cpanel-importer/scripts/extract.sh

#!/usr/bin/env bash
#
# extract.sh — symlink scan + sanitized cpmove untar.
#
# Usage:  extract.sh <tarball> <dest> <username> [<actions_out>]
#
# Calls scripts/lib/scan-symlinks.php first, then untars the cpmove with
# every DANGEROUS-classified symlink entry stripped via tar --exclude.
# The stripped-symlinks list is written as JSON to <actions_out> (default
# $DEST/.cpanel-importer-stripped-symlinks.json) so the merge step in
# entrypoint.sh can fold the stripped entries into report.json's actions[].
#
# Sandbox-mode posture: never refuse. ALFA-class root symlinks and other
# DANGEROUS entries are silently excluded from extraction; the panel sees
# them as quarantine actions on the results page instead of an import abort.

set -euo pipefail

TARBALL="${1:?usage: extract.sh <tarball> <dest> <username> [<actions_out>]}"
DEST="${2:?usage: extract.sh <tarball> <dest> <username> [<actions_out>]}"
USERNAME="${3:?usage: extract.sh <tarball> <dest> <username> [<actions_out>]}"
ACTIONS_OUT="${4:-${DEST}/.cpanel-importer-stripped-symlinks.json}"

ts()  { date -u +'%Y-%m-%dT%H:%M:%SZ'; }
log() { printf '[%s] extract: %s\n' "$(ts)" "$*"; }

[[ -f "$TARBALL" ]] || { log "tarball not found: $TARBALL"; exit 2; }
mkdir -p "$DEST"

# --- pre-extract symlink scan ---------------------------------------------

log "scanning tarball for dangerous symlinks (cpmove vector check)"
SYMLINK_REPORT=$(mktemp -p /tmp scan-symlinks.XXXXXX.json)
if ! php /scripts/lib/scan-symlinks.php \
        --tarball "$TARBALL" \
        --username "$USERNAME" \
        --report "$SYMLINK_REPORT"; then
    log "scan-symlinks.php exited with usage/IO error; aborting (this is not a sanitize-able state)"
    cat "$SYMLINK_REPORT" >&2 || true
    exit 3
fi

# --- compute exclude list from dangerous findings -------------------------

# Build a newline-delimited list of archive_path strings for tar --exclude-
# from. Also build a JSON actions[] array so entrypoint.sh's merge step can
# fold the strip-actions into report.json without re-parsing scan-symlinks.
EXCLUDES_FILE=$(mktemp -p /tmp tar-excludes.XXXXXX)
DANGEROUS_COUNT=$(python3 - "$SYMLINK_REPORT" "$EXCLUDES_FILE" "$ACTIONS_OUT" <<'PY'
import json, sys
src, excl_path, actions_path = sys.argv[1], sys.argv[2], sys.argv[3]
try:
    with open(src) as fh:
        r = json.load(fh)
except Exception as e:
    sys.stderr.write(f"failed to parse scan-symlinks report: {e}\n")
    print(0)
    sys.exit(0)

dangerous = [f for f in r.get('findings', []) if f.get('type') == 'DANGEROUS']
with open(excl_path, 'w') as eh:
    for f in dangerous:
        p = f.get('archive_path', '')
        if p:
            eh.write(p + '\n')

actions = [
    {
        'action':       'stripped_dangerous_symlink',
        'path':         f.get('archive_path', ''),
        'target':       f.get('target', ''),
        'reason':       f.get('reason', ''),
    }
    for f in dangerous
]
with open(actions_path, 'w') as ah:
    json.dump({'actions': actions, 'count': len(actions)}, ah, indent=2)
print(len(dangerous))
PY
)

if [[ "$DANGEROUS_COUNT" -gt 0 ]]; then
    log "stripping $DANGEROUS_COUNT dangerous symlink(s) via tar --exclude-from"
    while IFS= read -r path; do
        log "  STRIP: $path"
    done < "$EXCLUDES_FILE"
fi

# --- extract --------------------------------------------------------------

# Detect compression. cpmove can be .tar.gz / .tar.bz2 / .tar.
TAR_FLAGS="-xf"
case "$TARBALL" in
    *.tar.gz|*.tgz)   TAR_FLAGS="-xzf" ;;
    *.tar.bz2|*.tbz2) TAR_FLAGS="-xjf" ;;
    *.tar.xz|*.txz)   TAR_FLAGS="-xJf" ;;
    *.tar)            TAR_FLAGS="-xf"  ;;
esac

log "extracting with hardened tar flags into $DEST"
# Hardening flags (mirrored from CpanelBackupImporter::extractBackup):
#   --no-same-owner / --no-same-permissions: drop archive-recorded
#     uid/perm bits so the cpmove can't drop setuid binaries at us.
#   --no-overwrite-dir: refuse to clobber existing directory metadata,
#     closing one historical tar-symlink-escape vector.
#   --exclude-from=$EXCLUDES_FILE: strip every DANGEROUS-classified
#     symlink (target = /, /etc, /root, /boot, /proc, /sys, /dev).
#     Empty file = no-op exclude. tar's --exclude pattern matching
#     uses fnmatch but our archive_path entries don't contain glob
#     metacharacters (they came verbatim from `tar -tvf`), so the
#     match is effectively a literal-path skip.
#   --absolute-names is NOT used — leading / in a member name is stripped.
cd "$DEST"
tar --no-same-owner --no-same-permissions --no-overwrite-dir \
    --exclude-from="$EXCLUDES_FILE" \
    $TAR_FLAGS "$TARBALL"

log "extracted OK ($(find "$DEST" -type f | wc -l) files; $DANGEROUS_COUNT symlinks stripped)"
exit 0