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generate.go
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generate.go
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/*
Copyright 2023 Chainguard, Inc.
SPDX-License-Identifier: Apache-2.0
*/
package aws
import (
"bytes"
"context"
"encoding/base64"
"fmt"
"net/http"
"time"
"github.com/aws/aws-sdk-go-v2/aws"
v4 "github.com/aws/aws-sdk-go-v2/aws/signer/v4"
)
var timeNow = time.Now
const (
audHeader = `Chainguard-Audience`
idHeader = `Chainguard-Identity`
)
// GenerateToken creates token using the supplied AWS credentials that can prove the user's AWS identity. Audience and identity are
// the Chainguard STS url (e.g https://issuer.enforce.dev) and the UID of the Chainguard assumable identity to assume via STS.
func GenerateToken(ctx context.Context, creds aws.Credentials, audience, identity string) (string, error) {
req, err := http.NewRequest("POST", "https://sts.amazonaws.com", nil)
if err != nil {
return "", fmt.Errorf("failed to create new HTTP request: %w", err)
}
req.URL.Path = "/"
req.URL.RawQuery = "Action=GetCallerIdentity&Version=2011-06-15"
req.Header.Add("Accept", "application/json")
req.Header.Add(audHeader, audience)
req.Header.Add(idHeader, identity)
const (
// hashInit is the sha256 hash of an empty buffer, hex encoded.
hashInit = `e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855` //nolint:gosec
// STS service details for signing
svc = `sts`
region = `us-east-1`
)
err = v4.NewSigner().SignHTTP(ctx, creds, req, hashInit, svc, region, timeNow())
if err != nil {
return "", fmt.Errorf("failed to sign GetCallerIdentity request with AWS credentials: %w", err)
}
var b bytes.Buffer
err = req.Write(&b)
if err != nil {
return "", fmt.Errorf("failed to serialize GetCallerIdentity HTTP request to buffer: %w", err)
}
return base64.URLEncoding.EncodeToString(b.Bytes()), nil
}