From 5296e0d1e84269a7a8a1287afd47ae52b5577757 Mon Sep 17 00:00:00 2001 From: Jelmer Vernooij Date: Sat, 15 Feb 2003 14:44:25 +0000 Subject: Add draft of universal passdb document that combines ENCRYPTION.sgml, Samba-LDAP-HOWTO.sgml, pdb_mysql.sgml and pdb_xml.sgml (This used to be commit fc26d1bfd15e8762628f115dd18e9d716bbea0e8) --- docs/docbook/projdoc/passdb.sgml | 933 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 933 insertions(+) create mode 100644 docs/docbook/projdoc/passdb.sgml (limited to 'docs') diff --git a/docs/docbook/projdoc/passdb.sgml b/docs/docbook/projdoc/passdb.sgml new file mode 100644 index 0000000000..7f59cac7f3 --- /dev/null +++ b/docs/docbook/projdoc/passdb.sgml @@ -0,0 +1,933 @@ + + + + JelmerVernooij + + The Samba Team +
jelmer@samba.org
+ + + + Gerald (Jerry)Carter + + Samba Team +
jerry@samba.org
+ + + + Olivier (lem)Lemaire + + IDEALX +
olem@IDEALX.org
+ + + + JeremyAllison + + Samba Team +
+ jra@samba.org +
+ + + February 2003 + + +User information database + + + Introduction + + Newer windows clients send encrypted passwords over + the wire, instead of plain text passwords. The newest clients + will only send encrypted passwords and refuse to send plain text + passwords, unless their registry is tweaked. + + These passwords can't be converted to unix style encrypted + passwords. Because of that you can't use the standard unix + user database, and you have to store the Lanman and NT hashes + somewhere else. For more information, see the documentation + about the passdb backend = parameter. + + + + + Important Notes About Security + + The unix and SMB password encryption techniques seem similar + on the surface. This similarity is, however, only skin deep. The unix + scheme typically sends clear text passwords over the network when + logging in. This is bad. The SMB encryption scheme never sends the + cleartext password over the network but it does store the 16 byte + hashed values on disk. This is also bad. Why? Because the 16 byte hashed + values are a "password equivalent". You cannot derive the user's + password from them, but they could potentially be used in a modified + client to gain access to a server. This would require considerable + technical knowledge on behalf of the attacker but is perfectly possible. + You should thus treat the smbpasswd file as though it contained the + cleartext passwords of all your users. Its contents must be kept + secret, and the file should be protected accordingly. + + Ideally we would like a password scheme which neither requires + plain text passwords on the net or on disk. Unfortunately this + is not available as Samba is stuck with being compatible with + other SMB systems (WinNT, WfWg, Win95 etc). + + + Note that Windows NT 4.0 Service pack 3 changed the + default for permissible authentication so that plaintext + passwords are never sent over the wire. + The solution to this is either to switch to encrypted passwords + with Samba or edit the Windows NT registry to re-enable plaintext + passwords. See the document WinNT.txt for details on how to do + this. + + Other Microsoft operating systems which also exhibit + this behavior includes + + + MS DOS Network client 3.0 with + the basic network redirector installed + + Windows 95 with the network redirector + update installed + + Windows 98 [se] + + Windows 2000 + + + Note :All current release of + Microsoft SMB/CIFS clients support authentication via the + SMB Challenge/Response mechanism described here. Enabling + clear text authentication does not disable the ability + of the client to participate in encrypted authentication. + + + + Advantages of SMB Encryption + + + plain text passwords are not passed across + the network. Someone using a network sniffer cannot just + record passwords going to the SMB server. + + + WinNT doesn't like talking to a server + that isn't using SMB encrypted passwords. It will refuse + to browse the server if the server is also in user level + security mode. It will insist on prompting the user for the + password on each connection, which is very annoying. The + only things you can do to stop this is to use SMB encryption. + + + + + + + Advantages of non-encrypted passwords + + + plain text passwords are not kept + on disk. + + uses same password file as other unix + services such as login and ftp + + you are probably already using other + services (such as telnet and ftp) which send plain text + passwords over the net, so sending them for SMB isn't + such a big deal. + + + + + + + The smbpasswd Command + + The smbpasswd command maintains the two 32 byte password fields + in the smbpasswd file. If you wish to make it similar to the unix + passwd or yppasswd programs, + install it in /usr/local/samba/bin/ (or your + main Samba binary directory). + + smbpasswd now works in a client-server mode + where it contacts the local smbd to change the user's password on its + behalf. This has enormous benefits - as follows. + + smbpasswd now has the capability + to change passwords on Windows NT servers (this only works when + the request is sent to the NT Primary Domain Controller if you + are changing an NT Domain user's password). + + To run smbpasswd as a normal user just type : + + $ smbpasswd + Old SMB password: <type old value here - + or hit return if there was no old password> + New SMB Password: <type new value> + + Repeat New SMB Password: <re-type new value + + + If the old value does not match the current value stored for + that user, or the two new values do not match each other, then the + password will not be changed. + + If invoked by an ordinary user it will only allow the user + to change his or her own Samba password. + + If run by the root user smbpasswd may take an optional + argument, specifying the user name whose SMB password you wish to + change. Note that when run as root smbpasswd does not prompt for + or check the old password value, thus allowing root to set passwords + for users who have forgotten their passwords. + + smbpasswd is designed to work in the same way + and be familiar to UNIX users who use the passwd or + yppasswd commands. + + For more details on using smbpasswd refer + to the man page which will always be the definitive reference. + + + + + +LDAP + + +Introduction + + +This document describes how to use an LDAP directory for storing Samba user +account information traditionally stored in the smbpasswd(5) file. It is +assumed that the reader already has a basic understanding of LDAP concepts +and has a working directory server already installed. For more information +on LDAP architectures and Directories, please refer to the following sites. + + + + OpenLDAP - http://www.openldap.org/ + iPlanet Directory Server - http://iplanet.netscape.com/directory + + + +Note that O'Reilly Publishing is working on +a guide to LDAP for System Administrators which has a planned release date of +early summer, 2002. + + + +Two additional Samba resources which may prove to be helpful are + + + + The Samba-PDC-LDAP-HOWTO + maintained by Ignacio Coupeau. + + The NT migration scripts from IDEALX that are + geared to manage users and group in such a Samba-LDAP Domain Controller configuration. + + + + + + +Introduction + + +Traditionally, when configuring "encrypt +passwords = yes" in Samba's smb.conf file, user account +information such as username, LM/NT password hashes, password change times, and account +flags have been stored in the smbpasswd(5) file. There are several +disadvantages to this approach for sites with very large numbers of users (counted +in the thousands). + + + + +The first is that all lookups must be performed sequentially. Given that +there are approximately two lookups per domain logon (one for a normal +session connection such as when mapping a network drive or printer), this +is a performance bottleneck for lareg sites. What is needed is an indexed approach +such as is used in databases. + + + +The second problem is that administrators who desired to replicate a +smbpasswd file to more than one Samba server were left to use external +tools such as rsync(1) and ssh(1) +and wrote custom, in-house scripts. + + + +And finally, the amount of information which is stored in an +smbpasswd entry leaves no room for additional attributes such as +a home directory, password expiration time, or even a Relative +Identified (RID). + + + + +As a result of these defeciencies, a more robust means of storing user attributes +used by smbd was developed. The API which defines access to user accounts +is commonly referred to as the samdb interface (previously this was called the passdb +API, and is still so named in the CVS trees). In Samba 2.2.3, enabling support +for a samdb backend (e.g. --with-ldapsam or +--with-tdbsam) requires compile time support. + + + +When compiling Samba to include the --with-ldapsam autoconf +option, smbd (and associated tools) will store and lookup user accounts in +an LDAP directory. In reality, this is very easy to understand. If you are +comfortable with using an smbpasswd file, simply replace "smbpasswd" with +"LDAP directory" in all the documentation. + + + +There are a few points to stress about what the --with-ldapsam +does not provide. The LDAP support referred to in the this documentation does not +include: + + + + A means of retrieving user account information from + an Windows 2000 Active Directory server. + A means of replacing /etc/passwd. + + + +The second item can be accomplished by using LDAP NSS and PAM modules. LGPL +versions of these libraries can be obtained from PADL Software +(http://www.padl.com/). However, +the details of configuring these packages are beyond the scope of this document. + + + + + +Supported LDAP Servers + + +The LDAP samdb code in 2.2.3 has been developed and tested using the OpenLDAP +2.0 server and client libraries. The same code should be able to work with +Netscape's Directory Server and client SDK. However, due to lack of testing +so far, there are bound to be compile errors and bugs. These should not be +hard to fix. If you are so inclined, please be sure to forward all patches to +samba-patches@samba.org and +jerry@samba.org. + + + + + +Schema and Relationship to the RFC 2307 posixAccount + + + +Samba 3.0 includes the necessary schema file for OpenLDAP 2.0 in +examples/LDAP/samba.schema. The sambaAccount objectclass is given here: + + + +objectclass ( 1.3.1.5.1.4.1.7165.2.2.2 NAME 'sambaAccount' SUP top STRUCTURAL + DESC 'Samba Account' + MUST ( uid $ rid ) + MAY ( cn $ lmPassword $ ntPassword $ pwdLastSet $ logonTime $ + logoffTime $ kickoffTime $ pwdCanChange $ pwdMustChange $ acctFlags $ + displayName $ smbHome $ homeDrive $ scriptPath $ profilePath $ + description $ userWorkstations $ primaryGroupID $ domain )) + + + +The samba.schema file has been formatted for OpenLDAP 2.0. The OID's are +owned by the Samba Team and as such is legal to be openly published. +If you translate the schema to be used with Netscape DS, please +submit the modified schema file as a patch to jerry@samba.org + + + +Just as the smbpasswd file is mean to store information which supplements a +user's /etc/passwd entry, so is the sambaAccount object +meant to supplement the UNIX user account information. A sambaAccount is a +STRUCTURAL objectclass so it can be stored individually +in the directory. However, there are several fields (e.g. uid) which overlap +with the posixAccount objectclass outlined in RFC2307. This is by design. + + + + + +In order to store all user account information (UNIX and Samba) in the directory, +it is necessary to use the sambaAccount and posixAccount objectclasses in +combination. However, smbd will still obtain the user's UNIX account +information via the standard C library calls (e.g. getpwnam(), et. al.). +This means that the Samba server must also have the LDAP NSS library installed +and functioning correctly. This division of information makes it possible to +store all Samba account information in LDAP, but still maintain UNIX account +information in NIS while the network is transitioning to a full LDAP infrastructure. + + + + +Configuring Samba with LDAP + + + +OpenLDAP configuration + + +To include support for the sambaAccount object in an OpenLDAP directory +server, first copy the samba.schema file to slapd's configuration directory. + + + +root# cp samba.schema /etc/openldap/schema/ + + + +Next, include the samba.schema file in slapd.conf. +The sambaAccount object contains two attributes which depend upon other schema +files. The 'uid' attribute is defined in cosine.schema and +the 'displayName' attribute is defined in the inetorgperson.schema +file. Both of these must be included before the samba.schema file. + + + +## /etc/openldap/slapd.conf + +## schema files (core.schema is required by default) +include /etc/openldap/schema/core.schema + +## needed for sambaAccount +include /etc/openldap/schema/cosine.schema +include /etc/openldap/schema/inetorgperson.schema +include /etc/openldap/schema/samba.schema + +## uncomment this line if you want to support the RFC2307 (NIS) schema +## include /etc/openldap/schema/nis.schema + +.... + + + +It is recommended that you maintain some indices on some of the most usefull attributes, +like in the following example, to speed up searches made on sambaAccount objectclasses +(and possibly posixAccount and posixGroup as well). + + +# Indices to maintain +## required by OpenLDAP 2.0 +index objectclass eq + +## support pb_getsampwnam() +index uid pres,eq +## support pdb_getsambapwrid() +index rid eq + +## uncomment these if you are storing posixAccount and +## posixGroup entries in the directory as well +##index uidNumber eq +##index gidNumber eq +##index cn eq +##index memberUid eq + + + + + +Configuring Samba + + + +The following parameters are available in smb.conf only with --with-ldapsam +was included with compiling Samba. + + + + ldap ssl + ldap server + ldap admin dn + ldap suffix + ldap filter + ldap port + + + +These are described in the smb.conf(5) man +page and so will not be repeated here. However, a sample smb.conf file for +use with an LDAP directory could appear as + + + +## /usr/local/samba/lib/smb.conf +[global] + security = user + encrypt passwords = yes + + netbios name = TASHTEGO + workgroup = NARNIA + + # ldap related parameters + + # define the DN to use when binding to the directory servers + # The password for this DN is not stored in smb.conf. Rather it + # must be set by using 'smbpasswd -w secretpw' to store the + # passphrase in the secrets.tdb file. If the "ldap admin dn" values + # changes, this password will need to be reset. + ldap admin dn = "cn=Samba Manager,ou=people,dc=samba,dc=org" + + # specify the LDAP server's hostname (defaults to locahost) + ldap server = ahab.samba.org + + # Define the SSL option when connecting to the directory + # ('off', 'start tls', or 'on' (default)) + ldap ssl = start tls + + # define the port to use in the LDAP session (defaults to 636 when + # "ldap ssl = on") + ldap port = 389 + + # specify the base DN to use when searching the directory + ldap suffix = "ou=people,dc=samba,dc=org" + + # generally the default ldap search filter is ok + # ldap filter = "(&(uid=%u)(objectclass=sambaAccount))" + + + + + + + + +Accounts and Groups management + + +As users accounts are managed thru the sambaAccount objectclass, you should +modify you existing administration tools to deal with sambaAccount attributes. + + + +Machines accounts are managed with the sambaAccount objectclass, just +like users accounts. However, it's up to you to stored thoses accounts +in a different tree of you LDAP namespace: you should use +"ou=Groups,dc=plainjoe,dc=org" to store groups and +"ou=People,dc=plainjoe,dc=org" to store users. Just configure your +NSS and PAM accordingly (usually, in the /etc/ldap.conf configuration +file). + + + +In Samba release 3.0, the group management system is based on posix +groups. This means that Samba make usage of the posixGroup objectclass. +For now, there is no NT-like group system management (global and local +groups). + + + + + +Security and sambaAccount + + + +There are two important points to remember when discussing the security +of sambaAccount entries in the directory. + + + + Never retrieve the lmPassword or + ntPassword attribute values over an unencrypted LDAP session. + Never allow non-admin users to + view the lmPassword or ntPassword attribute values. + + + +These password hashes are clear text equivalents and can be used to impersonate +the user without deriving the original clear text strings. For more information +on the details of LM/NT password hashes, refer to the ENCRYPTION chapter of the Samba-HOWTO-Collection. + + + +To remedy the first security issue, the "ldap ssl" smb.conf parameter defaults +to require an encrypted session (ldap ssl = on) using +the default port of 636 +when contacting the directory server. When using an OpenLDAP 2.0 server, it +is possible to use the use the StartTLS LDAP extended operation in the place of +LDAPS. In either case, you are strongly discouraged to disable this security +(ldap ssl = off). + + + +Note that the LDAPS protocol is deprecated in favor of the LDAPv3 StartTLS +extended operation. However, the OpenLDAP library still provides support for +the older method of securing communication between clients and servers. + + + +The second security precaution is to prevent non-administrative users from +harvesting password hashes from the directory. This can be done using the +following ACL in slapd.conf: + + + +## allow the "ldap admin dn" access, but deny everyone else +access to attrs=lmPassword,ntPassword + by dn="cn=Samba Admin,ou=people,dc=plainjoe,dc=org" write + by * none + + + + + + + + +LDAP specials attributes for sambaAccounts + + +The sambaAccount objectclass is composed of the following attributes: + + + + + lmPassword: the LANMAN password 16-byte hash stored as a character + representation of a hexidecimal string. + + ntPassword: the NT password hash 16-byte stored as a character + representation of a hexidecimal string. + + pwdLastSet: The integer time in seconds since 1970 when the + lmPassword and ntPassword attributes were last set. + + + acctFlags: string of 11 characters surrounded by square brackets [] + representing account flags such as U (user), W(workstation), X(no password expiration), and + D(disabled). + + logonTime: Integer value currently unused + + logoffTime: Integer value currently unused + + kickoffTime: Integer value currently unused + + pwdCanChange: Integer value currently unused + + pwdMustChange: Integer value currently unused + + homeDrive: specifies the drive letter to which to map the + UNC path specified by homeDirectory. The drive letter must be specified in the form "X:" + where X is the letter of the drive to map. Refer to the "logon drive" parameter in the + smb.conf(5) man page for more information. + + scriptPath: The scriptPath property specifies the path of + the user's logon script, .CMD, .EXE, or .BAT file. The string can be null. The path + is relative to the netlogon share. Refer to the "logon script" parameter in the + smb.conf(5) man page for more information. + + profilePath: specifies a path to the user's profile. + This value can be a null string, a local absolute path, or a UNC path. Refer to the + "logon path" parameter in the smb.conf(5) man page for more information. + + smbHome: The homeDirectory property specifies the path of + the home directory for the user. The string can be null. If homeDrive is set and specifies + a drive letter, homeDirectory should be a UNC path. The path must be a network + UNC path of the form \\server\share\directory. This value can be a null string. + Refer to the "logon home" parameter in the smb.conf(5) man page for more information. + + + userWorkstation: character string value currently unused. + + + rid: the integer representation of the user's relative identifier + (RID). + + primaryGroupID: the relative identifier (RID) of the primary group + of the user. + + + + +The majority of these parameters are only used when Samba is acting as a PDC of +a domain (refer to the Samba-PDC-HOWTO for details on +how to configure Samba as a Primary Domain Controller). The following four attributes +are only stored with the sambaAccount entry if the values are non-default values: + + + + smbHome + scriptPath + logonPath + homeDrive + + + +These attributes are only stored with the sambaAccount entry if +the values are non-default values. For example, assume TASHTEGO has now been +configured as a PDC and that logon home = \\%L\%u was defined in +its smb.conf file. When a user named "becky" logons to the domain, +the logon home string is expanded to \\TASHTEGO\becky. +If the smbHome attribute exists in the entry "uid=becky,ou=people,dc=samba,dc=org", +this value is used. However, if this attribute does not exist, then the value +of the logon home parameter is used in its place. Samba +will only write the attribute value to the directory entry is the value is +something other than the default (e.g. \\MOBY\becky). + + + + + + + + +Example LDIF Entries for a sambaAccount + + + +The following is a working LDIF with the inclusion of the posixAccount objectclass: + + + +dn: uid=guest2, ou=people,dc=plainjoe,dc=org +ntPassword: 878D8014606CDA29677A44EFA1353FC7 +pwdMustChange: 2147483647 +primaryGroupID: 1201 +lmPassword: 552902031BEDE9EFAAD3B435B51404EE +pwdLastSet: 1010179124 +logonTime: 0 +objectClass: sambaAccount +uid: guest2 +kickoffTime: 2147483647 +acctFlags: [UX ] +logoffTime: 2147483647 +rid: 19006 +pwdCanChange: 0 + + + +The following is an LDIF entry for using both the sambaAccount and +posixAccount objectclasses: + + + +dn: uid=gcarter, ou=people,dc=plainjoe,dc=org +logonTime: 0 +displayName: Gerald Carter +lmPassword: 552902031BEDE9EFAAD3B435B51404EE +primaryGroupID: 1201 +objectClass: posixAccount +objectClass: sambaAccount +acctFlags: [UX ] +userPassword: {crypt}BpM2ej8Rkzogo +uid: gcarter +uidNumber: 9000 +cn: Gerald Carter +loginShell: /bin/bash +logoffTime: 2147483647 +gidNumber: 100 +kickoffTime: 2147483647 +pwdLastSet: 1010179230 +rid: 19000 +homeDirectory: /home/tashtego/gcarter +pwdCanChange: 0 +pwdMustChange: 2147483647 +ntPassword: 878D8014606CDA29677A44EFA1353FC7 + + + + + + +Passdb MySQL plugin + + +Building + +To build the plugin, run make bin/pdb_mysql.so +in the source/ directory of samba distribution. + + +Next, copy pdb_mysql.so to any location you want. I +strongly recommend installing it in $PREFIX/lib or /usr/lib/samba/ + + + + +Creating the database + + +You either can set up your own table and specify the field names to pdb_mysql (see below +for the column names) or use the default table. The file examples/pdb/mysql/mysql.dump +contains the correct queries to create the required tables. Use the command : + +mysql -uusername -hhostname -ppassword databasename < /path/to/samba/examples/pdb/mysql/mysql.dump + + + + + +Configuring + +This plugin lacks some good documentation, but here is some short info: + +Add a the following to the passdb backend variable in your smb.conf: + +passdb backend = [other-plugins] plugin:/location/to/pdb_mysql.so:identifier [other-plugins] + + + +The identifier can be any string you like, as long as it doesn't collide with +the identifiers of other plugins or other instances of pdb_mysql. If you +specify multiple pdb_mysql.so entries in 'passdb backend', you also need to +use different identifiers! + + + +Additional options can be given thru the smb.conf file in the [global] section. + + + +identifier:mysql host - host name, defaults to 'localhost' +identifier:mysql password +identifier:mysql user - defaults to 'samba' +identifier:mysql database - defaults to 'samba' +identifier:mysql port - defaults to 3306 +identifier:table - Name of the table containing users + + + + +WARNING: since the password for the mysql user is stored in the +smb.conf file, you should make the the smb.conf file +readable only to the user that runs samba. This is considered a security +bug and will be fixed soon. + + +Names of the columns in this table(I've added column types those columns should have first): + + +identifier:logon time column - int(9) +identifier:logoff time column - int(9) +identifier:kickoff time column - int(9) +identifier:pass last set time column - int(9) +identifier:pass can change time column - int(9) +identifier:pass must change time column - int(9) +identifier:username column - varchar(255) - unix username +identifier:domain column - varchar(255) - NT domain user is part of +identifier:nt username column - varchar(255) - NT username +identifier:fullname column - varchar(255) - Full name of user +identifier:home dir column - varchar(255) - Unix homedir path +identifier:dir drive column - varchar(2) - Directory drive path (eg: 'H:') +identifier:logon script column - varchar(255) - Batch file to run on client side when logging on +identifier:profile path column - varchar(255) - Path of profile +identifier:acct desc column - varchar(255) - Some ASCII NT user data +identifier:workstations column - varchar(255) - Workstations user can logon to (or NULL for all) +identifier:unknown string column - varchar(255) - unknown string +identifier:munged dial column - varchar(255) - ? +identifier:uid column - int(9) - Unix user ID (uid) +identifier:gid column - int(9) - Unix user group (gid) +identifier:user sid column - varchar(255) - NT user SID +identifier:group sid column - varchar(255) - NT group ID +identifier:lanman pass column - varchar(255) - encrypted lanman password +identifier:nt pass column - varchar(255) - encrypted nt passwd +identifier:plain pass column - varchar(255) - plaintext password +identifier:acct control column - int(9) - nt user data +identifier:unknown 3 column - int(9) - unknown +identifier:logon divs column - int(9) - ? +identifier:hours len column - int(9) - ? +identifier:unknown 5 column - int(9) - unknown +identifier:unknown 6 column - int(9) - unknown + + + +Eventually, you can put a colon (:) after the name of each column, which +should specify the column to update when updating the table. You can also +specify nothing behind the colon - then the data from the field will not be +updated. + + + + + +Using plaintext passwords or encrypted password + + +I strongly discourage the use of plaintext passwords, however, you can use them: + + + +If you would like to use plaintext passwords, set 'identifier:lanman pass column' and 'identifier:nt pass column' to 'NULL' (without the quotes) and 'identifier:plain pass column' to the name of the column containing the plaintext passwords. + + + +If you use encrypted passwords, set the 'identifier:plain pass column' to 'NULL' (without the quotes). This is the default. + + + + + +Getting non-column data from the table + + +It is possible to have not all data in the database and making some 'constant'. + + + +For example, you can set 'identifier:fullname column' to : +CONCAT(First_name,' ',Sur_name) + + + +Or, set 'identifier:workstations column' to : +NULL + +See the MySQL documentation for more language constructs. + + + + + +Passdb XML plugin + + +Building + +This module requires libxml2 to be installed. + +To build pdb_xml, run: make bin/pdb_xml.so in +the directory source/. + + + + +Usage + +The usage of pdb_xml is pretty straightforward. To export data, use: + +pdbedit -e plugin:/usr/lib/samba/pdb_xml.so:filename + +(where filename is the name of the file to put the data in) + + + +To import data, use: +pdbedit -i plugin:/usr/lib/samba/pdb_xml.so:filename -e current-pdb + +Where filename is the name to read the data from and current-pdb to put it in. + + + + + -- cgit