Resolve Hostnames in macOS Chroot Jail – Unable to Resolve Hostnames Inside macOS Chroot Jail

bashdnsmacosNetworkopen source

I just created a chroot jail with inetutils, coreutils and bash. Most of the things seem to work. I can ping ip addresses and hosts that are inside /etc/hosts, however, I can't ping hosts that are not in /etc/hosts. I copied both resolv.conf and protocols to the chroot jail, but I still cannot ping hostnames. Which file am I supposed to put inside the jail so I can resolve hostnames? I have also read some stuff about scutil, but I want to avoid copying more binaries as much as possible.

$ ping 8.8.8.8 
PING 8.8.8.8 (8.8.8.8): 56 data bytes
64 bytes from 8.8.8.8: icmp_seq=0 ttl=120 time=22.322 ms
64 bytes from 8.8.8.8: icmp_seq=1 ttl=120 time=26.672 ms

$ ping google.com   # Host not in /etc/hosts
ping: unknown host

$ ping example.com  # Host in /etc/hosts
PING example.com (93.184.216.34): 56 data bytes
64 bytes from 93.184.216.34: icmp_seq=0 ttl=50 time=160.226 ms
64 bytes from 93.184.216.34: icmp_seq=1 ttl=50 time=147.602 ms

Best Answer

I was able to get it to work by making sure the /etc/resolver.conf existed in the chroot and then symlinking /var/run/mDNSResponder into the chroot.

$ sudo chroot -u user "/Users/user/Source/macos-mkjail/test_jail" /bin/bash
bash-4.4$ ping www.google.com
PING www.google.com (216.58.194.164): 56 data bytes
64 bytes from 216.58.194.164: icmp_seq=0 ttl=53 time=10326.366 ms
64 bytes from 216.58.194.164: icmp_seq=1 ttl=53 time=44.899 ms
64 bytes from 216.58.194.164: icmp_seq=2 ttl=53 time=39.388 ms
^C--- www.google.com ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max/stddev = 39.388/3470.218/10326.366/4848.030 ms
bash-4.4$exit
$
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