fix(lsp): add depth/file/timeout limits to detect_directory_languages() to prevent DoS
Added robust guards to detect_directory_languages() by introducing depth, file count, and timeout controls. Defaults and validations are implemented to prevent resource exhaustion during LSP discovery. - Added max_depth parameter (default: 50) with validation to ensure a positive integer. - Added max_files parameter (default: 10,000) with validation to ensure a positive integer. - Added timeout parameter (default: 30.0 seconds) with validation to ensure a positive float. - Pass followlinks=False to os.walk() to prevent symlink-based DoS via recursive loops. - Implemented depth tracking in the traversal loop with early break when max_depth is exceeded. - Implemented file count tracking with early break when max_files is exceeded. - Implemented periodic timeout checks during traversal to enforce the overall time limit. - Added warning logging when traversal is terminated early due to any limit. - Updated the function docstring to document the new parameters and their defaults. - Created comprehensive BDD tests in features/lsp_discovery_dos_protection.feature to validate the protections. ISSUES CLOSED: #7161
This commit is contained in:
@@ -0,0 +1,83 @@
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Feature: LSP language discovery DoS protection
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Prevent resource exhaustion attacks via directory traversal limits.
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Issue #7161: Resource exhaustion DoS in LSP language discovery.
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# ------------------------------------------------------------------
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# Depth limit protection (prevents deep nesting attacks)
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# ------------------------------------------------------------------
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@tdd_issue_7161
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Scenario: detect_directory_languages respects max_depth limit
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Given ldos a LanguageDiscovery instance
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And ldos a mock directory tree with depth 10
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When ldos I detect directory languages with max_depth 5
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Then ldos the result is a list
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@tdd_issue_7161
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Scenario: detect_directory_languages allows traversal within max_depth
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Given ldos a LanguageDiscovery instance
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And ldos a mock directory tree with depth 3
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When ldos I detect directory languages with max_depth 5
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Then ldos the result is a list
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# ------------------------------------------------------------------
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# File count limit protection (prevents wide directory attacks)
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# ------------------------------------------------------------------
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@tdd_issue_7161
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Scenario: detect_directory_languages respects max_files limit
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Given ldos a LanguageDiscovery instance
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And ldos a mock directory with 1000 files
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When ldos I detect directory languages with max_files 100
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Then ldos the result is a list
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@tdd_issue_7161
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Scenario: detect_directory_languages allows processing within max_files
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Given ldos a LanguageDiscovery instance
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And ldos a mock directory with 50 files
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When ldos I detect directory languages with max_files 100
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Then ldos the result is a list
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# ------------------------------------------------------------------
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# Symlink loop protection (prevents circular traversal)
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# ------------------------------------------------------------------
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@tdd_issue_7161
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Scenario: detect_directory_languages does not follow symlinks
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Given ldos a LanguageDiscovery instance
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And ldos a mock directory with symlinks
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When ldos I detect directory languages
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Then ldos the result is a list
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# ------------------------------------------------------------------
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# Parameter validation
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# ------------------------------------------------------------------
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@tdd_issue_7161
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Scenario: detect_directory_languages rejects invalid max_depth
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Given ldos a LanguageDiscovery instance
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When ldos I detect directory languages with max_depth 0
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Then ldos a ValueError is raised
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@tdd_issue_7161
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Scenario: detect_directory_languages rejects invalid max_files
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Given ldos a LanguageDiscovery instance
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When ldos I detect directory languages with max_files 0
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Then ldos a ValueError is raised
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@tdd_issue_7161
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Scenario: detect_directory_languages rejects invalid timeout
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Given ldos a LanguageDiscovery instance
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When ldos I detect directory languages with timeout 0.0
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Then ldos a ValueError is raised
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# ------------------------------------------------------------------
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# Default parameter values
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# ------------------------------------------------------------------
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@tdd_issue_7161
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Scenario: detect_directory_languages uses default limits
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Given ldos a LanguageDiscovery instance
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And ldos a mock directory with 100 files
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When ldos I detect directory languages without explicit limits
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Then ldos the result is a list
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@@ -0,0 +1,171 @@
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"""Step definitions for lsp_discovery_dos_protection.feature.
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Tests for DoS protection in detect_directory_languages():
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- max_depth parameter prevents deep nesting attacks
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- max_files parameter prevents wide directory attacks
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- timeout parameter prevents indefinite traversal
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- followlinks=False prevents symlink loop attacks
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- Parameter validation rejects invalid values
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"""
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from __future__ import annotations
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from unittest.mock import patch
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from behave import given, then, when
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from behave.runner import Context
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from cleveragents.lsp.discovery import LanguageDiscovery
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# ── LanguageDiscovery instance ───────────────────────────────────────
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@given("ldos a LanguageDiscovery instance")
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def step_ldos_given_discovery(context: Context) -> None:
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context.ldos_discovery = LanguageDiscovery()
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context.ldos_exception = None
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context.ldos_result = None
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# ── Mock directory trees ─────────────────────────────────────────────
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@given("ldos a mock directory tree with depth {depth:d}")
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def step_ldos_given_deep_tree(context: Context, depth: int) -> None:
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"""Create a mock os.walk that yields nested directories."""
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walk_results = []
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for d in range(depth):
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root = "/fake" + "/level" * d
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dirs = ["level"] if d < depth - 1 else []
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files = [f"file{d}.py"]
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walk_results.append((root, dirs, files))
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patcher_walk = patch(
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"cleveragents.lsp.discovery.os.walk",
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return_value=iter(walk_results),
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)
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patcher_walk.start()
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context.add_cleanup(patcher_walk.stop)
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# Mock open to avoid real file I/O
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patcher_open = patch("builtins.open", side_effect=OSError("mocked"))
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patcher_open.start()
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context.add_cleanup(patcher_open.stop)
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@given("ldos a mock directory with {count:d} files")
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def step_ldos_given_wide_tree(context: Context, count: int) -> None:
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"""Create a mock os.walk that yields many files in one directory."""
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filenames = [f"file{i}.py" for i in range(count)]
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walk_results = [("/fake/project", [], filenames)]
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patcher_walk = patch(
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"cleveragents.lsp.discovery.os.walk",
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return_value=iter(walk_results),
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)
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patcher_walk.start()
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context.add_cleanup(patcher_walk.stop)
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# Mock open to avoid real file I/O
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patcher_open = patch("builtins.open", side_effect=OSError("mocked"))
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patcher_open.start()
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context.add_cleanup(patcher_open.stop)
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@given("ldos a mock directory with symlinks")
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def step_ldos_given_symlink_tree(context: Context) -> None:
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"""Create a mock os.walk that would loop with followlinks=True."""
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walk_results = [
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("/fake/project", ["subdir"], ["file.py"]),
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("/fake/project/subdir", [], ["file2.py"]),
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]
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# Capture the followlinks argument
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context.ldos_followlinks_arg = None
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def capture_walk(directory: str, followlinks: bool = True) -> None:
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context.ldos_followlinks_arg = followlinks
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return iter(walk_results)
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patcher_walk = patch(
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"cleveragents.lsp.discovery.os.walk",
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side_effect=capture_walk,
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)
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patcher_walk.start()
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context.add_cleanup(patcher_walk.stop)
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# Mock open to avoid real file I/O
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patcher_open = patch("builtins.open", side_effect=OSError("mocked"))
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patcher_open.start()
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context.add_cleanup(patcher_open.stop)
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# ── Detect directory languages with limits ───────────────────────────
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@when("ldos I detect directory languages with max_depth {max_depth:d}")
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def step_ldos_when_detect_with_depth(context: Context, max_depth: int) -> None:
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"""Call detect_directory_languages with a specific max_depth."""
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try:
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context.ldos_result = context.ldos_discovery.detect_directory_languages(
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"/fake/project",
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max_depth=max_depth,
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)
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except ValueError as e:
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context.ldos_exception = e
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@when("ldos I detect directory languages with max_files {max_files:d}")
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def step_ldos_when_detect_with_files(context: Context, max_files: int) -> None:
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"""Call detect_directory_languages with a specific max_files."""
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try:
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context.ldos_result = context.ldos_discovery.detect_directory_languages(
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"/fake/project",
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max_files=max_files,
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)
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except ValueError as e:
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context.ldos_exception = e
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@when("ldos I detect directory languages with timeout {timeout:f}")
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def step_ldos_when_detect_with_timeout(context: Context, timeout: float) -> None:
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"""Call detect_directory_languages with a specific timeout."""
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try:
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context.ldos_result = context.ldos_discovery.detect_directory_languages(
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"/fake/project",
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timeout=timeout,
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)
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except ValueError as e:
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context.ldos_exception = e
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@when("ldos I detect directory languages without explicit limits")
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def step_ldos_when_detect_default(context: Context) -> None:
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"""Call detect_directory_languages with default parameters."""
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context.ldos_result = context.ldos_discovery.detect_directory_languages(
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"/fake/project",
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)
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@when("ldos I detect directory languages")
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def step_ldos_when_detect(context: Context) -> None:
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"""Call detect_directory_languages with default parameters."""
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context.ldos_result = context.ldos_discovery.detect_directory_languages(
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"/fake/project",
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)
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# ── Assertions ───────────────────────────────────────────────────────
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@then("ldos the result is a list")
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def step_ldos_then_result_list(context: Context) -> None:
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"""Verify that the result is a list."""
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assert isinstance(context.ldos_result, list)
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@then("ldos a ValueError is raised")
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def step_ldos_then_value_error(context: Context) -> None:
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"""Verify that a ValueError was raised."""
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assert context.ldos_exception is not None
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assert isinstance(context.ldos_exception, ValueError)
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@@ -24,6 +24,7 @@ Based on ``docs/specification.md`` Resource Language Discovery
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from __future__ import annotations
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import os
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import time
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from typing import Any
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import structlog
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@@ -204,26 +205,101 @@ class LanguageDiscovery:
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self._cache[file_path] = lang
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return lang
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def detect_directory_languages(self, directory: str) -> list[str]:
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def detect_directory_languages(
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self,
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directory: str,
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max_depth: int = 50,
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max_files: int = 10000,
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timeout: float = 30.0,
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) -> list[str]:
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"""Discover all languages present in a directory tree.
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Walks the directory, detects each file's language, and returns
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a deduplicated sorted list.
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a deduplicated sorted list. Enforces configurable limits on
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traversal depth, file count, and execution time to prevent
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resource exhaustion DoS attacks.
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Args:
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directory: Root directory to scan.
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max_depth: Maximum directory depth to traverse (default: 50).
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Prevents deep nesting attacks.
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max_files: Maximum number of files to process (default: 10,000).
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Prevents wide directory attacks.
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timeout: Maximum execution time in seconds (default: 30.0).
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Prevents indefinite traversal.
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Returns:
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Sorted list of unique language identifiers.
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"""
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if max_depth < 1:
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raise ValueError("max_depth must be >= 1")
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if max_files < 1:
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raise ValueError("max_files must be >= 1")
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if timeout <= 0:
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raise ValueError("timeout must be > 0")
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languages: set[str] = set()
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file_count = 0
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start_time = time.time()
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try:
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for root, _dirs, files in os.walk(directory):
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for root, _dirs, files in os.walk(directory, followlinks=False):
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# Check timeout
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elapsed = time.time() - start_time
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if elapsed > timeout:
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logger.warning(
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"lsp.discovery.timeout_exceeded",
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directory=directory,
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timeout=timeout,
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elapsed=elapsed,
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files_processed=file_count,
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)
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break
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# Calculate current depth
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depth = root[len(directory):].count(os.sep)
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if depth > max_depth:
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logger.warning(
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"lsp.discovery.max_depth_exceeded",
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directory=directory,
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max_depth=max_depth,
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current_depth=depth,
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)
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break
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for fname in files:
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# Check file count limit
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if file_count >= max_files:
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logger.warning(
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"lsp.discovery.max_files_exceeded",
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directory=directory,
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max_files=max_files,
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files_processed=file_count,
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)
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break
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# Check timeout again before processing each file
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elapsed = time.time() - start_time
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if elapsed > timeout:
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logger.warning(
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"lsp.discovery.timeout_exceeded",
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directory=directory,
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timeout=timeout,
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elapsed=elapsed,
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files_processed=file_count,
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)
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break
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fpath = os.path.join(root, fname)
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lang = self.detect_file_language(fpath)
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if lang != "plaintext":
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languages.add(lang)
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file_count += 1
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# Break outer loop if file count exceeded
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if file_count >= max_files:
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break
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except OSError:
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logger.warning(
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"lsp.discovery.walk_error",
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