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resolver.go
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resolver.go
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package docker
import (
"context"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"path"
"strconv"
"strings"
"time"
"github.com/containerd/containerd/images"
"github.com/containerd/containerd/log"
"github.com/containerd/containerd/reference"
"github.com/containerd/containerd/remotes"
digest "github.com/opencontainers/go-digest"
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"golang.org/x/net/context/ctxhttp"
)
var (
// ErrNoToken is returned if a request is successful but the body does not
// contain an authorization token.
ErrNoToken = errors.New("authorization server did not include a token in the response")
// ErrInvalidAuthorization is used when credentials are passed to a server but
// those credentials are rejected.
ErrInvalidAuthorization = errors.New("authorization failed")
)
type dockerResolver struct {
credentials func(string) (string, string, error)
plainHTTP bool
client *http.Client
tracker StatusTracker
}
// ResolverOptions are used to configured a new Docker register resolver
type ResolverOptions struct {
// Credentials provides username and secret given a host.
// If username is empty but a secret is given, that secret
// is interpretted as a long lived token.
Credentials func(string) (string, string, error)
// PlainHTTP specifies to use plain http and not https
PlainHTTP bool
// Client is the http client to used when making registry requests
Client *http.Client
// Tracker is used to track uploads to the registry. This is used
// since the registry does not have upload tracking and the existing
// mechanism for getting blob upload status is expensive.
Tracker StatusTracker
}
// NewResolver returns a new resolver to a Docker registry
func NewResolver(options ResolverOptions) remotes.Resolver {
tracker := options.Tracker
if tracker == nil {
tracker = NewInMemoryTracker()
}
return &dockerResolver{
credentials: options.Credentials,
plainHTTP: options.PlainHTTP,
client: options.Client,
tracker: tracker,
}
}
var _ remotes.Resolver = &dockerResolver{}
func (r *dockerResolver) Resolve(ctx context.Context, ref string) (string, ocispec.Descriptor, error) {
refspec, err := reference.Parse(ref)
if err != nil {
return "", ocispec.Descriptor{}, err
}
if refspec.Object == "" {
return "", ocispec.Descriptor{}, reference.ErrObjectRequired
}
base, err := r.base(refspec)
if err != nil {
return "", ocispec.Descriptor{}, err
}
fetcher := dockerFetcher{
dockerBase: base,
}
var (
urls []string
dgst = refspec.Digest()
)
if dgst != "" {
if err := dgst.Validate(); err != nil {
// need to fail here, since we can't actually resolve the invalid
// digest.
return "", ocispec.Descriptor{}, err
}
// turns out, we have a valid digest, make a url.
urls = append(urls, fetcher.url("manifests", dgst.String()))
// fallback to blobs on not found.
urls = append(urls, fetcher.url("blobs", dgst.String()))
} else {
urls = append(urls, fetcher.url("manifests", refspec.Object))
}
ctx, err = contextWithRepositoryScope(ctx, refspec, false)
if err != nil {
return "", ocispec.Descriptor{}, err
}
for _, u := range urls {
req, err := http.NewRequest(http.MethodHead, u, nil)
if err != nil {
return "", ocispec.Descriptor{}, err
}
// set headers for all the types we support for resolution.
req.Header.Set("Accept", strings.Join([]string{
images.MediaTypeDockerSchema2Manifest,
images.MediaTypeDockerSchema2ManifestList,
ocispec.MediaTypeImageManifest,
ocispec.MediaTypeImageIndex, "*"}, ", "))
log.G(ctx).Debug("resolving")
resp, err := fetcher.doRequestWithRetries(ctx, req, nil)
if err != nil {
return "", ocispec.Descriptor{}, err
}
resp.Body.Close() // don't care about body contents.
if resp.StatusCode > 299 {
if resp.StatusCode == http.StatusNotFound {
continue
}
return "", ocispec.Descriptor{}, errors.Errorf("unexpected status code %v: %v", u, resp.Status)
}
// this is the only point at which we trust the registry. we use the
// content headers to assemble a descriptor for the name. when this becomes
// more robust, we mostly get this information from a secure trust store.
dgstHeader := digest.Digest(resp.Header.Get("Docker-Content-Digest"))
if dgstHeader != "" {
if err := dgstHeader.Validate(); err != nil {
return "", ocispec.Descriptor{}, errors.Wrapf(err, "%q in header not a valid digest", dgstHeader)
}
dgst = dgstHeader
}
if dgst == "" {
return "", ocispec.Descriptor{}, errors.Errorf("could not resolve digest for %v", ref)
}
var (
size int64
sizeHeader = resp.Header.Get("Content-Length")
)
size, err = strconv.ParseInt(sizeHeader, 10, 64)
if err != nil {
return "", ocispec.Descriptor{}, errors.Wrapf(err, "invalid size header: %q", sizeHeader)
}
if size < 0 {
return "", ocispec.Descriptor{}, errors.Errorf("%q in header not a valid size", sizeHeader)
}
desc := ocispec.Descriptor{
Digest: dgst,
MediaType: resp.Header.Get("Content-Type"), // need to strip disposition?
Size: size,
}
log.G(ctx).WithField("desc.digest", desc.Digest).Debug("resolved")
return ref, desc, nil
}
return "", ocispec.Descriptor{}, errors.Errorf("%v not found", ref)
}
func (r *dockerResolver) Fetcher(ctx context.Context, ref string) (remotes.Fetcher, error) {
refspec, err := reference.Parse(ref)
if err != nil {
return nil, err
}
base, err := r.base(refspec)
if err != nil {
return nil, err
}
return dockerFetcher{
dockerBase: base,
}, nil
}
func (r *dockerResolver) Pusher(ctx context.Context, ref string) (remotes.Pusher, error) {
refspec, err := reference.Parse(ref)
if err != nil {
return nil, err
}
// Manifests can be pushed by digest like any other object, but the passed in
// reference cannot take a digest without the associated content. A tag is allowed
// and will be used to tag pushed manifests.
if refspec.Object != "" && strings.Contains(refspec.Object, "@") {
return nil, errors.New("cannot use digest reference for push locator")
}
base, err := r.base(refspec)
if err != nil {
return nil, err
}
return dockerPusher{
dockerBase: base,
tag: refspec.Object,
tracker: r.tracker,
}, nil
}
type dockerBase struct {
refspec reference.Spec
base url.URL
token string
client *http.Client
useBasic bool
username string
secret string
}
func (r *dockerResolver) base(refspec reference.Spec) (*dockerBase, error) {
var (
err error
base url.URL
username, secret string
)
host := refspec.Hostname()
base.Scheme = "https"
if host == "docker.io" {
base.Host = "registry-1.docker.io"
} else {
base.Host = host
if r.plainHTTP || strings.HasPrefix(host, "localhost:") {
base.Scheme = "http"
}
}
if r.credentials != nil {
username, secret, err = r.credentials(base.Host)
if err != nil {
return nil, err
}
}
prefix := strings.TrimPrefix(refspec.Locator, host+"/")
base.Path = path.Join("/v2", prefix)
return &dockerBase{
refspec: refspec,
base: base,
client: r.client,
username: username,
secret: secret,
}, nil
}
func (r *dockerBase) url(ps ...string) string {
url := r.base
url.Path = path.Join(url.Path, path.Join(ps...))
return url.String()
}
func (r *dockerBase) authorize(req *http.Request) {
if r.useBasic {
req.SetBasicAuth(r.username, r.secret)
} else if r.token != "" {
req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", r.token))
}
}
func (r *dockerBase) doRequest(ctx context.Context, req *http.Request) (*http.Response, error) {
ctx = log.WithLogger(ctx, log.G(ctx).WithField("url", req.URL.String()))
log.G(ctx).WithField("request.headers", req.Header).WithField("request.method", req.Method).Debug("do request")
r.authorize(req)
resp, err := ctxhttp.Do(ctx, r.client, req)
if err != nil {
return nil, errors.Wrap(err, "failed to do request")
}
log.G(ctx).WithFields(logrus.Fields{
"status": resp.Status,
"response.headers": resp.Header,
}).Debug("fetch response received")
return resp, nil
}
func (r *dockerBase) doRequestWithRetries(ctx context.Context, req *http.Request, responses []*http.Response) (*http.Response, error) {
resp, err := r.doRequest(ctx, req)
if err != nil {
return nil, err
}
responses = append(responses, resp)
req, err = r.retryRequest(ctx, req, responses)
if err != nil {
resp.Body.Close()
return nil, err
}
if req != nil {
resp.Body.Close()
return r.doRequestWithRetries(ctx, req, responses)
}
return resp, err
}
func (r *dockerBase) retryRequest(ctx context.Context, req *http.Request, responses []*http.Response) (*http.Request, error) {
if len(responses) > 5 {
return nil, nil
}
last := responses[len(responses)-1]
if last.StatusCode == http.StatusUnauthorized {
log.G(ctx).WithField("header", last.Header.Get("WWW-Authenticate")).Debug("Unauthorized")
for _, c := range parseAuthHeader(last.Header) {
if c.scheme == bearerAuth {
if err := invalidAuthorization(c, responses); err != nil {
r.token = ""
return nil, err
}
if err := r.setTokenAuth(ctx, c.parameters); err != nil {
return nil, err
}
return copyRequest(req)
} else if c.scheme == basicAuth {
if r.username != "" && r.secret != "" {
r.useBasic = true
}
return copyRequest(req)
}
}
return nil, nil
} else if last.StatusCode == http.StatusMethodNotAllowed && req.Method == http.MethodHead {
// Support registries which have not properly implemented the HEAD method for
// manifests endpoint
if strings.Contains(req.URL.Path, "/manifests/") {
// TODO: copy request?
req.Method = http.MethodGet
return copyRequest(req)
}
}
// TODO: Handle 50x errors accounting for attempt history
return nil, nil
}
func invalidAuthorization(c challenge, responses []*http.Response) error {
errStr := c.parameters["error"]
if errStr == "" {
return nil
}
n := len(responses)
if n == 1 || (n > 1 && !sameRequest(responses[n-2].Request, responses[n-1].Request)) {
return nil
}
return errors.Wrapf(ErrInvalidAuthorization, "server message: %s", errStr)
}
func sameRequest(r1, r2 *http.Request) bool {
if r1.Method != r2.Method {
return false
}
if *r1.URL != *r2.URL {
return false
}
return true
}
func copyRequest(req *http.Request) (*http.Request, error) {
ireq := *req
if ireq.GetBody != nil {
var err error
ireq.Body, err = ireq.GetBody()
if err != nil {
return nil, err
}
}
return &ireq, nil
}
func (r *dockerBase) setTokenAuth(ctx context.Context, params map[string]string) error {
realm, ok := params["realm"]
if !ok {
return errors.New("no realm specified for token auth challenge")
}
realmURL, err := url.Parse(realm)
if err != nil {
return fmt.Errorf("invalid token auth challenge realm: %s", err)
}
to := tokenOptions{
realm: realmURL.String(),
service: params["service"],
}
to.scopes = getTokenScopes(ctx, params)
if len(to.scopes) == 0 {
return errors.Errorf("no scope specified for token auth challenge")
}
if r.secret != "" {
// Credential information is provided, use oauth POST endpoint
r.token, err = r.fetchTokenWithOAuth(ctx, to)
if err != nil {
return errors.Wrap(err, "failed to fetch oauth token")
}
} else {
// Do request anonymously
r.token, err = r.getToken(ctx, to)
if err != nil {
return errors.Wrap(err, "failed to fetch anonymous token")
}
}
return nil
}
type tokenOptions struct {
realm string
service string
scopes []string
}
type postTokenResponse struct {
AccessToken string `json:"access_token"`
RefreshToken string `json:"refresh_token"`
ExpiresIn int `json:"expires_in"`
IssuedAt time.Time `json:"issued_at"`
Scope string `json:"scope"`
}
func (r *dockerBase) fetchTokenWithOAuth(ctx context.Context, to tokenOptions) (string, error) {
form := url.Values{}
form.Set("scope", strings.Join(to.scopes, " "))
form.Set("service", to.service)
// TODO: Allow setting client_id
form.Set("client_id", "containerd-dist-tool")
if r.username == "" {
form.Set("grant_type", "refresh_token")
form.Set("refresh_token", r.secret)
} else {
form.Set("grant_type", "password")
form.Set("username", r.username)
form.Set("password", r.secret)
}
resp, err := ctxhttp.PostForm(ctx, r.client, to.realm, form)
if err != nil {
return "", err
}
defer resp.Body.Close()
// Registries without support for POST may return 404 for POST /v2/token.
// As of September 2017, GCR is known to return 404.
if (resp.StatusCode == 405 && r.username != "") || resp.StatusCode == 404 {
return r.getToken(ctx, to)
} else if resp.StatusCode < 200 || resp.StatusCode >= 400 {
b, _ := ioutil.ReadAll(io.LimitReader(resp.Body, 64000)) // 64KB
log.G(ctx).WithFields(logrus.Fields{
"status": resp.Status,
"body": string(b),
}).Debugf("token request failed")
// TODO: handle error body and write debug output
return "", errors.Errorf("unexpected status: %s", resp.Status)
}
decoder := json.NewDecoder(resp.Body)
var tr postTokenResponse
if err = decoder.Decode(&tr); err != nil {
return "", fmt.Errorf("unable to decode token response: %s", err)
}
return tr.AccessToken, nil
}
type getTokenResponse struct {
Token string `json:"token"`
AccessToken string `json:"access_token"`
ExpiresIn int `json:"expires_in"`
IssuedAt time.Time `json:"issued_at"`
RefreshToken string `json:"refresh_token"`
}
// getToken fetches a token using a GET request
func (r *dockerBase) getToken(ctx context.Context, to tokenOptions) (string, error) {
req, err := http.NewRequest("GET", to.realm, nil)
if err != nil {
return "", err
}
reqParams := req.URL.Query()
if to.service != "" {
reqParams.Add("service", to.service)
}
for _, scope := range to.scopes {
reqParams.Add("scope", scope)
}
if r.secret != "" {
req.SetBasicAuth(r.username, r.secret)
}
req.URL.RawQuery = reqParams.Encode()
resp, err := ctxhttp.Do(ctx, r.client, req)
if err != nil {
return "", err
}
defer resp.Body.Close()
if resp.StatusCode < 200 || resp.StatusCode >= 400 {
// TODO: handle error body and write debug output
return "", errors.Errorf("unexpected status: %s", resp.Status)
}
decoder := json.NewDecoder(resp.Body)
var tr getTokenResponse
if err = decoder.Decode(&tr); err != nil {
return "", fmt.Errorf("unable to decode token response: %s", err)
}
// `access_token` is equivalent to `token` and if both are specified
// the choice is undefined. Canonicalize `access_token` by sticking
// things in `token`.
if tr.AccessToken != "" {
tr.Token = tr.AccessToken
}
if tr.Token == "" {
return "", ErrNoToken
}
return tr.Token, nil
}