- <title>A program should be able to open its own files on Linux</title>
- <link>http://people.skolelinux.org/pere/blog/A_program_should_be_able_to_open_its_own_files_on_Linux.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/A_program_should_be_able_to_open_its_own_files_on_Linux.html</guid>
- <pubDate>Sun, 5 Jun 2016 08:30:00 +0200</pubDate>
- <description><p>Many years ago, when koffice was fresh and with few users, I
-decided to test its presentation tool when making the slides for a
-talk I was giving for NUUG on Japhar, a free Java virtual machine. I
-wrote the first draft of the slides, saved the result and went to bed
-the day before I would give the talk. The next day I took a plane to
-the location where the meeting should take place, and on the plane I
-started up koffice again to polish the talk a bit, only to discover
-that kpresenter refused to load its own data file. I cursed a bit and
-started making the slides again from memory, to have something to
-present when I arrived. I tested that the saved files could be
-loaded, and the day seemed to be rescued. I continued to polish the
-slides until I suddenly discovered that the saved file could no longer
-be loaded into kpresenter. In the end I had to rewrite the slides
-three times, condensing the content until the talk became shorter and
-shorter. After the talk I was able to pinpoint the problem &ndash;
-kpresenter wrote inline images in a way itself could not understand.
-Eventually that bug was fixed and kpresenter ended up being a great
-program to make slides. The point I'm trying to make is that we
-expect a program to be able to load its own data files, and it is
-embarrassing to its developers if it can't.</p>
-
-<p>Did you ever experience a program failing to load its own data
-files from the desktop file browser? It is not a uncommon problem. A
-while back I discovered that the screencast recorder
-gtk-recordmydesktop would save an Ogg Theora video file the KDE file
-browser would refuse to open. No video player claimed to understand
-such file. I tracked down the cause being <tt>file --mime-type</tt>
-returning the application/ogg MIME type, which no video player I had
-installed listed as a MIME type they would understand. I asked for
-<a href="http://bugs.gw.com/view.php?id=382">file to change its
-behavour</a> and use the MIME type video/ogg instead. I also asked
-several video players to add video/ogg to their desktop files, to give
-the file browser an idea what to do about Ogg Theora files. After a
-while, the desktop file browsers in Debian started to handle the
-output from gtk-recordmydesktop properly.</p>
-
-<p>But history repeats itself. A few days ago I tested the music
-system Rosegarden again, and I discovered that the KDE and xfce file
-browsers did not know what to do with the Rosegarden project files
-(*.rg). I've reported <a href="http://bugs.debian.org/825993">the
-rosegarden problem to BTS</a> and a fix is commited to git and will be
-included in the next upload. To increase the chance of me remembering
-how to fix the problem next time some program fail to load its files
-from the file browser, here are some notes on how to fix it.</p>
-
-<p>The file browsers in Debian in general operates on MIME types.
-There are two sources for the MIME type of a given file. The output from
-<tt>file --mime-type</tt> mentioned above, and the content of the
-shared MIME type registry (under /usr/share/mime/). The file MIME
-type is mapped to programs supporting the MIME type, and this
-information is collected from
-<a href="https://www.freedesktop.org/wiki/Specifications/desktop-entry-spec/">the
-desktop files</a> available in /usr/share/applications/. If there is
-one desktop file claiming support for the MIME type of the file, it is
-activated when asking to open a given file. If there are more, one
-can normally select which one to use by right-clicking on the file and
-selecting the wanted one using 'Open with' or similar. In general
-this work well. But it depend on each program picking a good MIME
-type (preferably
-<a href="http://www.iana.org/assignments/media-types/media-types.xhtml">a
-MIME type registered with IANA</a>), file and/or the shared MIME
-registry recognizing the file and the desktop file to list the MIME
-type in its list of supported MIME types.</p>
-
-<p>The <tt>/usr/share/mime/packages/rosegarden.xml</tt> entry for
-<a href="http://www.freedesktop.org/wiki/Specifications/shared-mime-info-spec">the
-Shared MIME database</a> look like this:</p>
-
-<p><blockquote><pre>
-&lt;?xml version="1.0" encoding="UTF-8"?&gt;
-&lt;mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info"&gt;
- &lt;mime-type type="audio/x-rosegarden"&gt;
- &lt;sub-class-of type="application/x-gzip"/&gt;
- &lt;comment&gt;Rosegarden project file&lt;/comment&gt;
- &lt;glob pattern="*.rg"/&gt;
- &lt;/mime-type&gt;
-&lt;/mime-info&gt;
-</pre></blockquote></p>
-
-<p>This states that audio/x-rosegarden is a kind of application/x-gzip
-(it is a gzipped XML file). Note, it is much better to use an
-official MIME type registered with IANA than it is to make up ones own
-unofficial ones like the x-rosegarden type used by rosegarden.</p>
-
-<p>The desktop file of the rosegarden program failed to list
-audio/x-rosegarden in its list of supported MIME types, causing the
-file browsers to have no idea what to do with *.rg files:</p>
-
-<p><blockquote><pre>
-% grep Mime /usr/share/applications/rosegarden.desktop
-MimeType=audio/x-rosegarden-composition;audio/x-rosegarden-device;audio/x-rosegarden-project;audio/x-rosegarden-template;audio/midi;
-X-KDE-NativeMimeType=audio/x-rosegarden-composition
-%
-</pre></blockquote></p>
-
-<p>The fix was to add "audio/x-rosegarden;" at the end of the
-MimeType= line.</p>
-
-<p>If you run into a file which fail to open the correct program when
-selected from the file browser, please check out the output from
-<tt>file --mime-type</tt> for the file, ensure the file ending and
-MIME type is registered somewhere under /usr/share/mime/ and check
-that some desktop file under /usr/share/applications/ is claiming
-support for this MIME type. If not, please report a bug to have it
-fixed. :)</p>
+ <title>Easier recipe to observe the cell phones around you</title>
+ <link>http://people.skolelinux.org/pere/blog/Easier_recipe_to_observe_the_cell_phones_around_you.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Easier_recipe_to_observe_the_cell_phones_around_you.html</guid>
+ <pubDate>Sun, 24 Sep 2017 08:30:00 +0200</pubDate>
+ <description><p>A little more than a month ago I wrote
+<a href="http://people.skolelinux.org/pere/blog/Simpler_recipe_on_how_to_make_a_simple__7_IMSI_Catcher_using_Debian.html">how
+to observe the SIM card ID (aka IMSI number) of mobile phones talking
+to nearby mobile phone base stations using Debian GNU/Linux and a
+cheap USB software defined radio</a>, and thus being able to pinpoint
+the location of people and equipment (like cars and trains) with an
+accuracy of a few kilometer. Since then we have worked to make the
+procedure even simpler, and it is now possible to do this without any
+manual frequency tuning and without building your own packages.</p>
+
+<p>The <a href="https://tracker.debian.org/pkg/gr-gsm">gr-gsm</a>
+package is now included in Debian testing and unstable, and the
+IMSI-catcher code no longer require root access to fetch and decode
+the GSM data collected using gr-gsm.</p>
+
+<p>Here is an updated recipe, using packages built by Debian and a git
+clone of two python scripts:</p>
+
+<ol>
+
+<li>Start with a Debian machine running the Buster version (aka
+ testing).</li>
+
+<li>Run '<tt>apt install gr-gsm python-numpy python-scipy
+ python-scapy</tt>' as root to install required packages.</li>
+
+<li>Fetch the code decoding GSM packages using '<tt>git clone
+ github.com/Oros42/IMSI-catcher.git</tt>'.</li>
+
+<li>Insert USB software defined radio supported by GNU Radio.</li>
+
+<li>Enter the IMSI-catcher directory and run '<tt>python
+ scan-and-livemon</tt>' to locate the frequency of nearby base
+ stations and start listening for GSM packages on one of them.</li>
+
+<li>Enter the IMSI-catcher directory and run '<tt>python
+ simple_IMSI-catcher.py</tt>' to display the collected information.</li>
+
+</ol>
+
+<p>Note, due to a bug somewhere the scan-and-livemon program (actually
+<a href="https://github.com/ptrkrysik/gr-gsm/issues/336">its underlying
+program grgsm_scanner</a>) do not work with the HackRF radio. It does
+work with RTL 8232 and other similar USB radio receivers you can get
+very cheaply
+(<a href="https://www.ebay.com/sch/items/?_nkw=rtl+2832">for example
+from ebay</a>), so for now the solution is to scan using the RTL radio
+and only use HackRF for fetching GSM data.</p>
+
+<p>As far as I can tell, a cell phone only show up on one of the
+frequencies at the time, so if you are going to track and count every
+cell phone around you, you need to listen to all the frequencies used.
+To listen to several frequencies, use the --numrecv argument to
+scan-and-livemon to use several receivers. Further, I am not sure if
+phones using 3G or 4G will show as talking GSM to base stations, so
+this approach might not see all phones around you. I typically see
+0-400 IMSI numbers an hour when looking around where I live.</p>
+
+<p>I've tried to run the scanner on a
+<a href="https://wiki.debian.org/RaspberryPi">Raspberry Pi 2 and 3
+running Debian Buster</a>, but the grgsm_livemon_headless process seem
+to be too CPU intensive to keep up. When GNU Radio print 'O' to
+stdout, I am told there it is caused by a buffer overflow between the
+radio and GNU Radio, caused by the program being unable to read the
+GSM data fast enough. If you see a stream of 'O's from the terminal
+where you started scan-and-livemon, you need a give the process more
+CPU power. Perhaps someone are able to optimize the code to a point
+where it become possible to set up RPi3 based GSM sniffers? I tried
+using Raspbian instead of Debian, but there seem to be something wrong
+with GNU Radio on raspbian, causing glibc to abort().</p>
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