When a user lacks permission, the app should (a) not let them do data entry it
will reject and (b) subtly say who can. General mechanism + the key gates.
Server — compute & expose "who can <verb> here":
- zddc.WhoCan(chain, verb) → Authority{Roles, People}: the acl.permissions
grantees holding the verb across the cascade (roles + their members) plus the
admins (who bypass). New whocan.go + whocan_test.go.
- AccessView gains path_who_can (profilehandler.go), populated only for verbs the
caller LACKS and only when they can read the path (mirrors .zddc readability),
so one cap.at() answers "can I?" and "if not, who?".
- writeForbiddenWho enriches the 403 body with who_can for the missing verb
(errors.go); authorizeAction uses it (fileapi.go) as the safety net for denials
that weren't pre-checked.
Shared — shared/cap.js:
- cap.whoCan(view, verb) + cap.denyHint(view, verb) → {text, title}, role-first
("Only the document controller can create here") with the people in the tooltip.
- handleForbidden appends the hint (from the 403 body, else the cached view), so
every tool that already routes 403s through it (form save, tables save, browse)
now explains who can — for free.
Key gates:
- Browse party-create (the reported bug): pre-check create authority on ssr/ and
the slot BEFORE opening the picker — if the user can do neither, show the hint
instead of the form; if only existing parties are usable, disable "+ New party"
with the who-can hint. The post-hoc 403 catch now names who can too.
- Tables +Add row disabled state shows the who-can hint.
Plus: subtle /_apps/{browse,archive,classifier}.html links in the landing footer.
Tests: Go WhoCan unit test (role/person split, admin bypass, dedupe); cap.spec.js
(denyHint role-first/people/fallback, whoCan, handleForbidden enrichment) — 5
green; Go handler+zddc+policy suites green. (Pre-existing stale browse toolbar
test browse.spec.js:274 unaffected.)
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
74 lines
2.6 KiB
Go
74 lines
2.6 KiB
Go
package handler
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import (
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"encoding/json"
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"net/http"
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"codeberg.org/VARASYS/ZDDC/zddc/internal/policy"
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"codeberg.org/VARASYS/ZDDC/zddc/internal/zddc"
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)
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// writeForbidden emits a 403 JSON response naming the missing verb. Used
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// at every ACL-deny site so the client-side toast can render a specific
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// "you need <verb> here" message and offer elevation when the path-scoped
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// /.profile/access?path= reports a would_elevate_grant covering that verb.
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//
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// Body shape:
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//
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// {"error": "Forbidden", "missing_verb": "w"}
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//
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// Existing clients that read the body as text see the JSON string instead
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// of "Forbidden\n" — both are diagnostic-only display strings, no client
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// in this repo parses the previous plain-text body for content. Used in
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// place of `http.Error(w, "Forbidden", http.StatusForbidden)` exclusively
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// for ACL-deny cases. Other 403 conditions (no authenticated principal,
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// existence-leak guards, etc.) keep the plain-text variant since
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// "missing_verb" doesn't apply to them.
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func writeForbidden(w http.ResponseWriter, action string) {
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verb := verbForAction(action)
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body, _ := json.Marshal(map[string]string{
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"error": "Forbidden",
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"missing_verb": verb,
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})
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w.Header().Set("Content-Type", "application/json; charset=utf-8")
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w.WriteHeader(http.StatusForbidden)
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_, _ = w.Write(body)
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}
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// writeForbiddenWho is writeForbidden enriched with a "who_can" Authority for
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// the missing verb, computed from the deny site's policy chain. Lets the toast
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// tell the user who to ask even when the action wasn't pre-checked (a race, or
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// a path the client didn't gate). The pre-check path (AccessView.PathWhoCan) is
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// the primary surface; this is the safety net.
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func writeForbiddenWho(w http.ResponseWriter, action string, chain zddc.PolicyChain) {
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verb := verbForAction(action)
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body := map[string]any{"error": "Forbidden", "missing_verb": verb}
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if vs, ok := zddc.ParseVerbSet(verb); ok {
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if a := zddc.WhoCan(chain, vs); !a.Empty() {
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body["who_can"] = a
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}
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}
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raw, _ := json.Marshal(body)
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w.Header().Set("Content-Type", "application/json; charset=utf-8")
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w.WriteHeader(http.StatusForbidden)
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_, _ = w.Write(raw)
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}
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// verbForAction maps a policy.Action constant to its single-character
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// verb. Mirrors policy.actionVerb but emits the wire-format letter
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// rather than the bitmask, so the JSON body carries "r"/"w"/"c"/"d"/"a"
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// — the same alphabet the listing's `verbs` field uses.
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func verbForAction(action string) string {
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switch action {
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case policy.ActionWrite:
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return "w"
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case policy.ActionCreate:
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return "c"
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case policy.ActionDelete:
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return "d"
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case policy.ActionAdmin:
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return "a"
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default:
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return "r"
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}
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}
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