110 lines
2.6 KiB
Go
110 lines
2.6 KiB
Go
// Copyright (C) 2018 Storj Labs, Inc.
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// See LICENSE for copying information.
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package peertls
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// Many cryptography standards use ASN.1 to define their data structures,
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// and Distinguished Encoding Rules (DER) to serialize those structures.
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// Because DER produces binary output, it can be challenging to transmit
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// the resulting files through systems, like electronic mail, that only
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// support ASCII. The PEM format solves this problem by encoding the
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// binary data using base64.
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// (see https://en.wikipedia.org/wiki/Privacy-enhanced_Electronic_Mail)
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import (
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"crypto"
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"crypto/ecdsa"
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"crypto/elliptic"
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"crypto/rand"
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"crypto/x509"
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"encoding/asn1"
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"math/big"
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"github.com/zeebo/errs"
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)
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type ecdsaSignature struct {
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R, S *big.Int
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}
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var authECCurve = elliptic.P256()
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func parseCertificateChains(rawCerts [][]byte) ([]*x509.Certificate, error) {
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parsedCerts, err := parseCerts(rawCerts)
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if err != nil {
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return nil, err
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}
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return parsedCerts, nil
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}
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func parseCerts(rawCerts [][]byte) ([]*x509.Certificate, error) {
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certs := make([]*x509.Certificate, len(rawCerts))
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for i, c := range rawCerts {
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var err error
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certs[i], err = x509.ParseCertificate(c)
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if err != nil {
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return nil, ErrParseCerts.New("unable to parse certificate at index %d", i)
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}
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}
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return certs, nil
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}
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func verifyChainSignatures(certs []*x509.Certificate) error {
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for i, cert := range certs {
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j := len(certs)
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if i+1 < j {
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err := verifyCertSignature(certs[i+1], cert)
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if err != nil {
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return ErrVerifyCertificateChain.Wrap(err)
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}
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continue
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}
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err := verifyCertSignature(cert, cert)
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if err != nil {
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return ErrVerifyCertificateChain.Wrap(err)
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}
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}
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return nil
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}
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func verifyCertSignature(parentCert, childCert *x509.Certificate) error {
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pubKey, ok := parentCert.PublicKey.(*ecdsa.PublicKey)
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if !ok {
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return ErrUnsupportedKey.New("%T", parentCert.PublicKey)
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}
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signature := new(ecdsaSignature)
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if _, err := asn1.Unmarshal(childCert.Signature, signature); err != nil {
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return ErrVerifySignature.New("unable to unmarshal ecdsa signature: %v", err)
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}
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h := crypto.SHA256.New()
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_, err := h.Write(childCert.RawTBSCertificate)
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if err != nil {
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return ErrVerifySignature.Wrap(err)
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}
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digest := h.Sum(nil)
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if !ecdsa.Verify(pubKey, digest, signature.R, signature.S) {
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return ErrVerifySignature.New("signature is not valid")
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}
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return nil
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}
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func newSerialNumber() (*big.Int, error) {
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serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
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serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
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if err != nil {
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return nil, errs.New("failed to generateServerTls serial number: %s", err.Error())
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}
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return serialNumber, nil
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}
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