Fix UTF-16 result handling for efibootmgrstable/zed

The tl;dr is that UEFI NVRAM is in encoded
in UTF-16, and when we run the efibootmgr command,
we can get unicode characters back.

Except we previously were forcing everything to be
treated as UTF-8 due to the way oslo.concurrency's
processutils module works.

This could be observed with UTF character 0x00FF
which raises up a nice exception when we try to
decode it.

Anyhow! while fixing handling of this, we discovered
we could get basically the cruft out of the NVRAM,
by getting what was most likey a truncated string
out of our own test VMs. As such, we need to also
permit decoding to be tollerant of failures.
This could be binary data or as simple as flipped
bits which get interpretted invalid characters.
As such, we have introduced such data into one of our
tests involving UEFI record de-duplication.

Closes-Bug: 2015602
Change-Id: I006535bf124379ed65443c7b283bc99ecc95568b
(cherry picked from commit 76accfb880474445a5dcb07825889123b3dd0237)

1 files changed, 11 insertions, 4 deletions

diff --git a/ironic_python_agent/efi_utils.py b/ironic_python_agent/efi_utils.py
index 48e643d3..6fc8dff1 100644
--- a/ironic_python_agent/efi_utils.py
+++ b/ironic_python_agent/efi_utils.py
@@ -275,8 +275,15 @@ def get_boot_records():
 
     :return: an iterator yielding pairs (boot number, boot record).
     """
-    efi_output = utils.execute('efibootmgr', '-v')
-    for line in efi_output[0].split('\n'):
+    # Invokes binary=True so we get a bytestream back.
+    efi_output = utils.execute('efibootmgr', '-v', binary=True)
+    # Bytes must be decoded before regex can be run and
+    # matching to work as intended.
+    # Also ignore errors on decoding, as we can basically get
+    # garbage out of the nvram record, this way we don't fail
+    # hard on unrelated records.
+    cmd_output = efi_output[0].decode('utf-16', errors='ignore')
+    for line in cmd_output.split('\n'):
         match = _ENTRY_LABEL.match(line)
         if match is not None:
             yield (match[1], match[2])
@@ -293,7 +300,7 @@ def add_boot_record(device, efi_partition, loader, label):
     # https://linux.die.net/man/8/efibootmgr
     utils.execute('efibootmgr', '-v', '-c', '-d', device,
                   '-p', str(efi_partition), '-w', '-L', label,
-                  '-l', loader)
+                  '-l', loader, binary=True)
 
 
 def remove_boot_record(boot_num):
@@ -301,7 +308,7 @@ def remove_boot_record(boot_num):
 
     :param boot_num: the number of the boot record
     """
-    utils.execute('efibootmgr', '-b', boot_num, '-B')
+    utils.execute('efibootmgr', '-b', boot_num, '-B', binary=True)
 
 
 def _run_efibootmgr(valid_efi_bootloaders, device, efi_partition,