diff options
Diffstat (limited to 'security/keys/request_key.c')
| -rw-r--r-- | security/keys/request_key.c | 713 |
1 files changed, 713 insertions, 0 deletions
diff --git a/security/keys/request_key.c b/security/keys/request_key.c new file mode 100644 index 00000000..82465328 --- /dev/null +++ b/security/keys/request_key.c @@ -0,0 +1,713 @@ +/* Request a key from userspace + * + * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + * + * See Documentation/security/keys-request-key.txt + */ + +#include <linux/module.h> +#include <linux/sched.h> +#include <linux/kmod.h> +#include <linux/err.h> +#include <linux/keyctl.h> +#include <linux/slab.h> +#include "internal.h" + +#define key_negative_timeout 60 /* default timeout on a negative key's existence */ + +/* + * wait_on_bit() sleep function for uninterruptible waiting + */ +static int key_wait_bit(void *flags) +{ + schedule(); + return 0; +} + +/* + * wait_on_bit() sleep function for interruptible waiting + */ +static int key_wait_bit_intr(void *flags) +{ + schedule(); + return signal_pending(current) ? -ERESTARTSYS : 0; +} + +/** + * complete_request_key - Complete the construction of a key. + * @cons: The key construction record. + * @error: The success or failute of the construction. + * + * Complete the attempt to construct a key. The key will be negated + * if an error is indicated. The authorisation key will be revoked + * unconditionally. + */ +void complete_request_key(struct key_construction *cons, int error) +{ + kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error); + + if (error < 0) + key_negate_and_link(cons->key, key_negative_timeout, NULL, + cons->authkey); + else + key_revoke(cons->authkey); + + key_put(cons->key); + key_put(cons->authkey); + kfree(cons); +} +EXPORT_SYMBOL(complete_request_key); + +/* + * Initialise a usermode helper that is going to have a specific session + * keyring. + * + * This is called in context of freshly forked kthread before kernel_execve(), + * so we can simply install the desired session_keyring at this point. + */ +static int umh_keys_init(struct subprocess_info *info, struct cred *cred) +{ + struct key *keyring = info->data; + + return install_session_keyring_to_cred(cred, keyring); +} + +/* + * Clean up a usermode helper with session keyring. + */ +static void umh_keys_cleanup(struct subprocess_info *info) +{ + struct key *keyring = info->data; + key_put(keyring); +} + +/* + * Call a usermode helper with a specific session keyring. + */ +static int call_usermodehelper_keys(char *path, char **argv, char **envp, + struct key *session_keyring, enum umh_wait wait) +{ + gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL; + struct subprocess_info *info = + call_usermodehelper_setup(path, argv, envp, gfp_mask); + + if (!info) + return -ENOMEM; + + call_usermodehelper_setfns(info, umh_keys_init, umh_keys_cleanup, + key_get(session_keyring)); + return call_usermodehelper_exec(info, wait); +} + +/* + * Request userspace finish the construction of a key + * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>" + */ +static int call_sbin_request_key(struct key_construction *cons, + const char *op, + void *aux) +{ + const struct cred *cred = current_cred(); + key_serial_t prkey, sskey; + struct key *key = cons->key, *authkey = cons->authkey, *keyring, + *session; + char *argv[9], *envp[3], uid_str[12], gid_str[12]; + char key_str[12], keyring_str[3][12]; + char desc[20]; + int ret, i; + + kenter("{%d},{%d},%s", key->serial, authkey->serial, op); + + ret = install_user_keyrings(); + if (ret < 0) + goto error_alloc; + + /* allocate a new session keyring */ + sprintf(desc, "_req.%u", key->serial); + + cred = get_current_cred(); + keyring = keyring_alloc(desc, cred->fsuid, cred->fsgid, cred, + KEY_ALLOC_QUOTA_OVERRUN, NULL); + put_cred(cred); + if (IS_ERR(keyring)) { + ret = PTR_ERR(keyring); + goto error_alloc; + } + + /* attach the auth key to the session keyring */ + ret = key_link(keyring, authkey); + if (ret < 0) + goto error_link; + + /* record the UID and GID */ + sprintf(uid_str, "%d", cred->fsuid); + sprintf(gid_str, "%d", cred->fsgid); + + /* we say which key is under construction */ + sprintf(key_str, "%d", key->serial); + + /* we specify the process's default keyrings */ + sprintf(keyring_str[0], "%d", + cred->thread_keyring ? cred->thread_keyring->serial : 0); + + prkey = 0; + if (cred->tgcred->process_keyring) + prkey = cred->tgcred->process_keyring->serial; + sprintf(keyring_str[1], "%d", prkey); + + rcu_read_lock(); + session = rcu_dereference(cred->tgcred->session_keyring); + if (!session) + session = cred->user->session_keyring; + sskey = session->serial; + rcu_read_unlock(); + + sprintf(keyring_str[2], "%d", sskey); + + /* set up a minimal environment */ + i = 0; + envp[i++] = "HOME=/"; + envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin"; + envp[i] = NULL; + + /* set up the argument list */ + i = 0; + argv[i++] = "/sbin/request-key"; + argv[i++] = (char *) op; + argv[i++] = key_str; + argv[i++] = uid_str; + argv[i++] = gid_str; + argv[i++] = keyring_str[0]; + argv[i++] = keyring_str[1]; + argv[i++] = keyring_str[2]; + argv[i] = NULL; + + /* do it */ + ret = call_usermodehelper_keys(argv[0], argv, envp, keyring, + UMH_WAIT_PROC); + kdebug("usermode -> 0x%x", ret); + if (ret >= 0) { + /* ret is the exit/wait code */ + if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) || + key_validate(key) < 0) + ret = -ENOKEY; + else + /* ignore any errors from userspace if the key was + * instantiated */ + ret = 0; + } + +error_link: + key_put(keyring); + +error_alloc: + complete_request_key(cons, ret); + kleave(" = %d", ret); + return ret; +} + +/* + * Call out to userspace for key construction. + * + * Program failure is ignored in favour of key status. + */ +static int construct_key(struct key *key, const void *callout_info, + size_t callout_len, void *aux, + struct key *dest_keyring) +{ + struct key_construction *cons; + request_key_actor_t actor; + struct key *authkey; + int ret; + + kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux); + + cons = kmalloc(sizeof(*cons), GFP_KERNEL); + if (!cons) + return -ENOMEM; + + /* allocate an authorisation key */ + authkey = request_key_auth_new(key, callout_info, callout_len, + dest_keyring); + if (IS_ERR(authkey)) { + kfree(cons); + ret = PTR_ERR(authkey); + authkey = NULL; + } else { + cons->authkey = key_get(authkey); + cons->key = key_get(key); + + /* make the call */ + actor = call_sbin_request_key; + if (key->type->request_key) + actor = key->type->request_key; + + ret = actor(cons, "create", aux); + + /* check that the actor called complete_request_key() prior to + * returning an error */ + WARN_ON(ret < 0 && + !test_bit(KEY_FLAG_REVOKED, &authkey->flags)); + key_put(authkey); + } + + kleave(" = %d", ret); + return ret; +} + +/* + * Get the appropriate destination keyring for the request. + * + * The keyring selected is returned with an extra reference upon it which the + * caller must release. + */ +static void construct_get_dest_keyring(struct key **_dest_keyring) +{ + struct request_key_auth *rka; + const struct cred *cred = current_cred(); + struct key *dest_keyring = *_dest_keyring, *authkey; + + kenter("%p", dest_keyring); + + /* find the appropriate keyring */ + if (dest_keyring) { + /* the caller supplied one */ + key_get(dest_keyring); + } else { + /* use a default keyring; falling through the cases until we + * find one that we actually have */ + switch (cred->jit_keyring) { + case KEY_REQKEY_DEFL_DEFAULT: + case KEY_REQKEY_DEFL_REQUESTOR_KEYRING: + if (cred->request_key_auth) { + authkey = cred->request_key_auth; + down_read(&authkey->sem); + rka = authkey->payload.data; + if (!test_bit(KEY_FLAG_REVOKED, + &authkey->flags)) + dest_keyring = + key_get(rka->dest_keyring); + up_read(&authkey->sem); + if (dest_keyring) + break; + } + + case KEY_REQKEY_DEFL_THREAD_KEYRING: + dest_keyring = key_get(cred->thread_keyring); + if (dest_keyring) + break; + + case KEY_REQKEY_DEFL_PROCESS_KEYRING: + dest_keyring = key_get(cred->tgcred->process_keyring); + if (dest_keyring) + break; + + case KEY_REQKEY_DEFL_SESSION_KEYRING: + rcu_read_lock(); + dest_keyring = key_get( + rcu_dereference(cred->tgcred->session_keyring)); + rcu_read_unlock(); + + if (dest_keyring) + break; + + case KEY_REQKEY_DEFL_USER_SESSION_KEYRING: + dest_keyring = + key_get(cred->user->session_keyring); + break; + + case KEY_REQKEY_DEFL_USER_KEYRING: + dest_keyring = key_get(cred->user->uid_keyring); + break; + + case KEY_REQKEY_DEFL_GROUP_KEYRING: + default: + BUG(); + } + } + + *_dest_keyring = dest_keyring; + kleave(" [dk %d]", key_serial(dest_keyring)); + return; +} + +/* + * Allocate a new key in under-construction state and attempt to link it in to + * the requested keyring. + * + * May return a key that's already under construction instead if there was a + * race between two thread calling request_key(). + */ +static int construct_alloc_key(struct key_type *type, + const char *description, + struct key *dest_keyring, + unsigned long flags, + struct key_user *user, + struct key **_key) +{ + const struct cred *cred = current_cred(); + unsigned long prealloc; + struct key *key; + key_ref_t key_ref; + int ret; + + kenter("%s,%s,,,", type->name, description); + + *_key = NULL; + mutex_lock(&user->cons_lock); + + key = key_alloc(type, description, cred->fsuid, cred->fsgid, cred, + KEY_POS_ALL, flags); + if (IS_ERR(key)) + goto alloc_failed; + + set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags); + + if (dest_keyring) { + ret = __key_link_begin(dest_keyring, type, description, + &prealloc); + if (ret < 0) + goto link_prealloc_failed; + } + + /* attach the key to the destination keyring under lock, but we do need + * to do another check just in case someone beat us to it whilst we + * waited for locks */ + mutex_lock(&key_construction_mutex); + + key_ref = search_process_keyrings(type, description, type->match, cred); + if (!IS_ERR(key_ref)) + goto key_already_present; + + if (dest_keyring) + __key_link(dest_keyring, key, &prealloc); + + mutex_unlock(&key_construction_mutex); + if (dest_keyring) + __key_link_end(dest_keyring, type, prealloc); + mutex_unlock(&user->cons_lock); + *_key = key; + kleave(" = 0 [%d]", key_serial(key)); + return 0; + + /* the key is now present - we tell the caller that we found it by + * returning -EINPROGRESS */ +key_already_present: + key_put(key); + mutex_unlock(&key_construction_mutex); + key = key_ref_to_ptr(key_ref); + if (dest_keyring) { + ret = __key_link_check_live_key(dest_keyring, key); + if (ret == 0) + __key_link(dest_keyring, key, &prealloc); + __key_link_end(dest_keyring, type, prealloc); + if (ret < 0) + goto link_check_failed; + } + mutex_unlock(&user->cons_lock); + *_key = key; + kleave(" = -EINPROGRESS [%d]", key_serial(key)); + return -EINPROGRESS; + +link_check_failed: + mutex_unlock(&user->cons_lock); + key_put(key); + kleave(" = %d [linkcheck]", ret); + return ret; + +link_prealloc_failed: + mutex_unlock(&user->cons_lock); + kleave(" = %d [prelink]", ret); + return ret; + +alloc_failed: + mutex_unlock(&user->cons_lock); + kleave(" = %ld", PTR_ERR(key)); + return PTR_ERR(key); +} + +/* + * Commence key construction. + */ +static struct key *construct_key_and_link(struct key_type *type, + const char *description, + const char *callout_info, + size_t callout_len, + void *aux, + struct key *dest_keyring, + unsigned long flags) +{ + struct key_user *user; + struct key *key; + int ret; + + kenter(""); + + user = key_user_lookup(current_fsuid(), current_user_ns()); + if (!user) + return ERR_PTR(-ENOMEM); + + construct_get_dest_keyring(&dest_keyring); + + ret = construct_alloc_key(type, description, dest_keyring, flags, user, + &key); + key_user_put(user); + + if (ret == 0) { + ret = construct_key(key, callout_info, callout_len, aux, + dest_keyring); + if (ret < 0) { + kdebug("cons failed"); + goto construction_failed; + } + } else if (ret == -EINPROGRESS) { + ret = 0; + } else { + goto couldnt_alloc_key; + } + + key_put(dest_keyring); + kleave(" = key %d", key_serial(key)); + return key; + +construction_failed: + key_negate_and_link(key, key_negative_timeout, NULL, NULL); + key_put(key); +couldnt_alloc_key: + key_put(dest_keyring); + kleave(" = %d", ret); + return ERR_PTR(ret); +} + +/** + * request_key_and_link - Request a key and cache it in a keyring. + * @type: The type of key we want. + * @description: The searchable description of the key. + * @callout_info: The data to pass to the instantiation upcall (or NULL). + * @callout_len: The length of callout_info. + * @aux: Auxiliary data for the upcall. + * @dest_keyring: Where to cache the key. + * @flags: Flags to key_alloc(). + * + * A key matching the specified criteria is searched for in the process's + * keyrings and returned with its usage count incremented if found. Otherwise, + * if callout_info is not NULL, a key will be allocated and some service + * (probably in userspace) will be asked to instantiate it. + * + * If successfully found or created, the key will be linked to the destination + * keyring if one is provided. + * + * Returns a pointer to the key if successful; -EACCES, -ENOKEY, -EKEYREVOKED + * or -EKEYEXPIRED if an inaccessible, negative, revoked or expired key was + * found; -ENOKEY if no key was found and no @callout_info was given; -EDQUOT + * if insufficient key quota was available to create a new key; or -ENOMEM if + * insufficient memory was available. + * + * If the returned key was created, then it may still be under construction, + * and wait_for_key_construction() should be used to wait for that to complete. + */ +struct key *request_key_and_link(struct key_type *type, + const char *description, + const void *callout_info, + size_t callout_len, + void *aux, + struct key *dest_keyring, + unsigned long flags) +{ + const struct cred *cred = current_cred(); + struct key *key; + key_ref_t key_ref; + int ret; + + kenter("%s,%s,%p,%zu,%p,%p,%lx", + type->name, description, callout_info, callout_len, aux, + dest_keyring, flags); + + /* search all the process keyrings for a key */ + key_ref = search_process_keyrings(type, description, type->match, cred); + + if (!IS_ERR(key_ref)) { + key = key_ref_to_ptr(key_ref); + if (dest_keyring) { + construct_get_dest_keyring(&dest_keyring); + ret = key_link(dest_keyring, key); + key_put(dest_keyring); + if (ret < 0) { + key_put(key); + key = ERR_PTR(ret); + goto error; + } + } + } else if (PTR_ERR(key_ref) != -EAGAIN) { + key = ERR_CAST(key_ref); + } else { + /* the search failed, but the keyrings were searchable, so we + * should consult userspace if we can */ + key = ERR_PTR(-ENOKEY); + if (!callout_info) + goto error; + + key = construct_key_and_link(type, description, callout_info, + callout_len, aux, dest_keyring, + flags); + } + +error: + kleave(" = %p", key); + return key; +} + +/** + * wait_for_key_construction - Wait for construction of a key to complete + * @key: The key being waited for. + * @intr: Whether to wait interruptibly. + * + * Wait for a key to finish being constructed. + * + * Returns 0 if successful; -ERESTARTSYS if the wait was interrupted; -ENOKEY + * if the key was negated; or -EKEYREVOKED or -EKEYEXPIRED if the key was + * revoked or expired. + */ +int wait_for_key_construction(struct key *key, bool intr) +{ + int ret; + + ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT, + intr ? key_wait_bit_intr : key_wait_bit, + intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE); + if (ret < 0) + return ret; + if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) + return key->type_data.reject_error; + return key_validate(key); +} +EXPORT_SYMBOL(wait_for_key_construction); + +/** + * request_key - Request a key and wait for construction + * @type: Type of key. + * @description: The searchable description of the key. + * @callout_info: The data to pass to the instantiation upcall (or NULL). + * + * As for request_key_and_link() except that it does not add the returned key + * to a keyring if found, new keys are always allocated in the user's quota, + * the callout_info must be a NUL-terminated string and no auxiliary data can + * be passed. + * + * Furthermore, it then works as wait_for_key_construction() to wait for the + * completion of keys undergoing construction with a non-interruptible wait. + */ +struct key *request_key(struct key_type *type, + const char *description, + const char *callout_info) +{ + struct key *key; + size_t callout_len = 0; + int ret; + + if (callout_info) + callout_len = strlen(callout_info); + key = request_key_and_link(type, description, callout_info, callout_len, + NULL, NULL, KEY_ALLOC_IN_QUOTA); + if (!IS_ERR(key)) { + ret = wait_for_key_construction(key, false); + if (ret < 0) { + key_put(key); + return ERR_PTR(ret); + } + } + return key; +} +EXPORT_SYMBOL(request_key); + +/** + * request_key_with_auxdata - Request a key with auxiliary data for the upcaller + * @type: The type of key we want. + * @description: The searchable description of the key. + * @callout_info: The data to pass to the instantiation upcall (or NULL). + * @callout_len: The length of callout_info. + * @aux: Auxiliary data for the upcall. + * + * As for request_key_and_link() except that it does not add the returned key + * to a keyring if found and new keys are always allocated in the user's quota. + * + * Furthermore, it then works as wait_for_key_construction() to wait for the + * completion of keys undergoing construction with a non-interruptible wait. + */ +struct key *request_key_with_auxdata(struct key_type *type, + const char *description, + const void *callout_info, + size_t callout_len, + void *aux) +{ + struct key *key; + int ret; + + key = request_key_and_link(type, description, callout_info, callout_len, + aux, NULL, KEY_ALLOC_IN_QUOTA); + if (!IS_ERR(key)) { + ret = wait_for_key_construction(key, false); + if (ret < 0) { + key_put(key); + return ERR_PTR(ret); + } + } + return key; +} +EXPORT_SYMBOL(request_key_with_auxdata); + +/* + * request_key_async - Request a key (allow async construction) + * @type: Type of key. + * @description: The searchable description of the key. + * @callout_info: The data to pass to the instantiation upcall (or NULL). + * @callout_len: The length of callout_info. + * + * As for request_key_and_link() except that it does not add the returned key + * to a keyring if found, new keys are always allocated in the user's quota and + * no auxiliary data can be passed. + * + * The caller should call wait_for_key_construction() to wait for the + * completion of the returned key if it is still undergoing construction. + */ +struct key *request_key_async(struct key_type *type, + const char *description, + const void *callout_info, + size_t callout_len) +{ + return request_key_and_link(type, description, callout_info, + callout_len, NULL, NULL, + KEY_ALLOC_IN_QUOTA); +} +EXPORT_SYMBOL(request_key_async); + +/* + * request a key with auxiliary data for the upcaller (allow async construction) + * @type: Type of key. + * @description: The searchable description of the key. + * @callout_info: The data to pass to the instantiation upcall (or NULL). + * @callout_len: The length of callout_info. + * @aux: Auxiliary data for the upcall. + * + * As for request_key_and_link() except that it does not add the returned key + * to a keyring if found and new keys are always allocated in the user's quota. + * + * The caller should call wait_for_key_construction() to wait for the + * completion of the returned key if it is still undergoing construction. + */ +struct key *request_key_async_with_auxdata(struct key_type *type, + const char *description, + const void *callout_info, + size_t callout_len, + void *aux) +{ + return request_key_and_link(type, description, callout_info, + callout_len, aux, NULL, KEY_ALLOC_IN_QUOTA); +} +EXPORT_SYMBOL(request_key_async_with_auxdata); |