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//
// Copyright 2021 The Sigstore 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
//
// http://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.
package hashivault
import (
"context"
"crypto"
"errors"
"fmt"
"io"
"strconv"
"github.com/sigstore/sigstore/pkg/signature"
"github.com/sigstore/sigstore/pkg/signature/options"
)
// Taken from https://www.vaultproject.io/api/secret/transit
// nolint:revive
const (
AlgorithmECDSAP256 = "ecdsa-p256"
AlgorithmECDSAP384 = "ecdsa-p384"
AlgorithmECDSAP521 = "ecdsa-p521"
AlgorithmED25519 = "ed25519"
AlgorithmRSA2048 = "rsa-2048"
AlgorithmRSA3072 = "rsa-3072"
AlgorithmRSA4096 = "rsa-4096"
)
var hvSupportedAlgorithms = []string{
AlgorithmECDSAP256,
AlgorithmECDSAP384,
AlgorithmECDSAP521,
AlgorithmED25519,
AlgorithmRSA2048,
AlgorithmRSA3072,
AlgorithmRSA4096,
}
var hvSupportedHashFuncs = []crypto.Hash{
crypto.SHA224,
crypto.SHA256,
crypto.SHA384,
crypto.SHA512,
crypto.Hash(0),
}
// SignerVerifier creates and verifies digital signatures over a message using Hashicorp Vault KMS service
type SignerVerifier struct {
hashFunc crypto.Hash
client *hashivaultClient
}
// LoadSignerVerifier generates signatures using the specified key object in Vault and hash algorithm.
//
// It also can verify signatures (via a remote vall to the Vault instance). hashFunc should be
// set to crypto.Hash(0) if the key referred to by referenceStr is an ED25519 signing key.
func LoadSignerVerifier(referenceStr string, hashFunc crypto.Hash, opts ...signature.RPCOption) (*SignerVerifier, error) {
h := &SignerVerifier{}
ctx := context.Background()
rpcAuth := options.RPCAuth{}
var keyVersion string
for _, opt := range opts {
opt.ApplyRPCAuthOpts(&rpcAuth)
opt.ApplyContext(&ctx)
opt.ApplyKeyVersion(&keyVersion)
}
var keyVersionUint uint64
var err error
if keyVersion != "" {
keyVersionUint, err = strconv.ParseUint(keyVersion, 10, 64)
if err != nil {
return nil, fmt.Errorf("parsing key version: %w", err)
}
}
if rpcAuth.OIDC.Token != "" {
rpcAuth.Token, err = oidcLogin(ctx, rpcAuth.Address, rpcAuth.OIDC.Path, rpcAuth.OIDC.Role, rpcAuth.OIDC.Token)
if err != nil {
return nil, err
}
}
h.client, err = newHashivaultClient(rpcAuth.Address, rpcAuth.Token, rpcAuth.Path, referenceStr, keyVersionUint)
if err != nil {
return nil, err
}
switch hashFunc {
case 0, crypto.SHA224, crypto.SHA256, crypto.SHA384, crypto.SHA512:
h.hashFunc = hashFunc
default:
return nil, errors.New("hash function not supported by Hashivault")
}
return h, nil
}
// SignMessage signs the provided message using HashiCorp Vault KMS. If the message is provided,
// this method will compute the digest according to the hash function specified
// when the HashivaultSigner was created.
//
// SignMessage recognizes the following Options listed in order of preference:
//
// - WithDigest()
//
// All other options are ignored if specified.
func (h SignerVerifier) SignMessage(message io.Reader, opts ...signature.SignOption) ([]byte, error) {
var digest []byte
var signerOpts crypto.SignerOpts = h.hashFunc
for _, opt := range opts {
opt.ApplyDigest(&digest)
opt.ApplyCryptoSignerOpts(&signerOpts)
}
digest, hf, err := signature.ComputeDigestForSigning(message, signerOpts.HashFunc(), hvSupportedHashFuncs, opts...)
if err != nil {
return nil, err
}
return h.client.sign(digest, hf, opts...)
}
// PublicKey returns the public key that can be used to verify signatures created by
// this signer. All options provided in arguments to this method are ignored.
func (h SignerVerifier) PublicKey(_ ...signature.PublicKeyOption) (crypto.PublicKey, error) {
return h.client.public()
}
// VerifySignature verifies the signature for the given message. Unless provided
// in an option, the digest of the message will be computed using the hash function specified
// when the SignerVerifier was created.
//
// This function returns nil if the verification succeeded, and an error message otherwise.
//
// This function recognizes the following Options listed in order of preference:
//
// - WithDigest()
//
// - WithCryptoSignerOpts()
//
// All other options are ignored if specified.
func (h SignerVerifier) VerifySignature(sig, message io.Reader, opts ...signature.VerifyOption) error {
var digest []byte
var signerOpts crypto.SignerOpts = h.hashFunc
for _, opt := range opts {
opt.ApplyDigest(&digest)
opt.ApplyCryptoSignerOpts(&signerOpts)
}
digest, hf, err := signature.ComputeDigestForVerifying(message, signerOpts.HashFunc(), hvSupportedHashFuncs, opts...)
if err != nil {
return err
}
sigBytes, err := io.ReadAll(sig)
if err != nil {
return fmt.Errorf("reading signature: %w", err)
}
return h.client.verify(sigBytes, digest, hf, opts...)
}
// CreateKey attempts to create a new key in Vault with the specified algorithm.
func (h SignerVerifier) CreateKey(_ context.Context, algorithm string) (crypto.PublicKey, error) {
return h.client.createKey(algorithm)
}
type cryptoSignerWrapper struct {
ctx context.Context
hashFunc crypto.Hash
sv *SignerVerifier
errFunc func(error)
}
func (c cryptoSignerWrapper) Public() crypto.PublicKey {
pk, err := c.sv.PublicKey(options.WithContext(c.ctx))
if err != nil && c.errFunc != nil {
c.errFunc(err)
}
return pk
}
func (c cryptoSignerWrapper) Sign(_ io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
hashFunc := c.hashFunc
if opts != nil {
hashFunc = opts.HashFunc()
}
hvOptions := []signature.SignOption{
options.WithContext(c.ctx),
options.WithDigest(digest),
options.WithCryptoSignerOpts(hashFunc),
}
return c.sv.SignMessage(nil, hvOptions...)
}
// CryptoSigner returns a crypto.Signer object that uses the underlying SignerVerifier, along with a crypto.SignerOpts object
// that allows the KMS to be used in APIs that only accept the standard golang objects
func (h *SignerVerifier) CryptoSigner(ctx context.Context, errFunc func(error)) (crypto.Signer, crypto.SignerOpts, error) {
csw := &cryptoSignerWrapper{
ctx: ctx,
sv: h,
hashFunc: h.hashFunc,
errFunc: errFunc,
}
return csw, h.hashFunc, nil
}
// SupportedAlgorithms returns the list of algorithms supported by the Hashicorp Vault service
func (h *SignerVerifier) SupportedAlgorithms() []string {
return hvSupportedAlgorithms
}
// DefaultAlgorithm returns the default algorithm for the Hashicorp Vault service
func (h *SignerVerifier) DefaultAlgorithm() string {
return AlgorithmECDSAP256
}
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