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Bryan Schumaker955a8572010-09-29 15:41:49 -04001
2=========
3ID Mapper
4=========
5Id mapper is used by NFS to translate user and group ids into names, and to
6translate user and group names into ids. Part of this translation involves
7performing an upcall to userspace to request the information. Id mapper will
8user request-key to perform this upcall and cache the result. The program
Bryan Schumakereb1c86b2010-10-26 13:27:42 -04009/usr/sbin/nfs.idmap should be called by request-key, and will perform the
Bryan Schumaker955a8572010-09-29 15:41:49 -040010translation and initialize a key with the resulting information.
11
12 NFS_USE_NEW_IDMAPPER must be selected when configuring the kernel to use this
13 feature.
14
15===========
16Configuring
17===========
18The file /etc/request-key.conf will need to be modified so /sbin/request-key can
19direct the upcall. The following line should be added:
20
21#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...
22#====== ======= =============== =============== ===============================
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040023create id_resolver * * /usr/sbin/nfs.idmap %k %d 600
Bryan Schumaker955a8572010-09-29 15:41:49 -040024
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040025This will direct all id_resolver requests to the program /usr/sbin/nfs.idmap.
Bryan Schumaker955a8572010-09-29 15:41:49 -040026The last parameter, 600, defines how many seconds into the future the key will
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040027expire. This parameter is optional for /usr/sbin/nfs.idmap. When the timeout
28is not specified, nfs.idmap will default to 600 seconds.
Bryan Schumaker955a8572010-09-29 15:41:49 -040029
30id mapper uses for key descriptions:
31 uid: Find the UID for the given user
32 gid: Find the GID for the given group
33 user: Find the user name for the given UID
34 group: Find the group name for the given GID
35
36You can handle any of these individually, rather than using the generic upcall
37program. If you would like to use your own program for a uid lookup then you
38would edit your request-key.conf so it look similar to this:
39
40#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...
41#====== ======= =============== =============== ===============================
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040042create id_resolver uid:* * /some/other/program %k %d 600
43create id_resolver * * /usr/sbin/nfs.idmap %k %d 600
Bryan Schumaker955a8572010-09-29 15:41:49 -040044
45Notice that the new line was added above the line for the generic program.
46request-key will find the first matching line and corresponding program. In
47this case, /some/other/program will handle all uid lookups and
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040048/usr/sbin/nfs.idmap will handle gid, user, and group lookups.
Bryan Schumaker955a8572010-09-29 15:41:49 -040049
50See <file:Documentation/keys-request-keys.txt> for more information about the
51request-key function.
52
53
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040054=========
55nfs.idmap
56=========
57nfs.idmap is designed to be called by request-key, and should not be run "by
Bryan Schumaker955a8572010-09-29 15:41:49 -040058hand". This program takes two arguments, a serialized key and a key
59description. The serialized key is first converted into a key_serial_t, and
60then passed as an argument to keyctl_instantiate (both are part of keyutils.h).
61
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040062The actual lookups are performed by functions found in nfsidmap.h. nfs.idmap
Bryan Schumaker955a8572010-09-29 15:41:49 -040063determines the correct function to call by looking at the first part of the
64description string. For example, a uid lookup description will appear as
65"uid:user@domain".
66
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040067nfs.idmap will return 0 if the key was instantiated, and non-zero otherwise.