Can't access metadata token for service-account from Google Container VM image

Question

I am logged into a Google Compute Engine instance from a VM image as detailed here.

I would like to follow the instructions given for accessing the private container registry, but get a 403 error when requesting a token.

Trying this:

$ METADATA=http://metadata.google.internal/computeMetadata/v1
$ SVC_ACCT=$METADATA/instance/service-accounts/default
$ ACCESS_TOKEN=$(curl -H 'Metadata-Flavor: Google' $SVC_ACCT/token \
    | cut -d'"' -f 4)
$ docker login -e [email protected] -u _token -p $ACCESS_TOKEN https://gcr.io
$ docker run --rm gcr.io/<your-project>/<your-image> <command>

..I have no access token found and it fails.

Trying to call the metadata I can see this:

> curl "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/" -H "Metadata-Flavor: Google"

aliases
email
scopes
token

...but when I try to get the token I have a 403 error:

> curl "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token" -H "Metadata-Flavor: Google"

<!DOCTYPE html>
<html lang=en>
  <meta charset=utf-8>
  <meta name=viewport content="initial-scale=1, minimum-scale=1, width=device-width">
  <title>Error 403 (Forbidden)!!1</title>
  <style>
    *{margin:0;padding:0}html,code{font:15px/22px arial,sans-serif}html{background:#fff;color:#222;padding:15px}body{margin:7% auto 0;max-width:390px;min-height:180px;padding:30px 0 15px}* > body{background:url(//www.google.com/images/errors/robot.png) 100% 5px no-repeat;padding-right:205px}p{margin:11px 0 22px;overflow:hidden}ins{color:#777;text-decoration:none}a img{border:0}@media screen and (max-width:772px){body{background:none;margin-top:0;max-width:none;padding-right:0}}#logo{background:url(//www.google.com/images/branding/googlelogo/1x/googlelogo_color_150x54dp.png) no-repeat;margin-left:-5px}@media only screen and (min-resolution:192dpi){#logo{background:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_color_150x54dp.png) no-repeat 0% 0%/100% 100%;-moz-border-image:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_color_150x54dp.png) 0}}@media only screen and (-webkit-min-device-pixel-ratio:2){#logo{background:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_color_150x54dp.png) no-repeat;-webkit-background-size:100% 100%}}#logo{display:inline-block;height:54px;width:150px}
  </style>
  <a href=//www.google.com/><span id=logo aria-label=Google></span></a>
  <p><b>403.</b> <ins>That’s an error.</ins>
  <p>Your client does not have permission to get URL <code>/computeMetadata/v1/instance/service-accounts/default/token</code> from this server.  <ins>That’s all we know.</ins>

I have set the default compute engine service account to be an owner of the project (it was on editor) and tried again, no luck.

I have tried the SO solutions as detailed below, they do not work:

And consulted the Google docs here:

https://cloud.google.com/compute/docs/storing-retrieving-metadata#querying

Is there something I am missing on how to get a successful authentication? Many thanks if you have any suggestions!

MarkeD MarkeD · Accepted Answer · 2016-10-04T15:46:10

Praise the SO gods, I was creating the instance without the correct scopes.

You can check in the GCE UI in the edit instance screen, I had no Google API Cloud access due to passing {"https://www.googleapis.com/auth/cloud-platform"} instead of ["https://www.googleapis.com/auth/cloud-platform"] in the API request.

This command now returns the auth token correctly:

> curl "http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token" -H "Metadata-Flavor: Google"

{"access_token":"ya29.XXXXX","expires_in":3599,"token_type":"Bearer"}

Can't access metadata token for service-account from Google Container VM image

1 Answers