51 lines
1.7 KiB
Bash
51 lines
1.7 KiB
Bash
#!/usr/bin/env bash
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set -uo pipefail
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# CASAN Plan-16 SEC-28 (X-04) — path-traversal / symlink guard.
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#
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# A tool that takes a file path as input/output can be pointed at an arbitrary
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# location via `..` or a symlink (e.g. a symlink named "input.txt" -> /etc/passwd),
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# reading or writing outside the workspace. This resolves the REAL path (following
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# every symlink) and refuses anything that escapes the allowed root.
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#
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# Usage: path-guard.sh <path> [allowed-root] (default root: repo workspace)
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# Exit: 0 inside the root, 1 outside / unresolvable.
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SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
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source "$SCRIPT_DIR/casan-paths.sh"
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PROJECT_ROOT="$CASAN_APP_ROOT"
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PYTHON_BIN="${CASAN_PYTHON_BIN:-}"
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if [[ -z "$PYTHON_BIN" ]]; then
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for candidate in /usr/bin/python3 python3 python; do
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if command -v "$candidate" >/dev/null 2>&1 && "$candidate" --version >/dev/null 2>&1; then
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PYTHON_BIN="$candidate"
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break
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fi
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done
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fi
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[[ -n "$PYTHON_BIN" ]] || { echo "PATH_GUARD_RUNTIME_UNAVAILABLE" >&2; exit 69; }
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TARGET="${1:-}"
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ROOT="${2:-$PROJECT_ROOT}"
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if [[ -z "$TARGET" ]]; then
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echo "Usage: path-guard.sh <path> [allowed-root]" >&2
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exit 64
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fi
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"$PYTHON_BIN" - "$TARGET" "$ROOT" <<'PY'
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import os
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import sys
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target, root = sys.argv[1], sys.argv[2]
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# realpath resolves symlinks in every existing path component and normalizes "..";
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# for a not-yet-created leaf it resolves the existing parent chain.
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real_target = os.path.realpath(target)
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real_root = os.path.realpath(root)
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if real_target == real_root or real_target.startswith(real_root + os.sep):
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print(f"PATH_OK {real_target}")
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sys.exit(0)
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sys.stderr.write(f"PATH_ESCAPES_ROOT target={target} real={real_target} root={real_root}\n")
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sys.exit(1)
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PY
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