Add initial implementation to support AWS KMS.
Mariano Cano
4 years ago
parent
b0f768a3fb
commit
c32abb76cd
@ -0,0 +1,237 @@
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package awskms
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import (
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"context"
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"crypto"
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"net/url"
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"strings"
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"time"
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"github.com/smallstep/certificates/kms/uri"
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"github.com/aws/aws-sdk-go/aws/session"
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"github.com/aws/aws-sdk-go/service/kms"
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"github.com/pkg/errors"
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"github.com/smallstep/certificates/kms/apiv1"
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"github.com/smallstep/cli/crypto/pemutil"
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)
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// KMS implements a KMS using AWS Key Management Service.
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type KMS struct {
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session *session.Session
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service *kms.KMS
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}
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// customerMasterKeySpecMapping is a mapping between the step signature algorithm,
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// and bits for RSA keys, with awskms CustomerMasterKeySpec.
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var customerMasterKeySpecMapping = map[apiv1.SignatureAlgorithm]interface{}{
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apiv1.UnspecifiedSignAlgorithm: kms.CustomerMasterKeySpecEccNistP256,
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apiv1.SHA256WithRSA: map[int]string{
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0: kms.CustomerMasterKeySpecRsa3072,
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2048: kms.CustomerMasterKeySpecRsa2048,
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3072: kms.CustomerMasterKeySpecRsa3072,
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4096: kms.CustomerMasterKeySpecRsa4096,
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},
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apiv1.SHA512WithRSA: map[int]string{
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0: kms.CustomerMasterKeySpecRsa4096,
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4096: kms.CustomerMasterKeySpecRsa4096,
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},
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apiv1.SHA256WithRSAPSS: map[int]string{
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0: kms.CustomerMasterKeySpecRsa3072,
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2048: kms.CustomerMasterKeySpecRsa2048,
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3072: kms.CustomerMasterKeySpecRsa3072,
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4096: kms.CustomerMasterKeySpecRsa4096,
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},
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apiv1.SHA512WithRSAPSS: map[int]string{
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0: kms.CustomerMasterKeySpecRsa4096,
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4096: kms.CustomerMasterKeySpecRsa4096,
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},
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apiv1.ECDSAWithSHA256: kms.CustomerMasterKeySpecEccNistP256,
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apiv1.ECDSAWithSHA384: kms.CustomerMasterKeySpecEccNistP384,
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apiv1.ECDSAWithSHA512: kms.CustomerMasterKeySpecEccNistP521,
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}
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// New creates a new AWSKMS. By default, sessions will be created using the
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// credentials in `~/.aws/credentials`, but this can be overridden using the
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// CredentialsFile option, the Region and Profile can also be configured as
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// options.
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//
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// AWS sessions can also be configured with environment variables, see docs at
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// https://docs.aws.amazon.com/sdk-for-go/api/aws/session/ for all the options.
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func New(ctx context.Context, opts apiv1.Options) (*KMS, error) {
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o := session.Options{}
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if opts.Region != "" {
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o.Config.Region = &opts.Region
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}
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if opts.Profile != "" {
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o.Profile = opts.Profile
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}
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if opts.CredentialsFile != "" {
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o.SharedConfigFiles = []string{opts.CredentialsFile}
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}
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sess, err := session.NewSessionWithOptions(o)
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if err != nil {
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return nil, errors.Wrap(err, "error creating AWS session")
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}
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return &KMS{
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session: sess,
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service: kms.New(sess),
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}, nil
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}
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func init() {
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apiv1.Register(apiv1.AmazonKMS, func(ctx context.Context, opts apiv1.Options) (apiv1.KeyManager, error) {
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return New(ctx, opts)
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})
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}
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// GetPublicKey returns a public key from KMS.
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func (k *KMS) GetPublicKey(req *apiv1.GetPublicKeyRequest) (crypto.PublicKey, error) {
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if req.Name == "" {
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return nil, errors.New("getPublicKey 'name' cannot be empty")
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}
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keyID, err := parseKeyID(req.Name)
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if err != nil {
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return nil, err
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}
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ctx, cancel := defaultContext()
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defer cancel()
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resp, err := k.service.GetPublicKeyWithContext(ctx, &kms.GetPublicKeyInput{
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KeyId: &keyID,
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})
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if err != nil {
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return nil, errors.Wrap(err, "awskms GetPublicKeyWithContext failed")
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}
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return pemutil.ParseDER(resp.PublicKey)
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}
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// CreateKey generates a new key in KMS and returns the public key version
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// of it.
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func (k *KMS) CreateKey(req *apiv1.CreateKeyRequest) (*apiv1.CreateKeyResponse, error) {
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if req.Name == "" {
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return nil, errors.New("createKeyRequest 'name' cannot be empty")
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}
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keySpec, err := getCustomerMasterKeySpecMapping(req.SignatureAlgorithm, req.Bits)
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if err != nil {
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return nil, err
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}
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tag := new(kms.Tag)
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tag.SetTagKey("name")
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tag.SetTagValue(req.Name)
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input := &kms.CreateKeyInput{
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Description: &req.Name,
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CustomerMasterKeySpec: &keySpec,
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Tags: []*kms.Tag{tag},
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}
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input.SetKeyUsage(kms.KeyUsageTypeSignVerify)
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ctx, cancel := defaultContext()
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defer cancel()
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resp, err := k.service.CreateKeyWithContext(ctx, input)
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if err != nil {
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return nil, errors.Wrap(err, "awskms CreateKeyWithContext failed")
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}
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if err := k.createKeyAlias(*resp.KeyMetadata.KeyId, req.Name); err != nil {
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return nil, err
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}
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// Create uri for key
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name := uri.New("awskms", url.Values{
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"key-id": []string{*resp.KeyMetadata.KeyId},
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}).String()
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publicKey, err := k.GetPublicKey(&apiv1.GetPublicKeyRequest{
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Name: name,
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})
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if err != nil {
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return nil, err
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}
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// Names uses Amazon Resource Name
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// https://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html#arn-syntax-kms
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return &apiv1.CreateKeyResponse{
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Name: name,
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PublicKey: publicKey,
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CreateSignerRequest: apiv1.CreateSignerRequest{
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SigningKey: name,
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},
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}, nil
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}
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func (k *KMS) createKeyAlias(keyID, alias string) error {
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alias = "alias/" + alias + "-" + keyID[:8]
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ctx, cancel := defaultContext()
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defer cancel()
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_, err := k.service.CreateAliasWithContext(ctx, &kms.CreateAliasInput{
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AliasName: &alias,
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TargetKeyId: &keyID,
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})
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if err != nil {
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return errors.Wrap(err, "awskms CreateAliasWithContext failed")
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}
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return nil
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}
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// CreateSigner creates a new crypto.Signer with a previously configured key.
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func (k *KMS) CreateSigner(req *apiv1.CreateSignerRequest) (crypto.Signer, error) {
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if req.SigningKey == "" {
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return nil, errors.New("createSigner 'signingKey' cannot be empty")
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}
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return NewSigner(k.service, req.SigningKey)
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}
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// Close closes the connection of the KMS client.
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func (k *KMS) Close() error {
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return nil
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}
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func defaultContext() (context.Context, context.CancelFunc) {
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return context.WithTimeout(context.Background(), 15*time.Second)
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}
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// parseKeyID extracts the key-id from an uri.
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func parseKeyID(name string) (string, error) {
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name = strings.ToLower(name)
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if strings.HasPrefix(name, "awskms:") || strings.HasPrefix(name, "aws:") {
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u, err := uri.Parse(name)
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if err != nil {
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return "", err
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}
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if k := u.Get("key-id"); k != "" {
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return k, nil
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}
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return "", errors.Errorf("failed to get key-id from %s", name)
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}
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return name, nil
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}
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func getCustomerMasterKeySpecMapping(alg apiv1.SignatureAlgorithm, bits int) (string, error) {
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v, ok := customerMasterKeySpecMapping[alg]
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if !ok {
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return "", errors.Errorf("awskms does not support signature algorithm '%s'", alg)
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}
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switch v := v.(type) {
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case string:
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return v, nil
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case map[int]string:
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s, ok := v[bits]
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if !ok {
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return "", errors.Errorf("awskms does not support signature algorithm '%s' with '%d' bits", alg, bits)
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}
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return s, nil
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default:
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return "", errors.Errorf("unexpected error: this should not happen")
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}
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}
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@ -0,0 +1,121 @@
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package awskms
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import (
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"crypto"
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"crypto/ecdsa"
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"crypto/rsa"
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"io"
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"github.com/aws/aws-sdk-go/service/kms"
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"github.com/pkg/errors"
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"github.com/smallstep/cli/crypto/pemutil"
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)
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type Signer struct {
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service *kms.KMS
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keyID string
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publicKey crypto.PublicKey
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}
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// NewSigner creates a new signer using a key in the AWS KMS.
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func NewSigner(svc *kms.KMS, signingKey string) (*Signer, error) {
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keyID, err := parseKeyID(signingKey)
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if err != nil {
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return nil, err
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}
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// Make sure that the key exists.
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signer := &Signer{
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service: svc,
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keyID: keyID,
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}
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if err := signer.preloadKey(keyID); err != nil {
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return nil, err
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}
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return signer, nil
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}
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func (s *Signer) preloadKey(keyID string) error {
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ctx, cancel := defaultContext()
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defer cancel()
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resp, err := s.service.GetPublicKeyWithContext(ctx, &kms.GetPublicKeyInput{
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KeyId: &keyID,
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})
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if err != nil {
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return errors.Wrap(err, "awskms GetPublicKeyWithContext failed")
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}
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s.publicKey, err = pemutil.ParseDER(resp.PublicKey)
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return err
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}
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// Public returns the public key of this signer or an error.
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func (s *Signer) Public() crypto.PublicKey {
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return s.publicKey
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}
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// Sign signs digest with the private key stored in the AWS KMS.
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func (s *Signer) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
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alg, err := getSigningAlgorithm(s.Public(), opts)
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if err != nil {
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return nil, err
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}
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req := &kms.SignInput{
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KeyId: &s.keyID,
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SigningAlgorithm: &alg,
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Message: digest,
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}
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req.SetMessageType("DIGEST")
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ctx, cancel := defaultContext()
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defer cancel()
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resp, err := s.service.SignWithContext(ctx, req)
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if err != nil {
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return nil, errors.Wrap(err, "awsKMS SignWithContext failed")
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}
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return resp.Signature, nil
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}
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func getSigningAlgorithm(key crypto.PublicKey, opts crypto.SignerOpts) (string, error) {
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switch key.(type) {
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case *rsa.PublicKey:
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_, isPSS := opts.(*rsa.PSSOptions)
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switch h := opts.HashFunc(); h {
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case crypto.SHA256:
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if isPSS {
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return "RSASSA_PSS_SHA_256", nil
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}
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return "RSASSA_PKCS1_V1_5_SHA_256", nil
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case crypto.SHA384:
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if isPSS {
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return "RSASSA_PSS_SHA_384", nil
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}
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return "RSASSA_PKCS1_V1_5_SHA_384", nil
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case crypto.SHA512:
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if isPSS {
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return "RSASSA_PSS_SHA_512", nil
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}
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return "RSASSA_PKCS1_V1_5_SHA_512", nil
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default:
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return "", errors.Errorf("unsupported hash function %v", h)
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}
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case *ecdsa.PublicKey:
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switch h := opts.HashFunc(); h {
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case crypto.SHA256:
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return "ECDSA_SHA_256", nil
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case crypto.SHA384:
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return "ECDSA_SHA_384", nil
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case crypto.SHA512:
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return "ECDSA_SHA_512", nil
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default:
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return "", errors.Errorf("unsupported hash function %v", h)
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}
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default:
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return "", errors.Errorf("unsupported key type %T", key)
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}
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}
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