Bypass of client certificate verification with transfer over TLS

Summary

When a provide-xfr is given with a tls-auth-name, a secondary requesting a transfer should provide a client certificate with that name. However, no client certificate is needed when the request comes in over TLS over the regular tls-port (and not the tls-auth-port) or over over TCP over the regular port, when the other conditions of the provide-xfr rule match. A flaw was found in nsd. This authentication bypass allows an attacker to perform unauthorized zone transfers, leading to information disclosure. This flaw is rated as Moderate. This allows unauthorized zone transfers and information disclosure if requests are made over the regular TLS or TCP port, as the `tls-auth-xfr-only` option is not enabled by default. This vulnerability doesn't affect any supported Red Hat Product. Red Hat severity: Moderate — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N). Weakness: CWE-303.