Join the AMA (Ask Me Anything) with the Firefox leadership team to celebrate Firefox 20th anniversary and discuss Firefox’s future on Mozilla Connect. Mark your calendar on Thursday, November 14, 18:00 - 20:00 UTC!

Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

This thread was archived. Please ask a new question if you need help.

DNS over https not working properly

  • 4 replies
  • 1 has this problem
  • 1 view
  • Last reply by Andrew P

Andrew P
Andrew P
more options

My UK ISP has a 'Site Safe' feature that is set at the ISP end, to block malicious websites. When I

enable this setting, and specifically enable DoH under Options, a DNS leak test shows that my ISP is my DNS provider. disable this setting, and specifically enable DoH under Options, a DNS leak test shows that Cloudflare is my DNS provider.

Shouldn't DoH work all the time, if I specifically enable DoH under Options? Otherwise bad actor sites could do the same thing as my ISP, and I would think I'm protected, but in reality, I'm not and exposing my DNS traffic?

My UK ISP has a 'Site Safe' feature that is set at the ISP end, to block malicious websites. When I enable this setting, and specifically enable DoH under Options, a DNS leak test shows that my ISP is my DNS provider. disable this setting, and specifically enable DoH under Options, a DNS leak test shows that Cloudflare is my DNS provider. Shouldn't DoH work all the time, if I specifically enable DoH under Options? Otherwise bad actor sites could do the same thing as my ISP, and I would think I'm protected, but in reality, I'm not and exposing my DNS traffic?

All Replies (4)

Dilan Ranawaka
Dilan Ranawaka
more options

You can enable or disable DoH in your Firefox connection settings: 

  *Click the menu button Fx57Menu and select Options.
  *In the General panel, scroll down to Network Settings and click the Settings… button.
  *In the dialog box that opens, scroll down to Enable DNS over HTTPS.

       On: Select the Enable DNS over HTTPS checkbox. Select a provider or set up a custom provider.
       Off: Deselect the Enable DNS over HTTPS checkbox. 

  *Click OK to save your changes and close the window.
Andrew P
Andrew P Question owner
more options

This is not what I'm asking. Feel free to re-read the original.

TyDraniu
TyDraniu
  • Top 10 Contributor
more options

Andrew P said

My UK ISP has a 'Site Safe' feature that is set at the ISP end, to block malicious websites. Shouldn't DoH work all the time, if I specifically enable DoH under Options? Otherwise bad actor sites could do the same thing as my ISP, and I would think I'm protected, but in reality, I'm not and exposing my DNS traffic?

In my private opinion, you're right. But DoH is breaking this 'Site Safe' feature, all UK ISPs have named Mozilla the Villain Of The Year (you know, our children are no longer safe), so Moz has decided to change the way it works.

For domains that are excluded from TRR or when parental control is enabled, we fallback to NativeLookup. This happens even in MODE_TRRONLY. By default localhost and local are excluded (so we cover *.local hosts).

To change it back, go to about:config and set network.dns.skipTRR-when-parental-control-enabled = false. See also the network.trr.excluded-domains pref.

See:

Andrew P
Andrew P Question owner
more options

Thanks for your reply. Very helpful.

I did try to set the value to 'false' and it didn't work (DNS still shows resolver is set to ISP's resolver) but I'm guessing this setting only refers to Mozilla's implementation of parental controls (about:safe)?

I didn't change any other value and for ref: network.trr.mode showed as 2.

As such, it would be useful to have some sort to indicator on the UI, so that if DoH is set by the user, a graphic shows whether a users DNS traffic is being directed properly.