Function certificateRequestInfoFromMsg

handshake_client.go:1207–1269

certificateRequestInfoFromMsg generates a CertificateRequestInfo from a TLS <= 1.2 CertificateRequest, making an effort to fill in missing information.

(ctx context.Context, vers uint16, certReq *certificateRequestMsg)

// certificateRequestInfoFromMsg generates a CertificateRequestInfo from a TLS
// <= 1.2 CertificateRequest, making an effort to fill in missing information.
func certificateRequestInfoFromMsg(ctx context.Context, vers uint16, certReq *certificateRequestMsg) *CertificateRequestInfo {
	cri := &CertificateRequestInfo{
		AcceptableCAs: certReq.certificateAuthorities,
		Version:       vers,
		ctx:           ctx,
	}

	var rsaAvail, ecAvail bool
	for _, certType := range certReq.certificateTypes {
		switch certType {
		case certTypeRSASign:
			rsaAvail = true
		case certTypeECDSASign:
			ecAvail = true
		}
	}

	if !certReq.hasSignatureAlgorithm {
		// Prior to TLS 1.2, signature schemes did not exist. In this case we
		// make up a list based on the acceptable certificate types, to help
		// GetClientCertificate and SupportsCertificate select the right certificate.
		// The hash part of the SignatureScheme is a lie here, because
		// TLS 1.0 and 1.1 always use MD5+SHA1 for RSA and SHA1 for ECDSA.
		switch {
		case rsaAvail && ecAvail:
			cri.SignatureSchemes = []SignatureScheme{
				ECDSAWithP256AndSHA256, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512,
				PKCS1WithSHA256, PKCS1WithSHA384, PKCS1WithSHA512, PKCS1WithSHA1,
			}
		case rsaAvail:
			cri.SignatureSchemes = []SignatureScheme{
				PKCS1WithSHA256, PKCS1WithSHA384, PKCS1WithSHA512, PKCS1WithSHA1,
			}
		case ecAvail:
			cri.SignatureSchemes = []SignatureScheme{
				ECDSAWithP256AndSHA256, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512,
			}
		}
		return cri
	}

	// Filter the signature schemes based on the certificate types.
	// See RFC 5246, Section 7.4.4 (where it calls this "somewhat complicated").
	cri.SignatureSchemes = make([]SignatureScheme, 0, len(certReq.supportedSignatureAlgorithms))
	for _, sigScheme := range certReq.supportedSignatureAlgorithms {
		sigType, _, err := typeAndHashFromSignatureScheme(sigScheme)
		if err != nil {
			continue
		}
		switch sigType {
		case signatureECDSA, signatureEd25519:
			if ecAvail {
				cri.SignatureSchemes = append(cri.SignatureSchemes, sigScheme)
			}
		case signatureRSAPSS, signaturePKCS1v15:
			if rsaAvail {
				cri.SignatureSchemes = append(cri.SignatureSchemes, sigScheme)
			}