navidrome/plugins/host_subsonicapi.go

package plugins

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"net/http/httptest"
	"net/url"
	"path"
	"strings"

	"github.com/navidrome/navidrome/log"
	"github.com/navidrome/navidrome/model"
	"github.com/navidrome/navidrome/model/request"
	"github.com/navidrome/navidrome/plugins/host/subsonicapi"
	"github.com/navidrome/navidrome/plugins/schema"
	"github.com/navidrome/navidrome/server/subsonic"
)

// SubsonicAPIService is the interface for the Subsonic API service
//
// Authentication: The plugin must provide valid authentication parameters in the URL:
//   - Required: `u` (username) - The service validates this parameter is present
//   - Example: `"/rest/ping?u=admin"`
//
// URL Format: Only the path and query parameters from the URL are used - host, protocol, and method are ignored
//
// Automatic Parameters: The service automatically adds:
//   - `c`: Plugin name (client identifier)
//   - `v`: Subsonic API version (1.16.1)
//   - `f`: Response format (json)
//
// See example usage in the `plugins/examples/subsonicapi-demo` plugin
type subsonicAPIServiceImpl struct {
	pluginID    string
	router      SubsonicRouter
	ds          model.DataStore
	permissions *subsonicAPIPermissions
}

func newSubsonicAPIService(pluginID string, router *SubsonicRouter, ds model.DataStore, permissions *schema.PluginManifestPermissionsSubsonicapi) subsonicapi.SubsonicAPIService {
	return &subsonicAPIServiceImpl{
		pluginID:    pluginID,
		router:      *router,
		ds:          ds,
		permissions: parseSubsonicAPIPermissions(permissions),
	}
}

func (s *subsonicAPIServiceImpl) Call(ctx context.Context, req *subsonicapi.CallRequest) (*subsonicapi.CallResponse, error) {
	if s.router == nil {
		return &subsonicapi.CallResponse{
			Error: "SubsonicAPI router not available",
		}, nil
	}

	// Parse the input URL
	parsedURL, err := url.Parse(req.Url)
	if err != nil {
		return &subsonicapi.CallResponse{
			Error: fmt.Sprintf("invalid URL format: %v", err),
		}, nil
	}

	// Extract query parameters
	query := parsedURL.Query()

	// Validate that 'u' (username) parameter is present
	username := query.Get("u")
	if username == "" {
		return &subsonicapi.CallResponse{
			Error: "missing required parameter 'u' (username)",
		}, nil
	}

	if err := s.checkPermissions(ctx, username); err != nil {
		log.Warn(ctx, "SubsonicAPI call blocked by permissions", "plugin", s.pluginID, "user", username, err)
		return &subsonicapi.CallResponse{Error: err.Error()}, nil
	}

	// Add required Subsonic API parameters
	query.Set("c", s.pluginID)       // Client name (plugin ID)
	query.Set("f", "json")           // Response format
	query.Set("v", subsonic.Version) // API version

	// Extract the endpoint from the path
	endpoint := path.Base(parsedURL.Path)

	// Build the final URL with processed path and modified query parameters
	finalURL := &url.URL{
		Path:     "/" + endpoint,
		RawQuery: query.Encode(),
	}

	// Create HTTP request with internal authentication
	httpReq, err := http.NewRequestWithContext(ctx, "GET", finalURL.String(), nil)
	if err != nil {
		return &subsonicapi.CallResponse{
			Error: fmt.Sprintf("failed to create HTTP request: %v", err),
		}, nil
	}

	// Set internal authentication context using the username from the 'u' parameter
	authCtx := request.WithInternalAuth(httpReq.Context(), username)
	httpReq = httpReq.WithContext(authCtx)

	// Use ResponseRecorder to capture the response
	recorder := httptest.NewRecorder()

	// Call the subsonic router
	s.router.ServeHTTP(recorder, httpReq)

	// Return the response body as JSON
	return &subsonicapi.CallResponse{
		Json: recorder.Body.String(),
	}, nil
}

func (s *subsonicAPIServiceImpl) checkPermissions(ctx context.Context, username string) error {
	if s.permissions == nil {
		return nil
	}
	if len(s.permissions.AllowedUsernames) > 0 {
		if _, ok := s.permissions.usernameMap[strings.ToLower(username)]; !ok {
			return fmt.Errorf("username %s is not allowed", username)
		}
	}
	if !s.permissions.AllowAdmins {
		if s.router == nil {
			return fmt.Errorf("permissions check failed: router not available")
		}
		usr, err := s.ds.User(ctx).FindByUsername(username)
		if err != nil {
			if errors.Is(err, model.ErrNotFound) {
				return fmt.Errorf("username %s not found", username)
			}
			return err
		}
		if usr.IsAdmin {
			return fmt.Errorf("calling SubsonicAPI as admin user is not allowed")
		}
	}
	return nil
}

type subsonicAPIPermissions struct {
	AllowedUsernames []string
	AllowAdmins      bool
	usernameMap      map[string]struct{}
}

func parseSubsonicAPIPermissions(data *schema.PluginManifestPermissionsSubsonicapi) *subsonicAPIPermissions {
	if data == nil {
		return &subsonicAPIPermissions{}
	}
	perms := &subsonicAPIPermissions{
		AllowedUsernames: data.AllowedUsernames,
		AllowAdmins:      data.AllowAdmins,
		usernameMap:      make(map[string]struct{}),
	}
	for _, u := range data.AllowedUsernames {
		perms.usernameMap[strings.ToLower(u)] = struct{}{}
	}
	return perms
}