team-tryouts/tests/test_csp.py

"""Content Security Policy.

SEC-WEB-001 / OPS-010. script-src no longer carries 'unsafe-inline': the
directive that let the stored XSS of SEC-XSS-001 execute instead of being
blocked. Inline scripts are authorised by a per-request nonce, and every
inline event handler has been replaced by a data-action attribute
dispatched from main.js.

Getting here took removing 82 handlers across 17 templates, because a nonce
authorises `<script>` elements and can do nothing for `onclick`. These
tests keep it that way: one new inline handler, and the policy silently
stops applying to that page.
"""

import os
import re

import pytest

from app.app import build_csp

TEMPLATE_ROOT = os.path.join(
    os.path.dirname(os.path.dirname(os.path.abspath(__file__))),
    'app', 'templates',
)

#: Attributes a nonce can never authorise.
INLINE_HANDLER = re.compile(
    r'\son(?:click|change|submit|input|load|keyup|keydown|mouseover|focus|blur)\s*=',
    re.I,
)

#: Remaining inline handlers, per template. Lower these as you migrate;
#: never raise one. Templates absent from this map must have none.
#: No template may carry an inline event handler. The migration is done;
#: this is now a hard rule, not a countdown.
HANDLER_BUDGET = {}

#: What the ratchet is counting down to.
TOTAL_BUDGET = sum(HANDLER_BUDGET.values())


def _templates():
    for root, _dirs, files in os.walk(TEMPLATE_ROOT):
        for name in files:
            if name.endswith('.html'):
                full = os.path.join(root, name)
                rel = os.path.relpath(full, TEMPLATE_ROOT).replace(os.sep, '/')
                yield rel, full


def _count_handlers(path):
    with open(path, encoding='utf-8') as handle:
        return len(INLINE_HANDLER.findall(handle.read()))


class TestPolicyHeader:
    def test_script_src_no_longer_allows_inline(self, client):
        csp = client.get('/auth/login').headers['Content-Security-Policy']
        script_src = next(d for d in csp.split(';') if 'script-src' in d)

        assert "'unsafe-inline'" not in script_src
        assert "'nonce-" in script_src

    def test_the_policy_pins_the_dangerous_directives(self, client):
        csp = client.get('/auth/login').headers['Content-Security-Policy']

        assert "default-src 'self'" in csp
        assert "frame-ancestors 'none'" in csp
        assert "base-uri 'self'" in csp
        assert "form-action 'self'" in csp
        assert "object-src" not in csp or "object-src 'none'" in csp

    def test_the_legacy_mode_still_builds(self):
        """The escape hatch is kept for a deployment that hits an overlooked
        handler. Emitting both would be pointless: a nonce makes browsers
        ignore 'unsafe-inline' entirely."""
        csp = build_csp(allow_inline_script=True)

        assert "'unsafe-inline'" in csp
        assert 'nonce-' not in csp

    def test_the_hardened_policy_carries_a_nonce_and_no_unsafe_inline(self):
        csp = build_csp(allow_inline_script=False, nonce='abc123')

        assert "'nonce-abc123'" in csp
        assert "'unsafe-inline'" not in csp.split('style-src')[0]

    def test_each_request_gets_a_distinct_nonce(self, app):
        """A reused nonce is worth no more than 'unsafe-inline'."""
        application = app
        application.config['CSP_ALLOW_INLINE_SCRIPT'] = False
        client = application.test_client()

        seen = set()
        for _ in range(5):
            csp = client.get('/auth/login').headers['Content-Security-Policy']
            seen.add(re.search(r"'nonce-([^']+)'", csp).group(1))

        assert len(seen) == 5


class TestInlineHandlerRatchet:
    @pytest.mark.parametrize('relative,full', list(_templates()))
    def test_a_template_never_gains_an_inline_handler(self, relative, full):
        allowed = HANDLER_BUDGET.get(relative, 0)
        found = _count_handlers(full)

        assert found <= allowed, (
            f'{relative} has {found} inline event handler(s), budget is '
            f'{allowed}. A nonce cannot authorise these — use '
            f'data-action="..." and the delegated listener in main.js.'
        )

    def test_every_inline_script_block_carries_a_nonce(self):
        """Without a nonce a block is simply not executed now, and nothing
        in the server logs says so."""
        import re as _re

        offenders = []
        for relative, full in _templates():
            with open(full, encoding='utf-8') as handle:
                content = handle.read()
            for tag in _re.findall(r'<script[^>]*>', content):
                if 'src=' in tag or 'nonce=' in tag:
                    continue
                offenders.append(f'{relative}: {tag}')

        assert not offenders, (
            'inline <script> without nonce="{{ csp_nonce }}": ' + str(offenders)
        )

    def test_the_shared_layout_is_free_of_them(self):
        """base.html and macros.html render on every single page."""
        for relative in ('layouts/base.html', 'layouts/macros.html'):
            full = os.path.join(TEMPLATE_ROOT, *relative.split('/'))
            assert _count_handlers(full) == 0, f'{relative} regressed'

    def test_no_template_carries_an_inline_handler(self):
        total = sum(_count_handlers(full) for _rel, full in _templates())

        assert total == 0, (
            f'{total} inline event handler(s) reintroduced. They are not '
            f'covered by the nonce, so they will not run — use '
            f'data-action="..." and registerActions() instead.'
        )