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// Copyright 2020 The Go Cloud Development Kit Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// This is an implementation for Options.MakeSignBytes
// that serves as example for how to keep a private key in a separate
// process, service, or HSM/TPM, yet use it as signer for blob.Bucket.
package gcsblob
import (
"context"
"sync"
credentials "cloud.google.com/go/iam/credentials/apiv1"
gax "github.com/googleapis/gax-go/v2"
credentialspb "google.golang.org/genproto/googleapis/iam/credentials/v1"
)
// credentialsClient wraps the IAM Credentials API client for a lazy initialization
// and expresses it in the reduced format expected by SignBytes.
// See https://cloud.google.com/iam/docs/reference/credentials/rest
type credentialsClient struct {
init sync.Once
err error
// client as reduced surface of credentials.IamCredentialsClient
// enables us to use a mock in tests.
client interface {
SignBlob(context.Context, *credentialspb.SignBlobRequest, ...gax.CallOption) (*credentialspb.SignBlobResponse, error)
}
}
// CreateMakeSignBytesWith produces a MakeSignBytes variant from an expanded parameter set.
// It essentially adapts a remote call to the IAM Credentials API
// to the function signature expected by storage.SignedURLOptions.SignBytes.
func (c *credentialsClient) CreateMakeSignBytesWith(lifetimeCtx context.Context, googleAccessID string) func(context.Context) SignBytesFunc {
return func(requestCtx context.Context) SignBytesFunc {
c.init.Do(func() {
if c.client != nil {
// Set previously, likely to a mock implementation for tests.
return
}
c.client, c.err = credentials.NewIamCredentialsClient(lifetimeCtx)
})
return func(p []byte) ([]byte, error) {
if c.err != nil {
return nil, c.err
}
resp, err := c.client.SignBlob(
requestCtx,
&credentialspb.SignBlobRequest{
Name: googleAccessID,
Payload: p,
})
if err != nil {
return nil, err
}
return resp.GetSignedBlob(), nil
}
}
}
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