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