• Thank you for your quick reply !

    Yes, my davdroid cannot use stronger than AES128-GCM-SHA256 cipher: - User [24/Jul/2018:20:35:01 +0200] TLSv1.2/AES128-GCM-SHA256 "PROPFIND /remote.php/dav/calendars/User /Calendar/ HTTP/2.0" 207 1469 "-" "DAVdroid/1.11.5-ose (2018/07/01; dav4android; okhttp/3.10.0) Android/7.0"

    I’m using:
    Samsung J6
    Asus Zenfone 2

    With same server, with same nextcloud instance, I’ve no cipher troubles with nexcloud app ( or others apps in general ) : - User [26/Jul/2018:10:38:41 +0200] TLSv1.2/DHE-RSA-AES256-GCM-SHA384 "PROPFIND /remote.php/webdav/file.ext HTTP/1.1" 207 835 "-" "Mozilla/5.0 (Android) ownCloud-android/3.2.1"

    Here my nginx’s configuration, nothing of special, just ugly ciphers at end of ssl_ciphers 😕

    ssl_protocols TLSv1.2;
    ssl_prefer_server_ciphers on;

    I Hope to be able to remove AES128 ciphers to keep strong crypto configuration

    Maybe I need to do something on my davdroid ? Do you have EC with your davdroid ?

    Thank you !

  • developer

    @jujubickoille On Android 7, DAVdroid does not change the available ciphers. It just uses what’s available by Android.

  • I dunno what Davdroid change or don’t but, with davdroid, I cannot have strongger than a poor AES128. cf my nginx configuration and my logs.

    It’s same with the smartphone of my wife and I’ve no problem with other apps ( Nextcloud app, Chrome, Samsung webbrowser… ) with these phones or with others devices ( when I access to my calendar with my computer using nextcloud Calendar app ).

    So, for me, the problem can be only from davdroid because only davdroid use this cipher ( and if I remove it from my nginx’s conf, I got SSL error when I sync my davdroid ).

    How can I give you some constructive informations ? A debug file with and without AES enabled in Nginx can be interresting for you ?

    Thank you !

  • developer

    @jujubickoille Can you provide a test account which works with other Android 7 apps, but doesn’t work with DAVdroid?

  • Hi all,

    I can confirm I have the same issue using DavDroid on Nextcloud last version hosted by Nginx. If I keep this week AES128 cipher, DavDroid can synchronise properly.

    But if I remove it and keep strong encryption, DavDroid will flood my phone with SSL handshake failure notification.

    I’m using a Galaxy S6 with Android7.

    I have no difficulties with others apps with or without AES128.

    I will post my nginx SSL configuration and some screenshot of DavDroid error on my phone later.

  • developer

    @ap0p0 Screenshots won’t be of any use. Even debug info and logs probably won’t be helpful, because they will just say that there are incompatible ciphers.

    Can you provide a test account that works with the NC app on Android 7, but does not work with DAVdroid on Android 7?

  • I prefer to not have my nextcloud unsynced with davdroid clients.

    But if you can make you own nginx web server with SSL configuration like below, you should reproduce the issue:
    ssl on;
    ssl_protocols TLSv1.2;
    ssl_prefer_server_ciphers on;
    ssl_dhparam xxxxxxxxxxxxx;
    ssl_ecdh_curve secp384r1;
    add_header Strict-Transport-Security “max-age=15768000; includeSubDomains; preload;”;

    ssl_certificate_key xxxxx;
    ssl_certificate xxxxxx;
    ssl_trusted_certificate xxxxxx;

    ssl_session_cache shared:SSL:50m;
    ssl_session_timeout 1d;
    ssl_session_tickets off;

    ssl_stapling on;
    ssl_stapling_verify on;
    resolver_timeout 3s;

  • developer

  • Thank you for your quick answer. I added this, removed AES128 cipher, restarted nginx and I did a caldav/cardav sync. No SSL failure on my phone so I can confirm it’s OK with strong crypto!!

    Thanks! 🙂

  • @rfc2822 I’ve add the prime256v1 curve in my nginx, remove weak cipher and it work too !

    Thank you very much, now I use TLSv1.2/ECDHE-RSA-AES256-GCM-SHA384 So it’s really great =))

    I didn’t see there topics, I’m sorry but I think it will be helpfull !

    many thanks rfc2822 !

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