fix(mutation): apply the auth context to table mutations (closes #73)#75
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Table mutations (POST/PATCH/PUT/DELETE on a relation) ran with no auth
context at all, while reads and RPC already wrapped their DB work in
Bier.Auth.with_context/4 (SET LOCAL ROLE + request.* GUCs + the
db-pre-request hook). This meant a JWT's role claim, db-anon-role,
db-pre-request, and role-based grants/RLS had no effect on writes — an
anonymous request could write as the connecting (often superuser) role.
Bier.Mutation.run/4 now threads conn.assigns[:bier_auth] into the
mutation transaction via Bier.Auth.with_context/4, mirroring the read
and RPC paths, and maps a resulting Postgrex.Error through
Bier.Auth.map_error/2 so an anonymous 42501 surfaces as 401 (WWW-Authenticate:
Bearer) instead of 403 or a silent success.
Bier.Mutation.execute/4 threads the rollback reason through
Postgrex.rollback/2 as the full {:error, _} tuple rather than the bare
reason (unlike the read path), so a write-query failure is double-wrapped
by the time it reaches Postgrex.transaction/2's return; a setup-phase
failure (role switch / db-pre-request) is not. mutation.ex's new
map_write_error/2 matches both shapes rather than touching that existing
convention, keeping the change scoped to the auth gap.
Added test/bier/mutation_auth_test.exs (TDD, run RED against the
pre-fix code) covering both angles against a dedicated
auth-configured instance: an authenticated author's JWT id claim must
reach a DEFAULT-derived column (GUC-based proof, with two different
claims to rule out a hardcoded value), and an anonymous insert into a
table only postgrest_test_author may write must now be denied (401)
instead of silently succeeding as the superuser (privilege-based
proof — the actual security hole).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Closes #73.
What & why
Table mutations (
POST/PATCH/PUT/DELETE) ran with no per-request auth context — noSET LOCAL ROLE, norequest.*GUCs, nodb-pre-request. Reads (query_executor.ex) and RPC (rpc.ex) already wrap their DB work inBier.Auth.with_context/4, butmutation.exdid not, so the JWTrole,db-anon-role,db-pre-request, and role-based grants/RLS had no effect on writes. In a real deployment (Bier connecting as a non-superuserauthenticator), an anonymous write ran as the connecting role instead of the anon role — a security gap.Fix
lib/bier/mutation.exrun/4now threads the context (conn.assigns[:bier_auth]) into the mutation transaction and wrapsexecute/4inBier.Auth.with_context/4, mapping a Postgres error throughBier.Auth.map_error/2— exactly mirroring the read path. When no auth is configured (bier_authabsent), the path is an exact no-op, so behavior is unchanged.WWW-Authenticate: BearerSET LOCAL ROLE+request.jwt.claimsVerification
mix test: 825 passed, 0 failures (no auth-schema table-mutation conformance case existed, so no regression).test/bier/mutation_auth_test.exs: anonPOSTto a table the anon role can't write → 401; author-JWTPOST→ 201, and acurrent_setting('request.jwt.claims')-defaulted column reflects the token'sidclaim (two distinct claim values).mix format/credo --strict/docs --warnings-as-errorsclean.Follow-ups (non-blocking)
execute/4's double-wrapped rollback error tuples (pre-existing convention) somap_write_error/2needn't match two shapes.🤖 Generated with Claude Code