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// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT
package dtls
import (
"bytes"
"crypto/tls"
"crypto/x509"
"fmt"
"strings"
"github.com/pion/dtls/v3/pkg/protocol/handshake"
)
// ClientHelloInfo contains information from a ClientHello message in order to
// guide application logic in the GetCertificate.
type ClientHelloInfo struct {
// ServerName indicates the name of the server requested by the client
// in order to support virtual hosting. ServerName is only set if the
// client is using SNI (see RFC 4366, Section 3.1).
ServerName string
// CipherSuites lists the CipherSuites supported by the client (e.g.
// TLS_AES_128_GCM_SHA256, TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256).
CipherSuites []CipherSuiteID
// RandomBytes stores the client hello random bytes
RandomBytes [handshake.RandomBytesLength]byte
}
// CertificateRequestInfo contains information from a server's
// CertificateRequest message, which is used to demand a certificate and proof
// of control from a client.
type CertificateRequestInfo struct {
// AcceptableCAs contains zero or more, DER-encoded, X.501
// Distinguished Names. These are the names of root or intermediate CAs
// that the server wishes the returned certificate to be signed by. An
// empty slice indicates that the server has no preference.
AcceptableCAs [][]byte
}
// SupportsCertificate returns nil if the provided certificate is supported by
// the server that sent the CertificateRequest. Otherwise, it returns an error
// describing the reason for the incompatibility.
// NOTE: original src:
// https://github.com/golang/go/blob/29b9a328d268d53833d2cc063d1d8b4bf6852675/src/crypto/tls/common.go#L1273
func (cri *CertificateRequestInfo) SupportsCertificate(c *tls.Certificate) error {
if len(cri.AcceptableCAs) == 0 {
return nil
}
for j, cert := range c.Certificate {
x509Cert := c.Leaf
// Parse the certificate if this isn't the leaf node, or if
// chain.Leaf was nil.
if j != 0 || x509Cert == nil {
var err error
if x509Cert, err = x509.ParseCertificate(cert); err != nil {
return fmt.Errorf("failed to parse certificate #%d in the chain: %w", j, err)
}
}
for _, ca := range cri.AcceptableCAs {
if bytes.Equal(x509Cert.RawIssuer, ca) {
return nil
}
}
}
return errNotAcceptableCertificateChain
}
func (c *handshakeConfig) setNameToCertificateLocked() {
nameToCertificate := make(map[string]*tls.Certificate)
for i := range c.localCertificates {
cert := &c.localCertificates[i]
x509Cert := cert.Leaf
if x509Cert == nil {
var parseErr error
x509Cert, parseErr = x509.ParseCertificate(cert.Certificate[0])
if parseErr != nil {
continue
}
}
if len(x509Cert.Subject.CommonName) > 0 {
nameToCertificate[strings.ToLower(x509Cert.Subject.CommonName)] = cert
}
for _, san := range x509Cert.DNSNames {
nameToCertificate[strings.ToLower(san)] = cert
}
}
c.nameToCertificate = nameToCertificate
}
//nolint:cyclop
func (c *handshakeConfig) getCertificate(clientHelloInfo *ClientHelloInfo) (*tls.Certificate, error) {
c.mu.Lock()
defer c.mu.Unlock()
if c.localGetCertificate != nil &&
(len(c.localCertificates) == 0 || len(clientHelloInfo.ServerName) > 0) {
cert, err := c.localGetCertificate(clientHelloInfo)
if cert != nil || err != nil {
return cert, err
}
}
if c.nameToCertificate == nil {
c.setNameToCertificateLocked()
}
if len(c.localCertificates) == 0 {
return nil, errNoCertificates
}
if len(c.localCertificates) == 1 {
// There's only one choice, so no point doing any work.
return &c.localCertificates[0], nil
}
if len(clientHelloInfo.ServerName) == 0 {
return &c.localCertificates[0], nil
}
name := strings.TrimRight(strings.ToLower(clientHelloInfo.ServerName), ".")
if cert, ok := c.nameToCertificate[name]; ok {
return cert, nil
}
// try replacing labels in the name with wildcards until we get a
// match.
labels := strings.Split(name, ".")
for i := range labels {
labels[i] = "*"
candidate := strings.Join(labels, ".")
if cert, ok := c.nameToCertificate[candidate]; ok {
return cert, nil
}
}
// If nothing matches, return the first certificate.
return &c.localCertificates[0], nil
}
// NOTE: original src:
// https://github.com/golang/go/blob/29b9a328d268d53833d2cc063d1d8b4bf6852675/src/crypto/tls/handshake_client.go#L974
func (c *handshakeConfig) getClientCertificate(cri *CertificateRequestInfo) (*tls.Certificate, error) {
c.mu.Lock()
defer c.mu.Unlock()
if c.localGetClientCertificate != nil {
return c.localGetClientCertificate(cri)
}
for i := range c.localCertificates {
chain := c.localCertificates[i]
if err := cri.SupportsCertificate(&chain); err != nil {
continue
}
return &chain, nil
}
// No acceptable certificate found. Don't send a certificate.
return new(tls.Certificate), nil
}
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