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Joe edited this page Jan 28, 2021 · 23 revisions

Setup

Use the following steps to configure a domain for DNS C2 (and DNS Canaries), you can use any DNS provider you wish as long as you setup the records correctly. I recommend setting a TTL of ~5 minutes for each record.

  1. Create an A record for your example.com pointing at your Sliver server (or redirector) IP address.
  2. Create an A record for an ns1 subdomain (i.e. ns1.example.com) that points to your Sliver server (or redirector) IP address.
  3. Create an NS record with an arbitrary subdomain, for example 1 (i.e. 1.example.com) which is managed by ns1.example.com.
  4. You can now use 1.example.com as your DNS C2 domain e.g. generate --dns 1.example.com. (always use the FQDN when issuing DNS commands).

IMPORTANT: Always use the FQDN when issuing DNS commands in the Sliver console (e.g., 1.example.com. note the trailing .). DNS is a finicky protocol!

The final configuration should look like for the domain lil-peep.rip: DNS Configuration

IMPORTANT: Remember to disable Cloudflare's "cloud" when configuring these records, and to adjust the TTLs.

DNS Canaries

DNS Canaries are unique per-binary domains that are optionally inserted during the string obfuscation process. These domains are not actually used by the implant code and are deliberately not obfuscated so that they show up if someone runs strings on the implant. If these domains are ever resolved (and you have a dns listener running) you'll get an alert telling which specific file was discovered by the blue team.

Example generate command with canaries, make sure to use the FQDN:

sliver > generate --http foobar.com --canary 1.example.com.

Make sure you have a DNS listener running, and to use the FQDN:

sliver > dns --domains 1.example.com.

[*] Starting DNS listener with parent domain(s) [1.example.com.] ...
[*] Successfully started job #1

You can view previously generated canaries with the canaries command.

Ubuntu

NOTE: On recent versions of Ubuntu, you may need to disable systemd-resolved as this binds to your local UDP:53 and fucks up everything about how DNS is supposed to work. To use a sane DNS configuration run the following commands as root because resolved probably broke sudo too:

systemctl disable systemd-resolved.service
systemctl stop systemd-resolved
rm -f /etc/resolv.conf
vim /etc/resolv.conf

Add a normal resolv.conf:

nameserver 1.1.1.1
nameserver 8.8.8.8

Under the Hood

TODO :)