Date: Thu, 12 Jul 2001 18:59:40 +0400 (MSD) From: Alex Kapranoff <kapr@acm.org> To: FreeBSD-gnats-submit@freebsd.org Cc: honig@sprynet.com Subject: docs/28916: DocBook conversion of doc/articles/ipsec-must Message-ID: <200107121459.f6CExeq01850@kapran.bitmcnit.bryansk.su>
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>Number: 28916
>Category: docs
>Synopsis: DocBook conversion of doc/articles/ipsec-must
>Confidential: no
>Severity: non-critical
>Priority: high
>Responsible: freebsd-doc
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Thu Jul 12 08:10:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: Alex Kapranoff
>Release: FreeBSD 5.0-CURRENT i386
>Organization:
Inner Mongolia
>Environment:
System: FreeBSD kapran.bitmcnit.bryansk.su 5.0-CURRENT FreeBSD 5.0-CURRENT #5: Sun Jun 24 22:56:52 MSD 2001 root@kapran.bitmcnit.bryansk.su:/usr/src/sys/compile/KAPRAN i386
>Description:
I added some content (mostly removing obsolete info and
providing additional links) along with converting the text to
DocBook. A review would be appreciated.
>How-To-Repeat:
>Fix:
# This is a shell archive. Save it in a file, remove anything before
# this line, and then unpack it by entering "sh file". Note, it may
# create directories; files and directories will be owned by you and
# have default permissions.
#
# This archive contains:
#
# Makefile
# article.sgml
#
echo x - Makefile
sed 's/^X//' >Makefile << 'END-of-Makefile'
X# $FreeBSD: doc/en_US.ISO8859-1/articles/ipsec-must/Makefile,v 1.1 2000/06/26 09:10:24 nik Exp $
X
XDOC?= article
X
XFORMATS?= html
X
XINSTALL_COMPRESSED?=gz
XINSTALL_ONLY_COMPRESSED?=
X
XSRCS= article.sgml
X
XDOC_PREFIX?= ${.CURDIR}/../../..
X
X.include "${DOC_PREFIX}/share/mk/doc.project.mk"
END-of-Makefile
echo x - article.sgml
sed 's/^X//' >article.sgml << 'END-of-article.sgml'
X<!DOCTYPE article PUBLIC "-//FreeBSD//DTD DocBook V4.1-Based Extension//EN" [
X<!ENTITY % man PUBLIC "-//FreeBSD//ENTITIES DocBook Manual Page Entities//EN">
X%man;
X]>
X
X<!-- $FreeBSD$ -->
X
X<article>
X <articleinfo>
X <title>Independent Verification of IPSec Functionality in FreeBSD</title>
X
X <author>
X <firstname>David</firstname>
X <surname>Honig</surname>
X
X <affiliation>
X <address><email>honig@sprynet.com</email></address>
X </affiliation>
X </author>
X
X <pubdate>3 May 1999</pubdate>
X
X <abstract>
X <para>You installed IPsec and it seems to be working. How do you
X know? I describe a method for experimentally verifying that IPsec is
X working.</para>
X </abstract>
X </articleinfo>
X
X <sect1>
X <title>The Problem</title>
X
X <para>First, let's assume you have <link linkend="ipsec-install">
X installed <emphasis>IPsec</emphasis></link>. How do you know
X it's <link linkend="caveat">working</link>? Sure, your
X connection won't work if its misconfigured, and it will work
X when you finally get it right. &man.netstat.1; will list it.
X But can you independently confirm it?</para>
X </sect1>
X
X <sect1>
X <title>The Solution</title>
X
X <para>First, some crypto-relevant info theory:</para>
X
X <orderedlist>
X <listitem>
X <para>encrypted data is uniformly distributed, i.e., has maximal
X entropy per symbol;</para>
X </listitem>
X
X <listitem>
X <para>raw, uncompressed data is typically redundant, i.e., has
X sub-maximal entropy.</para>
X </listitem>
X </orderedlist>
X
X <para>Suppose you could measure the entropy of the data to- and
X from- your network interface. Then you could see the difference
X between unencrypted data and encrypted data. This would be true
X even if some of the data in <quote>encrypted mode</quote> was
X not encrypted---as the outermost IP header must be, if the
X packet is to be routable.</para>
X
X <sect2 id="MUST">
X <title>MUST</title>
X
X <para>Ueli Maurer's <quote>Universal Statistical Test for Random
X Bit Generators</quote>(<ulink
X url="http://www.geocities.com/SiliconValley/Code/4704/universal.pdf">;
X <acronym>MUST</acronym></ulink>) quickly measures the entropy
X of a sample. It uses a compression-like algorithm. <link
X linkend="code">The code is given below</link> for a variant
X which measures successive (~quarter megabyte) chunks of a
X file.</para>
X </sect2>
X
X <sect2 id="tcpdump">
X <title>Tcpdump</title>
X
X <para>We also need a way to capture the raw network data. A
X program called &man.tcpdump.1; lets you do this, if you have
X enabled the <emphasis>Berkeley Packet Filter</emphasis>
X interface in your <link linkend="kernel">kernel's config
X file</link>.</para>
X
X <para>The command
X
X <screen>
X <userinput><command>tcpdump</command> -c 4000 -s 10000 -w <replaceable>dumpfile.bin</replaceable></userinput>
X </screen>
X
X will capture 4000 raw packets to
X <replaceable>dumpfile.bin</replaceable>. Up to 10,000 bytes per
X packet will be captured in this example.</para>
X </sect2>
X
X <sect1>
X <title>The Experiment</title>
X
X <para>Here's the experiment.</para>
X
X <procedure>
X <step>
X <para>Open a window to an IPsec host and another window to an
X insecure host.</para>
X </step>
X
X <step>
X <para>Now start <link linkend="tcpdump">capturing
X packets</link>.</para>
X </step>
X
X <step>
X <para>In the <quote>secure</quote> window, run the UNIX
X command &man.yes.1;, which will stream the <quote>y</quote>
X character. After a while, stop this. Switch to the
X insecure window, and repeat. After a while, stop.</para>
X </step>
X
X <step>
X <para>Now run <link linkend="code">MUST</link> on the
X captured packets. You should see something like the
X following. The important thing to note is that the secure
X connection has 93% (6.7) of the expected value (7.18), and
X the <quote>normal</quote> connection has 29% (2.1) of the
X expected value.</para>
X
X <screen>
X&prompt.user; <userinput>tcpdump -c 4000 -s 10000 -w <replaceable>ipsecdemo.bin</replaceable></userinput>
X&prompt.user; <userinput>uliscan <replaceable>ipsecdemo.bin</replaceable></userinput>
X
XUliscan 21 Dec 98
XL=8 256 258560
XMeasuring file ipsecdemo.bin
XInit done
XExpected value for L=8 is 7.1836656
X6.9396 --------------------------------------------------------
X6.6177 -----------------------------------------------------
X6.4100 ---------------------------------------------------
X2.1101 -----------------
X2.0838 -----------------
X2.0983 -----------------
X</screen>
X </step>
X </procedure>
X </sect1>
X
X <sect1 id="caveat">
X <title>Caveat</title>
X
X <para>This experiment shows that IPsec <emphasis>does</emphasis>
X seem to be distributing the payload data
X <emphasis>uniformly</emphasis>, as encryption should. However,
X the experiment described here <emphasis>can not</emphasis>
X detect many possible flaws in a system (none of which do I have
X any evidence for). These include poor key generation or
X exchange, data or keys being visible to others, use of weak
X algorithms, kernel subversion, etc. Study the source; know the
X code.</para>
X </sect1>
X
X <sect1 id="IPsec">
X <title>IPsec---Definition</title>
X
X <para>Internet Protocol security extensions to IPv4; required for
X IPv6. A protocol for negotiating encryption and authentication
X at the IP (host-to-host) level. SSL secures only one application
X socket; <application>SSH</application> secures only a login;
X <application>PGP</application> secures only a specified file or
X message. IPsec encrypts everything between two hosts.</para>
X </sect1>
X
X <sect1 id="ipsec-install">
X <title>Installing IPsec</title>
X
X <para>Most of the modern versions of FreeBSD have IPsec support
X in their base source. So you'll probably will need to include
X <option>IPSEC</option> option in your kernel config and, after
X kernel rebuild and reinstall, configure IPsec connections using
X &man.setkey.8; command.</para>
X
X <para>A comprehensive guide on running IPsec on FreeBSD is
X provided in <ulink
X url="http://www.freebsd.org/handbook/ipsec.html">FreeBSD
X Handbook</ulink>.</para>
X </sect1>
X
X <sect1 id="kernel">
X <title>usr/src/sys/i386/conf/KERNELNAME</title>
X
X <para>This needs to be present in the kernel config file in order
X to be able to capture network data with &man.tcpdump.1;. Be sure
X to run &man.config.8; after adding this, and rebuild and
X reinstall.</para>
X
X<programlisting>
Xdevice bpf
X</programlisting>
X </sect1>
X
X <sect1 id="code">
X <title>Maurer's Universal Statistical Test (for block size=8
X bits)</title>
X
X <para>You can find the same code at <ulink
X url="http://www.geocities.com/SiliconValley/Code/4704/uliscanc.txt">;
X this link</ulink>.</para>
X
X<programlisting>
X/*
X ULISCAN.c ---blocksize of 8
X
X 1 Oct 98
X 1 Dec 98
X 21 Dec 98 uliscan.c derived from ueli8.c
X
X This version has // comments removed for Sun cc
X
X This implements Ueli M Maurer's "Universal Statistical Test for Random
X Bit Generators" using L=8
X
X Accepts a filename on the command line; writes its results, with other
X info, to stdout.
X
X Handles input file exhaustion gracefully.
X
X Ref: J. Cryptology v 5 no 2, 1992 pp 89-105
X also on the web somewhere, which is where I found it.
X
X -David Honig
X honig@sprynet.com
X
X Usage:
X ULISCAN filename
X outputs to stdout
X*/
X
X#define L 8
X#define V (1<<L)
X#define Q (10*V)
X#define K (100 *Q)
X#define MAXSAMP (Q + K)
X
X#include <stdio.h>
X#include <math.h>
X
Xint main(argc, argv)
Xint argc;
Xchar **argv;
X{
X FILE *fptr;
X int i,j;
X int b, c;
X int table[V];
X double sum = 0.0;
X int iproduct = 1;
X int run;
X
X extern double log(/* double x */);
X
X printf("Uliscan 21 Dec 98 \nL=%d %d %d \n", L, V, MAXSAMP);
X
X if (argc < 2) {
X printf("Usage: Uliscan filename\n");
X exit(-1);
X } else {
X printf("Measuring file %s\n", argv[1]);
X }
X
X fptr = fopen(argv[1],"rb");
X
X if (fptr == NULL) {
X printf("Can't find %s\n", argv[1]);
X exit(-1);
X }
X
X for (i = 0; i < V; i++) {
X table[i] = 0;
X }
X
X for (i = 0; i < Q; i++) {
X b = fgetc(fptr);
X table[b] = i;
X }
X
X printf("Init done\n");
X
X printf("Expected value for L=8 is 7.1836656\n");
X
X run = 1;
X
X while (run) {
X sum = 0.0;
X iproduct = 1;
X
X if (run)
X for (i = Q; run && i < Q + K; i++) {
X j = i;
X b = fgetc(fptr);
X
X if (b < 0)
X run = 0;
X
X if (run) {
X if (table[b] > j)
X j += K;
X
X sum += log((double)(j-table[b]));
X
X table[b] = i;
X }
X }
X
X if (!run)
X printf("Premature end of file; read %d blocks.\n", i - Q);
X
X sum = (sum/((double)(i - Q))) / log(2.0);
X printf("%4.4f ", sum);
X
X for (i = 0; i < (int)(sum*8.0 + 0.50); i++)
X printf("-");
X
X printf("\n");
X
X /* refill initial table */
X if (0) {
X for (i = 0; i < Q; i++) {
X b = fgetc(fptr);
X if (b < 0) {
X run = 0;
X } else {
X table[b] = i;
X }
X }
X }
X }
X}
X</programlisting>
X </sect1>
X</article>
END-of-article.sgml
exit
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