M1/#292: auth.Bootstrap for empty-users-table first-run admin

internal/auth/bootstrap.go

@@ -0,0 +1,85 @@
+package auth
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
+	"log/slog"
+	"os"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+	"golang.org/x/crypto/bcrypt"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/config"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+)
+
+// Bootstrap creates the initial admin user when the users table is empty AND
+// the config supplies a bootstrap username. A blank password means "generate a
+// random one and print it once on stderr" — suitable for first-run setups
+// where the operator is watching the logs.
+func Bootstrap(ctx context.Context, pool *pgxpool.Pool, cfg config.AdminBootstrapConfig, logger *slog.Logger) error {
+	if cfg.Username == "" {
+		return nil
+	}
+
+	q := dbq.New(pool)
+	count, err := q.CountUsers(ctx)
+	if err != nil {
+		return fmt.Errorf("auth: count users: %w", err)
+	}
+	if count > 0 {
+		return nil
+	}
+
+	password := cfg.Password
+	passwordGenerated := false
+	if password == "" {
+		p, err := randomToken(18)
+		if err != nil {
+			return fmt.Errorf("auth: generate password: %w", err)
+		}
+		password = p
+		passwordGenerated = true
+	}
+
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return fmt.Errorf("auth: hash password: %w", err)
+	}
+
+	apiToken, err := randomToken(32)
+	if err != nil {
+		return fmt.Errorf("auth: generate api token: %w", err)
+	}
+
+	user, err := q.CreateUser(ctx, dbq.CreateUserParams{
+		Username:     cfg.Username,
+		PasswordHash: string(hash),
+		ApiToken:     apiToken,
+		IsAdmin:      true,
+	})
+	if err != nil {
+		return fmt.Errorf("auth: insert admin: %w", err)
+	}
+
+	logger.Info("admin bootstrapped", "username", cfg.Username, "user_id", user.ID.String())
+	if passwordGenerated {
+		fmt.Fprintf(os.Stderr, "\n--- minstrel admin bootstrap (shown once) ---\nusername:  %s\npassword:  %s\napi_token: %s\n---\n\n",
+			cfg.Username, password, apiToken)
+	} else {
+		fmt.Fprintf(os.Stderr, "\n--- minstrel admin api token (shown once) ---\nusername:  %s\napi_token: %s\n---\n\n",
+			cfg.Username, apiToken)
+	}
+	return nil
+}
+
+// randomToken returns a URL-safe base64 string backed by n random bytes.
+func randomToken(n int) (string, error) {
+	b := make([]byte, n)
+	if _, err := rand.Read(b); err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(b), nil
+}