WIP: set up heimdal-openldap-sasl stack

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Oystein Kristoffer Tveit 2024-07-06 13:08:05 +02:00
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# Tracking document for new PVV kerberos auth stack
![Bensinstasjon på heimdal](https://bydelsnytt.no/wp-content/uploads/2022/08/esso_heimdal003.jpg)
<div align="center">
Bensinstasjon på heimdal
</div>
### TODO:
- [ ] setup heimdal
- [x] ensure running with systemd
- [x] compile smbk5pwd (part of openldap)
- [ ] set `modify -a -disallow-all-tix,requires-pre-auth default` declaratively
- [ ] fully initialize PVV.NTNU.NO
- [x] `kadmin -l init PVV.NTNU.NO`
- [x] add oysteikt/admin@PVV.NTNU.NO principal
- [x] add oysteikt@PVV.NTNU.NO principal
- [ ] add krbtgt@PVV.NTNU.NO principal?
- why is this needed, and where is it documented?
- `kadmin check` seems to work under sudo?
- Fix FQDN: https://github.com/NixOS/nixpkgs/issues/94011
https://github.com/NixOS/nixpkgs/issues/261269
- [ ] setup cyrus sasl
- [x] ensure running with systemd
- [x] verify GSSAPI support plugin is installed
- `nix-shell -p cyrus_sasl --command pluginviewer`
- [x] create "host/localhost@PVV.NTNU.NO" and export to keytab
- [x] verify cyrus sasl is able to talk to heimdal
- `sudo testsaslauthd -u oysteikt -p <password>`
- [ ] provide ldap principal to cyrus sasl through keytab
- [ ] setup openldap
- [x] ensure running with systemd
- [ ] verify openldap is able to talk to cyrus sasl
- [ ] create user for oysteikt in openldap
- [ ] authenticate openldap login through sasl
- does this require creating an ldap user?
- [ ] fix smbk5pwd integration
- [x] add smbk5pwd schemas to openldap
- [x] create openldap db for smbk5pwd with overlays
- [ ] test to ensure that user sync is working
- [ ] test as user source (replace passwd)
- [ ] test as PAM auth source
- [ ] test as auth source for 3rd party appliation
- [ ] Set up ldap administration panel
- Doesn't seem like there are many good ones out there. Maybe phpLDAPAdmin?
- [ ] Set up kerberos SRV DNS entry
### Information and URLS
- OpenLDAP SASL: https://www.openldap.org/doc/admin24/sasl.html
- Use a keytab: https://kb.iu.edu/d/aumh
- 2 ways for openldap to auth: https://security.stackexchange.com/questions/65093/how-to-test-ldap-that-authenticates-with-kerberos
- Cyrus guide OpenLDAP + SASL + GSSAPI: https://www.cyrusimap.org/sasl/sasl/faqs/openldap-sasl-gssapi.html
- Configuring GSSAPI and Cyrus SASL: https://web.mit.edu/darwin/src/modules/passwordserver_sasl/cyrus_sasl/doc/gssapi.html
- PVV Kerberos docs: https://wiki.pvv.ntnu.no/wiki/Drift/Kerberos
- OpenLDAP smbk5pwd source: https://git.openldap.org/nivanova/openldap/-/tree/master/contrib/slapd-modules/smbk5pwd
- saslauthd(8): https://linux.die.net/man/8/saslauthd

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./hardware-configuration.nix ./hardware-configuration.nix
../../base.nix ../../base.nix
../../misc/metrics-exporters.nix ../../misc/metrics-exporters.nix
./services/heimdal.nix
./services/openldap.nix
./services/cyrus-sasl.nix
]; ];
# buskerud does not support efi? # buskerud does not support efi?
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boot.loader.grub.enable = true; boot.loader.grub.enable = true;
boot.loader.grub.device = "/dev/sda"; boot.loader.grub.device = "/dev/sda";
# resolved messes up FQDN coming from nscd
services.resolved.enable = false;
networking.hostName = "dagali"; networking.hostName = "dagali";
networking.search = [ "pvv.ntnu.no" "pvv.org" ]; networking.search = [ "pvv.ntnu.no" "pvv.org" ];
networking.nameservers = [ "129.241.0.200" "129.241.0.201" ]; networking.nameservers = [ "129.241.0.200" "129.241.0.201" ];

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{ config, ... }:
let
cfg = config.services.saslauthd;
in
{
# TODO: This is seemingly required for openldap to authenticate
# against kerberos, but I have no idea how to configure it as
# such. Does it need a keytab? There's a binary "testsaslauthd"
# that follows with `pkgs.cyrus_sasl` that might be useful.
services.saslauthd = {
enable = true;
mechanism = "kerberos5";
config = ''
mech_list: gs2-krb5 gssapi
keytab: /etc/krb5.keytab
'';
};
# TODO: maybe the upstream module should consider doing this?
environment.systemPackages = [ cfg.package ];
}

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{ config, pkgs, lib, ... }:
let
realm = "PVV.NTNU.NO";
cfg = config.security.krb5;
in
{
security.krb5 = {
enable = true;
# NOTE: This has a small edit that moves an include header to $dev/include.
# It is required in order to build smbk5pwd, because of some nested includes.
# We should open an issue upstream (heimdal, not nixpkgs), but this patch
# will do for now.
# package = pkgs.callPackage ./package.nix {
# inherit (pkgs.apple_sdk.frameworks)
# CoreFoundation Security SystemConfiguration;
# };
package = pkgs.heimdal.overrideAttrs (prev: {
postInstall = prev.postInstall + ''
cp include/heim_threads.h $dev/include
'';
});
settings = {
# logging.kdc = "CONSOLE";
realms.${realm} = {
admin_server = "dagali.pvv.ntnu.no";
kdc = [ "localhost" ];
};
kadmin.default_keys = lib.concatStringsSep " " [
"aes256-cts-hmac-sha1-96:pw-salt"
"aes128-cts-hmac-sha1-96:pw-salt"
];
libdefaults.default_etypes = lib.concatStringsSep " " [
"aes256-cts-hmac-sha1-96"
"aes128-cts-hmac-sha1-96"
];
libdefaults = {
default_realm = realm;
};
domain_realm = {
"pvv.ntnu.no" = realm;
".pvv.ntnu.no" = realm;
};
logging = {
kdc = "SYSLOG:DEBUG:AUTH";
admin_server = "SYSLOG:DEBUG:AUTH";
default = "SYSLOG:DEBUG:AUTH";
};
};
};
services.kerberos_server = {
enable = true;
settings = {
realms.${realm} = {
dbname = "/var/heimdal/heimdal";
mkey = "/var/heimdal/mkey";
};
# kadmin.default_keys = lib.concatStringsSep " " [
# "aes256-cts-hmac-sha1-96:pw-salt"
# "aes128-cts-hmac-sha1-96:pw-salt"
# ];
# libdefaults.default_etypes = lib.concatStringsSep " " [
# "aes256-cts-hmac-sha1-96"
# "aes128-cts-hmac-sha1-96"
# ];
# password_quality.min_length = 8;
};
};
}

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{ config, pkgs, lib, ... }:
{
services.openldap = let
dn = "dc=kerberos,dc=pvv,dc=ntnu,dc=no";
cfg = config.services.openldap;
heimdal = config.security.krb5.package;
in {
enable = true;
# NOTE: this is a custom build of openldap with support for
# perl and kerberos.
package = pkgs.openldap.overrideAttrs (prev: {
# https://github.com/openldap/openldap/blob/master/configure
configureFlags = prev.configureFlags ++ [
# Connect to slapd via UNIX socket
"--enable-local"
# Cyrus SASL
"--enable-spasswd"
# Reverse hostname lookups
"--enable-rlookups"
# perl
"--enable-perl"
];
buildInputs = prev.buildInputs ++ [
pkgs.perl
# NOTE: do not upstream this, it might not work with
# MIT in the same way
heimdal
];
extraContribModules = prev.extraContribModules ++ [
# https://git.openldap.org/openldap/openldap/-/tree/master/contrib/slapd-modules
"smbk5pwd"
];
});
settings = {
attrs = {
olcLogLevel = [ "stats" "config" "args" ];
# olcAuthzRegexp = ''
# gidNumber=.*\\\+uidNumber=0,cn=peercred,cn=external,cn=auth
# "uid=heimdal,${dn2}"
# '';
# olcSaslSecProps = "minssf=0";
};
children = {
"cn=schema".includes = let
# NOTE: needed for smbk5pwd.so module
schemaToLdif = name: path: pkgs.runCommandNoCC name {
buildInputs = with pkgs; [ schema2ldif ];
} ''
schema2ldif "${path}" > $out
'';
hdb-ldif = schemaToLdif "hdb.ldif" "${heimdal.src}/lib/hdb/hdb.schema";
samba-ldif = schemaToLdif "samba.ldif" "${heimdal.src}/tests/ldap/samba.schema";
in [
"${cfg.package}/etc/schema/core.ldif"
"${cfg.package}/etc/schema/cosine.ldif"
"${cfg.package}/etc/schema/nis.ldif"
"${cfg.package}/etc/schema/inetorgperson.ldif"
"${hdb-ldif}"
"${samba-ldif}"
];
# NOTE: installation of smbk5pwd.so module
# https://git.openldap.org/openldap/openldap/-/tree/master/contrib/slapd-modules/smbk5pwd
"cn=module{0}".attrs = {
objectClass = [ "olcModuleList" ];
olcModuleLoad = [ "${cfg.package}/lib/modules/smbk5pwd.so" ];
};
# NOTE: activation of smbk5pwd.so module for {1}mdb
"olcOverlay={0}smbk5pwd,olcDatabase={1}mdb".attrs = {
objectClass = [ "olcOverlayConfig" "olcSmbK5PwdConfig" ];
olcOverlay = "{0}smbk5pwd";
olcSmbK5PwdEnable = [ "krb5" "samba" ];
olcSmbK5PwdMustChange = toString (60 * 60 * 24 * 30);
};
"olcDatabase={1}mdb".attrs = {
objectClass = [ "olcDatabaseConfig" "olcMdbConfig" ];
olcDatabase = "{1}mdb";
olcSuffix = dn;
# TODO: PW is supposed to be a secret, but it's probably fine for testing
olcRootDN = "cn=admin,${dn}";
# TODO: replace with proper secret
olcRootPW.path = pkgs.writeText "olcRootPW" "pass";
olcDbDirectory = "/var/lib/openldap/test-smbk5pwd-db";
olcDbIndex = "objectClass eq";
olcAccess = [
''{0}to attrs=userPassword,shadowLastChange
by dn.exact=cn=admin,${dn} write
by self write
by anonymous auth
by * none''
''{1}to dn.base=""
by * read''
/* allow read on anything else */
# ''{2}to *
# by cn=admin,${dn} write by dn.exact=gidNumber=0+uidNumber=0+cn=peercred,cn=external write
# by * read''
];
};
};
};
};
}