Re: [Libguestfs] [PATCH nbdkit 9/9] eval, sh: Define $nbdkit_safe_stdio = 0|1 in scripts.

On 4/15/20 11:16 AM, Richard W.M. Jones wrote: In the subject, you describe $nbdkit_safe_stdio, but in the patch body... >--- > plugins/eval/nbdkit-eval-plugin.pod | 11 +++-------- > plugins/sh/nbdkit-sh-plugin.pod | 18 +++++++++++++++++- > plugins/sh/call.c | 8 ++++++-- > tests/test-single-sh.sh | 4 ++++ > 4 files changed, 30 insertions(+), 11 deletions(-) > The patch does not work as intended as currently written: when we invoke /path/to/script config $key $value, we have already set up stdin/stdout to our own pipes [1].

For .config and .config_complete, reading will always see EOF (no other callback needs to interact with the original stdin, and callbacks like .pwrite actually use the pipe for data). If we want to allow a script to read a password from stdin, we need to preserve the original fd to .config and .config_complete rather than passing in an empty pipe (but those are the only two callbacks where it makes sense, and even then, only when we did not use script=- or when -s is in effect). [1] ./nbdkit eval config='ls -l /proc/$$/fd >/dev/tty' a=b total 0 lr-x------. 1 eblake eblake 64 Apr 15 13:03 0 -> 'pipe:[1669308]' l-wx------. 1 eblake eblake 64 Apr 15 13:03 1 -> 'pipe:[1669309]' l-wx------. 1 eblake eblake 64 Apr 15 13:03 2 -> 'pipe:[1669310]' lr-x------. 1 eblake eblake 64 Apr 15 13:03 255 -> /tmp/nbdkitevalVUNZ1F/config

Side thought: Both the eval and sh plugins already pass on all unrecognized key=value pairs through to the .config callback, and error out if the config callback returns missing. But right now, if a script wants to set up an environment variable that will still be present to affect later calls, it has to track things itself (perhaps by having the .config callback append to $tmpdir/vars, then all other callbacks start by 'source $tmpdir/vars'). Would it make sense to reserve a special exit value from the .config callback for the case where the script wants the current key=value passed to config to be preserved to all future callbacks? Or even state that the config callback exiting with status 2 (for missing) is NOT an error, but does the key=value preservation automatically?