google-auth-library-token

aka. GOOGLE_APPLICATION_CREDENTIALS_to_access_token, GOOGLE_APPLICATION_CREDENTIALS to Authorization header

TLDR usage

Download either executable google-auth-library-token(.exe) from dist:

Windows:

curl.exe -L https://github.com/Masterxilo/google-auth-library-token/raw/master/dist/google-auth-library-token.exe -o google-auth-library-token.exe

Linux:

curl -L https://github.com/Masterxilo/google-auth-library-token/raw/master/dist/google-auth-library-token -o google-auth-library-token ; chmod +x ./google-auth-library-token

Define the environment variable GOOGLE_APPLICATION_CREDENTIALS to point to a service account credentials .json file export GOOGLE_APPLICATION_CREDENTIALS or $env:GOOGLE_APPLICATION_CREDENTIALS, %GOOGLE_APPLICATION_CREDENTIALS%, e.g.

export GOOGLE_APPLICATION_CREDENTIALS="$(realpath GOOGLE_APPLICATION_CREDENTIALS)"

$env:GOOGLE_APPLICATION_CREDENTIALS=(Get-Item GOOGLE_APPLICATION_CREDENTIALS).FullName

to point to the full path of a GOOGLE_APPLICATION_CREDENTIALS file sometimes named service-account-file.json containing something like

{
  "type": "service_account",
  "project_id": "googlecloudprojectname-....",
  "private_key_id": "0e2382b3....e829",
  "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvgIBAzGF2D....5PrjwqY5TxkckWI.............Y8XXTZSilaEZw9NbYNXkJbDNYbAZmpQ4KJUV4CX1AoGBALxfl4vAexkBr3OrPw47\nJIStE/+6XbbTTqzg\n/\n6sQosMIlSscB2EI3tnsdVg6M\n-----END PRIVATE KEY-----\n",
  "client_email": "clientname@projectname-projectid.iam.gserviceaccount.com",
  "client_id": "10.....672",
  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
  "token_uri": "https://oauth2.googleapis.com/token",
  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
  "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/clientname%40projectname-projectid.iam.gserviceaccount.com"
}

then run it

./google-auth-library-token

and obtain on stdout an access_token like:

ya29.c.b0AXv0zTMcQpRhiECLqICqHZNgzbGeuQ0ArL9l********************Ni1Oi9Q0cOarCqUZPCNDX70........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

that can be sent to authenticate/authorize the given client to Google APIs via https header

Authorization: Bearer ${access_token}

Performance Comparison

Given a properly configured GOOGLE_APPLICATION_CREDENTIALS env variable:

$ time gcloud auth application-default print-access-token
ya29.c.c0ASRK0GYgbQi9-jPK19_NeEPenRviiM7-G3FetLySV_nRT1kdzexKPzwRj-IQpCyAu_T4h8z5BsjQ3eepXIWk5uV8O5wlij2i7oonYh_4QUCQMpP0jDU6Q2q9OcKcacEAvSgTEOJd2aGtzRUj3cKx_UtqP5iOOsD0Ueix-lilAQdistCh26zahKJaZ3_dfDPslOpJDAlG0IUqxrmD0TjfnxFqLLf84VRt2bTuoGh9mcx_HpXMvSkunxGBqDtMLXVHDxg-SCA3UJ3HNtS92ZBbcXiU0RDrRzJjOxTe8MONZ5ggGY.....9wdygyXz9rlVwvJpz1-tpQcmdp2Jv3V7

real    0m0.543s
user    0m0.422s
sys     0m0.053s

$ time ./google-auth-library-token 2>/dev/null
ya29.c.c0ASRK0GYmRff9DmE-vfSSqi4hEsIGZG7JPUZtLK18X_J7kk2kErH8qQjYN3ugNqxTHIkb0AQ2ffy...5qhSbczqZtdBo43V-hi7kR7m-4Uogvc644eBgI2_izl6FJB-YJ8SQF5MS6phB0VRcMUysdSOjX1F3XmmzcrfSs

real    0m0.172s
user    0m0.079s
sys     0m0.023s

Troubleshooting

{
  error: Error: error:25066067:DSO support routines:dlfcn_load:could not load the shared library
      at Sign.sign (internal/crypto/sig.js:105:29)
      at Object.sign (/snapshot/app/node_modules/jwa/index.js:152:45)
      at Object.jwsSign [as sign] (/snapshot/app/node_modules/jws/lib/sign-stream.js:32:24)
      at GoogleToken.requestToken (/snapshot/app/node_modules/gtoken/build/src/index.js:225:31)
      at GoogleToken.getTokenAsyncInner (/snapshot/app/node_modules/gtoken/build/src/index.js:163:21)
      at GoogleToken.getTokenAsync (/snapshot/app/node_modules/gtoken/build/src/index.js:142:55)
      at GoogleToken.getToken (/snapshot/app/node_modules/gtoken/build/src/index.js:94:21)
      at JWT.refreshTokenNoCache (/snapshot/app/node_modules/google-auth-library/build/src/auth/jwtclient.js:171:36)
      at JWT.refreshToken (/snapshot/app/node_modules/google-auth-library/build/src/auth/oauth2client.js:152:24)
      at JWT.refreshAccessTokenAsync (/snapshot/app/node_modules/google-auth-library/build/src/auth/oauth2client.js:198:30) {
    opensslErrorStack: [
      'error:0E076071:configuration file routines:module_run:unknown module name',
      'error:0E07506E:configuration file routines:module_load_dso:error loading dso',
      'error:25070067:DSO support routines:DSO_load:could not load the shared library'
    ],
    library: 'DSO support routines',
    function: 'dlfcn_load',
    reason: 'could not load the shared library',
    code: 'ERR_OSSL_DSO_COULD_NOT_LOAD_THE_SHARED_LIBRARY'
  }
}

workaround

export OPENSSL_CONF=/dev/null

Description

Reads the file pointed to by the GOOGLE_APPLICATION_CREDENTIALS environment variable and obtains a new oauth 2 token for the service client/service account described by it to access Google APIs.

Figuring out how long the token will be valid is a separate concern.

This tool has about the same function as

gcloud auth application-default print-access-token

but does not depend on the entire google-cloud-sdk.

See

• https://cloud.google.com/docs/authentication/getting-started
• https://cloud.google.com/docs/authentication/production

Implementation and building

Current implementation uses google-auth-library.GoogleAuth. Binaries are pretty large because they bundle nodejs (built using pkg), but at least run fast.

You can build it on your own using powershell on Windows, pwsh or bash, assuming nodejs/npm are installed:

npm install
./build

TODO

[ ] Maybe we could use cpp client lib for highest efficiency and smaller binaries instead of this insanely large node packaged app.

• https://github.com/googleapis/google-cloud-cpp
• https://github.com/googleapis/google-cloud-cpp/blob/main/google/cloud/storage/quickstart/README.md

[ ] the tool would be more useful if you could also pass the filename GOOGLE_APPLICATION_CREDENTIALS as a relative path as a commandline argument or even the contents of the file...

[x] alpine (musl) instead of glibc based version

Tags

GOOGLE_APPLICATION_CREDENTIALS

google-auth-library GoogleAuth example

token

access token

OAuth 2.0

Google APIs

Authentication

Service Client

Service Credentials

Service Account

Machine to Machine authentication

Google Cloud

gcloud

google-cloud-sdk