b88878efec
Encrypted image setups can now bake a Tor onion service into the initramfs so the dropbear unlock shell stays reachable behind NAT or a dynamic IP. When the user opts in, configure_encryption installs tor + busybox, drops the mkinitcpio hooks (ordered `netconf tor dropbear encryptssh`), generates the v3 onion keys offline in the image chroot, and prints the stable .onion address. Unlock with `torsocks ssh root@<onion-address>`. The runtime hook syncs the clock via NTP first (RTC-less boards boot at 1970, which Tor's consensus checks reject) and starts the onion service pointing at dropbear on 127.0.0.1:22. Hardening baked in from an adversarial review of the shipped path: - cmdline.txt boot path (RPi4-class firmware boot) now sets the same ip=::::<host>:eth0:dhcp net.ifnames=0 params as the boot.txt path, so the initramfs actually gets a network and the onion can publish. - the initramfs bakes in libnss_dns.so.2 so the NTP hostname resolves. - the hook extracts DHCP DNS with sed instead of sourcing the lease files, which would run attacker-controlled DHCP option strings as root pre-boot. - NTP is attempted unconditionally (bounded), not gated on DHCP-provided DNS. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
38 lines
1.6 KiB
Bash
38 lines
1.6 KiB
Bash
#!/bin/bash
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# mkinitcpio install hook: Tor onion service for remote LUKS unlock.
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# Installed to /etc/initcpio/install/tor by linux-image-manager.
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build() {
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add_binary /usr/bin/tor
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# Full busybox for the ntpd applet: boards without an RTC (e.g. most
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# Raspberry Pis) wake up in 1970, which Tor's consensus checks reject.
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# A different target path keeps mkinitcpio's own busybox untouched.
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add_binary /usr/bin/busybox /usr/local/bin/busybox
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# glibc resolves the NTP server hostname via getaddrinfo(), which dlopen()s
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# these NSS modules at runtime — add_binary only follows NEEDED libs, so
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# without them DNS silently fails, ntpd never syncs, and the clock stays
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# at 1970. glibc's built-in default (no nsswitch.conf) is "dns ... files".
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add_binary /usr/lib/libnss_dns.so.2
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add_binary /usr/lib/libnss_files.so.2
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add_file /etc/tor/initramfs-torrc /etc/tor/torrc
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add_file /etc/tor/initramfs-onion/hostname /etc/tor/onion/hostname
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add_file /etc/tor/initramfs-onion/hs_ed25519_public_key /etc/tor/onion/hs_ed25519_public_key
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add_file /etc/tor/initramfs-onion/hs_ed25519_secret_key /etc/tor/onion/hs_ed25519_secret_key
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add_runscript
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}
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help() {
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cat <<HELPEOF
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Starts a Tor onion service in early userspace so the dropbear unlock
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shell stays reachable under the .onion address baked into the image,
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even behind NAT or a dynamic IP.
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Place it between netconf and dropbear:
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HOOKS=(... netconf tor dropbear encryptssh ...)
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Optional kernel parameter:
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tor_ntp=<server> NTP server used to set the clock before Tor starts
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(default: pool.ntp.org)
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HELPEOF
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}
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