blog/Automatic_proxy_configuration_with_Debian_Edu___Skolelinux.html

   1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
   2           "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
   3 <html xmlns="http://www.w3.org/1999/xhtml" dir="ltr">
   4   <head>
   5     <meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
   6     <title>Petter Reinholdtsen: Automatic proxy configuration with Debian Edu / Skolelinux</title>
   7     <link rel="stylesheet" type="text/css" media="screen" href="http://people.skolelinux.org/pere/blog/style.css" />
   8     <link rel="stylesheet" type="text/css" media="screen" href="http://people.skolelinux.org/pere/blog/vim.css" />
   9
  10
  11   </head>
  12   <body>
  13     <div class="title">
  14  <h1>
  15      <a href="http://people.skolelinux.org/pere/blog/">Petter Reinholdtsen</a>
  16
  17  </h1>
  18
  19 </div>
  20
  21
  22     <div class="entry">
  23       <div class="title">Automatic proxy configuration with Debian Edu / Skolelinux</div>
  24       <div class="date">13th February 2012</div>
  25       <div class="body"><p>New in the Squeeze version of
  26 <a href="http://www.skolelinux.org/">Debian Edu / Skolelinux</a> is the
  27 ability for clients to automatically configure their proxy settings
  28 based on their environment.  We want all systems on the client to use
  29 the WPAD based proxy definition fetched from <tt>http://wpad/wpad.dat</tt>, to
  30 allow sites to control the proxy setting from a central place and make
  31 sure clients do not have hard coded proxy settings.  The schools can
  32 change the global proxy setting by editing
  33 <tt>tjener:/etc/debian-edu/www/wpad.dat</tt> and the change propagate
  34 to all Debian Edu clients in the network.</p>
  35
  36 <p>The problem is that some systems do not understand the WPAD system.
  37 In other words, how do one get from a WPAD file like this (this is a
  38 simple one, they can run arbitrary code):</p>
  39
  40 <blockquote><pre>
  41 function FindProxyForURL(url, host)
  42 {
  43    if (!isResolvable(host) ||
  44        isPlainHostName(host) ||
  45        dnsDomainIs(host, ".intern"))
  46       return "DIRECT";
  47    else
  48       return "PROXY webcache:3128; DIRECT";
  49 }
  50 </pre></blockquote>
  51
  52 <p>to a proxy setting in the process environment looking like this:</p>
  53
  54 <blockquote><pre>
  55 http_proxy=http://webcache:3128/
  56 ftp_proxy=http://webcache:3128/
  57 </pre></blockquote>
  58
  59 <p>To do this conversion I developed a perl script that will execute
  60 the javascript fragment in the WPAD file and return the proxy that
  61 would be used for
  62 <tt><a href="http://www.debian.org/">http://www.debian.org/</a></tt>,
  63 and insert this extracted proxy URL in <tt>/etc/environment</tt> and
  64 <tt>/etc/apt/apt.conf</tt>.  The perl script wpad-extract work just
  65 fine in Squeeze, but in Wheezy the library it need to run the
  66 javascript code is <a href="http://bugs.debian.org/631045">no longer
  67 able to build</a> because the C library it depended on is now a C++
  68 library.  I hope someone find a solution to that problem before Wheezy
  69 is frozen.  An alternative would be for us to rewrite wpad-extract to
  70 use some other javascript library currently working in Wheezy, but no
  71 known alternative is known at the moment.</p>
  72
  73 <p>This automatic proxy system allow the roaming workstation (aka
  74 laptop) setup in Debian Edu/Squeeze to use the proxy when the laptop
  75 is connected to the backbone network in a Debian Edu setup, and to
  76 automatically use any proxy present and announced using the WPAD
  77 feature when it is connected to other networks.  And if no proxy is
  78 announced, direct connections will be used instead.</p>
  79
  80 <p>Silently using a proxy announced on the network might be a privacy
  81 or security problem.  But those controlling DHCP and DNS on a network
  82 could just as easily set up a transparent proxy, and force all HTTP
  83 and FTP connections to use a proxy anyway, so I consider that
  84 distinction to be academic.  If you are afraid of using the wrong
  85 proxy, you should avoid connecting to the network in question in the
  86 first place.  In Debian Edu, the proxy setup is updated using dhcp and
  87 ifupdown hooks, to make sure the configuration is updated every time
  88 the network setup changes.</p>
  89
  90 <p>The WPAD system is documented in a
  91 <a href="http://tools.ietf.org/html/draft-ietf-wrec-wpad-01">IETF
  92 draft</a> and a
  93 <a href="http://en.wikipedia.org/wiki/Web_Proxy_Autodiscovery_Protocol">Wikipedia
  94 page</a> for those that want to learn more.</p>
  95 </div>
  96
  97       <div class="tags">Tags: <a href="http://people.skolelinux.org/pere/blog/tags/debian edu">debian edu</a>, <a href="http://people.skolelinux.org/pere/blog/tags/english">english</a>.</div>
  98
  99
 100     </div>
 101
 102
 103
 104
 105     <div id="sidebar">
 106
 107
 108
 109 <h2>Archive</h2>
 110 <ul>
 111
 112 <li>2015
 113 <ul>
 114
 115 <li><a href="http://people.skolelinux.org/pere/blog/archive/2015/01/">January (2)</a></li>
 116
 117 </ul></li>
 118
 119 <li>2014
 120 <ul>
 121
 122 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/01/">January (2)</a></li>
 123
 124 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/02/">February (3)</a></li>
 125
 126 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/03/">March (8)</a></li>
 127
 128 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/04/">April (7)</a></li>
 129
 130 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/05/">May (1)</a></li>
 131
 132 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/06/">June (2)</a></li>
 133
 134 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/07/">July (2)</a></li>
 135
 136 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/08/">August (2)</a></li>
 137
 138 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/09/">September (5)</a></li>
 139
 140 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/10/">October (6)</a></li>
 141
 142 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/11/">November (3)</a></li>
 143
 144 <li><a href="http://people.skolelinux.org/pere/blog/archive/2014/12/">December (5)</a></li>
 145
 146 </ul></li>
 147
 148 <li>2013
 149 <ul>
 150
 151 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/01/">January (11)</a></li>
 152
 153 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/02/">February (9)</a></li>
 154
 155 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/03/">March (9)</a></li>
 156
 157 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/04/">April (6)</a></li>
 158
 159 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/05/">May (9)</a></li>
 160
 161 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/06/">June (10)</a></li>
 162
 163 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/07/">July (7)</a></li>
 164
 165 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/08/">August (3)</a></li>
 166
 167 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/09/">September (5)</a></li>
 168
 169 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/10/">October (7)</a></li>
 170
 171 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/11/">November (9)</a></li>
 172
 173 <li><a href="http://people.skolelinux.org/pere/blog/archive/2013/12/">December (3)</a></li>
 174
 175 </ul></li>
 176
 177 <li>2012
 178 <ul>
 179
 180 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/01/">January (7)</a></li>
 181
 182 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/02/">February (10)</a></li>
 183
 184 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/03/">March (17)</a></li>
 185
 186 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/04/">April (12)</a></li>
 187
 188 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/05/">May (12)</a></li>
 189
 190 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/06/">June (20)</a></li>
 191
 192 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/07/">July (17)</a></li>
 193
 194 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/08/">August (6)</a></li>
 195
 196 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/09/">September (9)</a></li>
 197
 198 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/10/">October (17)</a></li>
 199
 200 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/11/">November (10)</a></li>
 201
 202 <li><a href="http://people.skolelinux.org/pere/blog/archive/2012/12/">December (7)</a></li>
 203
 204 </ul></li>
 205
 206 <li>2011
 207 <ul>
 208
 209 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/01/">January (16)</a></li>
 210
 211 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/02/">February (6)</a></li>
 212
 213 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/03/">March (6)</a></li>
 214
 215 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/04/">April (7)</a></li>
 216
 217 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/05/">May (3)</a></li>
 218
 219 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/06/">June (2)</a></li>
 220
 221 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/07/">July (7)</a></li>
 222
 223 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/08/">August (6)</a></li>
 224
 225 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/09/">September (4)</a></li>
 226
 227 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/10/">October (2)</a></li>
 228
 229 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/11/">November (3)</a></li>
 230
 231 <li><a href="http://people.skolelinux.org/pere/blog/archive/2011/12/">December (1)</a></li>
 232
 233 </ul></li>
 234
 235 <li>2010
 236 <ul>
 237
 238 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/01/">January (2)</a></li>
 239
 240 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/02/">February (1)</a></li>
 241
 242 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/03/">March (3)</a></li>
 243
 244 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/04/">April (3)</a></li>
 245
 246 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/05/">May (9)</a></li>
 247
 248 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/06/">June (14)</a></li>
 249
 250 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/07/">July (12)</a></li>
 251
 252 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/08/">August (13)</a></li>
 253
 254 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/09/">September (7)</a></li>
 255
 256 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/10/">October (9)</a></li>
 257
 258 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/11/">November (13)</a></li>
 259
 260 <li><a href="http://people.skolelinux.org/pere/blog/archive/2010/12/">December (12)</a></li>
 261
 262 </ul></li>
 263
 264 <li>2009
 265 <ul>
 266
 267 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/01/">January (8)</a></li>
 268
 269 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/02/">February (8)</a></li>
 270
 271 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/03/">March (12)</a></li>
 272
 273 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/04/">April (10)</a></li>
 274
 275 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/05/">May (9)</a></li>
 276
 277 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/06/">June (3)</a></li>
 278
 279 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/07/">July (4)</a></li>
 280
 281 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/08/">August (3)</a></li>
 282
 283 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/09/">September (1)</a></li>
 284
 285 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/10/">October (2)</a></li>
 286
 287 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/11/">November (3)</a></li>
 288
 289 <li><a href="http://people.skolelinux.org/pere/blog/archive/2009/12/">December (3)</a></li>
 290
 291 </ul></li>
 292
 293 <li>2008
 294 <ul>
 295
 296 <li><a href="http://people.skolelinux.org/pere/blog/archive/2008/11/">November (5)</a></li>
 297
 298 <li><a href="http://people.skolelinux.org/pere/blog/archive/2008/12/">December (7)</a></li>
 299
 300 </ul></li>
 301
 302 </ul>
 303
 304
 305
 306 <h2>Tags</h2>
 307 <ul>
 308
 309  <li><a href="http://people.skolelinux.org/pere/blog/tags/3d-printer">3d-printer (13)</a></li>
 310
 311  <li><a href="http://people.skolelinux.org/pere/blog/tags/amiga">amiga (1)</a></li>
 312
 313  <li><a href="http://people.skolelinux.org/pere/blog/tags/aros">aros (1)</a></li>
 314
 315  <li><a href="http://people.skolelinux.org/pere/blog/tags/bankid">bankid (4)</a></li>
 316
 317  <li><a href="http://people.skolelinux.org/pere/blog/tags/bitcoin">bitcoin (8)</a></li>
 318
 319  <li><a href="http://people.skolelinux.org/pere/blog/tags/bootsystem">bootsystem (15)</a></li>
 320
 321  <li><a href="http://people.skolelinux.org/pere/blog/tags/bsa">bsa (2)</a></li>
 322
 323  <li><a href="http://people.skolelinux.org/pere/blog/tags/chrpath">chrpath (2)</a></li>
 324
 325  <li><a href="http://people.skolelinux.org/pere/blog/tags/debian">debian (109)</a></li>
 326
 327  <li><a href="http://people.skolelinux.org/pere/blog/tags/debian edu">debian edu (151)</a></li>
 328
 329  <li><a href="http://people.skolelinux.org/pere/blog/tags/digistan">digistan (10)</a></li>
 330
 331  <li><a href="http://people.skolelinux.org/pere/blog/tags/dld">dld (15)</a></li>
 332
 333  <li><a href="http://people.skolelinux.org/pere/blog/tags/docbook">docbook (12)</a></li>
 334
 335  <li><a href="http://people.skolelinux.org/pere/blog/tags/drivstoffpriser">drivstoffpriser (4)</a></li>
 336
 337  <li><a href="http://people.skolelinux.org/pere/blog/tags/english">english (265)</a></li>
 338
 339  <li><a href="http://people.skolelinux.org/pere/blog/tags/fiksgatami">fiksgatami (22)</a></li>
 340
 341  <li><a href="http://people.skolelinux.org/pere/blog/tags/fildeling">fildeling (12)</a></li>
 342
 343  <li><a href="http://people.skolelinux.org/pere/blog/tags/freeculture">freeculture (14)</a></li>
 344
 345  <li><a href="http://people.skolelinux.org/pere/blog/tags/freedombox">freedombox (9)</a></li>
 346
 347  <li><a href="http://people.skolelinux.org/pere/blog/tags/frikanalen">frikanalen (11)</a></li>
 348
 349  <li><a href="http://people.skolelinux.org/pere/blog/tags/intervju">intervju (41)</a></li>
 350
 351  <li><a href="http://people.skolelinux.org/pere/blog/tags/isenkram">isenkram (10)</a></li>
 352
 353  <li><a href="http://people.skolelinux.org/pere/blog/tags/kart">kart (19)</a></li>
 354
 355  <li><a href="http://people.skolelinux.org/pere/blog/tags/ldap">ldap (9)</a></li>
 356
 357  <li><a href="http://people.skolelinux.org/pere/blog/tags/lenker">lenker (8)</a></li>
 358
 359  <li><a href="http://people.skolelinux.org/pere/blog/tags/lsdvd">lsdvd (2)</a></li>
 360
 361  <li><a href="http://people.skolelinux.org/pere/blog/tags/ltsp">ltsp (1)</a></li>
 362
 363  <li><a href="http://people.skolelinux.org/pere/blog/tags/mesh network">mesh network (8)</a></li>
 364
 365  <li><a href="http://people.skolelinux.org/pere/blog/tags/multimedia">multimedia (32)</a></li>
 366
 367  <li><a href="http://people.skolelinux.org/pere/blog/tags/norsk">norsk (254)</a></li>
 368
 369  <li><a href="http://people.skolelinux.org/pere/blog/tags/nuug">nuug (167)</a></li>
 370
 371  <li><a href="http://people.skolelinux.org/pere/blog/tags/offentlig innsyn">offentlig innsyn (11)</a></li>
 372
 373  <li><a href="http://people.skolelinux.org/pere/blog/tags/open311">open311 (2)</a></li>
 374
 375  <li><a href="http://people.skolelinux.org/pere/blog/tags/opphavsrett">opphavsrett (50)</a></li>
 376
 377  <li><a href="http://people.skolelinux.org/pere/blog/tags/personvern">personvern (81)</a></li>
 378
 379  <li><a href="http://people.skolelinux.org/pere/blog/tags/raid">raid (1)</a></li>
 380
 381  <li><a href="http://people.skolelinux.org/pere/blog/tags/reactos">reactos (1)</a></li>
 382
 383  <li><a href="http://people.skolelinux.org/pere/blog/tags/reprap">reprap (11)</a></li>
 384
 385  <li><a href="http://people.skolelinux.org/pere/blog/tags/rfid">rfid (3)</a></li>
 386
 387  <li><a href="http://people.skolelinux.org/pere/blog/tags/robot">robot (9)</a></li>
 388
 389  <li><a href="http://people.skolelinux.org/pere/blog/tags/rss">rss (1)</a></li>
 390
 391  <li><a href="http://people.skolelinux.org/pere/blog/tags/ruter">ruter (4)</a></li>
 392
 393  <li><a href="http://people.skolelinux.org/pere/blog/tags/scraperwiki">scraperwiki (2)</a></li>
 394
 395  <li><a href="http://people.skolelinux.org/pere/blog/tags/sikkerhet">sikkerhet (41)</a></li>
 396
 397  <li><a href="http://people.skolelinux.org/pere/blog/tags/sitesummary">sitesummary (4)</a></li>
 398
 399  <li><a href="http://people.skolelinux.org/pere/blog/tags/skepsis">skepsis (4)</a></li>
 400
 401  <li><a href="http://people.skolelinux.org/pere/blog/tags/standard">standard (46)</a></li>
 402
 403  <li><a href="http://people.skolelinux.org/pere/blog/tags/stavekontroll">stavekontroll (3)</a></li>
 404
 405  <li><a href="http://people.skolelinux.org/pere/blog/tags/stortinget">stortinget (9)</a></li>
 406
 407  <li><a href="http://people.skolelinux.org/pere/blog/tags/surveillance">surveillance (29)</a></li>
 408
 409  <li><a href="http://people.skolelinux.org/pere/blog/tags/sysadmin">sysadmin (2)</a></li>
 410
 411  <li><a href="http://people.skolelinux.org/pere/blog/tags/usenix">usenix (2)</a></li>
 412
 413  <li><a href="http://people.skolelinux.org/pere/blog/tags/valg">valg (8)</a></li>
 414
 415  <li><a href="http://people.skolelinux.org/pere/blog/tags/video">video (46)</a></li>
 416
 417  <li><a href="http://people.skolelinux.org/pere/blog/tags/vitenskap">vitenskap (4)</a></li>
 418
 419  <li><a href="http://people.skolelinux.org/pere/blog/tags/web">web (34)</a></li>
 420
 421 </ul>
 422
 423
 424     </div>
 425     <p style="text-align: right">
 426  Created by <a href="http://steve.org.uk/Software/chronicle">Chronicle v4.6</a>
 427 </p>
 428
 429   </body>
 430 </html>