nixos/taskserver: Add a nixos-taskdctl command

It's a helper for NixOS systems to make it easier to handle CA
certificate signing, similar to what taskd provides but comes preseeded
with the values from the system configuration.

The tool is very limited at the moment and only allows to *add*
organisations, users and groups. Deletion and suspension however is much
simpler to implement, because we don't need to handle certificate
signing.

Another limitation is that we don't take into account whether
certificates and keys are already set in the system configuration and if
they're set it will fail spectacularly.

For passing the commands to the taskd command, we're using a small C
program which does setuid() and setgid() to the Taskserver user and
group, because runuser(1) needs PAM (quite pointless if you're already
root) and su(1) doesn't allow for setting the group and setgid()s to the
default group of the user, so it even doesn't work in conjunction with
sg(1).

In summary, we now have a shiny nixos-taskdctl command, which lets us do
things like:

nixos-taskdctl add-org NixOS
nixos-taskdctl add-user NixOS alice
nixos-taskdctl export-user NixOS alice

The last command writes a series of shell commands to stdout, which then
can be imported on the client by piping it into a shell as well as doing
it for example via SSH:

ssh root@server nixos-taskdctl export-user NixOS alice | sh

Of course, in terms of security we need to improve this even further so
that we generate the private key on the client and just send a CSR to
the server so that we don't need to push any secrets over the wire.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This commit is contained in:
aszlig 2016-04-05 17:31:58 +02:00
parent 5146f76095
commit 227229653a
No known key found for this signature in database
GPG key ID: D0EBD0EC8C2DC961

View file

@ -59,6 +59,43 @@ let
''}
'';
genClientKey = ''
umask 0077
if tmpdir="$(${pkgs.coreutils}/bin/mktemp -d)"; then
trap "rm -rf '$tmpdir'" EXIT
${pkgs.gnutls}/bin/certtool -p --bits 2048 --outfile "$tmpdir/key"
cat > "$tmpdir/template" <<-\ \ EOF
organization = $organisation
cn = ${cfg.server.fqdn}
tls_www_client
encryption_key
signing_key
EOF
${pkgs.gnutls}/bin/certtool -c \
--load-privkey "$tmpdir/key" \
--load-ca-privkey "${cfg.dataDir}/keys/ca.key" \
--load-ca-certificate "${cfg.dataDir}/keys/ca.cert" \
--template "$tmpdir/template" \
--outfile "$tmpdir/cert"
mkdir -m 0700 -p "${cfg.dataDir}/keys/user/$organisation/$user"
chown root:root "${cfg.dataDir}/keys/user/$organisation/$user"
cat "$tmpdir/key" \
> "${cfg.dataDir}/keys/user/$organisation/$user/private.key"
cat "$tmpdir/cert" \
> "${cfg.dataDir}/keys/user/$organisation/$user/public.cert"
rm -rf "$tmpdir"
trap - EXIT
else
echo "Unable to create temporary directory for client" \
"certificate creation." >&2
exit 1
fi
'';
orgOptions = { name, ... }: {
options.users = mkOption {
type = types.uniq (types.listOf types.str);
@ -79,6 +116,293 @@ let
};
};
mkShellStr = val: "'${replaceStrings ["'"] ["'\\''"] val}'";
mkShellName = replaceStrings ["-"] ["_"];
mkSubCommand = name: { args, description, script }: let
mkArg = pos: arg: "local ${arg}=\"\$${toString pos}\"";
mkDesc = line: "echo ${mkShellStr " ${line}"} >&2";
usagePosArgs = concatMapStringsSep " " (a: "<${a}>") args;
in ''
subcmd_${mkShellName name}() {
${concatImapStringsSep "\n " mkArg args}
${script}
}
usage_${mkShellName name}() {
echo " nixos-taskdctl ${name} ${usagePosArgs}" >&2
${concatMapStringsSep "\n " mkDesc description}
}
'';
mkCStr = val: "\"${escape ["\\" "\""] val}\"";
taskdUser = let
runUser = pkgs.writeText "runuser.c" ''
#include <sys/types.h>
#include <pwd.h>
#include <grp.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
int main(int argc, char **argv) {
struct passwd *userinfo;
struct group *groupinfo;
errno = 0;
if ((userinfo = getpwnam(${mkCStr cfg.user})) == NULL) {
if (errno == 0)
fputs(${mkCStr "User name `${cfg.user}' not found."}, stderr);
else
perror("getpwnam");
return EXIT_FAILURE;
}
errno = 0;
if ((groupinfo = getgrnam(${mkCStr cfg.group})) == NULL) {
if (errno == 0)
fputs(${mkCStr "Group name `${cfg.group}' not found."}, stderr);
else
perror("getgrnam");
return EXIT_FAILURE;
}
if (setgid(groupinfo->gr_gid) == -1) {
perror("setgid");
return EXIT_FAILURE;
}
if (setuid(userinfo->pw_uid) == -1) {
perror("setgid");
return EXIT_FAILURE;
}
argv[0] = "taskd";
if (execv(${mkCStr taskd}, argv) == -1) {
perror("execv");
return EXIT_FAILURE;
}
/* never reached */
return EXIT_SUCCESS;
}
'';
in pkgs.runCommand "taskd-user" {} ''
cc -Wall -std=c11 "${runUser}" -o "$out"
'';
subcommands = {
list-users = {
args = [ "organisation" ];
description = [
"List all users belonging to the specified organisation."
];
script = ''
legend "The following users exist for $organisation:"
${pkgs.findutils}/bin/find \
"${cfg.dataDir}/orgs/$organisation/users" \
-mindepth 2 -maxdepth 2 -name config \
-exec ${pkgs.gnused}/bin/sed -ne 's/^user *= *//p' {} +
'';
};
list-orgs = {
args = [];
description = [
"List available organisations"
];
script = ''
legend "The following organisations exist:"
${pkgs.findutils}/bin/find \
"${cfg.dataDir}/orgs" -mindepth 1 -maxdepth 1 \
-type d
'';
};
get-uuid = {
args = [ "organisation" "user" ];
description = [
"Get the UUID of the specified user belonging to the specified"
"organisation."
];
script = ''
for uuid in "${cfg.dataDir}/orgs/$organisation/users"/*; do
usr="$(${pkgs.gnused}/bin/sed -ne 's/^user *= *//p' "$uuid/config")"
if [ "$usr" = "$user" ]; then
legend "User $user has the following UUID:"
echo "$(${pkgs.coreutils}/bin/basename "$uuid")"
exit 0
fi
done
echo "No UUID found for user $user." >&2
exit 1
'';
};
export-user = {
args = [ "organisation" "user" ];
description = [
"Export user of the specified organisation as a series of shell"
"commands that can be used on the client side to easily import"
"the certificates."
""
"Note that the private key will be exported as well, so use this"
"with care!"
];
script = ''
if ! subcmd_quiet list-users "$organisation" | grep -qxF "$user"; then
exists "User $user doesn't exist in organisation $organisation."
fi
uuid="$(subcmd_quiet get-uuid "$organisation" "$user")" || exit 1
cat <<COMMANDS
taskdatadir="\''${TASKDATA:-\$HOME/.task}"
umask 0077
mkdir -p "\$taskdatadir/keys"
cat > "\$taskdatadir/keys/public.cert" <<EOF
$(cat "${cfg.dataDir}/keys/user/$organisation/$user/public.cert")
EOF
cat > "\$taskdatadir/keys/private.key" <<EOF
$(${pkgs.gnused}/bin/sed -ne '/^---* *BEGIN /,/^---* *END /p' \
"${cfg.dataDir}/keys/user/$organisation/$user/private.key")
EOF
cat > "\$taskdatadir/keys/ca.cert" <<EOF
$(cat "${cfg.dataDir}/keys/ca.cert")
EOF
task config taskd.certificate -- "\$taskdatadir/keys/public.cert"
task config taskd.key -- "\$taskdatadir/keys/private.key"
task config taskd.ca -- "\$taskdatadir/keys/ca.cert"
task config taskd.credentials -- "$organisation/$user/$uuid"
COMMANDS
'';
};
add-org = {
args = [ "name" ];
description = [
"Create an organisation with the specified name."
];
script = ''
if [ -e "orgs/$name" ]; then
exists "Organisation with name $name already exists."
fi
${taskdUser} add org "$name"
'';
};
add-user = {
args = [ "organisation" "user" ];
description = [
"Create a user for the given organisation and print the UUID along"
"with the client certificate and key."
];
script = ''
if subcmd list-users "$organisation" | grep -qxF "$user"; then
exists "User $user already exists in organisation $organisation."
fi
${taskdUser} add user "$organisation" "$user"
${genClientKey}
'';
};
add-group = {
args = [ "organisation" "group" ];
description = [
"Create a group for the given organisation."
];
script = ''
if [ -e "orgs/$organisation/groups/$group" ]; then
exists "Group $group already exists in organisation $organisation."
fi
${taskdUser} add group "$organisation" "$group"
'';
};
};
mkCase = name: { args, ... }: let
mkPosArg = pos: const "\"\$${toString (pos + 1)}\"";
cmdArgs = concatImapStringsSep " " mkPosArg args;
in ''
${name})
if [ $# -ne ${toString ((length args) + 1)} ]; then
echo "Wrong number of arguments to ${name}." >&2
echo >&2
usage_${mkShellName name}
exit 1
fi
subcmd "${name}" ${cmdArgs};;
'';
nixos-taskdctl = pkgs.writeScriptBin "nixos-taskdctl" ''
#!${pkgs.stdenv.shell}
export TASKDDATA=${mkShellStr cfg.dataDir}
quiet=0
# Deliberately undocumented, because we don't want people to use this as
# it's only used in and specific to the preStart script of the Taskserver
# service.
if [ "$1" = "--service-helper" ]; then
quiet=1
exists() {
exit 0
}
shift
else
exists() {
echo "$@" >&2
exit 1
}
fi
legend() {
if [ $quiet -eq 0 ]; then
echo "$@" >&2
fi
}
subcmd() {
local cmdname="''${1//-/_}"
shift
"subcmd_$cmdname" "$@"
}
subcmd_quiet() {
local prev_quiet=$quiet
quiet=1
subcmd "$@"
local ret=$?
quiet=$prev_quiet
return $ret
}
${concatStrings (mapAttrsToList mkSubCommand subcommands)}
case "$1" in
${concatStrings (mapAttrsToList mkCase subcommands)}
*) echo "Usage: nixos-taskdctl <subcommand> [<args>]" >&2
echo >&2
echo "A tool to manage taskserver users on NixOS" >&2
echo >&2
echo "The following subcommands are available:" >&2
${concatMapStringsSep "\n " (c: "usage_${mkShellName c}")
(attrNames subcommands)}
exit 1
esac
'';
ctlcmd = "${nixos-taskdctl}/bin/nixos-taskdctl --service-helper";
in {
options = {
@ -294,7 +618,7 @@ in {
config = mkIf cfg.enable {
environment.systemPackages = [ pkgs.taskserver ];
environment.systemPackages = [ pkgs.taskserver nixos-taskdctl ];
users.users = optional (cfg.user == "taskd") {
name = "taskd";