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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>
19: <a href=#why>Why do we ship cryptography?</a>.<br>
20: <a href=#prng>Pseudo Random Number Generators</a> (PRNG): ARC4, ...<br>
21: <a href=#hash>Cryptographic Hash Functions</a>: MD5, SHA1, ...<br>
22: <a href=#trans>Cryptographic Transforms</a>: DES, Blowfish, ...<br>
23:
24: <a href=#people>International Cryptographers wanted</a><br>
1.33 deraadt 25: <a href=#papers>Further Reading</a><br>
1.1 deraadt 26: <p>
1.32 deraadt 27: <hr>
28:
29: <dl>
30: <a name=why></a>
1.37 deraadt 31: <li><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
70: cryptography utilized in OpenBSD can be classified into three
1.33 deraadt 71: different aspects, which will be described later.<p>
1.10 deraadt 72:
73: <p>
1.18 deraadt 74: <a name=prng></a>
1.37 deraadt 75: <li><h3><font color=#e00000>Pseudo Random Number Generators</font></h3><p>
1.32 deraadt 76:
1.10 deraadt 77: A Pseudo Random Number Generator (PRNG) provides applications with a stream of
78: numbers which have certain important properties for system security:<p>
79:
80: <ul>
1.11 deraadt 81: <li>It should be impossible for an outsider to predict the output of the
82: random number generator even with knowledge of previous output.
83: <li>The generated numbers should not have repeating patterns which means
84: the PRNG should have a very long cycle length.
1.10 deraadt 85: </ul>
1.32 deraadt 86: <p>
1.10 deraadt 87:
1.13 deraadt 88: A PRNG is normally just an algorithm where the same initial starting
89: values will yield the same sequence of outputs. On a multiuser
90: operating system there are many sources which allow seeding the PRNG
91: with random data. The OpenBSD kernel uses the mouse interrupt timing,
92: network data interrupt latency, inter-keypress timing and disk IO
93: information to fill an entropy pool. Random numbers are available for
94: kernel routines and are exported via devices to userland programs.
1.36 deraadt 95: So far random numbers are used in the following places:<p>
1.13 deraadt 96:
1.10 deraadt 97: <ul>
1.14 deraadt 98: <li>Dynamic sin_port allocation in bind(2).
99: <li>PIDs of processes.
1.26 aaron 100: <li>IP datagram IDs.
1.14 deraadt 101: <li>RPC transaction IDs (XID).
102: <li>NFS RPC transaction IDs (XID).
103: <li>DNS Query-IDs.
104: <li>Inode generation numbers, see getfh(2) and fsirand(8).
1.31 aaron 105: <li>Timing perturbance in traceroute(8).
1.14 deraadt 106: <li>Stronger temporary names for mktemp(3) and mkstemp(3)
107: <li>Randomness added to the TCP ISS value for protection against
108: spoofing attacks.
1.29 deraadt 109: <li>random padding in IPSEC esp_old packets.
1.14 deraadt 110: <li>To generate salts for the various password algorithms.
111: <li>For generating fake S/Key challenges.
1.28 angelos 112: <li>In <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>photurisd</a>
113: and <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=isakmpd>isakmpd</a>
114: to provide liveness proof of key exchanges.
1.10 deraadt 115: </ul>
1.1 deraadt 116:
1.10 deraadt 117: <p>
1.18 deraadt 118: <a name=hash></a>
1.37 deraadt 119: <li><h3><font color=#e00000>Cryptographic Hash Functions</font></h3><p>
1.32 deraadt 120:
1.10 deraadt 121: A Hash Function compresses its input data to a string of
1.36 deraadt 122: constant size. For a Cryptographic Hash Function it is infeasible to find:
123:
1.1 deraadt 124: <ul>
1.11 deraadt 125: <li>two inputs which have the same output (collision resistant),
126: <li>a different input for a given input with the same output
127: (2nd preimage resistant).
1.1 deraadt 128: </ul>
1.32 deraadt 129: <p>
1.10 deraadt 130:
1.12 millert 131: In OpenBSD MD5, SHA1, and RIPEMD-160 are used as Cryptographic Hash Functions,
1.36 deraadt 132: e.g:<p>
1.10 deraadt 133: <ul>
1.27 deraadt 134: <li>In <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=skey>S/Key</a>
135: to provide one time passwords.
136: <li>In <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=ipsec>IPsec</a>,
137: <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>photurisd</a>
138: and
139: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=isakmpd>isakmpd(8)</a>
140: to authenticate the data origin of packets and to ensure packet integrity.
141: <li>For FreeBSD-style MD5 passwords (not enabled by default), see
142: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=passwd.conf&sektion=5>
143: passwd.conf(5)</a>
144: <li>For TCP SYN cookie support (not enabled by default), see
145: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=options&sektion=4>
146: options(4)</a>
1.24 niklas 147: <li>In libssl for digital signing of messages.
1.10 deraadt 148: </ul>
1.32 deraadt 149: <p>
1.10 deraadt 150:
1.6 deraadt 151: <p>
1.18 deraadt 152: <a name=trans></a>
1.37 deraadt 153: <li><h3><font color=#e00000>Cryptographic Transforms</font></h3><p>
1.32 deraadt 154:
1.11 deraadt 155: Cryptographic Transforms are used to encrypt and decrypt data. These
156: are normally used with an encryption key for data encryption and with
157: a decryption key for data decryption. The security of a Cryptographic
158: Transform should rely only on the keying material.<p>
1.6 deraadt 159:
1.24 niklas 160: OpenBSD provides transforms like DES, 3DES, Blowfish and Cast for the
1.36 deraadt 161: kernel and userland programs, which are used in many places like:<p>
1.10 deraadt 162: <ul>
1.27 deraadt 163: <li>In libc for creating
164: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=blf_key>Blowfish</a>
1.33 deraadt 165: passwords. See also the <a href=papers/bcrypt-paper.ps>USENIX paper</a>
166: on this topic.
1.27 deraadt 167: <li>In
168: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=ipsec>IPsec</a>
169: to provide confidentiality for the network layer.
170: <li>In Kerberos and a handful of kerberized applications, like
171: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=telnet>telnet</a>,
172: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=cvs>cvs</a>,
173: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=rsh>rsh</a>,
174: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=rcp>rcp</a>,
175: and
176: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=rlogin>rlogin</a>.
1.24 niklas 177: <li>In <a href=http://wserver.physnet.uni-hamburg.de/provos/photuris/>
1.27 deraadt 178: photurisd</a> and
179: <a href=http://www.openbsd.org/cgi-bin/man.cgi?query=isakmpd>isakmpd</a>
180: to protect the exchanges where IPsec key material is negotiated.
1.24 niklas 181: <li>In AFS to protect the messages passing over the network, providing
1.27 deraadt 182: confidentiality of remote filesystem access.
1.24 niklas 183: <li>In libssl to let applications communicate over the de-facto standard
184: cryptographically secure SSL protocol.
1.10 deraadt 185: </ul>
1.1 deraadt 186:
1.10 deraadt 187: <p>
1.32 deraadt 188: <a name=people></a>
1.37 deraadt 189: <li><h3><font color=#e00000>International Cryptographers Wanted</font></h3><p>
1.32 deraadt 190:
191: Of course, our project needs people to work on these systems. If any
192: non-American cryptographer who meets the constraints listed earlier is
193: interested in helping out with embedded cryptography in OpenBSD,
194: please contact us.<p>
195:
1.33 deraadt 196: <p>
197: <a name=papers></a>
1.37 deraadt 198: <li><h3><font color=#e00000>Further Reading</font></h3><p>
1.33 deraadt 199:
200: A number of papers have been written by OpenBSD team members, about
201: cryptographic changes they have done in OpenBSD. The postscript
1.34 deraadt 202: versions of these documents are available as follows.<p>
1.33 deraadt 203:
204: <ul>
205: <li>A Future-Adaptable Password Scheme
206: Niels Provos, David Mazieres.<br>
207: <a href=papers/bcrypt-paper.ps>paper</a> and
208: <a href=papers/bcrypt-slides.ps>slides</a>.
209: <li>Cryptography in OpenBSD: An Overview<br>
210: Theo de Raadt, Niklas Hallqvist, Artur Grabowski,
211: Angelos D. Keromytis, Niels Provos.<br>
212: <a href=papers/crypt-paper.ps>paper</a> and
213: <a href=papers/crypt-slides.ps>slides</a>.
214: </ul>
215:
1.32 deraadt 216: </dl>
217:
218: <p>
1.1 deraadt 219: <hr>
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