"""Tests for filesystem path safety primitives."""

from pathlib import Path

import pytest

from mcp.shared.path_security import (

PathEscapeError,

contains_path_traversal,

is_absolute_path,

safe_join,

)

@pytest.mark.parametrize(

("value", "expected"),

[

# Safe: no traversal

("a/b/c", False),

("readme.txt", False),

("", False),

(".", False),

("./a/b", False),

# Safe: .. balanced by prior descent

("a/../b", False),

("a/b/../c", False),

("a/b/../../c", False),

# Unsafe: net escape

("..", True),

("../etc", True),

("../../etc/passwd", True),

("a/../../b", True),

("./../../etc", True),

# .. as substring, not component — safe

("1.0..2.0", False),

("foo..bar", False),

("..foo", False),

("foo..", False),

# Backslash separator

("..\\etc", True),

("a\\..\\..\\b", True),

("a\\b\\c", False),

# Mixed separators

("a/..\\..\\b", True),

],

)

def test_contains_path_traversal(value: str, expected: bool):

assert contains_path_traversal(value) is expected

@pytest.mark.parametrize(

("value", "expected"),

[

# Relative

("relative/path", False),

("file.txt", False),

("", False),

(".", False),

("..", False),

# POSIX absolute

("/", True),

("/etc/passwd", True),

("/a", True),

# Windows drive

("C:", True),

("C:\\Windows", True),

("c:/foo", True),

("Z:\\", True),

# Windows UNC / backslash-absolute

("\\\\server\\share", True),

("\\foo", True),

# Windows drive-relative — discards the join base when drives differ

("C:relative", True),

("x:y", True),

("a:debug", True),

# Not a drive: digit before colon

("1:foo", False),

# Colon not in position 1

("ab:c", False),

# Non-ASCII letter is not a drive letter

("Ω:namespace", False),

("é:foo", False),

],

)

def test_is_absolute_path(value: str, expected: bool):

assert is_absolute_path(value) is expected

def test_safe_join_simple(tmp_path: Path):

result = safe_join(tmp_path, "docs", "readme.txt")

assert result == tmp_path / "docs" / "readme.txt"

def test_safe_join_resolves_relative_base(tmp_path: Path, monkeypatch: pytest.MonkeyPatch):

monkeypatch.chdir(tmp_path)

result = safe_join(".", "file.txt")

assert result == tmp_path / "file.txt"

def test_safe_join_rejects_dotdot_escape(tmp_path: Path):

with pytest.raises(PathEscapeError, match="escapes base"):

safe_join(tmp_path, "../../../etc/passwd")

def test_safe_join_rejects_balanced_then_escape(tmp_path: Path):

with pytest.raises(PathEscapeError, match="escapes base"):

safe_join(tmp_path, "a/../../etc")

def test_safe_join_allows_balanced_dotdot(tmp_path: Path):

result = safe_join(tmp_path, "a/../b")

assert result == tmp_path / "b"

def test_safe_join_rejects_absolute_part(tmp_path: Path):

with pytest.raises(PathEscapeError, match="is absolute"):

safe_join(tmp_path, "/etc/passwd")

def test_safe_join_rejects_absolute_in_later_part(tmp_path: Path):

with pytest.raises(PathEscapeError, match="is absolute"):

safe_join(tmp_path, "docs", "/etc/passwd")

def test_safe_join_rejects_windows_drive(tmp_path: Path):

with pytest.raises(PathEscapeError, match="is absolute"):

safe_join(tmp_path, "C:\\Windows\\System32")

def test_safe_join_rejects_null_byte(tmp_path: Path):

with pytest.raises(PathEscapeError, match="null byte"):

safe_join(tmp_path, "file\0.txt")

def test_safe_join_rejects_null_byte_in_later_part(tmp_path: Path):

with pytest.raises(PathEscapeError, match="null byte"):

safe_join(tmp_path, "docs", "file\0.txt")

def test_safe_join_rejects_symlink_escape(tmp_path: Path):

outside = tmp_path / "outside"

outside.mkdir()

sandbox = tmp_path / "sandbox"

sandbox.mkdir()

(sandbox / "escape").symlink_to(outside)

with pytest.raises(PathEscapeError, match="escapes base"):

safe_join(sandbox, "escape", "secret.txt")

def test_safe_join_base_equals_target(tmp_path: Path):

# Joining nothing (or ".") should return the base itself

assert safe_join(tmp_path) == tmp_path

assert safe_join(tmp_path, ".") == tmp_path

def test_path_escape_error_is_value_error():

with pytest.raises(ValueError):

safe_join("/tmp", "/etc")