Authentication & Authorization

July 8, 2026 ยท View on GitHub

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 Go client supports all three through NewClient 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 WithToken. The token is sent as Authorization: Bearer ... on every request.

db := mdb.NewClient("http://127.0.0.1:8453",
	mdb.WithToken("s3cret-token"),
)

ok, err := db.Health(ctx)
if err != nil {
	if errors.Is(err, mdb.ErrAuth) {
		log.Fatal("bad or missing token")
	}
	log.Fatal(err)
}
fmt.Println("healthy:", ok)

A missing or wrong token surfaces as an error wrapping mdb.ErrAuth (HTTP 401/403).

Where the token comes from

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

token := os.Getenv("MONGRELDB_TOKEN")
if token == "" {
	log.Fatal("MONGRELDB_TOKEN not set")
}
db := mdb.NewClient(mdb.DefaultBaseURL, mdb.WithToken(token))

Basic auth mode

Start the daemon with a users file or inline users:

mongreldb-server --auth-users

Connect with WithBasicAuth:

db := mdb.NewClient("http://127.0.0.1:8453",
	mdb.WithBasicAuth("admin", "s3cret"),
)

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

Token takes precedence

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

db := mdb.NewClient(url,
	mdb.WithBasicAuth("fallback", "user"),
	mdb.WithToken("overrides-everything"),
)

Custom transport and timeouts

WithHTTPClient installs a custom *http.Client (e.g. with a custom transport for mTLS, proxies, or connection pooling). WithTimeout sets the per-request timeout.

db := mdb.NewClient(url,
	mdb.WithToken(token),
	mdb.WithTimeout(60*time.Second),
)

// Or a fully custom client:
db := mdb.NewClient(url,
	mdb.WithToken(token),
	mdb.WithHTTPClient(&http.Client{
		Timeout:   60 * time.Second,
		Transport: &http.Transport{ /* TLS, proxy, pooling, ... */ },
	}),
)

Verifying what gets sent

The auth header is applied in Client.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 using httptest:

srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
	fmt.Println(r.Header.Get("Authorization")) // inspect the header
	w.WriteHeader(200)
}))
defer srv.Close()

db := mdb.NewClient(srv.URL, mdb.WithToken("abc"))
_, _ = db.Health(context.Background())
// prints: Bearer abc

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 Client.SQL.

Create a user

db.SQL(ctx, "CREATE USER alice WITH PASSWORD 'hunter2'")

Alter a user

Change a password:

db.SQL(ctx, "ALTER USER alice WITH PASSWORD 'new-password'")

Grant the admin role:

db.SQL(ctx, "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(ctx, "DROP USER alice")

Roles and grants

db.SQL(ctx, "CREATE ROLE analyst")
db.SQL(ctx, "GRANT SELECT ON orders TO analyst")
db.SQL(ctx, "GRANT analyst TO alice")
db.SQL(ctx, "REVOKE SELECT ON orders FROM analyst")
db.SQL(ctx, "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 errors.Is. A 401/403 maps to mdb.ErrAuth; a 404 maps to mdb.ErrNotFound. Always discriminate with errors.Is rather than string-matching err.Error().

Forgetting to set auth in production. A client built with NewClient(url) and no options sends no credentials. Against an auth-enabled daemon, every call fails with ErrAuth. Centralize client construction so the auth option is never accidentally dropped.

Sharing one client across goroutines is fine; sharing credentials across users is not. A *Client is 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