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.TH TLSDATE 1 "OCTOBER 2012" Linux "User Manuals"
tlsdate \- secure parasitic rdate replacement
.B tlsdate [\-hnvVstlw] [\-H [hostname]] [\-p [port]] [\-P [sslv23|sslv3|tlsv1]] \
[\-\-certdir [dirname]] [\-x [\-\-proxy] proxy\-type://proxyhost:proxyport]
.B tlsdate
is a tool for setting the system clock by hand or by communication
with the network. It does not set the Real Time Clock. It is designed to be as
secure as TLS (RFC 2246) but of course the security of TLS is often reduced to
whichever CA racket you believe is trustworthy. By default, tlsdate trusts your
local CA root store - so any of these companies could assist in a MITM attack
against you and you'd be screwed.
This tool is designed to be run by hand or as a system daemon. It must be
run as root or otherwise have the proper caps; it will not be able to set
the system time without running as root or another privileged user.
.IP "\-h | \-\-help"
Print the help message
.IP "\-s | \-\-skip\-verification"
Skip certificate verification
.IP "\-H | \-\-host [hostname|ip]"
Set remote hostname (default: '')
.IP "\-n | \-\-dont\-set\-clock"
Do not set the system clock to the time of the remote server
.IP "\-p | \-\-port [port]"
Set remote port (default: '443')
.IP "\-P | \-\-protocol [sslv23|sslv3|tlsv1]"
Set protocol to use when communicating with server (default: 'tlsv1')
.IP "\-C | \-\-certdir [dirname]"
Set the local directory where certificates are located
(default: '/etc/ssl/certs')
This allows for certificate or certificate authority (CA) pinning. To ensure
that signatures are only valid if they are signed by a specific CA or
certificate, set the path to a directory containing only the desired
.IP "\-x | \-\-proxy [proxy\-type://proxyhost:proxyport]"
The proxy argument expects HTTP, SOCKS4A or SOCKS5 formatted as followed:
The proxy support should not leak DNS requests and is suitable for use with Tor.
.IP "\-v | \-\-verbose"
Provide verbose output
.IP "\-V | \-\-showtime [human|raw]"
Show the time retrieved from the remote server in a human-readable format or as
a raw time_t.
.IP "\-t | \-\-timewarp"
If the local clock is before RECENT_COMPILE_DATE; we set the clock to the
RECENT_COMPILE_DATE. If the local clock is after RECENT_COMPILE_DATE, we leave
the clock alone. Clock setting is performed as the first operation and will
impact certificate verification. Specifically, this option is helpful if on
first boot, the local system clock is set back to the era of Disco and Terrible
Hair. This should ensure that X509_V_ERR_CERT_NOT_YET_VALID or
X509_V_ERR_CERT_HAS_EXPIRED are not encountered because of a broken RTC or the
lack of a local RTC; we assume that tlsdate is recompiled yearly and that all
certificates are otherwise considered valid.
.IP "\-l | \-\-leap"
Normally, the passing of time or time yet to come ensures that SSL verify
functions will fail to validate certificates. Commonly,
annoying but still very important error states. When the only issue with the
certificates in question is the timing information, this option allows you to
trust the remote system's time, as long as it is after RECENT_COMPILE_DATE and
before MAX_REASONABLE_TIME. The connection will only be trusted if
the only errors encountered. The SSL verify function will not return X509_V_OK
if there are any other issues, such as self-signed certificates or if the user
pins to a CA that is not used by the remote server. This is useful if your RTC
is broken on boot and you are unable to use DNSEC until you've at least had
some kind of leap of cryptographically assured data.
.IP "\-w | \-\-http"
Run in web mode: look for the time in an HTTP "Date" header inside an
HTTPS connection, rather than in the TLS connection itself. The provided
hostname and port must support HTTPS.
It's likely! Let us know by contacting
Note that
.B tlsdate(1)
is in Beta, and may not work as expected.
Jacob Appelbaum <jacob at appelbaum dot net>
.B tlsdate(1),
.B tlsdate-helper(1),
.B tlsdated(8),
.B tlsdated.conf(5)