X-Git-Url: http://pere.pagekite.me/gitweb/homepage.git/blobdiff_plain/6150c7a64a43c3644a1f02db495c0d22651e2624..48242bda221d48f034db275c4758ac81cc92d31b:/blog/index.rss diff --git a/blog/index.rss b/blog/index.rss index 2faa9a8da3..5756f07f83 100644 --- a/blog/index.rss +++ b/blog/index.rss @@ -6,6 +6,112 @@ http://people.skolelinux.org/pere/blog/ + + Fetching trusted timestamps using the rfc3161ng python module + http://people.skolelinux.org/pere/blog/Fetching_trusted_timestamps_using_the_rfc3161ng_python_module.html + http://people.skolelinux.org/pere/blog/Fetching_trusted_timestamps_using_the_rfc3161ng_python_module.html + Mon, 8 Oct 2018 12:30:00 +0200 + <p>I have earlier covered the basics of trusted timestamping using the +'openssl ts' client. See blog post for +<a href="http://people.skolelinux.org/pere/blog/Public_Trusted_Timestamping_services_for_everyone.html">2014</a>, +<a href="http://people.skolelinux.org/pere/blog/syslog_trusted_timestamp___chain_of_trusted_timestamps_for_your_syslog.html">2016</a> +and +<a href="http://people.skolelinux.org/pere/blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html">2017</a> +for those stories. But some times I want to integrate the timestamping +in other code, and recently I needed to integrate it into Python. +After searching a bit, I found +<a href="https://dev.entrouvert.org/projects/python-rfc3161">the +rfc3161 library</a> which seemed like a good fit, but I soon +discovered it only worked for python version 2, and I needed something +that work with python version 3. Luckily I next came across +<a href="https://github.com/trbs/rfc3161ng/">the rfc3161ng library</a>, +a fork of the original rfc3161 library. Not only is it working with +python 3, it have fixed a few of the bugs in the original library, and +it has an active maintainer. I decided to wrap it up and make it +<a href="https://tracker.debian.org/pkg/python-rfc3161ng">available in +Debian</a>, and a few days ago it entered Debian unstable and testing.</p> + +<p>Using the library is fairly straight forward. The only slightly +problematic step is to fetch the required certificates to verify the +timestamp. For some services it is straight forward, while for others +I have not yet figured out how to do it. Here is a small standalone +code example based on of the integration tests in the library code:</p> + +<pre> +#!/usr/bin/python3 + +""" + +Python 3 script demonstrating how to use the rfc3161ng module to +get trusted timestamps. + +The license of this code is the same as the license of the rfc3161ng +library, ie MIT/BSD. + +""" + +import os +import pyasn1.codec.der +import rfc3161ng +import subprocess +import tempfile +import urllib.request + +def store(f, data): + f.write(data) + f.flush() + f.seek(0) + +def fetch(url, f=None): + response = urllib.request.urlopen(url) + data = response.read() + if f: + store(f, data) + return data + +def main(): + with tempfile.NamedTemporaryFile() as cert_f,\ + tempfile.NamedTemporaryFile() as ca_f,\ + tempfile.NamedTemporaryFile() as msg_f,\ + tempfile.NamedTemporaryFile() as tsr_f: + + # First fetch certificates used by service + certificate_data = fetch('https://freetsa.org/files/tsa.crt', cert_f) + ca_data_data = fetch('https://freetsa.org/files/cacert.pem', ca_f) + + # Then timestamp the message + timestamper = \ + rfc3161ng.RemoteTimestamper('http://freetsa.org/tsr', + certificate=certificate_data) + data = b"Python forever!\n" + tsr = timestamper(data=data, return_tsr=True) + + # Finally, convert message and response to something 'openssl ts' can verify + store(msg_f, data) + store(tsr_f, pyasn1.codec.der.encoder.encode(tsr)) + args = ["openssl", "ts", "-verify", + "-data", msg_f.name, + "-in", tsr_f.name, + "-CAfile", ca_f.name, + "-untrusted", cert_f.name] + subprocess.check_call(args) + +if '__main__' == __name__: + main() +</pre> + +<p>The code fetches the required certificates, store them as temporary +files, timestamp a simple message, store the message and timestamp to +disk and ask 'openssl ts' to verify the timestamp. A timestamp is +around 1.5 kiB in size, and should be fairly easy to store for future +use.</p> + +<p>As usual, if you use Bitcoin and want to show your support of my +activities, please send Bitcoin donations to my address +<b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p> + + + Automatic Google Drive sync using grive in Debian http://people.skolelinux.org/pere/blog/Automatic_Google_Drive_sync_using_grive_in_Debian.html @@ -572,153 +678,6 @@ wait "$gstpid" <p>I hope you find the approach useful. I know I do.</p> -<p>As usual, if you use Bitcoin and want to show your support of my -activities, please send Bitcoin donations to my address -<b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p> - - - - - Streaming the Linux desktop to Kodi using VLC and RTSP - http://people.skolelinux.org/pere/blog/Streaming_the_Linux_desktop_to_Kodi_using_VLC_and_RTSP.html - http://people.skolelinux.org/pere/blog/Streaming_the_Linux_desktop_to_Kodi_using_VLC_and_RTSP.html - Thu, 12 Jul 2018 02:00:00 +0200 - <p>PS: See -<ahref="http://people.skolelinux.org/pere/blog/Simple_streaming_the_Linux_desktop_to_Kodi_using_GStreamer_and_RTP.html">the -followup post</a> for a even better approach.</p> - -<p>A while back, I was asked by a friend how to stream the desktop to -my projector connected to Kodi. I sadly had to admit that I had no -idea, as it was a task I never had tried. Since then, I have been -looking for a way to do so, preferable without much extra software to -install on either side. Today I found a way that seem to kind of -work. Not great, but it is a start.</p> - -<p>I had a look at several approaches, for example -<a href="https://github.com/mfoetsch/dlna_live_streaming">using uPnP -DLNA as described in 2011</a>, but it required a uPnP server, fuse and -local storage enough to store the stream locally. This is not going -to work well for me, lacking enough free space, and it would -impossible for my friend to get working.</p> - -<p>Next, it occurred to me that perhaps I could use VLC to create a -video stream that Kodi could play. Preferably using -broadcast/multicast, to avoid having to change any setup on the Kodi -side when starting such stream. Unfortunately, the only recipe I -could find using multicast used the rtp protocol, and this protocol -seem to not be supported by Kodi.</p> - -<p>On the other hand, the rtsp protocol is working! Unfortunately I -have to specify the IP address of the streaming machine in both the -sending command and the file on the Kodi server. But it is showing my -desktop, and thus allow us to have a shared look on the big screen at -the programs I work on.</p> - -<p>I did not spend much time investigating codeces. I combined the -rtp and rtsp recipes from -<a href="https://wiki.videolan.org/Documentation:Streaming_HowTo/Command_Line_Examples/">the -VLC Streaming HowTo/Command Line Examples</a>, and was able to get -this working on the desktop/streaming end.</p> - -<blockquote><pre> -vlc screen:// --sout \ - '#transcode{vcodec=mp4v,acodec=mpga,vb=800,ab=128}:rtp{dst=projector.local,port=1234,sdp=rtsp://192.168.11.4:8080/test.sdp}' -</pre></blockquote> - -<p>I ssh-ed into my Kodi box and created a file like this with the -same IP address:</p> - -<blockquote><pre> -echo rtsp://192.168.11.4:8080/test.sdp \ - > /storage/videos/screenstream.m3u -</pre></blockquote> - -<p>Note the 192.168.11.4 IP address is my desktops IP address. As far -as I can tell the IP must be hardcoded for this to work. In other -words, if someone elses machine is going to do the steaming, you have -to update screenstream.m3u on the Kodi machine and adjust the vlc -recipe. To get started, locate the file in Kodi and select the m3u -file while the VLC stream is running. The desktop then show up in my -big screen. :)</p> - -<p>When using the same technique to stream a video file with audio, -the audio quality is really bad. No idea if the problem is package -loss or bad parameters for the transcode. I do not know VLC nor Kodi -enough to tell.</p> - -<p><strong>Update 2018-07-12</strong>: Johannes Schauer send me a few -succestions and reminded me about an important step. The "screen:" -input source is only available once the vlc-plugin-access-extra -package is installed on Debian. Without it, you will see this error -message: "VLC is unable to open the MRL 'screen://'. Check the log -for details." He further found that it is possible to drop some parts -of the VLC command line to reduce the amount of hardcoded information. -It is also useful to consider using cvlc to avoid having the VLC -window in the desktop view. In sum, this give us this command line on -the source end - -<blockquote><pre> -cvlc screen:// --sout \ - '#transcode{vcodec=mp4v,acodec=mpga,vb=800,ab=128}:rtp{sdp=rtsp://:8080/}' -</pre></blockquote> - -<p>and this on the Kodi end<p> - -<blockquote><pre> -echo rtsp://192.168.11.4:8080/ \ - > /storage/videos/screenstream.m3u -</pre></blockquote> - -<p>Still bad image quality, though. But I did discover that streaming -a DVD using dvdsimple:///dev/dvd as the source had excellent video and -audio quality, so I guess the issue is in the input or transcoding -parts, not the rtsp part. I've tried to change the vb and ab -parameters to use more bandwidth, but it did not make a -difference.</p> - -<p>I further received a suggestion from Einar Haraldseid to try using -gstreamer instead of VLC, and this proved to work great! He also -provided me with the trick to get Kodi to use a multicast stream as -its source. By using this monstrous oneliner, I can stream my desktop -with good video quality in reasonable framerate to the 239.255.0.1 -multicast address on port 1234: - -<blockquote><pre> -gst-launch-1.0 ximagesrc use-damage=0 ! video/x-raw,framerate=30/1 ! \ - videoconvert ! queue2 ! \ - x264enc bitrate=8000 speed-preset=superfast tune=zerolatency qp-min=30 \ - key-int-max=15 bframes=2 ! video/x-h264,profile=high ! queue2 ! \ - mpegtsmux alignment=7 name=mux ! rndbuffersize max=1316 min=1316 ! \ - udpsink host=239.255.0.1 port=1234 ttl-mc=1 auto-multicast=1 sync=0 \ - pulsesrc device=$(pactl list | grep -A2 'Source #' | \ - grep 'Name: .*\.monitor$' | cut -d" " -f2|head -1) ! \ - audioconvert ! queue2 ! avenc_aac ! queue2 ! mux. -</pre></blockquote> - -<p>and this on the Kodi end<p> - -<blockquote><pre> -echo udp://@239.255.0.1:1234 \ - > /storage/videos/screenstream.m3u -</pre></blockquote> - -<p>Note the trick to pick a valid pulseaudio source. It might not -pick the one you need. This approach will of course lead to trouble -if more than one source uses the same multicast port and address. -Note the ttl-mc=1 setting, which limit the multicast packages to the -local network. If the value is increased, your screen will be -broadcasted further, one network "hop" for each increase (read up on -multicast to learn more. :)!</p> - -<p>Having cracked how to get Kodi to receive multicast streams, I -could use this VLC command to stream to the same multicast address. -The image quality is way better than the rtsp approach, but gstreamer -seem to be doing a better job.</p> - -<blockquote><pre> -cvlc screen:// --sout '#transcode{vcodec=mp4v,acodec=mpga,vb=800,ab=128}:rtp{mux=ts,dst=239.255.0.1,port=1234,sdp=sap}' -</pre></blockquote> - <p>As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address <b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>