certificates/kms/awskms/awskms.go
2020-05-19 17:35:36 -07:00

237 lines
6.5 KiB
Go

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