Marc S. Weidner
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Signed-off-by: Marc S. Weidner <msw@coresecret.dev>
230 lines
7.4 KiB
Bash
230 lines
7.4 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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# Configure the target system for chroot.
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# Globals:
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# TARGET
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# VAR_CHROOT_ACTIVATED
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# VAR_CHROOT_SYS_MASK_HELPER
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# VAR_NEED_RUN_IN_TARGET
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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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# ERR_CHRT_MOUNTS: on failure
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#######################################
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prepare_mounts() {
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### Notes
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# This function mounts all necessary pseudo filesystems into the target root environment to enable chroot operations.
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# --rbind: recursive binding.
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# --make-rslave: In this case, the mount point is marked as 'slave'.
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# This means changes to the source mount (e.g., /proc) are propagated to the target mount (e.g., "${TARGET}/proc").
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# Conversely, changes to the target mount are not propagated back to the source mount.
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# This mode is necessary to avoid problems with double or erroneous propagation effects in chroot or container environments.
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#
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# Some subdirectories (such as /dev/pts, /dev/shm, /sys/fs/cgroup) are remounted with more restrictive options
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# like 'noexec', 'nosuid', and 'nodev' to enhance security. This ensures they override the inherited bind-mounts and
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# enforce proper runtime behavior in the chroot.
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### Declare Arrays, HashMaps, and Variables.
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declare -A HMP_SPECIAL_MOUNTS=(
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["/dev"]="devtmpfs devtmpfs mode=0755,nosuid" # Base device node FS
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["/dev/pts"]="devpts devpts noexec,nosuid" # Pseudoterminals
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["/dev/shm"]="tmpfs tmpfs rw,nosuid,nodev" # Shared memory
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["/dev/mqueue"]="mqueue mqueue rw,nosuid,nodev,noexec" # POSIX message queues
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["/dev/hugepages"]="hugetlbfs hugetlbfs rw,nosuid,nodev" # Huge pages
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["/proc"]="proc proc nosuid,noexec,nodev" # procfs
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["/sys"]="sysfs sysfs nosuid,noexec,nodev" # sysfs
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["/sys/fs/cgroup"]="cgroup2 cgroup2 rw,nosuid,nodev,noexec,relatime" # Unified cgroup2
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)
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declare var_path="" var_fs="" var_src="" var_opts=""
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# shellcheck disable=SC2034
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declare -g VAR_CHROOT_SYS_MASK_HELPER=""
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# shellcheck disable=SC2034
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VAR_CHROOT_SYS_MASK_HELPER=$(cat <<'EOF'
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#-------------------------------------------------------------------------------
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# Helpers: mount detection and conditional umount (idempotent).
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# Detect if PATH is an exact mountpoint (not just covered by a parent mount).
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cdi_is_mountpoint() {
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declare path="${1:?target path required}"
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if command -v mountpoint >/dev/null 2>&1; then
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mountpoint -q -- "${path}"
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return $?
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fi
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if command -v findmnt >/dev/null 2>&1; then
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# Exact mountpoint check (not -T which matches enclosing mounts).
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findmnt -rn --mountpoint "${path}" >/dev/null 2>&1 && return 0 || return 1
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fi
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# Fallback: parse /proc/self/mountinfo (field 5 = mountpoint, no spaces here).
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awk -v p="${path}" '$5==p {found=1; exit} END{exit (found?0:1)}' /proc/self/mountinfo 2>/dev/null
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}
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cdi_umount_if_mountpoint() {
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declare path="${1:?target path required}"
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if cdi_is_mountpoint "${path}"; then
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umount -l -- "${path}" || { printf 'ERROR: cannot umount %s\n' "${path}" >&2; return 128; }
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fi
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return 0
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}
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cdi_sys_mask_enter() {
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declare state="/run/.ciss_sysmask"
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mkdir -p /run
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# Record only true mountpoints.
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declare had_sys="0"
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declare had_cg="0"
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cdi_is_mountpoint /sys && had_sys="1"
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cdi_is_mountpoint /sys/fs/cgroup && had_cg="1"
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printf 'HAD_SYS=%s\nHAD_CG=%s\n' "${had_sys}" "${had_cg}" >| "${state}"
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# Unmount only if exact mountpoints exist.
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cdi_umount_if_mountpoint /sys/fs/cgroup || return 129
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cdi_umount_if_mountpoint /sys || return 130
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mkdir -p /sys
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mount -t tmpfs -o ro,nosuid,nodev,noexec,mode=0555,size=1M tmpfs /sys \
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|| { printf 'ERROR: cannot mount tmpfs on /sys\n' >&2; return 131; }
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return 0
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}
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cdi_sys_mask_leave() {
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declare state="/run/.ciss_sysmask"
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declare had_sys="0"
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declare had_cg="0"
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if [[ -f "${state}" ]]; then
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# shellcheck disable=SC2155
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declare had_sys="$(grep -Eo '^HAD_SYS=[01]' "${state}" 2>/dev/null | cut -d= -f2 || printf '0')"
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# shellcheck disable=SC2155
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declare had_cg="$(grep -Eo '^HAD_CG=[01]' "${state}" 2>/dev/null | cut -d= -f2 || printf '0')"
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fi
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# Drop the mask if present (it is an exact mountpoint).
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cdi_umount_if_mountpoint /sys || return 132
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if [[ "${had_sys}" == "1" ]]; then
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mount -t sysfs -o nosuid,nodev,noexec sysfs /sys \
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|| { printf 'ERROR: cannot mount sysfs on /sys\n' >&2; return 133; }
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fi
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if [[ "${had_cg}" == "1" ]]; then
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mkdir -p /sys/fs/cgroup
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mount -t cgroup2 -o rw,nosuid,nodev,noexec,relatime cgroup2 /sys/fs/cgroup \
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|| { printf 'ERROR: cannot mount cgroup2 on /sys/fs/cgroup\n' >&2; return 134; }
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fi
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rm -f -- "${state}"
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return 0
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}
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#-------------------------------------------------------------------------------
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EOF
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)
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for var_path in "${!HMP_SPECIAL_MOUNTS[@]}"; do
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mkdir -p "${TARGET}${var_path}"
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done
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for var_path in "${!HMP_SPECIAL_MOUNTS[@]}"; do
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IFS=" " read -r var_fs var_src var_opts <<< "${HMP_SPECIAL_MOUNTS[${var_path}]}"
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if mountpoint -q "${TARGET}${var_path}"; then
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do_log "info" "file_only" "4010() Skipped: '${TARGET}${var_path}' is already a mountpoint."
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continue
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fi
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if ! mount -t "${var_fs}" "${var_src}" "${TARGET}${var_path}" -o "${var_opts}"; then
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do_log "emergency" "file_only" "4010() Command: [mount -t ${var_fs} ${var_src} ${TARGET}${var_path} -o ${var_opts}] failed."
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return "${ERR_CHRT_MOUNTS}"
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fi
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do_log "info" "file_only" "4010() Command: [mount -t ${var_fs} ${var_src} ${TARGET}${var_path} -o ${var_opts}] successful."
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done
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if [[ "${VAR_NEED_RUN_IN_TARGET:-false}" == "true" ]]; then
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mkdir -p "${TARGET}/run"
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if ! mount --make-rslave --rbind /run "${TARGET}/run"; then
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do_log "emergency" "file_only" "4010() Command: [mount --make-rslave --rbind /run ${TARGET}/run] failed."
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return "${ERR_CHRT_MOUNTS}"
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fi
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do_log "info" "file_only" "4010() Command: [mount --make-rslave --rbind /run ${TARGET}/run] successful."
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fi
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if ! chroot_exec "${TARGET}" mkdir -p /etc/systemd/system/multi-user.target.wants; then
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do_log "emergency" "file_only" "4010() Command: [chroot_exec ${TARGET} mkdir -p /etc/systemd/system/multi-user.target.wants] failed."
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return "${ERR_CHRT_MOUNTS}"
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fi
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do_log "info" "file_only" "4010() Command: [chroot_exec ${TARGET} mkdir -p /etc/systemd/system/multi-user.target.wants] successful."
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mkdir -p "${TARGET}/media/cdrom0"
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# shellcheck disable=SC2034
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declare -gx VAR_CHROOT_ACTIVATED="system"
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do_log "info" "file_only" "4010() Command: [declare -gx VAR_CHROOT_ACTIVATED=system]"
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guard_dir && return 0
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}
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### Prevents accidental 'unset -f'.
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# shellcheck disable=SC2034
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readonly -f prepare_mounts
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# vim: number et ts=2 sw=2 sts=2 ai tw=128 ft=sh
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