projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 955a857e BS |
1 | |
| 2 | ========= | |
| 3 | ID Mapper | |
| 4 | ========= | |
| 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 of this translation involves | |
| 7 | performing an upcall to userspace to request the information. Id mapper will | |
| 8 | user request-key to perform this upcall and cache the result. The program | |
| eb1c86b8 | 9 | /usr/sbin/nfs.idmap should be called by request-key, and will perform the |
| 955a857e BS |
10 | translation 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 | =========== | |
| 16 | Configuring | |
| 17 | =========== | |
| 18 | The file /etc/request-key.conf will need to be modified so /sbin/request-key can | |
| 19 | direct the upcall. The following line should be added: | |
| 20 | ||
| 21 | #OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ... | |
| 22 | #====== ======= =============== =============== =============================== | |
| eb1c86b8 | 23 | create id_resolver * * /usr/sbin/nfs.idmap %k %d 600 |
| 955a857e | 24 | |
| eb1c86b8 | 25 | This will direct all id_resolver requests to the program /usr/sbin/nfs.idmap. |
| 955a857e | 26 | The last parameter, 600, defines how many seconds into the future the key will |
| eb1c86b8 BS |
27 | expire. This parameter is optional for /usr/sbin/nfs.idmap. When the timeout |
| 28 | is not specified, nfs.idmap will default to 600 seconds. | |
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29 | |
| 30 | id 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 | ||
| 36 | You can handle any of these individually, rather than using the generic upcall | |
| 37 | program. If you would like to use your own program for a uid lookup then you | |
| 38 | would edit your request-key.conf so it look similar to this: | |
| 39 | ||
| 40 | #OP TYPE DESCRIPTION CALLOUT INFO PROGRAM ARG1 ARG2 ARG3 ... | |
| 41 | #====== ======= =============== =============== =============================== | |
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42 | create id_resolver uid:* * /some/other/program %k %d 600 |
| 43 | create id_resolver * * /usr/sbin/nfs.idmap %k %d 600 | |
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44 | |
| 45 | Notice that the new line was added above the line for the generic program. | |
| 46 | request-key will find the first matching line and corresponding program. In | |
| 47 | this case, /some/other/program will handle all uid lookups and | |
| eb1c86b8 | 48 | /usr/sbin/nfs.idmap will handle gid, user, and group lookups. |
| 955a857e | 49 | |
| d410fa4e RD |
50 | See <file:Documentation/security/keys-request-keys.txt> for more information |
| 51 | about the request-key function. | |
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52 | |
| 53 | ||
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54 | ========= |
| 55 | nfs.idmap | |
| 56 | ========= | |
| 57 | nfs.idmap is designed to be called by request-key, and should not be run "by | |
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58 | hand". This program takes two arguments, a serialized key and a key |
| 59 | description. The serialized key is first converted into a key_serial_t, and | |
| 60 | then passed as an argument to keyctl_instantiate (both are part of keyutils.h). | |
| 61 | ||
| eb1c86b8 | 62 | The actual lookups are performed by functions found in nfsidmap.h. nfs.idmap |
| 955a857e BS |
63 | determines the correct function to call by looking at the first part of the |
| 64 | description string. For example, a uid lookup description will appear as | |
| 65 | "uid:user@domain". | |
| 66 | ||
| eb1c86b8 | 67 | nfs.idmap will return 0 if the key was instantiated, and non-zero otherwise. |