Samba 4.21 Features added/changed
Samba 4.20 is Current Stable Release.
Samba 4.21.0
- Release Notes for 4.21.0
- September 02, 2024
Release Announcements
This is the first stable release of the Samba 4.21 release series. Please read the release notes carefully before upgrading.
UPGRADING
Hardening of "valid users", "invalid users", "read list" and "write list"
In previous versions of Samba, if a user or group name in either of the mentioned options could not be resolved to a valid SID, the user (or group) would be skipped without any notification. This could result in unexpected and insecure behaviour. Starting with this version of Samba, if any user or group name in any of the options cannot be resolved due to a communication error with a domain controller, Samba will log an error and the tree connect will fail. Non existing users (or groups) are ignored.
LDAP TLS/SASL channel binding support
The ldap server supports SASL binds with kerberos or NTLMSSP over TLS connections now (either ldaps or starttls).
Setups where 'ldap server require strong auth = allow_sasl_over_tls' was required before, can now most likely move to the default of 'ldap server require strong auth = yes'.
If SASL binds without correct tls channel bindings are required 'ldap server require strong auth = allow_sasl_without_tls_channel_bindings' should be used now, as 'allow_sasl_over_tls' will generate a warning in every start of 'samba', as well as '[samba-tool ]testparm'.
This is similar to LdapEnforceChannelBinding under HKLM\SYSTEM\CurrentControlSet\Services\NTDS\Parameters on Windows.
All client tools using ldaps also include the correct channel bindings now.
NEW FEATURES/CHANGES
LDB no longer a standalone tarball
LDB, Samba's LDAP-like local database and the power behind the Samba AD DC, is no longer available to build as a distinct tarball, but is instead provided as an optional public library.
If you need ldb as a public library, say to build sssd, then use ./configure --private-libraries='!ldb'
This re-integration allows LDB tests to use the Samba's full selftest system, including our knownfail infrastructure, and decreases the work required during security releases as a coordinated release of the ldb tarball is not also required.
This approach has been demonstrated already in Debian, which is already building Samba and LDB is this way.
As part of this work, the pyldb-util public library, not known to be used by any other software, is made private to Samba.
LDB Module API Python bindings removed
The LDB Modules API, which we do not promise a stable ABI or API for, was wrapped in python in early LDB development. However that wrapping never took into account later changes, and so has not worked for a number of years. Samba 4.21 and LDB 2.10 removes this unused and broken feature.
Changes in LDB handling of Unicode
Developers using LDB up to version 2.9 could call ldb_set_utf8_fns() to determine how LDB handled casefolding. This is used internally by string comparison functions. In LDB 2.10 this function is deprecated, and ldb_set_utf8_functions() is preferred. The new function allows a direct comparison function to be set as well as a casefold function.
This improves performance and allows for more robust handling of degenerate cases. The function should be called just after ldb_init(), with the following arguments:
ldb_set_utf8_functions(ldb, /* the struct ldb_ctx LDB object */
context_variable /* possibly NULL */
casefold_function,
case_insensitive_comparison_function);
The default behaviour of LDB remains to perform ASCII casefolding only, as if in the "C" locale. Recent versions have become increasingly consistent in this.
Some Samba public libraries made private by default
The following Samba C libraries are currently made public due to their use by OpenChange or for historical reasons that are no longer clear.
dcerpc-samr, samba-policy, tevent-util, dcerpc, samba-hostconfig, samba-credentials, dcerpc_server, samdb
The libraries used by the OpenChange client now private, but can be made public (like ldb above) with:
./configure --private-libraries='!dcerpc,!samba-hostconfig,!samba-credentials,!ldb'
The C libraries without any known user or used only for the OpenChange server (a dead project) may be made private entirely in a future Samba version.
If you use a Samba library in this list, please be in touch with the samba-technical mailing list.
Using ldaps from 'winbindd' and 'net ads'
Beginning with Samba 3.0.22 the 'ldap ssl = start tls' option also impacted LDAP connections to active directory domain controllers. Using the STARTTLS operation on LDAP port 389 connections. Starting with Samba 3.5.0 'ldap ssl ads = yes' was required in addition in order let to 'ldap ssl = start tls' have any effect on those connections.
'ldap ssl ads' was deprecated with Samba 4.8.0 and removed together with the whole functionality in Samba 4.14.0, because it didn't support tls channel bindings required for the sasl authentication.
The functionality is now re-added using the correct channel bindings based on the gnutls based tls implementation we already have, instead of using the tls layer provided by openldap. This makes it available and consistent with all LDAP client libraries we use and implement on our own.
The 'client ldap sasl wrapping' option gained the two new possible values: 'starttls' (using STARTTLS on tcp port 389) and 'ldaps' (using TLS directly on tcp port 636).
If you had 'ldap ssl = start tls' and 'ldap ssl ads = yes' before, you can now use 'client ldap sasl wrapping = starttls' in order to get STARTTLS on tcp port 389.
As we no longer use the openldap tls layer it is required to configure the correct certificate trusts with at least one of the following options: 'tls trust system cas', 'tls ca directories' or 'tls cafile'. While 'tls verify peer' and 'tls crlfile' are also relevant, see 'man smb.conf' for further details.
New DNS hostname config option
To get `net ads dns register` working correctly running manually or during a domain join a special entry in /etc/hosts was required. This not really documented and thus the DNS registration mostly didn't work. With the new option the default is [netbios name].[realm] which should be correct in the majority of use cases.
We will also use the value to create service principal names during a Kerberos authentication and DNS functions.
This is not supported in samba-tool yet.
Samba AD will rotate expired passwords on smartcard-required accounts
Traditionally in AD, accounts set to be "smart card require for logon" will have a password for NTLM fallback and local profile encryption (Windows DPAPI). This password previously would not expire.
Matching Windows behaviour, when the DC in a FL 2016 domain and the msDS-ExpirePasswordsOnSmartCardOnlyAccounts attribute on the domain root is set to TRUE, Samba will now expire these passwords and rotate them shortly before they expire.
Note that the password expiry time must be set to twice the TGT lifetime for smooth operation, e.g. daily expiry given a default 10 hour TGT lifetime, as the password is only rotated in the second half of its life. Again, this matches the Windows behaviour.
Provided the default 2016 schema is used, new Samba domains provisioned with Samba 4.21 will have this enabled once the domain functional level is set to 2016.
NOTE:
- Domains upgraded from older Samba versions will not have this set, even after the functional level preparation, matching thebehaviour of upgraded Windows AD domains.
Per-user and group "veto files" and "hide files"
"veto files" and "hide files" can optionally be restricted to certain users and groups. To apply a veto or hide directive to a filename for a specific user or group, a parametric option like this can be used:
hide files : USERNAME = /somefile.txt/ veto files : GROUPNAME = /otherfile.txt/
For details consult the updated smb.conf manpage.
Automatic keytab update after machine password change
When machine account password is updated, either by winbind doing regular updates or manually (e.g. net ads changetrustpw), now winbind will also support update of keytab entries in case you use newly added option 'sync machine password to keytab'.
The new parameter allows you to describe what keytabs and how should be updated. From smb.conf(5) manpage - each keytab can have exactly one of these four forms:
account_name
sync_spns
spn_prefixes=value1[,value2[...]]
spns=value1[,value2[...]]
The functionality provided by the removed commands "net ads keytab add/delete/add_update_ads" can be achieved via the 'sync machine password to keytab' as in these examples:
"net ads keytab add wurst/brot@REALM"
- this command is not adding <principal> to AD, so the best fit can be specifier "spns"
- add to smb.conf:
sync machine password to keytab = /path/to/keytab1:spns=wurst/brot@REALM:machine_password
- run:
"net ads keytab create"
"net ads keytab delete wurst/brot@REALM"
- remove the principal (or the whole keytab line if there was just one)
- run:
"net ads keytab create"
"net ads keytab add_update_ads wurst/brot@REALM"
- this command was adding the principal to AD, so for this case use a keytab with specifier sync_spns
- add to smb.conf:
sync machine password to keytab = /path/to/keytab2:sync_spns:machine_password
- run:
"net ads setspn add wurst/brot@REALM" # this adds the principal to AD "net ads keytab create" # this sync it from AD to local keytab
A new parameter 'sync machine password script' allows to specify external script that will be triggered after the automatic keytab update. If keytabs should be generated in clustered environments it is recommended to update them on all nodes. Check in smb.conf(5) the scripts winbind_ctdb_updatekeytab.sh and 46.update-keytabs.script in section 'sync machine password script' for details.
For detailed information check the smb.conf(5) and net(8) manpages.
New cephfs VFS module
Introduce new vfs-to-cephfs bridge which uses libcephfs low-level APIs (instead of path-based operations in the existing module). It allows users to pass explicit user-credentials per call (including supplementary groups), as well as faster operations using inode and file-handle caching on the Samba side.
Configuration is identical to existing module, but using 'ceph_new' instead of 'ceph' for the relevant smb.conf entries. This new module is expected to deprecate and replace the old one in next major release.
Group Managed Service Accounts
Samba 4.21 adds support for gMSAs (Group Managed Service Accounts), completing support for Functional Level 2012.
The purpose of a gMSA is to allow a single host, or a cluster of hosts, to share access to an automatically rotating password, avoiding the weak static service passwords that are often the entrypoint of attackers to AD domains. Each server has a strong and regularly rotated password, which is used to access the gMSA account of (e.g.) the database server.
Samba provides management and client tools, allowing services on Unix hosts to access the current and next gMSA passwords, as well as obtain a credentials cache.
Samba 4.20 announced the client-side tools for this feature. To avoid duplication and provide consistency, the existing commands for password viewing have been extended, so these commands operate both on a gMSA (with credentials, over LDAP, specify -H) and locally for accounts that have a compatible password (e.g. plaintext via GPG, compatible hash)
samba-tool user getpassword samba-tool user get-kerberos-ticket samba-tool domain exportkeytab
An example command, which gets the NT hash for use with NTLM, is
samba-tool user getpassword -H ldap://server --machine-pass \
TestUser1 --attributes=unicodePwd
Kerberos is a better choice (gMSA accounts should not use LDAP simple binds, for reasons of both security and compatibility). Use
samba-tool user get-kerberos-ticket -H ldap://server --machine-pass \
TestUser1 --output-krb5-ccache=/srv/service/krb5_ccache
gMSAs disclose a current and previous password. To access the previous NT hash, use:
samba-tool user getpassword -H ldap://server --machine-pass TestUser1 \
--attrs=unicodePwd;previous=1
To access the previous password as UTF8, use:
samba-tool user getpassword -H ldap://server --machine-pass TestUser1 \
--attributes=pwdLastSet,virtualClearTextUTF8;previous=1
However, Windows tools for dealing with gMSAs tend to use Active Directory Web Services (ADWS) from Powershell for setting up the accounts, and this separate protocol is not supported by Samba 4.21.
Samba-tool commands for handling gMSA (KDS) root keys
Group managed service accounts rotate passwords based on root keys, which can be managed using samba-tool, with commands such as
samba-tool domain kds root_key create samba-tool domain kds root_key list
Samba will create a new root key for new domains at provision time, but users of gMSA accounts on upgraded domains will need to first create a root key.
RFC 8070 PKINIT "Freshness extension" supported in the Heimdal KDC
The Heimdal KDC will recognise when a client provides proof that they hold the hardware token used for smart-card authentication 'now' and has not used a saved future-dated reply. Samba 4.21 now matches Windows and will assign an extra SID to the user in this case, allowing sensitive resources to be additionally protected.
Only Windows clients are known to support the client side of this feature at this time.
New samba-tool Authentication Policy management command structure
As foreshadowed in the Samba 4.20 release notes, the "samba-tool domain auth policy" commands have been reworked to be more intuitive based on user feedback and reflection.
Support for key features of AD Domain/Forest Functional Level 2012R2
Combined with other changes in recent versions (such as claims support in 4.20), Samba can now claim Functional Level 2012R2 support.
Build system
In previous versions of Samba, packagers of Samba would set their package-specific version strings using a patch to the SAMBA_VERSION_VENDOR_SUFFIX line in the ./VERSION file. Now that is achieved by using --vendor-suffix (at configure time), allowing this to be more easily scripted. Vendors are encouraged to include their name and full package version to assist with upstream debugging.
More deterministic builds
Samba builds are now more reproducible, providing better assurance that the Samba binaries you run are the same as what is expected from the source code. If locale settings are not changed, the same objects will be produced from each compilation run. If Samba is built in a different path, the object code will remain the same, but DWARF debugging sections will change (while remaining functionally equivalent).
See https://reproducible-builds.org/ for more information on this industry-wide effort and https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/samba.html for the status in Debian.
Improved command-line redaction
There are several options that can be used with Samba tools for specifying secrets. Although this is best avoided, when these options are used, Samba will redact the secrets in /proc, so that they won't be seen in ps or top. This is now carried out more thoroughly, redacting more options. There is a race inherent in this, and the passwords will be visible for a short time. The secrets are also not removed from .bash_history and similar files.
REMOVED FEATURES
Following commands are removed:
net ads keytab add <principal> net ads keytab delete <principal> net ads keytab add_update_ads
smb.conf changes
Parameter Name Description Default -------------- ----------- ------- client ldap sasl wrapping new values client use spnego principal removed ldap server require strong auth new values tls trust system cas new tls ca directories new dns hostname client dns name [netbios name].[realm] valid users Hardening invalid users Hardening read list Hardening write list Hardening veto files Added per-user and per-group vetos hide files Added per-user and per-group hides sync machine password to keytab keytabs sync machine password script script
CHANGES SINCE 4.21.0rc4
- David Disseldorp <ddiss@samba.org>
- BUG 15699: Incorrect FSCTL_QUERY_ALLOCATED_RANGES response when truncated.
- Noel Power <noel.power@suse.com>
- BUG 15702: Bad variable definition for ParseTuple causing test failure for Smb3UnixTests.test_create_context_reparse.
- Shachar Sharon <ssharon@redhat.com>
- BUG 15686: Add new vfs_ceph module (based on low level API).
CHANGES SINCE 4.21.0rc3
- Pavel Filipenský <pfilipensky@samba.org>
- BUG 15698: samba-tool can not load the default configuration file.
- Shachar Sharon <ssharon@redhat.com>
- BUG 15700: Crash when readlinkat fails.
CHANGES SINCE 4.21.0rc2
- Pavel Filipenský <pfilipensky@samba.org>
- BUG 15689: Can't add/delete special keys to keytab for nfs, cifs, http etc.
- Stefan Metzmacher <metze@samba.org>
- BUG 15696: Compound SMB2 requests don't return NT_STATUS_NETWORK_SESSION_EXPIRED for all requests, confuses MacOSX clients.
- Anoop C S <anoopcs@samba.org>
- BUG 15689: Can't add/delete special keys to keytab for nfs, cifs, http etc.
CHANGES SINCE 4.21.0rc1
- Andreas Schneider <asn@samba.org>
- BUG 15673: --version-* options are still not ergonomic, and they reject tilde characters.
- Anoop C S <anoopcs@samba.org>
- BUG 15686: Add new vfs_ceph module (based on low level API)
- Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
- BUG 15673: --version-* options are still not ergonomic, and they reject tilde characters.
- Jo Sutton <josutton@catalyst.net.nz>
- BUG 15690: ldb_version.h is missing from ldb public library
- Pavel Filipenský <pfilipensky@samba.org>
- BUG 15689: Can not add/delete special keys to keytab for nfs, cifs, http etc
- Shachar Sharon <ssharon@redhat.com>
- BUG 15686: Add new vfs_ceph module (based on low level API)
- Stefan Metzmacher <metze@samba.org>
- Volker Lendecke <vl@samba.org>
- BUG 15688: per user veto and hide file syntax is to complex
KNOWN ISSUES
Release_Planning_for_Samba_4.21#Release_blocking_bugs