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1.10 deraadt 4: <title>Cryptography in OpenBSD</title>
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1.22 deraadt 14: <img alt="[OpenBSD]" height=200 width=200 SRC="images/blowfish.jpg">
1.37 deraadt 15: <p>
16: <h2><font color=#e00000>Cryptography</font><hr></h2>
1.32 deraadt 17:
18: <strong>Index</strong><br>
1.41 louis 19: <a href=#why>Why do we ship cryptography?</a>.<br>
1.40 deraadt 20: <a href=#ssh>SSH soon built in</a>.<br>
1.32 deraadt 21: <a href=#prng>Pseudo Random Number Generators</a> (PRNG): ARC4, ...<br>
22: <a href=#hash>Cryptographic Hash Functions</a>: MD5, SHA1, ...<br>
23: <a href=#trans>Cryptographic Transforms</a>: DES, Blowfish, ...<br>
24:
25: <a href=#people>International Cryptographers wanted</a><br>
1.33 deraadt 26: <a href=#papers>Further Reading</a><br>
1.1 deraadt 27: <p>
1.32 deraadt 28: <hr>
29:
30: <a name=why></a>
1.42 ! deraadt 31: <h3><font color=#e00000>Why do we ship cryptography?</font></h3><p>
1.32 deraadt 32:
33: In three words: <strong>because we can</strong>.<p>
34:
1.1 deraadt 35: The OpenBSD project is based in Canada.<p>
36:
1.23 deraadt 37: The <a href=ECL.html>Export Control List of Canada</a>
38: places no significant restriction on the export of
1.5 deraadt 39: cryptographic software, and is even more explicit about the free
40: export of freely-available cryptographic software. Marc Plumb has
41: done
1.2 deraadt 42: <a href=http://insight.mcmaster.ca/org/efc/pages/doc/crypto-export.html>
1.31 aaron 43: some research to test the cryptographic laws</a>.
1.2 deraadt 44: <p>
1.1 deraadt 45:
1.3 deraadt 46: Hence the OpenBSD project has embedded cryptography into numerous places
47: in the operating system. We require that the cryptographic software we
48: use be <a href=policy.html>freely available and with good licenses</a>.
1.32 deraadt 49: We do not directly use cryptography with nasty patents.
1.13 deraadt 50: We also require that such software is from countries with useful export
1.16 deraadt 51: licenses because we do not wish to break the laws of any country.
52: The cryptographic software components which we use currently were
53: written in Argentina, Australia, Canada, Germany, Greece, Norway, and
54: Sweden.
55: <p>
1.7 deraadt 56:
1.15 deraadt 57: When we create OpenBSD releases or snapshots we build our release
58: binaries in free countries to assure that the sources and binaries we
59: provide to users are free of tainting. In the past our release binary
60: builds have been done in Canada, Sweden, and Germany.<p>
61:
1.16 deraadt 62: OpenBSD ships with Kerberos IV included. The codebase we use is the
1.17 deraadt 63: exportable KTH-based release from Sweden. Our X11 source has been
64: extended to make use of Kerberos IV as well. Kerberos V support will
1.16 deraadt 65: perhaps appear in 1999, but at present time a freely exportable
66: Kerberos V release does not exist.<p>
67:
1.15 deraadt 68: Today cryptography is an important means for enhancing the <a
69: href=security.html>security</a> of an operating system. The
1.42 ! deraadt 70: cryptography utilized in OpenBSD can be classified into various
! 71: aspects, described as follows.<p>
1.10 deraadt 72:
1.39 louis 73: <a name=ssh></a>
1.42 ! deraadt 74: <h3><font color=#e00000>SSH soon built in</font></h3><p>
1.39 louis 75:
1.40 deraadt 76: What is the first thing most people do after installing OpenBSD?
77: They install Secure Shell (ssh) from the ports tree or the packages on
78: the FTP sites. Until now, that is.<p>
1.39 louis 79:
80: This is still very much a work in progress, but we found an innovative way
1.40 deraadt 81: around the RSA patent. We are taking a free license release of ssh and
82: OpenBSD-ifying it. We will get around the USA-based RSA patent by providing
83: an easy way to automatically download and install a RSA-enabled package
1.41 louis 84: containing shared library versions of libcrypto and libssl. These packages
1.40 deraadt 85: are based on OpenSSL. People living outside the USA can freely use the
86: RSA patented code, while people inside the USA can freely use it for
87: non-commercial purposes. It appears as if companies inside the USA can
88: use the RSA libraries too, as long as RSA is not used in a profit generating
89: role.<p>
1.39 louis 90:
1.40 deraadt 91: But this way almost everyone will get ssh built-in.<p>
1.39 louis 92:
1.18 deraadt 93: <a name=prng></a>
1.42 ! deraadt 94: <h3><font color=#e00000>Pseudo Random Number Generators</font></h3><p>
1.32 deraadt 95:
1.10 deraadt 96: A Pseudo Random Number Generator (PRNG) provides applications with a stream of
97: numbers which have certain important properties for system security:<p>
98:
99: <ul>
1.11 deraadt 100: <li>It should be impossible for an outsider to predict the output of the
101: random number generator even with knowledge of previous output.
102: <li>The generated numbers should not have repeating patterns which means
103: the PRNG should have a very long cycle length.
1.10 deraadt 104: </ul>
1.32 deraadt 105: <p>
1.10 deraadt 106:
1.13 deraadt 107: A PRNG is normally just an algorithm where the same initial starting
108: values will yield the same sequence of outputs. On a multiuser
109: operating system there are many sources which allow seeding the PRNG
110: with random data. The OpenBSD kernel uses the mouse interrupt timing,
111: network data interrupt latency, inter-keypress timing and disk IO
112: information to fill an entropy pool. Random numbers are available for
113: kernel routines and are exported via devices to userland programs.
1.36 deraadt 114: So far random numbers are used in the following places:<p>
1.13 deraadt 115:
1.10 deraadt 116: <ul>
1.14 deraadt 117: <li>Dynamic sin_port allocation in bind(2).
118: <li>PIDs of processes.
1.26 aaron 119: <li>IP datagram IDs.
1.14 deraadt 120: <li>RPC transaction IDs (XID).
121: <li>NFS RPC transaction IDs (XID).
122: <li>DNS Query-IDs.
123: <li>Inode generation numbers, see getfh(2) and fsirand(8).
1.31 aaron 124: <li>Timing perturbance in traceroute(8).
1.14 deraadt 125: <li>Stronger temporary names for mktemp(3) and mkstemp(3)
126: <li>Randomness added to the TCP ISS value for protection against
127: spoofing attacks.
1.29 deraadt 128: <li>random padding in IPSEC esp_old packets.
1.14 deraadt 129: <li>To generate salts for the various password algorithms.
130: <li>For generating fake S/Key challenges.
1.28 angelos 131: <li>In <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>photurisd</a>
132: and <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=isakmpd>isakmpd</a>
133: to provide liveness proof of key exchanges.
1.10 deraadt 134: </ul>
1.1 deraadt 135:
1.10 deraadt 136: <p>
1.18 deraadt 137: <a name=hash></a>
1.42 ! deraadt 138: <h3><font color=#e00000>Cryptographic Hash Functions</font></h3><p>
1.32 deraadt 139:
1.10 deraadt 140: A Hash Function compresses its input data to a string of
1.36 deraadt 141: constant size. For a Cryptographic Hash Function it is infeasible to find:
142:
1.1 deraadt 143: <ul>
1.11 deraadt 144: <li>two inputs which have the same output (collision resistant),
145: <li>a different input for a given input with the same output
146: (2nd preimage resistant).
1.1 deraadt 147: </ul>
1.32 deraadt 148: <p>
1.10 deraadt 149:
1.12 millert 150: In OpenBSD MD5, SHA1, and RIPEMD-160 are used as Cryptographic Hash Functions,
1.36 deraadt 151: e.g:<p>
1.10 deraadt 152: <ul>
1.27 deraadt 153: <li>In <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=skey>S/Key</a>
154: to provide one time passwords.
155: <li>In <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=ipsec>IPsec</a>,
156: <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>photurisd</a>
157: and
158: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=isakmpd>isakmpd(8)</a>
159: to authenticate the data origin of packets and to ensure packet integrity.
160: <li>For FreeBSD-style MD5 passwords (not enabled by default), see
161: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=passwd.conf&sektion=5>
162: passwd.conf(5)</a>
163: <li>For TCP SYN cookie support (not enabled by default), see
164: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=options&sektion=4>
165: options(4)</a>
1.24 niklas 166: <li>In libssl for digital signing of messages.
1.10 deraadt 167: </ul>
1.32 deraadt 168: <p>
1.10 deraadt 169:
1.6 deraadt 170: <p>
1.18 deraadt 171: <a name=trans></a>
1.42 ! deraadt 172: <h3><font color=#e00000>Cryptographic Transforms</font></h3><p>
1.32 deraadt 173:
1.11 deraadt 174: Cryptographic Transforms are used to encrypt and decrypt data. These
175: are normally used with an encryption key for data encryption and with
176: a decryption key for data decryption. The security of a Cryptographic
177: Transform should rely only on the keying material.<p>
1.6 deraadt 178:
1.24 niklas 179: OpenBSD provides transforms like DES, 3DES, Blowfish and Cast for the
1.36 deraadt 180: kernel and userland programs, which are used in many places like:<p>
1.10 deraadt 181: <ul>
1.27 deraadt 182: <li>In libc for creating
183: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=blf_key>Blowfish</a>
1.33 deraadt 184: passwords. See also the <a href=papers/bcrypt-paper.ps>USENIX paper</a>
185: on this topic.
1.27 deraadt 186: <li>In
187: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=ipsec>IPsec</a>
188: to provide confidentiality for the network layer.
189: <li>In Kerberos and a handful of kerberized applications, like
190: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=telnet>telnet</a>,
191: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=cvs>cvs</a>,
192: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=rsh>rsh</a>,
193: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=rcp>rcp</a>,
194: and
195: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=rlogin>rlogin</a>.
1.24 niklas 196: <li>In <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>
1.27 deraadt 197: photurisd</a> and
198: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=isakmpd>isakmpd</a>
199: to protect the exchanges where IPsec key material is negotiated.
1.24 niklas 200: <li>In AFS to protect the messages passing over the network, providing
1.27 deraadt 201: confidentiality of remote filesystem access.
1.24 niklas 202: <li>In libssl to let applications communicate over the de-facto standard
203: cryptographically secure SSL protocol.
1.10 deraadt 204: </ul>
1.1 deraadt 205:
1.10 deraadt 206: <p>
1.32 deraadt 207: <a name=people></a>
1.42 ! deraadt 208: <h3><font color=#e00000>International Cryptographers Wanted</font></h3><p>
1.32 deraadt 209:
210: Of course, our project needs people to work on these systems. If any
211: non-American cryptographer who meets the constraints listed earlier is
212: interested in helping out with embedded cryptography in OpenBSD,
213: please contact us.<p>
214:
1.33 deraadt 215: <p>
216: <a name=papers></a>
1.42 ! deraadt 217: <h3><font color=#e00000>Further Reading</font></h3><p>
1.33 deraadt 218:
219: A number of papers have been written by OpenBSD team members, about
220: cryptographic changes they have done in OpenBSD. The postscript
1.34 deraadt 221: versions of these documents are available as follows.<p>
1.33 deraadt 222:
223: <ul>
224: <li>A Future-Adaptable Password Scheme
225: Niels Provos, David Mazieres.<br>
226: <a href=papers/bcrypt-paper.ps>paper</a> and
227: <a href=papers/bcrypt-slides.ps>slides</a>.
228: <li>Cryptography in OpenBSD: An Overview<br>
229: Theo de Raadt, Niklas Hallqvist, Artur Grabowski,
230: Angelos D. Keromytis, Niels Provos.<br>
231: <a href=papers/crypt-paper.ps>paper</a> and
232: <a href=papers/crypt-slides.ps>slides</a>.
233: </ul>
234:
1.32 deraadt 235: <p>
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