If gpg2 is run from a terminal window (Xterminal, ssh, or otherwise), the
pinentry-curses module should be used to accept input whether $DISPLAY is
defined or not. All other input to the program is via the text terminal.
The passphrase input should not be an exception.
3) The gpg2 and gpg-agent documentation included with the XFCE Spin
installation provides a great deal of information about default
configuration file names and locations, as well as script file
pathnames, and such-like. XFCE does things differently, and finding
the information is difficult making debugging harder and all attempts
to fix the problem by hand more difficult.
gpg-agent is started by /etc/xdg/xfce4/xinitrc at X login or, if the user logs in at a console (e.g. tty3) and no gpg-agent is running, gpg-agent will be started by gpg2. The only difference between the two is the location of the listening socket and whether or not a gpg-agent-info file is written in $HOME/.cache/. Testing shows no behavioural difference.
Removal of the package pinentry-gtk-0.8.1-4.fc16 results in the following error messages from gpg2:
gpg: problem with the agent: No pinentry
gpg: public key decryption failed: Operation cancelled
gpg: decryption failed: No secret key
...indicating that gpg-agent (or possibly the /usr/bin/pinentry script) truly has no clue how to fall back to pinentry-ncurses.
I wrote above:
"If an X display is available via ssh port forwarding, pinentry-gtk-2 fails to
use the forwarded display."
This is true, but it's a tangential problem that only occurs if ssh is tunnelled over a vpn connection. I have yet reliably reproduce it. (It's some sort of X security problem.)
This problem would be bypassed if gpg2 run from a terminal used pinentry-curses by default (whether $DISPLAY was defined or not).
There are at least 2 bugs here.
First problem is more or less that when you run pinentry within gnupg context, it has no way to know if it's running on terminal or not. That is because gnupg is running pinentry in a pipe and then forwarding output onto terminal (if it has one). So the test we added for pinentry running on terminal to fallback to curses is not evaluated as true. We can do a hard fallback to pinentry-curses for cases where all else fails I guess.
I was also able to reproduce second issue of pinentry getting stuck in a loop inside xfce environment. Here I have no idea yet why that happens. It happens for pinentry-curses under some conditions as well.
Regarding the first of the isolated issues:
The problem is with gnupg2, not with gnupg. I removed gpg2 from my system and installed gpg instead, and have had no further problems.
I would suggest that this is a design flaw. It seems wrong to me that a terminal application would call an external utility to open a gui window just to retrieve one piece of input, particularly when the external utility may or may not have an environment in which to operate. If I am working in a terminal window--even if I do have an X environment running--I don't want a new window to pop up. It's disruptive.
Thanks for picking these up.
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