diff options
Diffstat (limited to 'Documentation/keys.txt')
| -rw-r--r-- | Documentation/keys.txt | 93 |
1 files changed, 79 insertions, 14 deletions
diff --git a/Documentation/keys.txt b/Documentation/keys.txt index 947d57d5345..51652d39e61 100644 --- a/Documentation/keys.txt +++ b/Documentation/keys.txt @@ -4,7 +4,7 @@ This service allows cryptographic keys, authentication tokens, cross-domain user mappings, and similar to be cached in the kernel for the use of -filesystems other kernel services. +filesystems and other kernel services. Keyrings are permitted; these are a special type of key that can hold links to other keys. Processes each have three standard keyring subscriptions that a @@ -726,6 +726,15 @@ 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. +To access the key manager, the following header must be #included: + + <linux/key.h> + +Specific key types should have a header file under include/keys/ that should be +used to access that type. For keys of type "user", for example, that would be: + + <keys/user-type.h> + Note that there are two different types of pointers to keys that may be encountered: @@ -791,6 +800,36 @@ payload contents" for more information. passed to the key_type->request_key() op if it exists. +(*) A key can be requested asynchronously by calling one of: + + struct key *request_key_async(const struct key_type *type, + const char *description, + const char *callout_string); + + or: + + struct key *request_key_async_with_auxdata(const struct key_type *type, + const char *description, + const char *callout_string, + void *aux); + + which are asynchronous equivalents of request_key() and + request_key_with_auxdata() respectively. + + These two functions return with the key potentially still under + construction. To wait for contruction completion, the following should be + called: + + int wait_for_key_construction(struct key *key, bool intr); + + The function will wait for the key to finish being constructed and then + invokes key_validate() to return an appropriate value to indicate the state + of the key (0 indicates the key is usable). + + If intr is true, then the wait can be interrupted by a signal, in which + case error ERESTARTSYS will be returned. + + (*) When it is no longer required, the key should be released using: void key_put(struct key *key); @@ -924,7 +963,11 @@ DEFINING A KEY TYPE A kernel service may want to define its own key type. For instance, an AFS filesystem might want to define a Kerberos 5 ticket key type. To do this, it -author fills in a struct key_type and registers it with the system. +author fills in a key_type struct and registers it with the system. + +Source files that implement key types should include the following header file: + + <linux/key-type.h> The structure has a number of fields, some of which are mandatory: @@ -1053,22 +1096,44 @@ The structure has a number of fields, some of which are mandatory: as might happen when the userspace buffer is accessed. - (*) int (*request_key)(struct key *key, struct key *authkey, const char *op, + (*) int (*request_key)(struct key_construction *cons, const char *op, void *aux); - This method is optional. If provided, request_key() and - request_key_with_auxdata() will invoke this function rather than - upcalling to /sbin/request-key to operate upon a key of this type. + This method is optional. If provided, request_key() and friends will + invoke this function rather than upcalling to /sbin/request-key to operate + upon a key of this type. + + The aux parameter is as passed to request_key_async_with_auxdata() and + similar or is NULL otherwise. Also passed are the construction record for + the key to be operated upon and the operation type (currently only + "create"). + + This method is permitted to return before the upcall is complete, but the + following function must be called under all circumstances to complete the + instantiation process, whether or not it succeeds, whether or not there's + an error: + + void complete_request_key(struct key_construction *cons, int error); + + The error parameter should be 0 on success, -ve on error. The + construction record is destroyed by this action and the authorisation key + will be revoked. If an error is indicated, the key under construction + will be negatively instantiated if it wasn't already instantiated. + + If this method returns an error, that error will be returned to the + caller of request_key*(). complete_request_key() must be called prior to + returning. + + The key under construction and the authorisation key can be found in the + key_construction struct pointed to by cons: + + (*) struct key *key; + + The key under construction. - The aux parameter is as passed to request_key_with_auxdata() or is NULL - otherwise. Also passed are the key to be operated upon, the - authorisation key for this operation and the operation type (currently - only "create"). + (*) struct key *authkey; - This function should return only when the upcall is complete. Upon return - the authorisation key will be revoked, and the target key will be - negatively instantiated if it is still uninstantiated. The error will be - returned to the caller of request_key*(). + The authorisation key. ============================ |