diff options
Diffstat (limited to 'Documentation/keys.txt')
| -rw-r--r-- | Documentation/keys.txt | 92 |
1 files changed, 66 insertions, 26 deletions
diff --git a/Documentation/keys.txt b/Documentation/keys.txt index 0321ded4b9ae..4afe03a58c5b 100644 --- a/Documentation/keys.txt +++ b/Documentation/keys.txt @@ -195,8 +195,8 @@ KEY ACCESS PERMISSIONS ====================== Keys have an owner user ID, a group access ID, and a permissions mask. The mask -has up to eight bits each for user, group and other access. Only five of each -set of eight bits are defined. These permissions granted are: +has up to eight bits each for possessor, user, group and other access. Only +five of each set of eight bits are defined. These permissions granted are: (*) View @@ -241,16 +241,16 @@ about the status of the key service: type, description and permissions. The payload of the key is not available this way: - SERIAL FLAGS USAGE EXPY PERM UID GID TYPE DESCRIPTION: SUMMARY - 00000001 I----- 39 perm 1f0000 0 0 keyring _uid_ses.0: 1/4 - 00000002 I----- 2 perm 1f0000 0 0 keyring _uid.0: empty - 00000007 I----- 1 perm 1f0000 0 0 keyring _pid.1: empty - 0000018d I----- 1 perm 1f0000 0 0 keyring _pid.412: empty - 000004d2 I--Q-- 1 perm 1f0000 32 -1 keyring _uid.32: 1/4 - 000004d3 I--Q-- 3 perm 1f0000 32 -1 keyring _uid_ses.32: empty - 00000892 I--QU- 1 perm 1f0000 0 0 user metal:copper: 0 - 00000893 I--Q-N 1 35s 1f0000 0 0 user metal:silver: 0 - 00000894 I--Q-- 1 10h 1f0000 0 0 user metal:gold: 0 + SERIAL FLAGS USAGE EXPY PERM UID GID TYPE DESCRIPTION: SUMMARY + 00000001 I----- 39 perm 1f1f0000 0 0 keyring _uid_ses.0: 1/4 + 00000002 I----- 2 perm 1f1f0000 0 0 keyring _uid.0: empty + 00000007 I----- 1 perm 1f1f0000 0 0 keyring _pid.1: empty + 0000018d I----- 1 perm 1f1f0000 0 0 keyring _pid.412: empty + 000004d2 I--Q-- 1 perm 1f1f0000 32 -1 keyring _uid.32: 1/4 + 000004d3 I--Q-- 3 perm 1f1f0000 32 -1 keyring _uid_ses.32: empty + 00000892 I--QU- 1 perm 1f000000 0 0 user metal:copper: 0 + 00000893 I--Q-N 1 35s 1f1f0000 0 0 user metal:silver: 0 + 00000894 I--Q-- 1 10h 001f0000 0 0 user metal:gold: 0 The flags are: @@ -361,6 +361,8 @@ The main syscalls are: /sbin/request-key will be invoked in an attempt to obtain a key. The callout_info string will be passed as an argument to the program. + See also Documentation/keys-request-key.txt. + The keyctl syscall functions are: @@ -533,8 +535,8 @@ The keyctl syscall functions are: (*) Read the payload data from a key: - key_serial_t keyctl(KEYCTL_READ, key_serial_t keyring, char *buffer, - size_t buflen); + long keyctl(KEYCTL_READ, key_serial_t keyring, char *buffer, + size_t buflen); This function attempts to read the payload data from the specified key into the buffer. The process must have read permission on the key to @@ -555,9 +557,9 @@ The keyctl syscall functions are: (*) Instantiate a partially constructed key. - key_serial_t keyctl(KEYCTL_INSTANTIATE, key_serial_t key, - const void *payload, size_t plen, - key_serial_t keyring); + long keyctl(KEYCTL_INSTANTIATE, key_serial_t key, + const void *payload, size_t plen, + key_serial_t keyring); If the kernel calls back to userspace to complete the instantiation of a key, userspace should use this call to supply data for the key before the @@ -576,8 +578,8 @@ The keyctl syscall functions are: (*) Negatively instantiate a partially constructed key. - key_serial_t keyctl(KEYCTL_NEGATE, key_serial_t key, - unsigned timeout, key_serial_t keyring); + long keyctl(KEYCTL_NEGATE, key_serial_t key, + unsigned timeout, key_serial_t keyring); If the kernel calls back to userspace to complete the instantiation of a key, userspace should use this call mark the key as negative before the @@ -637,6 +639,34 @@ call, and the key released upon close. How to deal with conflicting keys due to two different users opening the same file is left to the filesystem author to solve. +Note that there are two different types of pointers to keys that may be +encountered: + + (*) struct key * + + This simply points to the key structure itself. Key structures will be at + least four-byte aligned. + + (*) key_ref_t + + This is equivalent to a struct key *, but the least significant bit is set + if the caller "possesses" the key. By "possession" it is meant that the + calling processes has a searchable link to the key from one of its + keyrings. There are three functions for dealing with these: + + key_ref_t make_key_ref(const struct key *key, + unsigned long possession); + + struct key *key_ref_to_ptr(const key_ref_t key_ref); + + unsigned long is_key_possessed(const key_ref_t key_ref); + + The first function constructs a key reference from a key pointer and + possession information (which must be 0 or 1 and not any other value). + + The second function retrieves the key pointer from a reference and the + third retrieves the possession flag. + When accessing a key's payload contents, certain precautions must be taken to prevent access vs modification races. See the section "Notes on accessing payload contents" for more information. @@ -660,12 +690,18 @@ payload contents" for more information. If successful, the key will have been attached to the default keyring for implicitly obtained request-key keys, as set by KEYCTL_SET_REQKEY_KEYRING. + See also Documentation/keys-request-key.txt. + (*) When it is no longer required, the key should be released using: void key_put(struct key *key); - This can be called from interrupt context. If CONFIG_KEYS is not set then + Or: + + void key_ref_put(key_ref_t key_ref); + + These can be called from interrupt context. If CONFIG_KEYS is not set then the argument will not be parsed. @@ -689,13 +725,17 @@ payload contents" for more information. (*) If a keyring was found in the search, this can be further searched by: - struct key *keyring_search(struct key *keyring, - const struct key_type *type, - const char *description) + key_ref_t keyring_search(key_ref_t keyring_ref, + const struct key_type *type, + const char *description) This searches the keyring tree specified for a matching key. Error ENOKEY - is returned upon failure. If successful, the returned key will need to be - released. + is returned upon failure (use IS_ERR/PTR_ERR to determine). If successful, + the returned key will need to be released. + + The possession attribute from the keyring reference is used to control + access through the permissions mask and is propagated to the returned key + reference pointer if successful. (*) To check the validity of a key, this function can be called: @@ -732,7 +772,7 @@ More complex payload contents must be allocated and a pointer to them set in key->payload.data. One of the following ways must be selected to access the data: - (1) Unmodifyable key type. + (1) Unmodifiable key type. If the key type does not have a modify method, then the key's payload can be accessed without any form of locking, provided that it's known to be |