mirror of
https://github.com/leonvanzyl/autocoder.git
synced 2026-02-05 16:33:08 +00:00
fix: harden dev server RCE mitigations from PR #153
Address security gaps and improve validation in the dev server command execution path introduced by PR #153: Security fixes (critical): - Add missing shell metacharacters to dangerous_ops blocklist: single & (Windows cmd.exe command separator), >, <, ^, %, \n, \r - The single & gap was a confirmed RCE bypass on Windows where .cmd files are always executed via cmd.exe even with shell=False (CPython limitation documented in issue #77696) - Apply validate_custom_command_strict at /start endpoint for defense-in-depth against config file tampering Validation improvements: - Fix uvicorn --flag=value syntax (split on = before comparing) - Expand Python support: Django (manage.py), Flask, custom .py scripts - Add runners: flask, poetry, cargo, go, npx - Expand npm script allowlist: serve, develop, server, preview - Reorder PATCH /config validation to run strict check first (fail fast) - Extract constants: ALLOWED_NPM_SCRIPTS, ALLOWED_PYTHON_MODULES, BLOCKED_SHELLS for reuse and testability Cleanup: - Remove unused security.py imports from dev_server_manager.py - Fix deprecated datetime.utcnow() -> datetime.now(timezone.utc) - Remove unnecessary _remove_lock() in exception handlers where lock was never created (Popen failure path) Tests: - Add test_devserver_security.py with 78 tests covering valid commands, blocked shells, blocked commands, injection attempts, dangerous_ops blocking, and constant verification Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Auto
@@ -7,8 +7,8 @@ Uses project registry for path lookups and project_config for command detection.
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"""
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import logging
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import sys
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import shlex
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import sys
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from pathlib import Path
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from fastapi import APIRouter, HTTPException
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@@ -73,7 +73,20 @@ def get_project_dir(project_name: str) -> Path:
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return project_dir
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ALLOWED_RUNNERS = {"npm", "pnpm", "yarn", "uvicorn", "python", "python3"}
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ALLOWED_RUNNERS = {
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"npm", "pnpm", "yarn", "npx",
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"uvicorn", "python", "python3",
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"flask", "poetry",
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"cargo", "go",
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}
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ALLOWED_NPM_SCRIPTS = {"dev", "start", "serve", "develop", "server", "preview"}
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# Allowed Python -m modules for dev servers
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ALLOWED_PYTHON_MODULES = {"uvicorn", "flask", "gunicorn", "http.server"}
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BLOCKED_SHELLS = {"sh", "bash", "zsh", "cmd", "powershell", "pwsh", "cmd.exe"}
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def validate_custom_command_strict(cmd: str) -> None:
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"""
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@@ -90,46 +103,85 @@ def validate_custom_command_strict(cmd: str) -> None:
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base = Path(argv[0]).name.lower()
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# Block direct shells / interpreters commonly used for command injection
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if base in {"sh", "bash", "zsh", "cmd", "powershell", "pwsh"}:
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if base in BLOCKED_SHELLS:
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raise ValueError(f"custom_command runner not allowed: {base}")
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if base not in ALLOWED_RUNNERS:
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raise ValueError(f"custom_command runner not allowed: {base}")
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raise ValueError(
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f"custom_command runner not allowed: {base}. "
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f"Allowed: {', '.join(sorted(ALLOWED_RUNNERS))}"
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)
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# Block one-liner execution
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# Block one-liner execution for python
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lowered = [a.lower() for a in argv]
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if base in {"python", "python3"}:
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if "-c" in lowered:
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raise ValueError("python -c is not allowed")
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# Only allow: python -m uvicorn ...
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if len(argv) < 3 or argv[1:3] != ["-m", "uvicorn"]:
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raise ValueError("Only 'python -m uvicorn ...' is allowed")
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if len(argv) >= 3 and argv[1] == "-m":
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# Allow: python -m <allowed_module> ...
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if argv[2] not in ALLOWED_PYTHON_MODULES:
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raise ValueError(
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f"python -m {argv[2]} is not allowed. "
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f"Allowed modules: {', '.join(sorted(ALLOWED_PYTHON_MODULES))}"
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)
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elif len(argv) >= 2 and argv[1].endswith(".py"):
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# Allow: python manage.py runserver, python app.py, etc.
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pass
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else:
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raise ValueError(
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"Python commands must use 'python -m <module> ...' or 'python <script>.py ...'"
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)
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if base == "flask":
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# Allow: flask run [--host ...] [--port ...]
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if len(argv) < 2 or argv[1] != "run":
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raise ValueError("flask custom_command must be 'flask run [options]'")
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if base == "poetry":
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# Allow: poetry run <subcmd> ...
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if len(argv) < 3 or argv[1] != "run":
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raise ValueError("poetry custom_command must be 'poetry run <command> ...'")
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if base == "uvicorn":
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if len(argv) < 2 or ":" not in argv[1]:
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raise ValueError("uvicorn must specify an app like module:app")
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allowed_flags = {"--host", "--port", "--reload", "--log-level", "--workers"}
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i = 2
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while i < len(argv):
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a = argv[i]
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if a.startswith("-") and a not in allowed_flags:
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raise ValueError(f"uvicorn flag not allowed: {a}")
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i += 1
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for a in argv[2:]:
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if a.startswith("-"):
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# Handle --flag=value syntax
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flag_key = a.split("=", 1)[0]
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if flag_key not in allowed_flags:
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raise ValueError(f"uvicorn flag not allowed: {flag_key}")
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if base in {"npm", "pnpm", "yarn"}:
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# Allow only dev/start scripts (no arbitrary exec)
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# Allow only known safe scripts (no arbitrary exec)
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if base == "npm":
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if len(argv) < 3 or argv[1] != "run" or argv[2] not in {"dev", "start"}:
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raise ValueError("npm custom_command must be 'npm run dev' or 'npm run start'")
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if len(argv) < 3 or argv[1] != "run" or argv[2] not in ALLOWED_NPM_SCRIPTS:
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raise ValueError(
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f"npm custom_command must be 'npm run <script>' where script is one of: "
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f"{', '.join(sorted(ALLOWED_NPM_SCRIPTS))}"
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)
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elif base == "pnpm":
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ok = (len(argv) >= 2 and argv[1] in {"dev", "start"}) or (len(argv) >= 3 and argv[1] == "run" and argv[2] in {"dev", "start"})
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ok = (
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(len(argv) >= 2 and argv[1] in ALLOWED_NPM_SCRIPTS)
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or (len(argv) >= 3 and argv[1] == "run" and argv[2] in ALLOWED_NPM_SCRIPTS)
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)
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if not ok:
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raise ValueError("pnpm custom_command must be 'pnpm dev/start' or 'pnpm run dev/start'")
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raise ValueError(
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f"pnpm custom_command must use a known script: "
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f"{', '.join(sorted(ALLOWED_NPM_SCRIPTS))}"
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)
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elif base == "yarn":
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ok = (len(argv) >= 2 and argv[1] in {"dev", "start"}) or (len(argv) >= 3 and argv[1] == "run" and argv[2] in {"dev", "start"})
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ok = (
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(len(argv) >= 2 and argv[1] in ALLOWED_NPM_SCRIPTS)
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or (len(argv) >= 3 and argv[1] == "run" and argv[2] in ALLOWED_NPM_SCRIPTS)
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)
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if not ok:
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raise ValueError("yarn custom_command must be 'yarn dev/start' or 'yarn run dev/start'")
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raise ValueError(
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f"yarn custom_command must use a known script: "
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f"{', '.join(sorted(ALLOWED_NPM_SCRIPTS))}"
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)
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def get_project_devserver_manager(project_name: str):
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@@ -243,7 +295,7 @@ async def start_devserver(
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status_code=400,
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detail="Direct command execution is disabled. Use /config to set a safe custom_command."
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)
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command = get_dev_command(project_dir)
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if not command:
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@@ -255,6 +307,13 @@ async def start_devserver(
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# Validate command against security allowlist before execution
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validate_dev_command(command, project_dir)
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# Defense-in-depth: also run strict structural validation at execution time
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# (catches config file tampering that bypasses the /config endpoint)
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try:
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validate_custom_command_strict(command)
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except ValueError as e:
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raise HTTPException(status_code=400, detail=str(e))
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# Now command is definitely str and validated
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success, message = await manager.start(command)
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@@ -346,12 +405,17 @@ async def update_devserver_config(
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except ValueError as e:
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raise HTTPException(status_code=400, detail=str(e))
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else:
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# Validate command against security allowlist before persisting
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# Strict structural validation first (most specific errors)
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try:
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validate_custom_command_strict(update.custom_command)
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except ValueError as e:
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raise HTTPException(status_code=400, detail=str(e))
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# Then validate against security allowlist
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validate_dev_command(update.custom_command, project_dir)
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# Set the custom command
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try:
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validate_custom_command_strict(update.custom_command)
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set_dev_command(project_dir, update.custom_command)
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except ValueError as e:
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raise HTTPException(status_code=400, detail=str(e))
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