This document describes the use of the NTP Project's ntp-keygen
program, that generates cryptographic data files used by the NTPv4
authentication and identity schemes.
It can generate message digest keys used in symmetric key cryptography and,
if the OpenSSL software
library has been installed, it can generate host keys, sign keys,
certificates, and identity keys and parameters used by the Autokey
public key cryptography.
The message digest keys file is generated in a
format compatible with NTPv3.
All other files are in PEM-encoded
printable ASCII format so they can be embedded as MIME attachments in
mail to other sites.
This document applies to version 4.2.8p11 of ntp-keygen.
This program generates cryptographic data files used by the NTPv4 authentication and identity schemes. It can generate message digest keys used in symmetric key cryptography and, if the OpenSSL software library has been installed, it can generate host keys, sign keys, certificates, and identity keys and parameters used by the Autokey public key cryptography. The message digest keys file is generated in a format compatible with NTPv3. All other files are in PEM-encoded printable ASCII format so they can be embedded as MIME attachments in mail to other sites.
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 ntpq and ntpdc utility programs.
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.
Some files used by this program are encrypted using a private password.
The -p option specifies the password for local encrypted files and the
-q option the password for encrypted files sent to remote sites.
If no password is specified, the host name returned by the Unix
gethostname() function, normally the DNS name of the host, is used.
The pw option of the 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 ntpd without password, but only on the same
host.
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 ntp.keys, is
usually installed in /etc.
Other files and links are usually installed
in /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 keysdir
configuration command in such cases.
Normally, this is in /etc.
This program directs commentary and error messages to the standard
error stream stderr and remote files to the standard output stream
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 ntpkey and include the file type,
generating host and filestamp,
as described in the Cryptographic Data Files section below.
To test and gain experience with Autokey concepts, log in as root and
change to the keys directory, usually /usr/local/etc.
When run for the
first time, or if all files with names beginning ntpkey] have been
removed, use the ntp-keygen 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.
Run the command on as many hosts as necessary.
Designate one of them as the trusted host (TH) using ntp-keygen
with the -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.
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 -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 -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.
Additional information on trusted groups and identity schemes is on the Autokey Public-Key Authentication page.
This program generates cryptographic data files used by the NTPv4 authentication and identification schemes. It can generate message digest keys used in symmetric key cryptography and, if the OpenSSL software library has been installed, it can generate host keys, signing keys, certificates, and identity keys and parameters used in Autokey public key cryptography. These files are used for cookie encryption, digital signature, and challenge/response identification algorithms compatible with the Internet standard security infrastructure.
The message digest symmetric keys file is generated in a format compatible with NTPv3. All other files are in PEM-encoded printable ASCII format, so they can be embedded as MIME attachments in email to other sites and certificate authorities. By default, files are not encrypted.
When used to generate message digest symmetric 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 SHA1, AES-128-CMAC, and
other message digest algorithms.
The message digest symmetric 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
ntpq(1ntpqmdoc)
and
ntpdc(1ntpdcmdoc)
utility programs.
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.
Some files used by this program are encrypted using a private password.
The
-p
option specifies the read password for local encrypted files and the
-q
option the write password for encrypted files sent to remote sites.
If no password is specified, the host name returned by the Unix
hostname(1)
command, normally the DNS name of the host, is used as the the default read
password, for convenience.
The
ntp-keygen
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.
The
pw
option of the
crypto
ntpd(1ntpdmdoc)
configuration command specifies the read
password for previously encrypted local files.
This must match the local read password used by this program.
If not specified, the host name is used.
Thus, if files are generated by this program without an explicit password,
they can be read back by
ntpd(1ntpdmdoc)
without specifying an explicit password but only on the same host.
If the write password used for encryption is specified as the host name,
these files can be read by that host with no explicit password.
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
ntp.keys,
is usually installed in
/etc.
Other files and links are usually installed in
/usr/local/etc,
which is normally in a shared filesystem in
NFS-mounted networks and cannot be changed by shared clients.
In these cases, NFS clients can specify the files in another
directory such as
/etc
using the
keysdir
ntpd(1ntpdmdoc)
configuration file command.
This program directs commentary and error messages to the standard error stream stderr and remote files to the standard output stream 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 ntpkey* and include the file type, generating host and filestamp, as described in the Cryptographic Data Files section below.
The safest way to run the
ntp-keygen
program is logged in directly as root.
The recommended procedure is change to the
keys
directory, usually
/usr/local/etc,
then run the program.
To test and gain experience with Autokey concepts, log in as root and
change to the
keys
directory, usually
/usr/local/etc.
When run for the first time, or if all files with names beginning with
ntpkey*
have been removed, use the
ntp-keygen
command without arguments to generate a default
RSA
host key and matching
RSA-MD5
certificate file with expiration date one year hence,
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 without options, the program uses the
existing keys and parameters and generates a new certificate file with
new expiration date one year hence, and soft link.
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
AES128CMAC, MD2, MD5, MDC2, SHA, SHA1
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.
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.
Running the program as other than root and using the Unix
su(1)
command
to assume root may not work properly, since by default the OpenSSL library
looks for the random seed file
.rnd
in the user home directory.
However, there should be only one
.rnd,
most conveniently
in the root directory, so it is convenient to define the
.Ev RANDFILE
environment variable used by the OpenSSL library as the path to
.rnd.
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
/etc
using the
keysdir
ntpd(1ntpdmdoc)
configuration file 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.
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.
All files are installed by default in the keys directory /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.
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 filestamp file name extensions, the files for an NTP server and dependent clients can all be installed in the same shared directory.
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(1ntpdmdoc)
follows it to the file name to extract the
filestamp.
If a link is not present,
ntpd(1ntpdmdoc)
extracts the
filestamp
from the file itself.
This allows clients to verify that the file and generation times
are always current.
The
ntp-keygen
program uses the same
filestamp
extension for all files generated
at one time, so each generation is distinct and can be readily
recognized in monitoring data.
Run the command on as many hosts as necessary.
Designate one of them as the trusted host (TH) using
ntp-keygen
with the
-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.
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
-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
-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.
Additional information on trusted groups and identity schemes is on the Autokey Public-Key Authentication page.
File names begin with the prefix
ntpkey_
and end with the suffix
_hostname. filestamp,
where
hostname
is the owner name, usually the string returned
by the Unix
hostname(1)
command, and
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
rm ntpkey*
command or all files generated
at a specific time can be removed by a
rm *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.
Each cryptographic configuration involves selection of a signature scheme
and identification scheme, called a cryptotype,
as explained in the
Authentication Options
section of
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
Automatic NTP Configuration Options
section of
ntp.conf(5).
On each trusted host as root, change to the keys directory.
To insure a fresh fileset, remove all
ntpkey
files.
Then run
ntp-keygen
-T
to generate keys and a trusted certificate.
On all other hosts do the same, but leave off the
-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.
If it is necessary to use a different sign key or different digest/signature
scheme than the default, run
ntp-keygen
with the
-S type
option, where
type
is either
RSA
or
DSA.
The most frequent 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
ntp-keygen
with the
-c scheme
option and selected
scheme
as needed.
If
ntp-keygen
is run again without these options, it generates a new certificate
using the same scheme and sign key, and soft link.
After setting up the environment it is advisable to update certificates
from time to time, if only to extend the validity interval.
Simply run
ntp-keygen
with the same flags as before to generate new certificates
using existing keys, and soft links.
However, if the host or sign key is changed,
ntpd(1ntpdmdoc)
should be restarted.
When
ntpd(1ntpdmdoc)
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.
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
schemes described below.
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.
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.
The PC scheme supports only one trusted host in the group.
On trusted host alice run
ntp-keygen
-P
-p password
to generate the host key file
ntpkey_ RSA key_alice. filestamp
and trusted private certificate file
ntpkey_ RSA-MD5 _ cert_alice. filestamp,
and soft links.
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
ntpkey_host_bob
to the host key file and soft link
ntpkey_cert_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, and recreating the soft links.
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
ntp-keygen
-T
-I
-p password
to produce her parameter file
ntpkey_IFFpar_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
ntpkey_iff_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.
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
ntp-keygen
-e
and pipe the output to a file or email program.
Copy or email this file to all restricted clients.
On these clients install a soft link from the generic
ntpkey_iff_alice
to this file.
To further protect the integrity of the keys,
each file can be encrypted with a secret password.
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
ntp-keygen
-T
-G
-p password
to produce her parameter file
ntpkey_GQpar_alice.filestamp,
which includes both server and client keys.
Copy this file to all group hosts and install a soft link
from the generic
ntpkey_gq_alice
to this file.
In addition, on each host
bob
install a soft link
from generic
ntpkey_gq_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.
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
ntp-keygen
-V n
-p password,
where
n
is the number of revokable keys (typically 5) to produce
the parameter file
ntpkeys_MVpar_trish.filestamp
and client key files
ntpkeys_MVkeyd _ trish. filestamp
where
d
is the key number (0 <
d
<
n).
Copy the parameter file to alice and install a soft link
from the generic
ntpkey_mv_alice
to this file.
Copy one of the client key files to alice for later distribution
to her clients.
It does not 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 clients.
On client bob install a soft link from generic
ntpkey_mvkey_bob
to the client key file.
As the
MV
scheme is independent of keys and certificates,
these files can be refreshed as needed.
-b --imbits= modulus-c --certificate= schemeRSA-MD2, RSA-MD5, RSA-MDC2, RSA-SHA, RSA-SHA1, RSA-RIPEMD160, DSA-SHA,
or
DSA-SHA1.
Note that
RSA
schemes must be used with an
RSA
sign key and
DSA
schemes must be used with a
DSA
sign key.
The default without this option is
RSA-MD5.
If compatibility with FIPS 140-2 is required, either the
DSA-SHA
or
DSA-SHA1
scheme must be used.
-C --cipher= cipherdes-ede3-cbc.
The
openssl -h
command provided with OpenSSL displays available ciphers.
-d --debug-level-D --set-debug-level= level-e --id-keyIFF
or
GQ
public parameters from the
IFFkey or GQkey
client keys file previously specified
as unencrypted data to the standard output stream
stdout.
This is intended for automatic key distribution by email.
-G --gq-paramsGQ
parameters and key file for the Guillou-Quisquater (GQ) identity scheme.
This option is mutually exclusive with the
-I
and
-V
options.
-H --host-keyRSA
public/private host key file.
-I --iffkeyIFF
key file for the Schnorr (IFF) identity scheme.
This option is mutually exclusive with the
-G
and
Fl V
options.
-i --ident= groupIFF, GQ,
and
MV
client parameters files.
In that role, the default is the host name if no group is provided.
The group name, if specified using
-i
or
-s
following an
@
character, is also used in certificate subject and issuer names in the form
host @ group
and should match the group specified via
crypto ident
or
server ident
in the ntpd configuration file.
-l --lifetime= days-m --modulus= bits-M --md5keyMD5
keys, and if OpenSSL is available, 10
SHA
keys.
An
MD5
key is a string of 20 random printable ASCII characters, while a
SHA
key is a string of 40 random hex digits.
The file can be edited using a text editor to change the key type or key content.
This option is mutually exclusive with all other options.
-p --password= passwdhostname
command.
-P --pvt-certPC
identity scheme.
By default, the program generates public certificates.
Note: the PC identity scheme is not recommended for new installations.
-q --export-passwd= passwdIFF, GQ and MV
identity files redirected to
stdout
to
passwd.
In effect, these files are decrypted with the
-p
password, then encrypted with the
-q
password.
By default, the password is the string returned by the Unix
hostname
command.
-s --subject-key= [host] [@ group]-s -@ group
is allowed, and results in leaving the host name unchanged, as with
-i group.
The group name, or if no group is provided, the host name are also used in the
file names of
IFF, GQ,
and
MV
identity scheme client parameter files.
If
host
is not specified, the default host name is the string returned by the Unix
hostname
command.
-S --sign-key= [RSA | DSA]DSA.
-T --trusted-cert-V --mv-params nkeys-I
and
-G
options.
Note: support for this option should be considered a work in progress.
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
ntp-keygen
program.
If a site supports OpenSSL or its companion OpenSSH,
it is very likely that means to do this are already available.
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.
The entropy seed used by the OpenSSL library is contained in a file,
usually called
.rnd,
which must be available when starting the NTP daemon
or the
ntp-keygen
program.
The NTP daemon will first look for the file
using the path specified by the
randfile
subcommand of the
crypto
configuration command.
If not specified in this way, or when starting the
ntp-keygen
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
.rnd
file in the user home directory.
Since both the
ntp-keygen
program and
ntpd(1ntpdmdoc)
daemon must run as root, the logical place to put this file is in
/.rnd
or
/root/.rnd.
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.
All file formats begin with two nonencrypted lines.
The first line contains the file name, including the generated host name
and filestamp, in the format
ntpkey_key _ name. filestamp,
where
key
is the key or parameter type,
name
is the host or group name and
filestamp
is the filestamp (NTP seconds) when the file was created.
By convention,
key
names in generated file names include both upper and lower case
characters, while
key
names in generated link names include only lower case characters.
The filestamp is not used in generated link names.
The second line contains the datestamp in conventional Unix
date
format.
Lines beginning with
#
are considered comments and ignored by the
ntp-keygen
program and
ntpd(1ntpdmdoc)
daemon.
The remainder of the file contains cryptographic data, encoded first using ASN.1 rules, then encrypted if necessary, and finally written in PEM-encoded printable ASCII text, preceded and followed by MIME content identifier lines.
The format of the symmetric keys file, ordinarily named ntp.keys, is somewhat different than the other files in the interest of backward compatibility. Ordinarily, the file is generated by this program, but it can be constructed and edited using an ordinary text editor.
# ntpkey_MD5key_bk.ntp.org.3595864945 # Thu Dec 12 19:22:25 2013 1 MD5 L";Nw<\`.I<f4U0)247"i # MD5 key 2 MD5 &>l0%XXK9O'51VwV<xq~ # MD5 key 3 MD5 lb4zLW~d^!K:]RsD'qb6 # MD5 key 4 MD5 Yue:tL[+vR)M\`n~bY,'? # MD5 key 5 MD5 B;fx'Kgr/&4ZTbL6=RxA # MD5 key 6 MD5 4eYwa\`o@}3i@@@@V@@..R9!l # MD5 key 7 MD5 \`A.([h+;wTQ|xfi%Sn_! # MD5 key 8 MD5 45:V,r4]l6y^JH6"Sh?F # MD5 key 9 MD5 3-5vcn*6l29DS?Xdsg)* # MD5 key 10 MD5 2late4Me # MD5 key 11 SHA1 a27872d3030a9025b8446c751b4551a7629af65c # SHA1 key 12 SHA1 21bc3b4865dbb9e920902abdccb3e04ff97a5e74 # SHA1 key 13 SHA1 2b7736fe24fef5ba85ae11594132ab5d6f6daba9 # SHA1 key 14 SHA a5332809c8878dd3a5b918819108a111509aeceb # SHA key 15 MD2 2fe16c88c760ff2f16d4267e36c1aa6c926e6964 # MD2 key 16 MD4 b2691811dc19cfc0e2f9bcacd74213f29812183d # MD4 key 17 MD5 e4d6735b8bdad58ec5ffcb087300a17f7fef1f7c # MD5 key 18 MDC2 a8d5e2315c025bf3a79174c87fbd10477de2eabc # MDC2 key 19 RIPEMD160 77ca332cafb30e3cafb174dcd5b80ded7ba9b3d2 # RIPEMD160 key 20 AES128CMAC f92ff73eee86c1e7dc638d6489a04e4e555af878 # AES128CMAC key
Figure 1. Typical Symmetric Key File
Figure 1 shows a typical symmetric keys file used by the reference implementation. Following the header the keys are entered one per line in the format
keyno type key
where
keyno
is a positive integer in the range 1-65534;
type
is the key type for the message digest algorithm, which in the absence of the
OpenSSL library must be
MD5
to designate the MD5 message digest algorithm;
if the OpenSSL library is installed, the key type can be any
message digest algorithm supported by that library;
however, if compatibility with FIPS 140-2 is required,
the key type must be either
SHA
or
SHA1;
key
is the key itself,
which is a printable ASCII string 20 characters or less in length:
each character is chosen from the 93 printable characters
in the range 0x21 through 0x7e (
!
through
~
) excluding space and the
#
character, and terminated by whitespace or a
#
character.
An OpenSSL key consists of a hex-encoded ASCII string of 40 characters, which
is truncated as necessary.
Note that the keys used by the
ntpq(1ntpqmdoc)
and
ntpdc(1ntpdcmdoc)
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.
The
ntp-keygen
program generates a symmetric keys file
ntpkey_MD5key_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
ntp.keys,
so
ntp-keygen
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
ntpq(1ntpqmdoc)
and
ntpdc(1ntpdcmdoc)
utilities.
This section was generated by AutoGen,
using the agtexi-cmd template and the option descriptions for the ntp-keygen program.
This software is released under the NTP license, <http://ntp.org/license>.
This is the automatically generated usage text for ntp-keygen.
The text printed is the same whether selected with the help option
(--help) or the more-help option (--more-help). more-help will print
the usage text by passing it through a pager program.
more-help is disabled on platforms without a working
fork(2) function. The PAGER environment variable is
used to select the program, defaulting to more. Both will exit
with a status code of 0.
ntp-keygen (ntp) - Create a NTP host key - Ver. 4.2.8p10
Usage: ntp-keygen [ -<flag> [<val>] | --<name>[{=| }<val>] ]...
Flg Arg Option-Name Description
-b Num imbits identity modulus bits
- it must be in the range:
256 to 2048
-c Str certificate certificate scheme
-C Str cipher privatekey cipher
-d no debug-level Increase debug verbosity level
- may appear multiple times
-D Num set-debug-level Set the debug verbosity level
- may appear multiple times
-e no id-key Write IFF or GQ identity keys
-G no gq-params Generate GQ parameters and keys
-H no host-key generate RSA host key
-I no iffkey generate IFF parameters
-i Str ident set Autokey group name
-l Num lifetime set certificate lifetime
-m Num modulus prime modulus
- it must be in the range:
256 to 2048
-M no md5key generate symmetric keys
-P no pvt-cert generate PC private certificate
-p Str password local private password
-q Str export-passwd export IFF or GQ group keys with password
-s Str subject-name set host and optionally group name
-S Str sign-key generate sign key (RSA or DSA)
-T no trusted-cert trusted certificate (TC scheme)
-V Num mv-params generate <num> MV parameters
-v Num mv-keys update <num> MV keys
opt version output version information and exit
-? no help display extended usage information and exit
-! no more-help extended usage information passed thru pager
-> opt save-opts save the option state to a config file
-< Str load-opts load options from a config file
- disabled as '--no-load-opts'
- may appear multiple times
Options are specified by doubled hyphens and their name or by a single
hyphen and the flag character.
The following option preset mechanisms are supported:
- reading file $HOME/.ntprc
- reading file ./.ntprc
- examining environment variables named NTP_KEYGEN_*
Please send bug reports to: <http://bugs.ntp.org, bugs@ntp.org>
This is the “identity modulus bits” option. This option takes a number argument imbits.
This option has some usage constraints. It:
AUTOKEY during the compilation.
The number of bits in the identity modulus. The default is 256.
This is the “certificate scheme” option. This option takes a string argument scheme.
This option has some usage constraints. It:
AUTOKEY during the compilation.
scheme is one of RSA-MD2, RSA-MD5, RSA-MDC2, RSA-SHA, RSA-SHA1, RSA-RIPEMD160, DSA-SHA, or DSA-SHA1.
Select the certificate signature encryption/message digest 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.
This is the “privatekey cipher” option. This option takes a string argument cipher.
This option has some usage constraints. It:
AUTOKEY during the compilation.
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 "-C des-ede3-cbc". The openssl tool lists ciphers
available in "openssl -h" output.
This is the “write iff or gq identity keys” option.
This option has some usage constraints. It:
AUTOKEY during the compilation.
Write the public parameters from the IFF or GQ client keys to the standard output. This is intended for automatic key distribution by email.
This is the “generate gq parameters and keys” option.
This option has some usage constraints. It:
AUTOKEY during the compilation.
Generate parameters and keys for the GQ identification scheme, obsoleting any that may exist.
This is the “generate rsa host key” option.
This option has some usage constraints. It:
AUTOKEY during the compilation.
Generate new host keys, obsoleting any that may exist.
This is the “generate iff parameters” option.
This option has some usage constraints. It:
AUTOKEY during the compilation.
Generate parameters for the IFF identification scheme, obsoleting any that may exist.
This is the “set autokey group name” option. This option takes a string argument group.
This option has some usage constraints. It:
AUTOKEY during the compilation.
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 -i/--ident or
using -s/--subject-name following an '@' character,
is also a part of the self-signed host certificate subject and
issuer names in the form host@group and should match the
'crypto ident' or 'server ident' configuration in the
ntpd configuration file.
This is the “set certificate lifetime” option. This option takes a number argument lifetime.
This option has some usage constraints. It:
AUTOKEY during the compilation.
Set the certificate expiration to lifetime days from now.
This is the “prime modulus” option. This option takes a number argument modulus.
This option has some usage constraints. It:
AUTOKEY during the compilation.
The number of bits in the prime modulus. The default is 512.
This is the “generate symmetric keys” option. Generate symmetric keys, obsoleting any that may exist.
This is the “generate pc private certificate” option.
This option has some usage constraints. It:
AUTOKEY during the compilation.
Generate a private certificate. By default, the program generates public certificates.
This is the “local private password” option. This option takes a string argument passwd.
This option has some usage constraints. It:
AUTOKEY during the compilation.
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.
This is the “export iff or gq group keys with password” option. This option takes a string argument passwd.
This option has some usage constraints. It:
AUTOKEY during the compilation.
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.
This is the “set host and optionally group name” option. This option takes a string argument host@group.
This option has some usage constraints. It:
AUTOKEY during the compilation.
Set the Autokey host name, and optionally, group name specified
following an '@' 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 host@group form for the host certificate subject and issuer
fields. Specifying '-s @group' is allowed, and results in
leaving the host name unchanged while appending @group to the
subject and issuer fields, as with -i group. 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.
This is the “generate sign key (rsa or dsa)” option. This option takes a string argument sign.
This option has some usage constraints. It:
AUTOKEY during the compilation.
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.
This is the “trusted certificate (tc scheme)” option.
This option has some usage constraints. It:
AUTOKEY during the compilation.
Generate a trusted certificate. By default, the program generates a non-trusted certificate.
This is the “generate <num> mv parameters” option. This option takes a number argument num.
This option has some usage constraints. It:
AUTOKEY during the compilation.
Generate parameters and keys for the Mu-Varadharajan (MV) identification scheme.
This is the “update <num> mv keys” option. This option takes a number argument num.
This option has some usage constraints. It:
AUTOKEY during the compilation.
This option has no doc documentation.
Any option that is not marked as not presettable may be preset by
loading values from configuration ("rc" or "ini") files, and values from environment variables named NTP-KEYGEN and NTP-KEYGEN_<OPTION_NAME>. <OPTION_NAME> must be one of
the options listed above in upper case and segmented with underscores.
The NTP-KEYGEN variable will be tokenized and parsed like
the command line. The remaining variables are tested for existence and their
values are treated like option arguments.
libopts will search in 2 places for configuration files:
HOME, and PWD
are expanded and replaced when ntp-keygen runs.
For any of these that are plain files, they are simply processed.
For any that are directories, then a file named .ntprc is searched for
within that directory and processed.
Configuration files may be in a wide variety of formats. The basic format is an option name followed by a value (argument) on the same line. Values may be separated from the option name with a colon, equal sign or simply white space. Values may be continued across multiple lines by escaping the newline with a backslash.
Multiple programs may also share the same initialization file. Common options are collected at the top, followed by program specific segments. The segments are separated by lines like:
[NTP-KEYGEN]
or by
<?program ntp-keygen>
Do not mix these styles within one configuration file.
Compound values and carefully constructed string values may also be specified using XML syntax:
<option-name>
<sub-opt>...<...>...</sub-opt>
</option-name>
yielding an option-name.sub-opt string value of
"...<...>..."
AutoOpts does not track suboptions. You simply note that it is a
hierarchicly valued option. AutoOpts does provide a means for searching
the associated name/value pair list (see: optionFindValue).
The command line options relating to configuration and/or usage help are:
Print the program version to standard out, optionally with licensing information, then exit 0. The optional argument specifies how much licensing detail to provide. The default is to print just the version. The licensing infomation may be selected with an option argument. Only the first letter of the argument is examined:
One of the following exit values will be returned:
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 OpenSSL library routines.
If a site supports ssh, it is very likely that means to do this are
already available.
The entropy seed used by the OpenSSL library is contained in a file,
usually called .rnd, which must be available when
starting the ntp-keygen program or ntpd daemon.
The OpenSSL library looks for the file using the path specified by the
RANDFILE environment variable in the user home directory, whether root
or some other user.
If the RANDFILE environment variable is not
present, the library looks for the .rnd file in the user home
directory.
Since both the ntp-keygen program and ntpd daemon must run
as root, the logical place to put this file is in /.rnd or
/root/.rnd.
If the file is not available or cannot be written, the program exits
with a message to the system log.
File and link names are in the form ntpkey_key_name.fstamp,
where key is the key or parameter type,
name is the host or group name and
fstamp is the filestamp (NTP seconds) when the file was created).
By convention, key names in generated file names include both upper and
lower case characters, while key names in generated link names include
only lower case characters. The filestamp is not used in generated link
names.
The key name is a string defining the cryptographic key type. Key types include public/private keys host and sign, certificate cert and several challenge/response key types. By convention, client files used for challenges have a par subtype, as in the IFF challenge IFFpar, while server files for responses have a key subtype, as in the GQ response GQkey.
All files begin with two nonencrypted lines. The first line contains
the file name in the format ntpkey_key_host.fstamp.
The second line contains the datestamp in conventional Unix date format.
Lines beginning with # are ignored.
The remainder of the file contains cryptographic data encoded first using ASN.1 rules, then encrypted using the DES-CBC algorithm with given password and finally written in PEM-encoded printable ASCII text preceded and followed by MIME content identifier lines.
The format of the symmetric keys file, ordinarily named ntp.keys,
is somewhat different than the other files in the interest of backward
compatibility.
Ordinarily, the file is generated by this program, but
it can be constructed and edited using an ordinary text editor.
# ntpkey_MD5key_hms.local.3564038757
# Sun Dec 9 02:45:57 2012
1 MD5 "]!ghT%O;3)WJ,/Nc:>I # MD5 key
2 MD5 lu+H^tF46BKR-6~pV_5 # MD5 key
3 MD5 :lnoVsE%Yz*avh%EtNC # MD5 key
4 MD5 |fdZrf0sF~^V # MD5 key
5 MD5 IyAG>O"y"LmCRS!*bHC # MD5 key
6 MD5 ">e\A # MD5 key
7 MD5 c9x=M'CfLxax9v)PV-si # MD5 key
8 MD5 E|=jvFVov?Bn|Ev=&aK\ # MD5 key
9 MD5 T!c4UT&`(m$+m+B6,`Q0 # MD5 key
10 MD5 JVF/1=)=IFbHbJQz..Cd # MD5 key
11 SHA1 6dea311109529e436c2b4fccae9bc753c16d1b48 # SHA1 key
12 SHA1 7076f373d86c4848c59ff8046e49cb7d614ec394 # SHA1 key
13 SHA1 5f48b1b60591eb01b7cf1d33b7774f08d20262d3 # SHA1 key
14 SHA1 eed5ab9d9497319ec60cf3781d52607e76720178 # SHA1 key
15 SHA1 f283562611a04c964da8126296f5f8e58c3f85de # SHA1 key
16 SHA1 1930da171297dd63549af50b29449de17dcf341f # SHA1 key
17 SHA1 fee892110358cd4382322b889869e750db8e8a8f # SHA1 key
18 SHA1 b5520c9fadd7ad3fd8bfa061c8821b65d029bb37 # SHA1 key
19 SHA1 8c74fb440ec80f453ec6aaa62b9baed0ab723b92 # SHA1 key
20 SHA1 6bc05f734306a189326000970c19b3910f403795 # SHA1 key
Figure 1. Typical Symmetric Key File
Figure 1 shows a typical symmetric keys file used by the reference implementation. Each line of the file contains three fields, first an integer between 1 and 65534, inclusive, representing the key identifier used in the server and peer configuration commands. Next is the key type for the message digest algorithm, which in the absence of the OpenSSL library must be MD5 to designate the MD5 message digest algorithm. If the OpenSSL library is installed, the key type can be any message digest algorithm supported by that library. However, if compatibility with FIPS 140-2 is required, the key type must be either SHA or SHA1. The key type can be changed using an ASCII text editor.
An MD5 key consists of a printable ASCII string less than or equal to 16 characters and terminated by whitespace or a # character. An OpenSSL key consists of a hex-encoded ASCII string of 40 characters, which is truncated as necessary.
Note that the keys used by the ntpq and ntpdc 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.
The ntp-keygen program generates a MD5 symmetric keys file
ntpkey_MD5key_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 ntp.keys, so ntp-keygen
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 ntpq and
ntpdc utilities.