selfsignedjwt.go

Documentation: cloud.google.com/go/auth/credentials

     1  // Copyright 2023 Google LLC
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //      http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package credentials
    16  
    17  import (
    18  	"context"
    19  	"crypto/rsa"
    20  	"fmt"
    21  	"strings"
    22  	"time"
    23  
    24  	"cloud.google.com/go/auth"
    25  	"cloud.google.com/go/auth/internal"
    26  	"cloud.google.com/go/auth/internal/credsfile"
    27  	"cloud.google.com/go/auth/internal/jwt"
    28  )
    29  
    30  var (
    31  	// for testing
    32  	now func() time.Time = time.Now
    33  )
    34  
    35  // configureSelfSignedJWT uses the private key in the service account to create
    36  // a JWT without making a network call.
    37  func configureSelfSignedJWT(f *credsfile.ServiceAccountFile, opts *DetectOptions) (auth.TokenProvider, error) {
    38  	pk, err := internal.ParseKey([]byte(f.PrivateKey))
    39  	if err != nil {
    40  		return nil, fmt.Errorf("credentials: could not parse key: %w", err)
    41  	}
    42  	return &selfSignedTokenProvider{
    43  		email:    f.ClientEmail,
    44  		audience: opts.Audience,
    45  		scopes:   opts.scopes(),
    46  		pk:       pk,
    47  		pkID:     f.PrivateKeyID,
    48  	}, nil
    49  }
    50  
    51  type selfSignedTokenProvider struct {
    52  	email    string
    53  	audience string
    54  	scopes   []string
    55  	pk       *rsa.PrivateKey
    56  	pkID     string
    57  }
    58  
    59  func (tp *selfSignedTokenProvider) Token(context.Context) (*auth.Token, error) {
    60  	iat := now()
    61  	exp := iat.Add(time.Hour)
    62  	scope := strings.Join(tp.scopes, " ")
    63  	c := &jwt.Claims{
    64  		Iss:   tp.email,
    65  		Sub:   tp.email,
    66  		Aud:   tp.audience,
    67  		Scope: scope,
    68  		Iat:   iat.Unix(),
    69  		Exp:   exp.Unix(),
    70  	}
    71  	h := &jwt.Header{
    72  		Algorithm: jwt.HeaderAlgRSA256,
    73  		Type:      jwt.HeaderType,
    74  		KeyID:     string(tp.pkID),
    75  	}
    76  	msg, err := jwt.EncodeJWS(h, c, tp.pk)
    77  	if err != nil {
    78  		return nil, fmt.Errorf("credentials: could not encode JWT: %w", err)
    79  	}
    80  	return &auth.Token{Value: msg, Type: internal.TokenTypeBearer, Expiry: exp}, nil
    81  }
    82
View as plain text