X-Git-Url: http://pere.pagekite.me/gitweb/homepage.git/blobdiff_plain/2377a19a2fcd67c09830cbb4a2a81cfd5a6f00d6..6a58d21ef026fad6b251d1dec5cab28df9243a9b:/blog/index.html diff --git a/blog/index.html b/blog/index.html index 6fd3994470..7ee76c94b8 100644 --- a/blog/index.html +++ b/blog/index.html @@ -19,6 +19,103 @@ +
+
Simpler recipe on how to make a simple $7 IMSI Catcher using Debian
+
9th August 2017
+

On friday, I came across an interesting article in the Norwegian +web based ICT news magazine digi.no on +how +to collect the IMSI numbers of nearby cell phones using the cheap +DVB-T software defined radios. The article refered to instructions +and a recipe by +Keld Norman on Youtube on how to make a simple $7 IMSI Catcher, and I decided to test them out.

+ +

The instructions said to use Ubuntu, install pip using apt (to +bypass apt), use pip to install pybombs (to bypass both apt and pip), +and the ask pybombs to fetch and build everything you need from +scratch. I wanted to see if I could do the same on the most recent +Debian packages, but this did not work because pybombs tried to build +stuff that no longer build with the most recent openssl library or +some other version skew problem. While trying to get this recipe +working, I learned that the apt->pip->pybombs route was a long detour, +and the only piece of software dependency missing in Debian was the +gr-gsm package. I also found out that the lead upstream developer of +gr-gsm (the name stand for GNU Radio GSM) project already had a set of +Debian packages provided in an Ubuntu PPA repository. All I needed to +do was to dget the Debian source package and built it.

+ +

The IMSI collector is a python script listening for packages on the +loopback network device and printing to the terminal some specific GSM +packages with IMSI numbers in them. The code is fairly short and easy +to understand. The reason this work is because gr-gsm include a tool +to read GSM data from a software defined radio like a DVB-T USB stick +and other software defined radios, decode them and inject them into a +network device on your Linux machine (using the loopback device by +default). This proved to work just fine, and I've been testing the +collector for a few days now.

+ +

The updated and simpler recipe is thus to

+ +
    + +
  1. start with a Debian machine running Stretch or newer,
    2. + +
  2. build and install the gr-gsm package available from +http://ppa.launchpad.net/ptrkrysik/gr-gsm/ubuntu/pool/main/g/gr-gsm/,
    3. + +
  3. clone the git repostory from https://github.com/Oros42/IMSI-catcher,
    4. + +
  4. run grgsm_livemon and adjust the frequency until the terminal +where it was started is filled with a stream of text (meaning you +found a GSM station).
    5. + +
  5. go into the IMSI-catcher directory and run 'sudo python simple_IMSI-catcher.py' to extract the IMSI numbers.
    6. + +
+ +

To make it even easier in the future to get this sniffer up and +running, I decided to package +the gr-gsm project +for Debian (WNPP +#871055), and the package was uploaded into the NEW queue today. +Luckily the gnuradio maintainer has promised to help me, as I do not +know much about gnuradio stuff yet.

+ +

I doubt this "IMSI cacher" is anywhere near as powerfull as +commercial tools like +The +Spy Phone Portable IMSI / IMEI Catcher or the +Harris +Stingray, but I hope the existance of cheap alternatives can make +more people realise how their whereabouts when carrying a cell phone +is easily tracked. Seeing the data flow on the screen, realizing that +I live close to a police station and knowing that the police is also +wearing cell phones, I wonder how hard it would be for criminals to +track the position of the police officers to discover when there are +police near by, or for foreign military forces to track the location +of the Norwegian military forces, or for anyone to track the location +of government officials...

+ +

It is worth noting that the data reported by the IMSI-catcher +script mentioned above is only a fraction of the data broadcasted on +the GSM network. It will only collect one frequency at the time, +while a typical phone will be using several frequencies, and not all +phones will be using the frequencies tracked by the grgsm_livemod +program. Also, there is a lot of radio chatter being ignored by the +simple_IMSI-catcher script, which would be collected by extending the +parser code. I wonder if gr-gsm can be set up to listen to more than +one frequency?

+
+
+ + + Tags: debian, english, personvern, surveillance. + + +
+
+
+
Norwegian Bokmål edition of Debian Administrator's Handbook is now available
25th July 2017
@@ -620,121 +717,6 @@ implemented in Python.

-
-
Detecting NFS hangs on Linux without hanging yourself...
-
9th March 2017
-

Over the years, administrating thousand of NFS mounting linux -computers at the time, I often needed a way to detect if the machine -was experiencing NFS hang. If you try to use df or look at a -file or directory affected by the hang, the process (and possibly the -shell) will hang too. So you want to be able to detect this without -risking the detection process getting stuck too. It has not been -obvious how to do this. When the hang has lasted a while, it is -possible to find messages like these in dmesg:

- -

-nfs: server nfsserver not responding, still trying -
nfs: server nfsserver OK -

- -

It is hard to know if the hang is still going on, and it is hard to -be sure looking in dmesg is going to work. If there are lots of other -messages in dmesg the lines might have rotated out of site before they -are noticed.

- -

While reading through the nfs client implementation in linux kernel -code, I came across some statistics that seem to give a way to detect -it. The om_timeouts sunrpc value in the kernel will increase every -time the above log entry is inserted into dmesg. And after digging a -bit further, I discovered that this value show up in -/proc/self/mountstats on Linux.

- -

The mountstats content seem to be shared between files using the -same file system context, so it is enough to check one of the -mountstats files to get the state of the mount point for the machine. -I assume this will not show lazy umounted NFS points, nor NFS mount -points in a different process context (ie with a different filesystem -view), but that does not worry me.

- -

The content for a NFS mount point look similar to this:

- -

-[...]
-device /dev/mapper/Debian-var mounted on /var with fstype ext3
-device nfsserver:/mnt/nfsserver/home0 mounted on /mnt/nfsserver/home0 with fstype nfs statvers=1.1
-        opts:   rw,vers=3,rsize=65536,wsize=65536,namlen=255,acregmin=3,acregmax=60,acdirmin=30,acdirmax=60,soft,nolock,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=129.240.3.145,mountvers=3,mountport=4048,mountproto=udp,local_lock=all
-        age:    7863311
-        caps:   caps=0x3fe7,wtmult=4096,dtsize=8192,bsize=0,namlen=255
-        sec:    flavor=1,pseudoflavor=1
-        events: 61063112 732346265 1028140 35486205 16220064 8162542 761447191 71714012 37189 3891185 45561809 110486139 4850138 420353 15449177 296502 52736725 13523379 0 52182 9016896 1231 0 0 0 0 0 
-        bytes:  166253035039 219519120027 0 0 40783504807 185466229638 11677877 45561809 
-        RPC iostats version: 1.0  p/v: 100003/3 (nfs)
-        xprt:   tcp 925 1 6810 0 0 111505412 111480497 109 2672418560317 0 248 53869103 22481820
-        per-op statistics
-                NULL: 0 0 0 0 0 0 0 0
-             GETATTR: 61063106 61063108 0 9621383060 6839064400 453650 77291321 78926132
-             SETATTR: 463469 463470 0 92005440 66739536 63787 603235 687943
-              LOOKUP: 17021657 17021657 0 3354097764 4013442928 57216 35125459 35566511
-              ACCESS: 14281703 14290009 5 2318400592 1713803640 1709282 4865144 7130140
-            READLINK: 125 125 0 20472 18620 0 1112 1118
-                READ: 4214236 4214237 0 715608524 41328653212 89884 22622768 22806693
-               WRITE: 8479010 8494376 22 187695798568 1356087148 178264904 51506907 231671771
-              CREATE: 171708 171708 0 38084748 46702272 873 1041833 1050398
-               MKDIR: 3680 3680 0 773980 993920 26 23990 24245
-             SYMLINK: 903 903 0 233428 245488 6 5865 5917
-               MKNOD: 80 80 0 20148 21760 0 299 304
-              REMOVE: 429921 429921 0 79796004 61908192 3313 2710416 2741636
-               RMDIR: 3367 3367 0 645112 484848 22 5782 6002
-              RENAME: 466201 466201 0 130026184 121212260 7075 5935207 5961288
-                LINK: 289155 289155 0 72775556 67083960 2199 2565060 2585579
-             READDIR: 2933237 2933237 0 516506204 13973833412 10385 3190199 3297917
-         READDIRPLUS: 1652839 1652839 0 298640972 6895997744 84735 14307895 14448937
-              FSSTAT: 6144 6144 0 1010516 1032192 51 9654 10022
-              FSINFO: 2 2 0 232 328 0 1 1
-            PATHCONF: 1 1 0 116 140 0 0 0
-              COMMIT: 0 0 0 0 0 0 0 0
-
-device binfmt_misc mounted on /proc/sys/fs/binfmt_misc with fstype binfmt_misc
-[...]
-

- -

The key number to look at is the third number in the per-op list. -It is the number of NFS timeouts experiences per file system -operation. Here 22 write timeouts and 5 access timeouts. If these -numbers are increasing, I believe the machine is experiencing NFS -hang. Unfortunately the timeout value do not start to increase right -away. The NFS operations need to time out first, and this can take a -while. The exact timeout value depend on the setup. For example the -defaults for TCP and UDP mount points are quite different, and the -timeout value is affected by the soft, hard, timeo and retrans NFS -mount options.

- -

The only way I have been able to get working on Debian and RedHat -Enterprise Linux for getting the timeout count is to peek in /proc/. -But according to -Solaris -10 System Administration Guide: Network Services, the 'nfsstat -c' -command can be used to get these timeout values. But this do not work -on Linux, as far as I can tell. I -asked Debian about this, -but have not seen any replies yet.

- -

Is there a better way to figure out if a Linux NFS client is -experiencing NFS hangs? Is there a way to detect which processes are -affected? Is there a way to get the NFS mount going quickly once the -network problem causing the NFS hang has been cleared? I would very -much welcome some clues, as we regularly run into NFS hangs.

-
-
- - - Tags: debian, english, sysadmin. - - -
-
-
-

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