Samba 4.7 Features added/changed

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Samba 4.7.0 rc 3

Release Notes for Samba 4.7.0 rc3
July 12, 2017

Release Announcements

This is the third release candidate of Samba 4.7. This is *not* intended for production environments and is designed for testing purposes only. Please report any defects via the Samba bug reporting system at https://bugzilla.samba.org/.

Samba 4.7 will be the next version of the Samba suite.

UPGRADING

smbclient changes

smbclient no longer prints a 'Domain=[...] OS=[Windows 6.1] Server=[...]' banner when connecting to the first server. With SMB2 and Kerberos there's no way to print this information reliable. Now we avoid it at all consistently. In interactive session the following banner is now presented to the user: 'Try "help" do get a list of possible commands.'.

The default for "client max protocol" has changed to "SMB3_11", which means that smbclient (and related commands) will work against servers without SMB1 support.

It's possible to use the '-m/--max-protocol' option to overwrite the "client max protocol" option temporary.

Note that the '-e/--encrypt' option also works with most SMB3 servers (e.g. Windows >= 2012 and Samba >= 4.0.0), so the SMB1 unix extensions are not required for encryption.

The change to SMB3_11 as default also means smbclient no longer negotiates SMB1 unix extensions by default, when talking to a Samba server with "unix extensions = yes". As a result some commands are not available, e.g. posix_encrypt, posix_open, posix_mkdir, posix_rmdir, posix_unlink, posix_whoami, getfacl and symlink. Using "-mNT1" reenabled them, if the server supports SMB1.

Note: the default ("CORE") for "client min protocol" hasn't changed, so it's still possible to connect to SMB1-only servers by default.

smbclient learned a new command "deltree" that is able to do a recursive deletion of a directory tree.

NEW FEATURES/CHANGES

Whole DB read locks: Improved LDAP and replication consistency

Prior to Samba 4.7 and ldb 1.2.0, the LDB database layer used by Samba erronously did not take whole-DB read locks to protect search and DRS replication operations.

While each object returned remained subject to a record-level lock (so would remain consistent to itself), under a race condition with a rename or delete, it and any links (like the member attribute) to it would not be returned.

The symptoms of this issue include:

Replication failures with this error showing in the client side logs:

error during DRS repl ADD: No objectClass found in replPropertyMetaData for Failed to commit objects:
WERR_GEN_FAILURE/NT_STATUS_INVALID_NETWORK_RESPONSE

A crash of the server, in particular the rpc_server process with

INTERNAL ERROR: Signal 11

LDAP read inconsistency

A DN subject to a search at the same time as it is being renamed may not appear under either the old or new name, but will re-appear for a subsequent search.

See BUG #12858 for more details and updated advise on database recovery for affected installations.

Samba AD with MIT Kerberos

After four years of development, Samba finally supports compiling and running Samba AD with MIT Kerberos. You can enable it with:

   ./configure --with-system-mitkrb5

Samba requires version 1.15.1 of MIT Kerberos to build with AD DC support. The krb5-devel and krb5-server packages are required. The feature set is not on par with with the Heimdal build but the most important things, like forest and external trusts, are working. Samba uses the KDC binary provided by MIT Kerberos.

Missing features, compared to Heimdal, are:

  • PKINIT support
  • S4U2SELF/S4U2PROXY support
  • RODC support (not fully working with Heimdal either)

The Samba AD process will take care of starting the MIT KDC and it will load a KDB (Kerberos Database) driver to access the Samba AD database. When provisioning an AD DC using 'samba-tool' it will take care of creating a correct kdc.conf file for the MIT KDC. Note that 'samba-tool' will overwrite the system kdc.conf by default. It is possible to use a different location during provision. You should consult the 'samba-tool' help and smb.conf manpage for details.

Dynamic RPC port range

The dynamic port range for RPC services has been changed from the old default value 1024-1300 to 49152-65535. This port range is not only used by a Samba AD DC but also applies to all other server roles including NT4-style domain controllers. The new value has been defined by Microsoft in Windows Server 2008 and newer versions. To make it easier for Administrators to control those port ranges we use the same default and make it configurable with the option: 'rpc server dynamic port range'.

The 'rpc server port' option sets the first available port from the new 'rpc server dynamic port range' option. The option 'rpc server port' only applies to Samba provisioned as an AD DC.

Authentication and Authorization audit support

Detailed authentication and authorization audit information is now logged to Samba's debug logs under the "auth_audit" debug class, including in particular the client IP address triggering the audit line. Additionally, if Samba is compiled against the jansson JSON library, a JSON representation is logged under the "auth_json_audit" debug class.

Audit support is comprehensive for all authentication and authorisation of user accounts in the Samba Active Directory Domain Controller, as well as the implicit authentication in password changes. In the file server and classic/NT4 domain controller, NTLM authentication, SMB and RPC authorization is covered, however password changes are not at this stage, and this support is not currently backed by a testsuite.

Multi-process LDAP Server

The LDAP server in the AD DC now honours the process model used for the rest of the samba process, rather than being forced into a single process. This aids in Samba's ability to scale to larger numbers of AD clients and the AD DC's overall resiliency, but will mean that there is a fork()ed child for every LDAP client, which may be more resource intensive in some situations.

Improved Read-Only Domain Controller (RODC) Support

Support for RODCs in Samba AD until now has been experimental. With this latest version, many of the critical bugs have been fixed and the RODC can be used in DC environments requiring no writable behaviour. RODCs now correctly support bad password lockouts and password disclosure auditing through the msDS-RevealedUsers attribute.

The fixes made to the RWDC will also allow Windows RODC to function more correctly and to avoid strange data omissions such as failures to replicate groups or updated passwords. Password changes are currently rejected at the RODC, although referrals should be given over LDAP. While any bad passwords can trigger domain-wide lockout, good passwords which have not been replicated yet for a password change can only be used via NTLM on the RODC (and not Kerberos).

The reliability of RODCs locating a writable partner still requires some improvements and so the 'password server' configuration option is generally recommended on the RODC.

Additional password hashes stored in supplementalCredentials

A new config option 'password hash userPassword schemes' has been added to enable generation of SHA-256 and SHA-512 hashes (without storing the plaintext password with reversible encryption). This builds upon previous work to improve password sync for the AD DC (originally using GPG).

The user command of 'samba-tool' has been updated in order to be able to extract these additional hashes, as well as extracting the (HTTP) WDigest hashes that we had also been storing in supplementalCredentials.

Improvements to DNS during Active Directory domain join

The 'samba-tool' domain join command will now add the A and GUID DNS records (on both the local and remote servers) during a join if possible via RPC. This should allow replication to proceed more smoothly post-join.

The mname element of the SOA record will now also be dynamically generated to point to the local read-write server. 'samba_dnsupdate' should now be more reliable as it will now find the appropriate name server even when resolv.conf points to a forwarder.

Significant AD performance and replication improvements

Previously, replication of group memberships was been an incredibly expensive process for the AD DC. This was mostly due to unnecessary CPU time being spent parsing member linked attributes. The database now stores these linked attributes in sorted form to perform efficient searches for existing members. In domains with a large number of group memberships, a join can now be completed in half the time compared with Samba 4.6.

LDAP search performance has also improved, particularly in the unindexed search case. Parsing and processing of security descriptors should now be more efficient, improving replication but also overall performance.

Query record for open file or directory

The record attached to an open file or directory in Samba can be queried through the 'net tdb locking' command. In clustered Samba this can be useful to determine the file or directory triggering corresponding "hot" record warnings in ctdb.

Removal of lpcfg_register_defaults_hook()

The undocumented and unsupported function lpcfg_register_defaults_hook() that was used by external projects to call into Samba and modify smb.conf default parameter settings has been removed. If your project was using this call please raise the issue on samba-technical@lists.samba.org in order to design a supported way of obtaining the same functionality.

Change of loadable module interface

The _init function of all loadable modules in Samba has changed from:

NTSTATUS _init(void);

to:

NTSTATUS _init(TALLOC_CTX *);

This allows a program loading a module to pass in a long-lived talloc context (which must be guaranteed to be alive for the lifetime of the module). This allows modules to avoid use of the talloc_autofree_context() (which is inherently thread-unsafe) and still be valgrind-clean on exit. Modules that don't need to free long-lived data on exit should use the NULL talloc context.

Parameter changes

The "strict sync" global parameter has been changed from a default of "no" to "yes". This means smbd will by default obey client requests to synchronize unwritten data in operating system buffers safely onto disk. This is a safer default setting for modern SMB1/2/3 clients.

The 'ntlm auth' option default is renamed to 'ntlmv2-only', reflecting the previous behaviour. Two new values have been provided, 'mschapv2-and-ntlmv2-only' (allowing MSCHAPv2 while denying NTLMv1) and 'disabled', totally disabling NTLM authentication and password changes.

CTDB changes=

  • CTDB no longer allows mixed minor versions in a cluster
See the AllowMixedVersions tunable option in ctdb-tunables(7) and also Upgrading_a_CTDB_cluster#Policy
  • CTDB now ignores hints from Samba about TDB flags when attaching to databases
CTDB will use the correct flags depending on the type of database. For clustered databases, the smb.conf setting dbwrap_tdb_mutexes:*=true will be ignored. Instead, CTDB continues to use the TDBMutexEnabled tunable.
  • New configuration variable CTDB_NFS_CHECKS_DIR
See ctdbd.conf(5) for more details.
  • The CTDB_SERVICE_AUTOSTARTSTOP configuration variable has been removed
To continue to manage/unmanage services while CTDB is running:
  • Start service by hand and then flag it as managed
  • Mark service as unmanaged and shut it down by hand
  • In some cases CTDB does something fancy - e.g. start Samba under "nice", so care is needed. One technique is to disable the eventscript, mark as managed, run the startup event by hand and then re-enable the eventscript.
  • The CTDB_SCRIPT_DEBUGLEVEL configuration variable has been removed
  • The example NFS Ganesha call-out has been improved
  • A new "replicated" database type is available
Replicated databases are intended for CTDB's internal use to replicate state data across the cluster, but may find other uses. The data in replicated databases is valid for the lifetime of CTDB and cleared on first attach.

smb.conf changes

 Parameter Name                     Description             Default
 --------------                     -----------             -------
 allow unsafe cluster upgrade       New parameter           no
 auth event notification            New parameter           no
 auth methods                       Deprecated
 client max protocol                Effective               SMB3_11
                                    default changed
 map untrusted to domain            New value/              auto
                                    Default changed/
                                    Deprecated
 mit kdc command                    New parameter
 profile acls                       Deprecated
 rpc server dynamic port range      New parameter           49152-65535
 strict sync                        Default changed         yes
 password hash userPassword schemes New parameter
 ntlm auth                          New values              ntlmv2-only


KNOWN ISSUES

 Release_blocking_bugs

CHANGES SINCE 4.7.0rc2

  • Jeremy Allison <jra@samba.org>
  • BUG #12836: s3: smbd: Fix a read after free if a chained SMB1 call goes async.
  • BUG #12899: s3: libsmb: Reverse sense of 'clear all attributes', ignore attribute change in SMB2 to match SMB1.
  • BUG #12914: s3: smbclient: Add new command deltree.
  • Ralph Boehme <slow@samba.org>
  • BUG #12885: s3/smbd: Let non_widelink_open() chdir() to directories directly.
  • BUG #12887: Remove SMB_VFS_STRICT_UNLOCK noop from the VFS.
  • BUG #12891: Enable TDB mutexes in dbwrap and ctdb.
  • BUG #12897: vfs_fruit: don't use MS NFS ACEs with Windows clients.
  • BUG #12910: s3/notifyd: Ensure notifyd doesn't return from smbd_notifyd_init.
  • Alexander Bokovoy <ab@samba.org>
  • BUG #12905: Build py3 versions of other rpc modules.
  • Günther Deschner <gd@samba.org>
  • BUG #12840: vfs_fruit: Add "fruit:model = <modelname>" parametric option.
  • Dustin L. Howett
  • BUG #12720: idmap_ad: Retry query_user exactly once if we get TLDAP_SERVER_DOWN.
  • Amitay Isaacs <amitay@gmail.com>
  • BUG #12891: dbwrap_ctdb: Fix calculation of persistent flag.
  • Thomas Jarosch <thomas.jarosch@intra2net.com>
  • BUG #12927: s3: libsmb: Fix use-after-free when accessing pointer *p.
  • Volker Lendecke <vl@samba.org>
  • BUG #12925: smbd: Fix a connection run-down race condition.
  • Stefan Metzmacher <metze@samba.org>
  • tevent: version 0.9.33: make tevent_req_print() more robust against crashes.
  • ldb: version 1.2.1
  • BUG #12882BUG 12882: Do not install _ldb_text.py if we have system libldb.
  • BUG #12890BUG 12890: s3:smbd: consistently use talloc_tos() memory for rpc_pipe_open_interface().
  • BUG #12900BUG 12900: Fix index out of bound in ldb_msg_find_common_values.
  • Rowland Penny <rpenny@samba.org>
  • BUG #12884BUG 12884: Easily edit a users object in AD, as if using 'ldbedit'.
  • Bernhard M. Wiedemann <bwiedemann@suse.de>
  • Andreas Schneider <asn@samba.org>
  • BUG #12882BUG 12882: waf: Do not install _ldb_text.py if we have system libldb.
  • Martin Schwenke <martin@meltin.net>
  • BUG #12898BUG 12898: ctdb-common: Set close-on-exec when creating PID file.

Changes since 4.7.0rc1

  • Jeffrey Altman <jaltman@secure-endpoints.com>
  • BUG #12894: CVE-2017-11103: Orpheus' Lyre KDC-REP service name validation