Privacy Preserving Analytics
Posted on Apr 15, 2019 by
eighthave
F-Droid always avoids tracking users as much as we can. We will never require an account, and we have put a lot of effort into making it hard for even the f-droid.org server to track users. We also recognize that usage data has value. It can be used to help show the level of popularity, and to provide app developers some feedback on what users like.
After years of moving totally away from data, including disabling download counts on f-droid.org, we have started an experiment with tracking usage without tracking users. We are building upon the work of Tor Project and Guardian Project. We have enabled access logging on https://search.f-droid.org and https://mirror.f-droid.org/ for the initial trial. (Note: search on f-droid.org could happen fully client-side using javascript, in that case, those searches will never hit search.f-droid.org and therefore will not be logged).
The one caveat here is that Nginx does not allow custom time formats like Apache does, so the web logs will contain exact date and time of each hit. The time zone is zeroed out. The raw logs will not be published, and they will be sanitized before being fed into any analytics system like Matomo/Piwik. Also, Nginx does not allow custom error log formats, so errors will have complete information. The error logs will therefore not be used in analytics without full sanitation, and are only kept for a short time period.
Our Setup
Our servers run Debian, so this gives commands for that context. First, ensure that Nginx is set up with the “geoip” extension. That enables Nginx to convert IP addresses into country codes, so that country codes are logged instead of IP addresses.
# apt-get install libnginx-mod-http-geoip geoip-database
Then enable the custom logging setup in /etc/nginx/nginx.conf:
geoip_country /usr/share/GeoIP/GeoIP.dat;
log_format privacy '0.0.0.0 - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "-" $geoip_country_code';
access_log /var/log/nginx/access.log privacy;
This then makes the access log data look like:
# tail /var/log/nginx/access.log
0.0.0.0 - - [12/Apr/2019:07:01:37 +0000] "GET /android-free/repository/ HTTP/1.1" 200 949 "-" "-" PL
0.0.0.0 - - [12/Apr/2019:07:02:27 +0000] "GET /robots.txt HTTP/1.1" 200 24 "-" "-" US
0.0.0.0 - - [12/Apr/2019:07:02:27 +0000] "GET /android-free/repository/ HTTP/1.1" 200 949 "-" "-" US
0.0.0.0 - - [12/Apr/2019:07:04:08 +0000] "GET / HTTP/1.1" 200 278 "-" "-" BR
0.0.0.0 - - [12/Apr/2019:07:06:41 +0000] "GET /android-free/repository/ HTTP/1.1" 200 949 "-" "-" US
0.0.0.0 - - [12/Apr/2019:07:11:45 +0000] "GET /android-free/repository/ HTTP/1.1" 200 949 "-" "-" FR
0.0.0.0 - - [12/Apr/2019:07:16:32 +0000] "GET / HTTP/1.1" 200 278 "-" "-" CA
0.0.0.0 - - [12/Apr/2019:07:16:49 +0000] "GET /android-free/repository/ HTTP/1.1" 200 949 "-" "-" GB
0.0.0.0 - - [12/Apr/2019:07:19:42 +0000] "GET / HTTP/1.1" 200 278 "-" "-" VN
0.0.0.0 - - [12/Apr/2019:07:20:20 +0000] "GET /robots.txt HTTP/1.1" 200 24 "-" "-" US
0.0.0.0 - - [12/Apr/2019:07:21:51 +0000] "GET /android-free/repository/ HTTP/1.1" 200 949 "-" "-" US
0.0.0.0 - - [12/Apr/2019:07:26:57 +0000] "GET /android-free/repository/ HTTP/1.1" 200 949 "-" "-" DE
0.0.0.0 - - [12/Apr/2019:07:32:01 +0000] "GET /android-free/repository/ HTTP/1.1" 200 949 "-" "-" SE
0.0.0.0 - - [12/Apr/2019:07:32:23 +0000] "GET /android-free/repository/sys-img/android/sys-img-9.0.0_r33-sdk.xml HTTP/1.1" 200 904 "-" "-" US
0.0.0.0 - - [12/Apr/2019:07:37:04 +0000] "GET /android-free/repository/ HTTP/1.1" 200 949 "-" "-" DE
0.0.0.0 - - [12/Apr/2019:07:38:55 +0000] "\x03\x00\x00/*\xE0\x00\x00\x00\x00\x00Cookie: mstshash=Administr" 400 173 "-" "-" RU
0.0.0.0 - - [12/Apr/2019:07:39:12 +0000] "GET / HTTP/1.1" 200 278 "-" "-" EC
