Etcd Gateway TLS authentication only applies to endpoints detected in DNS SRV records

### Vulnerability type Cryptography

### Workarounds Refer to the [gateway documentation](https://github.com/etcd-io/etcd/blob/master/Documentation/op-guide/gateway.md). The vulnerability was spotted due to unclear documentation of how the gateway handles endpoints validation.

### Detail When starting a gateway, TLS authentication will only be attempted on endpoints identified in DNS SRV records for a given domain, which occurs in the discoverEndpoints function. No authentication is performed against endpoints provided in the --endpoints flag. The auditors has noted that appropriate documentation of this validation functionality plus deprecation of this misleading functionality is an acceptable path forward. ### References Find out more on this vulnerability in the [security audit report](https://github.com/etcd-io/etcd/blob/master/security/SECURITY_AUDIT.pdf)

### For more information If you have any questions or comments about this advisory: * Contact the [etcd security committee](https://github.com/etcd-io/etcd/blob/master/security/security-release-process.md#product-security-committee-psc)