Enhancement: Run Zammad with a non-superuser PostgreSQL role - #611
Enhancement: Run Zammad with a non-superuser PostgreSQL role#611fliebe92 wants to merge 5 commits into
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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
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Included review availability: Your plan provides up to 8 included reviews per hour; 6 remain after this review. 📝 WalkthroughWalkthroughPostgreSQL configuration now uses separate administrative and Zammad application roles. Initialization creates the application role and database when required, grants database privileges, and rejects identical role credentials. Health checks and automated tests verify that the application role is unprivileged. Documentation covers the configuration and migration procedure for existing installations. Merge Risk: ⚪ Minimal · up to The change runs Zammad with a dedicated non-superuser PostgreSQL role while preserving existing installation behavior; no actionable merge-blocking risk remains based on the supplied evidence. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
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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.)
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| - postgresql-data:/var/lib/postgresql/data | ||
| configs: | ||
| - source: postgresql-initdb | ||
| target: /docker-entrypoint-initdb.d/10-create-zammad-role.sh |
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This will not work with portainer scenarios.
I'm not sure if complicating the docker stack like this is worth it in the end.
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Thanks, you are right and I fixed it in b8561e4 — the external file is gone and the hook is now inlined as configs.content, so docker-compose.yml is self-contained again and can be deployed as-is.
I verified this by copying only docker-compose.yml into an empty directory and starting it there: Compose materialises the script in the container, the $$ escapes are resolved to the container's own variables, and the role and database get created. That covers the Portainer web editor and anyone who just copies the file, not only the repository build method.
This also removes the upgrade burden I had originally written into the release note draft — there is no extra file for existing deployments to pick up anymore.
On "is it worth it in the end": your call, and I am happy to drop it. My case for keeping it, briefly:
- The net cost is now ~25 lines inside
docker-compose.yml, no new file, no new service, no new container. - It removes the last place where our Docker deployment is less hardened than the packaged Linux install, which already creates a plain login role.
- Nothing changes for existing installations - they keep the role layout their volume was created with, and migrating is optional.
The real cost I would like to name honestly: the hook is no longer covered by shellcheck now that it lives in YAML, and the POSTGRESQL_DB_CREATE default change affects people running against an external database server. If either of those tips the balance for you, say so and I will close this in favour of leaving the stack as it is.
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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 draftUpdated after b8561e4: the second breaking change is gone, the compose file is self-contained again. Release 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
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…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.
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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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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.
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 |
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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) and used only for administration.postgresql/initdb.d/10-create-zammad-role.sh, creates the unprivilegedzammadrole and thezammad_productiondatabase it owns. It is mounted through a top-levelconfigs:entry rather than a bind mount, because a missing bind-mount source is silently created as an empty directory, whereas a missing config file makes Compose fail loudly.POSTGRES_DB/POSTGRES_USER/POSTGRES_PASSkeep their meaning for users — they still describe the database and role Zammad connects with.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
The role layout is established while the
postgresql-datavolume is initialised, so existing installations keep the superuser role they were created with. 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, and states that staying on the old layout is not a vulnerability.Tests
check_database_role_is_unprivilegedwas added to the shared test helpers and is asserted in both thedefaultandbackupmodules. It verifies that thezammadrole 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 a real stack:
zammad_productionis owned byzammad,plpgsqlis the only extension.backupmodule passes, i.e.pg_dumpand the restore path — includingDROP SCHEMA public CASCADE; CREATE SCHEMA public;— work without any superuser privilege.SELECT pg_read_file('/etc/passwd')aszammadis denied.zammad) still becomes healthy under this compose file, its data stays reachable, and the initdb hook correctly does not re-run.Follow-up
The environment variable reference on docs.zammad.org lives in
zammad-documentationand needs a separate PR forPOSTGRES_SUPERUSER,POSTGRES_SUPERUSER_PASSand thePOSTGRESQL_DB_CREATEdefault.Summary by CodeRabbit
New Features
Documentation
Bug Fixes