xref: /freebsd-9.3-release/usr.sbin/ntp/doc/ntp-keygen.8

.Dd November 21 2016
.Dt NTP_KEYGEN 8 User Commands
.Os
.\"  EDIT THIS FILE WITH CAUTION  (ntp-keygen-opts.mdoc)
.\"
.\" $FreeBSD: releng/9.3/usr.sbin/ntp/doc/ntp-keygen.8 310419 2016-12-22 16:19:05Z delphij $
.\"
.\"  It has been AutoGen-ed  November 21, 2016 at 08:03:48 AM by AutoGen 5.18.5
.\"  From the definitions    ntp-keygen-opts.def
.\"  and the template file   agmdoc-cmd.tpl
.Sh NAME
.Nm ntp-keygen
.Nd Create a NTP host key
.Sh SYNOPSIS
.Nm
.\" Mixture of short (flag) options and long options
.Op Fl flags
.Op Fl flag Op Ar value
.Op Fl \-option\-name Ns Oo Oo Ns "=| " Oc Ns Ar value Oc
.Pp
All arguments must be options.
.Pp
.Sh DESCRIPTION
This program generates cryptographic data files used by the NTPv4
authentication and identification schemes.
It generates MD5 key files used in symmetric key cryptography.
In addition, if the OpenSSL software library has been installed,
it generates keys, certificate and identity files used in public key
cryptography.
These files are used for cookie encryption,
digital signature and challenge/response identification algorithms
compatible with the Internet standard security infrastructure.
.Pp
All files are in PEM\-encoded printable ASCII format,
so they can be embedded as MIME attachments in mail to other sites
and certificate authorities.
By default, files are not encrypted.
.Pp
When used to generate message digest keys, the program produces a file
containing ten pseudo\-random printable ASCII strings suitable for the
MD5 message digest algorithm included in the distribution.
If the OpenSSL library is installed, it produces an additional ten
hex\-encoded random bit strings suitable for the SHA1 and other message
digest algorithms.
The message digest keys file must be distributed and stored
using secure means beyond the scope of NTP itself.
Besides the keys used for ordinary NTP associations, additional keys
can be defined as passwords for the
.Xr ntpq 8
and
.Xr ntpdc 8
utility programs.
.Pp
The remaining generated files are compatible with other OpenSSL
applications and other Public Key Infrastructure (PKI) resources.
Certificates generated by this program are compatible with extant
industry practice, although some users might find the interpretation of
X509v3 extension fields somewhat liberal.
However, the identity keys are probably not compatible with anything
other than Autokey.
.Pp
Some files used by this program are encrypted using a private password.
The
.Fl p
option specifies the password for local encrypted files and the
.Fl q
option the password for encrypted files sent to remote sites.
If no password is specified, the host name returned by the Unix
.Fn gethostname
function, normally the DNS name of the host is used.
.Pp
The
.Ar pw
option of the
.Ar crypto
configuration command specifies the read
password for previously encrypted local files.
This must match the local password used by this program.
If not specified, the host name is used.
Thus, if files are generated by this program without password,
they can be read back by
.Ar ntpd
without password but only on the same host.
.Pp
Normally, encrypted files for each host are generated by that host and
used only by that host, although exceptions exist as noted later on
this page.
The symmetric keys file, normally called
.Ar ntp.keys ,
is usually installed in
.Pa /etc .
Other files and links are usually installed in
.Pa /usr/local/etc ,
which is normally in a shared filesystem in
NFS\-mounted networks and cannot be changed by shared clients.
The location of the keys directory can be changed by the
.Ar keysdir
configuration command in such cases.
Normally, this is in
.Pa /etc .
.Pp
This program directs commentary and error messages to the standard
error stream
.Ar stderr
and remote files to the standard output stream
.Ar stdout
where they can be piped to other applications or redirected to files.
The names used for generated files and links all begin with the
string
.Ar ntpkey
and include the file type, generating host and filestamp,
as described in the
.Dq Cryptographic Data Files
section below.
.Ss Running the Program
To test and gain experience with Autokey concepts, log in as root and
change to the keys directory, usually
.Pa /usr/local/etc 
When run for the first time, or if all files with names beginning with
.Ar ntpkey
have been removed, use the
.Nm
command without arguments to generate a
default RSA host key and matching RSA\-MD5 certificate with expiration
date one year hence.
If run again without options, the program uses the
existing keys and parameters and generates only a new certificate with
new expiration date one year hence.
.Pp
Run the command on as many hosts as necessary.
Designate one of them as the trusted host (TH) using
.Nm
with the
.Fl T
option and configure it to synchronize from reliable Internet servers.
Then configure the other hosts to synchronize to the TH directly or
indirectly.
A certificate trail is created when Autokey asks the immediately
ascendant host towards the TH to sign its certificate, which is then
provided to the immediately descendant host on request.
All group hosts should have acyclic certificate trails ending on the TH.
.Pp
The host key is used to encrypt the cookie when required and so must be
RSA type.
By default, the host key is also the sign key used to encrypt
signatures.
A different sign key can be assigned using the
.Fl S
option and this can be either RSA or DSA type.
By default, the signature
message digest type is MD5, but any combination of sign key type and
message digest type supported by the OpenSSL library can be specified
using the
.Fl c
option.
The rules say cryptographic media should be generated with proventic
filestamps, which means the host should already be synchronized before
this program is run.
This of course creates a chicken\-and\-egg problem
when the host is started for the first time.
Accordingly, the host time
should be set by some other means, such as eyeball\-and\-wristwatch, at
least so that the certificate lifetime is within the current year.
After that and when the host is synchronized to a proventic source, the
certificate should be re\-generated.
.Pp
Additional information on trusted groups and identity schemes is on the
.Dq Autokey Public\-Key Authentication
page.
.Pp
The
.Xr ntpd 8
configuration command
.Ic crypto pw Ar password
specifies the read password for previously encrypted files.
The daemon expires on the spot if the password is missing
or incorrect.
For convenience, if a file has been previously encrypted,
the default read password is the name of the host running
the program.
If the previous write password is specified as the host name,
these files can be read by that host with no explicit password.
.Pp
File names begin with the prefix
.Cm ntpkey_
and end with the postfix
.Ar _hostname.filestamp ,
where
.Ar hostname
is the owner name, usually the string returned
by the Unix gethostname() routine, and
.Ar filestamp
is the NTP seconds when the file was generated, in decimal digits.
This both guarantees uniqueness and simplifies maintenance
procedures, since all files can be quickly removed
by a
.Ic rm ntpkey\&*
command or all files generated
at a specific time can be removed by a
.Ic rm
.Ar \&*filestamp
command.
To further reduce the risk of misconfiguration,
the first two lines of a file contain the file name
and generation date and time as comments.
.Pp
All files are installed by default in the keys directory
.Pa /usr/local/etc ,
which is normally in a shared filesystem
in NFS\-mounted networks.
The actual location of the keys directory
and each file can be overridden by configuration commands,
but this is not recommended.
Normally, the files for each host are generated by that host
and used only by that host, although exceptions exist
as noted later on this page.
.Pp
Normally, files containing private values,
including the host key, sign key and identification parameters,
are permitted root read/write\-only;
while others containing public values are permitted world readable.
Alternatively, files containing private values can be encrypted
and these files permitted world readable,
which simplifies maintenance in shared file systems.
Since uniqueness is insured by the hostname and
file name extensions, the files for a NFS server and
dependent clients can all be installed in the same shared directory.
.Pp
The recommended practice is to keep the file name extensions
when installing a file and to install a soft link
from the generic names specified elsewhere on this page
to the generated files.
This allows new file generations to be activated simply
by changing the link.
If a link is present, ntpd follows it to the file name
to extract the filestamp.
If a link is not present,
.Xr ntpd 8
extracts the filestamp from the file itself.
This allows clients to verify that the file and generation times
are always current.
The
.Nm
program uses the same timestamp extension for all files generated
at one time, so each generation is distinct and can be readily
recognized in monitoring data.
.Ss Running the program
The safest way to run the
.Nm
program is logged in directly as root.
The recommended procedure is change to the keys directory,
usually
.Pa /usr/local/etc ,
then run the program.
When run for the first time,
or if all
.Cm ntpkey
files have been removed,
the program generates a RSA host key file and matching RSA\-MD5 certificate file,
which is all that is necessary in many cases.
The program also generates soft links from the generic names
to the respective files.
If run again, the program uses the same host key file,
but generates a new certificate file and link.
.Pp
The host key is used to encrypt the cookie when required and so must be RSA type.
By default, the host key is also the sign key used to encrypt signatures.
When necessary, a different sign key can be specified and this can be
either RSA or DSA type.
By default, the message digest type is MD5, but any combination
of sign key type and message digest type supported by the OpenSSL library
can be specified, including those using the MD2, MD5, SHA, SHA1, MDC2
and RIPE160 message digest algorithms.
However, the scheme specified in the certificate must be compatible
with the sign key.
Certificates using any digest algorithm are compatible with RSA sign keys;
however, only SHA and SHA1 certificates are compatible with DSA sign keys.
.Pp
Private/public key files and certificates are compatible with
other OpenSSL applications and very likely other libraries as well.
Certificates or certificate requests derived from them should be compatible
with extant industry practice, although some users might find
the interpretation of X509v3 extension fields somewhat liberal.
However, the identification parameter files, although encoded
as the other files, are probably not compatible with anything other than Autokey.
.Pp
Running the program as other than root and using the Unix
.Ic su
command
to assume root may not work properly, since by default the OpenSSL library
looks for the random seed file
.Cm .rnd
in the user home directory.
However, there should be only one
.Cm .rnd ,
most conveniently
in the root directory, so it is convenient to define the
.Cm $RANDFILE
environment variable used by the OpenSSL library as the path to
.Cm /.rnd .
.Pp
Installing the keys as root might not work in NFS\-mounted
shared file systems, as NFS clients may not be able to write
to the shared keys directory, even as root.
In this case, NFS clients can specify the files in another
directory such as
.Pa /etc
using the
.Ic keysdir
command.
There is no need for one client to read the keys and certificates
of other clients or servers, as these data are obtained automatically
by the Autokey protocol.
.Pp
Ordinarily, cryptographic files are generated by the host that uses them,
but it is possible for a trusted agent (TA) to generate these files
for other hosts; however, in such cases files should always be encrypted.
The subject name and trusted name default to the hostname
of the host generating the files, but can be changed by command line options.
It is convenient to designate the owner name and trusted name
as the subject and issuer fields, respectively, of the certificate.
The owner name is also used for the host and sign key files,
while the trusted name is used for the identity files.
.Pp
All files are installed by default in the keys directory
.Pa /usr/local/etc ,
which is normally in a shared filesystem
in NFS\-mounted networks.
The actual location of the keys directory
and each file can be overridden by configuration commands,
but this is not recommended.
Normally, the files for each host are generated by that host
and used only by that host, although exceptions exist
as noted later on this page.
.Pp
Normally, files containing private values,
including the host key, sign key and identification parameters,
are permitted root read/write\-only;
while others containing public values are permitted world readable.
Alternatively, files containing private values can be encrypted
and these files permitted world readable,
which simplifies maintenance in shared file systems.
Since uniqueness is insured by the hostname and
file name extensions, the files for a NFS server and
dependent clients can all be installed in the same shared directory.
.Pp
The recommended practice is to keep the file name extensions
when installing a file and to install a soft link
from the generic names specified elsewhere on this page
to the generated files.
This allows new file generations to be activated simply
by changing the link.
If a link is present, ntpd follows it to the file name
to extract the filestamp.
If a link is not present,
.Xr ntpd 8
extracts the filestamp from the file itself.
This allows clients to verify that the file and generation times
are always current.
The
.Nm
program uses the same timestamp extension for all files generated
at one time, so each generation is distinct and can be readily
recognized in monitoring data.
.Ss Running the program
The safest way to run the
.Nm
program is logged in directly as root.
The recommended procedure is change to the keys directory,
usually
.Pa /usr/local/etc ,
then run the program.
When run for the first time,
or if all
.Cm ntpkey
files have been removed,
the program generates a RSA host key file and matching RSA\-MD5 certificate file,
which is all that is necessary in many cases.
The program also generates soft links from the generic names
to the respective files.
If run again, the program uses the same host key file,
but generates a new certificate file and link.
.Pp
The host key is used to encrypt the cookie when required and so must be RSA type.
By default, the host key is also the sign key used to encrypt signatures.
When necessary, a different sign key can be specified and this can be
either RSA or DSA type.
By default, the message digest type is MD5, but any combination
of sign key type and message digest type supported by the OpenSSL library
can be specified, including those using the MD2, MD5, SHA, SHA1, MDC2
and RIPE160 message digest algorithms.
However, the scheme specified in the certificate must be compatible
with the sign key.
Certificates using any digest algorithm are compatible with RSA sign keys;
however, only SHA and SHA1 certificates are compatible with DSA sign keys.
.Pp
Private/public key files and certificates are compatible with
other OpenSSL applications and very likely other libraries as well.
Certificates or certificate requests derived from them should be compatible
with extant industry practice, although some users might find
the interpretation of X509v3 extension fields somewhat liberal.
However, the identification parameter files, although encoded
as the other files, are probably not compatible with anything other than Autokey.
.Pp
Running the program as other than root and using the Unix
.Ic su
command
to assume root may not work properly, since by default the OpenSSL library
looks for the random seed file
.Cm .rnd
in the user home directory.
However, there should be only one
.Cm .rnd ,
most conveniently
in the root directory, so it is convenient to define the
.Cm $RANDFILE
environment variable used by the OpenSSL library as the path to
.Cm /.rnd .
.Pp
Installing the keys as root might not work in NFS\-mounted
shared file systems, as NFS clients may not be able to write
to the shared keys directory, even as root.
In this case, NFS clients can specify the files in another
directory such as
.Pa /etc
using the
.Ic keysdir
command.
There is no need for one client to read the keys and certificates
of other clients or servers, as these data are obtained automatically
by the Autokey protocol.
.Pp
Ordinarily, cryptographic files are generated by the host that uses them,
but it is possible for a trusted agent (TA) to generate these files
for other hosts; however, in such cases files should always be encrypted.
The subject name and trusted name default to the hostname
of the host generating the files, but can be changed by command line options.
It is convenient to designate the owner name and trusted name
as the subject and issuer fields, respectively, of the certificate.
The owner name is also used for the host and sign key files,
while the trusted name is used for the identity files.
seconds.
seconds.
s Trusted Hosts and Groups
Each cryptographic configuration involves selection of a signature scheme
and identification scheme, called a cryptotype,
as explained in the
.Sx Authentication Options
section of
.Xr ntp.conf 5 .
The default cryptotype uses RSA encryption, MD5 message digest
and TC identification.
First, configure a NTP subnet including one or more low\-stratum
trusted hosts from which all other hosts derive synchronization
directly or indirectly.
Trusted hosts have trusted certificates;
all other hosts have nontrusted certificates.
These hosts will automatically and dynamically build authoritative
certificate trails to one or more trusted hosts.
A trusted group is the set of all hosts that have, directly or indirectly,
a certificate trail ending at a trusted host.
The trail is defined by static configuration file entries
or dynamic means described on the
.Sx Automatic NTP Configuration Options
section of
.Xr ntp.conf 5 .
.Pp
On each trusted host as root, change to the keys directory.
To insure a fresh fileset, remove all
.Cm ntpkey
files.
Then run
.Nm
.Fl T
to generate keys and a trusted certificate.
On all other hosts do the same, but leave off the
.Fl T
flag to generate keys and nontrusted certificates.
When complete, start the NTP daemons beginning at the lowest stratum
and working up the tree.
It may take some time for Autokey to instantiate the certificate trails
throughout the subnet, but setting up the environment is completely automatic.
.Pp
If it is necessary to use a different sign key or different digest/signature
scheme than the default, run
.Nm
with the
.Fl S Ar type
option, where
.Ar type
is either
.Cm RSA
or
.Cm DSA .
The most often need to do this is when a DSA\-signed certificate is used.
If it is necessary to use a different certificate scheme than the default,
run
.Nm
with the
.Fl c Ar scheme
option and selected
.Ar scheme
as needed.
f
.Nm
is run again without these options, it generates a new certificate
using the same scheme and sign key.
.Pp
After setting up the environment it is advisable to update certificates
from time to time, if only to extend the validity interval.
Simply run
.Nm
with the same flags as before to generate new certificates
using existing keys.
However, if the host or sign key is changed,
.Xr ntpd 8
should be restarted.
When
.Xr ntpd 8
is restarted, it loads any new files and restarts the protocol.
Other dependent hosts will continue as usual until signatures are refreshed,
at which time the protocol is restarted.
.Ss Identity Schemes
As mentioned on the Autonomous Authentication page,
the default TC identity scheme is vulnerable to a middleman attack.
However, there are more secure identity schemes available,
including PC, IFF, GQ and MV described on the
.Qq Identification Schemes
page
(maybe available at
.Li http://www.eecis.udel.edu/%7emills/keygen.html ) .
These schemes are based on a TA, one or more trusted hosts
and some number of nontrusted hosts.
Trusted hosts prove identity using values provided by the TA,
while the remaining hosts prove identity using values provided
by a trusted host and certificate trails that end on that host.
The name of a trusted host is also the name of its sugroup
and also the subject and issuer name on its trusted certificate.
The TA is not necessarily a trusted host in this sense, but often is.
.Pp
In some schemes there are separate keys for servers and clients.
A server can also be a client of another server,
but a client can never be a server for another client.
In general, trusted hosts and nontrusted hosts that operate
as both server and client have parameter files that contain
both server and client keys.
Hosts that operate
only as clients have key files that contain only client keys.
.Pp
The PC scheme supports only one trusted host in the group.
On trusted host alice run
.Nm
.Fl P
.Fl p Ar password
to generate the host key file
.Pa ntpkey_RSAkey_ Ns Ar alice.filestamp
and trusted private certificate file
.Pa ntpkey_RSA\-MD5_cert_ Ns Ar alice.filestamp .
Copy both files to all group hosts;
they replace the files which would be generated in other schemes.
On each host bob install a soft link from the generic name
.Pa ntpkey_host_ Ns Ar bob
to the host key file and soft link
.Pa ntpkey_cert_ Ns Ar bob
to the private certificate file.
Note the generic links are on bob, but point to files generated
by trusted host alice.
In this scheme it is not possible to refresh
either the keys or certificates without copying them
to all other hosts in the group.
.Pp
For the IFF scheme proceed as in the TC scheme to generate keys
and certificates for all group hosts, then for every trusted host in the group,
generate the IFF parameter file.
On trusted host alice run
.Nm
.Fl T
.Fl I
.Fl p Ar password
to produce her parameter file
.Pa ntpkey_IFFpar_ Ns Ar alice.filestamp ,
which includes both server and client keys.
Copy this file to all group hosts that operate as both servers
and clients and install a soft link from the generic
.Pa ntpkey_iff_ Ns Ar alice
to this file.
If there are no hosts restricted to operate only as clients,
there is nothing further to do.
As the IFF scheme is independent
of keys and certificates, these files can be refreshed as needed.
.Pp
If a rogue client has the parameter file, it could masquerade
as a legitimate server and present a middleman threat.
To eliminate this threat, the client keys can be extracted
from the parameter file and distributed to all restricted clients.
After generating the parameter file, on alice run
.Nm
.Fl e
and pipe the output to a file or mail program.
Copy or mail this file to all restricted clients.
On these clients install a soft link from the generic
.Pa ntpkey_iff_ Ns Ar alice
to this file.
To further protect the integrity of the keys,
each file can be encrypted with a secret password.
.Pp
For the GQ scheme proceed as in the TC scheme to generate keys
and certificates for all group hosts, then for every trusted host
in the group, generate the IFF parameter file.
On trusted host alice run
.Nm
.Fl T
.Fl G
.Fl p Ar password
to produce her parameter file
.Pa ntpkey_GQpar_ Ns Ar alice.filestamp ,
which includes both server and client keys.
Copy this file to all group hosts and install a soft link
from the generic
.Pa ntpkey_gq_ Ns Ar alice
to this file.
In addition, on each host bob install a soft link
from generic
.Pa ntpkey_gq_ Ns Ar bob
to this file.
As the GQ scheme updates the GQ parameters file and certificate
at the same time, keys and certificates can be regenerated as needed.
.Pp
For the MV scheme, proceed as in the TC scheme to generate keys
and certificates for all group hosts.
For illustration assume trish is the TA, alice one of several trusted hosts
and bob one of her clients.
On TA trish run
.Nm
.Fl V Ar n
.Fl p Ar password ,
where
.Ar n
is the number of revokable keys (typically 5) to produce
the parameter file
.Pa ntpkeys_MVpar_ Ns Ar trish.filestamp
and client key files
.Pa ntpkeys_MVkeyd_ Ns Ar trish.filestamp
where
.Ar d
is the key number (0 \&<
.Ar d
\&<
.Ar n ) .
Copy the parameter file to alice and install a soft link
from the generic
.Pa ntpkey_mv_ Ns Ar alice
to this file.
Copy one of the client key files to alice for later distribution
to her clients.
It doesn't matter which client key file goes to alice,
since they all work the same way.
Alice copies the client key file to all of her cliens.
On client bob install a soft link from generic
.Pa ntpkey_mvkey_ Ns Ar bob
to the client key file.
As the MV scheme is independent of keys and certificates,
these files can be refreshed as needed.
.Ss Command Line Options
.Bl -tag -width indent
.It Fl c Ar scheme
Select certificate message digest/signature encryption scheme.
The
.Ar scheme
can be one of the following:
. Cm RSA\-MD2 , RSA\-MD5 , RSA\-SHA , RSA\-SHA1 , RSA\-MDC2 , RSA\-RIPEMD160 , DSA\-SHA ,
or
.Cm DSA\-SHA1 .
Note that RSA schemes must be used with a RSA sign key and DSA
schemes must be used with a DSA sign key.
The default without this option is
.Cm RSA\-MD5 .
.It Fl d
Enable debugging.
This option displays the cryptographic data produced in eye\-friendly billboards.
.It Fl e
Write the IFF client keys to the standard output.
This is intended for automatic key distribution by mail.
.It Fl G
Generate parameters and keys for the GQ identification scheme,
obsoleting any that may exist.
.It Fl g
Generate keys for the GQ identification scheme
using the existing GQ parameters.
If the GQ parameters do not yet exist, create them first.
.It Fl H
Generate new host keys, obsoleting any that may exist.
.It Fl I
Generate parameters for the IFF identification scheme,
obsoleting any that may exist.
.It Fl i Ar name
Set the suject name to
.Ar name .
This is used as the subject field in certificates
and in the file name for host and sign keys.
.It Fl M
Generate MD5 keys, obsoleting any that may exist.
.It Fl P
Generate a private certificate.
By default, the program generates public certificates.
.It Fl p Ar password
Encrypt generated files containing private data with
.Ar password
and the DES\-CBC algorithm.
.It Fl q
Set the password for reading files to password.
.It Fl S Oo Cm RSA | DSA Oc
Generate a new sign key of the designated type,
obsoleting any that may exist.
By default, the program uses the host key as the sign key.
.It Fl s Ar name
Set the issuer name to
.Ar name .
This is used for the issuer field in certificates
and in the file name for identity files.
.It Fl T
Generate a trusted certificate.
By default, the program generates a non\-trusted certificate.
.It Fl V Ar nkeys
Generate parameters and keys for the Mu\-Varadharajan (MV) identification scheme.
.El
.Ss Random Seed File
All cryptographically sound key generation schemes must have means
to randomize the entropy seed used to initialize
the internal pseudo\-random number generator used
by the library routines.
The OpenSSL library uses a designated random seed file for this purpose.
The file must be available when starting the NTP daemon and
.Nm
program.
If a site supports OpenSSL or its companion OpenSSH,
it is very likely that means to do this are already available.
.Pp
It is important to understand that entropy must be evolved
for each generation, for otherwise the random number sequence
would be predictable.
Various means dependent on external events, such as keystroke intervals,
can be used to do this and some systems have built\-in entropy sources.
Suitable means are described in the OpenSSL software documentation,
but are outside the scope of this page.
.Pp
The entropy seed used by the OpenSSL library is contained in a file,
usually called
.Cm .rnd ,
which must be available when starting the NTP daemon
or the
.Nm
program.
The NTP daemon will first look for the file
using the path specified by the
.Ic randfile
subcommand of the
.Ic crypto
configuration command.
If not specified in this way, or when starting the
.Nm
program,
the OpenSSL library will look for the file using the path specified
by the
.Ev RANDFILE
environment variable in the user home directory,
whether root or some other user.
If the
.Ev RANDFILE
environment variable is not present,
the library will look for the
.Cm .rnd
file in the user home directory.
If the file is not available or cannot be written,
the daemon exits with a message to the system log and the program
exits with a suitable error message.
.Ss Cryptographic Data Files
All other file formats begin with two lines.
The first contains the file name, including the generated host name
and filestamp.
The second contains the datestamp in conventional Unix date format.
Lines beginning with # are considered comments and ignored by the
.Nm
program and
.Xr ntpd 8
daemon.
Cryptographic values are encoded first using ASN.1 rules,
then encrypted if necessary, and finally written PEM\-encoded
printable ASCII format preceded and followed by MIME content identifier lines.
.Pp
The format of the symmetric keys file is somewhat different
than the other files in the interest of backward compatibility.
Since DES\-CBC is deprecated in NTPv4, the only key format of interest
is MD5 alphanumeric strings.
Following hte heard the keys are
entered one per line in the format
.D1 Ar keyno type key
where
.Ar keyno
is a positive integer in the range 1\-65,535,
.Ar type
is the string MD5 defining the key format and
.Ar key
is the key itself,
which is a printable ASCII string 16 characters or less in length.
Each character is chosen from the 93 printable characters
in the range 0x21 through 0x7f excluding space and the
.Ql #
character.
.Pp
Note that the keys used by the
.Xr ntpq 8
and
.Xr ntpdc 8
programs
are checked against passwords requested by the programs
and entered by hand, so it is generally appropriate to specify these keys
in human readable ASCII format.
.Pp
The
.Nm
program generates a MD5 symmetric keys file
.Pa ntpkey_MD5key_ Ns Ar hostname.filestamp .
Since the file contains private shared keys,
it should be visible only to root and distributed by secure means
to other subnet hosts.
The NTP daemon loads the file
.Pa ntp.keys ,
so
.Nm
installs a soft link from this name to the generated file.
Subsequently, similar soft links must be installed by manual
or automated means on the other subnet hosts.
While this file is not used with the Autokey Version 2 protocol,
it is needed to authenticate some remote configuration commands
used by the
.Xr ntpq 8
and
.Xr ntpdc 8
utilities.
.Sh "OPTIONS"
.Bl -tag
.It  Fl b Ar imbits , Fl \-imbits Ns = Ns Ar imbits 
identity modulus bits.
This option takes an integer number as its argument.
The value of
.Ar imbits
is constrained to being:
.in +4
.nf
.na
in the range  256 through 2048
.fi
.in -4
.sp
The number of bits in the identity modulus.  The default is 256.
.It  Fl c Ar scheme , Fl \-certificate Ns = Ns Ar scheme 
certificate scheme.
.sp
scheme is one of
RSA\-MD2, RSA\-MD5, RSA\-SHA, RSA\-SHA1, RSA\-MDC2, RSA\-RIPEMD160,
DSA\-SHA, or DSA\-SHA1.
.sp
Select the certificate message digest/signature encryption scheme.
Note that RSA schemes must be used with a RSA sign key and DSA
schemes must be used with a DSA sign key.  The default without
this option is RSA\-MD5.
.It  Fl C Ar cipher , Fl \-cipher Ns = Ns Ar cipher 
privatekey cipher.
.sp
Select the cipher which is used to encrypt the files containing
private keys.  The default is three\-key triple DES in CBC mode,
equivalent to "@code{\-C des\-ede3\-cbc".  The openssl tool lists ciphers
available in "\fBopenssl \-h\fP" output.
.It  Fl d , Fl \-debug\-level 
Increase debug verbosity level.
This option may appear an unlimited number of times.
.sp
.It  Fl D Ar number , Fl \-set\-debug\-level Ns = Ns Ar number 
Set the debug verbosity level.
This option may appear an unlimited number of times.
This option takes an integer number as its argument.
.sp
.It  Fl e , Fl \-id\-key 
Write IFF or GQ identity keys.
.sp
Write the IFF or GQ client keys to the standard output.  This is
intended for automatic key distribution by mail.
.It  Fl G , Fl \-gq\-params 
Generate GQ parameters and keys.
.sp
Generate parameters and keys for the GQ identification scheme,
obsoleting any that may exist.
.It  Fl H , Fl \-host\-key 
generate RSA host key.
.sp
Generate new host keys, obsoleting any that may exist.
.It  Fl I , Fl \-iffkey 
generate IFF parameters.
.sp
Generate parameters for the IFF identification scheme, obsoleting
any that may exist.
.It  Fl i Ar group , Fl \-ident Ns = Ns Ar group 
set Autokey group name.
.sp
Set the optional Autokey group name to name.  This is used in
the file name of IFF, GQ, and MV client parameters files.  In
that role, the default is the host name if this option is not
provided.  The group name, if specified using \fB\-i/\-\-ident\fP or
using \fB\-s/\-\-subject\-name\fP following an '\fB@\fP' character,
is also a part of the self\-signed host certificate's subject and
issuer names in the form \fBhost@group\fP and should match the
\'\fBcrypto ident\fP' or '\fBserver ident\fP' configuration in
\fBntpd\fP's configuration file. 
.It  Fl l Ar lifetime , Fl \-lifetime Ns = Ns Ar lifetime 
set certificate lifetime.
This option takes an integer number as its argument.
.sp
Set the certificate expiration to lifetime days from now.
.It  Fl M , Fl \-md5key 
generate MD5 keys.
.sp
Generate MD5 keys, obsoleting any that may exist.
.It  Fl m Ar modulus , Fl \-modulus Ns = Ns Ar modulus 
modulus.
This option takes an integer number as its argument.
The value of
.Ar modulus
is constrained to being:
.in +4
.nf
.na
in the range  256 through 2048
.fi
.in -4
.sp
The number of bits in the prime modulus.  The default is 512.
.It  Fl P , Fl \-pvt\-cert 
generate PC private certificate.
.sp
Generate a private certificate.  By default, the program generates
public certificates.
.It  Fl p Ar passwd , Fl \-password Ns = Ns Ar passwd 
local private password.
.sp
Local files containing private data are encrypted with the
DES\-CBC algorithm and the specified password.  The same password
must be specified to the local ntpd via the "crypto pw password"
configuration command.  The default password is the local
hostname.
.It  Fl q Ar passwd , Fl \-export\-passwd Ns = Ns Ar passwd 
export IFF or GQ group keys with password.
.sp
Export IFF or GQ identity group keys to the standard output,
encrypted with the DES\-CBC algorithm and the specified password.
The same password must be specified to the remote ntpd via the
"crypto pw password" configuration command.  See also the option
-\-id\-key (\-e) for unencrypted exports.
.It  Fl S Ar sign , Fl \-sign\-key Ns = Ns Ar sign 
generate sign key (RSA or DSA).
.sp
Generate a new sign key of the designated type, obsoleting any
that may exist.  By default, the program uses the host key as the
sign key.
.It  Fl s Ar host@group , Fl \-subject\-name Ns = Ns Ar host@group 
set host and optionally group name.
.sp
Set the Autokey host name, and optionally, group name specified
following an '\fB@\fP' character.  The host name is used in the file
name of generated host and signing certificates, without the
group name.  The host name, and if provided, group name are used
in \fBhost@group\fP form for the host certificate's subject and issuer
fields.  Specifying '\fB\-s @group\fP' is allowed, and results in
leaving the host name unchanged while appending \fB@group\fP to the
subject and issuer fields, as with \fB\-i group\fP.  The group name, or
if not provided, the host name are also used in the file names
of IFF, GQ, and MV client parameter files.
.It  Fl T , Fl \-trusted\-cert 
trusted certificate (TC scheme).
.sp
Generate a trusted certificate.  By default, the program generates
a non\-trusted certificate.
.It  Fl V Ar num , Fl \-mv\-params Ns = Ns Ar num 
generate <num> MV parameters.
This option takes an integer number as its argument.
.sp
Generate parameters and keys for the Mu\-Varadharajan (MV)
identification scheme.
.It  Fl v Ar num , Fl \-mv\-keys Ns = Ns Ar num 
update <num> MV keys.
This option takes an integer number as its argument.
.sp
This option has not been fully documented.
.It Fl \&? , Fl \-help
Display usage information and exit.
.It Fl \&! , Fl \-more\-help
Pass the extended usage information through a pager.
.It Fl > Oo Ar cfgfile Oc , Fl \-save\-opts Oo Ns = Ns Ar cfgfile Oc
Save the option state to \fIcfgfile\fP.  The default is the \fIlast\fP
configuration file listed in the \fBOPTION PRESETS\fP section, below.
The command will exit after updating the config file.
.It Fl < Ar cfgfile , Fl \-load\-opts Ns = Ns Ar cfgfile , Fl \-no\-load\-opts
Load options from \fIcfgfile\fP.
The \fIno\-load\-opts\fP form will disable the loading
of earlier config/rc/ini files.  \fI\-\-no\-load\-opts\fP is handled early,
out of order.
.It Fl \-version Op Brq Ar v|c|n
Output version of program and exit.  The default mode is `v', a simple
version.  The `c' mode will print copyright information and `n' will
print the full copyright notice.
.El
.Sh "OPTION PRESETS"
Any option that is not marked as \fInot presettable\fP may be preset
by loading values from configuration ("RC" or ".INI") file(s) and values from
environment variables named:
.nf
  \fBNTP_KEYGEN_<option\-name>\fP or \fBNTP_KEYGEN\fP
.fi
.ad
The environmental presets take precedence (are processed later than)
the configuration files.
The \fIhomerc\fP files are "\fI$HOME\fP", and "\fI.\fP".
If any of these are directories, then the file \fI.ntprc\fP
is searched for within those directories.
.Sh USAGE
The
.Fl p Ar password
option specifies the write password and
.Fl q Ar password
option the read password for previously encrypted files.
The
.Nm
program prompts for the password if it reads an encrypted file
and the password is missing or incorrect.
If an encrypted file is read successfully and
no write password is specified, the read password is used
as the write password by default.
.Sh "ENVIRONMENT"
See \fBOPTION PRESETS\fP for configuration environment variables.
.Sh "FILES"
See \fBOPTION PRESETS\fP for configuration files.
.Sh "EXIT STATUS"
One of the following exit values will be returned:
.Bl -tag
.It 0 " (EXIT_SUCCESS)"
Successful program execution.
.It 1 " (EXIT_FAILURE)"
The operation failed or the command syntax was not valid.
.It 66 " (EX_NOINPUT)"
A specified configuration file could not be loaded.
.It 70 " (EX_SOFTWARE)"
libopts had an internal operational error.  Please report
it to autogen\-users@lists.sourceforge.net.  Thank you.
.El
.Sh "AUTHORS"
The University of Delaware and Network Time Foundation
.Sh "COPYRIGHT"
Copyright (C) 1992\-2016 The University of Delaware and Network Time Foundation all rights reserved.
This program is released under the terms of the NTP license, <http://ntp.org/license>.
.Sh BUGS
It can take quite a while to generate some cryptographic values,
from one to several minutes with modern architectures
such as UltraSPARC and up to tens of minutes to an hour
with older architectures such as SPARC IPC.
.Pp
Please report bugs to http://bugs.ntp.org .
.Pp
Please send bug reports to: http://bugs.ntp.org, bugs@ntp.org
.Sh NOTES
Portions of this document came from FreeBSD.
.Pp
This manual page was \fIAutoGen\fP\-erated from the \fBntp\-keygen\fP
option definitions.