Feat: Use per-request nonce in CSP to remove 'unsafe-inline' / 'unsafe-eval' - #10308
Feat: Use per-request nonce in CSP to remove 'unsafe-inline' / 'unsafe-eval'#10308hiteshjambhale wants to merge 8 commits into
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…al' (pgadmin-org#7599) Harden the default Content-Security-Policy so inline scripts run only via a per-request nonce instead of a blanket 'unsafe-inline', and drop 'unsafe-eval'. - Generate a per-request nonce (secrets.token_urlsafe) cached on flask.g so the exact same value is emitted in templates and the CSP response header. - Substitute a {nonce} placeholder in CONTENT_SECURITY_POLICY at runtime. - Tag inline <script>/<style> tags, and set window.__webpack_nonce__ so webpack's dynamically injected assets carry the nonce too. - New default: script-src 'self' 'nonce-{nonce}' (no 'unsafe-inline'/'unsafe-eval'). - style-src keeps 'unsafe-inline': MUI/React inject un-nonced runtime styles and inline style="" attributes that cannot be nonced. - 'unsafe-eval' is not needed by production bundles; the dev ('eval' devtool) bundles add it via config_local.py (documented in config.py). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Included review availability: Your plan provides up to 8 included reviews per hour; 7 remain after this review. WalkthroughThe application now generates one CSP nonce per request. The resolved nonce is emitted in the CSP header and passed to inline scripts and styles through the template context. Tests cover nonce generation, policy resolution, debug-mode handling, and header emission. ChangesContent Security Policy nonce enforcement
Estimated code review effort: 3 (Moderate) | ~20 minutes Merge Risk: 🔵 Low · up to The PR strengthens script execution policy by replacing blanket inline and eval allowances with per-request nonces. It is otherwise mergeable, but the current head contains a misleading keyring configuration test that should be removed or corrected to avoid encoding incorrect behavior. Suggested reviewers: Sequence Diagram(s)sequenceDiagram
participant Browser
participant FlaskRequest
participant SecurityHeaders
participant Templates
Browser->>FlaskRequest: request page
FlaskRequest->>SecurityHeaders: resolve Content-Security-Policy
SecurityHeaders-->>FlaskRequest: return nonce-bearing CSP header
FlaskRequest->>Templates: provide csp_nonce
Templates-->>Browser: render nonce-bearing scripts and styles
🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Pull request overview
Adds per-request CSP nonces to restrict inline script execution and remove the default reliance on 'unsafe-eval'.
Changes:
- Generates and injects request-scoped CSP nonces.
- Updates the default CSP and template script/style tags.
- Attempts to propagate the nonce to dynamically loaded Webpack assets.
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
web/config.py |
Defines the nonce-based default CSP. |
web/pgadmin/__init__.py |
Exposes the nonce to templates. |
web/pgadmin/utils/security_headers.py |
Generates nonces and substitutes the CSP placeholder. |
web/pgadmin/templates/base.html |
Adds nonces to shared scripts and styles. |
web/pgadmin/templates/security/render_page.html |
Nonces security-page styles. |
web/pgadmin/tools/debugger/templates/debugger/direct.html |
Nonces debugger styles. |
web/pgadmin/tools/erd/templates/erd/index.html |
Nonces ERD styles. |
web/pgadmin/tools/psql/templates/psql/index.html |
Nonces PSQL styles. |
web/pgadmin/tools/schema_diff/templates/schema_diff/index.html |
Nonces schema-diff styles. |
web/pgadmin/tools/sqleditor/templates/sqleditor/index.html |
Nonces SQL editor styles. |
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Setting window.__webpack_nonce__ in HTML is a no-op: webpack only substitutes the __webpack_nonce__ identifier inside compiled modules, and MUI/emotion does not read it either (it requires an explicit createCache nonce). Same-origin webpack chunks are already allowed by script-src 'self', so the block did nothing. Remove it; the resourceBasePath inline script keeps its nonce.
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I've reviewed this and, rather than take the 'unsafe-eval' question on trust, ran the branch locally to check it. In short: the mechanism is correct and the template coverage is complete, and I could not break the app with the committed policy. I have no blockers, although I would like the development case handled automatically and some test coverage added.
What I verified
Running this branch with the policy exactly as committed (web/config.py:165):
/loginreturns 200 withscript-src 'self' 'nonce-<value>', and every one of the 12 nonce-tagged elements in the page carries exactly the nonce sent in the header. Scanning the same HTML for<script>/<style>tags without a nonce found none.- The nonce is freshly generated per request.
- A custom policy containing no
{nonce}token is passed through byte for byte, and an empty policy suppresses the header entirely, so existing deployments that override this setting are unaffected. - Grepping the whole branch for inline
<script>/<style>, everything Flask renders is tagged. The only untagged ones left areruntime/src/html/*.html, and those are loaded by Electron withloadFile()straight from disk rather than served by Flask, so the header never applies to them. - The full application boots under the strict policy in Chromium (menu bar, workspace switcher, Object Explorer, Dashboard) with zero console errors, which also confirms that the scripts RequireJS injects dynamically are fine, since
'self'covers them.
On 'unsafe-eval', the production bundles do contain new Function call sites, so I chased each one. Webpack's globalThis probe in app.bundle.js is short-circuited by a typeof globalThis check and try/caught anyway. The remainder arrive via vanilla-jsoneditor: ajv's runtime schema compiler, jsonpath-plus, and the lodash/JavaScript query languages. None of them are reachable as pgAdmin configures the editor, because JsonEditor.jsx passes neither a validator (so ajv never compiles anything) nor queryLanguages, which leaves only the default JSON Query language registered, and that one composes closures rather than evaluating source. I confirmed that empirically by serving the editor from a page with the exact committed policy and running a transform (.items | filter(.n >= 2)) through the Transform dialog: it previewed and applied correctly, with no CSP violation raised. So the claim in the PR description holds, at least for the current configuration.
🟡 Development bundles will fail with no clue as to why
webpack.config.js:39 sets devtool: 'eval' for anything other than a production build, so a developer running a dev bundle gets a blank page plus a CSP violation in the console until they discover the config_local.py incantation in the comment at web/config.py:157-164. It would be kinder to handle it automatically, and since config_local is merged into config only after config.py has been evaluated, a conditional in config.py itself would not see an overridden DEBUG. The natural home is get_content_security_policy() in security_headers.py:40, which already runs per request: when config.DEBUG is set and the policy carries a nonce, add 'unsafe-eval' to script-src. base.html already branches on config.DEBUG to choose between require.js and require.min.js, so that would be consistent with how the codebase treats dev builds.
🟡 No test coverage
Nothing here is covered by a test, and the failure modes are quiet: someone adding an inline <script> to a template in six months' time will not find out from the suite. Three cheap assertions would lock the behaviour down: that the header nonce matches the nonce on the rendered page's inline tags, that a policy without {nonce} is passed through unchanged, and that the page contains no untagged inline <script>/<style>.
One gotcha for whoever writes it: regression/runtests.py pushes a long-lived app context (app.app_context().push()), and because the nonce is cached on flask.g, which is bound to the app context rather than the request, every request inside that harness sees the same nonce. I hit exactly that whilst testing and it is an artefact of the harness, not a bug in the patch: without the pushed context each request gets a fresh nonce, as it does in normal serving. Still, a "fresh per request" assertion written inside the regression harness will fail misleadingly, and it is worth knowing that the freshness guarantee rests on one app context per request.
🟢 Cheap hardening whilst in the neighbourhood
object-src falls back to default-src, which permits data:, and that is a venerable plugin-based XSS vector; base-uri has no fallback to default-src at all, so <base> injection is currently unconstrained. Adding object-src 'none'; base-uri 'self'; form-action 'self'; costs nothing and sits squarely within the intent of this PR.
ℹ️ Notes
- The eval-capable libraries are bundled even though they are unreachable today, so if anyone later enables a JSON schema validator or additional query languages for the JSON editor,
'unsafe-eval'becomes necessary again. Worth a line in theconfig.pycomment so the connection is not lost. - The value of locking down
script-srcis partly undercut bydefault-src ... http:, which leavesimg-srcandconnect-srcopen to any host: an injection that did land would still have an exfiltration channel. That is the pre-existing default rather than anything introduced here, and tightening it risks breaking user-configured external resources, so it is follow-up material rather than a change for this PR. - The nonces on
<style>tags are inert at present, sincestyle-srckeeps'unsafe-inline'. They are harmless and future-proof, but it is worth stating outright in the comment that adding'nonce-{nonce}'tostyle-srcwill disable'unsafe-inline'and break MUI's runtime styles, because that is a natural next step for someone tightening the policy further. - On the Copilot comment about
window.__webpack_nonce__: it was right as written, and b53ffaf resolves it the right way by deleting the assignment rather than plumbing it through the entry points. Webpack loads chunks as same-originsrcscripts, which'self'already permits, and the<style>elements its style-loader injects are covered bystyle-src 'unsafe-inline', so there is nothing left for the nonce to do there.
CI is still running as I write this; the feature test jobs are the meaningful gate for the UI, since they build a production bundle and drive the real application.
Development bundles are built with webpack's 'eval' devtool, which the strict nonce policy blocks, forcing developers to manually add 'unsafe-eval' via config_local.py. Handle it automatically in get_content_security_policy() (which runs per request and therefore sees a DEBUG value overridden in config_local): when config.DEBUG is set and the policy uses a nonce, append 'unsafe-eval' to the script-src directive, without duplicating it. Production is unaffected and custom (non-nonce) policies pass through untouched.
Adds unit tests covering nonce generation/caching/per-request freshness, {nonce} substitution, pass-through of custom/None/empty policies, header emission, and the dev-mode behaviour (including the no-script-src edge case, exact script-src name matching, and no-duplication).
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Inline comments:
In `@web/pgadmin/utils/tests/test_security_headers.py`:
- Around line 18-29: Remove the “PLANNED / DEV-MODE” and “EXPECTED TO FAIL”
wording from the security-header test comments, including the repeated instances
at the referenced test sections. Keep the regression test descriptions and
assertions unchanged.
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Hi @dpage Thanks for taking time to review the PR 1. Dev case handled automatically ( 2. Test coverage |
The dev-mode 'unsafe-eval' behaviour is now implemented, so these are ordinary regression tests. Remove the 'PLANNED'/'EXPECTED TO FAIL until impl' banners (which incorrectly told maintainers not to make the source pass) and an unused MagicMock import.
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Thanks for the two follow-ups; both are right, and I am happy with how you have
handled them. Putting the dev-mode logic in get_content_security_policy() is
the correct home for exactly the reason you give, that it runs per request and
so sees the merged config.DEBUG including a config_local override, and
resolving the __webpack_nonce__ point by deleting the assignment rather than
plumbing it through the entry points was the right call too.
A few things remain, mostly carried over from my last review.
🟡 The config comment now contradicts the code
web/config.py:157-164 still tells developers to add 'unsafe-eval' themselves
in config_local.py, but security_headers.py:56 now does that automatically
whenever DEBUG is set. That advice was accurate before f61e8ff and is stale
now; anyone following it will add the incantation and be none the wiser as to
why it changed nothing. Worth replacing with a note that debug mode relaxes the
policy on its own, which also puts the security implication on the record:
turning DEBUG on in a server-mode deployment to chase a bug silently drops
eval protection, and nothing is logged when it happens.
🟢 The extra directives
object-src 'none'; base-uri 'self'; form-action 'self'; still is not in the
policy at web/config.py:165-169. base-uri in particular has no fallback to
default-src, so <base> injection remains entirely unconstrained; the three
cost nothing and sit squarely within the intent of the PR.
🟢 Two lines still missing from the comment
The first is the one I asked for about the eval-capable libraries. Now that I
have chased it properly I can give you the exact mechanism to write down, which
is more useful than my earlier hand-waving: vanilla-jsoneditor defaults
queryLanguages to [jsonQueryLanguage] alone, and JSONQuery composes closures
rather than evaluating source, so the Transform dialog is safe. The only
new Function in the package belongs to the Lodash language, and the others
arrive via jsonpath-plus and ajv's runtime compiler. None of the three is
reachable because JsonEditor.jsx passes neither queryLanguages nor a
validator. That is a fairly load-bearing coincidence to leave undocumented:
register another query language or switch on schema validation later and
'unsafe-eval' becomes necessary again, with the breakage surfacing as a
console error in one dialog rather than anywhere near the change that caused it.
The second is a warning that adding 'nonce-{nonce}' to style-src will
disable 'unsafe-inline' and break MUI's runtime styles. That is the obvious
next step for anyone tightening this further, and the failure would look
mystifying.
🟡 The test gap
Of the three assertions I suggested, the new file covers one, that a policy
without {nonce} is passed through unchanged. The other two are the ones I most
wanted, and they are the two that are missing: that the nonce in the header
matches the nonce on the rendered page's inline tags, and that the rendered page
contains no untagged inline <script>/<style>.
Everything in test_security_headers.py today exercises the helper functions in
isolation, which is useful but leaves the actual regression uncovered. The
failure mode I am worried about is someone adding an untagged inline <script>
to a template in six months; no test in the current file would notice, because
none of them renders a page. A single request against /login asserting both
properties would close that off.
One gotcha when you write it, which I hit myself: regression/runtests.py
pushes a long-lived app context, and since the nonce is cached on flask.g,
which binds to the app context rather than the request, every request inside
that harness sees the same nonce. Your unit tests dodge this neatly by building
their own Flask app, but a rendered-page test going through the harness client
will not, so do not be alarmed by it and do not assert freshness from in there.
None of this changes my earlier conclusion: the mechanism is correct, the
template coverage is complete, and I could not break the app with the committed
policy. These are worth doing before this goes in, but they are all small.
- config.py: rewrite the CSP comment to match the code. Debug mode now auto-adds 'unsafe-eval' for a nonce policy (per-request, so it sees a config_local DEBUG override), with a note on the server-mode implication that turning DEBUG on relaxes the policy unlogged. - config.py: document why 'unsafe-eval' is safe to drop - JsonEditor.jsx passes neither queryLanguages nor a validator, so vanilla-jsoneditor's eval-capable paths (jsonpath-plus, ajv, Lodash language) stay unreachable; enabling either brings the need back. - config.py: warn that adding a nonce to style-src disables 'unsafe-inline' and breaks MUI's runtime styles. - config.py: add object-src 'none' and base-uri 'self' to the policy. - test_security_headers.py: add a rendered-page test asserting the CSP header nonce matches the inline <script>/<style> nonces and that no inline tag is untagged (with the flask.g/app-context caveat noted).
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Thanks @dpage — all addressed:
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Summary
Addresses #7599 — removing
'unsafe-inline'and'unsafe-eval'from the Content-Security-Policy. (Re-opens #10153, which was auto-closed when the source fork was recreated — same branch, same change.)This introduces a per-request CSP nonce so inline scripts run only when they carry the nonce, instead of relying on a blanket
'unsafe-inline'.'unsafe-eval'is dropped from the default policy as well.What changed
security_headers.py— generate a per-request nonce (secrets.token_urlsafe), cached onflask.gso the same value is emitted both in the rendered templates and in theContent-Security-Policyresponse header. A{nonce}placeholder inCONTENT_SECURITY_POLICYis substituted at runtime.__init__.py— exposecsp_nonceto templates.base.html+ tool templates) — tag inline<script>/<style>withnonce="{{ csp_nonce }}", and setwindow.__webpack_nonce__so webpack's dynamically injected assets carry the nonce too.config.py— new default policy:Notes / scope
'unsafe-eval'is not needed by production bundles (verified). Development bundles use webpack'sevaldevtool and do need it, so devs add it inconfig_local.py(documented inconfig.py).style-srckeeps'unsafe-inline'by necessity: MUI/React inject runtime<style>elements and, more importantly, inlinestyle=""attributes that cannot be covered by a nonce or hash. This matches standard practice for MUI/React apps — the meaningful XSS surface (scripts) is what gets locked down.{nonce}is absent from a custom policy, behaviour is unchanged.Testing
Verified against a production build with the strict policy: app loads, all tools (Query Tool, PSQL, ERD, Schema Diff, Debugger) work, and the JSON editor (ajv / jsonpath-plus) runs cleanly with no
'unsafe-eval'— confirming it can be dropped.Summary by CodeRabbit