Annotation of src/usr.bin/sudo/README.LDAP, Revision 1.2
1.1 millert 1: This file explains how to use the optional LDAP functionality of SUDO to
2: store /etc/sudoers information. This feature is distinct from LDAP passwords.
3:
4: LDAP philosophy
5: ===============
6: As times change and servers become cheap, an enterprise can easily have 500+
7: UNIX servers. Using LDAP to synchronize Users, Groups, Hosts, Mounts, and
8: others across an enterprise can greatly reduce the administrative overhead.
9:
10: Sudo in the past has only used a single local configuration file /etc/sudoers.
11: Some have attempted to workaround this by synchronizing changes via
12: RCS/CVS/RSYNC/RDIST/RCP/SCP and even NFS. Many have asked for a Hesiod, NIS,
13: or LDAP patch for sudo, so here is my attempt at LDAP'izing sudo.
14:
1.2 ! millert 15: For information on OpenLDAP, please see http://www.openldap.org/.
! 16:
1.1 millert 17: Definitions
18: ===========
19: Many times the word 'Directory' is used in the document to refer to the LDAP
20: server, structure and contents.
21:
22: Many times 'options' are used in this document to refer to sudoer 'defaults'.
23: They are one and the same.
24:
25: Design Features
26: ===============
27:
28: * Sudo no longer needs to read sudoers in its entirety. Parsing of
29: /etc/sudoers requires the entire file to be read. The LDAP feature of sudo
30: uses two (sometimes three) LDAP queries per invocation. It never reads all
31: the sudoer entries in the LDAP store. This makes it especially fast and
32: particularly usable in LDAP environments. The first query is to parse
33: default options (see below). The second is to match against the username or
34: groups a user belongs to. (The special ALL tag is matched in this query
35: too.) If no match is made against the username, the third query pulls the
36: entries that match against user netgroups to compare back to the user.
37:
38: * Sudo no longer blows up if there is a typo. Parsing of /etc/sudoers can
39: still blow up when sudo is invoked. However when using the LDAP feature of
40: sudo, LDAP syntax rules are applied before the data is uploaded into the
41: LDAP server, so proper syntax is always guaranteed! One can of course still
42: insert a bogus hostname or username, but sudo will not care.
43:
44: * Options inside of entries now override global default options.
45: /etc/sudoers allowed for only default options and limited options associated
46: with user/host/command aliases. The syntax can be difficult for the newbie.
47: The LDAP feature attempts to simplify this and yet still provide maximum
48: flexibility.
49:
50: Sudo first looks for an entry called 'cn=default' in the SUDOers container.
51: If found, the multi-valued sudoOption attribute is parsed the same way the
52: global 'Defaults' line in /etc/sudoers is parsed.
53:
54: If on the second or third query, a response contains a sudoRole which
55: matches against the user, host, and command, then the matched object is
56: scanned for a additional options to override the top-level defaults. See
57: the example LDAP content below for more information.
58:
59: * Visudo is no longer needed. Visudo provides locking and syntax checking
60: against the /etc/sudoers file. Since LDAP updates are atomic, locking is no
61: longer necessary. Because syntax is checked when the data is inserted into
62: LDAP, the sudoers syntax check becomes unnecessary.
63:
64: * Aliases are no longer needed. User, Host, and Command Aliases were setup
65: to allow simplification and readability of the sudoers files. Since the
66: LDAP sudoer entry allows multiple values for each of its attributes and
67: since most LDAP browsers are graphical and easy to work with, original
68: aliases are no longer needed.
69:
70: If you want to specify lots of users into an entry or want to have similar
71: entries with identical users, then use either groups or user netgroups.
72: Thats what groups and netgroups are for and Sudo handles this well.
73: Alternately, one can just paste them all into the LDAP record.
74:
75: If you want to specify lots of hosts into an entry, use netgroups or IP
76: address matches (10.2.3.4/255.255.0.0). Thats what netgroups are for and
77: Sudo handles this well. Or just past them all into the LDAP record.
78:
79: If you want to specify lots of commands, use directories or wildcards, or
80: just paste them all into LDAP. That's what it's for.
81:
82: * The /etc/sudoers file can be disabled. Paranoid security administrators
83: can now disallow parsing of any local /etc/sudoers file by an LDAP
84: sudoOption 'ignore_local_sudoers'. This way all sudoers can be controlled
85: and audited in one place because local entries are not allowed.
86: In fact, if this option is included in the cn=defaults object of LDAP,
87: sudo won't even look for a /etc/sudoers file.
88:
89: * The sudo binary compiled with LDAP support should be totally backward
90: compatible and be syntactically and source code equivalent to its non
91: LDAP-enabled build.
92:
93:
94: Build instructions
95: ==================
96: The most simplest way to build sudo with LDAP support is to include the
1.2 ! millert 97: '--with-ldap' option.
1.1 millert 98:
1.2 ! millert 99: $ ./configure --with-ldap
1.1 millert 100:
1.2 ! millert 101: If your ldap libraries and headers are in a non-standard place, you will need
! 102: to specify them at configure time. E.g.
1.1 millert 103:
1.2 ! millert 104: $ ./configure --with-ldap=/usr/local/ldapsdk
1.1 millert 105:
1.2 ! millert 106: Sudo is developed using OpenLDAP. Other LDAP implementations may
! 107: require adding '-lldif' to SUDO_LIBS in the Makefile.
1.1 millert 108:
1.2 ! millert 109: Your Mileage may vary. Please let the sudo workers mailing list
! 110: <sudo-workers@sudo.ws> know what combinations worked best for your
! 111: OS and LDAP Combinations so we can improve sudo.
1.1 millert 112:
113: More Build Notes:
114: HP-UX 11.23 (gcc3) Galen Johnson <Galen.Johnson@sas.com>
115: CFLAGS="-D__10_10_compat_code" LDFLAGS="-L/opt/ldapux/lib"
116:
117: Schema Changes
118: ==============
1.2 ! millert 119: Add the appropriate schema to your LDAP server so that it may contain
! 120: sudoers content.
1.1 millert 121:
1.2 ! millert 122: For OpenLDAP, simply copy schema.OpenLDAP to the schema directory
! 123: (e.g. /etc/openldap/schema) and 'include' it in your slapd.conf and
! 124: restart slapd. For other LDAP servers, provide this to your LDAP
! 125: Administrator. Make sure to index the attribute 'sudoUser'.
1.1 millert 126:
1.2 ! millert 127: For the SunONE or iPlanet LDAP server, use the schema.iPlanet file.
1.1 millert 128:
129: Importing /etc/sudoers to LDAP
130: ==============================
131: Importing is a two step process.
132:
133: Step 1:
134: Ask your LDAP Administrator where to create the ou=SUDOers container.
1.2 ! millert 135:
! 136: For instance, if using OpenLDAP:
! 137:
! 138: dn: ou=SUDOers,dc=example,dc=com
! 139: objectClass: top
! 140: objectClass: organizationalUnit
! 141: ou: SUDOers
! 142:
1.1 millert 143: (An example location is shown below). Then use the provided script to convert
144: your sudoers file into LDIF format. The script will also convert any default
145: options.
146:
147: # SUDOERS_BASE=ou=SUDOers,dc=example,dc=com
148: # export SUDOERS_BASE
149: # ./sudoers2ldif /etc/sudoers > /tmp/sudoers.ldif
150:
151: Step 2:
152: Import into your directory server. If you are using OpenLDAP, do the following
153: if you are using another directory, provide the LDIF file to your LDAP
154: Administrator. An example is shown below.
155:
156: # ldapadd -f /tmp/sudoers.ldif -h ldapserver \
157: > -D cn=Manager,dc=example,dc=com -W -x
158:
159: Example sudoers Entries in LDAP
160: ===============================
161: The equivalent of a sudoer in LDAP is a 'sudoRole'. It contains sudoUser(s),
162: sudoHost, sudoCommand and optional sudoOption(s) and sudoRunAs(s).
163: <put an example here>
164:
165: Managing LDAP entries
166: =====================
167: Doing a one-time bulk load of your ldap entries is fine. However what if you
168: need to make minor changes on a daily basis? It doesn't make sense to delete
169: and re-add objects. (You can, but this is tedious).
170:
171: I recommend using any of the following LDAP browsers to administer your SUDOers.
172: * GQ - The gentleman's LDAP client - Open Source - I use this a lot on Linux
173: and since it is Schema aware, I don't need to create a sudoRole template.
174: http://biot.com/gq/
175:
176: * LDAP Browser/Editor - by Jarek Gawor - I use this a lot on Windows
177: and Solaris. It runs anywhere in a Java Virtual Machine including
178: web pages. You have to make a template from an existing sudoRole entry.
179: http://www.iit.edu/~gawojar/ldap
180: http://www.mcs.anl.gov/~gawor/ldap
181: http://ldapmanager.com
182:
183: There are dozens of others, some open source, some free, some not.
184:
185:
186: Configure your /etc/ldap.conf
187: =============================
188: The /etc/ldap.conf file is meant to be shared between sudo, pam_ldap, nss_ldap
189: and other ldap applications and modules. IBM Secureway unfortunately uses
190: the same filename but has a different syntax. If you need to rename where
191: this file is stored, recompile SUDO with the -DLDAP_CONFIG compile option.
192:
193: Make sure you sudoers_base matches exactly with the location you specified
194: when you imported the sudoers. Below is an example /etc/ldap.conf
195:
196: # Either specify a uri or host & port
197: #host ldapserver
198: #port 389
199: #
200: # URI will override host & port settings
201: # but only works with LDAP SDK's that support
202: # ldap_initialize() such as OpenLDAP
203: uri ldap://ldapserver
204: #uri ldaps://secureldapserver
205: #
206: # must be set or sudo will ignore LDAP
207: sudoers_base ou=SUDOers,dc=example,dc=com
208: #
209: # verbose sudoers matching from ldap
210: #sudoers_debug 2
211: #
212: # optional proxy credentials
213: #binddn <who to search as>
214: #bindpw <password>
1.2 ! millert 215: #rootbinddn <who to search as, uses /etc/ldap.passwd for bindpw>
1.1 millert 216: #
217: # LDAP Protocol Version defaults to 3
218: #ldap_version 3
219: #
220: # Define if you want to use port 389 and switch to
221: # encryption before the bind credentials are sent
222: #ssl start_tls
223: #
224: # Additional TLS options follow that allow tweaking
225: # of the SSL/TLS connection
226: #
227: #tls_checkpeer yes # verify server SSL certificate
228: #tls_checkpeer no # ignore server SSL certificate
229: #
230: # If you enable tls_checkpeer, specify either tls_cacertfile
231: # or tls_cacertdir.
232: #
233: #tls_cacertfile /etc/certs/trusted_signers.pem
234: #tls_cacertdir /etc/certs
235: #
236: # For systems that don't have /dev/random
237: # use this along with PRNGD or EGD.pl to seed the
238: # random number pool to generate cryptographic session keys.
239: #
240: #tls_randfile /etc/egd-pool
241: #
242: # You may restrict which ciphers are used. Consult your SSL
243: # documentation for which options go here.
244: #
245: #tls_ciphers <cipher-list>
246: #
247: # Sudo can provide a client certificate when communicating to
248: # the LDAP server.
249: # Tips:
250: # * Enable both lines at the same time.
251: # * Do not password protect the key file.
252: # * Ensure the keyfile is only readable by root.
253: #
254: #tls_cert /etc/certs/client_cert.pem
255: #tls_key /etc/certs/client_key.pem
256: #
257:
258: Debugging your LDAP configuration
259: =================================
260: Enable debugging if you believe sudo is not parsing LDAP the way you think it
261: it should. A value of 1 shows moderate debugging. A value of 2 shows the
262: results of the matches themselves. Make sure to set the value back to zero
263: so that other users don't get confused by the debugging messages. This value
264: is 'sudoers_debug' in the /etc/ldap.conf.
265:
266: Parsing Differences between /etc/sudoers and LDAP
267: =================================================
268: There are some subtle differences in the way sudoers is handled once in LDAP.
269: Probably the biggest is that according to the RFC, LDAP's ordering is
270: arbitrary and you cannot expect that Attributes & Entries are returned in
271: any order. If there are conflicting command rules on an entry, the negative
272: takes precedence. This is called paranoid behavior (not necessarily the
273: most specific match).
274:
275: Here is an example:
276:
277: # /etc/sudoers:
278: # Allow all commands except shell
279: johnny ALL=(root) ALL,!/bin/sh
280: # Always allows all commands because ALL is matched last
281: puddles ALL=(root) !/bin/sh,ALL
282:
283: # LDAP equivalent of Johnny
284: # Allows all commands except shell
285: dn: cn=role1,ou=Sudoers,dc=my-domain,dc=com
286: objectClass: sudoRole
287: objectClass: top
288: cn: role1
289: sudoUser: johnny
290: sudoHost: ALL
291: sudoCommand: ALL
292: sudoCommand: !/bin/sh
293:
294: # LDAP equivalent of Puddles
295: # Notice that even though ALL comes last, it still behaves like
296: # role1 since the LDAP code assumes the more paranoid configuration
297: dn: cn=role2,ou=Sudoers,dc=my-domain,dc=com
298: objectClass: sudoRole
299: objectClass: top
300: cn: role2
301: sudoUser: puddles
302: sudoHost: ALL
303: sudoCommand: !/bin/sh
304: sudoCommand: ALL
305:
1.2 ! millert 306: Another difference is that negations on the Host, User or Runas are
1.1 millert 307: currently ignorred. For example, these attributes do not work how they first
308: seem. If you desperately want this to be changed, contact Aaron Spangler
309: (aaron@spangler.ods.org).
310:
311: # does not match all but joe
312: # rather, does not match anyone
313: sudoUser: !joe
314:
315: # does not match all but joe
316: # rather, matches everyone including Joe
317: sudoUser: ALL
318: sudoUser: !joe
319:
320: # does not match all but web01
321: # rather, matches all hosts including web01
322: sudoHost: ALL
323: sudoHost: !web01
324:
325:
326: Configure your /etc/nsswitch.conf
327: =================================
328: At the time of this writing, sudo does not consult nsswitch.conf for the
329: search order. But if it did, it would look like this:
330: This might be implemented in the future. For now just skip this step.
331:
332: sudoers: files ldap
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