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nix trusts the swarm's root through its own CA bundle, so root's nix clients reach the cache

This commit is contained in:
atlas 2026-11-08 18:32:37 +01:00
commit 9d62ef44b5

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@ -1,32 +1,32 @@
# The root-side copy of the cache facts the host's nix daemon and hive-priv
# use: the key a downloaded closure must be signed by and the netrc the pull
# token goes out in. The script runs as root on the hive host under the hive's
# own store identity and writes:
# The root-side copy of the cache facts the host's nix daemon and hive-priv use:
# the key a closure must be signed by, the netrc the pull token goes out in and
# the CA bundle that trusts the cache. The script runs as root on the hive host
# under the hive's own store identity and writes:
#
# - the key into `dir`, which only root can read;
# - the netrc at `netrcFile`, root 0600: the pull token's entry for `host`
# followed by the entries of the host's own netrc (`hostNetrc`) for other
# machines. `netrc-file` is one path, so a fragment that names this file must
# carry what the host already keeps there;
# - the netrc at `netrcFile`, root 0600: the pull token's entry for `host` then
# the entries of the host's own netrc (`hostNetrc`), as `netrc-file` is one path;
# - the CA bundle at `caBundleFile`, root 0644: the host's own bundle
# (`baseBundle`) then the swarm's root (`swarmCa`), when the host holds it,
# which the cache's certificate chains to; `ssl-cert-file` is one path too;
# - a nix.conf fragment at `confFile` that the host's nix.conf includes, with
# `extra-substituters` (the cache's address), `extra-trusted-public-keys` and
# `netrc-file` (that merged netrc), so the daemon
# substitutes from the cache and its other substituters. It holds no secret.
# `extra-substituters` (the cache's address), `extra-trusted-public-keys`,
# `netrc-file` and `ssl-cert-file`. It holds no secret.
#
# Nothing is read from a file hive-c0re (unprivileged) writes: the key and the
# token come from the store.
# token come from the store. A store that holds no facts yet, or cannot be
# reached, leaves what is in `dir`, `netrcFile`, `caBundleFile` and `confFile`
# as they are. Nothing here removes a file.
#
# A store that holds no facts yet, or cannot be reached, leaves what is in
# `dir`, `netrcFile` and `confFile` as they are. Nothing here removes a file.
#
# Pure function — NOT a NixOS module. Call it from a unit's `script`, with
# `bao`, `coreutils`, `gnugrep` and `systemd` on its `path` and the `BAO_*`
# client environment set:
# Pure function — NOT a NixOS module. Call it from a unit's `script`, with `bao`,
# `coreutils`, `gnugrep`, `systemd` on its `path` and the `BAO_*` client set:
#
# script = import ./lib/attic-root-facts.nix { inherit lib; } {
# hive = "alpha"; host = "attic.example.org"; dir = "/run/hyperhive-priv/attic";
# url = "https://attic.example.org/swarm"; confFile = "/run/hyperhive-nix/cache.conf";
# netrcFile = "/run/hyperhive-nix/netrc"; hostNetrc = "/etc/nix/netrc";
# caBundleFile = "/run/hyperhive-nix/ca-bundle.crt"; baseBundle = "/etc/ssl/certs/ca-certificates.crt";
# swarmCa = "/var/lib/hive-tls/swarm-services-root.pem";
# };
{ lib }:
{
@ -45,6 +45,15 @@
# module, which is merged in and never written.
netrcFile,
hostNetrc,
# Where the CA bundle goes.
caBundleFile,
# The CA bundle nix uses without this module, copied in and never written:
# `ssl-cert-file` is one path, so a fragment that names the new bundle must
# carry the host's CAs.
baseBundle,
# The swarm's root certificate. The file may be absent: the bundle then holds
# the host's CAs alone until a later run finds it.
swarmCa,
}:
''
set -euo pipefail
@ -56,8 +65,11 @@
conf=${lib.escapeShellArg confFile}
netrc_file=${lib.escapeShellArg netrcFile}
host_netrc=${lib.escapeShellArg hostNetrc}
ca_bundle_file=${lib.escapeShellArg caBundleFile}
base_bundle=${lib.escapeShellArg baseBundle}
swarm_ca=${lib.escapeShellArg swarmCa}
install -d -m 0700 "$dir"
install -d -m 0755 "$(dirname -- "$conf")" "$(dirname -- "$netrc_file")"
install -d -m 0755 "$(dirname -- "$conf")" "$(dirname -- "$netrc_file")" "$(dirname -- "$ca_bundle_file")"
store_init
store_login
@ -128,14 +140,33 @@
atomic_write_secret 0600 "" "$netrc_file" "$netrc"
fi
# Last, so a daemon that reads the fragment finds the netrc in place. The
# mtime moves only with the content. Lix re-reads nix.conf for every
# connection, CppNix only at start, so a CppNix daemon that started before
# this write is restarted.
printf -v fragment '%s\n%s\n%s' \
# The host's CAs, then the swarm's root. Nix reads the file for each
# download, so a root that lands after the fragment reaches the next one
# without a restart. A file without a certificate is not appended: the bundle
# serves every https fetch of every nix client.
if [ ! -r "$base_bundle" ]; then
echo "cannot read the host's CA bundle $base_bundle; $ca_bundle_file stays as it is." >&2
exit 1
fi
bundle="$(< "$base_bundle")"
if [ -s "$swarm_ca" ] && grep -q -- '-----BEGIN CERTIFICATE-----' "$swarm_ca"; then
bundle+=$'\n'"$(< "$swarm_ca")"
else
echo "the swarm's root $swarm_ca is not on this host yet; $ca_bundle_file holds the host's CAs only."
fi
if secret_differs "$ca_bundle_file" "$bundle" || [ "$(stat -c %a "$ca_bundle_file")" != 644 ]; then
atomic_write_secret 0644 "" "$ca_bundle_file" "$bundle"
fi
# Last, so a daemon that reads the fragment finds the netrc and the bundle in
# place. The mtime moves only with the content. Lix re-reads nix.conf for
# every connection, CppNix only at start, so a CppNix daemon that started
# before this write is restarted.
printf -v fragment '%s\n%s\n%s\n%s' \
${lib.escapeShellArg "extra-substituters = ${url}"} \
"extra-trusted-public-keys = $key" \
"netrc-file = $netrc_file"
"netrc-file = $netrc_file" \
"ssl-cert-file = $ca_bundle_file"
if secret_differs "$conf" "$fragment"; then
atomic_write_secret 0644 "" "$conf" "$fragment"
fi