etcdserver: cherry-pick skip client san verification option for 3.3 version.

Co-authored-by: Martin Weindel <martin.weindel@sap.com>
Co-authored-by: Jingyi Hu <jingyih@google.com>
Co-authored-by: Liming Liu <andyliuliming@outlook.com>

etcdmain/config.go

@@ -189,6 +189,7 @@ func newConfig() *config {
 	fs.BoolVar(&cfg.ec.PeerAutoTLS, "peer-auto-tls", false, "Peer TLS using generated certificates")
 	fs.StringVar(&cfg.ec.PeerTLSInfo.CRLFile, "peer-crl-file", "", "Path to the peer certificate revocation list file.")
 	fs.StringVar(&cfg.ec.PeerTLSInfo.AllowedCN, "peer-cert-allowed-cn", "", "Allowed CN for inter peer authentication.")
+	fs.BoolVar(&cfg.ec.PeerTLSInfo.SkipClientSANVerify, "experimental-peer-skip-client-san-verification", false, "Skip verification of SAN field in client certificate for peer connections.")
 
 	fs.Var(flags.NewStringsValueV2(""), "cipher-suites", "Comma-separated list of supported TLS cipher suites between client/server and peers (empty will be auto-populated by Go).")
 

pkg/transport/listener.go

@@ -53,6 +53,9 @@ func wrapTLS(addr, scheme string, tlsinfo *TLSInfo, l net.Listener) (net.Listene
 	if scheme != "https" && scheme != "unixs" {
 		return l, nil
 	}
+	if tlsinfo != nil && tlsinfo.SkipClientSANVerify {
+		return NewTLSListener(l, tlsinfo)
+	}
 	return newTLSListener(l, tlsinfo, checkSAN)
 }
 
@@ -65,6 +68,8 @@ type TLSInfo struct {
 	CRLFile            string
 	InsecureSkipVerify bool
 
+	SkipClientSANVerify bool
+
 	// ServerName ensures the cert matches the given host in case of discovery / virtual hosting
 	ServerName string