gateway: Turn Symbolic Links Into HTTP Redirects

License: MIT
Signed-off-by: Kevin Atkinson <[email protected]>

Author: kevina

core/coreapi/interface/interface.go

@@ -25,6 +25,7 @@ type UnixfsAPI interface {
 	Add(context.Context, io.Reader) (*cid.Cid, error)
 	Cat(context.Context, string) (Reader, error)
 	Ls(context.Context, string) ([]*Link, error)
+	ReadSymLink(context.Context, string) (string, error) // Read symbolic link
 }
 
 // type ObjectAPI interface {
@@ -50,5 +51,6 @@ type UnixfsAPI interface {
 // }
 
 var ErrIsDir = errors.New("object is a directory")
+var ErrIsSymLink = errors.New("object is a symbolic link")
 var ErrIsNonDag = errors.New("not a merkledag object")
 var ErrOffline = errors.New("can't resolve, ipfs node is offline")

core/coreapi/unixfs.go

@@ -2,13 +2,17 @@ package coreapi
 
 import (
 	"context"
+	"errors"
 	"io"
 
 	core "github.com/ipfs/go-ipfs/core"
 	coreiface "github.com/ipfs/go-ipfs/core/coreapi/interface"
 	coreunix "github.com/ipfs/go-ipfs/core/coreunix"
+	mdag "github.com/ipfs/go-ipfs/merkledag"
 	uio "github.com/ipfs/go-ipfs/unixfs/io"
+	ftpb "github.com/ipfs/go-ipfs/unixfs/pb"
 
+	proto "gx/ipfs/QmZ4Qi3GaRbjcx28Sme5eMH7RQjGkt8wHxt2a65oLaeFEV/gogo-protobuf/proto"
 	cid "gx/ipfs/QmcTcsTvfaeEBRFo1TkFgT8sRmgi1n1LTZpecfVP8fzpGD/go-cid"
 )
 
@@ -36,12 +40,14 @@ func (api *UnixfsAPI) Cat(ctx context.Context, p string) (coreiface.Reader, erro
 	}
 
 	r, err := uio.NewDagReader(ctx, dagnode, api.node.DAG)
-	if err == uio.ErrIsDir {
+	switch err {
+	case uio.ErrIsDir:
 		return nil, coreiface.ErrIsDir
-	} else if err != nil {
-		return nil, err
+	case uio.ErrCantReadSymlinks:
+		return nil, coreiface.ErrIsSymLink
+	default:
 	}
-	return r, nil
+	return r, err;
 }
 
 func (api *UnixfsAPI) Ls(ctx context.Context, p string) ([]*coreiface.Link, error) {
@@ -57,3 +63,27 @@ func (api *UnixfsAPI) Ls(ctx context.Context, p string) ([]*coreiface.Link, erro
 	}
 	return links, nil
 }
+
+var NotASymLink = errors.New("not a symbolic link")
+
+func (api *UnixfsAPI) ReadSymLink(ctx context.Context, p string) (string, error) {
+	dagnode, err := resolve(ctx, api.node, p)
+	if err != nil {
+		return "", err
+	}
+	switch n := dagnode.(type) {
+	case *mdag.ProtoNode:
+		pb := new(ftpb.Data)
+		if err := proto.Unmarshal(n.Data(), pb); err != nil {
+			return "", err
+		}
+		switch pb.GetType() {
+		case ftpb.Data_Symlink:
+			return string(pb.GetData()), nil
+		default:
+			return "", NotASymLink
+		}
+	default:
+		return "", NotASymLink
+	}
+}

core/corehttp/gateway_handler.go

@@ -160,12 +160,15 @@ func (i *gatewayHandler) getOrHeadHandler(ctx context.Context, w http.ResponseWr
 
 	dr, err := i.api.Cat(ctx, urlPath)
 	dir := false
+	symLink := false
 	switch err {
 	case nil:
 		// core.Resolve worked
 		defer dr.Close()
 	case coreiface.ErrIsDir:
 		dir = true
+	case coreiface.ErrIsSymLink:
+		symLink = true
 	case namesys.ErrResolveFailed:
 		// Don't log that error as it is just noise
 		w.WriteHeader(http.StatusInternalServerError)
@@ -225,6 +228,18 @@ func (i *gatewayHandler) getOrHeadHandler(ctx context.Context, w http.ResponseWr
 		modtime = time.Unix(1, 0)
 	}
 
+	if symLink {
+		link, err := i.api.ReadSymLink(ctx, urlPath)
+		if err != nil {
+			internalWebError(w, err)
+			return
+		}
+		newPath := gopath.Join(gopath.Dir(urlPath), link);
+		http.Redirect(w, r, newPath, 302)
+		log.Debugf("symlink: redirect to %s", newPath)
+		return
+	}
+
 	if !dir {
 		name := gopath.Base(urlPath)
 		http.ServeContent(w, r, name, modtime, dr)