Enhancement: Run Zammad with a non-superuser PostgreSQL role - #611
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📝 WalkthroughWalkthroughPostgreSQL configuration now uses separate administrative and Zammad application roles. Initialization creates the application role and database and rejects invalid role or database combinations. Health checks and automated tests verify that the application role is unprivileged. Documentation covers configuration, deployment requirements, privilege handling, and migration procedures. Merge Risk: 🟠 High · up to A failed initial configuration can restart successfully with Zammad using the PostgreSQL superuser, defeating the intended privilege separation. This should be prevented on every startup before merge. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 4 files. (1 skipped: 1 unsupported.) Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out. Comment |
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Inline comments:
In @.github/tests/include/functions.sh:
- Around line 28-35: Update both psql checks in the relevant test function to
use the configured POSTGRES_USER value for --username instead of the hardcoded
postgres role, and bind ZAMMAD_DB_USER as a psql variable so both rolname and
pg_has_role queries target the configured application role.
In `@postgresql/initdb.d/10-create-zammad-role.sh`:
- Line 20: Update the validation near ZAMMAD_DB_USER in the bootstrap script to
reject initialization when ZAMMAD_DB_USER equals POSTGRES_USER, before role
creation or connection setup proceeds; retain the existing required-variable
validation and emit a clear failure for the conflicting values.
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.env.dist.github/tests/backup.sh.github/tests/default.sh.github/tests/include/functions.shREADME.mddocker-compose.ymlpostgresql/initdb.d/10-create-zammad-role.sh
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Release note draftRelease Drafter picks the PR title up automatically. Below are the sub-bullets to nest under it in the drafted release, in the same style as v16.0.0 and v15.0.0. Because of the
Related: zammad/coordination-technical-debt#854 · docs: zammad/zammad-documentation#900 |
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Inline comments:
In `@docker-compose.yml`:
- Around line 195-199: Update the zammad-postgresql healthcheck to validate an
actual Zammad database connection using TCP psql with --no-password,
ZAMMAD_DB_USER, ZAMMAD_DB_PASS, ZAMMAD_DB, and SELECT 1; replace the pg_isready
check while preserving the existing superuser comparison.
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Self-review notesTwo things came out of reviewing my own diff. 1. The migration path in the README was never actually executed — now it has been. Everything I had tested so far restored a dump into the same volume. The documented migration restores a dump taken by the old superuser
Result: restore ran ( While writing that test I noticed the steps staged the restore folder while the stack was still running, which leaves a window where any restarting Zammad container blocks in 2. Verified two assumptions in the test helper that I had only reasoned about. The postgres entrypoint does I also confirmed the assertion actually discriminates rather than passing vacuously:
And the full helper passes against a stack with entirely custom names ( Not changed: the |
The superuser password follows POSTGRES_PASS unless it is set explicitly, so that hardening that one variable does not leave a superuser behind on the default password. Also document that the superuser name must differ from POSTGRES_USER, since the stack refuses to start otherwise. See zammad/zammad-docker-compose#611
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@fliebe92 could you refresh the PR description and the release-note draft after 7fc85ce? A few things went stale:
The |
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Inline comments:
In `@docker-compose.yml`:
- Line 284: Update the database initialization hook around CREATE DATABASE and
CREATE ROLE to reject POSTGRES_DB values postgres, template0, and template1
before creating the Zammad role, preventing partial initialization; preserve
normal creation for other database names.
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Both refreshed, thanks for catching them. The description no longer describes the hook as a mounted file, and the healthcheck bullet now says what it actually does. It also documents the new Compose requirement and lists the verification I ran, including the migration executed end to end. On the release note: the Thanks for independently confirming the |
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Inline comments:
In `@docker-compose.yml`:
- Around line 194-196: Update the PostgreSQL healthcheck to validate on every
startup that POSTGRES_USER, POSTGRES_SUPERUSER, and POSTGRES_DB are distinct,
rather than relying only on the initdb hook guard. Ensure the healthcheck fails
for the collision-and-restart case while preserving supported migrated legacy
volumes, and add separate coverage for both scenarios.
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The postgres image unconditionally provisions POSTGRES_USER as a database superuser, so the stack connected to PostgreSQL with far more privilege than Zammad needs. Zammad only owns its own database and uses the built-in plpgsql extension, and the packaged Linux install already creates a plain login role. The bootstrap superuser is now kept separate as "postgres" and used only for administration, while an initdb hook creates the unprivileged "zammad" role along with the database it owns. Since that role deliberately has no CREATEDB attribute and the database is created up front, POSTGRESQL_DB_CREATE now defaults to false; installations using an external PostgreSQL server can re-enable it. The role layout is established when the database volume is initialised, so existing installations keep the one they were created with. PostgreSQL does not allow the bootstrap role to be demoted, so the README documents an optional backup and restore migration for them. See zammad/coordination-technical-debt#854
…ration Referencing the initdb hook as an external file broke deployments that only consume docker-compose.yml, such as Portainer stacks. The hook is inlined as config content instead, so the compose file can be deployed as-is again. The bootstrap role is a superuser, so Zammad must never reuse it. Rejecting that only in the initdb hook is not enough, because the restart policy brings the container back up with the role left uncreated, leaving Zammad to connect as the superuser after all. The healthcheck now rejects it as well, which keeps the stack down until the configuration is fixed. The role privilege test no longer assumes the default role names and uses the ones the database container is configured with.
pg_isready reports success for an unknown role or database, and accepts the socket-only server that runs while the data directory is still initialising. Dependent services wait for this healthcheck, so it has to prove more than that: the role and the database the initdb hook provisions must be usable, otherwise a failed hook would let the whole stack start against a database Zammad cannot connect to.
Anyone who had hardened POSTGRES_PASS would otherwise have gained a superuser on the default password, since POSTGRES_SUPERUSER_PASS fell back to 'zammad' independently. The role is only reachable from inside the stack network, but it is a privilege the installation did not have before, so the superuser password now follows POSTGRES_PASS unless it is set explicitly. Also document that POSTGRES_SUPERUSER must differ from POSTGRES_USER.
Comparing the configured role names in the healthcheck mixed configuration validation into it, and it was redundant: when the initdb hook rejects a bootstrap role collision it aborts before creating the database, so the connection check already fails and the stack stays down, with the reason in the database container log. Dropping it also removes a breaking change. An existing installation whose .env sets POSTGRES_USER=postgres collided with the new superuser default and would have stopped starting, although nothing about it is wrong. It now stays healthy and keeps working.
Without it the check only succeeded because initdb writes a trust rule for the loopback address ahead of the scram rule the image appends. Where host connections do require authentication, for example with POSTGRES_INITDB_ARGS=--auth-host=scram-sha-256, it failed with 'fe_sendauth: no password supplied' and the stack never came up, even though the role and the database had been provisioned correctly. Supplying it also means the check validates the credentials Zammad itself uses, wherever the loopback address is not trusted.
The conditional role and database creation could not trigger: the hook only runs against a freshly initialised cluster, where the sole pre-existing login role is the bootstrap role, which the collision check already rejects. It also implied an idempotency the hook does not have, since it never runs again on an existing volume. Dropping it removes the need for format() and \gexec, because psql can quote the identifiers and the password directly. Granting privileges on the database was a no-op, as the role owns it and therefore already holds CREATE, CONNECT and TEMPORARY on it. The README now states the minimum Docker Compose version, which the inlined config content requires, and that Docker Swarm is not supported, pointing at the Helm chart instead. The migration steps are marked as relevant only for installations predating this change. Finally, .env.dist no longer presents 'zammad' as the literal default for the superuser password, which someone could have uncommented as harmless while having hardened POSTGRES_PASS.
Naming a system database in POSTGRES_DB created the role and then failed, because that database already exists. The volume was left initialised, so the hook never ran again, while the healthcheck happily connected to the existing database - leaving Zammad pointed at a database owned by the bootstrap role. It is now rejected before anything is created. Both rejections also explain how to recover. initdb has already run when the hook executes, so correcting the configuration and starting again does not help, and the operator would otherwise only see a role or database reported missing on the next boot.
Compose only strips a trailing comment from a non-empty value in .env, so uncommenting the line set the superuser password to the comment text itself rather than leaving it empty for the fallback to act on. The hint now sits on its own line above it.
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#900) The Docker Compose stack now connects to PostgreSQL with an unprivileged login role and keeps a separate administrative superuser. Documents the new POSTGRES_SUPERUSER and POSTGRES_SUPERUSER_PASS variables, including that the superuser password follows POSTGRES_PASS and that its name must differ from POSTGRES_USER, clarifies POSTGRES_USER, and corrects the POSTGRESQL_DB_CREATE default, which is false in that stack because the Zammad role may not create databases. See zammad/zammad-docker-compose#611
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Refs zammad/coordination-technical-debt#854
What
The
postgresimage unconditionally provisionsPOSTGRES_USERas a database superuser, so the stack has been connecting to PostgreSQL with far more privilege than Zammad needs. Zammad only owns its own database and uses the built-inpg_catalog.plpgsqlextension — the packaged Linux install already creates a plain login role viaCREATE USER+GRANT ALL PRIVILEGES ON DATABASE, so the Docker stack was the outlier.This is defense in depth, not a fix for an exploitable issue: every capability a superuser role unlocks presupposes valid database credentials and network access to the database in the first place.
How
postgres(configurable viaPOSTGRES_SUPERUSER/POSTGRES_SUPERUSER_PASS, whose password followsPOSTGRES_PASSunless set explicitly) and used only for administration.docker-compose.ymlasconfigs.content, creates the unprivilegedzammadrole and thezammad_productiondatabase it owns. It is inlined rather than referenced as a file so thatdocker-compose.ymlstays deployable on its own, for example by pasting it into Portainer.POSTGRES_DB/POSTGRES_USER/POSTGRES_PASSkeep their meaning for users — they still describe the database and role Zammad connects with.SELECT 1, rather than usingpg_isready, which reports success for an unknown role or database and also accepts the socket-only server that runs during initialisation. Dependent services wait on it, so it has to prove the provisioned role and database are usable.configs.contentwas introduced there. Noted in the README along with the fact that Docker Swarm is not supported —docker stack deployrejects thedepends_onconditions this stack relies on, onmasteras much as here.Behaviour change:
POSTGRESQL_DB_CREATEnow defaults tofalsezammad-initrunsrake db:create, and a role withoutCREATEDBcannot do that — PostgreSQL performs the privilege check before the "database already exists" check, so it fails outright rather than passing through Rails' already-exists handling. Since the bundled server now creates the database up front,db:createis unnecessary. Anyone pointing Zammad at an external PostgreSQL server and relying on auto-creation needs to setPOSTGRESQL_DB_CREATE=trueand give their role theCREATEDBattribute.Existing installations
No action needed. The role layout is established while the
postgresql-datavolume is initialised, so existing installations keep the superuser role they were created with, and this branch leaves them healthy with their data intact. PostgreSQL refuses to demote the bootstrap role (The bootstrap superuser must have the SUPERUSER attribute) andREASSIGN OWNEDcannot move its objects, so there is no clean in-place migration. The README documents an optional backup and restore into a fresh volume instead, clearly marked as migration-only.Tests
check_database_role_is_unprivilegedwas added to the shared test helpers and is asserted in both thedefaultandbackupmodules. It verifies that Zammad's role — looked up from the container's own configuration rather than hardcoded — holds none ofSUPERUSER,CREATEDB,CREATEROLE,REPLICATION,BYPASSRLS, and is not a member ofpg_read_server_files,pg_write_server_filesorpg_execute_server_program.Verified locally against real stacks:
zammad_productionis owned byzammad,plpgsqlis the only extension, andSELECT pg_read_file('/etc/passwd')aszammadis denied.backupmodule passes, i.e.pg_dumpand the restore path — includingDROP SCHEMA public CASCADE; CREATE SCHEMA public;— work without any superuser privilege.master, seeded a canary, followed the README steps, and the restored instance keeps its data while ending up withzammad rolsuper=falseowning its database..envsetsPOSTGRES_USER=postgres.$and backslashes.POSTGRES_INITDB_ARGS=--auth-host=scram-sha-256, where the loopback address is not trusted, the healthcheck still passes and genuinely validates the credentials.docker-compose.ymlworks, which is what Portainer's web editor and plain copy-paste amount to.Follow-up
The environment variable reference on docs.zammad.org is updated in zammad/zammad-documentation#900.
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