1 2 3 4 5 6 7 Network Working Group K. Zeilenga 8 Request for Comments: 4526 OpenLDAP Foundation 9 Category: Standards Track June 2006 10 11 12 Lightweight Directory Access Protocol (LDAP) 13 Absolute True and False Filters 14 15 Status of This Memo 16 17 This document specifies an Internet standards track protocol for the 18 Internet community, and requests discussion and suggestions for 19 improvements. Please refer to the current edition of the "Internet 20 Official Protocol Standards" (STD 1) for the standardization state 21 and status of this protocol. Distribution of this memo is unlimited. 22 23 Copyright Notice 24 25 Copyright (C) The Internet Society (2006). 26 27 Abstract 28 29 This document extends the Lightweight Directory Access Protocol 30 (LDAP) to support absolute True and False filters based upon similar 31 capabilities found in X.500 directory systems. The document also 32 extends the String Representation of LDAP Search Filters to support 33 these filters. 34 35 Table of Contents 36 37 1. Background ......................................................1 38 2. Absolute True and False Filters .................................2 39 3. Security Considerations .........................................2 40 4. IANA Considerations .............................................3 41 5. References ......................................................3 42 5.1. Normative References .......................................3 43 5.2. Informative References .....................................3 44 45 1. Background 46 47 The X.500 Directory Access Protocol (DAP) [X.511] supports absolute 48 True and False assertions. An 'and' filter with zero elements always 49 evaluates to True. An 'or' filter with zero elements always 50 evaluates to False. These filters are commonly used when requesting 51 DSA-specific Entries (DSEs) that do not necessarily have 52 'objectClass' attributes; that is, where "(objectClass=*)" may 53 evaluate to False. 54 55 56 57 58 Zeilenga Standards Track [Page 1] 59 61 RFC 4526 LDAP Absolute True and False Filters June 2006 62 63 64 Although LDAPv2 [RFC1777][RFC3494] placed no restriction on the 65 number of elements in 'and' and 'or' filter sets, the LDAPv2 string 66 representation [RFC1960][RFC3494] could not represent empty 'and' and 67 'or' filter sets. Due to this, absolute True or False filters were 68 (unfortunately) eliminated from LDAPv3 [RFC4510]. 69 70 This documents extends LDAPv3 to support absolute True and False 71 assertions by allowing empty 'and' and 'or' in Search filters 72 [RFC4511] and extends the filter string representation [RFC4515] to 73 allow empty filter lists. 74 75 It is noted that certain search operations, such as those used to 76 retrieve subschema information [RFC4512], require use of particular 77 filters. This document does not change these requirements. 78 79 This feature is intended to allow a more direct mapping between DAP 80 and LDAP (as needed to implement DAP-to-LDAP gateways). 81 82 In this document, the key words "MUST", "MUST NOT", "REQUIRED", 83 "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", 84 and "OPTIONAL" are to be interpreted as described in BCP 14 85 [RFC2119]. 86 87 2. Absolute True and False Filters 88 89 Implementations of this extension SHALL allow 'and' and 'or' choices 90 with zero filter elements. 91 92 An 'and' filter consisting of an empty set of filters SHALL evaluate 93 to True. This filter is represented by the string "(&)". 94 95 An 'or' filter consisting of an empty set of filters SHALL evaluate 96 to False. This filter is represented by the string "(|)". 97 98 Servers supporting this feature SHOULD publish the Object Identifier 99 1.3.6.1.4.1.4203.1.5.3 as a value of the 'supportedFeatures' 100 [RFC4512] attribute in the root DSE. 101 102 Clients supporting this feature SHOULD NOT use the feature unless 103 they know that the server supports it. 104 105 3. Security Considerations 106 107 The (re)introduction of absolute True and False filters is not 108 believed to raise any new security considerations. 109 110 Implementors of this (or any) LDAPv3 extension should be familiar 111 with general LDAPv3 security considerations [RFC4510]. 112 113 114 115 Zeilenga Standards Track [Page 2] 116 118 RFC 4526 LDAP Absolute True and False Filters June 2006 119 120 121 4. IANA Considerations 122 123 Registration of this feature has been completed by the IANA 124 [RFC4520]. 125 126 Subject: Request for LDAP Protocol Mechanism Registration Object 127 Identifier: 1.3.6.1.4.1.4203.1.5.3 Description: True/False filters 128 Person & email address to contact for further information: 129 Kurt Zeilenga <kurt (a] openldap.org> Usage: Feature Specification: 130 RFC 4526 Author/Change Controller: IESG Comments: none 131 132 This OID was assigned [ASSIGN] by OpenLDAP Foundation, under its 133 IANA-assigned private enterprise allocation [PRIVATE], for use in 134 this specification. 135 136 5. References 137 138 5.1. Normative References 139 140 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 141 Requirement Levels", BCP 14, RFC 2119, March 1997. 142 143 [RFC4510] Zeilenga, K., Ed, "Lightweight Directory Access 144 Protocol (LDAP): Technical Specification Road Map", RFC 145 4510, June 2006. 146 147 [RFC4511] Sermersheim, J., Ed., "Lightweight Directory Access 148 Protocol (LDAP): The Protocol", RFC 4511, June 2006. 149 150 [RFC4512] Zeilenga, K., "Lightweight Directory Access Protocol 151 (LDAP): Directory Information Models", RFC 4512, June 152 2006. 153 154 [RFC4515] Smith, M., Ed. and T. Howes, "Lightweight Directory 155 Access Protocol (LDAP): String Representation of Search 156 Filters", RFC 4515, June 2006. 157 158 5.2. Informative References 159 160 [RFC1777] Yeong, W., Howes, T., and S. Kille, "Lightweight 161 Directory Access Protocol", RFC 1777, March 1995. 162 163 [RFC1960] Howes, T., "A String Representation of LDAP Search 164 Filters", RFC 1960, June 1996. 165 166 [RFC3494] Zeilenga, K., "Lightweight Directory Access Protocol 167 version 2 (LDAPv2) to Historic Status", RFC 3494, March 168 2003. 169 170 171 172 Zeilenga Standards Track [Page 3] 173 175 RFC 4526 LDAP Absolute True and False Filters June 2006 176 177 178 [RFC4520] Zeilenga, K., "Internet Assigned Numbers Authority 179 (IANA) Considerations for the Lightweight Directory 180 Access Protocol (LDAP)", BCP 64, RFC 4520, June 2006. 181 182 [X.500] International Telecommunication Union - 183 Telecommunication Standardization Sector, "The 184 Directory -- Overview of concepts, models and 185 services," X.500(1993) (also ISO/IEC 9594-1:1994). 186 187 [X.501] International Telecommunication Union - 188 Telecommunication Standardization Sector, "The 189 Directory -- Models," X.501(1993) (also ISO/IEC 9594- 190 2:1994). 191 192 [X.511] International Telecommunication Union - 193 Telecommunication Standardization Sector, "The 194 Directory: Abstract Service Definition", X.511(1993) 195 (also ISO/IEC 9594-3:1993). 196 197 [ASSIGN] OpenLDAP Foundation, "OpenLDAP OID Delegations", 198 http://www.openldap.org/foundation/oid-delegate.txt. 199 200 [PRIVATE] IANA, "Private Enterprise Numbers", 201 http://www.iana.org/assignments/enterprise-numbers. 202 203 Author's Address 204 205 Kurt D. Zeilenga 206 OpenLDAP Foundation 207 208 EMail: Kurt (a] OpenLDAP.org 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 Zeilenga Standards Track [Page 4] 230 232 RFC 4526 LDAP Absolute True and False Filters June 2006 233 234 235 Full Copyright Statement 236 237 Copyright (C) The Internet Society (2006). 238 239 This document is subject to the rights, licenses and restrictions 240 contained in BCP 78, and except as set forth therein, the authors 241 retain all their rights. 242 243 This document and the information contained herein are provided on an 244 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 245 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 246 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 247 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 248 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 249 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 250 251 Intellectual Property 252 253 The IETF takes no position regarding the validity or scope of any 254 Intellectual Property Rights or other rights that might be claimed to 255 pertain to the implementation or use of the technology described in 256 this document or the extent to which any license under such rights 257 might or might not be available; nor does it represent that it has 258 made any independent effort to identify any such rights. Information 259 on the procedures with respect to rights in RFC documents can be 260 found in BCP 78 and BCP 79. 261 262 Copies of IPR disclosures made to the IETF Secretariat and any 263 assurances of licenses to be made available, or the result of an 264 attempt made to obtain a general license or permission for the use of 265 such proprietary rights by implementers or users of this 266 specification can be obtained from the IETF on-line IPR repository at 267 http://www.ietf.org/ipr. 268 269 The IETF invites any interested party to bring to its attention any 270 copyrights, patents or patent applications, or other proprietary 271 rights that may cover technology that may be required to implement 272 this standard. Please address the information to the IETF at 273 ietf-ipr (a] ietf.org. 274 275 Acknowledgement 276 277 Funding for the RFC Editor function is provided by the IETF 278 Administrative Support Activity (IASA). 279 280 281 282 283 284 285 286 Zeilenga Standards Track [Page 5] 287 289
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