grub2-signing-extension/README.md

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# grub2-signing-extension for GRUB2
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GRUB2 has got a function which automatically checks if your GRUB2 files are signed and have a good signature. If the files aren't signed or have a bad signature GRUB2 won't run them to prevent running malicious software.
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The GRUB2 signing extension are some scripts which helps you to verify, sign and unsign your GRUB2 bootloader files using gpg.
## Requirements
You need
* GRUB2 ( sys-boot/grub:2 )
* GNUpg ( app-crypt/gnupg )
## Preparation
Before you can use the signing and verification feature you need to generate a keypair as root. Please use a secure passphrase.
`# gpg --gen-key`
To make gpg able to sign and verify files in a `su` environment we need to activate the gpg-agent for root.
Edit the file _/root/.gnupg/gpg.conf_ and add the line `use-agent`.
Save the file and create _/root/.gnupg/gpg-agent.conf_ with the following content
pinentry-program /usr/bin/pinentry-curses
no-grab
default-cache-ttl 1800
## How to install the GRUB2 check\_signatures feature and using the grub2-signing-extension
First, export your public key.
`# gpg --export -o ~/pubkey`
Next step, mount /boot and (re)install GRUB2 with the following arguments:
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`grub2-install /dev/sda -k /root/pubkey --modules="gcry_sha256 gcry_dsa gcry_rsa"`
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Now download the grub2-signing-extension and run `make install` as root. You will now have `grub2-sign`, `grub2-unsign` and `grub2-verify` as runable scripts.
To _enable_ GRUB2's check\_signatures feature insert the following content at the end of the file of */etc/grub.d/00_header*
cat << EOF
set check_signatures=enforce
EOF
Run `grub2-mkconfig -o /boot/grub/grub.cfg` to make the new configuration valid.
Now the time is come to sign your GRUB2 bootloader. Just run `grub2-sign`, enter your passphrase and that's it.
**ATTENTION:** On every change you need to run `grub2-unsign` first before you make your changes. It's also recommended to install a password in GRUB2!
## How to install a GRUB2 password
Run `grub2-mkpasswd-pbkdf2` and type a password. Please take care because in the GRUB2 standard installation the keyboard layout is set to en\_US.
Copy the content of *grub.pbkdf2.[...]* to your clipboard. Open the file */etc/grub.d/00_header* and insert this at the end of the file
cat << EOF
set superusers="yourUsername"
export superusers
password_pbkdf2 yourUsername grub.pbkdf2.[...this string from the clipboard...]
EOF
To boot GNU/Linux without automatically and without authentication open */etc/grub.d/10_linux* and change the following lines like this
echo "menuentry '$(echo "$title" | grub_quote)' ${CLASS} \$menuentry_id_option 'gnulinux-$version-$type-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
else
echo "menuentry '$(echo "$os" | grub_quote)' ${CLASS} \$menuentry_id_option 'gnulinux-simple-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
fi
to
echo "menuentry '$(echo "$title" | grub_quote)' --unrestricted ${CLASS} \$menuentry_id_option 'gnulinux-$version-$type-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
else
echo "menuentry '$(echo "$os" | grub_quote)' --unrestricted ${CLASS} \$menuentry_id_option 'gnulinux-simple-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
fi
The important changing is the flag *--unrestricted*.
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Run `grub2-unsign` to unsign the bootloader.
Then run `grub2-mkconfig -o /boot/grub/grub.cfg` to write the new config.
After this run `grub2-sign` again to sign the new changings.