/* -*- Mode: Text -*- */ autogen definitions options; #include copyright.def #include homerc.def #include autogen-version.def prog-name = "ntp-keygen"; prog-title = "create a Network Time Protocol host key"; package = ntp; include = '#include '; #include version.def flag = { value = b; name = imbits; arg-type = number; arg-name = imbits; arg-range = '256->2048'; ifdef = AUTOKEY; descrip = "identity modulus bits"; doc = <<- _EndOfDoc_ The number of bits in the identity modulus. The default is 512. _EndOfDoc_; }; flag = { value = c; name = certificate; arg-type = string; arg-name = scheme; ifdef = AUTOKEY; descrip = "certificate scheme"; doc = <<- _EndOfDoc_ 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. _EndOfDoc_; }; flag = { value = C; name = cipher; arg-type = string; arg-name = cipher; ifdef = AUTOKEY; descrip = "privatekey cipher"; doc = <<- _EndOfDoc_ 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 "@code{openssl -h}" output. _EndOfDoc_; }; #include debug-opt.def flag = { value = e; name = id-key; ifdef = AUTOKEY; descrip = "Write IFF or GQ identity keys"; doc = <<- _EndOfDoc_ Write the public parameters from the IFF or GQ client keys to the standard output. This is intended for automatic key distribution by email. _EndOfDoc_; }; flag = { value = G; name = gq-params; ifdef = AUTOKEY; descrip = "Generate GQ parameters and keys"; doc = <<- _EndOfDoc_ Generate parameters and keys for the GQ identification scheme, obsoleting any that may exist. _EndOfDoc_; }; flag = { value = H; name = host-key; ifdef = AUTOKEY; descrip = "generate RSA host key"; doc = <<- _EndOfDoc_ Generate new host keys, obsoleting any that may exist. _EndOfDoc_; }; flag = { value = I; name = iffkey; ifdef = AUTOKEY; descrip = "generate IFF parameters"; doc = <<- _EndOfDoc_ Generate parameters for the IFF identification scheme, obsoleting any that may exist. _EndOfDoc_; }; flag = { value = i; name = ident; ifdef = AUTOKEY; arg-type = string; arg-name = group; descrip = "set Autokey group name"; doc = <<- _EndOfDoc_ 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 @code{-i/--ident} or using @code{-s/--subject-name} following an '@code{@@}' character, is also a part of the self-signed host certificate subject and issuer names in the form @code{host@@group} and should match the '@code{crypto ident}' or '@code{server ident}' configuration in the @code{ntpd} configuration file. _EndOfDoc_; }; flag = { value = l; name = lifetime; ifdef = AUTOKEY; arg-type = number; arg-name = lifetime; descrip = "set certificate lifetime"; doc = <<- _EndOfDoc_ Set the certificate expiration to lifetime days from now. _EndOfDoc_; }; flag = { value = m; name = modulus; arg-type = number; arg-name = modulus; arg-range = '256->2048'; ifdef = AUTOKEY; descrip = "prime modulus"; doc = <<- _EndOfDoc_ The number of bits in the prime modulus. The default is 512. _EndOfDoc_; }; flag = { value = M; name = md5key; descrip = "generate symmetric keys"; doc = <<- _EndOfDoc_ Generate symmetric keys, obsoleting any that may exist. _EndOfDoc_; }; flag = { value = P; name = pvt-cert; ifdef = AUTOKEY; descrip = "generate PC private certificate"; doc = <<- _EndOfDoc_ Generate a private certificate. By default, the program generates public certificates. _EndOfDoc_; }; flag = { value = p; name = password; // was: pvt-passwd; ifdef = AUTOKEY; arg-type = string; arg-name = passwd; descrip = "local private password"; doc = <<- _EndOfDoc_ 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. _EndOfDoc_; }; flag = { value = q; name = export-passwd; // Was: get-pvt-passwd; ifdef = AUTOKEY; arg-type = string; arg-name = passwd; descrip = "export IFF or GQ group keys with password"; doc = <<- _EndOfDoc_ 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. _EndOfDoc_; }; flag = { value = s; name = subject-name; arg-type = string; arg-name = host@group; ifdef = AUTOKEY; descrip = "set host and optionally group name"; doc = <<- _EndOfDoc_ Set the Autokey host name, and optionally, group name specified following an '@code{@@}' 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 @code{host@@group} form for the host certificate subject and issuer fields. Specifying '@code{-s @@group}' is allowed, and results in leaving the host name unchanged while appending @code{@@group} to the subject and issuer fields, as with @code{-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. _EndOfDoc_; }; flag = { value = S; name = sign-key; arg-type = string; arg-name = sign; ifdef = AUTOKEY; descrip = "generate sign key (RSA or DSA)"; doc = <<- _EndOfDoc_ 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. _EndOfDoc_; }; flag = { value = T; name = trusted-cert; ifdef = AUTOKEY; descrip = "trusted certificate (TC scheme)"; doc = <<- _EndOfDoc_ Generate a trusted certificate. By default, the program generates a non-trusted certificate. _EndOfDoc_; }; flag = { value = V; name = mv-params; arg-type = number; arg-name = num; ifdef = AUTOKEY; descrip = "generate MV parameters"; doc = <<- _EndOfDoc_ Generate parameters and keys for the Mu-Varadharajan (MV) identification scheme. _EndOfDoc_; }; flag = { value = v; name = mv-keys; arg-type = number; arg-name = num; ifdef = AUTOKEY; descrip = "update MV keys"; }; /* explain: Additional information whenever the usage routine is invoked */ explain = <<- _END_EXPLAIN _END_EXPLAIN; doc-section = { ds-type = 'DESCRIPTION'; ds-format = 'mdoc'; ds-text = <<- _END_PROG_MDOC_DESCRIP 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. .Pp 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. .Pp 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 .Xr ntpq 1ntpqmdoc and .Xr ntpdc 1ntpdcmdoc 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 read password for local encrypted files and the .Fl q option the write password for encrypted files sent to remote sites. If no password is specified, the host name returned by the Unix .Xr hostname 1 command, normally the DNS name of the host, is used as the the default read password, for convenience. 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. .Pp The .Cm pw option of the .Ic crypto .Xr 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 .Xr 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. .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 .Pa 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. In these cases, NFS clients can specify the files in another directory such as .Pa /etc using the .Ic keysdir .Xr ntpd 1ntpdmdoc configuration file command. .Pp This program directs commentary and error messages to the standard error stream .Pa stderr and remote files to the standard output stream .Pa 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 .Pa ntpkey\&* and include the file type, generating host and filestamp, as described in the .Sx "Cryptographic Data Files" section below. .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 .Ar keys directory, usually .Pa /usr/local/etc , then run the program. .Pp To test and gain experience with Autokey concepts, log in as root and change to the .Ar keys directory, usually .Pa /usr/local/etc . When run for the first time, or if all files with names beginning with .Pa ntpkey\&* have been removed, use the .Nm command without arguments to generate a default .Cm RSA host key and matching .Cm 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. .Pp The host key is used to encrypt the cookie when required and so must be .Cm 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 .Cm RSA or .Cm DSA type. By default, the message digest type is .Cm MD5 , but any combination of sign key type and message digest type supported by the OpenSSL library can be specified, including those using the .Cm AES128CMAC , MD2 , MD5 , MDC2 , SHA , SHA1 and .Cm 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 .Cm RSA sign keys; however, only .Cm SHA and .Cm SHA1 certificates are compatible with .Cm 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 .Xr su 1 command to assume root may not work properly, since by default the OpenSSL library looks for the random seed file .Pa .rnd in the user home directory. However, there should be only one .Pa .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 .Pa .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 .Xr 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. .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 .Ar hostname and .Ar filestamp file name extensions, the files for an NTP 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, .Xr ntpd 1ntpdmdoc follows it to the file name to extract the .Ar filestamp . If a link is not present, .Xr ntpd 1ntpdmdoc extracts the .Ar 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 .Ar filestamp extension for all files generated at one time, so each generation is distinct and can be readily recognized in monitoring data. .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 .Cm RSA or .Cm DSA type. By default, the signature message digest type is .Cm 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. .Pp 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 File names begin with the prefix .Pa ntpkey Ns _ and end with the suffix .Pa _ Ns Ar hostname . Ar filestamp , where .Ar hostname is the owner name, usually the string returned by the Unix .Xr hostname 1 command, 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 Pa ntpkey\&* command or all files generated at a specific time can be removed by a .Ic rm Pa \&* Ns 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. .Ss 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 .Cm RSA encryption, .Cm MD5 message digest and .Cm 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 .Pa 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 frequent need to do this is when a .Cm DSA Ns -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. If .Nm is run again without these options, it generates a new certificate using the same scheme and sign key, and soft link. .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, and soft links. However, if the host or sign key is changed, .Xr ntpd 1ntpdmdoc should be restarted. When .Xr 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. .Ss Identity Schemes As mentioned on the Autonomous Authentication page, the default .Cm TC identity scheme is vulnerable to a middleman attack. However, there are more secure identity schemes available, including .Cm PC , IFF , GQ and .Cm 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. .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 Ns _ Cm RSA Pa key_alice. Ar filestamp and trusted private certificate file .Pa ntpkey Ns _ Cm RSA-MD5 _ Pa cert_alice. Ar 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 .Ar 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, and recreating the soft links. .Pp For the .Cm IFF scheme proceed as in the .Cm TC scheme to generate keys and certificates for all group hosts, then for every trusted host in the group, generate the .Cm 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_alice. Ns Ar 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_alice to this file. If there are no hosts restricted to operate only as clients, there is nothing further to do. As the .Cm 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 email program. Copy or email this file to all restricted clients. On these clients install a soft link from the generic .Pa ntpkey_iff_alice to this file. To further protect the integrity of the keys, each file can be encrypted with a secret password. .Pp For the .Cm GQ scheme proceed as in the .Cm TC scheme to generate keys and certificates for all group hosts, then for every trusted host in the group, generate the .Cm 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_alice. Ns Ar 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_alice to this file. In addition, on each host .Ar bob install a soft link from generic .Pa ntpkey_gq_ Ns Ar bob to this file. As the .Cm GQ scheme updates the .Cm GQ parameters file and certificate at the same time, keys and certificates can be regenerated as needed. .Pp For the .Cm MV scheme, proceed as in the .Cm 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_trish. Ns Ar filestamp and client key files .Pa ntpkeys_MVkey Ns Ar d _ Pa trish. Ar 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_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 .Pa ntpkey_mvkey_bob to the client key file. As the .Cm 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 b Fl -imbits Ns = Ar modulus Set the number of bits in the identity modulus for generating identity keys to .Ar modulus bits. The number of bits in the identity modulus defaults to 256, but can be set to values from 256 to 2048 (32 to 256 octets). Use the larger moduli with caution, as this can consume considerable computing resources and increases the size of authenticated packets. .It Fl c Fl -certificate Ns = Ar scheme Select certificate signature encryption/message digest scheme. The .Ar scheme can be one of the following: .Cm RSA-MD2 , RSA-MD5 , RSA-MDC2 , RSA-SHA , RSA-SHA1 , RSA-RIPEMD160 , DSA-SHA , or .Cm DSA-SHA1 . Note that .Cm RSA schemes must be used with an .Cm RSA sign key and .Cm DSA schemes must be used with a .Cm DSA sign key. The default without this option is .Cm RSA-MD5 . If compatibility with FIPS 140-2 is required, either the .Cm DSA-SHA or .Cm DSA-SHA1 scheme must be used. .It Fl C Fl -cipher Ns = Ar cipher Select the OpenSSL cipher to encrypt the files containing private keys. The default without this option is three-key triple DES in CBC mode, .Cm des-ede3-cbc . The .Ic openssl Fl h command provided with OpenSSL displays available ciphers. .It Fl d Fl -debug-level Increase debugging verbosity level. This option displays the cryptographic data produced in eye-friendly billboards. .It Fl D Fl -set-debug-level Ns = Ar level Set the debugging verbosity to .Ar level . This option displays the cryptographic data produced in eye-friendly billboards. .It Fl e Fl -id-key Write the .Cm IFF or .Cm GQ public parameters from the .Ar IFFkey or GQkey client keys file previously specified as unencrypted data to the standard output stream .Pa stdout . This is intended for automatic key distribution by email. .It Fl G Fl -gq-params Generate a new encrypted .Cm GQ parameters and key file for the Guillou-Quisquater (GQ) identity scheme. This option is mutually exclusive with the .Fl I and .Fl V options. .It Fl H Fl -host-key Generate a new encrypted .Cm RSA public/private host key file. .It Fl I Fl -iffkey Generate a new encrypted .Cm IFF key file for the Schnorr (IFF) identity scheme. This option is mutually exclusive with the .Fl G and Fl V options. .It Fl i Fl -ident Ns = Ar group Set the optional Autokey group name to .Ar group . This is used in the identity scheme parameter file names of .Cm IFF , GQ , and .Cm MV client parameters files. In that role, the default is the host name if no group is provided. The group name, if specified using .Fl i or .Fl s following an .Ql @@ character, is also used in certificate subject and issuer names in the form .Ar host @@ group and should match the group specified via .Ic crypto Cm ident or .Ic server Cm ident in the ntpd configuration file. .It Fl l Fl -lifetime Ns = Ar days Set the lifetime for certificate expiration to .Ar days . The default lifetime is one year (365 days). .It Fl m Fl -modulus Ns = Ar bits Set the number of bits in the prime modulus for generating files to .Ar bits . The modulus defaults to 512, but can be set from 256 to 2048 (32 to 256 octets). Use the larger moduli with caution, as this can consume considerable computing resources and increases the size of authenticated packets. .It Fl M Fl -md5key Generate a new symmetric keys file containing 10 .Cm MD5 keys, and if OpenSSL is available, 10 .Cm SHA keys. An .Cm MD5 key is a string of 20 random printable ASCII characters, while a .Cm 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. .It Fl p Fl -password Ns = Ar passwd Set the password for reading and writing encrypted files to .Ar passwd . These include the host, sign and identify key files. By default, the password is the string returned by the Unix .Ic hostname command. .It Fl P Fl -pvt-cert Generate a new private certificate used by the .Cm PC identity scheme. By default, the program generates public certificates. Note: the PC identity scheme is not recommended for new installations. .It Fl q Fl -export-passwd Ns = Ar passwd Set the password for writing encrypted .Cm IFF , GQ and MV identity files redirected to .Pa stdout to .Ar passwd . In effect, these files are decrypted with the .Fl p password, then encrypted with the .Fl q password. By default, the password is the string returned by the Unix .Ic hostname command. .It Fl s Fl -subject-key Ns = Ar Oo host Oc Op @@ Ar group Specify the Autokey host name, where .Ar host is the optional host name and .Ar group is the optional group name. The host name, and if provided, group name are used in .Ar host @@ group form as certificate subject and issuer. Specifying .Fl s @@ Ar group is allowed, and results in leaving the host name unchanged, as with .Fl i Ar group . The group name, or if no group is provided, the host name are also used in the file names of .Cm IFF , GQ , and .Cm MV identity scheme client parameter files. If .Ar host is not specified, the default host name is the string returned by the Unix .Ic hostname command. .It Fl S Fl -sign-key Ns = Op Cm RSA | DSA Generate a new encrypted public/private sign key file of the specified type. By default, the sign key is the host key and has the same type. If compatibility with FIPS 140-2 is required, the sign key type must be .Cm DSA . .It Fl T Fl -trusted-cert Generate a trusted certificate. By default, the program generates a non-trusted certificate. .It Fl V Fl -mv-params Ar nkeys Generate .Ar nkeys encrypted server keys and parameters for the Mu-Varadharajan (MV) identity scheme. This option is mutually exclusive with the .Fl I and .Fl G options. Note: support for this option should be considered a work in progress. .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 .Pa .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 .Cm 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 .Pa .rnd file in the user home directory. Since both the .Nm program and .Xr ntpd 1ntpdmdoc daemon must run as root, the logical place to put this file is in .Pa /.rnd or .Pa /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. .Ss Cryptographic Data Files 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 .Pa ntpkey_ Ns Ar key _ Ar name . Ar filestamp , where .Ar key is the key or parameter type, .Ar name is the host or group name and .Ar filestamp is the filestamp (NTP seconds) when the file was created. By convention, .Ar key names in generated file names include both upper and lower case characters, while .Ar 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 .Pa date format. Lines beginning with .Ql # are considered comments and ignored by the .Nm program and .Xr ntpd 1ntpdmdoc daemon. .Pp 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. .Pp The format of the symmetric keys file, ordinarily named .Pa 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. .Bd -literal -unfilled -offset center # ntpkey_MD5key_bk.ntp.org.3595864945 # Thu Dec 12 19:22:25 2013 1 MD5 L";Nw<\`.Il0%XXK9O'51VwV