container: add support for uploading to registries

Add a new generic container registry client via a new `container`
package. Use this to create a command line utility as well as a
new upload target for container registries.

The code uses the github.com/containers/* project and packages to
interact with container registires that is also used by skopeo,
podman et al. One if the dependencies is `proglottis/gpgme` that
is using cgo to bind libgpgme, so we have to add the corresponding
devel package to the BuildRequires as well as installing it on CI.

Checks will follow later via an integration test.

vendor/github.com/docker/distribution/registry/client/auth/challenge/addr.go

@@ -0,0 +1,27 @@
+package challenge
+
+import (
+	"net/url"
+	"strings"
+)
+
+// FROM: https://golang.org/src/net/http/http.go
+// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
+// return true if the string includes a port.
+func hasPort(s string) bool { return strings.LastIndex(s, ":") > strings.LastIndex(s, "]") }
+
+// FROM: http://golang.org/src/net/http/transport.go
+var portMap = map[string]string{
+	"http":  "80",
+	"https": "443",
+}
+
+// canonicalAddr returns url.Host but always with a ":port" suffix
+// FROM: http://golang.org/src/net/http/transport.go
+func canonicalAddr(url *url.URL) string {
+	addr := url.Host
+	if !hasPort(addr) {
+		return addr + ":" + portMap[url.Scheme]
+	}
+	return addr
+}

vendor/github.com/docker/distribution/registry/client/auth/challenge/authchallenge.go

@@ -0,0 +1,237 @@
+package challenge
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+	"sync"
+)
+
+// Challenge carries information from a WWW-Authenticate response header.
+// See RFC 2617.
+type Challenge struct {
+	// Scheme is the auth-scheme according to RFC 2617
+	Scheme string
+
+	// Parameters are the auth-params according to RFC 2617
+	Parameters map[string]string
+}
+
+// Manager manages the challenges for endpoints.
+// The challenges are pulled out of HTTP responses. Only
+// responses which expect challenges should be added to
+// the manager, since a non-unauthorized request will be
+// viewed as not requiring challenges.
+type Manager interface {
+	// GetChallenges returns the challenges for the given
+	// endpoint URL.
+	GetChallenges(endpoint url.URL) ([]Challenge, error)
+
+	// AddResponse adds the response to the challenge
+	// manager. The challenges will be parsed out of
+	// the WWW-Authenicate headers and added to the
+	// URL which was produced the response. If the
+	// response was authorized, any challenges for the
+	// endpoint will be cleared.
+	AddResponse(resp *http.Response) error
+}
+
+// NewSimpleManager returns an instance of
+// Manger which only maps endpoints to challenges
+// based on the responses which have been added the
+// manager. The simple manager will make no attempt to
+// perform requests on the endpoints or cache the responses
+// to a backend.
+func NewSimpleManager() Manager {
+	return &simpleManager{
+		Challenges: make(map[string][]Challenge),
+	}
+}
+
+type simpleManager struct {
+	sync.RWMutex
+	Challenges map[string][]Challenge
+}
+
+func normalizeURL(endpoint *url.URL) {
+	endpoint.Host = strings.ToLower(endpoint.Host)
+	endpoint.Host = canonicalAddr(endpoint)
+}
+
+func (m *simpleManager) GetChallenges(endpoint url.URL) ([]Challenge, error) {
+	normalizeURL(&endpoint)
+
+	m.RLock()
+	defer m.RUnlock()
+	challenges := m.Challenges[endpoint.String()]
+	return challenges, nil
+}
+
+func (m *simpleManager) AddResponse(resp *http.Response) error {
+	challenges := ResponseChallenges(resp)
+	if resp.Request == nil {
+		return fmt.Errorf("missing request reference")
+	}
+	urlCopy := url.URL{
+		Path:   resp.Request.URL.Path,
+		Host:   resp.Request.URL.Host,
+		Scheme: resp.Request.URL.Scheme,
+	}
+	normalizeURL(&urlCopy)
+
+	m.Lock()
+	defer m.Unlock()
+	m.Challenges[urlCopy.String()] = challenges
+	return nil
+}
+
+// Octet types from RFC 2616.
+type octetType byte
+
+var octetTypes [256]octetType
+
+const (
+	isToken octetType = 1 << iota
+	isSpace
+)
+
+func init() {
+	// OCTET      = <any 8-bit sequence of data>
+	// CHAR       = <any US-ASCII character (octets 0 - 127)>
+	// CTL        = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
+	// CR         = <US-ASCII CR, carriage return (13)>
+	// LF         = <US-ASCII LF, linefeed (10)>
+	// SP         = <US-ASCII SP, space (32)>
+	// HT         = <US-ASCII HT, horizontal-tab (9)>
+	// <">        = <US-ASCII double-quote mark (34)>
+	// CRLF       = CR LF
+	// LWS        = [CRLF] 1*( SP | HT )
+	// TEXT       = <any OCTET except CTLs, but including LWS>
+	// separators = "(" | ")" | "<" | ">" | "@" | "," | ";" | ":" | "\" | <">
+	//              | "/" | "[" | "]" | "?" | "=" | "{" | "}" | SP | HT
+	// token      = 1*<any CHAR except CTLs or separators>
+	// qdtext     = <any TEXT except <">>
+
+	for c := 0; c < 256; c++ {
+		var t octetType
+		isCtl := c <= 31 || c == 127
+		isChar := 0 <= c && c <= 127
+		isSeparator := strings.ContainsRune(" \t\"(),/:;<=>?@[]\\{}", rune(c))
+		if strings.ContainsRune(" \t\r\n", rune(c)) {
+			t |= isSpace
+		}
+		if isChar && !isCtl && !isSeparator {
+			t |= isToken
+		}
+		octetTypes[c] = t
+	}
+}
+
+// ResponseChallenges returns a list of authorization challenges
+// for the given http Response. Challenges are only checked if
+// the response status code was a 401.
+func ResponseChallenges(resp *http.Response) []Challenge {
+	if resp.StatusCode == http.StatusUnauthorized {
+		// Parse the WWW-Authenticate Header and store the challenges
+		// on this endpoint object.
+		return parseAuthHeader(resp.Header)
+	}
+
+	return nil
+}
+
+func parseAuthHeader(header http.Header) []Challenge {
+	challenges := []Challenge{}
+	for _, h := range header[http.CanonicalHeaderKey("WWW-Authenticate")] {
+		v, p := parseValueAndParams(h)
+		if v != "" {
+			challenges = append(challenges, Challenge{Scheme: v, Parameters: p})
+		}
+	}
+	return challenges
+}
+
+func parseValueAndParams(header string) (value string, params map[string]string) {
+	params = make(map[string]string)
+	value, s := expectToken(header)
+	if value == "" {
+		return
+	}
+	value = strings.ToLower(value)
+	s = "," + skipSpace(s)
+	for strings.HasPrefix(s, ",") {
+		var pkey string
+		pkey, s = expectToken(skipSpace(s[1:]))
+		if pkey == "" {
+			return
+		}
+		if !strings.HasPrefix(s, "=") {
+			return
+		}
+		var pvalue string
+		pvalue, s = expectTokenOrQuoted(s[1:])
+		if pvalue == "" {
+			return
+		}
+		pkey = strings.ToLower(pkey)
+		params[pkey] = pvalue
+		s = skipSpace(s)
+	}
+	return
+}
+
+func skipSpace(s string) (rest string) {
+	i := 0
+	for ; i < len(s); i++ {
+		if octetTypes[s[i]]&isSpace == 0 {
+			break
+		}
+	}
+	return s[i:]
+}
+
+func expectToken(s string) (token, rest string) {
+	i := 0
+	for ; i < len(s); i++ {
+		if octetTypes[s[i]]&isToken == 0 {
+			break
+		}
+	}
+	return s[:i], s[i:]
+}
+
+func expectTokenOrQuoted(s string) (value string, rest string) {
+	if !strings.HasPrefix(s, "\"") {
+		return expectToken(s)
+	}
+	s = s[1:]
+	for i := 0; i < len(s); i++ {
+		switch s[i] {
+		case '"':
+			return s[:i], s[i+1:]
+		case '\\':
+			p := make([]byte, len(s)-1)
+			j := copy(p, s[:i])
+			escape := true
+			for i = i + 1; i < len(s); i++ {
+				b := s[i]
+				switch {
+				case escape:
+					escape = false
+					p[j] = b
+					j++
+				case b == '\\':
+					escape = true
+				case b == '"':
+					return string(p[:j]), s[i+1:]
+				default:
+					p[j] = b
+					j++
+				}
+			}
+			return "", ""
+		}
+	}
+	return "", ""
+}

vendor/github.com/docker/distribution/registry/client/blob_writer.go

@@ -0,0 +1,162 @@
+package client
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"time"
+
+	"github.com/docker/distribution"
+)
+
+type httpBlobUpload struct {
+	statter distribution.BlobStatter
+	client  *http.Client
+
+	uuid      string
+	startedAt time.Time
+
+	location string // always the last value of the location header.
+	offset   int64
+	closed   bool
+}
+
+func (hbu *httpBlobUpload) Reader() (io.ReadCloser, error) {
+	panic("Not implemented")
+}
+
+func (hbu *httpBlobUpload) handleErrorResponse(resp *http.Response) error {
+	if resp.StatusCode == http.StatusNotFound {
+		return distribution.ErrBlobUploadUnknown
+	}
+	return HandleErrorResponse(resp)
+}
+
+func (hbu *httpBlobUpload) ReadFrom(r io.Reader) (n int64, err error) {
+	req, err := http.NewRequest("PATCH", hbu.location, ioutil.NopCloser(r))
+	if err != nil {
+		return 0, err
+	}
+	defer req.Body.Close()
+
+	resp, err := hbu.client.Do(req)
+	if err != nil {
+		return 0, err
+	}
+
+	if !SuccessStatus(resp.StatusCode) {
+		return 0, hbu.handleErrorResponse(resp)
+	}
+
+	hbu.uuid = resp.Header.Get("Docker-Upload-UUID")
+	hbu.location, err = sanitizeLocation(resp.Header.Get("Location"), hbu.location)
+	if err != nil {
+		return 0, err
+	}
+	rng := resp.Header.Get("Range")
+	var start, end int64
+	if n, err := fmt.Sscanf(rng, "%d-%d", &start, &end); err != nil {
+		return 0, err
+	} else if n != 2 || end < start {
+		return 0, fmt.Errorf("bad range format: %s", rng)
+	}
+
+	return (end - start + 1), nil
+
+}
+
+func (hbu *httpBlobUpload) Write(p []byte) (n int, err error) {
+	req, err := http.NewRequest("PATCH", hbu.location, bytes.NewReader(p))
+	if err != nil {
+		return 0, err
+	}
+	req.Header.Set("Content-Range", fmt.Sprintf("%d-%d", hbu.offset, hbu.offset+int64(len(p)-1)))
+	req.Header.Set("Content-Length", fmt.Sprintf("%d", len(p)))
+	req.Header.Set("Content-Type", "application/octet-stream")
+
+	resp, err := hbu.client.Do(req)
+	if err != nil {
+		return 0, err
+	}
+
+	if !SuccessStatus(resp.StatusCode) {
+		return 0, hbu.handleErrorResponse(resp)
+	}
+
+	hbu.uuid = resp.Header.Get("Docker-Upload-UUID")
+	hbu.location, err = sanitizeLocation(resp.Header.Get("Location"), hbu.location)
+	if err != nil {
+		return 0, err
+	}
+	rng := resp.Header.Get("Range")
+	var start, end int
+	if n, err := fmt.Sscanf(rng, "%d-%d", &start, &end); err != nil {
+		return 0, err
+	} else if n != 2 || end < start {
+		return 0, fmt.Errorf("bad range format: %s", rng)
+	}
+
+	return (end - start + 1), nil
+
+}
+
+func (hbu *httpBlobUpload) Size() int64 {
+	return hbu.offset
+}
+
+func (hbu *httpBlobUpload) ID() string {
+	return hbu.uuid
+}
+
+func (hbu *httpBlobUpload) StartedAt() time.Time {
+	return hbu.startedAt
+}
+
+func (hbu *httpBlobUpload) Commit(ctx context.Context, desc distribution.Descriptor) (distribution.Descriptor, error) {
+	// TODO(dmcgowan): Check if already finished, if so just fetch
+	req, err := http.NewRequest("PUT", hbu.location, nil)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+
+	values := req.URL.Query()
+	values.Set("digest", desc.Digest.String())
+	req.URL.RawQuery = values.Encode()
+
+	resp, err := hbu.client.Do(req)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+	defer resp.Body.Close()
+
+	if !SuccessStatus(resp.StatusCode) {
+		return distribution.Descriptor{}, hbu.handleErrorResponse(resp)
+	}
+
+	return hbu.statter.Stat(ctx, desc.Digest)
+}
+
+func (hbu *httpBlobUpload) Cancel(ctx context.Context) error {
+	req, err := http.NewRequest("DELETE", hbu.location, nil)
+	if err != nil {
+		return err
+	}
+	resp, err := hbu.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode == http.StatusNotFound || SuccessStatus(resp.StatusCode) {
+		return nil
+	}
+	return hbu.handleErrorResponse(resp)
+}
+
+func (hbu *httpBlobUpload) Close() error {
+	hbu.closed = true
+	return nil
+}

vendor/github.com/docker/distribution/registry/client/errors.go

@@ -0,0 +1,139 @@
+package client
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+
+	"github.com/docker/distribution/registry/api/errcode"
+	"github.com/docker/distribution/registry/client/auth/challenge"
+)
+
+// ErrNoErrorsInBody is returned when an HTTP response body parses to an empty
+// errcode.Errors slice.
+var ErrNoErrorsInBody = errors.New("no error details found in HTTP response body")
+
+// UnexpectedHTTPStatusError is returned when an unexpected HTTP status is
+// returned when making a registry api call.
+type UnexpectedHTTPStatusError struct {
+	Status string
+}
+
+func (e *UnexpectedHTTPStatusError) Error() string {
+	return fmt.Sprintf("received unexpected HTTP status: %s", e.Status)
+}
+
+// UnexpectedHTTPResponseError is returned when an expected HTTP status code
+// is returned, but the content was unexpected and failed to be parsed.
+type UnexpectedHTTPResponseError struct {
+	ParseErr   error
+	StatusCode int
+	Response   []byte
+}
+
+func (e *UnexpectedHTTPResponseError) Error() string {
+	return fmt.Sprintf("error parsing HTTP %d response body: %s: %q", e.StatusCode, e.ParseErr.Error(), string(e.Response))
+}
+
+func parseHTTPErrorResponse(statusCode int, r io.Reader) error {
+	var errors errcode.Errors
+	body, err := ioutil.ReadAll(r)
+	if err != nil {
+		return err
+	}
+
+	// For backward compatibility, handle irregularly formatted
+	// messages that contain a "details" field.
+	var detailsErr struct {
+		Details string `json:"details"`
+	}
+	err = json.Unmarshal(body, &detailsErr)
+	if err == nil && detailsErr.Details != "" {
+		switch statusCode {
+		case http.StatusUnauthorized:
+			return errcode.ErrorCodeUnauthorized.WithMessage(detailsErr.Details)
+		case http.StatusTooManyRequests:
+			return errcode.ErrorCodeTooManyRequests.WithMessage(detailsErr.Details)
+		default:
+			return errcode.ErrorCodeUnknown.WithMessage(detailsErr.Details)
+		}
+	}
+
+	if err := json.Unmarshal(body, &errors); err != nil {
+		return &UnexpectedHTTPResponseError{
+			ParseErr:   err,
+			StatusCode: statusCode,
+			Response:   body,
+		}
+	}
+
+	if len(errors) == 0 {
+		// If there was no error specified in the body, return
+		// UnexpectedHTTPResponseError.
+		return &UnexpectedHTTPResponseError{
+			ParseErr:   ErrNoErrorsInBody,
+			StatusCode: statusCode,
+			Response:   body,
+		}
+	}
+
+	return errors
+}
+
+func makeErrorList(err error) []error {
+	if errL, ok := err.(errcode.Errors); ok {
+		return []error(errL)
+	}
+	return []error{err}
+}
+
+func mergeErrors(err1, err2 error) error {
+	return errcode.Errors(append(makeErrorList(err1), makeErrorList(err2)...))
+}
+
+// HandleErrorResponse returns error parsed from HTTP response for an
+// unsuccessful HTTP response code (in the range 400 - 499 inclusive). An
+// UnexpectedHTTPStatusError returned for response code outside of expected
+// range.
+func HandleErrorResponse(resp *http.Response) error {
+	if resp.StatusCode >= 400 && resp.StatusCode < 500 {
+		// Check for OAuth errors within the `WWW-Authenticate` header first
+		// See https://tools.ietf.org/html/rfc6750#section-3
+		for _, c := range challenge.ResponseChallenges(resp) {
+			if c.Scheme == "bearer" {
+				var err errcode.Error
+				// codes defined at https://tools.ietf.org/html/rfc6750#section-3.1
+				switch c.Parameters["error"] {
+				case "invalid_token":
+					err.Code = errcode.ErrorCodeUnauthorized
+				case "insufficient_scope":
+					err.Code = errcode.ErrorCodeDenied
+				default:
+					continue
+				}
+				if description := c.Parameters["error_description"]; description != "" {
+					err.Message = description
+				} else {
+					err.Message = err.Code.Message()
+				}
+
+				return mergeErrors(err, parseHTTPErrorResponse(resp.StatusCode, resp.Body))
+			}
+		}
+		err := parseHTTPErrorResponse(resp.StatusCode, resp.Body)
+		if uErr, ok := err.(*UnexpectedHTTPResponseError); ok && resp.StatusCode == 401 {
+			return errcode.ErrorCodeUnauthorized.WithDetail(uErr.Response)
+		}
+		return err
+	}
+	return &UnexpectedHTTPStatusError{Status: resp.Status}
+}
+
+// SuccessStatus returns true if the argument is a successful HTTP response
+// code (in the range 200 - 399 inclusive).
+func SuccessStatus(status int) bool {
+	return status >= 200 && status <= 399
+}

vendor/github.com/docker/distribution/registry/client/repository.go

@@ -0,0 +1,872 @@
+package client
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/docker/distribution"
+	"github.com/docker/distribution/reference"
+	v2 "github.com/docker/distribution/registry/api/v2"
+	"github.com/docker/distribution/registry/client/transport"
+	"github.com/docker/distribution/registry/storage/cache"
+	"github.com/docker/distribution/registry/storage/cache/memory"
+	"github.com/opencontainers/go-digest"
+)
+
+// Registry provides an interface for calling Repositories, which returns a catalog of repositories.
+type Registry interface {
+	Repositories(ctx context.Context, repos []string, last string) (n int, err error)
+}
+
+// checkHTTPRedirect is a callback that can manipulate redirected HTTP
+// requests. It is used to preserve Accept and Range headers.
+func checkHTTPRedirect(req *http.Request, via []*http.Request) error {
+	if len(via) >= 10 {
+		return errors.New("stopped after 10 redirects")
+	}
+
+	if len(via) > 0 {
+		for headerName, headerVals := range via[0].Header {
+			if headerName != "Accept" && headerName != "Range" {
+				continue
+			}
+			for _, val := range headerVals {
+				// Don't add to redirected request if redirected
+				// request already has a header with the same
+				// name and value.
+				hasValue := false
+				for _, existingVal := range req.Header[headerName] {
+					if existingVal == val {
+						hasValue = true
+						break
+					}
+				}
+				if !hasValue {
+					req.Header.Add(headerName, val)
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
+// NewRegistry creates a registry namespace which can be used to get a listing of repositories
+func NewRegistry(baseURL string, transport http.RoundTripper) (Registry, error) {
+	ub, err := v2.NewURLBuilderFromString(baseURL, false)
+	if err != nil {
+		return nil, err
+	}
+
+	client := &http.Client{
+		Transport:     transport,
+		Timeout:       1 * time.Minute,
+		CheckRedirect: checkHTTPRedirect,
+	}
+
+	return &registry{
+		client: client,
+		ub:     ub,
+	}, nil
+}
+
+type registry struct {
+	client *http.Client
+	ub     *v2.URLBuilder
+}
+
+// Repositories returns a lexigraphically sorted catalog given a base URL.  The 'entries' slice will be filled up to the size
+// of the slice, starting at the value provided in 'last'.  The number of entries will be returned along with io.EOF if there
+// are no more entries
+func (r *registry) Repositories(ctx context.Context, entries []string, last string) (int, error) {
+	var numFilled int
+	var returnErr error
+
+	values := buildCatalogValues(len(entries), last)
+	u, err := r.ub.BuildCatalogURL(values)
+	if err != nil {
+		return 0, err
+	}
+
+	resp, err := r.client.Get(u)
+	if err != nil {
+		return 0, err
+	}
+	defer resp.Body.Close()
+
+	if SuccessStatus(resp.StatusCode) {
+		var ctlg struct {
+			Repositories []string `json:"repositories"`
+		}
+		decoder := json.NewDecoder(resp.Body)
+
+		if err := decoder.Decode(&ctlg); err != nil {
+			return 0, err
+		}
+
+		for cnt := range ctlg.Repositories {
+			entries[cnt] = ctlg.Repositories[cnt]
+		}
+		numFilled = len(ctlg.Repositories)
+
+		link := resp.Header.Get("Link")
+		if link == "" {
+			returnErr = io.EOF
+		}
+	} else {
+		return 0, HandleErrorResponse(resp)
+	}
+
+	return numFilled, returnErr
+}
+
+// NewRepository creates a new Repository for the given repository name and base URL.
+func NewRepository(name reference.Named, baseURL string, transport http.RoundTripper) (distribution.Repository, error) {
+	ub, err := v2.NewURLBuilderFromString(baseURL, false)
+	if err != nil {
+		return nil, err
+	}
+
+	client := &http.Client{
+		Transport:     transport,
+		CheckRedirect: checkHTTPRedirect,
+		// TODO(dmcgowan): create cookie jar
+	}
+
+	return &repository{
+		client: client,
+		ub:     ub,
+		name:   name,
+	}, nil
+}
+
+type repository struct {
+	client *http.Client
+	ub     *v2.URLBuilder
+	name   reference.Named
+}
+
+func (r *repository) Named() reference.Named {
+	return r.name
+}
+
+func (r *repository) Blobs(ctx context.Context) distribution.BlobStore {
+	statter := &blobStatter{
+		name:   r.name,
+		ub:     r.ub,
+		client: r.client,
+	}
+	return &blobs{
+		name:    r.name,
+		ub:      r.ub,
+		client:  r.client,
+		statter: cache.NewCachedBlobStatter(memory.NewInMemoryBlobDescriptorCacheProvider(), statter),
+	}
+}
+
+func (r *repository) Manifests(ctx context.Context, options ...distribution.ManifestServiceOption) (distribution.ManifestService, error) {
+	// todo(richardscothern): options should be sent over the wire
+	return &manifests{
+		name:   r.name,
+		ub:     r.ub,
+		client: r.client,
+		etags:  make(map[string]string),
+	}, nil
+}
+
+func (r *repository) Tags(ctx context.Context) distribution.TagService {
+	return &tags{
+		client: r.client,
+		ub:     r.ub,
+		name:   r.Named(),
+	}
+}
+
+// tags implements remote tagging operations.
+type tags struct {
+	client *http.Client
+	ub     *v2.URLBuilder
+	name   reference.Named
+}
+
+// All returns all tags
+func (t *tags) All(ctx context.Context) ([]string, error) {
+	var tags []string
+
+	listURLStr, err := t.ub.BuildTagsURL(t.name)
+	if err != nil {
+		return tags, err
+	}
+
+	listURL, err := url.Parse(listURLStr)
+	if err != nil {
+		return tags, err
+	}
+
+	for {
+		resp, err := t.client.Get(listURL.String())
+		if err != nil {
+			return tags, err
+		}
+		defer resp.Body.Close()
+
+		if SuccessStatus(resp.StatusCode) {
+			b, err := ioutil.ReadAll(resp.Body)
+			if err != nil {
+				return tags, err
+			}
+
+			tagsResponse := struct {
+				Tags []string `json:"tags"`
+			}{}
+			if err := json.Unmarshal(b, &tagsResponse); err != nil {
+				return tags, err
+			}
+			tags = append(tags, tagsResponse.Tags...)
+			if link := resp.Header.Get("Link"); link != "" {
+				linkURLStr := strings.Trim(strings.Split(link, ";")[0], "<>")
+				linkURL, err := url.Parse(linkURLStr)
+				if err != nil {
+					return tags, err
+				}
+
+				listURL = listURL.ResolveReference(linkURL)
+			} else {
+				return tags, nil
+			}
+		} else {
+			return tags, HandleErrorResponse(resp)
+		}
+	}
+}
+
+func descriptorFromResponse(response *http.Response) (distribution.Descriptor, error) {
+	desc := distribution.Descriptor{}
+	headers := response.Header
+
+	ctHeader := headers.Get("Content-Type")
+	if ctHeader == "" {
+		return distribution.Descriptor{}, errors.New("missing or empty Content-Type header")
+	}
+	desc.MediaType = ctHeader
+
+	digestHeader := headers.Get("Docker-Content-Digest")
+	if digestHeader == "" {
+		bytes, err := ioutil.ReadAll(response.Body)
+		if err != nil {
+			return distribution.Descriptor{}, err
+		}
+		_, desc, err := distribution.UnmarshalManifest(ctHeader, bytes)
+		if err != nil {
+			return distribution.Descriptor{}, err
+		}
+		return desc, nil
+	}
+
+	dgst, err := digest.Parse(digestHeader)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+	desc.Digest = dgst
+
+	lengthHeader := headers.Get("Content-Length")
+	if lengthHeader == "" {
+		return distribution.Descriptor{}, errors.New("missing or empty Content-Length header")
+	}
+	length, err := strconv.ParseInt(lengthHeader, 10, 64)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+	desc.Size = length
+
+	return desc, nil
+
+}
+
+// Get issues a HEAD request for a Manifest against its named endpoint in order
+// to construct a descriptor for the tag.  If the registry doesn't support HEADing
+// a manifest, fallback to GET.
+func (t *tags) Get(ctx context.Context, tag string) (distribution.Descriptor, error) {
+	ref, err := reference.WithTag(t.name, tag)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+	u, err := t.ub.BuildManifestURL(ref)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+
+	newRequest := func(method string) (*http.Response, error) {
+		req, err := http.NewRequest(method, u, nil)
+		if err != nil {
+			return nil, err
+		}
+
+		for _, t := range distribution.ManifestMediaTypes() {
+			req.Header.Add("Accept", t)
+		}
+		resp, err := t.client.Do(req)
+		return resp, err
+	}
+
+	resp, err := newRequest("HEAD")
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+	defer resp.Body.Close()
+
+	switch {
+	case resp.StatusCode >= 200 && resp.StatusCode < 400 && len(resp.Header.Get("Docker-Content-Digest")) > 0:
+		// if the response is a success AND a Docker-Content-Digest can be retrieved from the headers
+		return descriptorFromResponse(resp)
+	default:
+		// if the response is an error - there will be no body to decode.
+		// Issue a GET request:
+		//   - for data from a server that does not handle HEAD
+		//   - to get error details in case of a failure
+		resp, err = newRequest("GET")
+		if err != nil {
+			return distribution.Descriptor{}, err
+		}
+		defer resp.Body.Close()
+
+		if resp.StatusCode >= 200 && resp.StatusCode < 400 {
+			return descriptorFromResponse(resp)
+		}
+		return distribution.Descriptor{}, HandleErrorResponse(resp)
+	}
+}
+
+func (t *tags) Lookup(ctx context.Context, digest distribution.Descriptor) ([]string, error) {
+	panic("not implemented")
+}
+
+func (t *tags) Tag(ctx context.Context, tag string, desc distribution.Descriptor) error {
+	panic("not implemented")
+}
+
+func (t *tags) Untag(ctx context.Context, tag string) error {
+	panic("not implemented")
+}
+
+type manifests struct {
+	name   reference.Named
+	ub     *v2.URLBuilder
+	client *http.Client
+	etags  map[string]string
+}
+
+func (ms *manifests) Exists(ctx context.Context, dgst digest.Digest) (bool, error) {
+	ref, err := reference.WithDigest(ms.name, dgst)
+	if err != nil {
+		return false, err
+	}
+	u, err := ms.ub.BuildManifestURL(ref)
+	if err != nil {
+		return false, err
+	}
+
+	resp, err := ms.client.Head(u)
+	if err != nil {
+		return false, err
+	}
+
+	if SuccessStatus(resp.StatusCode) {
+		return true, nil
+	} else if resp.StatusCode == http.StatusNotFound {
+		return false, nil
+	}
+	return false, HandleErrorResponse(resp)
+}
+
+// AddEtagToTag allows a client to supply an eTag to Get which will be
+// used for a conditional HTTP request.  If the eTag matches, a nil manifest
+// and ErrManifestNotModified error will be returned. etag is automatically
+// quoted when added to this map.
+func AddEtagToTag(tag, etag string) distribution.ManifestServiceOption {
+	return etagOption{tag, etag}
+}
+
+type etagOption struct{ tag, etag string }
+
+func (o etagOption) Apply(ms distribution.ManifestService) error {
+	if ms, ok := ms.(*manifests); ok {
+		ms.etags[o.tag] = fmt.Sprintf(`"%s"`, o.etag)
+		return nil
+	}
+	return fmt.Errorf("etag options is a client-only option")
+}
+
+// ReturnContentDigest allows a client to set a the content digest on
+// a successful request from the 'Docker-Content-Digest' header. This
+// returned digest is represents the digest which the registry uses
+// to refer to the content and can be used to delete the content.
+func ReturnContentDigest(dgst *digest.Digest) distribution.ManifestServiceOption {
+	return contentDigestOption{dgst}
+}
+
+type contentDigestOption struct{ digest *digest.Digest }
+
+func (o contentDigestOption) Apply(ms distribution.ManifestService) error {
+	return nil
+}
+
+func (ms *manifests) Get(ctx context.Context, dgst digest.Digest, options ...distribution.ManifestServiceOption) (distribution.Manifest, error) {
+	var (
+		digestOrTag string
+		ref         reference.Named
+		err         error
+		contentDgst *digest.Digest
+		mediaTypes  []string
+	)
+
+	for _, option := range options {
+		switch opt := option.(type) {
+		case distribution.WithTagOption:
+			digestOrTag = opt.Tag
+			ref, err = reference.WithTag(ms.name, opt.Tag)
+			if err != nil {
+				return nil, err
+			}
+		case contentDigestOption:
+			contentDgst = opt.digest
+		case distribution.WithManifestMediaTypesOption:
+			mediaTypes = opt.MediaTypes
+		default:
+			err := option.Apply(ms)
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	if digestOrTag == "" {
+		digestOrTag = dgst.String()
+		ref, err = reference.WithDigest(ms.name, dgst)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if len(mediaTypes) == 0 {
+		mediaTypes = distribution.ManifestMediaTypes()
+	}
+
+	u, err := ms.ub.BuildManifestURL(ref)
+	if err != nil {
+		return nil, err
+	}
+
+	req, err := http.NewRequest("GET", u, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, t := range mediaTypes {
+		req.Header.Add("Accept", t)
+	}
+
+	if _, ok := ms.etags[digestOrTag]; ok {
+		req.Header.Set("If-None-Match", ms.etags[digestOrTag])
+	}
+
+	resp, err := ms.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode == http.StatusNotModified {
+		return nil, distribution.ErrManifestNotModified
+	} else if SuccessStatus(resp.StatusCode) {
+		if contentDgst != nil {
+			dgst, err := digest.Parse(resp.Header.Get("Docker-Content-Digest"))
+			if err == nil {
+				*contentDgst = dgst
+			}
+		}
+		mt := resp.Header.Get("Content-Type")
+		body, err := ioutil.ReadAll(resp.Body)
+
+		if err != nil {
+			return nil, err
+		}
+		m, _, err := distribution.UnmarshalManifest(mt, body)
+		if err != nil {
+			return nil, err
+		}
+		return m, nil
+	}
+	return nil, HandleErrorResponse(resp)
+}
+
+// Put puts a manifest.  A tag can be specified using an options parameter which uses some shared state to hold the
+// tag name in order to build the correct upload URL.
+func (ms *manifests) Put(ctx context.Context, m distribution.Manifest, options ...distribution.ManifestServiceOption) (digest.Digest, error) {
+	ref := ms.name
+	var tagged bool
+
+	for _, option := range options {
+		if opt, ok := option.(distribution.WithTagOption); ok {
+			var err error
+			ref, err = reference.WithTag(ref, opt.Tag)
+			if err != nil {
+				return "", err
+			}
+			tagged = true
+		} else {
+			err := option.Apply(ms)
+			if err != nil {
+				return "", err
+			}
+		}
+	}
+	mediaType, p, err := m.Payload()
+	if err != nil {
+		return "", err
+	}
+
+	if !tagged {
+		// generate a canonical digest and Put by digest
+		_, d, err := distribution.UnmarshalManifest(mediaType, p)
+		if err != nil {
+			return "", err
+		}
+		ref, err = reference.WithDigest(ref, d.Digest)
+		if err != nil {
+			return "", err
+		}
+	}
+
+	manifestURL, err := ms.ub.BuildManifestURL(ref)
+	if err != nil {
+		return "", err
+	}
+
+	putRequest, err := http.NewRequest("PUT", manifestURL, bytes.NewReader(p))
+	if err != nil {
+		return "", err
+	}
+
+	putRequest.Header.Set("Content-Type", mediaType)
+
+	resp, err := ms.client.Do(putRequest)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	if SuccessStatus(resp.StatusCode) {
+		dgstHeader := resp.Header.Get("Docker-Content-Digest")
+		dgst, err := digest.Parse(dgstHeader)
+		if err != nil {
+			return "", err
+		}
+
+		return dgst, nil
+	}
+
+	return "", HandleErrorResponse(resp)
+}
+
+func (ms *manifests) Delete(ctx context.Context, dgst digest.Digest) error {
+	ref, err := reference.WithDigest(ms.name, dgst)
+	if err != nil {
+		return err
+	}
+	u, err := ms.ub.BuildManifestURL(ref)
+	if err != nil {
+		return err
+	}
+	req, err := http.NewRequest("DELETE", u, nil)
+	if err != nil {
+		return err
+	}
+
+	resp, err := ms.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if SuccessStatus(resp.StatusCode) {
+		return nil
+	}
+	return HandleErrorResponse(resp)
+}
+
+// todo(richardscothern): Restore interface and implementation with merge of #1050
+/*func (ms *manifests) Enumerate(ctx context.Context, manifests []distribution.Manifest, last distribution.Manifest) (n int, err error) {
+	panic("not supported")
+}*/
+
+type blobs struct {
+	name   reference.Named
+	ub     *v2.URLBuilder
+	client *http.Client
+
+	statter distribution.BlobDescriptorService
+	distribution.BlobDeleter
+}
+
+func sanitizeLocation(location, base string) (string, error) {
+	baseURL, err := url.Parse(base)
+	if err != nil {
+		return "", err
+	}
+
+	locationURL, err := url.Parse(location)
+	if err != nil {
+		return "", err
+	}
+
+	return baseURL.ResolveReference(locationURL).String(), nil
+}
+
+func (bs *blobs) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
+	return bs.statter.Stat(ctx, dgst)
+
+}
+
+func (bs *blobs) Get(ctx context.Context, dgst digest.Digest) ([]byte, error) {
+	reader, err := bs.Open(ctx, dgst)
+	if err != nil {
+		return nil, err
+	}
+	defer reader.Close()
+
+	return ioutil.ReadAll(reader)
+}
+
+func (bs *blobs) Open(ctx context.Context, dgst digest.Digest) (distribution.ReadSeekCloser, error) {
+	ref, err := reference.WithDigest(bs.name, dgst)
+	if err != nil {
+		return nil, err
+	}
+	blobURL, err := bs.ub.BuildBlobURL(ref)
+	if err != nil {
+		return nil, err
+	}
+
+	return transport.NewHTTPReadSeeker(bs.client, blobURL,
+		func(resp *http.Response) error {
+			if resp.StatusCode == http.StatusNotFound {
+				return distribution.ErrBlobUnknown
+			}
+			return HandleErrorResponse(resp)
+		}), nil
+}
+
+func (bs *blobs) ServeBlob(ctx context.Context, w http.ResponseWriter, r *http.Request, dgst digest.Digest) error {
+	panic("not implemented")
+}
+
+func (bs *blobs) Put(ctx context.Context, mediaType string, p []byte) (distribution.Descriptor, error) {
+	writer, err := bs.Create(ctx)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+	dgstr := digest.Canonical.Digester()
+	n, err := io.Copy(writer, io.TeeReader(bytes.NewReader(p), dgstr.Hash()))
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+	if n < int64(len(p)) {
+		return distribution.Descriptor{}, fmt.Errorf("short copy: wrote %d of %d", n, len(p))
+	}
+
+	desc := distribution.Descriptor{
+		MediaType: mediaType,
+		Size:      int64(len(p)),
+		Digest:    dgstr.Digest(),
+	}
+
+	return writer.Commit(ctx, desc)
+}
+
+type optionFunc func(interface{}) error
+
+func (f optionFunc) Apply(v interface{}) error {
+	return f(v)
+}
+
+// WithMountFrom returns a BlobCreateOption which designates that the blob should be
+// mounted from the given canonical reference.
+func WithMountFrom(ref reference.Canonical) distribution.BlobCreateOption {
+	return optionFunc(func(v interface{}) error {
+		opts, ok := v.(*distribution.CreateOptions)
+		if !ok {
+			return fmt.Errorf("unexpected options type: %T", v)
+		}
+
+		opts.Mount.ShouldMount = true
+		opts.Mount.From = ref
+
+		return nil
+	})
+}
+
+func (bs *blobs) Create(ctx context.Context, options ...distribution.BlobCreateOption) (distribution.BlobWriter, error) {
+	var opts distribution.CreateOptions
+
+	for _, option := range options {
+		err := option.Apply(&opts)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	var values []url.Values
+
+	if opts.Mount.ShouldMount {
+		values = append(values, url.Values{"from": {opts.Mount.From.Name()}, "mount": {opts.Mount.From.Digest().String()}})
+	}
+
+	u, err := bs.ub.BuildBlobUploadURL(bs.name, values...)
+	if err != nil {
+		return nil, err
+	}
+
+	req, err := http.NewRequest("POST", u, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	resp, err := bs.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	switch resp.StatusCode {
+	case http.StatusCreated:
+		desc, err := bs.statter.Stat(ctx, opts.Mount.From.Digest())
+		if err != nil {
+			return nil, err
+		}
+		return nil, distribution.ErrBlobMounted{From: opts.Mount.From, Descriptor: desc}
+	case http.StatusAccepted:
+		// TODO(dmcgowan): Check for invalid UUID
+		uuid := resp.Header.Get("Docker-Upload-UUID")
+		location, err := sanitizeLocation(resp.Header.Get("Location"), u)
+		if err != nil {
+			return nil, err
+		}
+
+		return &httpBlobUpload{
+			statter:   bs.statter,
+			client:    bs.client,
+			uuid:      uuid,
+			startedAt: time.Now(),
+			location:  location,
+		}, nil
+	default:
+		return nil, HandleErrorResponse(resp)
+	}
+}
+
+func (bs *blobs) Resume(ctx context.Context, id string) (distribution.BlobWriter, error) {
+	panic("not implemented")
+}
+
+func (bs *blobs) Delete(ctx context.Context, dgst digest.Digest) error {
+	return bs.statter.Clear(ctx, dgst)
+}
+
+type blobStatter struct {
+	name   reference.Named
+	ub     *v2.URLBuilder
+	client *http.Client
+}
+
+func (bs *blobStatter) Stat(ctx context.Context, dgst digest.Digest) (distribution.Descriptor, error) {
+	ref, err := reference.WithDigest(bs.name, dgst)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+	u, err := bs.ub.BuildBlobURL(ref)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+
+	resp, err := bs.client.Head(u)
+	if err != nil {
+		return distribution.Descriptor{}, err
+	}
+	defer resp.Body.Close()
+
+	if SuccessStatus(resp.StatusCode) {
+		lengthHeader := resp.Header.Get("Content-Length")
+		if lengthHeader == "" {
+			return distribution.Descriptor{}, fmt.Errorf("missing content-length header for request: %s", u)
+		}
+
+		length, err := strconv.ParseInt(lengthHeader, 10, 64)
+		if err != nil {
+			return distribution.Descriptor{}, fmt.Errorf("error parsing content-length: %v", err)
+		}
+
+		return distribution.Descriptor{
+			MediaType: resp.Header.Get("Content-Type"),
+			Size:      length,
+			Digest:    dgst,
+		}, nil
+	} else if resp.StatusCode == http.StatusNotFound {
+		return distribution.Descriptor{}, distribution.ErrBlobUnknown
+	}
+	return distribution.Descriptor{}, HandleErrorResponse(resp)
+}
+
+func buildCatalogValues(maxEntries int, last string) url.Values {
+	values := url.Values{}
+
+	if maxEntries > 0 {
+		values.Add("n", strconv.Itoa(maxEntries))
+	}
+
+	if last != "" {
+		values.Add("last", last)
+	}
+
+	return values
+}
+
+func (bs *blobStatter) Clear(ctx context.Context, dgst digest.Digest) error {
+	ref, err := reference.WithDigest(bs.name, dgst)
+	if err != nil {
+		return err
+	}
+	blobURL, err := bs.ub.BuildBlobURL(ref)
+	if err != nil {
+		return err
+	}
+
+	req, err := http.NewRequest("DELETE", blobURL, nil)
+	if err != nil {
+		return err
+	}
+
+	resp, err := bs.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if SuccessStatus(resp.StatusCode) {
+		return nil
+	}
+	return HandleErrorResponse(resp)
+}
+
+func (bs *blobStatter) SetDescriptor(ctx context.Context, dgst digest.Digest, desc distribution.Descriptor) error {
+	return nil
+}

vendor/github.com/docker/distribution/registry/client/transport/http_reader.go

@@ -0,0 +1,250 @@
+package transport
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"regexp"
+	"strconv"
+)
+
+var (
+	contentRangeRegexp = regexp.MustCompile(`bytes ([0-9]+)-([0-9]+)/([0-9]+|\\*)`)
+
+	// ErrWrongCodeForByteRange is returned if the client sends a request
+	// with a Range header but the server returns a 2xx or 3xx code other
+	// than 206 Partial Content.
+	ErrWrongCodeForByteRange = errors.New("expected HTTP 206 from byte range request")
+)
+
+// ReadSeekCloser combines io.ReadSeeker with io.Closer.
+type ReadSeekCloser interface {
+	io.ReadSeeker
+	io.Closer
+}
+
+// NewHTTPReadSeeker handles reading from an HTTP endpoint using a GET
+// request. When seeking and starting a read from a non-zero offset
+// the a "Range" header will be added which sets the offset.
+// TODO(dmcgowan): Move this into a separate utility package
+func NewHTTPReadSeeker(client *http.Client, url string, errorHandler func(*http.Response) error) ReadSeekCloser {
+	return &httpReadSeeker{
+		client:       client,
+		url:          url,
+		errorHandler: errorHandler,
+	}
+}
+
+type httpReadSeeker struct {
+	client *http.Client
+	url    string
+
+	// errorHandler creates an error from an unsuccessful HTTP response.
+	// This allows the error to be created with the HTTP response body
+	// without leaking the body through a returned error.
+	errorHandler func(*http.Response) error
+
+	size int64
+
+	// rc is the remote read closer.
+	rc io.ReadCloser
+	// readerOffset tracks the offset as of the last read.
+	readerOffset int64
+	// seekOffset allows Seek to override the offset. Seek changes
+	// seekOffset instead of changing readOffset directly so that
+	// connection resets can be delayed and possibly avoided if the
+	// seek is undone (i.e. seeking to the end and then back to the
+	// beginning).
+	seekOffset int64
+	err        error
+}
+
+func (hrs *httpReadSeeker) Read(p []byte) (n int, err error) {
+	if hrs.err != nil {
+		return 0, hrs.err
+	}
+
+	// If we sought to a different position, we need to reset the
+	// connection. This logic is here instead of Seek so that if
+	// a seek is undone before the next read, the connection doesn't
+	// need to be closed and reopened. A common example of this is
+	// seeking to the end to determine the length, and then seeking
+	// back to the original position.
+	if hrs.readerOffset != hrs.seekOffset {
+		hrs.reset()
+	}
+
+	hrs.readerOffset = hrs.seekOffset
+
+	rd, err := hrs.reader()
+	if err != nil {
+		return 0, err
+	}
+
+	n, err = rd.Read(p)
+	hrs.seekOffset += int64(n)
+	hrs.readerOffset += int64(n)
+
+	return n, err
+}
+
+func (hrs *httpReadSeeker) Seek(offset int64, whence int) (int64, error) {
+	if hrs.err != nil {
+		return 0, hrs.err
+	}
+
+	lastReaderOffset := hrs.readerOffset
+
+	if whence == io.SeekStart && hrs.rc == nil {
+		// If no request has been made yet, and we are seeking to an
+		// absolute position, set the read offset as well to avoid an
+		// unnecessary request.
+		hrs.readerOffset = offset
+	}
+
+	_, err := hrs.reader()
+	if err != nil {
+		hrs.readerOffset = lastReaderOffset
+		return 0, err
+	}
+
+	newOffset := hrs.seekOffset
+
+	switch whence {
+	case io.SeekCurrent:
+		newOffset += offset
+	case io.SeekEnd:
+		if hrs.size < 0 {
+			return 0, errors.New("content length not known")
+		}
+		newOffset = hrs.size + offset
+	case io.SeekStart:
+		newOffset = offset
+	}
+
+	if newOffset < 0 {
+		err = errors.New("cannot seek to negative position")
+	} else {
+		hrs.seekOffset = newOffset
+	}
+
+	return hrs.seekOffset, err
+}
+
+func (hrs *httpReadSeeker) Close() error {
+	if hrs.err != nil {
+		return hrs.err
+	}
+
+	// close and release reader chain
+	if hrs.rc != nil {
+		hrs.rc.Close()
+	}
+
+	hrs.rc = nil
+
+	hrs.err = errors.New("httpLayer: closed")
+
+	return nil
+}
+
+func (hrs *httpReadSeeker) reset() {
+	if hrs.err != nil {
+		return
+	}
+	if hrs.rc != nil {
+		hrs.rc.Close()
+		hrs.rc = nil
+	}
+}
+
+func (hrs *httpReadSeeker) reader() (io.Reader, error) {
+	if hrs.err != nil {
+		return nil, hrs.err
+	}
+
+	if hrs.rc != nil {
+		return hrs.rc, nil
+	}
+
+	req, err := http.NewRequest("GET", hrs.url, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	if hrs.readerOffset > 0 {
+		// If we are at different offset, issue a range request from there.
+		req.Header.Add("Range", fmt.Sprintf("bytes=%d-", hrs.readerOffset))
+		// TODO: get context in here
+		// context.GetLogger(hrs.context).Infof("Range: %s", req.Header.Get("Range"))
+	}
+
+	req.Header.Add("Accept-Encoding", "identity")
+	resp, err := hrs.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+
+	// Normally would use client.SuccessStatus, but that would be a cyclic
+	// import
+	if resp.StatusCode >= 200 && resp.StatusCode <= 399 {
+		if hrs.readerOffset > 0 {
+			if resp.StatusCode != http.StatusPartialContent {
+				return nil, ErrWrongCodeForByteRange
+			}
+
+			contentRange := resp.Header.Get("Content-Range")
+			if contentRange == "" {
+				return nil, errors.New("no Content-Range header found in HTTP 206 response")
+			}
+
+			submatches := contentRangeRegexp.FindStringSubmatch(contentRange)
+			if len(submatches) < 4 {
+				return nil, fmt.Errorf("could not parse Content-Range header: %s", contentRange)
+			}
+
+			startByte, err := strconv.ParseUint(submatches[1], 10, 64)
+			if err != nil {
+				return nil, fmt.Errorf("could not parse start of range in Content-Range header: %s", contentRange)
+			}
+
+			if startByte != uint64(hrs.readerOffset) {
+				return nil, fmt.Errorf("received Content-Range starting at offset %d instead of requested %d", startByte, hrs.readerOffset)
+			}
+
+			endByte, err := strconv.ParseUint(submatches[2], 10, 64)
+			if err != nil {
+				return nil, fmt.Errorf("could not parse end of range in Content-Range header: %s", contentRange)
+			}
+
+			if submatches[3] == "*" {
+				hrs.size = -1
+			} else {
+				size, err := strconv.ParseUint(submatches[3], 10, 64)
+				if err != nil {
+					return nil, fmt.Errorf("could not parse total size in Content-Range header: %s", contentRange)
+				}
+
+				if endByte+1 != size {
+					return nil, fmt.Errorf("range in Content-Range stops before the end of the content: %s", contentRange)
+				}
+
+				hrs.size = int64(size)
+			}
+		} else if resp.StatusCode == http.StatusOK {
+			hrs.size = resp.ContentLength
+		} else {
+			hrs.size = -1
+		}
+		hrs.rc = resp.Body
+	} else {
+		defer resp.Body.Close()
+		if hrs.errorHandler != nil {
+			return nil, hrs.errorHandler(resp)
+		}
+		return nil, fmt.Errorf("unexpected status resolving reader: %v", resp.Status)
+	}
+
+	return hrs.rc, nil
+}

vendor/github.com/docker/distribution/registry/client/transport/transport.go

@@ -0,0 +1,147 @@
+package transport
+
+import (
+	"io"
+	"net/http"
+	"sync"
+)
+
+// RequestModifier represents an object which will do an inplace
+// modification of an HTTP request.
+type RequestModifier interface {
+	ModifyRequest(*http.Request) error
+}
+
+type headerModifier http.Header
+
+// NewHeaderRequestModifier returns a new RequestModifier which will
+// add the given headers to a request.
+func NewHeaderRequestModifier(header http.Header) RequestModifier {
+	return headerModifier(header)
+}
+
+func (h headerModifier) ModifyRequest(req *http.Request) error {
+	for k, s := range http.Header(h) {
+		req.Header[k] = append(req.Header[k], s...)
+	}
+
+	return nil
+}
+
+// NewTransport creates a new transport which will apply modifiers to
+// the request on a RoundTrip call.
+func NewTransport(base http.RoundTripper, modifiers ...RequestModifier) http.RoundTripper {
+	return &transport{
+		Modifiers: modifiers,
+		Base:      base,
+	}
+}
+
+// transport is an http.RoundTripper that makes HTTP requests after
+// copying and modifying the request
+type transport struct {
+	Modifiers []RequestModifier
+	Base      http.RoundTripper
+
+	mu     sync.Mutex                      // guards modReq
+	modReq map[*http.Request]*http.Request // original -> modified
+}
+
+// RoundTrip authorizes and authenticates the request with an
+// access token. If no token exists or token is expired,
+// tries to refresh/fetch a new token.
+func (t *transport) RoundTrip(req *http.Request) (*http.Response, error) {
+	req2 := cloneRequest(req)
+	for _, modifier := range t.Modifiers {
+		if err := modifier.ModifyRequest(req2); err != nil {
+			return nil, err
+		}
+	}
+
+	t.setModReq(req, req2)
+	res, err := t.base().RoundTrip(req2)
+	if err != nil {
+		t.setModReq(req, nil)
+		return nil, err
+	}
+	res.Body = &onEOFReader{
+		rc: res.Body,
+		fn: func() { t.setModReq(req, nil) },
+	}
+	return res, nil
+}
+
+// CancelRequest cancels an in-flight request by closing its connection.
+func (t *transport) CancelRequest(req *http.Request) {
+	type canceler interface {
+		CancelRequest(*http.Request)
+	}
+	if cr, ok := t.base().(canceler); ok {
+		t.mu.Lock()
+		modReq := t.modReq[req]
+		delete(t.modReq, req)
+		t.mu.Unlock()
+		cr.CancelRequest(modReq)
+	}
+}
+
+func (t *transport) base() http.RoundTripper {
+	if t.Base != nil {
+		return t.Base
+	}
+	return http.DefaultTransport
+}
+
+func (t *transport) setModReq(orig, mod *http.Request) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	if t.modReq == nil {
+		t.modReq = make(map[*http.Request]*http.Request)
+	}
+	if mod == nil {
+		delete(t.modReq, orig)
+	} else {
+		t.modReq[orig] = mod
+	}
+}
+
+// cloneRequest returns a clone of the provided *http.Request.
+// The clone is a shallow copy of the struct and its Header map.
+func cloneRequest(r *http.Request) *http.Request {
+	// shallow copy of the struct
+	r2 := new(http.Request)
+	*r2 = *r
+	// deep copy of the Header
+	r2.Header = make(http.Header, len(r.Header))
+	for k, s := range r.Header {
+		r2.Header[k] = append([]string(nil), s...)
+	}
+
+	return r2
+}
+
+type onEOFReader struct {
+	rc io.ReadCloser
+	fn func()
+}
+
+func (r *onEOFReader) Read(p []byte) (n int, err error) {
+	n, err = r.rc.Read(p)
+	if err == io.EOF {
+		r.runFunc()
+	}
+	return
+}
+
+func (r *onEOFReader) Close() error {
+	err := r.rc.Close()
+	r.runFunc()
+	return err
+}
+
+func (r *onEOFReader) runFunc() {
+	if fn := r.fn; fn != nil {
+		fn()
+		r.fn = nil
+	}
+}