grub: T6453: Fixed GRUB variables parsing

[zdc]

Change Summary

Fixed GRUB variables parsing

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://vyos.dev/T6453

Related PR(s)

Component(s) name

GRUB

Proposed changes

To parse variables with = a variable name should be limited by alphanumerical characters only.

How to test

from vyos.system import grub
grub_vars = {
    'variable_name': 'variable=value',
}
grub.vars_write('/tmp/vars.test', grub_vars)
grub.vars_read('/tmp/vars.test')

Smoketest result

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

[c-po]

@Mergifyio backport sagitta

[mergify]

backport sagitta

✅ Backports have been created

• #3604 grub: T6453: Fixed GRUB variables parsing (backport #3592) has been created for branch sagitta