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1 | NetLabel Linux Security Module Interface |
2 | ============================================================================== | |
3 | Paul Moore, paul.moore@hp.com | |
4 | ||
5 | May 17, 2006 | |
6 | ||
7 | * Overview | |
8 | ||
9 | NetLabel is a mechanism which can set and retrieve security attributes from | |
10 | network packets. It is intended to be used by LSM developers who want to make | |
11 | use of a common code base for several different packet labeling protocols. | |
12 | The NetLabel security module API is defined in 'include/net/netlabel.h' but a | |
13 | brief overview is given below. | |
14 | ||
15 | * NetLabel Security Attributes | |
16 | ||
17 | Since NetLabel supports multiple different packet labeling protocols and LSMs | |
18 | it uses the concept of security attributes to refer to the packet's security | |
19 | labels. The NetLabel security attributes are defined by the | |
20 | 'netlbl_lsm_secattr' structure in the NetLabel header file. Internally the | |
21 | NetLabel subsystem converts the security attributes to and from the correct | |
22 | low-level packet label depending on the NetLabel build time and run time | |
23 | configuration. It is up to the LSM developer to translate the NetLabel | |
24 | security attributes into whatever security identifiers are in use for their | |
25 | particular LSM. | |
26 | ||
27 | * NetLabel LSM Protocol Operations | |
28 | ||
29 | These are the functions which allow the LSM developer to manipulate the labels | |
30 | on outgoing packets as well as read the labels on incoming packets. Functions | |
31 | exist to operate both on sockets as well as the sk_buffs directly. These high | |
32 | level functions are translated into low level protocol operations based on how | |
33 | the administrator has configured the NetLabel subsystem. | |
34 | ||
35 | * NetLabel Label Mapping Cache Operations | |
36 | ||
37 | Depending on the exact configuration, translation between the network packet | |
38 | label and the internal LSM security identifier can be time consuming. The | |
39 | NetLabel label mapping cache is a caching mechanism which can be used to | |
40 | sidestep much of this overhead once a mapping has been established. Once the | |
a33f3224 | 41 | LSM has received a packet, used NetLabel to decode its security attributes, |
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42 | and translated the security attributes into a LSM internal identifier the LSM |
43 | can use the NetLabel caching functions to associate the LSM internal | |
44 | identifier with the network packet's label. This means that in the future | |
45 | when a incoming packet matches a cached value not only are the internal | |
46 | NetLabel translation mechanisms bypassed but the LSM translation mechanisms are | |
47 | bypassed as well which should result in a significant reduction in overhead. |