forked from remote/oauth2
google/externalaccount: moves externalaccount package out of internal and exports it
go/programmable-auth-design for context. Adds support for user defined supplier methods to return subject tokens and AWS security credentials. Change-Id: I7bc41f8c5202ae933fce516632f5049bbeb3d378 GitHub-Last-Rev: ac519b242f8315df572f1b205b0670f139bfc6c3 GitHub-Pull-Request: golang/oauth2#690 Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/550835 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Leo Siracusa <leosiracusa@google.com> Reviewed-by: Chris Smith <chrisdsmith@google.com> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Cody Oss <codyoss@google.com>
This commit is contained in:
463
google/externalaccount/basecredentials.go
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463
google/externalaccount/basecredentials.go
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@@ -0,0 +1,463 @@
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// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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Package externalaccount provides support for creating workload identity
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federation and workforce identity federation token sources that can be
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used to access Google Cloud resources from external identity providers.
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# Workload Identity Federation
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Using workload identity federation, your application can access Google Cloud
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resources from Amazon Web Services (AWS), Microsoft Azure or any identity
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provider that supports OpenID Connect (OIDC) or SAML 2.0.
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Traditionally, applications running outside Google Cloud have used service
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account keys to access Google Cloud resources. Using identity federation,
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you can allow your workload to impersonate a service account.
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This lets you access Google Cloud resources directly, eliminating the
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maintenance and security burden associated with service account keys.
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Follow the detailed instructions on how to configure Workload Identity Federation
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in various platforms:
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Amazon Web Services (AWS): https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#aws
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Microsoft Azure: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-clouds#azure
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OIDC identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#oidc
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SAML 2.0 identity provider: https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#saml
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For OIDC and SAML providers, the library can retrieve tokens in fours ways:
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from a local file location (file-sourced credentials), from a server
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(URL-sourced credentials), from a local executable (executable-sourced
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credentials), or from a user defined function that returns an OIDC or SAML token.
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For file-sourced credentials, a background process needs to be continuously
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refreshing the file location with a new OIDC/SAML token prior to expiration.
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For tokens with one hour lifetimes, the token needs to be updated in the file
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every hour. The token can be stored directly as plain text or in JSON format.
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For URL-sourced credentials, a local server needs to host a GET endpoint to
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return the OIDC/SAML token. The response can be in plain text or JSON.
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Additional required request headers can also be specified.
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For executable-sourced credentials, an application needs to be available to
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output the OIDC/SAML token and other information in a JSON format.
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For more information on how these work (and how to implement
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executable-sourced credentials), please check out:
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https://cloud.google.com/iam/docs/workload-identity-federation-with-other-providers#create_a_credential_configuration
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To use a custom function to supply the token, define a struct that implements the [SubjectTokenSupplier] interface for OIDC/SAML providers,
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or one that implements [AwsSecurityCredentialsSupplier] for AWS providers. This can then be used when building a [Config].
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The [golang.org/x/oauth2.TokenSource] created from the config using [NewTokenSource] can then be used to access Google
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Cloud resources. For instance, you can create a new client from the
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[cloud.google.com/go/storage] package and pass in option.WithTokenSource(yourTokenSource))
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Note that this library does not perform any validation on the token_url, token_info_url,
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or service_account_impersonation_url fields of the credential configuration.
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It is not recommended to use a credential configuration that you did not generate with
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the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
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# Workforce Identity Federation
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Workforce identity federation lets you use an external identity provider (IdP) to
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authenticate and authorize a workforce—a group of users, such as employees, partners,
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and contractors—using IAM, so that the users can access Google Cloud services.
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Workforce identity federation extends Google Cloud's identity capabilities to support
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syncless, attribute-based single sign on.
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With workforce identity federation, your workforce can access Google Cloud resources
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using an external identity provider (IdP) that supports OpenID Connect (OIDC) or
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SAML 2.0 such as Azure Active Directory (Azure AD), Active Directory Federation
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Services (AD FS), Okta, and others.
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|
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Follow the detailed instructions on how to configure Workload Identity Federation
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in various platforms:
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Azure AD: https://cloud.google.com/iam/docs/workforce-sign-in-azure-ad
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Okta: https://cloud.google.com/iam/docs/workforce-sign-in-okta
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OIDC identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#oidc
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SAML 2.0 identity provider: https://cloud.google.com/iam/docs/configuring-workforce-identity-federation#saml
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|
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For workforce identity federation, the library can retrieve tokens in four ways:
|
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from a local file location (file-sourced credentials), from a server
|
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(URL-sourced credentials), from a local executable (executable-sourced
|
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credentials), or from a user supplied function that returns an OIDC or SAML token.
|
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For file-sourced credentials, a background process needs to be continuously
|
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refreshing the file location with a new OIDC/SAML token prior to expiration.
|
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For tokens with one hour lifetimes, the token needs to be updated in the file
|
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every hour. The token can be stored directly as plain text or in JSON format.
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For URL-sourced credentials, a local server needs to host a GET endpoint to
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return the OIDC/SAML token. The response can be in plain text or JSON.
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Additional required request headers can also be specified.
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For executable-sourced credentials, an application needs to be available to
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output the OIDC/SAML token and other information in a JSON format.
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For more information on how these work (and how to implement
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executable-sourced credentials), please check out:
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https://cloud.google.com/iam/docs/workforce-obtaining-short-lived-credentials#generate_a_configuration_file_for_non-interactive_sign-in
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To use a custom function to supply the token, define a struct that implements the [SubjectTokenSupplier] interface for OIDC/SAML providers.
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This can then be used when building a [Config].
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The [golang.org/x/oauth2.TokenSource] created from the config using [NewTokenSource] can then be used access Google
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Cloud resources. For instance, you can create a new client from the
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[cloud.google.com/go/storage] package and pass in option.WithTokenSource(yourTokenSource))
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# Security considerations
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Note that this library does not perform any validation on the token_url, token_info_url,
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or service_account_impersonation_url fields of the credential configuration.
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It is not recommended to use a credential configuration that you did not generate with
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the gcloud CLI unless you verify that the URL fields point to a googleapis.com domain.
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*/
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package externalaccount
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import (
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"context"
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"fmt"
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"net/http"
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"regexp"
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"strconv"
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"time"
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"golang.org/x/oauth2"
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"golang.org/x/oauth2/google/internal/impersonate"
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"golang.org/x/oauth2/google/internal/stsexchange"
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)
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// now aliases time.Now for testing
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var now = func() time.Time {
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return time.Now().UTC()
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}
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// Config stores the configuration for fetching tokens with external credentials.
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type Config struct {
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// Audience is the Secure Token Service (STS) audience which contains the resource name for the workload
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// identity pool or the workforce pool and the provider identifier in that pool. Required.
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Audience string
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// SubjectTokenType is the STS token type based on the Oauth2.0 token exchange spec.
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// Expected values include:
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// “urn:ietf:params:oauth:token-type:jwt”
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// “urn:ietf:params:oauth:token-type:id-token”
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// “urn:ietf:params:oauth:token-type:saml2”
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// “urn:ietf:params:aws:token-type:aws4_request”
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// Required.
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SubjectTokenType string
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// TokenURL is the STS token exchange endpoint. If not provided, will default to
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// https://sts.googleapis.com/v1/token. Optional.
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TokenURL string
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// TokenInfoURL is the token_info endpoint used to retrieve the account related information (
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// user attributes like account identifier, eg. email, username, uid, etc). This is
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// needed for gCloud session account identification. Optional.
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TokenInfoURL string
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// ServiceAccountImpersonationURL is the URL for the service account impersonation request. This is only
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// required for workload identity pools when APIs to be accessed have not integrated with UberMint. Optional.
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ServiceAccountImpersonationURL string
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// ServiceAccountImpersonationLifetimeSeconds is the number of seconds the service account impersonation
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// token will be valid for. If not provided, it will default to 3600. Optional.
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ServiceAccountImpersonationLifetimeSeconds int
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// ClientSecret is currently only required if token_info endpoint also
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// needs to be called with the generated GCP access token. When provided, STS will be
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// called with additional basic authentication using ClientId as username and ClientSecret as password. Optional.
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ClientSecret string
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// ClientID is only required in conjunction with ClientSecret, as described above. Optional.
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ClientID string
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// CredentialSource contains the necessary information to retrieve the token itself, as well
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// as some environmental information. One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or
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// CredentialSource must be provided. Optional.
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CredentialSource *CredentialSource
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// QuotaProjectID is injected by gCloud. If the value is non-empty, the Auth libraries
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// will set the x-goog-user-project header which overrides the project associated with the credentials. Optional.
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QuotaProjectID string
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// Scopes contains the desired scopes for the returned access token. Optional.
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Scopes []string
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// WorkforcePoolUserProject is the workforce pool user project number when the credential
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// corresponds to a workforce pool and not a workload identity pool.
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// The underlying principal must still have serviceusage.services.use IAM
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// permission to use the project for billing/quota. Optional.
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WorkforcePoolUserProject string
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// SubjectTokenSupplier is an optional token supplier for OIDC/SAML credentials.
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// One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or CredentialSource must be provided. Optional.
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SubjectTokenSupplier SubjectTokenSupplier
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// AwsSecurityCredentialsSupplier is an AWS Security Credential supplier for AWS credentials.
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// One of SubjectTokenSupplier, AWSSecurityCredentialSupplier or CredentialSource must be provided. Optional.
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AwsSecurityCredentialsSupplier AwsSecurityCredentialsSupplier
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}
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var (
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validWorkforceAudiencePattern *regexp.Regexp = regexp.MustCompile(`//iam\.googleapis\.com/locations/[^/]+/workforcePools/`)
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)
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func validateWorkforceAudience(input string) bool {
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return validWorkforceAudiencePattern.MatchString(input)
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}
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// NewTokenSource Returns an external account TokenSource using the provided external account config.
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func NewTokenSource(ctx context.Context, conf Config) (oauth2.TokenSource, error) {
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if conf.Audience == "" {
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return nil, fmt.Errorf("oauth2/google/externalaccount: Audience must be set")
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}
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if conf.SubjectTokenType == "" {
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return nil, fmt.Errorf("oauth2/google/externalaccount: Subject token type must be set")
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}
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if conf.WorkforcePoolUserProject != "" {
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valid := validateWorkforceAudience(conf.Audience)
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if !valid {
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return nil, fmt.Errorf("oauth2/google/externalaccount: Workforce pool user project should not be set for non-workforce pool credentials")
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}
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}
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count := 0
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if conf.CredentialSource != nil {
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count++
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}
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if conf.SubjectTokenSupplier != nil {
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count++
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}
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if conf.AwsSecurityCredentialsSupplier != nil {
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count++
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}
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if count == 0 {
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return nil, fmt.Errorf("oauth2/google/externalaccount: One of CredentialSource, SubjectTokenSupplier, or AwsSecurityCredentialsSupplier must be set")
|
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}
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if count > 1 {
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return nil, fmt.Errorf("oauth2/google/externalaccount: Only one of CredentialSource, SubjectTokenSupplier, or AwsSecurityCredentialsSupplier must be set")
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}
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return conf.tokenSource(ctx, "https")
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}
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|
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// tokenSource is a private function that's directly called by some of the tests,
|
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// because the unit test URLs are mocked, and would otherwise fail the
|
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// validity check.
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func (c *Config) tokenSource(ctx context.Context, scheme string) (oauth2.TokenSource, error) {
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|
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ts := tokenSource{
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ctx: ctx,
|
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conf: c,
|
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}
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if c.ServiceAccountImpersonationURL == "" {
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return oauth2.ReuseTokenSource(nil, ts), nil
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}
|
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scopes := c.Scopes
|
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ts.conf.Scopes = []string{"https://www.googleapis.com/auth/cloud-platform"}
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imp := impersonate.ImpersonateTokenSource{
|
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Ctx: ctx,
|
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URL: c.ServiceAccountImpersonationURL,
|
||||
Scopes: scopes,
|
||||
Ts: oauth2.ReuseTokenSource(nil, ts),
|
||||
TokenLifetimeSeconds: c.ServiceAccountImpersonationLifetimeSeconds,
|
||||
}
|
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return oauth2.ReuseTokenSource(nil, imp), nil
|
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}
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||||
|
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// Subject token file types.
|
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const (
|
||||
fileTypeText = "text"
|
||||
fileTypeJSON = "json"
|
||||
defaultTokenUrl = "https://sts.googleapis.com/v1/token"
|
||||
)
|
||||
|
||||
// Format contains information needed to retireve a subject token for URL or File sourced credentials.
|
||||
type Format struct {
|
||||
// Type should be either "text" or "json". This determines whether the file or URL sourced credentials
|
||||
// expect a simple text subject token or if the subject token will be contained in a JSON object.
|
||||
// When not provided "text" type is assumed.
|
||||
Type string `json:"type"`
|
||||
// SubjectTokenFieldName is only required for JSON format. This is the field name that the credentials will check
|
||||
// for the subject token in the file or URL response. This would be "access_token" for azure.
|
||||
SubjectTokenFieldName string `json:"subject_token_field_name"`
|
||||
}
|
||||
|
||||
// CredentialSource stores the information necessary to retrieve the credentials for the STS exchange.
|
||||
type CredentialSource struct {
|
||||
// File is the location for file sourced credentials.
|
||||
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
|
||||
File string `json:"file"`
|
||||
|
||||
// Url is the URL to call for URL sourced credentials.
|
||||
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
|
||||
URL string `json:"url"`
|
||||
// Headers are the headers to attach to the request for URL sourced credentials.
|
||||
Headers map[string]string `json:"headers"`
|
||||
|
||||
// Executable is the configuration object for executable sourced credentials.
|
||||
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
|
||||
Executable *ExecutableConfig `json:"executable"`
|
||||
|
||||
// EnvironmentID is the EnvironmentID used for AWS sourced credentials. This should start with "AWS".
|
||||
// One field amongst File, URL, Executable, or EnvironmentID should be provided, depending on the kind of credential in question.
|
||||
EnvironmentID string `json:"environment_id"`
|
||||
// RegionURL is the metadata URL to retrieve the region from for EC2 AWS credentials.
|
||||
RegionURL string `json:"region_url"`
|
||||
// RegionalCredVerificationURL is the AWS regional credential verification URL, will default to
|
||||
// "https://sts.{region}.amazonaws.com?Action=GetCallerIdentity&Version=2011-06-15" if not provided."
|
||||
RegionalCredVerificationURL string `json:"regional_cred_verification_url"`
|
||||
// IMDSv2SessionTokenURL is the URL to retrieve the session token when using IMDSv2 in AWS.
|
||||
IMDSv2SessionTokenURL string `json:"imdsv2_session_token_url"`
|
||||
// Format is the format type for the subject token. Used for File and URL sourced credentials. Expected values are "text" or "json".
|
||||
Format Format `json:"format"`
|
||||
}
|
||||
|
||||
// ExecutableConfig contains information needed for executable sourced credentials.
|
||||
type ExecutableConfig struct {
|
||||
// Command is the the full command to run to retrieve the subject token.
|
||||
// This can include arguments. Must be an absolute path for the program. Required.
|
||||
Command string `json:"command"`
|
||||
// TimeoutMillis is the timeout duration, in milliseconds. Defaults to 30000 milliseconds when not provided. Optional.
|
||||
TimeoutMillis *int `json:"timeout_millis"`
|
||||
// OutputFile is the absolute path to the output file where the executable will cache the response.
|
||||
// If specified the auth libraries will first check this location before running the executable. Optional.
|
||||
OutputFile string `json:"output_file"`
|
||||
}
|
||||
|
||||
// SubjectTokenSupplier can be used to supply a subject token to exchange for a GCP access token.
|
||||
type SubjectTokenSupplier interface {
|
||||
// SubjectToken should return a valid subject token or an error.
|
||||
// The external account token source does not cache the returned subject token, so caching
|
||||
// logic should be implemented in the supplier to prevent multiple requests for the same subject token.
|
||||
SubjectToken(ctx context.Context, options SupplierOptions) (string, error)
|
||||
}
|
||||
|
||||
// AWSSecurityCredentialsSupplier can be used to supply AwsSecurityCredentials and an AWS Region to
|
||||
// exchange for a GCP access token.
|
||||
type AwsSecurityCredentialsSupplier interface {
|
||||
// AwsRegion should return the AWS region or an error.
|
||||
AwsRegion(ctx context.Context, options SupplierOptions) (string, error)
|
||||
// GetAwsSecurityCredentials should return a valid set of AwsSecurityCredentials or an error.
|
||||
// The external account token source does not cache the returned security credentials, so caching
|
||||
// logic should be implemented in the supplier to prevent multiple requests for the same security credentials.
|
||||
AwsSecurityCredentials(ctx context.Context, options SupplierOptions) (*AwsSecurityCredentials, error)
|
||||
}
|
||||
|
||||
// SupplierOptions contains information about the requested subject token or AWS security credentials from the
|
||||
// Google external account credential.
|
||||
type SupplierOptions struct {
|
||||
// Audience is the requested audience for the external account credential.
|
||||
Audience string
|
||||
// Subject token type is the requested subject token type for the external account credential. Expected values include:
|
||||
// “urn:ietf:params:oauth:token-type:jwt”
|
||||
// “urn:ietf:params:oauth:token-type:id-token”
|
||||
// “urn:ietf:params:oauth:token-type:saml2”
|
||||
// “urn:ietf:params:aws:token-type:aws4_request”
|
||||
SubjectTokenType string
|
||||
}
|
||||
|
||||
// parse determines the type of CredentialSource needed.
|
||||
func (c *Config) parse(ctx context.Context) (baseCredentialSource, error) {
|
||||
//set Defaults
|
||||
if c.TokenURL == "" {
|
||||
c.TokenURL = defaultTokenUrl
|
||||
}
|
||||
supplierOptions := SupplierOptions{Audience: c.Audience, SubjectTokenType: c.SubjectTokenType}
|
||||
|
||||
if c.AwsSecurityCredentialsSupplier != nil {
|
||||
awsCredSource := awsCredentialSource{
|
||||
awsSecurityCredentialsSupplier: c.AwsSecurityCredentialsSupplier,
|
||||
targetResource: c.Audience,
|
||||
supplierOptions: supplierOptions,
|
||||
ctx: ctx,
|
||||
}
|
||||
return awsCredSource, nil
|
||||
} else if c.SubjectTokenSupplier != nil {
|
||||
return programmaticRefreshCredentialSource{subjectTokenSupplier: c.SubjectTokenSupplier, supplierOptions: supplierOptions, ctx: ctx}, nil
|
||||
} else if len(c.CredentialSource.EnvironmentID) > 3 && c.CredentialSource.EnvironmentID[:3] == "aws" {
|
||||
if awsVersion, err := strconv.Atoi(c.CredentialSource.EnvironmentID[3:]); err == nil {
|
||||
if awsVersion != 1 {
|
||||
return nil, fmt.Errorf("oauth2/google/externalaccount: aws version '%d' is not supported in the current build", awsVersion)
|
||||
}
|
||||
|
||||
awsCredSource := awsCredentialSource{
|
||||
environmentID: c.CredentialSource.EnvironmentID,
|
||||
regionURL: c.CredentialSource.RegionURL,
|
||||
regionalCredVerificationURL: c.CredentialSource.RegionalCredVerificationURL,
|
||||
credVerificationURL: c.CredentialSource.URL,
|
||||
targetResource: c.Audience,
|
||||
ctx: ctx,
|
||||
}
|
||||
if c.CredentialSource.IMDSv2SessionTokenURL != "" {
|
||||
awsCredSource.imdsv2SessionTokenURL = c.CredentialSource.IMDSv2SessionTokenURL
|
||||
}
|
||||
|
||||
return awsCredSource, nil
|
||||
}
|
||||
} else if c.CredentialSource.File != "" {
|
||||
return fileCredentialSource{File: c.CredentialSource.File, Format: c.CredentialSource.Format}, nil
|
||||
} else if c.CredentialSource.URL != "" {
|
||||
return urlCredentialSource{URL: c.CredentialSource.URL, Headers: c.CredentialSource.Headers, Format: c.CredentialSource.Format, ctx: ctx}, nil
|
||||
} else if c.CredentialSource.Executable != nil {
|
||||
return createExecutableCredential(ctx, c.CredentialSource.Executable, c)
|
||||
}
|
||||
return nil, fmt.Errorf("oauth2/google/externalaccount: unable to parse credential source")
|
||||
}
|
||||
|
||||
type baseCredentialSource interface {
|
||||
credentialSourceType() string
|
||||
subjectToken() (string, error)
|
||||
}
|
||||
|
||||
// tokenSource is the source that handles external credentials. It is used to retrieve Tokens.
|
||||
type tokenSource struct {
|
||||
ctx context.Context
|
||||
conf *Config
|
||||
}
|
||||
|
||||
func getMetricsHeaderValue(conf *Config, credSource baseCredentialSource) string {
|
||||
return fmt.Sprintf("gl-go/%s auth/%s google-byoid-sdk source/%s sa-impersonation/%t config-lifetime/%t",
|
||||
goVersion(),
|
||||
"unknown",
|
||||
credSource.credentialSourceType(),
|
||||
conf.ServiceAccountImpersonationURL != "",
|
||||
conf.ServiceAccountImpersonationLifetimeSeconds != 0)
|
||||
}
|
||||
|
||||
// Token allows tokenSource to conform to the oauth2.TokenSource interface.
|
||||
func (ts tokenSource) Token() (*oauth2.Token, error) {
|
||||
conf := ts.conf
|
||||
|
||||
credSource, err := conf.parse(ts.ctx)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
subjectToken, err := credSource.subjectToken()
|
||||
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
stsRequest := stsexchange.TokenExchangeRequest{
|
||||
GrantType: "urn:ietf:params:oauth:grant-type:token-exchange",
|
||||
Audience: conf.Audience,
|
||||
Scope: conf.Scopes,
|
||||
RequestedTokenType: "urn:ietf:params:oauth:token-type:access_token",
|
||||
SubjectToken: subjectToken,
|
||||
SubjectTokenType: conf.SubjectTokenType,
|
||||
}
|
||||
header := make(http.Header)
|
||||
header.Add("Content-Type", "application/x-www-form-urlencoded")
|
||||
header.Add("x-goog-api-client", getMetricsHeaderValue(conf, credSource))
|
||||
clientAuth := stsexchange.ClientAuthentication{
|
||||
AuthStyle: oauth2.AuthStyleInHeader,
|
||||
ClientID: conf.ClientID,
|
||||
ClientSecret: conf.ClientSecret,
|
||||
}
|
||||
var options map[string]interface{}
|
||||
// Do not pass workforce_pool_user_project when client authentication is used.
|
||||
// The client ID is sufficient for determining the user project.
|
||||
if conf.WorkforcePoolUserProject != "" && conf.ClientID == "" {
|
||||
options = map[string]interface{}{
|
||||
"userProject": conf.WorkforcePoolUserProject,
|
||||
}
|
||||
}
|
||||
stsResp, err := stsexchange.ExchangeToken(ts.ctx, conf.TokenURL, &stsRequest, clientAuth, header, options)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
|
||||
accessToken := &oauth2.Token{
|
||||
AccessToken: stsResp.AccessToken,
|
||||
TokenType: stsResp.TokenType,
|
||||
}
|
||||
if stsResp.ExpiresIn < 0 {
|
||||
return nil, fmt.Errorf("oauth2/google/externalaccount: got invalid expiry from security token service")
|
||||
} else if stsResp.ExpiresIn >= 0 {
|
||||
accessToken.Expiry = now().Add(time.Duration(stsResp.ExpiresIn) * time.Second)
|
||||
}
|
||||
|
||||
if stsResp.RefreshToken != "" {
|
||||
accessToken.RefreshToken = stsResp.RefreshToken
|
||||
}
|
||||
return accessToken, nil
|
||||
}
|
||||
Reference in New Issue
Block a user