Authentication & Authorization

A mongreldb-server daemon runs in one of three modes:

1. Open (default) - no auth required.
2. Bearer token (--auth-token <TOKEN>) - every request must carry an Authorization: Bearer <TOKEN> header.
3. HTTP Basic (--auth-users) - every request must carry an Authorization: Basic <base64(user:pass)> header.

The Erlang client supports all three through mongreldb:connect/1 options. This guide shows each mode, how to inspect what was sent, and how to manage users and roles via SQL when the server is in Basic mode.

---

Bearer token mode

Start the daemon with a token:

mongreldb-server --auth-token s3cret-token

Connect with token. The token is sent as Authorization: Bearer ... on every request.

{ok, Db} = mongreldb:connect(#{url => <<"http://127.0.0.1:8453">>,
                               token => <<"s3cret-token">>}),

case (catch mongreldb:health(Db)) of
    true -> io:format("healthy~n", []);
    {mongreldb_error, mongreldb_auth_error, _} -> erlang:error(bad_or_missing_token);
    false -> erlang:error(daemon_unreachable)
end.

A missing or wrong token surfaces as mongreldb_auth_error (HTTP 401/403).

Where the token comes from

Hard-coding secrets in source is bad practice. Read it from the environment:

Token = case os:getenv("MONGRELDB_TOKEN") of
            false -> erlang:error(missing_mongreldb_token);
            "" -> erlang:error(missing_mongreldb_token);
            V -> list_to_binary(V)
        end,
{ok, Db} = mongreldb:connect(#{token => Token}).

Basic auth mode

Start the daemon with a users file or inline users:

mongreldb-server --auth-users

Connect with username / password:

{ok, Db} = mongreldb:connect(#{url => <<"http://127.0.0.1:8453">>,
                               username => <<"admin">>,
                               password => <<"s3cret">>}).

The client base64-encodes username:password and sets Authorization: Basic ... on every request.

Token takes precedence

If you supply both, token wins and Basic credentials are ignored. This lets you layer an override without branching:

{ok, Db} = mongreldb:connect(#{url => Url,
                               username => <<"fallback">>,
                               password => <<"user">>,
                               token => <<"overrides-everything">>}).

Timeouts

The client takes timeout (per-request) and connect_timeout, both in milliseconds.

{ok, Db} = mongreldb:connect(#{url => Url,
                               token => Token,
                               timeout => 10000,
                               connect_timeout => 30000}).

User and role management via SQL

When the daemon is in Basic auth mode, users and roles live in the catalog and are managed with SQL. Run these statements through mongreldb:sql/2.

Create a user

{ok, _} = mongreldb:sql(Db, <<"CREATE USER alice WITH PASSWORD 'hunter2'">>).

Alter a user

Change a password:

{ok, _} = mongreldb:sql(Db, <<"ALTER USER alice WITH PASSWORD 'new-password'">>).

Grant the admin role:

{ok, _} = mongreldb:sql(Db, <<"ALTER USER alice ADMIN">>).

ALTER USER ... ADMIN is how you promote a user to full administrative privileges (table creation/drop, compaction, user management). Use it sparingly.

Drop a user

{ok, _} = mongreldb:sql(Db, <<"DROP USER alice">>).

Roles and grants

{ok, _} = mongreldb:sql(Db, <<"CREATE ROLE analyst">>),
{ok, _} = mongreldb:sql(Db, <<"GRANT SELECT ON orders TO analyst">>),
{ok, _} = mongreldb:sql(Db, <<"GRANT analyst TO alice">>),
{ok, _} = mongreldb:sql(Db, <<"REVOKE SELECT ON orders FROM analyst">>),
{ok, _} = mongreldb:sql(Db, <<"DROP ROLE analyst">>).

Exact grant syntax mirrors the server's SQL flavor; consult the server's SQL reference for the full GRANT/REVOKE grammar available in your build.

Common pitfalls

Auth errors look like other errors without a specific catch clause. A 401/403 raises mongreldb_auth_error; a 404 raises mongreldb_not_found_error. Always discriminate by class rather than string-matching the message.

Forgetting to set auth in production. A client built with mongreldb:connect/0 and no credentials sends no credentials. Against an auth-enabled daemon, every call raises mongreldb_auth_error. Centralize client construction so the auth option is never accidentally dropped.

Sharing one client across processes is fine; sharing credentials across users is not. A client is a plain map and safe for concurrent use, but it carries one identity. If you serve multiple authenticated users, build a client per user (or per request) with that user's token.

Token in version control. Put secrets in the environment, a secret manager, or a file outside the repo. Never commit a real token.

Next steps

• errors.md - mongreldb_auth_error and the rest of the error hierarchy
• quickstart.md - the full end-to-end walkthrough