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diff --git a/contrib/ntp/html/authentic.html b/contrib/ntp/html/authentic.html new file mode 100644 index 000000000000..62066c3b5444 --- /dev/null +++ b/contrib/ntp/html/authentic.html @@ -0,0 +1,224 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html> + <head> + <meta http-equiv="content-type" content="text/html;charset=iso-8859-1"> + <meta name="generator" content="HTML Tidy, see www.w3.org"> + <title>Authentication Support</title> + <!-- Changed by: Harlan Stenn, 24-Jul-2018 --> + <link href="scripts/style.css" type="text/css" rel="stylesheet"> + <style type="text/css"> + <!-- + <style1 { + color: #FF0000; + font-weight: bold; + } + .style1 {color: #FF0000} + --> + </style> + </head> + <body> + <h3>Authentication Support</h3> + <img src="pic/alice44.gif" alt="gif" align="left"><a href="http://www.eecis.udel.edu/%7emills/pictures.html">from <i>Alice's Adventures in Wonderland</i>, Lewis Carroll</a> + <p>Our resident cryptographer; now you see him, now you don't.</p> + <p>Last update: + <!-- #BeginDate format:En2m -->24-Jul-2018 09:12<!-- #EndDate --> + UTC</p> + <br clear="left"> + <h4>Related Links</h4> + <script type="text/javascript" language="javascript" src="scripts/hand.txt"></script> + <script type="text/javascript" language="javascript" src="scripts/authopt.txt"></script> + <h4>Table of Contents</h4> + <ul> + <li class="inline"><a href="#auth">Introduction</a></li> + <li class="inline"><a href="#symm">Symmetric Key Cryptography</a></li> + <li class="inline"><a href="#windows">Microsoft Windows Authentication</a></li> + <li class="inline"><a href="#pub">Public Key Cryptography</a></li> + </ul> + <hr> + <h4 id="auth">Introduction</h4> + <p>This page describes the various cryptographic authentication + provisions in NTPv4. Authentication support allows the NTP client to + verify that servers are in fact known and trusted and not intruders + intending accidentally or intentionally to masquerade as a legitimate + server. A detailed discussion of the NTP multi-layer security model + and vulnerability analysis is in the white + paper <a href="http://www.eecis.udel.edu/~mills/security.html">NTP + Security Analysis</a>.</p> + <p>The NTPv3 specification (RFC-1305) defined an authentication scheme + properly described as <em>symmetric key cryptography</em>. It used + the Data Encryption Standard (DES) algorithm operating in cipher-block + chaining (CBC) mode. Subsequently, this algorithm was replaced by the + RSA Message Digest 5 (MD5) algorithm commonly called keyed-MD5. + Either algorithm computes a message digest or one-way hash which can + be used to verify the client has the same message digest as the + server. The MD5 message digest algorithm is included in the + distribution, so without further cryptographic support, the + distribution can be freely exported.</p> + <p>If the OpenSSL cryptographic library is installed prior to building + the distribution, all message digest algorithms included in the + library may be used, including SHA and SHA1. However, if conformance + to FIPS 140-2 is required, only a limited subset of these algorithms + can be used. This library is available + from <a href="http://www.openssl.org">http://www.openssl.org</a> and + can be installed using the procedures outlined in + the <a href="build.html">Building and Installing the Distribution</a> + page. Once installed, the configure and build process automatically + detects the library and links the library routines required.</p> + <p>In addition to the symmetric key algorithms, this distribution + includes support for the Autokey public key algorithms and protocol + specified in RFC-5906 "Network Time Protocol Version 4: Autokey + Specification". This support is available only if the OpenSSL + library has been installed and the <tt>--enable-autokey</tt> option is + used when the distribution is built.</p> + <p> Public key cryptography is generally considered more secure than + symmetric key cryptography, since the security is based on private and + public values which are generated by each participant and where the + private value is never revealed. Autokey uses X.509 public + certificates, which can be produced by commercial services, the + OpenSSL application program, or + the <a href="keygen.html"><tt>ntp-keygen</tt></a> utility program in + the NTP software distribution.</p> + <p>Note that according to US law, NTP binaries including OpenSSL library + components, including the OpenSSL library itself, cannot be exported + outside the US without license from the US Department of Commerce. + Builders outside the US are advised to obtain the OpenSSL library + directly from OpenSSL, which is outside the US, and build outside the + US.</p> + <p>Authentication is configured separately for each association using + the <tt>key</tt> or <tt>autokey</tt> option of the <tt>server</tt> + configuration command, as described in + the <a href="confopt.html">Server Options</a> page. + The <a href="keygen.html">ntp-keygen</a> page describes the files + required for the various authentication schemes. Further details are + in the briefings, papers and reports at the NTP project page linked + from <a href="http://www.ntp.org">www.ntp.org</a>.</p> + <p>By default, the client sends non-authenticated packets and the server + responds with non-authenticated packets. If the client sends + authenticated packets, the server responds with authenticated packets + if correct, or a crypto-NAK packet if not. In the case of unsolicited + packets which might consume significant resources, such as broadcast + or symmetric mode packets, authentication is required, unless + overridden by a <tt>disable auth</tt> command. In the current climate + of targeted broadcast or "letterbomb" attacks, defeating + this requirement would be decidedly dangerous. In any case, + the <tt>notrust </tt>flag, described on + the <a href="authopt.html">Access Control Options</a> page, can be + used to disable access to all but correctly authenticated clients.</p> + <h4 id="symm">Symmetric Key Cryptography</h4> + <p>The original NTPv3 specification (RFC-1305), as well as the current + NTPv4 specification (RFC-5905), allows any one of possibly 65,535 + message digest keys (excluding zero), each distinguished by a 32-bit + key ID, to authenticate an association. The servers and clients + involved must agree on the key ID, key type and key to authenticate + NTP packets.</p> + <p>The message digest is a cryptographic hash computed by an algorithm + such as MD5, SHA, or AES-128 CMAC. When authentication is specified, + a message authentication code (MAC) is appended to the NTP packet + header. The MAC consists of a 32-bit key identifier (key ID) followed + by a 128- or 160-bit message digest. The algorithm computes the + digest as the hash of a 128- or 160- bit message digest key + concatenated with the NTP packet header fields with the exception of + the MAC. On transmit, the message digest is computed and inserted in + the MAC. On receive, the message digest is computed and compared with + the MAC. The packet is accepted only if the two MACs are identical. + If a discrepancy is found by the client, the client ignores the + packet, but raises an alarm. If this happens at the server, the + server returns a special message called a <em>crypto-NAK</em>. Since + the crypto-NAK is protected by the loopback test, an intruder cannot + disrupt the protocol by sending a bogus crypto-NAK.</p> + <p>Keys and related information are specified in a keys file, which must + be distributed and stored using secure means beyond the scope of the + NTP protocol itself. Besides the keys used for ordinary NTP + associations, additional keys can be used as passwords for + the <tt><a href="ntpq.html">ntpq</a></tt> + and <tt><a href="ntpdc.html">ntpdc</a></tt> utility programs. + Ordinarily, the <tt>ntp.keys</tt> file is generated by + the <tt><a href="keygen.html">ntp-keygen</a></tt> program, but it can + be constructed and edited using an ordinary text editor.</p> + <p> Each line of the keys file consists of three or four fields: a + key ID in the range 1 to 65,535, inclusive, a key type, a + message digest key consisting of a printable ASCII string up to + 20 characters or a hex digit string with more than 20 + characters, and an optional comma-separated list of IPs that are + allowed to serve time. If the OpenSSL library is installed, the + key type can be any message digest algorithm supported by the + library. If the OpenSSL library is not installed, the only + permitted key type is MD5.</p> + <table> + <caption style="caption-side: bottom;"> + Figure 1. Typical Symmetric Key File + </caption> + <tr><td style="border: 1px solid black; border-spacing: 0;"> + <pre style="color:grey;"> + # 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;fxlKgr/&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 + 21 MD5 sampo 10.1.2.3/24 + </pre></td></tr></table> + <p>Figure 1 shows a typical symmetric keys file used by the reference + implementation when the OpenSSL library is installed. Each line of + the file contains three or four fields. The first field is an integer + between 1 and 65535, inclusive, representing the key identifier. The + second field is the digest algorithm, which in the absence of the + OpenSSL library must be <tt>MD5</tt>, which designates the MD5 message + digest algorithm. The third field is the key. The optional fourth + field is one or more comma-separated IPs. An IP may end with an + optional <tt>/subnetbits</tt> suffix, which limits the acceptance of + the key identifier to packets claiming to be from the described IP + space. In this example, for the key IDs in the range 1-10 the key is + interpreted as a printable ASCII string. For the key IDs in the range + 11-20, the key is a 40-character hex digit string. In either case, + the key is truncated or zero-filled internally to either 128 or 160 + bits, depending on the key type. The line can be edited later or new + lines can be added to change any field. The key can be changed to a + password, such as <tt>2late4Me</tt> for key ID 10. Note that two or + more keys files can be combined in any order as long as the key IDs + are distinct.</p> + <p>When <tt>ntpd</tt> is started, it reads the keys file specified by + the <tt>keys</tt> command and installs the keys in the key cache. + However, individual keys must be activated with + the <tt>trustedkey</tt> configuration command before use. This + allows, for instance, the installation of possibly several batches of + keys and then activating a key remotely using <tt>ntpq</tt> + or <tt>ntpdc</tt>. The <tt>requestkey</tt> command selects the key ID + used as the password for the <tt>ntpdc</tt> utility, while + the <tt>controlkey</tt> command selects the key ID used as the + password for the <tt>ntpq</tt> utility.</p> + <h4 id="windows">Microsoft Windows Authentication</h4> + <p>In addition to the above means, <tt>ntpd</tt> now supports Microsoft + Windows MS-SNTP authentication using Active Directory services. This + support was contributed by the Samba Team and is still in development. + It is enabled using the <tt>mssntp</tt> flag of the <tt>restrict</tt> + command described on the <a href="accopt.html#restrict">Access Control + Options</a> page. <span class="style1">Note: Potential users should + be aware that these services involve a TCP connection to another + process that could potentially block, denying services to other users. + Therefore, this flag should be used only for a dedicated server with + no clients other than MS-SNTP.</span></p> + <h4 id="pub">Public Key Cryptography</h4> + <p>See the <a href="autokey.html">Autokey Public-Key Authentication</a> + page.</p> + <hr> + <script type="text/javascript" language="javascript" src="scripts/footer.txt"></script> + </body> +</html> |