Date: Mon, 23 May 2016 17:06:13 +0200 From: "Luis M. Merino" <luismiguelmerino@...il.com> To: oss-security@...ts.openwall.com Subject: CVE request: OpenNTPD not verifying CN during HTTPS constraints request Good afternoon, I'm requesting a CVE for this patched mitm mitigation bypass vulnerability on OpenNTPD. Upstream patch: http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/ntpd/constraint.c.diff?r1=1.27&r2=1.28 Affected versions: All OpenNTPD versions containing constraints before May 21st 2016 are affected. OpenBSD 5.9 is affected. Description: OpenNTPD constraints is an experimental functionality to mitigate NTP man-in-the-middle attacks. When enabled (by default on OpenBSD base install), it request timestamps from trusted HTTPS servers through HTTP Date: header and the average of the values obtained are used to filter out deviating NTP responses. Common Name verification was disabled while configuring the HTTPS request, allowing upstream network attackers to intercept and forward the request to a malicious server that could provide forged timestamp constraints presenting valid certificates without the server noticing it. The vulnerable function is httpsdate_init at /src/usr.sbin/ntpd/constraint.c on OpenBSD source: [...] /* XXX we have to pre-resolve, so name and host are not equal */ tls_config_insecure_noverifyname(httpsdate->tls_config); [...] Solution: Update to -CURRENT. Regards, Luis M. Merino
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