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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
Bryan Schumakera602bea2012-01-26 16:54:25 -05007performing an upcall to userspace to request the information. There are two
8ways NFS could obtain this information: placing a call to /sbin/request-key
9or by placing a call to the rpc.idmap daemon.
Bryan Schumaker955a8572010-09-29 15:41:49 -040010
Bryan Schumakera602bea2012-01-26 16:54:25 -050011NFS will attempt to call /sbin/request-key first. If this succeeds, the
12result will be cached using the generic request-key cache. This call should
13only fail if /etc/request-key.conf is not configured for the id_resolver key
14type, see the "Configuring" section below if you wish to use the request-key
15method.
16
17If the call to /sbin/request-key fails (if /etc/request-key.conf is not
18configured with the id_resolver key type), then the idmapper will ask the
19legacy rpc.idmap daemon for the id mapping. This result will be stored
20in a custom NFS idmap cache.
21
Bryan Schumaker955a8572010-09-29 15:41:49 -040022
23===========
24Configuring
25===========
26The file /etc/request-key.conf will need to be modified so /sbin/request-key can
27direct the upcall. The following line should be added:
28
29#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...
30#====== ======= =============== =============== ===============================
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040031create id_resolver * * /usr/sbin/nfs.idmap %k %d 600
Bryan Schumaker955a8572010-09-29 15:41:49 -040032
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040033This will direct all id_resolver requests to the program /usr/sbin/nfs.idmap.
Bryan Schumaker955a8572010-09-29 15:41:49 -040034The last parameter, 600, defines how many seconds into the future the key will
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040035expire. This parameter is optional for /usr/sbin/nfs.idmap. When the timeout
36is not specified, nfs.idmap will default to 600 seconds.
Bryan Schumaker955a8572010-09-29 15:41:49 -040037
38id mapper uses for key descriptions:
39 uid: Find the UID for the given user
40 gid: Find the GID for the given group
41 user: Find the user name for the given UID
42 group: Find the group name for the given GID
43
44You can handle any of these individually, rather than using the generic upcall
45program. If you would like to use your own program for a uid lookup then you
46would edit your request-key.conf so it look similar to this:
47
48#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...
49#====== ======= =============== =============== ===============================
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040050create id_resolver uid:* * /some/other/program %k %d 600
51create id_resolver * * /usr/sbin/nfs.idmap %k %d 600
Bryan Schumaker955a8572010-09-29 15:41:49 -040052
53Notice that the new line was added above the line for the generic program.
54request-key will find the first matching line and corresponding program. In
55this case, /some/other/program will handle all uid lookups and
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040056/usr/sbin/nfs.idmap will handle gid, user, and group lookups.
Bryan Schumaker955a8572010-09-29 15:41:49 -040057
Paul Bolle395cf962011-08-15 02:02:26 +020058See <file:Documentation/security/keys-request-key.txt> for more information
Randy Dunlapd410fa42011-05-19 15:59:38 -070059about the request-key function.
Bryan Schumaker955a8572010-09-29 15:41:49 -040060
61
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040062=========
63nfs.idmap
64=========
65nfs.idmap is designed to be called by request-key, and should not be run "by
Bryan Schumaker955a8572010-09-29 15:41:49 -040066hand". This program takes two arguments, a serialized key and a key
67description. The serialized key is first converted into a key_serial_t, and
68then passed as an argument to keyctl_instantiate (both are part of keyutils.h).
69
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040070The actual lookups are performed by functions found in nfsidmap.h. nfs.idmap
Bryan Schumaker955a8572010-09-29 15:41:49 -040071determines the correct function to call by looking at the first part of the
72description string. For example, a uid lookup description will appear as
73"uid:user@domain".
74
Bryan Schumakereb1c86b2010-10-26 13:27:42 -040075nfs.idmap will return 0 if the key was instantiated, and non-zero otherwise.