1 ============= 1 =============
2 NFS ID Mapper 2 NFS ID Mapper
3 ============= 3 =============
4 4
5 Id mapper is used by NFS to translate user and 5 Id mapper is used by NFS to translate user and group ids into names, and to
6 translate user and group names into ids. Part 6 translate user and group names into ids. Part of this translation involves
7 performing an upcall to userspace to request t 7 performing an upcall to userspace to request the information. There are two
8 ways NFS could obtain this information: placin 8 ways NFS could obtain this information: placing a call to /sbin/request-key
9 or by placing a call to the rpc.idmap daemon. 9 or by placing a call to the rpc.idmap daemon.
10 10
11 NFS will attempt to call /sbin/request-key fir 11 NFS will attempt to call /sbin/request-key first. If this succeeds, the
12 result will be cached using the generic reques 12 result will be cached using the generic request-key cache. This call should
13 only fail if /etc/request-key.conf is not conf 13 only fail if /etc/request-key.conf is not configured for the id_resolver key
14 type, see the "Configuring" section below if y 14 type, see the "Configuring" section below if you wish to use the request-key
15 method. 15 method.
16 16
17 If the call to /sbin/request-key fails (if /et 17 If the call to /sbin/request-key fails (if /etc/request-key.conf is not
18 configured with the id_resolver key type), the 18 configured with the id_resolver key type), then the idmapper will ask the
19 legacy rpc.idmap daemon for the id mapping. T 19 legacy rpc.idmap daemon for the id mapping. This result will be stored
20 in a custom NFS idmap cache. 20 in a custom NFS idmap cache.
21 21
22 22
23 Configuring 23 Configuring
24 =========== 24 ===========
25 25
26 The file /etc/request-key.conf will need to be 26 The file /etc/request-key.conf will need to be modified so /sbin/request-key can
27 direct the upcall. The following line should 27 direct the upcall. The following line should be added:
28 28
29 ``#OP TYPE DESCRIPTION CALLOUT INFO 29 ``#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...``
30 ``#====== ======= =============== ====== 30 ``#====== ======= =============== =============== ===============================``
31 ``create id_resolver * * 31 ``create id_resolver * * /usr/sbin/nfs.idmap %k %d 600``
32 32
33 33
34 This will direct all id_resolver requests to t 34 This will direct all id_resolver requests to the program /usr/sbin/nfs.idmap.
35 The last parameter, 600, defines how many seco 35 The last parameter, 600, defines how many seconds into the future the key will
36 expire. This parameter is optional for /usr/s 36 expire. This parameter is optional for /usr/sbin/nfs.idmap. When the timeout
37 is not specified, nfs.idmap will default to 60 37 is not specified, nfs.idmap will default to 600 seconds.
38 38
39 id mapper uses for key descriptions:: 39 id mapper uses for key descriptions::
40 40
41 uid: Find the UID for the given use 41 uid: Find the UID for the given user
42 gid: Find the GID for the given gro 42 gid: Find the GID for the given group
43 user: Find the user name for the gi 43 user: Find the user name for the given UID
44 group: Find the group name for the gi 44 group: Find the group name for the given GID
45 45
46 You can handle any of these individually, rath 46 You can handle any of these individually, rather than using the generic upcall
47 program. If you would like to use your own pr 47 program. If you would like to use your own program for a uid lookup then you
48 would edit your request-key.conf so it look si 48 would edit your request-key.conf so it look similar to this:
49 49
50 ``#OP TYPE DESCRIPTION CALLOUT INFO 50 ``#OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ...``
51 ``#====== ======= =============== ====== 51 ``#====== ======= =============== =============== ===============================``
52 ``create id_resolver uid:* * 52 ``create id_resolver uid:* * /some/other/program %k %d 600``
53 ``create id_resolver * * 53 ``create id_resolver * * /usr/sbin/nfs.idmap %k %d 600``
54 54
55 55
56 Notice that the new line was added above the l 56 Notice that the new line was added above the line for the generic program.
57 request-key will find the first matching line 57 request-key will find the first matching line and corresponding program. In
58 this case, /some/other/program will handle all 58 this case, /some/other/program will handle all uid lookups and
59 /usr/sbin/nfs.idmap will handle gid, user, and 59 /usr/sbin/nfs.idmap will handle gid, user, and group lookups.
60 60
61 See Documentation/security/keys/request-key.rs 61 See Documentation/security/keys/request-key.rst for more information
62 about the request-key function. 62 about the request-key function.
63 63
64 64
65 nfs.idmap 65 nfs.idmap
66 ========= 66 =========
67 67
68 nfs.idmap is designed to be called by request- 68 nfs.idmap is designed to be called by request-key, and should not be run "by
69 hand". This program takes two arguments, a se 69 hand". This program takes two arguments, a serialized key and a key
70 description. The serialized key is first conv 70 description. The serialized key is first converted into a key_serial_t, and
71 then passed as an argument to keyctl_instantia 71 then passed as an argument to keyctl_instantiate (both are part of keyutils.h).
72 72
73 The actual lookups are performed by functions 73 The actual lookups are performed by functions found in nfsidmap.h. nfs.idmap
74 determines the correct function to call by loo 74 determines the correct function to call by looking at the first part of the
75 description string. For example, a uid lookup 75 description string. For example, a uid lookup description will appear as
76 "uid:user@domain". 76 "uid:user@domain".
77 77
78 nfs.idmap will return 0 if the key was instant 78 nfs.idmap will return 0 if the key was instantiated, and non-zero otherwise.
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