unsloth/studio/backend/core/inference/tools.py

# SPDX-License-Identifier: AGPL-3.0-only
# Copyright 2026-present the Unsloth AI Inc. team. All rights reserved. See /studio/LICENSE.AGPL-3.0

"""
Tool definitions and executors for LLM tool calling.

Supports web search (DuckDuckGo), Python code execution, and terminal commands.
"""

import ast
import os

os.environ["UNSLOTH_IS_PRESENT"] = "1"

import subprocess
import sys
import tempfile
import threading

from loggers import get_logger

logger = get_logger(__name__)

_EXEC_TIMEOUT = 300  # 5 minutes
_MAX_OUTPUT_CHARS = 8000  # truncate long output
_BASH_BLOCKED_WORDS = {"rm", "sudo", "dd", "chmod", "mkfs", "shutdown", "reboot"}

# Per-session working directories so each chat thread gets its own sandbox.
# Falls back to a shared ~/studio_sandbox/ for API callers without a session_id.
_workdirs: dict[str, str] = {}


def _get_workdir(session_id: str | None = None) -> str:
    """Return (and lazily create) a persistent working directory for tool execution."""
    global _workdirs
    key = session_id or "_default"
    if key not in _workdirs or not os.path.isdir(_workdirs[key]):
        home = os.path.expanduser("~")
        sandbox_root = os.path.join(home, "studio_sandbox")
        if session_id:
            # Sanitize: strip path separators and parent-dir references
            safe_id = os.path.basename(session_id.replace("..", ""))
            if not safe_id:
                safe_id = "_invalid"
            workdir = os.path.join(sandbox_root, safe_id)
            # Verify resolved path stays under sandbox root
            if not os.path.realpath(workdir).startswith(os.path.realpath(sandbox_root)):
                workdir = os.path.join(sandbox_root, "_invalid")
        else:
            workdir = sandbox_root
        os.makedirs(workdir, exist_ok = True)
        _workdirs[key] = workdir
    return _workdirs[key]


WEB_SEARCH_TOOL = {
    "type": "function",
    "function": {
        "name": "web_search",
        "description": (
            "Search the web and fetch page content. Returns snippets for all results. "
            "Use the url parameter to fetch full page text from a specific URL."
        ),
        "parameters": {
            "type": "object",
            "properties": {
                "query": {
                    "type": "string",
                    "description": "The search query",
                },
                "url": {
                    "type": "string",
                    "description": "A URL to fetch full page content from (instead of searching). Use this to read a page found in search results.",
                },
            },
            "required": [],
        },
    },
}

PYTHON_TOOL = {
    "type": "function",
    "function": {
        "name": "python",
        "description": "Execute Python code in a sandbox and return stdout/stderr.",
        "parameters": {
            "type": "object",
            "properties": {
                "code": {
                    "type": "string",
                    "description": "The Python code to run",
                }
            },
            "required": ["code"],
        },
    },
}

TERMINAL_TOOL = {
    "type": "function",
    "function": {
        "name": "terminal",
        "description": "Execute a terminal command and return stdout/stderr.",
        "parameters": {
            "type": "object",
            "properties": {
                "command": {
                    "type": "string",
                    "description": "The command to run",
                }
            },
            "required": ["command"],
        },
    },
}

ALL_TOOLS = [WEB_SEARCH_TOOL, PYTHON_TOOL, TERMINAL_TOOL]


_TIMEOUT_UNSET = object()


def execute_tool(
    name: str,
    arguments: dict,
    cancel_event = None,
    timeout: int | None = _TIMEOUT_UNSET,
    session_id: str | None = None,
) -> str:
    """Execute a tool by name with the given arguments. Returns result as a string.

    ``timeout``: int sets per-call limit in seconds, ``None`` means no limit,
    unset (default) uses ``_EXEC_TIMEOUT`` (300 s).
    ``session_id``: optional thread/session ID for per-conversation sandbox isolation.
    """
    logger.info(
        f"execute_tool: name={name}, session_id={session_id}, timeout={timeout}"
    )
    effective_timeout = _EXEC_TIMEOUT if timeout is _TIMEOUT_UNSET else timeout
    if name == "web_search":
        return _web_search(
            arguments.get("query", ""),
            url = arguments.get("url"),
            timeout = effective_timeout,
        )
    if name == "python":
        return _python_exec(
            arguments.get("code", ""), cancel_event, effective_timeout, session_id
        )
    if name == "terminal":
        return _bash_exec(
            arguments.get("command", ""), cancel_event, effective_timeout, session_id
        )
    return f"Unknown tool: {name}"


_MAX_PAGE_CHARS = 16000  # limit fetched page text
_MAX_FETCH_BYTES = _MAX_PAGE_CHARS * 4 + 1  # cap raw download size


def _validate_and_resolve_host(hostname: str, port: int) -> tuple[bool, str, str]:
    """Resolve *hostname*, reject non-public IPs, return a pinned IP string.

    Returns ``(ok, reason_or_empty, resolved_ip)``.  The caller should
    connect to *resolved_ip* (with a ``Host`` header) to prevent DNS
    rebinding between validation and the actual fetch.
    """
    import ipaddress
    import socket

    try:
        infos = socket.getaddrinfo(hostname, port, type = socket.SOCK_STREAM)
    except OSError as e:
        return False, f"Failed to resolve host: {e}", ""

    if not infos:
        return False, f"Failed to resolve host: no addresses for {hostname!r}", ""

    for *_, sockaddr in infos:
        ip = ipaddress.ip_address(sockaddr[0])
        if (
            ip.is_private
            or ip.is_loopback
            or ip.is_link_local
            or ip.is_multicast
            or ip.is_reserved
            or ip.is_unspecified
        ):
            return False, f"Blocked: refusing to fetch non-public address {ip}.", ""

    # Return the first resolved address for pinning
    first_ip = infos[0][4][0]
    return True, "", first_ip


def _fetch_page_text(
    url: str, max_chars: int = _MAX_PAGE_CHARS, timeout: int = 30
) -> str:
    """Fetch a URL and return plain text content (HTML tags stripped).

    Blocks private/loopback/link-local targets (SSRF protection) and caps
    the download size to avoid unbounded memory usage.
    """
    from urllib.parse import urlparse

    parsed = urlparse(url)
    if parsed.scheme not in ("http", "https"):
        return f"Blocked: only http/https URLs are allowed (got {parsed.scheme!r})."
    if not parsed.hostname:
        return "Blocked: URL is missing a hostname."

    port = parsed.port or (443 if parsed.scheme == "https" else 80)
    ok, reason, pinned_ip = _validate_and_resolve_host(parsed.hostname, port)
    if not ok:
        return reason

    try:
        import urllib.request
        from urllib.error import HTTPError as _HTTPError
        from urllib.parse import urljoin, urlunparse

        # Disable auto-redirect so we can validate each hop for SSRF.
        # urllib raises HTTPError for 3xx when the handler returns None,
        # so we catch that and extract the Location header manually.
        class _NoRedirect(urllib.request.HTTPRedirectHandler):
            def redirect_request(self, req, fp, code, msg, headers, newurl):
                return None

        opener = urllib.request.build_opener(_NoRedirect)
        max_bytes = max_chars * 4 + 1
        current_url = url
        current_host = parsed.hostname

        for _hop in range(5):
            # Pin to the validated IP to prevent DNS rebinding.
            # Rewrite the URL to use the IP and set the Host header.
            cp = urlparse(current_url)
            ip_netloc = f"{pinned_ip}:{cp.port}" if cp.port else pinned_ip
            pinned_url = urlunparse(cp._replace(netloc = ip_netloc))

            req = urllib.request.Request(
                pinned_url,
                headers = {
                    "User-Agent": "UnslothStudio/1.0",
                    "Host": current_host,
                },
            )
            try:
                resp = opener.open(req, timeout = timeout)
            except _HTTPError as e:
                if e.code not in (301, 302, 303, 307, 308):
                    return (
                        f"Failed to fetch URL: HTTP {e.code} {getattr(e, 'reason', '')}"
                    )
                location = e.headers.get("Location")
                if not location:
                    return "Failed to fetch URL: redirect missing Location header."
                current_url = urljoin(current_url, location)
                rp = urlparse(current_url)
                if rp.scheme not in ("http", "https") or not rp.hostname:
                    return "Blocked: redirect target is not a valid http/https URL."
                rp_port = rp.port or (443 if rp.scheme == "https" else 80)
                ok2, reason2, pinned_ip = _validate_and_resolve_host(
                    rp.hostname,
                    rp_port,
                )
                if not ok2:
                    return reason2
                current_host = rp.hostname
                continue
            # Success -- read capped body
            raw_bytes = resp.read(max_bytes)
            break
        else:
            return "Failed to fetch URL: too many redirects."

        charset = resp.headers.get_content_charset() or "utf-8"
        raw_html = raw_bytes.decode(charset, errors = "replace")
    except _HTTPError as e:
        return f"Failed to fetch URL: HTTP {e.code} {getattr(e, 'reason', '')}"
    except Exception as e:
        return f"Failed to fetch URL: {e}"

    # Convert HTML to Markdown using the builtin converter (no external deps)
    from ._html_to_md import html_to_markdown

    text = html_to_markdown(raw_html)

    if not text:
        return "(page returned no readable text)"
    if len(text) > max_chars:
        text = text[:max_chars] + f"\n\n... (truncated, {len(text)} chars total)"
    return text


def _web_search(
    query: str,
    max_results: int = 5,
    timeout: int = _EXEC_TIMEOUT,
    url: str | None = None,
) -> str:
    """Search the web using DuckDuckGo and return formatted results.

    If ``url`` is provided, fetches that page directly instead of searching.
    """
    # Direct URL fetch mode
    if url and url.strip():
        fetch_timeout = 60 if timeout is None else min(timeout, 60)
        return _fetch_page_text(url.strip(), timeout = fetch_timeout)

    if not query or not query.strip():
        return "No query provided."
    try:
        from ddgs import DDGS

        results = DDGS(timeout = timeout).text(query, max_results = max_results)
        if not results:
            return "No results found."
        parts = []
        for r in results:
            parts.append(
                f"Title: {r.get('title', '')}\n"
                f"URL: {r.get('href', '')}\n"
                f"Snippet: {r.get('body', '')}"
            )
        text = "\n\n---\n\n".join(parts)
        text += (
            "\n\n---\n\nIMPORTANT: These are only short snippets. "
            "To get the full page content, call web_search with "
            'the url parameter (e.g. {"url": "<URL>"}).'
        )
        return text
    except Exception as e:
        return f"Search failed: {e}"


def _check_signal_escape_patterns(code: str):
    """
    Check if code contains patterns that could escape signal-based timeouts.

    Vendored from unsloth_zoo.rl_environments to avoid importing unsloth_zoo
    (which requires GPU drivers and fails on Mac/Apple Silicon).

    Returns (safe: bool, details: dict)
    """
    try:
        tree = ast.parse(code)
    except SyntaxError as e:
        return False, {
            "error": f"SyntaxError: {e}",
            "signal_tampering": [],
            "exception_catching": [],
            "warnings": [],
        }

    signal_tampering = []
    exception_catching = []
    warnings = []

    def _ast_name_matches(node, names):
        if isinstance(node, ast.Name):
            return node.id in names
        elif isinstance(node, ast.Attribute):
            full_name = []
            current = node
            while isinstance(current, ast.Attribute):
                full_name.append(current.attr)
                current = current.value
            if isinstance(current, ast.Name):
                full_name.append(current.id)
            full_name = ".".join(reversed(full_name))
            return full_name in names
        return False

    class SignalEscapeVisitor(ast.NodeVisitor):
        def __init__(self):
            self.imports_signal = False
            self.signal_aliases = {"signal"}
            self.loop_depth = 0

        def visit_Import(self, node):
            for alias in node.names:
                if alias.name == "signal":
                    self.imports_signal = True
                    if alias.asname:
                        self.signal_aliases.add(alias.asname)
            self.generic_visit(node)

        def visit_ImportFrom(self, node):
            if node.module == "signal":
                self.imports_signal = True
                for alias in node.names:
                    if alias.name in (
                        "signal",
                        "SIGALRM",
                        "SIG_IGN",
                        "setitimer",
                        "ITIMER_REAL",
                        "pthread_sigmask",
                        "SIG_BLOCK",
                        "alarm",
                    ):
                        self.signal_aliases.add(alias.asname or alias.name)
            self.generic_visit(node)

        def visit_While(self, node):
            self.loop_depth += 1
            self.generic_visit(node)
            self.loop_depth -= 1

        def visit_For(self, node):
            self.loop_depth += 1
            self.generic_visit(node)
            self.loop_depth -= 1

        def visit_Call(self, node):
            func = node.func
            func_name = None
            if isinstance(func, ast.Attribute):
                if isinstance(func.value, ast.Name):
                    if func.value.id in self.signal_aliases:
                        func_name = f"signal.{func.attr}"
            elif isinstance(func, ast.Name):
                if func.id in ("signal", "setitimer", "alarm", "pthread_sigmask"):
                    func_name = func.id

            if func_name:
                if func_name in ("signal.signal", "signal"):
                    if len(node.args) >= 1:
                        if _ast_name_matches(
                            node.args[0], ("SIGALRM", "signal.SIGALRM")
                        ):
                            signal_tampering.append(
                                {
                                    "type": "signal_handler_override",
                                    "line": node.lineno,
                                    "description": "Overrides SIGALRM handler",
                                }
                            )
                elif func_name in ("signal.setitimer", "setitimer"):
                    if len(node.args) >= 1:
                        if _ast_name_matches(
                            node.args[0], ("ITIMER_REAL", "signal.ITIMER_REAL")
                        ):
                            signal_tampering.append(
                                {
                                    "type": "timer_manipulation",
                                    "line": node.lineno,
                                    "description": "Manipulates ITIMER_REAL timer",
                                }
                            )
                elif func_name in ("signal.alarm", "alarm"):
                    signal_tampering.append(
                        {
                            "type": "alarm_manipulation",
                            "line": node.lineno,
                            "description": "Manipulates alarm timer",
                        }
                    )
                elif func_name in ("signal.pthread_sigmask", "pthread_sigmask"):
                    signal_tampering.append(
                        {
                            "type": "signal_mask",
                            "line": node.lineno,
                            "description": "Modifies signal mask (may block SIGALRM)",
                        }
                    )
            self.generic_visit(node)

        def visit_ExceptHandler(self, node):
            if self.loop_depth == 0:
                self.generic_visit(node)
                return
            if node.type is None:
                exception_catching.append(
                    {
                        "type": "bare_except_in_loop",
                        "line": node.lineno,
                        "description": "Bare except in loop catches TimeoutError and continues looping",
                    }
                )
            elif isinstance(node.type, ast.Name):
                if node.type.id in ("TimeoutError", "BaseException", "Exception"):
                    exception_catching.append(
                        {
                            "type": f"catches_{node.type.id}_in_loop",
                            "line": node.lineno,
                            "description": f"Catches {node.type.id} in loop - may suppress timeout and continue",
                        }
                    )
            elif isinstance(node.type, ast.Tuple):
                for elt in node.type.elts:
                    if isinstance(elt, ast.Name):
                        if elt.id in ("TimeoutError", "BaseException", "Exception"):
                            exception_catching.append(
                                {
                                    "type": f"catches_{elt.id}_in_loop",
                                    "line": node.lineno,
                                    "description": f"Catches {elt.id} in loop - may suppress timeout and continue",
                                }
                            )
            self.generic_visit(node)

    visitor = SignalEscapeVisitor()
    visitor.visit(tree)

    if visitor.imports_signal and not signal_tampering:
        warnings.append("Code imports 'signal' module - review manually for safety")

    is_safe = len(signal_tampering) == 0 and len(exception_catching) == 0
    return is_safe, {
        "signal_tampering": signal_tampering,
        "exception_catching": exception_catching,
        "warnings": warnings,
    }


def _check_code_safety(code: str) -> str | None:
    """Validate code safety via static analysis.

    Returns an error message string if the code is unsafe, or None if OK.
    """
    safe, info = _check_signal_escape_patterns(code)
    if not safe:
        reasons = [
            item.get("description", "") for item in info.get("signal_tampering", [])
        ]
        return (
            f"Error: unsafe code detected ({'; '.join(reasons)}). "
            f"Please remove signal manipulation from your code."
        )

    return None


def _cancel_watcher(proc, cancel_event, poll_interval = 0.2):
    """Daemon thread that kills a process when cancel_event is set."""
    while proc.poll() is None:
        if cancel_event is not None and cancel_event.is_set():
            proc.kill()
            return
        cancel_event.wait(poll_interval) if cancel_event else None


def _truncate(text: str, limit: int = _MAX_OUTPUT_CHARS) -> str:
    if len(text) > limit:
        return text[:limit] + f"\n\n... (truncated, {len(text)} chars total)"
    return text


def _python_exec(
    code: str,
    cancel_event = None,
    timeout: int = _EXEC_TIMEOUT,
    session_id: str | None = None,
) -> str:
    """Execute Python code in a subprocess sandbox."""
    if not code or not code.strip():
        return "No code provided."

    # Validate imports and code safety
    error = _check_code_safety(code)
    if error:
        return error

    tmp_path = None
    workdir = _get_workdir(session_id)
    try:
        fd, tmp_path = tempfile.mkstemp(
            suffix = ".py", prefix = "studio_exec_", dir = workdir
        )
        with os.fdopen(fd, "w") as f:
            f.write(code)

        proc = subprocess.Popen(
            [sys.executable, tmp_path],
            stdout = subprocess.PIPE,
            stderr = subprocess.STDOUT,
            text = True,
            cwd = workdir,
        )

        # Spawn cancel watcher if we have a cancel event
        if cancel_event is not None:
            watcher = threading.Thread(
                target = _cancel_watcher, args = (proc, cancel_event), daemon = True
            )
            watcher.start()

        try:
            output, _ = proc.communicate(timeout = timeout)
        except subprocess.TimeoutExpired:
            proc.kill()
            proc.communicate()
            return _truncate(f"Execution timed out after {timeout} seconds.")

        if cancel_event is not None and cancel_event.is_set():
            return "Execution cancelled."

        result = output or ""
        if proc.returncode != 0:
            result = f"Exit code {proc.returncode}:\n{result}"
        return _truncate(result) if result.strip() else "(no output)"

    except Exception as e:
        return f"Execution error: {e}"
    finally:
        if tmp_path and os.path.exists(tmp_path):
            try:
                os.unlink(tmp_path)
            except OSError:
                pass


def _bash_exec(
    command: str,
    cancel_event = None,
    timeout: int = _EXEC_TIMEOUT,
    session_id: str | None = None,
) -> str:
    """Execute a bash command in a subprocess sandbox."""
    if not command or not command.strip():
        return "No command provided."

    # Block dangerous commands
    tokens = set(command.lower().split())
    blocked = tokens & _BASH_BLOCKED_WORDS
    if blocked:
        return f"Blocked command(s) for safety: {', '.join(sorted(blocked))}"

    try:
        workdir = _get_workdir(session_id)
        proc = subprocess.Popen(
            ["bash", "-c", command],
            stdout = subprocess.PIPE,
            stderr = subprocess.STDOUT,
            text = True,
            cwd = workdir,
        )

        if cancel_event is not None:
            watcher = threading.Thread(
                target = _cancel_watcher, args = (proc, cancel_event), daemon = True
            )
            watcher.start()

        try:
            output, _ = proc.communicate(timeout = timeout)
        except subprocess.TimeoutExpired:
            proc.kill()
            proc.communicate()
            return _truncate(f"Execution timed out after {timeout} seconds.")

        if cancel_event is not None and cancel_event.is_set():
            return "Execution cancelled."

        result = output or ""
        if proc.returncode != 0:
            result = f"Exit code {proc.returncode}:\n{result}"
        return _truncate(result) if result.strip() else "(no output)"

    except Exception as e:
        return f"Execution error: {e}"