multi: add and use DynamicPrice option

This commit adds a DynamicPrice member to the Services struct and uses
its values to determine if a GRPCPricer or DefaultPricer should be
initialised. The commit also updates the sample-conf.yaml file with the
new config options.

proxy/proxy.go

@@ -104,21 +104,50 @@ func (p *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	resourceName := target.ResourceName(r.URL.Path)
+
 	// Determine auth level required to access service and dispatch request
 	// accordingly.
 	authLevel := target.AuthRequired(r)
 	switch {
 	case authLevel.IsOn():
-		if !p.authenticator.Accept(&r.Header, target.Name) {
+		// Determine if the header contains the authentication
+		// required for the given resource. The call to Accept is
+		// called in each case body rather than outside the switch so
+		// as to avoid calling this possibly expensive call for static
+		// resources.
+		acceptAuth := p.authenticator.Accept(&r.Header, resourceName)
+		if !acceptAuth {
+			price, err := target.pricer.GetPrice(
+				r.Context(), r.URL.Path,
+			)
+			if err != nil {
+				prefixLog.Errorf("error getting "+
+					"resource price: %v", err)
+				sendDirectResponse(
+					w, r, http.StatusInternalServerError,
+					"failure fetching "+
+						"resource price",
+				)
+				return
+			}
+
+			// If the price returned is zero, then break out of the
+			// switch statement and allow access to the service.
+			if price == 0 {
+				break
+			}
+
 			prefixLog.Infof("Authentication failed. Sending 402.")
-			p.handlePaymentRequired(w, r, target.Name, target.Price)
+			p.handlePaymentRequired(w, r, resourceName, price)
 			return
 		}
 
 	case authLevel.IsFreebie():
 		// We only need to respect the freebie counter if the user
 		// is not authenticated at all.
-		if !p.authenticator.Accept(&r.Header, target.Name) {
+		acceptAuth := p.authenticator.Accept(&r.Header, resourceName)
+		if !acceptAuth {
 			ok, err := target.freebieDb.CanPass(r, remoteIP)
 			if err != nil {
 				prefixLog.Errorf("Error querying freebie db: "+
@@ -130,7 +159,30 @@ func (p *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 				return
 			}
 			if !ok {
-				p.handlePaymentRequired(w, r, target.Name, target.Price)
+				price, err := target.pricer.GetPrice(
+					r.Context(), r.URL.Path,
+				)
+				if err != nil {
+					prefixLog.Errorf("error getting "+
+						"resource price: %v", err)
+					sendDirectResponse(
+						w, r, http.StatusInternalServerError,
+						"failure fetching "+
+							"resource price",
+					)
+					return
+				}
+
+				// If the price returned is zero, then break
+				// out of the switch statement and allow access
+				// to the service.
+				if price == 0 {
+					break
+				}
+
+				p.handlePaymentRequired(
+					w, r, resourceName, target.Price,
+				)
 				return
 			}
 			_, err = target.freebieDb.TallyFreebie(r, remoteIP)
@@ -188,7 +240,16 @@ func (p *Proxy) UpdateServices(services []*Service) error {
 
 // Close cleans up the Proxy by closing any remaining open connections.
 func (p *Proxy) Close() error {
-	return nil
+	var returnErr error
+	for _, s := range p.services {
+		if err := s.pricer.Close(); err != nil {
+			log.Errorf("error while closing the pricer of "+
+				"service %s: %v", s.Name, err)
+			returnErr = err
+		}
+	}
+
+	return returnErr
 }
 
 // director is a method that rewrites an incoming request to be forwarded to a

proxy/service.go

@@ -12,6 +12,7 @@ import (
 	"github.com/btcsuite/btcutil"
 	"github.com/lightninglabs/aperture/auth"
 	"github.com/lightninglabs/aperture/freebie"
+	"github.com/lightninglabs/aperture/pricer"
 )
 
 var (
@@ -84,6 +85,10 @@ type Service struct {
 	// service's endpoint.
 	Price int64 `long:"price" description:"Static LSAT value in satoshis to be used for this service"`
 
+	// DynamicPrice holds the config options needed for initialising
+	// the pricer if a gPRC server is to be used for price data.
+	DynamicPrice pricer.Config `long:"dynamicprice" description:"Configuration for connecting to the gRPC server to use for the pricer backend"`
+
 	// AuthWhitelistPaths is an optional list of regular expressions that
 	// are matched against the path of the URL of a request. If the request
 	// URL matches any of those regular expressions, the call is treated as
@@ -93,6 +98,20 @@ type Service struct {
 	AuthWhitelistPaths []string `long:"authwhitelistpaths" description:"List of regular expressions for paths that don't require authentication'"`
 
 	freebieDb freebie.DB
+	pricer    pricer.Pricer
+}
+
+// ResourceName returns the string to be used to identify which resource a
+// macaroon has access to. If DynamicPrice Enabled option is set to true then
+// the service has further restrictions per resource and so the name will
+// include both the service name and the specific resource name. Otherwise
+// authorisation is only restricted by service name.
+func (s *Service) ResourceName(resourcePath string) string {
+	if s.DynamicPrice.Enabled {
+		return fmt.Sprintf("%s%s", s.Name, resourcePath)
+	}
+
+	return s.Name
 }
 
 // AuthRequired determines the auth level required for a given request.
@@ -170,6 +189,22 @@ func prepareServices(services []*Service) error {
 			}
 		}
 
+		// If dynamic prices are enabled then use the provided
+		// DynamicPrice options to initialise a gRPC backed
+		// pricer client.
+		if service.DynamicPrice.Enabled {
+			priceClient, err := pricer.NewGRPCPricer(
+				&service.DynamicPrice,
+			)
+			if err != nil {
+				return fmt.Errorf("error initializing "+
+					"pricer: %v", err)
+			}
+
+			service.pricer = priceClient
+			continue
+		}
+
 		// Check that the price for the service is not negative and not
 		// more than the maximum amount allowed by lnd. If no price, or
 		// a price of zero satoshis, is set the then default price of 1
@@ -186,6 +221,10 @@ func prepareServices(services []*Service) error {
 			return fmt.Errorf("maximum price exceeded for "+
 				"service %s", service.Name)
 		}
+
+		// Initialise a default pricer where all resources in a server
+		// are given the same price.
+		service.pricer = pricer.NewDefaultPricer(service.Price)
 	}
 	return nil
 }

sample-conf.yaml

@@ -82,8 +82,26 @@ services:
     constraints:
         "valid_until": "2020-01-01"
 
-    # The LSAT value in satoshis for the service.
-    price: 1     
+    # The LSAT value in satoshis for the service. It is ignored if
+    # dynamicprice.enabled is set to true.
+    price: 0
+
+    # Options to use for connection to the price serving gRPC server.
+    dynamicprice:
+      # Whether or not a gRPC server is available to query price data from. If
+      # this option is set to true then the 'price' option is ignored.
+      enabled: true
+
+      # The address of the gRPC pricer server.
+      grpcaddress: "127.0.0.1:10010"
+
+      # Whether or not TLS encryption should be used for communications with the
+      # gRPC server.
+      insecure: false
+
+      # The path to the pricer server's tls.cert. If the 'insecure' option is
+      # set to true then this path must be set.
+      tlscertpath: "path-to-pricer-server-tls-cert/tls.cert"
 
   - name: "service2"
     hostregexp: "service2.com:8083"
@@ -94,6 +112,19 @@ services:
         "valid_until": "2020-01-01"
     price: 1
 
+  - name: "service3"
+    hostregexp: "service3.com:8083"
+    pathregexp: '^/.*$'
+    address: "123.456.789:8082"
+    protocol: https
+    constraints:
+        "valid_until": "2020-01-01"
+    dynamicprice:
+      enbled: true
+      grpcaddress: 123.456.789:8083
+      insecure: false
+      tlscertpath: "path-to-pricer-server-tls-cert/tls.cert"
+
 # Settings for a Tor instance to allow requests over Tor as onion services.
 # Configuring Tor is optional.
 tor: