diff options
| -rw-r--r-- | Documentation/keys-request-key.txt | 54 | ||||
| -rw-r--r-- | Documentation/keys.txt | 29 | ||||
| -rw-r--r-- | include/linux/key.h | 8 | ||||
| -rw-r--r-- | security/keys/internal.h | 1 | ||||
| -rw-r--r-- | security/keys/keyctl.c | 2 | ||||
| -rw-r--r-- | security/keys/request_key.c | 44 |
6 files changed, 108 insertions, 30 deletions
diff --git a/Documentation/keys-request-key.txt b/Documentation/keys-request-key.txt index 22488d79116..c1f64fdf84c 100644 --- a/Documentation/keys-request-key.txt +++ b/Documentation/keys-request-key.txt @@ -3,16 +3,23 @@ =================== The key request service is part of the key retention service (refer to -Documentation/keys.txt). This document explains more fully how that the -requesting algorithm works. +Documentation/keys.txt). This document explains more fully how the requesting +algorithm works. The process starts by either the kernel requesting a service by calling -request_key(): +request_key*(): struct key *request_key(const struct key_type *type, const char *description, const char *callout_string); +or: + + struct key *request_key_with_auxdata(const struct key_type *type, + const char *description, + const char *callout_string, + void *aux); + Or by userspace invoking the request_key system call: key_serial_t request_key(const char *type, @@ -20,16 +27,26 @@ Or by userspace invoking the request_key system call: const char *callout_info, key_serial_t dest_keyring); -The main difference between the two access points is that the in-kernel -interface does not need to link the key to a keyring to prevent it from being -immediately destroyed. The kernel interface returns a pointer directly to the -key, and it's up to the caller to destroy the key. +The main difference between the access points is that the in-kernel interface +does not need to link the key to a keyring to prevent it from being immediately +destroyed. The kernel interface returns a pointer directly to the key, and +it's up to the caller to destroy the key. + +The request_key_with_auxdata() call is like the in-kernel request_key() call, +except that it permits auxiliary data to be passed to the upcaller (the default +is NULL). This is only useful for those key types that define their own upcall +mechanism rather than using /sbin/request-key. The userspace interface links the key to a keyring associated with the process to prevent the key from going away, and returns the serial number of the key to the caller. +The following example assumes that the key types involved don't define their +own upcall mechanisms. If they do, then those should be substituted for the +forking and execution of /sbin/request-key. + + =========== THE PROCESS =========== @@ -40,8 +57,8 @@ A request proceeds in the following manner: interface]. (2) request_key() searches the process's subscribed keyrings to see if there's - a suitable key there. If there is, it returns the key. If there isn't, and - callout_info is not set, an error is returned. Otherwise the process + a suitable key there. If there is, it returns the key. If there isn't, + and callout_info is not set, an error is returned. Otherwise the process proceeds to the next step. (3) request_key() sees that A doesn't have the desired key yet, so it creates @@ -62,7 +79,7 @@ A request proceeds in the following manner: instantiation. (7) The program may want to access another key from A's context (say a - Kerberos TGT key). It just requests the appropriate key, and the keyring + Kerberos TGT key). It just requests the appropriate key, and the keyring search notes that the session keyring has auth key V in its bottom level. This will permit it to then search the keyrings of process A with the @@ -79,10 +96,11 @@ A request proceeds in the following manner: (10) The program then exits 0 and request_key() deletes key V and returns key U to the caller. -This also extends further. If key W (step 7 above) didn't exist, key W would be -created uninstantiated, another auth key (X) would be created (as per step 3) -and another copy of /sbin/request-key spawned (as per step 4); but the context -specified by auth key X will still be process A, as it was in auth key V. +This also extends further. If key W (step 7 above) didn't exist, key W would +be created uninstantiated, another auth key (X) would be created (as per step +3) and another copy of /sbin/request-key spawned (as per step 4); but the +context specified by auth key X will still be process A, as it was in auth key +V. This is because process A's keyrings can't simply be attached to /sbin/request-key at the appropriate places because (a) execve will discard two @@ -118,17 +136,17 @@ A search of any particular keyring proceeds in the following fashion: (2) It considers all the non-keyring keys within that keyring and, if any key matches the criteria specified, calls key_permission(SEARCH) on it to see - if the key is allowed to be found. If it is, that key is returned; if + if the key is allowed to be found. If it is, that key is returned; if not, the search continues, and the error code is retained if of higher priority than the one currently set. (3) It then considers all the keyring-type keys in the keyring it's currently - searching. It calls key_permission(SEARCH) on each keyring, and if this + searching. It calls key_permission(SEARCH) on each keyring, and if this grants permission, it recurses, executing steps (2) and (3) on that keyring. The process stops immediately a valid key is found with permission granted to -use it. Any error from a previous match attempt is discarded and the key is +use it. Any error from a previous match attempt is discarded and the key is returned. When search_process_keyrings() is invoked, it performs the following searches @@ -153,7 +171,7 @@ The moment one succeeds, all pending errors are discarded and the found key is returned. Only if all these fail does the whole thing fail with the highest priority -error. Note that several errors may have come from LSM. +error. Note that several errors may have come from LSM. The error priority is: diff --git a/Documentation/keys.txt b/Documentation/keys.txt index 61c0fad2fe2..e373f021284 100644 --- a/Documentation/keys.txt +++ b/Documentation/keys.txt @@ -780,6 +780,17 @@ payload contents" for more information. See also Documentation/keys-request-key.txt. +(*) To search for a key, passing auxiliary data to the upcaller, call: + + struct key *request_key_with_auxdata(const struct key_type *type, + const char *description, + const char *callout_string, + void *aux); + + This is identical to request_key(), except that the auxiliary data is + passed to the key_type->request_key() op if it exists. + + (*) When it is no longer required, the key should be released using: void key_put(struct key *key); @@ -1031,6 +1042,24 @@ 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, + 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. + + 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"). + + 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*(). + + ============================ REQUEST-KEY CALLBACK SERVICE ============================ diff --git a/include/linux/key.h b/include/linux/key.h index e693e729bc9..169f05e4863 100644 --- a/include/linux/key.h +++ b/include/linux/key.h @@ -177,7 +177,8 @@ struct key { /* * kernel managed key type definition */ -typedef int (*request_key_actor_t)(struct key *key, struct key *authkey, const char *op); +typedef int (*request_key_actor_t)(struct key *key, struct key *authkey, + const char *op, void *aux); struct key_type { /* name of the type */ @@ -285,6 +286,11 @@ extern struct key *request_key(struct key_type *type, const char *description, const char *callout_info); +extern struct key *request_key_with_auxdata(struct key_type *type, + const char *description, + const char *callout_info, + void *aux); + extern int key_validate(struct key *key); extern key_ref_t key_create_or_update(key_ref_t keyring, diff --git a/security/keys/internal.h b/security/keys/internal.h index 3c2877f0663..1bb416f4bbc 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -99,6 +99,7 @@ extern int install_process_keyring(struct task_struct *tsk); extern struct key *request_key_and_link(struct key_type *type, const char *description, const char *callout_info, + void *aux, struct key *dest_keyring, unsigned long flags); diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 329411cf876..d9ca15c109c 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -183,7 +183,7 @@ asmlinkage long sys_request_key(const char __user *_type, } /* do the search */ - key = request_key_and_link(ktype, description, callout_info, + key = request_key_and_link(ktype, description, callout_info, NULL, key_ref_to_ptr(dest_ref), KEY_ALLOC_IN_QUOTA); if (IS_ERR(key)) { diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 58d1efd4fc2..f573ac189a0 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -1,6 +1,6 @@ /* request_key.c: request a key from userspace * - * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved. + * Copyright (C) 2004-6 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or @@ -33,7 +33,8 @@ DECLARE_WAIT_QUEUE_HEAD(request_key_conswq); */ static int call_sbin_request_key(struct key *key, struct key *authkey, - const char *op) + const char *op, + void *aux) { struct task_struct *tsk = current; key_serial_t prkey, sskey; @@ -127,6 +128,7 @@ error_alloc: static struct key *__request_key_construction(struct key_type *type, const char *description, const char *callout_info, + void *aux, unsigned long flags) { request_key_actor_t actor; @@ -164,7 +166,7 @@ static struct key *__request_key_construction(struct key_type *type, actor = call_sbin_request_key; if (type->request_key) actor = type->request_key; - ret = actor(key, authkey, "create"); + ret = actor(key, authkey, "create", aux); if (ret < 0) goto request_failed; @@ -258,8 +260,9 @@ alloc_failed: */ static struct key *request_key_construction(struct key_type *type, const char *description, - struct key_user *user, const char *callout_info, + void *aux, + struct key_user *user, unsigned long flags) { struct key_construction *pcons; @@ -284,7 +287,7 @@ static struct key *request_key_construction(struct key_type *type, } /* see about getting userspace to construct the key */ - key = __request_key_construction(type, description, callout_info, + key = __request_key_construction(type, description, callout_info, aux, flags); error: kleave(" = %p", key); @@ -392,6 +395,7 @@ static void request_key_link(struct key *key, struct key *dest_keyring) struct key *request_key_and_link(struct key_type *type, const char *description, const char *callout_info, + void *aux, struct key *dest_keyring, unsigned long flags) { @@ -399,8 +403,9 @@ struct key *request_key_and_link(struct key_type *type, struct key *key; key_ref_t key_ref; - kenter("%s,%s,%s,%p,%lx", - type->name, description, callout_info, dest_keyring, flags); + kenter("%s,%s,%s,%p,%p,%lx", + type->name, description, callout_info, aux, + dest_keyring, flags); /* search all the process keyrings for a key */ key_ref = search_process_keyrings(type, description, type->match, @@ -433,8 +438,8 @@ struct key *request_key_and_link(struct key_type *type, /* ask userspace (returns NULL if it waited on a key * being constructed) */ key = request_key_construction(type, description, - user, callout_info, - flags); + callout_info, aux, + user, flags); if (key) break; @@ -491,8 +496,27 @@ struct key *request_key(struct key_type *type, const char *callout_info) { return request_key_and_link(type, description, callout_info, NULL, - KEY_ALLOC_IN_QUOTA); + NULL, KEY_ALLOC_IN_QUOTA); } /* end request_key() */ EXPORT_SYMBOL(request_key); + +/*****************************************************************************/ +/* + * request a key with auxiliary data for the upcaller + * - search the process's keyrings + * - check the list of keys being created or updated + * - call out to userspace for a key if supplementary info was provided + */ +struct key *request_key_with_auxdata(struct key_type *type, + const char *description, + const char *callout_info, + void *aux) +{ + return request_key_and_link(type, description, callout_info, aux, + NULL, KEY_ALLOC_IN_QUOTA); + +} /* end request_key_with_auxdata() */ + +EXPORT_SYMBOL(request_key_with_auxdata); |