aws node handshake: support both v1 and v2 signatures, default to v1

This enables a smooth migration to the new v2 signature; we can start
using it in a few releases.

upup/pkg/fi/cloudup/awsup/aws_authenticator.go

@@ -17,24 +17,38 @@ limitations under the License.
 package awsup
 
 import (
+	"bytes"
 	"context"
 	"crypto/sha256"
 	"encoding/base64"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"net/url"
+	"time"
 
+	"github.com/aws/aws-sdk-go-v2/aws"
+	v4 "github.com/aws/aws-sdk-go-v2/aws/signer/v4"
 	awsconfig "github.com/aws/aws-sdk-go-v2/config"
 	"github.com/aws/aws-sdk-go-v2/feature/ec2/imds"
 	"github.com/aws/aws-sdk-go-v2/service/sts"
 	smithyhttp "github.com/aws/smithy-go/transport/http"
 	"k8s.io/kops/pkg/bootstrap"
 )
 
-const AWSAuthenticationTokenPrefix = "x-aws-sts "
+const AWSAuthenticationTokenPrefixV1 = "x-aws-sts "
+const AWSAuthenticationTokenPrefixV2 = "x-aws-sts-v2 "
 
 type awsAuthenticator struct {
+	// sts holds the AWS STS client, for signing V2 requests
 	sts *sts.Client
+
+	// region holds the AWS region in which we are running
+	region string
+
+	// credentialsProvider returns our AWS credentials, for sigining V1 requests
+	credentialsProvider aws.CredentialsProvider
 }
 
 var _ bootstrap.Authenticator = &awsAuthenticator{}
@@ -60,23 +74,86 @@ func NewAWSAuthenticator(ctx context.Context, region string) (bootstrap.Authenti
 		return nil, fmt.Errorf("failed to load aws config: %w", err)
 	}
 	return &awsAuthenticator{
-		sts: sts.NewFromConfig(config),
+		credentialsProvider: config.Credentials,
+		region:              region,
+		sts:                 sts.NewFromConfig(config),
 	}, nil
 }
 
+// awsV1Token is the format of the V1 request, it matches http.Header
+type awsV1Token map[string][]string
+
+// awsV2Token is the format of the V2 request, it maps to the http request generated by STS GetCallerIdentity
 type awsV2Token struct {
 	URL          string      `json:"url"`
 	Method       string      `json:"method"`
 	SignedHeader http.Header `json:"headers"`
 }
 
 func (a *awsAuthenticator) CreateToken(body []byte) (string, error) {
+	ctx := context.TODO()
+
+	// We sign with V1, for backwards compatibility.
+	// The issue is that if we upgrade the nodes before the control plane,
+	// the nodes are using v2 authentication against a v1 verifier.
+	// By having the server support v1 and v2, but the nodes continue to use
+	// v1 for now, we can introduce v2 support and then enable it in a few versions.
+	// The "nodes before control plane" is not the common case,
+	// and nodes at much higher versions is not guaranteed to be supported by kube,
+	// so once we are at kOps 1.32 this shoud be safe to flip to use V2.
+	// It's possibly safe at kOps 1.31 but that might need more careful analysis.
+	signWithV1 := true
+	if signWithV1 {
+		return a.createTokenV1(ctx, body)
+	}
+	return a.createTokenV2(ctx, body)
+}
+
+func (a *awsAuthenticator) createTokenV1(ctx context.Context, body []byte) (string, error) {
+	credentials, err := a.credentialsProvider.Retrieve(ctx)
+	if err != nil {
+		return "", fmt.Errorf("getting AWS credentials: %w", err)
+	}
+
+	host, err := a.getSTSHost(ctx)
+	if err != nil {
+		return "", fmt.Errorf("getting AWS STS url: %w", err)
+	}
+	stsURL := "https://" + host + "/"
+	region := a.region
+
+	req, err := signV1Request(ctx, stsURL, region, credentials, time.Now(), body)
+	if err != nil {
+		return "", fmt.Errorf("building (v1) signed request: %w", err)
+	}
+	headers, err := json.Marshal(req.Header)
+	if err != nil {
+		return "", fmt.Errorf("converting headers to json: %w", err)
+	}
+	return AWSAuthenticationTokenPrefixV1 + base64.StdEncoding.EncodeToString(headers), nil
+}
+
+func (a *awsAuthenticator) getSTSHost(ctx context.Context) (string, error) {
+	// An inefficient but reliable way to get the STS url
+	presignClient := sts.NewPresignClient(a.sts)
+	stsRequest, err := presignClient.PresignGetCallerIdentity(ctx, &sts.GetCallerIdentityInput{})
+	if err != nil {
+		return "", fmt.Errorf("building AWS STS presigned request: %w", err)
+	}
+	u, err := url.Parse(stsRequest.URL)
+	if err != nil {
+		return "", fmt.Errorf("parsing AWS STS url: %w", err)
+	}
+	return u.Host, err
+}
+
+func (a *awsAuthenticator) createTokenV2(ctx context.Context, body []byte) (string, error) {
 	sha := sha256.Sum256(body)
 
 	presignClient := sts.NewPresignClient(a.sts)
 
 	// Ensure the signature is only valid for this particular body content.
-	stsRequest, err := presignClient.PresignGetCallerIdentity(context.TODO(), &sts.GetCallerIdentityInput{}, func(po *sts.PresignOptions) {
+	stsRequest, err := presignClient.PresignGetCallerIdentity(ctx, &sts.GetCallerIdentityInput{}, func(po *sts.PresignOptions) {
 		po.ClientOptions = append(po.ClientOptions, func(o *sts.Options) {
 			o.APIOptions = append(o.APIOptions, smithyhttp.AddHeaderValue("X-Kops-Request-SHA", base64.RawStdEncoding.EncodeToString(sha[:])))
 		})
@@ -95,5 +172,32 @@ func (a *awsAuthenticator) CreateToken(body []byte) (string, error) {
 		return "", fmt.Errorf("converting token to json: %w", err)
 	}
 
-	return AWSAuthenticationTokenPrefix + base64.StdEncoding.EncodeToString(token), nil
+	return AWSAuthenticationTokenPrefixV2 + base64.StdEncoding.EncodeToString(token), nil
+}
+
+func signV1Request(ctx context.Context, stsURL string, region string, credentials aws.Credentials, signingTime time.Time, kopsRequestBody []byte) (*http.Request, error) {
+	kopsRequestHash := sha256.Sum256(kopsRequestBody)
+	kopsRequestHashBase64 := base64.RawStdEncoding.EncodeToString(kopsRequestHash[:])
+
+	// V1 requests use a well-known body (and host)
+	body := []byte("Action=GetCallerIdentity&Version=2011-06-15")
+
+	bodyHash := sha256.Sum256(body)
+
+	signedRequest, err := http.NewRequest("POST", stsURL, bytes.NewReader(body))
+	if err != nil {
+		return nil, fmt.Errorf("building http request: %v", err)
+	}
+	signedRequest.Header.Add("Content-Type", "application/x-www-form-urlencoded; charset=utf-8")
+	signedRequest.Header.Add("X-Kops-Request-Sha", kopsRequestHashBase64)
+
+	signer := v4.NewSigner()
+
+	service := "sts"
+
+	if err := signer.SignHTTP(ctx, credentials, signedRequest, hex.EncodeToString(bodyHash[:]), service, region, signingTime); err != nil {
+		return nil, fmt.Errorf("error from SignHTTP: %v", err)
+	}
+
+	return signedRequest, nil
 }