nix-bitcoin/modules/onion-addresses.nix

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# This module enables unprivileged users to read onion addresses.
# By default, onion addresses in /var/lib/tor/onion are only readable by the
# tor user.
# The included service copies onion addresses to /var/lib/onion-addresses/<user>/
# and sets permissions according to option 'access'.
{ config, lib, ... }:
with lib;
let
options.nix-bitcoin.onionAddresses = {
access = mkOption {
type = with types; attrsOf (listOf str);
default = {};
description = mdDoc ''
This option controls who is allowed to access onion addresses.
For example, the following allows user 'myuser' to access bitcoind
and clightning onion addresses:
```nix
{
"myuser" = [ "bitcoind" "clightning" ];
};
```
The onion hostnames can then be read from
{file}`/var/lib/onion-addresses/myuser`.
'';
};
services = mkOption {
type = with types; listOf str;
default = [];
description = mdDoc ''
Services that can access their onion address via file
{file}`/var/lib/onion-addresses/<service>`
The file is readable only by the service user.
'';
};
dataDir = mkOption {
readOnly = true;
default = "/var/lib/onion-addresses";
};
};
cfg = config.nix-bitcoin.onionAddresses;
nbLib = config.nix-bitcoin.lib;
in {
inherit options;
config = mkIf (cfg.access != {} || cfg.services != []) {
systemd.services.onion-addresses = {
wantedBy = [ "tor.service" ];
bindsTo = [ "tor.service" ];
after = [ "tor.service" ];
serviceConfig = nbLib.defaultHardening // {
Type = "oneshot";
RemainAfterExit = true;
StateDirectory = "onion-addresses";
StateDirectoryMode = "771";
PrivateNetwork = "true"; # This service needs no network access
PrivateUsers = "false";
CapabilityBoundingSet = "CAP_CHOWN CAP_FSETID CAP_SETFCAP CAP_DAC_OVERRIDE CAP_DAC_READ_SEARCH CAP_FOWNER CAP_IPC_OWNER";
};
script = ''
waitForFile() {
file=$1
for ((i=0; i<300; i++)); do
if [[ -e $file ]]; then
return;
fi
sleep 0.1
done
echo "Error: File $file did not appear after 30 sec."
exit 1
}
# Wait until tor is up
waitForFile /var/lib/tor/state
cd ${cfg.dataDir}
rm -rf ./*
${concatMapStrings
(user: ''
mkdir -p -m 0700 ${user}
chown ${user} ${user}
${concatMapStrings
(service: ''
onionFile='/var/lib/tor/onion/${service}/hostname'
waitForFile "$onionFile"
cp "$onionFile" '${user}/${service}'
chown '${user}' '${user}/${service}'
'')
cfg.access.${user}
}
'')
(builtins.attrNames cfg.access)
}
${concatMapStrings (service: ''
onionFile=/var/lib/tor/onion/${service}/hostname
waitForFile "$onionFile"
install -D -o ${config.systemd.services.${service}.serviceConfig.User} -m 400 "$onionFile" services/${service}
'') cfg.services}
'';
};
};
}