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1 | IETF CIPSO Working Group | ||
2 | 16 July, 1992 | ||
3 | |||
4 | |||
5 | |||
6 | COMMERCIAL IP SECURITY OPTION (CIPSO 2.2) | ||
7 | |||
8 | |||
9 | |||
10 | 1. Status | ||
11 | |||
12 | This Internet Draft provides the high level specification for a Commercial | ||
13 | IP Security Option (CIPSO). This draft reflects the version as approved by | ||
14 | the CIPSO IETF Working Group. Distribution of this memo is unlimited. | ||
15 | |||
16 | This document is an Internet Draft. Internet Drafts are working documents | ||
17 | of the Internet Engineering Task Force (IETF), its Areas, and its Working | ||
18 | Groups. Note that other groups may also distribute working documents as | ||
19 | Internet Drafts. | ||
20 | |||
21 | Internet Drafts are draft documents valid for a maximum of six months. | ||
22 | Internet Drafts may be updated, replaced, or obsoleted by other documents | ||
23 | at any time. It is not appropriate to use Internet Drafts as reference | ||
24 | material or to cite them other than as a "working draft" or "work in | ||
25 | progress." | ||
26 | |||
27 | Please check the I-D abstract listing contained in each Internet Draft | ||
28 | directory to learn the current status of this or any other Internet Draft. | ||
29 | |||
30 | |||
31 | |||
32 | |||
33 | 2. Background | ||
34 | |||
35 | Currently the Internet Protocol includes two security options. One of | ||
36 | these options is the DoD Basic Security Option (BSO) (Type 130) which allows | ||
37 | IP datagrams to be labeled with security classifications. This option | ||
38 | provides sixteen security classifications and a variable number of handling | ||
39 | restrictions. To handle additional security information, such as security | ||
40 | categories or compartments, another security option (Type 133) exists and | ||
41 | is referred to as the DoD Extended Security Option (ESO). The values for | ||
42 | the fixed fields within these two options are administered by the Defense | ||
43 | Information Systems Agency (DISA). | ||
44 | |||
45 | Computer vendors are now building commercial operating systems with | ||
46 | mandatory access controls and multi-level security. These systems are | ||
47 | no longer built specifically for a particular group in the defense or | ||
48 | intelligence communities. They are generally available commercial systems | ||
49 | for use in a variety of government and civil sector environments. | ||
50 | |||
51 | The small number of ESO format codes can not support all the possible | ||
52 | applications of a commercial security option. The BSO and ESO were | ||
53 | designed to only support the United States DoD. CIPSO has been designed | ||
54 | to support multiple security policies. This Internet Draft provides the | ||
55 | format and procedures required to support a Mandatory Access Control | ||
56 | security policy. Support for additional security policies shall be | ||
57 | defined in future RFCs. | ||
58 | |||
59 | |||
60 | |||
61 | |||
62 | Internet Draft, Expires 15 Jan 93 [PAGE 1] | ||
63 | |||
64 | |||
65 | |||
66 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
67 | |||
68 | |||
69 | |||
70 | |||
71 | 3. CIPSO Format | ||
72 | |||
73 | Option type: 134 (Class 0, Number 6, Copy on Fragmentation) | ||
74 | Option length: Variable | ||
75 | |||
76 | This option permits security related information to be passed between | ||
77 | systems within a single Domain of Interpretation (DOI). A DOI is a | ||
78 | collection of systems which agree on the meaning of particular values | ||
79 | in the security option. An authority that has been assigned a DOI | ||
80 | identifier will define a mapping between appropriate CIPSO field values | ||
81 | and their human readable equivalent. This authority will distribute that | ||
82 | mapping to hosts within the authority's domain. These mappings may be | ||
83 | sensitive, therefore a DOI authority is not required to make these | ||
84 | mappings available to anyone other than the systems that are included in | ||
85 | the DOI. | ||
86 | |||
87 | This option MUST be copied on fragmentation. This option appears at most | ||
88 | once in a datagram. All multi-octet fields in the option are defined to be | ||
89 | transmitted in network byte order. The format of this option is as follows: | ||
90 | |||
91 | +----------+----------+------//------+-----------//---------+ | ||
92 | | 10000110 | LLLLLLLL | DDDDDDDDDDDD | TTTTTTTTTTTTTTTTTTTT | | ||
93 | +----------+----------+------//------+-----------//---------+ | ||
94 | |||
95 | TYPE=134 OPTION DOMAIN OF TAGS | ||
96 | LENGTH INTERPRETATION | ||
97 | |||
98 | |||
99 | Figure 1. CIPSO Format | ||
100 | |||
101 | |||
102 | 3.1 Type | ||
103 | |||
104 | This field is 1 octet in length. Its value is 134. | ||
105 | |||
106 | |||
107 | 3.2 Length | ||
108 | |||
109 | This field is 1 octet in length. It is the total length of the option | ||
110 | including the type and length fields. With the current IP header length | ||
111 | restriction of 40 octets the value of this field MUST not exceed 40. | ||
112 | |||
113 | |||
114 | 3.3 Domain of Interpretation Identifier | ||
115 | |||
116 | This field is an unsigned 32 bit integer. The value 0 is reserved and MUST | ||
117 | not appear as the DOI identifier in any CIPSO option. Implementations | ||
118 | should assume that the DOI identifier field is not aligned on any particular | ||
119 | byte boundary. | ||
120 | |||
121 | To conserve space in the protocol, security levels and categories are | ||
122 | represented by numbers rather than their ASCII equivalent. This requires | ||
123 | a mapping table within CIPSO hosts to map these numbers to their | ||
124 | corresponding ASCII representations. Non-related groups of systems may | ||
125 | |||
126 | |||
127 | |||
128 | Internet Draft, Expires 15 Jan 93 [PAGE 2] | ||
129 | |||
130 | |||
131 | |||
132 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
133 | |||
134 | |||
135 | |||
136 | have their own unique mappings. For example, one group of systems may | ||
137 | use the number 5 to represent Unclassified while another group may use the | ||
138 | number 1 to represent that same security level. The DOI identifier is used | ||
139 | to identify which mapping was used for the values within the option. | ||
140 | |||
141 | |||
142 | 3.4 Tag Types | ||
143 | |||
144 | A common format for passing security related information is necessary | ||
145 | for interoperability. CIPSO uses sets of "tags" to contain the security | ||
146 | information relevant to the data in the IP packet. Each tag begins with | ||
147 | a tag type identifier followed by the length of the tag and ends with the | ||
148 | actual security information to be passed. All multi-octet fields in a tag | ||
149 | are defined to be transmitted in network byte order. Like the DOI | ||
150 | identifier field in the CIPSO header, implementations should assume that | ||
151 | all tags, as well as fields within a tag, are not aligned on any particular | ||
152 | octet boundary. The tag types defined in this document contain alignment | ||
153 | bytes to assist alignment of some information, however alignment can not | ||
154 | be guaranteed if CIPSO is not the first IP option. | ||
155 | |||
156 | CIPSO tag types 0 through 127 are reserved for defining standard tag | ||
157 | formats. Their definitions will be published in RFCs. Tag types whose | ||
158 | identifiers are greater than 127 are defined by the DOI authority and may | ||
159 | only be meaningful in certain Domains of Interpretation. For these tag | ||
160 | types, implementations will require the DOI identifier as well as the tag | ||
161 | number to determine the security policy and the format associated with the | ||
162 | tag. Use of tag types above 127 are restricted to closed networks where | ||
163 | interoperability with other networks will not be an issue. Implementations | ||
164 | that support a tag type greater than 127 MUST support at least one DOI that | ||
165 | requires only tag types 1 to 127. | ||
166 | |||
167 | Tag type 0 is reserved. Tag types 1, 2, and 5 are defined in this | ||
168 | Internet Draft. Types 3 and 4 are reserved for work in progress. | ||
169 | The standard format for all current and future CIPSO tags is shown below: | ||
170 | |||
171 | +----------+----------+--------//--------+ | ||
172 | | TTTTTTTT | LLLLLLLL | IIIIIIIIIIIIIIII | | ||
173 | +----------+----------+--------//--------+ | ||
174 | TAG TAG TAG | ||
175 | TYPE LENGTH INFORMATION | ||
176 | |||
177 | Figure 2: Standard Tag Format | ||
178 | |||
179 | In the three tag types described in this document, the length and count | ||
180 | restrictions are based on the current IP limitation of 40 octets for all | ||
181 | IP options. If the IP header is later expanded, then the length and count | ||
182 | restrictions specified in this document may increase to use the full area | ||
183 | provided for IP options. | ||
184 | |||
185 | |||
186 | 3.4.1 Tag Type Classes | ||
187 | |||
188 | Tag classes consist of tag types that have common processing requirements | ||
189 | and support the same security policy. The three tags defined in this | ||
190 | Internet Draft belong to the Mandatory Access Control (MAC) Sensitivity | ||
191 | |||
192 | |||
193 | |||
194 | Internet Draft, Expires 15 Jan 93 [PAGE 3] | ||
195 | |||
196 | |||
197 | |||
198 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
199 | |||
200 | |||
201 | |||
202 | class and support the MAC Sensitivity security policy. | ||
203 | |||
204 | |||
205 | 3.4.2 Tag Type 1 | ||
206 | |||
207 | This is referred to as the "bit-mapped" tag type. Tag type 1 is included | ||
208 | in the MAC Sensitivity tag type class. The format of this tag type is as | ||
209 | follows: | ||
210 | |||
211 | +----------+----------+----------+----------+--------//---------+ | ||
212 | | 00000001 | LLLLLLLL | 00000000 | LLLLLLLL | CCCCCCCCCCCCCCCCC | | ||
213 | +----------+----------+----------+----------+--------//---------+ | ||
214 | |||
215 | TAG TAG ALIGNMENT SENSITIVITY BIT MAP OF | ||
216 | TYPE LENGTH OCTET LEVEL CATEGORIES | ||
217 | |||
218 | Figure 3. Tag Type 1 Format | ||
219 | |||
220 | |||
221 | 3.4.2.1 Tag Type | ||
222 | |||
223 | This field is 1 octet in length and has a value of 1. | ||
224 | |||
225 | |||
226 | 3.4.2.2 Tag Length | ||
227 | |||
228 | This field is 1 octet in length. It is the total length of the tag type | ||
229 | including the type and length fields. With the current IP header length | ||
230 | restriction of 40 bytes the value within this field is between 4 and 34. | ||
231 | |||
232 | |||
233 | 3.4.2.3 Alignment Octet | ||
234 | |||
235 | This field is 1 octet in length and always has the value of 0. Its purpose | ||
236 | is to align the category bitmap field on an even octet boundary. This will | ||
237 | speed many implementations including router implementations. | ||
238 | |||
239 | |||
240 | 3.4.2.4 Sensitivity Level | ||
241 | |||
242 | This field is 1 octet in length. Its value is from 0 to 255. The values | ||
243 | are ordered with 0 being the minimum value and 255 representing the maximum | ||
244 | value. | ||
245 | |||
246 | |||
247 | 3.4.2.5 Bit Map of Categories | ||
248 | |||
249 | The length of this field is variable and ranges from 0 to 30 octets. This | ||
250 | provides representation of categories 0 to 239. The ordering of the bits | ||
251 | is left to right or MSB to LSB. For example category 0 is represented by | ||
252 | the most significant bit of the first byte and category 15 is represented | ||
253 | by the least significant bit of the second byte. Figure 4 graphically | ||
254 | shows this ordering. Bit N is binary 1 if category N is part of the label | ||
255 | for the datagram, and bit N is binary 0 if category N is not part of the | ||
256 | label. Except for the optimized tag 1 format described in the next section, | ||
257 | |||
258 | |||
259 | |||
260 | Internet Draft, Expires 15 Jan 93 [PAGE 4] | ||
261 | |||
262 | |||
263 | |||
264 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
265 | |||
266 | |||
267 | |||
268 | minimal encoding SHOULD be used resulting in no trailing zero octets in the | ||
269 | category bitmap. | ||
270 | |||
271 | octet 0 octet 1 octet 2 octet 3 octet 4 octet 5 | ||
272 | XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX . . . | ||
273 | bit 01234567 89111111 11112222 22222233 33333333 44444444 | ||
274 | number 012345 67890123 45678901 23456789 01234567 | ||
275 | |||
276 | Figure 4. Ordering of Bits in Tag 1 Bit Map | ||
277 | |||
278 | |||
279 | 3.4.2.6 Optimized Tag 1 Format | ||
280 | |||
281 | Routers work most efficiently when processing fixed length fields. To | ||
282 | support these routers there is an optimized form of tag type 1. The format | ||
283 | does not change. The only change is to the category bitmap which is set to | ||
284 | a constant length of 10 octets. Trailing octets required to fill out the 10 | ||
285 | octets are zero filled. Ten octets, allowing for 80 categories, was chosen | ||
286 | because it makes the total length of the CIPSO option 20 octets. If CIPSO | ||
287 | is the only option then the option will be full word aligned and additional | ||
288 | filler octets will not be required. | ||
289 | |||
290 | |||
291 | 3.4.3 Tag Type 2 | ||
292 | |||
293 | This is referred to as the "enumerated" tag type. It is used to describe | ||
294 | large but sparsely populated sets of categories. Tag type 2 is in the MAC | ||
295 | Sensitivity tag type class. The format of this tag type is as follows: | ||
296 | |||
297 | +----------+----------+----------+----------+-------------//-------------+ | ||
298 | | 00000010 | LLLLLLLL | 00000000 | LLLLLLLL | CCCCCCCCCCCCCCCCCCCCCCCCCC | | ||
299 | +----------+----------+----------+----------+-------------//-------------+ | ||
300 | |||
301 | TAG TAG ALIGNMENT SENSITIVITY ENUMERATED | ||
302 | TYPE LENGTH OCTET LEVEL CATEGORIES | ||
303 | |||
304 | Figure 5. Tag Type 2 Format | ||
305 | |||
306 | |||
307 | 3.4.3.1 Tag Type | ||
308 | |||
309 | This field is one octet in length and has a value of 2. | ||
310 | |||
311 | |||
312 | 3.4.3.2 Tag Length | ||
313 | |||
314 | This field is 1 octet in length. It is the total length of the tag type | ||
315 | including the type and length fields. With the current IP header length | ||
316 | restriction of 40 bytes the value within this field is between 4 and 34. | ||
317 | |||
318 | |||
319 | 3.4.3.3 Alignment Octet | ||
320 | |||
321 | This field is 1 octet in length and always has the value of 0. Its purpose | ||
322 | is to align the category field on an even octet boundary. This will | ||
323 | |||
324 | |||
325 | |||
326 | Internet Draft, Expires 15 Jan 93 [PAGE 5] | ||
327 | |||
328 | |||
329 | |||
330 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
331 | |||
332 | |||
333 | |||
334 | speed many implementations including router implementations. | ||
335 | |||
336 | |||
337 | 3.4.3.4 Sensitivity Level | ||
338 | |||
339 | This field is 1 octet in length. Its value is from 0 to 255. The values | ||
340 | are ordered with 0 being the minimum value and 255 representing the | ||
341 | maximum value. | ||
342 | |||
343 | |||
344 | 3.4.3.5 Enumerated Categories | ||
345 | |||
346 | In this tag, categories are represented by their actual value rather than | ||
347 | by their position within a bit field. The length of each category is 2 | ||
348 | octets. Up to 15 categories may be represented by this tag. Valid values | ||
349 | for categories are 0 to 65534. Category 65535 is not a valid category | ||
350 | value. The categories MUST be listed in ascending order within the tag. | ||
351 | |||
352 | |||
353 | 3.4.4 Tag Type 5 | ||
354 | |||
355 | This is referred to as the "range" tag type. It is used to represent | ||
356 | labels where all categories in a range, or set of ranges, are included | ||
357 | in the sensitivity label. Tag type 5 is in the MAC Sensitivity tag type | ||
358 | class. The format of this tag type is as follows: | ||
359 | |||
360 | +----------+----------+----------+----------+------------//-------------+ | ||
361 | | 00000101 | LLLLLLLL | 00000000 | LLLLLLLL | Top/Bottom | Top/Bottom | | ||
362 | +----------+----------+----------+----------+------------//-------------+ | ||
363 | |||
364 | TAG TAG ALIGNMENT SENSITIVITY CATEGORY RANGES | ||
365 | TYPE LENGTH OCTET LEVEL | ||
366 | |||
367 | Figure 6. Tag Type 5 Format | ||
368 | |||
369 | |||
370 | 3.4.4.1 Tag Type | ||
371 | |||
372 | This field is one octet in length and has a value of 5. | ||
373 | |||
374 | |||
375 | 3.4.4.2 Tag Length | ||
376 | |||
377 | This field is 1 octet in length. It is the total length of the tag type | ||
378 | including the type and length fields. With the current IP header length | ||
379 | restriction of 40 bytes the value within this field is between 4 and 34. | ||
380 | |||
381 | |||
382 | 3.4.4.3 Alignment Octet | ||
383 | |||
384 | This field is 1 octet in length and always has the value of 0. Its purpose | ||
385 | is to align the category range field on an even octet boundary. This will | ||
386 | speed many implementations including router implementations. | ||
387 | |||
388 | |||
389 | |||
390 | |||
391 | |||
392 | Internet Draft, Expires 15 Jan 93 [PAGE 6] | ||
393 | |||
394 | |||
395 | |||
396 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
397 | |||
398 | |||
399 | |||
400 | 3.4.4.4 Sensitivity Level | ||
401 | |||
402 | This field is 1 octet in length. Its value is from 0 to 255. The values | ||
403 | are ordered with 0 being the minimum value and 255 representing the maximum | ||
404 | value. | ||
405 | |||
406 | |||
407 | 3.4.4.5 Category Ranges | ||
408 | |||
409 | A category range is a 4 octet field comprised of the 2 octet index of the | ||
410 | highest numbered category followed by the 2 octet index of the lowest | ||
411 | numbered category. These range endpoints are inclusive within the range of | ||
412 | categories. All categories within a range are included in the sensitivity | ||
413 | label. This tag may contain a maximum of 7 category pairs. The bottom | ||
414 | category endpoint for the last pair in the tag MAY be omitted and SHOULD be | ||
415 | assumed to be 0. The ranges MUST be non-overlapping and be listed in | ||
416 | descending order. Valid values for categories are 0 to 65534. Category | ||
417 | 65535 is not a valid category value. | ||
418 | |||
419 | |||
420 | 3.4.5 Minimum Requirements | ||
421 | |||
422 | A CIPSO implementation MUST be capable of generating at least tag type 1 in | ||
423 | the non-optimized form. In addition, a CIPSO implementation MUST be able | ||
424 | to receive any valid tag type 1 even those using the optimized tag type 1 | ||
425 | format. | ||
426 | |||
427 | |||
428 | 4. Configuration Parameters | ||
429 | |||
430 | The configuration parameters defined below are required for all CIPSO hosts, | ||
431 | gateways, and routers that support multiple sensitivity labels. A CIPSO | ||
432 | host is defined to be the origination or destination system for an IP | ||
433 | datagram. A CIPSO gateway provides IP routing services between two or more | ||
434 | IP networks and may be required to perform label translations between | ||
435 | networks. A CIPSO gateway may be an enhanced CIPSO host or it may just | ||
436 | provide gateway services with no end system CIPSO capabilities. A CIPSO | ||
437 | router is a dedicated IP router that routes IP datagrams between two or more | ||
438 | IP networks. | ||
439 | |||
440 | An implementation of CIPSO on a host MUST have the capability to reject a | ||
441 | datagram for reasons that the information contained can not be adequately | ||
442 | protected by the receiving host or if acceptance may result in violation of | ||
443 | the host or network security policy. In addition, a CIPSO gateway or router | ||
444 | MUST be able to reject datagrams going to networks that can not provide | ||
445 | adequate protection or may violate the network's security policy. To | ||
446 | provide this capability the following minimal set of configuration | ||
447 | parameters are required for CIPSO implementations: | ||
448 | |||
449 | HOST_LABEL_MAX - This parameter contains the maximum sensitivity label that | ||
450 | a CIPSO host is authorized to handle. All datagrams that have a label | ||
451 | greater than this maximum MUST be rejected by the CIPSO host. This | ||
452 | parameter does not apply to CIPSO gateways or routers. This parameter need | ||
453 | not be defined explicitly as it can be implicitly derived from the | ||
454 | PORT_LABEL_MAX parameters for the associated interfaces. | ||
455 | |||
456 | |||
457 | |||
458 | Internet Draft, Expires 15 Jan 93 [PAGE 7] | ||
459 | |||
460 | |||
461 | |||
462 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
463 | |||
464 | |||
465 | |||
466 | |||
467 | HOST_LABEL_MIN - This parameter contains the minimum sensitivity label that | ||
468 | a CIPSO host is authorized to handle. All datagrams that have a label less | ||
469 | than this minimum MUST be rejected by the CIPSO host. This parameter does | ||
470 | not apply to CIPSO gateways or routers. This parameter need not be defined | ||
471 | explicitly as it can be implicitly derived from the PORT_LABEL_MIN | ||
472 | parameters for the associated interfaces. | ||
473 | |||
474 | PORT_LABEL_MAX - This parameter contains the maximum sensitivity label for | ||
475 | all datagrams that may exit a particular network interface port. All | ||
476 | outgoing datagrams that have a label greater than this maximum MUST be | ||
477 | rejected by the CIPSO system. The label within this parameter MUST be | ||
478 | less than or equal to the label within the HOST_LABEL_MAX parameter. This | ||
479 | parameter does not apply to CIPSO hosts that support only one network port. | ||
480 | |||
481 | PORT_LABEL_MIN - This parameter contains the minimum sensitivity label for | ||
482 | all datagrams that may exit a particular network interface port. All | ||
483 | outgoing datagrams that have a label less than this minimum MUST be | ||
484 | rejected by the CIPSO system. The label within this parameter MUST be | ||
485 | greater than or equal to the label within the HOST_LABEL_MIN parameter. | ||
486 | This parameter does not apply to CIPSO hosts that support only one network | ||
487 | port. | ||
488 | |||
489 | PORT_DOI - This parameter is used to assign a DOI identifier value to a | ||
490 | particular network interface port. All CIPSO labels within datagrams | ||
491 | going out this port MUST use the specified DOI identifier. All CIPSO | ||
492 | hosts and gateways MUST support either this parameter, the NET_DOI | ||
493 | parameter, or the HOST_DOI parameter. | ||
494 | |||
495 | NET_DOI - This parameter is used to assign a DOI identifier value to a | ||
496 | particular IP network address. All CIPSO labels within datagrams destined | ||
497 | for the particular IP network MUST use the specified DOI identifier. All | ||
498 | CIPSO hosts and gateways MUST support either this parameter, the PORT_DOI | ||
499 | parameter, or the HOST_DOI parameter. | ||
500 | |||
501 | HOST_DOI - This parameter is used to assign a DOI identifier value to a | ||
502 | particular IP host address. All CIPSO labels within datagrams destined for | ||
503 | the particular IP host will use the specified DOI identifier. All CIPSO | ||
504 | hosts and gateways MUST support either this parameter, the PORT_DOI | ||
505 | parameter, or the NET_DOI parameter. | ||
506 | |||
507 | This list represents the minimal set of configuration parameters required | ||
508 | to be compliant. Implementors are encouraged to add to this list to | ||
509 | provide enhanced functionality and control. For example, many security | ||
510 | policies may require both incoming and outgoing datagrams be checked against | ||
511 | the port and host label ranges. | ||
512 | |||
513 | |||
514 | 4.1 Port Range Parameters | ||
515 | |||
516 | The labels represented by the PORT_LABEL_MAX and PORT_LABEL_MIN parameters | ||
517 | MAY be in CIPSO or local format. Some CIPSO systems, such as routers, may | ||
518 | want to have the range parameters expressed in CIPSO format so that incoming | ||
519 | labels do not have to be converted to a local format before being compared | ||
520 | against the range. If multiple DOIs are supported by one of these CIPSO | ||
521 | |||
522 | |||
523 | |||
524 | Internet Draft, Expires 15 Jan 93 [PAGE 8] | ||
525 | |||
526 | |||
527 | |||
528 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
529 | |||
530 | |||
531 | |||
532 | systems then multiple port range parameters would be needed, one set for | ||
533 | each DOI supported on a particular port. | ||
534 | |||
535 | The port range will usually represent the total set of labels that may | ||
536 | exist on the logical network accessed through the corresponding network | ||
537 | interface. It may, however, represent a subset of these labels that are | ||
538 | allowed to enter the CIPSO system. | ||
539 | |||
540 | |||
541 | 4.2 Single Label CIPSO Hosts | ||
542 | |||
543 | CIPSO implementations that support only one label are not required to | ||
544 | support the parameters described above. These limited implementations are | ||
545 | only required to support a NET_LABEL parameter. This parameter contains | ||
546 | the CIPSO label that may be inserted in datagrams that exit the host. In | ||
547 | addition, the host MUST reject any incoming datagram that has a label which | ||
548 | is not equivalent to the NET_LABEL parameter. | ||
549 | |||
550 | |||
551 | 5. Handling Procedures | ||
552 | |||
553 | This section describes the processing requirements for incoming and | ||
554 | outgoing IP datagrams. Just providing the correct CIPSO label format | ||
555 | is not enough. Assumptions will be made by one system on how a | ||
556 | receiving system will handle the CIPSO label. Wrong assumptions may | ||
557 | lead to non-interoperability or even a security incident. The | ||
558 | requirements described below represent the minimal set needed for | ||
559 | interoperability and that provide users some level of confidence. | ||
560 | Many other requirements could be added to increase user confidence, | ||
561 | however at the risk of restricting creativity and limiting vendor | ||
562 | participation. | ||
563 | |||
564 | |||
565 | 5.1 Input Procedures | ||
566 | |||
567 | All datagrams received through a network port MUST have a security label | ||
568 | associated with them, either contained in the datagram or assigned to the | ||
569 | receiving port. Without this label the host, gateway, or router will not | ||
570 | have the information it needs to make security decisions. This security | ||
571 | label will be obtained from the CIPSO if the option is present in the | ||
572 | datagram. See section 4.1.2 for handling procedures for unlabeled | ||
573 | datagrams. This label will be compared against the PORT (if appropriate) | ||
574 | and HOST configuration parameters defined in section 3. | ||
575 | |||
576 | If any field within the CIPSO option, such as the DOI identifier, is not | ||
577 | recognized the IP datagram is discarded and an ICMP "parameter problem" | ||
578 | (type 12) is generated and returned. The ICMP code field is set to "bad | ||
579 | parameter" (code 0) and the pointer is set to the start of the CIPSO field | ||
580 | that is unrecognized. | ||
581 | |||
582 | If the contents of the CIPSO are valid but the security label is | ||
583 | outside of the configured host or port label range, the datagram is | ||
584 | discarded and an ICMP "destination unreachable" (type 3) is generated | ||
585 | and returned. The code field of the ICMP is set to "communication with | ||
586 | destination network administratively prohibited" (code 9) or to | ||
587 | |||
588 | |||
589 | |||
590 | Internet Draft, Expires 15 Jan 93 [PAGE 9] | ||
591 | |||
592 | |||
593 | |||
594 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
595 | |||
596 | |||
597 | |||
598 | "communication with destination host administratively prohibited" | ||
599 | (code 10). The value of the code field used is dependent upon whether | ||
600 | the originator of the ICMP message is acting as a CIPSO host or a CIPSO | ||
601 | gateway. The recipient of the ICMP message MUST be able to handle either | ||
602 | value. The same procedure is performed if a CIPSO can not be added to an | ||
603 | IP packet because it is too large to fit in the IP options area. | ||
604 | |||
605 | If the error is triggered by receipt of an ICMP message, the message | ||
606 | is discarded and no response is permitted (consistent with general ICMP | ||
607 | processing rules). | ||
608 | |||
609 | |||
610 | 5.1.1 Unrecognized tag types | ||
611 | |||
612 | The default condition for any CIPSO implementation is that an | ||
613 | unrecognized tag type MUST be treated as a "parameter problem" and | ||
614 | handled as described in section 4.1. A CIPSO implementation MAY allow | ||
615 | the system administrator to identify tag types that may safely be | ||
616 | ignored. This capability is an allowable enhancement, not a | ||
617 | requirement. | ||
618 | |||
619 | |||
620 | 5.1.2 Unlabeled Packets | ||
621 | |||
622 | A network port may be configured to not require a CIPSO label for all | ||
623 | incoming datagrams. For this configuration a CIPSO label must be | ||
624 | assigned to that network port and associated with all unlabeled IP | ||
625 | datagrams. This capability might be used for single level networks or | ||
626 | networks that have CIPSO and non-CIPSO hosts and the non-CIPSO hosts | ||
627 | all operate at the same label. | ||
628 | |||
629 | If a CIPSO option is required and none is found, the datagram is | ||
630 | discarded and an ICMP "parameter problem" (type 12) is generated and | ||
631 | returned to the originator of the datagram. The code field of the ICMP | ||
632 | is set to "option missing" (code 1) and the ICMP pointer is set to 134 | ||
633 | (the value of the option type for the missing CIPSO option). | ||
634 | |||
635 | |||
636 | 5.2 Output Procedures | ||
637 | |||
638 | A CIPSO option MUST appear only once in a datagram. Only one tag type | ||
639 | from the MAC Sensitivity class MAY be included in a CIPSO option. Given | ||
640 | the current set of defined tag types, this means that CIPSO labels at | ||
641 | first will contain only one tag. | ||
642 | |||
643 | All datagrams leaving a CIPSO system MUST meet the following condition: | ||
644 | |||
645 | PORT_LABEL_MIN <= CIPSO label <= PORT_LABEL_MAX | ||
646 | |||
647 | If this condition is not satisfied the datagram MUST be discarded. | ||
648 | If the CIPSO system only supports one port, the HOST_LABEL_MIN and the | ||
649 | HOST_LABEL_MAX parameters MAY be substituted for the PORT parameters in | ||
650 | the above condition. | ||
651 | |||
652 | The DOI identifier to be used for all outgoing datagrams is configured by | ||
653 | |||
654 | |||
655 | |||
656 | Internet Draft, Expires 15 Jan 93 [PAGE 10] | ||
657 | |||
658 | |||
659 | |||
660 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
661 | |||
662 | |||
663 | |||
664 | the administrator. If port level DOI identifier assignment is used, then | ||
665 | the PORT_DOI configuration parameter MUST contain the DOI identifier to | ||
666 | use. If network level DOI assignment is used, then the NET_DOI parameter | ||
667 | MUST contain the DOI identifier to use. And if host level DOI assignment | ||
668 | is employed, then the HOST_DOI parameter MUST contain the DOI identifier | ||
669 | to use. A CIPSO implementation need only support one level of DOI | ||
670 | assignment. | ||
671 | |||
672 | |||
673 | 5.3 DOI Processing Requirements | ||
674 | |||
675 | A CIPSO implementation MUST support at least one DOI and SHOULD support | ||
676 | multiple DOIs. System and network administrators are cautioned to | ||
677 | ensure that at least one DOI is common within an IP network to allow for | ||
678 | broadcasting of IP datagrams. | ||
679 | |||
680 | CIPSO gateways MUST be capable of translating a CIPSO option from one | ||
681 | DOI to another when forwarding datagrams between networks. For | ||
682 | efficiency purposes this capability is only a desired feature for CIPSO | ||
683 | routers. | ||
684 | |||
685 | |||
686 | 5.4 Label of ICMP Messages | ||
687 | |||
688 | The CIPSO label to be used on all outgoing ICMP messages MUST be equivalent | ||
689 | to the label of the datagram that caused the ICMP message. If the ICMP was | ||
690 | generated due to a problem associated with the original CIPSO label then the | ||
691 | following responses are allowed: | ||
692 | |||
693 | a. Use the CIPSO label of the original IP datagram | ||
694 | b. Drop the original datagram with no return message generated | ||
695 | |||
696 | In most cases these options will have the same effect. If you can not | ||
697 | interpret the label or if it is outside the label range of your host or | ||
698 | interface then an ICMP message with the same label will probably not be | ||
699 | able to exit the system. | ||
700 | |||
701 | |||
702 | 6. Assignment of DOI Identifier Numbers = | ||
703 | |||
704 | Requests for assignment of a DOI identifier number should be addressed to | ||
705 | the Internet Assigned Numbers Authority (IANA). | ||
706 | |||
707 | |||
708 | 7. Acknowledgements | ||
709 | |||
710 | Much of the material in this RFC is based on (and copied from) work | ||
711 | done by Gary Winiger of Sun Microsystems and published as Commercial | ||
712 | IP Security Option at the INTEROP 89, Commercial IPSO Workshop. | ||
713 | |||
714 | |||
715 | 8. Author's Address | ||
716 | |||
717 | To submit mail for distribution to members of the IETF CIPSO Working | ||
718 | Group, send mail to: cipso@wdl1.wdl.loral.com. | ||
719 | |||
720 | |||
721 | |||
722 | Internet Draft, Expires 15 Jan 93 [PAGE 11] | ||
723 | |||
724 | |||
725 | |||
726 | CIPSO INTERNET DRAFT 16 July, 1992 | ||
727 | |||
728 | |||
729 | |||
730 | |||
731 | To be added to or deleted from this distribution, send mail to: | ||
732 | cipso-request@wdl1.wdl.loral.com. | ||
733 | |||
734 | |||
735 | 9. References | ||
736 | |||
737 | RFC 1038, "Draft Revised IP Security Option", M. St. Johns, IETF, January | ||
738 | 1988. | ||
739 | |||
740 | RFC 1108, "U.S. Department of Defense Security Options | ||
741 | for the Internet Protocol", Stephen Kent, IAB, 1 March, 1991. | ||
742 | |||
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