I'll just paste the relevant stuff here:
#
banner stuff
[org/gnome/login-screen]
banner-message-enable=true
banner-message-text='You are accessing a U.S. Government
(USG) Information System (IS) that is provided for
USG-authorized use only. By using this IS (which includes
any device attached to this IS), you consent to the
following conditions:\n -The USG routinely intercepts and
monitors communications on this IS for purposes including,
but not limited to, penetration testing, COMSEC
monitoring, network operations and defense, personnel
misconduct (PM), law enforcement (LE), and
counterintelligence (CI) investigations.\n -At any time,
the USG may inspect and seize data stored on this IS.\n
-Communications using, or data stored on, this IS are not
private, are subject to routine monitoring, interception,
and search, and may be disclosed or used for any
USG-authorized purpose.\n -This IS includes security
measures (e.g., authentication and access controls) to
protect USG interests -- not for your personal benefit or
privacy.\n -Notwithstanding the above, using this IS does
not constitute consent to PM, LE or CI investigative
searching or monitoring of the content of privileged
communications, or work product, related to personal
representation or services by attorneys, psychotherapists,
or clergy, and their assistants. Such communications and
work product are private and confidential. See User
Agreement for details.'
#
don't show lists of users on login screen
disable-user-list=true
#
disable fingerprint reader
enable-fingerprint-authentication=false
By my count it's 1311 characters, but that's probably not
treating the \n's as a single character. FWIW, this is our
approved "short" version of the banner.