Marc S. Weidner
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Signed-off-by: Marc S. Weidner <msw@coresecret.dev>
253 lines
10 KiB
Bash
253 lines
10 KiB
Bash
#!/bin/bash
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# SPDX-Version: 3.0
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# SPDX-CreationInfo: 2025-06-17; WEIDNER, Marc S.; <msw@coresecret.dev>
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# SPDX-ExternalRef: GIT https://git.coresecret.dev/msw/CISS.debian.installer.git
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# SPDX-FileContributor: WEIDNER, Marc S.; Centurion Intelligence Consulting Agency
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# SPDX-FileCopyrightText: 2024-2025; WEIDNER, Marc S.; <msw@coresecret.dev>
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# SPDX-FileType: SOURCE
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# SPDX-License-Identifier: EUPL-1.2 OR LicenseRef-CCLA-1.0
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# SPDX-LicenseComment: This file is part of the CISS.debian.installer.secure framework.
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# SPDX-PackageName: CISS.debian.installer
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# SPDX-Security-Contact: security@coresecret.eu
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guard_sourcing
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#######################################
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# Setup Dropbear Initramfs Environment.
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# Globals:
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# HMP_PATH_ENCLABEL
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# TARGET
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# VAR_CRYPT_ROOT
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# VAR_FINAL_FQDN
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# VAR_FINAL_IPV4
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# VAR_FINAL_IPV4_GW
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# VAR_FINAL_IPV4_SUBNET
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# VAR_FINAL_NIC
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# VAR_GRUB_CMDLINE_LINUX
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# VAR_SETUP_PATH
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# dropbear_dhcp
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# dropbear_firewall
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# dropbear_port
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# network_static_ipv4nameserver_0
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# network_static_ipv4nameserver_1
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# ssh_allow_ipv4_0
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# user_root_ssh_pubkeys_0
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# user_root_ssh_pubkeys_1
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# user_root_ssh_pubkeys_2
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# user_root_ssh_pubkeys_3
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# Arguments:
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# None
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# Returns:
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# 0: on success
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#######################################
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setup_dropbear() {
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### Prepare strong dropbear host keys
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rm -f "${TARGET}"/etc/dropbear/initramfs/dropbear*key
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do_in_target "${TARGET}" /usr/bin/dropbearkey -t rsa -s 4096 -f /etc/dropbear/initramfs/dropbear_rsa_host_key
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do_in_target "${TARGET}" /usr/bin/dropbearkey -t ed25519 -f /etc/dropbear/initramfs/dropbear_ed25519_host_key
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chmod 0600 "${TARGET}"/etc/dropbear/initramfs/dropbear*key
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chown root:root "${TARGET}"/etc/dropbear/initramfs/dropbear*key
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### Prepare dropbear authorized_keys
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touch "${TARGET}/etc/dropbear/initramfs/authorized_keys" && chmod 0600 "${TARGET}/etc/dropbear/initramfs/authorized_keys"
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printf "%s\n" "${user_root_sshpubkey}" > "${TARGET}/etc/dropbear/initramfs/authorized_keys"
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install -D -m 0755 -o root -g root "${VAR_SETUP_PATH}/includes/etc/banner" "${TARGET}/etc/dropbear/initramfs/"
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### Check for initramfs "IP"-variable: static or dynamic configuration vai dhcp.
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if [[ "${dropbear_dhcp,,}" != "true" ]]; then
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declare network_static_ipv4ntpserver_0="192.53.103.108"
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### "IP=<HOST IP>::<GATEWAY IP>:<SUBNET MASK>:<FQDN>:<NIC>:none:<DNS 0 IP>:<DNS 1 IP>:<NTP IP>"
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printf "IP=%s::%s:%s:%s:%s:none:%s:%s:%s\n" \
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"${VAR_FINAL_IPV4}" \
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"${VAR_FINAL_IPV4_GW}" \
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"${VAR_FINAL_IPV4_SUBNET}" \
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"${VAR_FINAL_FQDN}" \
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"${VAR_FINAL_NIC}" \
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"${network_static_ipv4nameserver_0:-135.181.207.105}" \
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"${network_static_ipv4nameserver_1:-89.58.62.53}" \
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"${network_static_ipv4ntpserver_0:-192.53.103.104}" \
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>| "${TARGET}/etc/initramfs-tools/conf.d/ip"
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else
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### "IP=:::::<NIC>:dhcp"
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printf "IP=:::::%s:dhcp\n" "${VAR_FINAL_NIC}" >| "${TARGET}/etc/initramfs-tools/conf.d/ip"
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fi
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### Generate dropbear configuration file
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write_dropbear_conf
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### Prepare Grub Bootparameter for LUKS decryption of '/root' and '/recovery'.
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# Options in "GRUB_CMDLINE_LINUX" are always effective.
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# Options in "GRUB_CMDLINE_LINUX_DEFAULT" are effective ONLY during normal boot (NOT during recovery mode).
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grub_extract_current_string
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declare var_label="${HMP_PATH_ENCLABEL["LABEL_/"]}"
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VAR_GRUB_CMDLINE_LINUX="${VAR_GRUB_CMDLINE_LINUX} cryptdevice=${VAR_CRYPT_ROOT}:cryptroot root=/dev/mapper/${var_label}"
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grub_finalize_string
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### Install the script to be called by 'update-initramfs' for updating 'PATH'-variable inside initramfs.
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install -D -m 0755 -o root -g root "${VAR_SETUP_PATH}/includes/initramfs-tools/scripts/init-top/fixpath.sh" \
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"${TARGET}/includes/initramfs-tools/scripts/init-top/"
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### Install the script to be called by 'update-initramfs' for customizing dropbear inside initramfs.
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install -D -m 0755 -o root -g root "${VAR_SETUP_PATH}/includes/initramfs-tools/hooks/custom-initramfs.sh" \
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"${TARGET}/includes/initramfs-tools/hooks/"
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### Install the script to be called by 'update-initramfs' for customizing prompt inside initramfs environment.
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install -D -m 0755 -o root -g root "${VAR_SETUP_PATH}/includes/initramfs-tools/hooks/custom-prompt.sh" \
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"${TARGET}/includes/initramfs-tools/hooks/"
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### Install the script to be called inside initramfs environment for unlocking LUKS and NUKE Devices.
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install -D -m 0755 -o root -g root "${VAR_SETUP_PATH}/includes/initramfs-tools/files/unlock_wrapper.sh" \
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"${TARGET}/includes/initramfs-tools/files/"
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install -D -m 0755 -o root -g root "${VAR_SETUP_PATH}/includes/initramfs-tools/files/unlock_wrapper.sh" \
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"${TARGET}/usr/lib/cryptsetup/scripts/"
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# TODO: Update preseed.yaml for pgp signing key AND / OR implementation of presigned unlock-wrapper.sh
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### Install the script to be called inside Host environment for signing 'unlock_wrapper.sh'-script.
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install -D -m 0700 -o root -g root "${VAR_SETUP_PATH}/includes/initramfs-tools/files/unlock_wrapper_signer.sh" \
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"${TARGET}/includes/initramfs-tools/files/"
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### Install the script to be called by 'update-initramfs' for installing the necessary modules to load into initramfs environment.
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install -D -m 0644 -o root -g root "${VAR_SETUP_PATH}/includes/initramfs-tools/modules" \
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"${TARGET}/includes/initramfs-tools/"
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declare var_modules; var_modules=$(grep_nic_driver_modules)
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cat << EOF >> "${TARGET}/includes/initramfs-tools/modules"
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### Custom NIC driver
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${var_modules}
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# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh
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EOF
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### Install the script to be called inside initramfs environment for preparing dropbear execution.
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do_in_target "${TARGET}" mv /usr/share/initramfs-tools/scripts/init-premount/dropbear /usr/share/initramfs-tools/scripts/init-premount/dropbear.2022.83
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install -D -m 0755 -o root -g root "${VAR_SETUP_PATH}/includes/usr/share/initramfs-tools/scripts/init-premount/dropbear" \
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"${TARGET}/includes/usr/share/initramfs-tools/scripts/init-premount/"
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### Install the variable file to be called inside initramfs environment for setting up dropbear firewall.
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install -D -m 0600 -o root -g root "${VAR_SETUP_PATH}/includes/initramfs-tools/files/dropbear_fw.cnf" \
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"${TARGET}/includes/initramfs-tools/files/dropbear_fw.conf"
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### Install the firewall script to be called inside initramfs environment for setting up dropbear firewall.
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install -D -m 0755 -o root -g root "${VAR_SETUP_PATH}/includes/initramfs-tools/files/dropbear_fw.sh" \
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"${TARGET}/includes/initramfs-tools/files/"
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if [[ "${dropbear_firewall,,}" == "true" && -n "${ssh_allow_ipv4_0}" ]]; then
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sed -i 's/^DROPBEAR_FIREWALL_ENABLED=0$/DROPBEAR_FIREWALL_ENABLED=1/' "${TARGET}/includes/initramfs-tools/files/dropbear_fw.cnf"
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sed -i '/^# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh$/d' "${TARGET}/includes/initramfs-tools/files/dropbear_fw.cnf"
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cat << EOF >> "${TARGET}/includes/initramfs-tools/files/dropbear_fw.cnf"
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DROPBEAR_PORT=${dropbear_port}
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DROPBEAR_JUMP_SERVER_IP=${ssh_allow_ipv4_0}
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# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh
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EOF
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fi
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### Finally, deploy all changes done via 'update-grub' and 'update-initramfs'.
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do_in_target "${TARGET}" update-grub
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do_in_target "${TARGET}" update-initramfs -u -v -k all
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return 0
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}
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#######################################
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# Write '/etc/dropbear/initramfs/dropbear.conf'.
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# Globals:
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# TARGET
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# ssh_port
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# Arguments:
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# None
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# Returns:
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# 0: on success
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#######################################
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write_dropbear_conf() {
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[[ -z "${dropbear_port:-}" ]] && dropbear_port="2222"
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cat << EOF >| "${TARGET}/etc/dropbear/initramfs/dropbear.conf"
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#
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# Configuration options for the dropbear-initramfs boot scripts.
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# Variable assignment follow shell semantics and escaping/quoting rules.
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# You must run update-initramfs(8) to effect changes to this file (like
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# for other files in the '/etc/dropbear/initramfs' directory).
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#
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# Command line options to pass to dropbear(8)
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# Dropbear options for 2025+:
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# -b: Display the contents of bannerfile before user login
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# -E: Log to stderr
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# -I: Idle timeout in seconds
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# -K: Keepalive interval in seconds
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# -p: Specify port (and optionally address)
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# -w: Disable root login (SHOULD NOT be implemented for initramfs)
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DROPBEAR_OPTIONS="-b /etc/dropbear/banner -c /usr/local/bin/unlock_wrapper.sh -E -I 300 -K 60 -p ${dropbear_port}"
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#
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# On local (non-NFS) mounts, interfaces matching this pattern are
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# brought down before exiting the ramdisk to avoid dirty network
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# configuration in the normal kernel.
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# The special value 'none' keeps all interfaces up and preserves routing
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# tables and addresses.
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#
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#IFDOWN="*"
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#
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# On local (non-NFS) mounts, the network stack and dropbear are started
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# asynchronously at init-premount stage. This value specifies the
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# maximum number of seconds to wait (while the network/dropbear are
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# being configured) at init-bottom stage before terminating dropbear and
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# bringing the network down.
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# If the timeout is too short, and if the boot process is not blocking
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# on user input supplied via SSHd (ie no remote unlocking), then the
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# initrd might pivot to init(1) too early, thereby causing a race
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# condition between network configuration from initramfs vs from the
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# normal system.
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#
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#DROPBEAR_SHUTDOWN_TIMEOUT=60
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EOF
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do_log "info" "file_only" "Written: '${TARGET}/etc/dropbear/initramfs/dropbear.conf'."
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return 0
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}
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#######################################
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# Collect NIC driver modules for initramfs installation.
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# Arguments:
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# None
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# Returns:
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# 0: on success
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#######################################
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grep_nic_driver_modules() {
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### Collect all ethernet driver names and sort them uniquely.
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declare -a _mods
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declare var_nic_module var_nic_modules
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# shellcheck disable=SC2312
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readarray -t _mods < <(
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lspci -k \
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| grep -A2 -i ethernet \
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| grep 'Kernel driver in use' \
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| awk '{print $5}' \
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| sort -u
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)
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### If only one entry remains, save it in 'var_nic_module', otherwise save all modules in 'var_nic_modules'.
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if [[ "${#_mods[@]}" -eq 1 ]]; then
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var_nic_module="${_mods[0]}"
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else
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var_nic_modules="${_mods[*]}"
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fi
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if [[ -n "${var_nic_module}" ]]; then
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echo "${var_nic_module}"
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else
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echo "${var_nic_modules}"
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fi
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return 0
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}
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# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh
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