initramfs: Fix cryptdevice identification

[cbiedl]

Hi there,
when packaging clevis 12 for Debian, I had to change scripts/local-top/clevis line 109:

-        local "$(grep '^CRYPTTAB_SOURCE=' /proc/"$pid"/environ)"
+        local "$(grep -z '^CRYPTTAB_SOURCE=' /proc/"$pid"/environ)"

The environment is zero-terminated, therefore the text-based grep will not find anything, therefore create an emtpy statement which causes script abort.
The strange part is why appearently nobody else encountered that problem.

[jmarcelletti]

I tested this on Ubuntu 18.04 and it didn't work (broke things). To be clear this is just a clean into of 18.04.4 with nothing but default install with encrypted lvm. Here's what I see:

[cbiedl]

Hmmm, interesting. Ubuntu uses a different busybox flavour for the initrd - something I wanted to adopt for Debian as well but never got a round tuit. And that grep has a different behaviour in that regard:
busybox-static:

 # /usr/bin/busybox grep ^BOOT /proc/1/environ
 #

busybox-initramfs:

# /usr/lib/initramfs-tools/bin/busybox grep ^BOOT /proc/1/environ
BOOT_IMAGE=/vmlinuz-5.4.0-14-generic
#

This explains why we two see a different behaviour, and possibly more people will stumble upon this.
They are many differences in the configurations of these flavours, I'll check in detail on another day.