143 lines
5.6 KiB
Nix
143 lines
5.6 KiB
Nix
# The root-side copy of the cache facts the host's nix daemon and hive-priv
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# use: the key a downloaded closure must be signed by and the netrc the pull
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# token goes out in. The script runs as root on the hive host under the hive's
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# own store identity and writes:
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#
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# - the key into `dir`, which only root can read;
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# - the netrc at `netrcFile`, root 0600: the pull token's entry for `host`
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# followed by the entries of the host's own netrc (`hostNetrc`) for other
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# machines. `netrc-file` is one path, so a fragment that names this file must
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# carry what the host already keeps there;
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# - a nix.conf fragment at `confFile` that the host's nix.conf includes, with
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# `extra-substituters` (the cache's address), `extra-trusted-public-keys` and
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# `netrc-file` (that merged netrc), so the daemon
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# substitutes from the cache and its other substituters. It holds no secret.
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#
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# Nothing is read from a file hive-c0re (unprivileged) writes: the key and the
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# token come from the store.
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#
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# A store that holds no facts yet, or cannot be reached, leaves what is in
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# `dir`, `netrcFile` and `confFile` as they are. Nothing here removes a file.
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#
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# Pure function — NOT a NixOS module. Call it from a unit's `script`, with
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# `bao`, `coreutils`, `gnugrep` and `systemd` on its `path` and the `BAO_*`
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# client environment set:
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#
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# script = import ./lib/attic-root-facts.nix { inherit lib; } {
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# hive = "alpha"; host = "attic.example.org"; dir = "/run/hyperhive-priv/attic";
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# url = "https://attic.example.org/swarm"; confFile = "/run/hyperhive-nix/cache.conf";
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# netrcFile = "/run/hyperhive-nix/netrc"; hostNetrc = "/etc/nix/netrc";
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# };
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{ lib }:
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{
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# The hive's name in the store: facts are read from
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# `secret/swarm/hives/<hive>/attic/`.
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hive,
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# The cache server's host name, which the netrc line names.
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host,
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# Where the key goes.
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dir,
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# The cache's address as the daemon lists it in `extra-substituters`.
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url,
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# Where the nix.conf fragment goes; its directory is root's and readable.
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confFile,
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# Where the merged netrc goes, and the netrc the host uses without this
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# module, which is merged in and never written.
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netrcFile,
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hostNetrc,
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}:
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''
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set -euo pipefail
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${import ./store-seeded-secret.nix { }}
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${import ./atomic-write-secret.nix { }}
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${import ./refresh-consumer.nix { }}
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dir=${lib.escapeShellArg dir}
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conf=${lib.escapeShellArg confFile}
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netrc_file=${lib.escapeShellArg netrcFile}
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host_netrc=${lib.escapeShellArg hostNetrc}
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install -d -m 0700 "$dir"
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install -d -m 0755 "$(dirname -- "$conf")" "$(dirname -- "$netrc_file")"
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store_init
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store_login
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if [ "$STORE_UP" != 1 ]; then
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echo "could not read the cache facts; $dir stays as it is." >&2
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exit 1
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fi
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# <leaf> <variable>. Sets the variable to the leaf's value. A leaf the store
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# does not hold sets `missing`; any other failure ends the run.
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missing=0
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fetch() {
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local value
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if value="$(store_bao kv get -field=value ${lib.escapeShellArg "secret/swarm/hives/${hive}/attic"}/"$1" 2>"$STORE_ERR")"; then
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printf -v "$2" '%s' "$value"
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elif grep -qi 'no value found' "$STORE_ERR"; then
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missing=1
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else
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cat "$STORE_ERR" >&2
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echo "could not read the cache fact $1; $dir stays as it is." >&2
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exit 1
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fi
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}
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key=""
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token=""
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fetch public-key key
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fetch pull-token token
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if [ "$missing" = 1 ]; then
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echo "the swarm has not given this hive its cache facts yet; $dir stays as it is."
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exit 0
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fi
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# One token each: both land in a file nix and hive-priv parse by whitespace.
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if [[ ! "$key" =~ ^[^[:space:]:]+:[^[:space:]]+$ ]] || [[ ! "$token" =~ ^[^[:space:]]+$ ]]; then
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echo "the stored cache facts are not a <name>:<key> and a single token; $dir stays as it is." >&2
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exit 1
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fi
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# Written only when the value changed, so the files keep their mtime between
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# runs. The owner is the running user, root, and the mode is 0600.
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if secret_differs "$dir/public-key" "$key"; then
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atomic_write_secret 0600 "" "$dir/public-key" "$key"
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fi
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# The host's netrc without its lines for this cache's host: an entry runs from
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# a `machine` or `default` line to the next one. A missing file is no entries.
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# Our entry goes first, which is the one curl takes when an entry the filter
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# does not recognise names the cache's host too.
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other_netrc_entries() {
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local line skip=0 tok kept=""
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[ -f "$host_netrc" ] || return 0
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while IFS= read -r line || [ -n "$line" ]; do
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read -ra tok <<<"$line"
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case "''${tok[0]-}" in
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machine) if [ "''${tok[1]-}" = ${lib.escapeShellArg host} ]; then skip=1; else skip=0; fi ;;
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default) skip=0 ;;
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esac
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[ "$skip" = 1 ] || kept+="$line"$'\n'
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done <"$host_netrc"
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printf '%s' "$kept"
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}
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netrc="machine ${host} password $token"
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others="$(other_netrc_entries)"
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if [ -n "$others" ]; then netrc="$netrc"$'\n'"$others"; fi
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# The mode too: an earlier deploy left this path 0640 for a group.
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if secret_differs "$netrc_file" "$netrc" || [ "$(stat -c %a "$netrc_file")" != 600 ]; then
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atomic_write_secret 0600 "" "$netrc_file" "$netrc"
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fi
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# Last, so a daemon that reads the fragment finds the netrc in place. The
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# mtime moves only with the content. Lix re-reads nix.conf for every
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# connection, CppNix only at start, so a CppNix daemon that started before
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# this write is restarted.
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printf -v fragment '%s\n%s\n%s' \
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${lib.escapeShellArg "extra-substituters = ${url}"} \
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"extra-trusted-public-keys = $key" \
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"netrc-file = $netrc_file"
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if secret_differs "$conf" "$fragment"; then
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atomic_write_secret 0644 "" "$conf" "$fragment"
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fi
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refresh_unit nix-daemon.service "$conf"
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''
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