Fix: form-action CSP blocked atproto login form submission (v0.4.2)#107
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The handle-entry form sets a strict CSP. The `form-action 'self'` directive (added for defense-in-depth) silently broke login: submitting the form hits our endpoint, which immediately 302-redirects to the user's own authorization server (any PDS, cross-origin). `form-action` is enforced across the entire redirect chain, so `'self'` blocks the submission and the browser does nothing — exactly the "form doesn't send me there" symptom, while navigating to the auth URL directly worked (no form-action involved). Remove the `form-action` directive entirely — it is fundamentally incompatible with a login form that must redirect to per-user auth servers. The rest of the hardening (default-src 'none', no scripts, frame-ancestors, nosniff, no-store, style-src 'self') stays. Add a regression test asserting the form CSP never carries form-action. Reproduced and verified the fix by driving the form in headless Chrome. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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| Status | Name | Latest Commit | Updated (UTC) |
|---|---|---|---|
| ✅ Deployment successful! View logs |
startup-api | 1ef82e6 | Jun 29 2026, 02:36 AM |
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Regression in 0.4.1 — atproto login form does nothing
The hardened CSP added to the handle-entry form in #106 included
form-action 'self', which silently breaks login.Root cause
Submitting the handle form hits our
/users/auth/atproto?handle=…endpoint, which immediately 302-redirects to the user's own authorization server (any PDS —bsky.socialor self-hosted, cross-origin).form-actionis enforced across the entire redirect chain, so'self'rejects the submission and the browser does nothing.This is exactly the reported symptom: navigating to the auth URL directly works (no form involved), but the form "doesn't send you there."
Reproduced in headless Chrome — the console shows:
Fix
Remove the
form-actiondirective from the handle form. It's fundamentally incompatible with a login form that must redirect to per-user auth servers. All other hardening stays:default-src 'none'(no scripts),frame-ancestors 'none',style-src 'self',nosniff,no-store. Added a regression test asserting the form CSP never carriesform-action.Verified
wrangler dev: submission now navigates to the auth endpoint with the handle and no CSP violation (localhost returns 400 only because bsky can't fetch a127.0.0.1client-metadata URL for PAR; on the live HTTPS demo it 302s to bsky).tsc+eslintclean; full suite 129/129.Bumps patch version to 0.4.2 (0.4.1 is live-broken).
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