path: root/swarm/api/http/server.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

/*
A simple http server interface to Swarm
*/
package http

import (
    "bufio"
    "bytes"
    "encoding/json"
    "fmt"
    "io"
    "io/ioutil"
    "mime"
    "mime/multipart"
    "net/http"
    "os"
    "path"
    "regexp"
    "strconv"
    "strings"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/metrics"
    "github.com/ethereum/go-ethereum/swarm/api"
    "github.com/ethereum/go-ethereum/swarm/log"
    "github.com/ethereum/go-ethereum/swarm/storage"
    "github.com/ethereum/go-ethereum/swarm/storage/mru"

    "github.com/rs/cors"
)

type resourceResponse struct {
    Manifest storage.Address `json:"manifest"`
    Resource string          `json:"resource"`
    Update   storage.Address `json:"update"`
}

var (
    postRawCount    = metrics.NewRegisteredCounter("api.http.post.raw.count", nil)
    postRawFail     = metrics.NewRegisteredCounter("api.http.post.raw.fail", nil)
    postFilesCount  = metrics.NewRegisteredCounter("api.http.post.files.count", nil)
    postFilesFail   = metrics.NewRegisteredCounter("api.http.post.files.fail", nil)
    deleteCount     = metrics.NewRegisteredCounter("api.http.delete.count", nil)
    deleteFail      = metrics.NewRegisteredCounter("api.http.delete.fail", nil)
    getCount        = metrics.NewRegisteredCounter("api.http.get.count", nil)
    getFail         = metrics.NewRegisteredCounter("api.http.get.fail", nil)
    getFileCount    = metrics.NewRegisteredCounter("api.http.get.file.count", nil)
    getFileNotFound = metrics.NewRegisteredCounter("api.http.get.file.notfound", nil)
    getFileFail     = metrics.NewRegisteredCounter("api.http.get.file.fail", nil)
    getListCount    = metrics.NewRegisteredCounter("api.http.get.list.count", nil)
    getListFail     = metrics.NewRegisteredCounter("api.http.get.list.fail", nil)
)

type methodHandler map[string]http.Handler

func (m methodHandler) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
    v, ok := m[r.Method]
    if ok {
        v.ServeHTTP(rw, r)
        return
    }
    rw.WriteHeader(http.StatusMethodNotAllowed)
}

func NewServer(api *api.API, corsString string) *Server {
    var allowedOrigins []string
    for _, domain := range strings.Split(corsString, ",") {
        allowedOrigins = append(allowedOrigins, strings.TrimSpace(domain))
    }
    c := cors.New(cors.Options{
        AllowedOrigins: allowedOrigins,
        AllowedMethods: []string{http.MethodPost, http.MethodGet, http.MethodDelete, http.MethodPatch, http.MethodPut},
        MaxAge:         600,
        AllowedHeaders: []string{"*"},
    })

    server := &Server{api: api}

    defaultMiddlewares := []Adapter{
        RecoverPanic,
        SetRequestID,
        SetRequestHost,
        InitLoggingResponseWriter,
        ParseURI,
        InstrumentOpenTracing,
    }

    mux := http.NewServeMux()
    mux.Handle("/bzz:/", methodHandler{
        "GET": Adapt(
            http.HandlerFunc(server.HandleBzzGet),
            defaultMiddlewares...,
        ),
        "POST": Adapt(
            http.HandlerFunc(server.HandlePostFiles),
            defaultMiddlewares...,
        ),
        "DELETE": Adapt(
            http.HandlerFunc(server.HandleDelete),
            defaultMiddlewares...,
        ),
    })
    mux.Handle("/bzz-raw:/", methodHandler{
        "GET": Adapt(
            http.HandlerFunc(server.HandleGet),
            defaultMiddlewares...,
        ),
        "POST": Adapt(
            http.HandlerFunc(server.HandlePostRaw),
            defaultMiddlewares...,
        ),
    })
    mux.Handle("/bzz-immutable:/", methodHandler{
        "GET": Adapt(
            http.HandlerFunc(server.HandleBzzGet),
            defaultMiddlewares...,
        ),
    })
    mux.Handle("/bzz-hash:/", methodHandler{
        "GET": Adapt(
            http.HandlerFunc(server.HandleGet),
            defaultMiddlewares...,
        ),
    })
    mux.Handle("/bzz-list:/", methodHandler{
        "GET": Adapt(
            http.HandlerFunc(server.HandleGetList),
            defaultMiddlewares...,
        ),
    })
    mux.Handle("/bzz-resource:/", methodHandler{
        "GET": Adapt(
            http.HandlerFunc(server.HandleGetResource),
            defaultMiddlewares...,
        ),
        "POST": Adapt(
            http.HandlerFunc(server.HandlePostResource),
            defaultMiddlewares...,
        ),
    })

    mux.Handle("/", methodHandler{
        "GET": Adapt(
            http.HandlerFunc(server.HandleRootPaths),
            SetRequestID,
            InitLoggingResponseWriter,
        ),
    })
    server.Handler = c.Handler(mux)

    return server
}

func (s *Server) ListenAndServe(addr string) error {
    s.listenAddr = addr
    return http.ListenAndServe(addr, s)
}

// browser API for registering bzz url scheme handlers:
// https://developer.mozilla.org/en/docs/Web-based_protocol_handlers
// electron (chromium) api for registering bzz url scheme handlers:
// https://github.com/atom/electron/blob/master/docs/api/protocol.md
type Server struct {
    http.Handler
    api        *api.API
    listenAddr string
}

func (s *Server) HandleBzzGet(w http.ResponseWriter, r *http.Request) {
    log.Debug("handleBzzGet", "ruid", GetRUID(r.Context()), "uri", r.RequestURI)
    if r.Header.Get("Accept") == "application/x-tar" {
        uri := GetURI(r.Context())
        _, credentials, _ := r.BasicAuth()
        reader, err := s.api.GetDirectoryTar(r.Context(), s.api.Decryptor(r.Context(), credentials), uri)
        if err != nil {
            if isDecryptError(err) {
                w.Header().Set("WWW-Authenticate", fmt.Sprintf("Basic realm=%q", uri.Address().String()))
                RespondError(w, r, err.Error(), http.StatusUnauthorized)
                return
            }
            RespondError(w, r, fmt.Sprintf("Had an error building the tarball: %v", err), http.StatusInternalServerError)
            return
        }
        defer reader.Close()

        w.Header().Set("Content-Type", "application/x-tar")

        fileName := uri.Addr
        if found := path.Base(uri.Path); found != "" && found != "." && found != "/" {
            fileName = found
        }
        w.Header().Set("Content-Disposition", fmt.Sprintf("inline; filename=\"%s.tar\"", fileName))

        w.WriteHeader(http.StatusOK)
        io.Copy(w, reader)
        return
    }

    s.HandleGetFile(w, r)
}

func (s *Server) HandleRootPaths(w http.ResponseWriter, r *http.Request) {
    switch r.RequestURI {
    case "/":
        RespondTemplate(w, r, "landing-page", "Swarm: Please request a valid ENS or swarm hash with the appropriate bzz scheme", 200)
        return
    case "/robots.txt":
        w.Header().Set("Last-Modified", time.Now().Format(http.TimeFormat))
        fmt.Fprintf(w, "User-agent: *\nDisallow: /")
    case "/favicon.ico":
        w.WriteHeader(http.StatusOK)
        w.Write(faviconBytes)
    default:
        RespondError(w, r, "Not Found", http.StatusNotFound)
    }
}

// HandlePostRaw handles a POST request to a raw bzz-raw:/ URI, stores the request
// body in swarm and returns the resulting storage address as a text/plain response
func (s *Server) HandlePostRaw(w http.ResponseWriter, r *http.Request) {
    ruid := GetRUID(r.Context())
    log.Debug("handle.post.raw", "ruid", ruid)

    postRawCount.Inc(1)

    toEncrypt := false
    uri := GetURI(r.Context())
    if uri.Addr == "encrypt" {
        toEncrypt = true
    }

    if uri.Path != "" {
        postRawFail.Inc(1)
        RespondError(w, r, "raw POST request cannot contain a path", http.StatusBadRequest)
        return
    }

    if uri.Addr != "" && uri.Addr != "encrypt" {
        postRawFail.Inc(1)
        RespondError(w, r, "raw POST request addr can only be empty or \"encrypt\"", http.StatusBadRequest)
        return
    }

    if r.Header.Get("Content-Length") == "" {
        postRawFail.Inc(1)
        RespondError(w, r, "missing Content-Length header in request", http.StatusBadRequest)
        return
    }

    addr, _, err := s.api.Store(r.Context(), r.Body, r.ContentLength, toEncrypt)
    if err != nil {
        postRawFail.Inc(1)
        RespondError(w, r, err.Error(), http.StatusInternalServerError)
        return
    }

    log.Debug("stored content", "ruid", ruid, "key", addr)

    w.Header().Set("Content-Type", "text/plain")
    w.WriteHeader(http.StatusOK)
    fmt.Fprint(w, addr)
}

// HandlePostFiles handles a POST request to
// bzz:/<hash>/<path> which contains either a single file or multiple files
// (either a tar archive or multipart form), adds those files either to an
// existing manifest or to a new manifest under <path> and returns the
// resulting manifest hash as a text/plain response
func (s *Server) HandlePostFiles(w http.ResponseWriter, r *http.Request) {
    ruid := GetRUID(r.Context())
    log.Debug("handle.post.files", "ruid", ruid)
    postFilesCount.Inc(1)

    contentType, params, err := mime.ParseMediaType(r.Header.Get("Content-Type"))
    if err != nil {
        postFilesFail.Inc(1)
        RespondError(w, r, err.Error(), http.StatusBadRequest)
        return
    }

    toEncrypt := false
    uri := GetURI(r.Context())
    if uri.Addr == "encrypt" {
        toEncrypt = true
    }

    var addr storage.Address
    if uri.Addr != "" && uri.Addr != "encrypt" {
        addr, err = s.api.Resolve(r.Context(), uri.Addr)
        if err != nil {
            postFilesFail.Inc(1)
            RespondError(w, r, fmt.Sprintf("cannot resolve %s: %s", uri.Addr, err), http.StatusInternalServerError)
            return
        }
        log.Debug("resolved key", "ruid", ruid, "key", addr)
    } else {
        addr, err = s.api.NewManifest(r.Context(), toEncrypt)
        if err != nil {
            postFilesFail.Inc(1)
            RespondError(w, r, err.Error(), http.StatusInternalServerError)
            return
        }
        log.Debug("new manifest", "ruid", ruid, "key", addr)
    }

    newAddr, err := s.api.UpdateManifest(r.Context(), addr, func(mw *api.ManifestWriter) error {
        switch contentType {
        case "application/x-tar":
            _, err := s.handleTarUpload(r, mw)
            if err != nil {
                RespondError(w, r, fmt.Sprintf("error uploading tarball: %v", err), http.StatusInternalServerError)
                return err
            }
            return nil
        case "multipart/form-data":
            return s.handleMultipartUpload(r, params["boundary"], mw)

        default:
            return s.handleDirectUpload(r, mw)
        }
    })
    if err != nil {
        postFilesFail.Inc(1)
        RespondError(w, r, fmt.Sprintf("cannot create manifest: %s", err), http.StatusInternalServerError)
        return
    }

    log.Debug("stored content", "ruid", ruid, "key", newAddr)

    w.Header().Set("Content-Type", "text/plain")
    w.WriteHeader(http.StatusOK)
    fmt.Fprint(w, newAddr)
}

func (s *Server) handleTarUpload(r *http.Request, mw *api.ManifestWriter) (storage.Address, error) {
    log.Debug("handle.tar.upload", "ruid", GetRUID(r.Context()))

    defaultPath := r.URL.Query().Get("defaultpath")

    key, err := s.api.UploadTar(r.Context(), r.Body, GetURI(r.Context()).Path, defaultPath, mw)
    if err != nil {
        return nil, err
    }
    return key, nil
}

func (s *Server) handleMultipartUpload(r *http.Request, boundary string, mw *api.ManifestWriter) error {
    ruid := GetRUID(r.Context())
    log.Debug("handle.multipart.upload", "ruid", ruid)
    mr := multipart.NewReader(r.Body, boundary)
    for {
        part, err := mr.NextPart()
        if err == io.EOF {
            return nil
        } else if err != nil {
            return fmt.Errorf("error reading multipart form: %s", err)
        }

        var size int64
        var reader io.Reader = part
        if contentLength := part.Header.Get("Content-Length"); contentLength != "" {
            size, err = strconv.ParseInt(contentLength, 10, 64)
            if err != nil {
                return fmt.Errorf("error parsing multipart content length: %s", err)
            }
            reader = part
        } else {
            // copy the part to a tmp file to get its size
            tmp, err := ioutil.TempFile("", "swarm-multipart")
            if err != nil {
                return err
            }
            defer os.Remove(tmp.Name())
            defer tmp.Close()
            size, err = io.Copy(tmp, part)
            if err != nil {
                return fmt.Errorf("error copying multipart content: %s", err)
            }
            if _, err := tmp.Seek(0, io.SeekStart); err != nil {
                return fmt.Errorf("error copying multipart content: %s", err)
            }
            reader = tmp
        }

        // add the entry under the path from the request
        name := part.FileName()
        if name == "" {
            name = part.FormName()
        }
        uri := GetURI(r.Context())
        path := path.Join(uri.Path, name)
        entry := &api.ManifestEntry{
            Path:        path,
            ContentType: part.Header.Get("Content-Type"),
            Size:        size,
            ModTime:     time.Now(),
        }
        log.Debug("adding path to new manifest", "ruid", ruid, "bytes", entry.Size, "path", entry.Path)
        contentKey, err := mw.AddEntry(r.Context(), reader, entry)
        if err != nil {
            return fmt.Errorf("error adding manifest entry from multipart form: %s", err)
        }
        log.Debug("stored content", "ruid", ruid, "key", contentKey)
    }
}

func (s *Server) handleDirectUpload(r *http.Request, mw *api.ManifestWriter) error {
    ruid := GetRUID(r.Context())
    log.Debug("handle.direct.upload", "ruid", ruid)
    key, err := mw.AddEntry(r.Context(), r.Body, &api.ManifestEntry{
        Path:        GetURI(r.Context()).Path,
        ContentType: r.Header.Get("Content-Type"),
        Mode:        0644,
        Size:        r.ContentLength,
        ModTime:     time.Now(),
    })
    if err != nil {
        return err
    }
    log.Debug("stored content", "ruid", ruid, "key", key)
    return nil
}

// HandleDelete handles a DELETE request to bzz:/<manifest>/<path>, removes
// <path> from <manifest> and returns the resulting manifest hash as a
// text/plain response
func (s *Server) HandleDelete(w http.ResponseWriter, r *http.Request) {
    ruid := GetRUID(r.Context())
    uri := GetURI(r.Context())
    log.Debug("handle.delete", "ruid", ruid)
    deleteCount.Inc(1)
    newKey, err := s.api.Delete(r.Context(), uri.Addr, uri.Path)
    if err != nil {
        deleteFail.Inc(1)
        RespondError(w, r, fmt.Sprintf("could not delete from manifest: %v", err), http.StatusInternalServerError)
        return
    }

    w.Header().Set("Content-Type", "text/plain")
    w.WriteHeader(http.StatusOK)
    fmt.Fprint(w, newKey)
}

// Parses a resource update post url to corresponding action
// possible combinations:
// /            add multihash update to existing hash
// /raw         add raw update to existing hash
// /#           create new resource with first update as mulitihash
// /raw/#       create new resource with first update raw
func resourcePostMode(path string) (isRaw bool, frequency uint64, err error) {
    re, err := regexp.Compile("^(raw)?/?([0-9]+)?$")
    if err != nil {
        return isRaw, frequency, err
    }
    m := re.FindAllStringSubmatch(path, 2)
    var freqstr = "0"
    if len(m) > 0 {
        if m[0][1] != "" {
            isRaw = true
        }
        if m[0][2] != "" {
            freqstr = m[0][2]
        }
    } else if len(path) > 0 {
        return isRaw, frequency, fmt.Errorf("invalid path")
    }
    frequency, err = strconv.ParseUint(freqstr, 10, 64)
    return isRaw, frequency, err
}

// Handles creation of new mutable resources and adding updates to existing mutable resources
// There are two types of updates available, "raw" and "multihash."
// If the latter is used, a subsequent bzz:// GET call to the manifest of the resource will return
// the page that the multihash is pointing to, as if it held a normal swarm content manifest
//
// The POST request admits a JSON structure as defined in the mru package: `mru.updateRequestJSON`
// The requests can be to a) create a resource, b) update a resource or c) both a+b: create a resource and set the initial content
func (s *Server) HandlePostResource(w http.ResponseWriter, r *http.Request) {
    ruid := GetRUID(r.Context())
    uri := GetURI(r.Context())
    log.Debug("handle.post.resource", "ruid", ruid)
    var err error

    // Creation and update must send mru.updateRequestJSON JSON structure
    body, err := ioutil.ReadAll(r.Body)
    if err != nil {
        RespondError(w, r, err.Error(), http.StatusInternalServerError)
        return
    }

    view, err := s.api.ResolveResourceView(r.Context(), uri, r.URL.Query())
    if err != nil { // couldn't parse query string or retrieve manifest
        getFail.Inc(1)
        httpStatus := http.StatusBadRequest
        if err == api.ErrCannotLoadResourceManifest || err == api.ErrCannotResolveResourceURI {
            httpStatus = http.StatusNotFound
        }
        RespondError(w, r, fmt.Sprintf("cannot retrieve resource view: %s", err), httpStatus)
        return
    }

    var updateRequest mru.Request
    updateRequest.Feed = *view
    query := r.URL.Query()

    if err := updateRequest.FromValues(query, body); err != nil { // decodes request from query parameters
        RespondError(w, r, err.Error(), http.StatusBadRequest)
        return
    }

    if updateRequest.IsUpdate() {
        // Verify that the signature is intact and that the signer is authorized
        // to update this resource
        // Check this early, to avoid creating a resource and then not being able to set its first update.
        if err = updateRequest.Verify(); err != nil {
            RespondError(w, r, err.Error(), http.StatusForbidden)
            return
        }
        _, err = s.api.ResourceUpdate(r.Context(), &updateRequest)
        if err != nil {
            RespondError(w, r, err.Error(), http.StatusInternalServerError)
            return
        }
    }

    if query.Get("manifest") == "1" {
        // we create a manifest so we can retrieve the resource with bzz:// later
        // this manifest has a special "resource type" manifest, and saves the
        // resource view ID used to retrieve the resource later
        m, err := s.api.NewResourceManifest(r.Context(), &updateRequest.Feed)
        if err != nil {
            RespondError(w, r, fmt.Sprintf("failed to create resource manifest: %v", err), http.StatusInternalServerError)
            return
        }
        // the key to the manifest will be passed back to the client
        // the client can access the view  directly through its resourceView member
        // the manifest key can be set as content in the resolver of the ENS name
        outdata, err := json.Marshal(m)
        if err != nil {
            RespondError(w, r, fmt.Sprintf("failed to create json response: %s", err), http.StatusInternalServerError)
            return
        }
        fmt.Fprint(w, string(outdata))

        w.Header().Add("Content-type", "application/json")
    }
}

// Retrieve Swarm Feeds:
// bzz-resource://<id> - get latest update
// bzz-resource://<id>/?period=n - get latest update on period n
// bzz-resource://<id>/?period=n&version=m - get update version m of period n
// bzz-resource://<id>/meta - get metadata and next version information
// <id> = ens name or hash
// TODO: Enable pass maxPeriod parameter
func (s *Server) HandleGetResource(w http.ResponseWriter, r *http.Request) {
    ruid := GetRUID(r.Context())
    uri := GetURI(r.Context())
    log.Debug("handle.get.resource", "ruid", ruid)
    var err error

    view, err := s.api.ResolveResourceView(r.Context(), uri, r.URL.Query())
    if err != nil { // couldn't parse query string or retrieve manifest
        getFail.Inc(1)
        httpStatus := http.StatusBadRequest
        if err == api.ErrCannotLoadResourceManifest || err == api.ErrCannotResolveResourceURI {
            httpStatus = http.StatusNotFound
        }
        RespondError(w, r, fmt.Sprintf("cannot retrieve resource view: %s", err), httpStatus)
        return
    }

    // determine if the query specifies period and version or it is a metadata query
    if r.URL.Query().Get("meta") == "1" {
        unsignedUpdateRequest, err := s.api.ResourceNewRequest(r.Context(), view)
        if err != nil {
            getFail.Inc(1)
            RespondError(w, r, fmt.Sprintf("cannot retrieve resource metadata for view=%s: %s", view.Hex(), err), http.StatusNotFound)
            return
        }
        rawResponse, err := unsignedUpdateRequest.MarshalJSON()
        if err != nil {
            RespondError(w, r, fmt.Sprintf("cannot encode unsigned UpdateRequest: %v", err), http.StatusInternalServerError)
            return
        }
        w.Header().Add("Content-type", "application/json")
        w.WriteHeader(http.StatusOK)
        fmt.Fprint(w, string(rawResponse))
        return
    }

    lookupParams := &mru.Query{Feed: *view}
    if err = lookupParams.FromValues(r.URL.Query()); err != nil { // parse period, version
        RespondError(w, r, fmt.Sprintf("invalid mutable resource request:%s", err), http.StatusBadRequest)
        return
    }

    data, err := s.api.ResourceLookup(r.Context(), lookupParams)

    // any error from the switch statement will end up here
    if err != nil {
        code, err2 := s.translateResourceError(w, r, "mutable resource lookup fail", err)
        RespondError(w, r, err2.Error(), code)
        return
    }

    // All ok, serve the retrieved update
    log.Debug("Found update", "view", view.Hex(), "ruid", ruid)
    w.Header().Set("Content-Type", api.MimeOctetStream)
    http.ServeContent(w, r, "", time.Now(), bytes.NewReader(data))
}

func (s *Server) translateResourceError(w http.ResponseWriter, r *http.Request, supErr string, err error) (int, error) {
    code := 0
    defaultErr := fmt.Errorf("%s: %v", supErr, err)
    rsrcErr, ok := err.(*mru.Error)
    if !ok && rsrcErr != nil {
        code = rsrcErr.Code()
    }
    switch code {
    case storage.ErrInvalidValue:
        return http.StatusBadRequest, defaultErr
    case storage.ErrNotFound, storage.ErrNotSynced, storage.ErrNothingToReturn, storage.ErrInit:
        return http.StatusNotFound, defaultErr
    case storage.ErrUnauthorized, storage.ErrInvalidSignature:
        return http.StatusUnauthorized, defaultErr
    case storage.ErrDataOverflow:
        return http.StatusRequestEntityTooLarge, defaultErr
    }

    return http.StatusInternalServerError, defaultErr
}

// HandleGet handles a GET request to
// - bzz-raw://<key> and responds with the raw content stored at the
//   given storage key
// - bzz-hash://<key> and responds with the hash of the content stored
//   at the given storage key as a text/plain response
func (s *Server) HandleGet(w http.ResponseWriter, r *http.Request) {
    ruid := GetRUID(r.Context())
    uri := GetURI(r.Context())
    log.Debug("handle.get", "ruid", ruid, "uri", uri)
    getCount.Inc(1)
    _, pass, _ := r.BasicAuth()

    addr, err := s.api.ResolveURI(r.Context(), uri, pass)
    if err != nil {
        getFail.Inc(1)
        RespondError(w, r, fmt.Sprintf("cannot resolve %s: %s", uri.Addr, err), http.StatusNotFound)
        return
    }
    w.Header().Set("Cache-Control", "max-age=2147483648, immutable") // url was of type bzz://<hex key>/path, so we are sure it is immutable.

    log.Debug("handle.get: resolved", "ruid", ruid, "key", addr)

    // if path is set, interpret <key> as a manifest and return the
    // raw entry at the given path

    etag := common.Bytes2Hex(addr)
    noneMatchEtag := r.Header.Get("If-None-Match")
    w.Header().Set("ETag", fmt.Sprintf("%q", etag)) // set etag to manifest key or raw entry key.
    if noneMatchEtag != "" {
        if bytes.Equal(storage.Address(common.Hex2Bytes(noneMatchEtag)), addr) {
            w.WriteHeader(http.StatusNotModified)
            return
        }
    }

    // check the root chunk exists by retrieving the file's size
    reader, isEncrypted := s.api.Retrieve(r.Context(), addr)
    if _, err := reader.Size(r.Context(), nil); err != nil {
        getFail.Inc(1)
        RespondError(w, r, fmt.Sprintf("root chunk not found %s: %s", addr, err), http.StatusNotFound)
        return
    }

    w.Header().Set("X-Decrypted", fmt.Sprintf("%v", isEncrypted))

    switch {
    case uri.Raw():
        // allow the request to overwrite the content type using a query
        // parameter
        if typ := r.URL.Query().Get("content_type"); typ != "" {
            w.Header().Set("Content-Type", typ)
        }
        http.ServeContent(w, r, "", time.Now(), reader)
    case uri.Hash():
        w.Header().Set("Content-Type", "text/plain")
        w.WriteHeader(http.StatusOK)
        fmt.Fprint(w, addr)
    }
}

// HandleGetList handles a GET request to bzz-list:/<manifest>/<path> and returns
// a list of all files contained in <manifest> under <path> grouped into
// common prefixes using "/" as a delimiter
func (s *Server) HandleGetList(w http.ResponseWriter, r *http.Request) {
    ruid := GetRUID(r.Context())
    uri := GetURI(r.Context())
    _, credentials, _ := r.BasicAuth()
    log.Debug("handle.get.list", "ruid", ruid, "uri", uri)
    getListCount.Inc(1)

    // ensure the root path has a trailing slash so that relative URLs work
    if uri.Path == "" && !strings.HasSuffix(r.URL.Path, "/") {
        http.Redirect(w, r, r.URL.Path+"/", http.StatusMovedPermanently)
        return
    }

    addr, err := s.api.Resolve(r.Context(), uri.Addr)
    if err != nil {
        getListFail.Inc(1)
        RespondError(w, r, fmt.Sprintf("cannot resolve %s: %s", uri.Addr, err), http.StatusNotFound)
        return
    }
    log.Debug("handle.get.list: resolved", "ruid", ruid, "key", addr)

    list, err := s.api.GetManifestList(r.Context(), s.api.Decryptor(r.Context(), credentials), addr, uri.Path)
    if err != nil {
        getListFail.Inc(1)
        if isDecryptError(err) {
            w.Header().Set("WWW-Authenticate", fmt.Sprintf("Basic realm=%q", addr.String()))
            RespondError(w, r, err.Error(), http.StatusUnauthorized)
            return
        }
        RespondError(w, r, err.Error(), http.StatusInternalServerError)
        return
    }

    // if the client wants HTML (e.g. a browser) then render the list as a
    // HTML index with relative URLs
    if strings.Contains(r.Header.Get("Accept"), "text/html") {
        w.Header().Set("Content-Type", "text/html")
        err := TemplatesMap["bzz-list"].Execute(w, &htmlListData{
            URI: &api.URI{
                Scheme: "bzz",
                Addr:   uri.Addr,
                Path:   uri.Path,
            },
            List: &list,
        })
        if err != nil {
            getListFail.Inc(1)
            log.Error(fmt.Sprintf("error rendering list HTML: %s", err))
        }
        return
    }

    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(&list)
}

// HandleGetFile handles a GET request to bzz://<manifest>/<path> and responds
// with the content of the file at <path> from the given <manifest>
func (s *Server) HandleGetFile(w http.ResponseWriter, r *http.Request) {
    ruid := GetRUID(r.Context())
    uri := GetURI(r.Context())
    _, credentials, _ := r.BasicAuth()
    log.Debug("handle.get.file", "ruid", ruid, "uri", r.RequestURI)
    getFileCount.Inc(1)

    // ensure the root path has a trailing slash so that relative URLs work
    if uri.Path == "" && !strings.HasSuffix(r.URL.Path, "/") {
        http.Redirect(w, r, r.URL.Path+"/", http.StatusMovedPermanently)
        return
    }
    var err error
    manifestAddr := uri.Address()

    if manifestAddr == nil {
        manifestAddr, err = s.api.Resolve(r.Context(), uri.Addr)
        if err != nil {
            getFileFail.Inc(1)
            RespondError(w, r, fmt.Sprintf("cannot resolve %s: %s", uri.Addr, err), http.StatusNotFound)
            return
        }
    } else {
        w.Header().Set("Cache-Control", "max-age=2147483648, immutable") // url was of type bzz://<hex key>/path, so we are sure it is immutable.
    }

    log.Debug("handle.get.file: resolved", "ruid", ruid, "key", manifestAddr)

    reader, contentType, status, contentKey, err := s.api.Get(r.Context(), s.api.Decryptor(r.Context(), credentials), manifestAddr, uri.Path)

    etag := common.Bytes2Hex(contentKey)
    noneMatchEtag := r.Header.Get("If-None-Match")
    w.Header().Set("ETag", fmt.Sprintf("%q", etag)) // set etag to actual content key.
    if noneMatchEtag != "" {
        if bytes.Equal(storage.Address(common.Hex2Bytes(noneMatchEtag)), contentKey) {
            w.WriteHeader(http.StatusNotModified)
            return
        }
    }

    if err != nil {
        if isDecryptError(err) {
            w.Header().Set("WWW-Authenticate", fmt.Sprintf("Basic realm=%q", manifestAddr))
            RespondError(w, r, err.Error(), http.StatusUnauthorized)
            return
        }

        switch status {
        case http.StatusNotFound:
            getFileNotFound.Inc(1)
            RespondError(w, r, err.Error(), http.StatusNotFound)
        default:
            getFileFail.Inc(1)
            RespondError(w, r, err.Error(), http.StatusInternalServerError)
        }
        return
    }

    //the request results in ambiguous files
    //e.g. /read with readme.md and readinglist.txt available in manifest
    if status == http.StatusMultipleChoices {
        list, err := s.api.GetManifestList(r.Context(), s.api.Decryptor(r.Context(), credentials), manifestAddr, uri.Path)
        if err != nil {
            getFileFail.Inc(1)
            if isDecryptError(err) {
                w.Header().Set("WWW-Authenticate", fmt.Sprintf("Basic realm=%q", manifestAddr))
                RespondError(w, r, err.Error(), http.StatusUnauthorized)
                return
            }
            RespondError(w, r, err.Error(), http.StatusInternalServerError)
            return
        }

        log.Debug(fmt.Sprintf("Multiple choices! --> %v", list), "ruid", ruid)
        //show a nice page links to available entries
        ShowMultipleChoices(w, r, list)
        return
    }

    // check the root chunk exists by retrieving the file's size
    if _, err := reader.Size(r.Context(), nil); err != nil {
        getFileNotFound.Inc(1)
        RespondError(w, r, fmt.Sprintf("file not found %s: %s", uri, err), http.StatusNotFound)
        return
    }

    if contentType != "" {
        w.Header().Set("Content-Type", contentType)
    }

    fileName := uri.Addr
    if found := path.Base(uri.Path); found != "" && found != "." && found != "/" {
        fileName = found
    }
    w.Header().Set("Content-Disposition", fmt.Sprintf("inline; filename=\"%s\"", fileName))

    http.ServeContent(w, r, fileName, time.Now(), newBufferedReadSeeker(reader, getFileBufferSize))
}

// The size of buffer used for bufio.Reader on LazyChunkReader passed to
// http.ServeContent in HandleGetFile.
// Warning: This value influences the number of chunk requests and chunker join goroutines
// per file request.
// Recommended value is 4 times the io.Copy default buffer value which is 32kB.
const getFileBufferSize = 4 * 32 * 1024

// bufferedReadSeeker wraps bufio.Reader to expose Seek method
// from the provied io.ReadSeeker in newBufferedReadSeeker.
type bufferedReadSeeker struct {
    r io.Reader
    s io.Seeker
}

// newBufferedReadSeeker creates a new instance of bufferedReadSeeker,
// out of io.ReadSeeker. Argument `size` is the size of the read buffer.
func newBufferedReadSeeker(readSeeker io.ReadSeeker, size int) bufferedReadSeeker {
    return bufferedReadSeeker{
        r: bufio.NewReaderSize(readSeeker, size),
        s: readSeeker,
    }
}

func (b bufferedReadSeeker) Read(p []byte) (n int, err error) {
    return b.r.Read(p)
}

func (b bufferedReadSeeker) Seek(offset int64, whence int) (int64, error) {
    return b.s.Seek(offset, whence)
}

type loggingResponseWriter struct {
    http.ResponseWriter
    statusCode int
}

func newLoggingResponseWriter(w http.ResponseWriter) *loggingResponseWriter {
    return &loggingResponseWriter{w, http.StatusOK}
}

func (lrw *loggingResponseWriter) WriteHeader(code int) {
    lrw.statusCode = code
    lrw.ResponseWriter.WriteHeader(code)
}

func isDecryptError(err error) bool {
    return strings.Contains(err.Error(), api.ErrDecrypt.Error())
}