Add readonly api to gateway

Issue ipfs#1322

Added the ability to expose individual commands to a read-only style
handler that can be used on any http interface.

Added the read-only handler to the gateway.

cmd/ipfs/daemon.go

@@ -281,7 +281,7 @@ func serveHTTPApi(req cmds.Request) (error, <-chan error) {
 	var opts = []corehttp.ServeOption{
 		corehttp.CommandsOption(*req.Context()),
 		corehttp.WebUIOption,
-		apiGw.ServeOption(),
+		apiGw.ServeOption(nil),
 		corehttp.VersionOption(),
 		defaultMux("/debug/vars"),
 		defaultMux("/debug/pprof/"),
@@ -339,7 +339,7 @@ func serveHTTPGateway(req cmds.Request) (error, <-chan error) {
 	var opts = []corehttp.ServeOption{
 		corehttp.VersionOption(),
 		corehttp.IPNSHostnameOption(),
-		corehttp.GatewayOption(writable),
+		corehttp.GatewayOption(writable, req.Context()),
 	}
 
 	if len(cfg.Gateway.RootRedirect) > 0 {

commands/http/handler.go

@@ -12,6 +12,7 @@ import (
 	context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
 
 	cmds "github.com/ipfs/go-ipfs/commands"
+	commands "github.com/ipfs/go-ipfs/core/commands"
 	u "github.com/ipfs/go-ipfs/util"
 )
 
@@ -21,6 +22,7 @@ var log = u.Logger("commands/http")
 type internalHandler struct {
 	ctx  cmds.Context
 	root *cmds.Command
+	readOnly bool
 }
 
 // The Handler struct is funny because we want to wrap our internal handler
@@ -47,14 +49,18 @@ var mimeTypes = map[string]string{
 	cmds.Text: "text/plain",
 }
 
+var readOnlyCmds = map[*cmds.Command]bool{
+	commands.RefsCmd: true,
+}
+
 func NewHandler(ctx cmds.Context, root *cmds.Command, allowedOrigin string) *Handler {
 	// allow whitelisted origins (so we can make API requests from the browser)
 	if len(allowedOrigin) > 0 {
 		log.Info("Allowing API requests from origin: " + allowedOrigin)
 	}
 
 	// Create a handler for the API.
-	internal := internalHandler{ctx, root}
+	internal := internalHandler{ctx, root, false}
 
 	// Create a CORS object for wrapping the internal handler.
 	c := cors.New(cors.Options{
@@ -71,6 +77,32 @@ func NewHandler(ctx cmds.Context, root *cmds.Command, allowedOrigin string) *Han
 	return &Handler{internal, c.Handler(internal)}
 }
 
+func NewReadOnlyHandler(ctx cmds.Context, root *cmds.Command, allowedOrigin string) *Handler {
+	// allow whitelisted origins (so we can make API requests from the browser)
+	if len(allowedOrigin) > 0 {
+		log.Info("Allowing API requests from origin: " + allowedOrigin)
+	}
+
+	// Create a handler for the API.
+	internal := internalHandler{ctx, root, true}
+
+	// Create a CORS object for wrapping the internal handler.
+	c := cors.New(cors.Options{
+		AllowedMethods: []string{"GET"},
+
+		// use AllowOriginFunc instead of AllowedOrigins because we want to be
+		// restrictive by default.
+		AllowOriginFunc: func(origin string) bool {
+			return (allowedOrigin == "*") || (origin == allowedOrigin)
+		},
+	})
+
+	fmt.Println("Read Only API")
+
+	// Wrap the internal handler with CORS handling-middleware.
+	return &Handler{internal, c.Handler(internal)}
+}
+
 func (i internalHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	log.Debug("Incoming API request: ", r.URL)
 
@@ -89,6 +121,7 @@ func (i internalHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	req, err := Parse(r, i.root)
+
 	if err != nil {
 		if err == ErrNotFound {
 			w.WriteHeader(http.StatusNotFound)
@@ -99,6 +132,15 @@ func (i internalHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if i.readOnly == true {
+		if _, ok := readOnlyCmds[req.Command()]; !ok {
+			// Or a 404?
+			w.WriteHeader(http.StatusForbidden)
+			w.Write([]byte("You may not execute this request on the read-only api."))
+			return
+		}
+	}
+
 	// get the node's context to pass into the commands.
 	node, err := i.ctx.GetNode()
 	if err != nil {

core/corehttp/gateway.go

@@ -4,7 +4,11 @@ import (
 	"fmt"
 	"net/http"
 	"sync"
+	"os"
 
+	commands "github.com/ipfs/go-ipfs/commands"
+	cmdsHttp "github.com/ipfs/go-ipfs/commands/http"
+	corecommands "github.com/ipfs/go-ipfs/core/commands"
 	core "github.com/ipfs/go-ipfs/core"
 	id "github.com/ipfs/go-ipfs/p2p/protocol/identify"
 )
@@ -25,26 +29,34 @@ func NewGateway(conf GatewayConfig) *Gateway {
 	}
 }
 
-func (g *Gateway) ServeOption() ServeOption {
+func (g *Gateway) ServeOption(cctx * commands.Context) ServeOption {
 	return func(n *core.IpfsNode, mux *http.ServeMux) (*http.ServeMux, error) {
 		gateway, err := newGatewayHandler(n, g.Config)
 		if err != nil {
 			return nil, err
 		}
 		mux.Handle("/ipfs/", gateway)
 		mux.Handle("/ipns/", gateway)
+
+		if cctx != nil {
+			origin := os.Getenv(originEnvKey)
+			cmdHandler := cmdsHttp.NewReadOnlyHandler(*cctx, corecommands.Root, origin)
+			mux.Handle(cmdsHttp.ApiPath+"/", cmdHandler)
+		}
 		return mux, nil
 	}
 }
 
-func GatewayOption(writable bool) ServeOption {
+
+func GatewayOption(writable bool, cctx * commands.Context) ServeOption {
 	g := NewGateway(GatewayConfig{
 		Writable:  writable,
 		BlockList: &BlockList{},
 	})
-	return g.ServeOption()
+	return g.ServeOption(cctx)
 }
 
+
 func VersionOption() ServeOption {
 	return func(n *core.IpfsNode, mux *http.ServeMux) (*http.ServeMux, error) {
 		mux.HandleFunc("/version", func(w http.ResponseWriter, r *http.Request) {