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 Kotlin client supports all three through its constructor parameters. 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.

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Bearer token mode

Start the daemon with a token:

mongreldb-server --auth-token s3cret-token

Connect by passing the token as the token constructor argument. The token is sent as Authorization: Bearer ... on every request.

val db = MongrelDB(
    url = "http://127.0.0.1:8453",
    token = "s3cret-token",
)

if (!db.health()) {
    // A bad/missing token surfaces as AuthException on the first call;
    // health() swallows it and returns false.
    error("daemon not reachable (bad token?)")
}

A missing or wrong token surfaces as AuthException (HTTP 401/403) on any call. health() catches exceptions and returns false, so it is a safe probe; other methods throw.

Where the token comes from

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

val token = System.getenv("MONGRELDB_TOKEN") ?: error("MONGRELDB_TOKEN not set")
val db = MongrelDB(MongrelDB.DEFAULT_BASE_URL, token = token)

Basic auth mode

Start the daemon with a users file or inline users:

mongreldb-server --auth-users

Connect with username and password:

val db = MongrelDB(
    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 a token and Basic credentials, the token wins and Basic credentials are ignored. This lets you layer an override without branching:

val db = MongrelDB(
    url = url,
    token = "overrides-everything", // token wins
    username = "fallback",          // ignored
    password = "user",              // ignored
)

Timeouts

The default connect and read timeouts are both 30 seconds. Override them with the connectTimeoutMillis and readTimeoutMillis constructor arguments:

val db = MongrelDB(
    url = "http://127.0.0.1:8453",
    token = token,
    connectTimeoutMillis = 10_000,
    readTimeoutMillis = 60_000,
)

Because the client uses java.net.HttpURLConnection, there is no connection pooling to configure: each request opens and closes its own connection. For a pooled transport, run the client behind a local HTTP proxy or adopt the JVM's keep.alive defaults (on by default).

Verifying what gets sent

The auth header is applied in MongrelDB.applyAuth, called from every request. For debugging, point the client at a local echo server or watch the daemon logs. A quick integration test pattern is in src/test/kotlin/.../MongrelDBLiveTest.kt: it spins up an in-process com.sun.net.httpserver.HttpServer that captures the Authorization header and asserts the client sent Bearer <token>.

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.

Create a user

db.sql("CREATE USER alice WITH PASSWORD 'hunter2'")

Alter a user

Change a password:

db.sql("ALTER USER alice WITH PASSWORD 'new-password'")

Grant the admin role:

db.sql("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

db.sql("DROP USER alice")

Roles and grants

db.sql("CREATE ROLE analyst")
db.sql("GRANT SELECT ON orders TO analyst")
db.sql("GRANT analyst TO alice")
db.sql("REVOKE SELECT ON orders FROM analyst")
db.sql("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 typed catches. A 401/403 raises AuthException; a 404 raises NotFoundException. Always catch the specific subclass rather than string-matching message.

Forgetting to set auth in production. A client built with MongrelDB(url) sends no credentials. Against an auth-enabled daemon, every call throws AuthException. Centralize client construction so the auth credentials are never accidentally dropped.

Sharing one client across threads is fine; sharing credentials across users is not. A MongrelDB instance is thread-safe, 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 - AuthException and the rest of the exception hierarchy
• quickstart.md - the full end-to-end walkthrough