diff options
Diffstat (limited to 'security/keys/request_key.c')
| -rw-r--r-- | security/keys/request_key.c | 821 |
1 files changed, 821 insertions, 0 deletions
diff --git a/security/keys/request_key.c b/security/keys/request_key.c new file mode 100644 index 000000000..a7673ad86 --- /dev/null +++ b/security/keys/request_key.c @@ -0,0 +1,821 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Request a key from userspace + * + * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * See Documentation/security/keys/request-key.rst + */ + +#include <linux/export.h> +#include <linux/sched.h> +#include <linux/kmod.h> +#include <linux/err.h> +#include <linux/keyctl.h> +#include <linux/slab.h> +#include <net/net_namespace.h> +#include "internal.h" +#include <keys/request_key_auth-type.h> + +#define key_negative_timeout 60 /* default timeout on a negative key's existence */ + +static struct key *check_cached_key(struct keyring_search_context *ctx) +{ +#ifdef CONFIG_KEYS_REQUEST_CACHE + struct key *key = current->cached_requested_key; + + if (key && + ctx->match_data.cmp(key, &ctx->match_data) && + !(key->flags & ((1 << KEY_FLAG_INVALIDATED) | + (1 << KEY_FLAG_REVOKED)))) + return key_get(key); +#endif + return NULL; +} + +static void cache_requested_key(struct key *key) +{ +#ifdef CONFIG_KEYS_REQUEST_CACHE + struct task_struct *t = current; + + /* Do not cache key if it is a kernel thread */ + if (!(t->flags & PF_KTHREAD)) { + key_put(t->cached_requested_key); + t->cached_requested_key = key_get(key); + set_tsk_thread_flag(t, TIF_NOTIFY_RESUME); + } +#endif +} + +/** + * complete_request_key - Complete the construction of a key. + * @authkey: The authorisation key. + * @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 *authkey, int error) +{ + struct request_key_auth *rka = get_request_key_auth(authkey); + struct key *key = rka->target_key; + + kenter("%d{%d},%d", authkey->serial, key->serial, error); + + if (error < 0) + key_negate_and_link(key, key_negative_timeout, NULL, authkey); + else + key_revoke(authkey); +} +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(const char *path, char **argv, char **envp, + struct key *session_keyring, int wait) +{ + struct subprocess_info *info; + + info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL, + umh_keys_init, umh_keys_cleanup, + session_keyring); + if (!info) + return -ENOMEM; + + 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 *authkey, void *aux) +{ + static char const request_key[] = "/sbin/request-key"; + struct request_key_auth *rka = get_request_key_auth(authkey); + const struct cred *cred = current_cred(); + key_serial_t prkey, sskey; + struct key *key = rka->target_key, *keyring, *session, *user_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, rka->op); + + ret = look_up_user_keyrings(NULL, &user_session); + if (ret < 0) + goto error_us; + + /* 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_POS_ALL | KEY_USR_VIEW | KEY_USR_READ, + KEY_ALLOC_QUOTA_OVERRUN, NULL, 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", from_kuid(&init_user_ns, cred->fsuid)); + sprintf(gid_str, "%d", from_kgid(&init_user_ns, 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->process_keyring) + prkey = cred->process_keyring->serial; + sprintf(keyring_str[1], "%d", prkey); + + session = cred->session_keyring; + if (!session) + session = user_session; + sskey = session->serial; + + 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++] = (char *)request_key; + argv[i++] = (char *)rka->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(request_key, 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: + key_put(user_session); +error_us: + complete_request_key(authkey, 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) +{ + request_key_actor_t actor; + struct key *authkey; + int ret; + + kenter("%d,%p,%zu,%p", key->serial, callout_info, callout_len, aux); + + /* allocate an authorisation key */ + authkey = request_key_auth_new(key, "create", callout_info, callout_len, + dest_keyring); + if (IS_ERR(authkey)) + return PTR_ERR(authkey); + + /* Make the call */ + actor = call_sbin_request_key; + if (key->type->request_key) + actor = key->type->request_key; + + ret = actor(authkey, aux); + + /* check that the actor called complete_request_key() prior to + * returning an error */ + WARN_ON(ret < 0 && + !test_bit(KEY_FLAG_INVALIDATED, &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 int 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; + int ret; + + kenter("%p", dest_keyring); + + /* find the appropriate keyring */ + if (dest_keyring) { + /* the caller supplied one */ + key_get(dest_keyring); + } else { + bool do_perm_check = true; + + /* 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 = get_request_key_auth(authkey); + if (!test_bit(KEY_FLAG_REVOKED, + &authkey->flags)) + dest_keyring = + key_get(rka->dest_keyring); + up_read(&authkey->sem); + if (dest_keyring) { + do_perm_check = false; + break; + } + } + + fallthrough; + case KEY_REQKEY_DEFL_THREAD_KEYRING: + dest_keyring = key_get(cred->thread_keyring); + if (dest_keyring) + break; + + fallthrough; + case KEY_REQKEY_DEFL_PROCESS_KEYRING: + dest_keyring = key_get(cred->process_keyring); + if (dest_keyring) + break; + + fallthrough; + case KEY_REQKEY_DEFL_SESSION_KEYRING: + dest_keyring = key_get(cred->session_keyring); + + if (dest_keyring) + break; + + fallthrough; + case KEY_REQKEY_DEFL_USER_SESSION_KEYRING: + ret = look_up_user_keyrings(NULL, &dest_keyring); + if (ret < 0) + return ret; + break; + + case KEY_REQKEY_DEFL_USER_KEYRING: + ret = look_up_user_keyrings(&dest_keyring, NULL); + if (ret < 0) + return ret; + break; + + case KEY_REQKEY_DEFL_GROUP_KEYRING: + default: + BUG(); + } + + /* + * Require Write permission on the keyring. This is essential + * because the default keyring may be the session keyring, and + * joining a keyring only requires Search permission. + * + * However, this check is skipped for the "requestor keyring" so + * that /sbin/request-key can itself use request_key() to add + * keys to the original requestor's destination keyring. + */ + if (dest_keyring && do_perm_check) { + ret = key_permission(make_key_ref(dest_keyring, 1), + KEY_NEED_WRITE); + if (ret) { + key_put(dest_keyring); + return ret; + } + } + } + + *_dest_keyring = dest_keyring; + kleave(" [dk %d]", key_serial(dest_keyring)); + return 0; +} + +/* + * 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 keyring_search_context *ctx, + struct key *dest_keyring, + unsigned long flags, + struct key_user *user, + struct key **_key) +{ + struct assoc_array_edit *edit = NULL; + struct key *key; + key_perm_t perm; + key_ref_t key_ref; + int ret; + + kenter("%s,%s,,,", + ctx->index_key.type->name, ctx->index_key.description); + + *_key = NULL; + mutex_lock(&user->cons_lock); + + perm = KEY_POS_VIEW | KEY_POS_SEARCH | KEY_POS_LINK | KEY_POS_SETATTR; + perm |= KEY_USR_VIEW; + if (ctx->index_key.type->read) + perm |= KEY_POS_READ; + if (ctx->index_key.type == &key_type_keyring || + ctx->index_key.type->update) + perm |= KEY_POS_WRITE; + + key = key_alloc(ctx->index_key.type, ctx->index_key.description, + ctx->cred->fsuid, ctx->cred->fsgid, ctx->cred, + perm, flags, NULL); + if (IS_ERR(key)) + goto alloc_failed; + + set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags); + + if (dest_keyring) { + ret = __key_link_lock(dest_keyring, &key->index_key); + if (ret < 0) + goto link_lock_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. + * + * The caller might specify a comparison function which looks for keys + * that do not exactly match but are still equivalent from the caller's + * perspective. The __key_link_begin() operation must be done only after + * an actual key is determined. + */ + mutex_lock(&key_construction_mutex); + + rcu_read_lock(); + key_ref = search_process_keyrings_rcu(ctx); + rcu_read_unlock(); + if (!IS_ERR(key_ref)) + goto key_already_present; + + if (dest_keyring) { + ret = __key_link_begin(dest_keyring, &key->index_key, &edit); + if (ret < 0) + goto link_alloc_failed; + __key_link(dest_keyring, key, &edit); + } + + mutex_unlock(&key_construction_mutex); + if (dest_keyring) + __key_link_end(dest_keyring, &key->index_key, edit); + 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_begin(dest_keyring, &key->index_key, &edit); + if (ret < 0) + goto link_alloc_failed_unlocked; + ret = __key_link_check_live_key(dest_keyring, key); + if (ret == 0) + __key_link(dest_keyring, key, &edit); + __key_link_end(dest_keyring, &key->index_key, edit); + 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_alloc_failed: + mutex_unlock(&key_construction_mutex); +link_alloc_failed_unlocked: + __key_link_end(dest_keyring, &key->index_key, edit); +link_lock_failed: + mutex_unlock(&user->cons_lock); + key_put(key); + 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 keyring_search_context *ctx, + 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(""); + + if (ctx->index_key.type == &key_type_keyring) + return ERR_PTR(-EPERM); + + ret = construct_get_dest_keyring(&dest_keyring); + if (ret) + goto error; + + user = key_user_lookup(current_fsuid()); + if (!user) { + ret = -ENOMEM; + goto error_put_dest_keyring; + } + + ret = construct_alloc_key(ctx, 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 error_put_dest_keyring; + } + + 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); +error_put_dest_keyring: + key_put(dest_keyring); +error: + 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. + * @domain_tag: The domain in which the key operates. + * @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 (type, description, domain_tag) 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, + struct key_tag *domain_tag, + const void *callout_info, + size_t callout_len, + void *aux, + struct key *dest_keyring, + unsigned long flags) +{ + struct keyring_search_context ctx = { + .index_key.type = type, + .index_key.domain_tag = domain_tag, + .index_key.description = description, + .index_key.desc_len = strlen(description), + .cred = current_cred(), + .match_data.cmp = key_default_cmp, + .match_data.raw_data = description, + .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, + .flags = (KEYRING_SEARCH_DO_STATE_CHECK | + KEYRING_SEARCH_SKIP_EXPIRED | + KEYRING_SEARCH_RECURSE), + }; + struct key *key; + key_ref_t key_ref; + int ret; + + kenter("%s,%s,%p,%zu,%p,%p,%lx", + ctx.index_key.type->name, ctx.index_key.description, + callout_info, callout_len, aux, dest_keyring, flags); + + if (type->match_preparse) { + ret = type->match_preparse(&ctx.match_data); + if (ret < 0) { + key = ERR_PTR(ret); + goto error; + } + } + + key = check_cached_key(&ctx); + if (key) + goto error_free; + + /* search all the process keyrings for a key */ + rcu_read_lock(); + key_ref = search_process_keyrings_rcu(&ctx); + rcu_read_unlock(); + + if (!IS_ERR(key_ref)) { + if (dest_keyring) { + ret = key_task_permission(key_ref, current_cred(), + KEY_NEED_LINK); + if (ret < 0) { + key_ref_put(key_ref); + key = ERR_PTR(ret); + goto error_free; + } + } + + key = key_ref_to_ptr(key_ref); + if (dest_keyring) { + ret = key_link(dest_keyring, key); + if (ret < 0) { + key_put(key); + key = ERR_PTR(ret); + goto error_free; + } + } + + /* Only cache the key on immediate success */ + cache_requested_key(key); + } 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_free; + + key = construct_key_and_link(&ctx, callout_info, callout_len, + aux, dest_keyring, flags); + } + +error_free: + if (type->match_free) + type->match_free(&ctx.match_data); +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 ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE); + if (ret) + return -ERESTARTSYS; + ret = key_read_state(key); + if (ret < 0) + return ret; + return key_validate(key); +} +EXPORT_SYMBOL(wait_for_key_construction); + +/** + * request_key_tag - Request a key and wait for construction + * @type: Type of key. + * @description: The searchable description of the key. + * @domain_tag: The domain in which the key operates. + * @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_tag(struct key_type *type, + const char *description, + struct key_tag *domain_tag, + 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, domain_tag, + 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_tag); + +/** + * 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. + * @domain_tag: The domain in which the key operates. + * @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, + struct key_tag *domain_tag, + const void *callout_info, + size_t callout_len, + void *aux) +{ + struct key *key; + int ret; + + key = request_key_and_link(type, description, domain_tag, + 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_rcu - Request key from RCU-read-locked context + * @type: The type of key we want. + * @description: The name of the key we want. + * @domain_tag: The domain in which the key operates. + * + * Request a key from a context that we may not sleep in (such as RCU-mode + * pathwalk). Keys under construction are ignored. + * + * Return a pointer to the found key if successful, -ENOKEY if we couldn't find + * a key or some other error if the key found was unsuitable or inaccessible. + */ +struct key *request_key_rcu(struct key_type *type, + const char *description, + struct key_tag *domain_tag) +{ + struct keyring_search_context ctx = { + .index_key.type = type, + .index_key.domain_tag = domain_tag, + .index_key.description = description, + .index_key.desc_len = strlen(description), + .cred = current_cred(), + .match_data.cmp = key_default_cmp, + .match_data.raw_data = description, + .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, + .flags = (KEYRING_SEARCH_DO_STATE_CHECK | + KEYRING_SEARCH_SKIP_EXPIRED), + }; + struct key *key; + key_ref_t key_ref; + + kenter("%s,%s", type->name, description); + + key = check_cached_key(&ctx); + if (key) + return key; + + /* search all the process keyrings for a key */ + key_ref = search_process_keyrings_rcu(&ctx); + if (IS_ERR(key_ref)) { + key = ERR_CAST(key_ref); + if (PTR_ERR(key_ref) == -EAGAIN) + key = ERR_PTR(-ENOKEY); + } else { + key = key_ref_to_ptr(key_ref); + cache_requested_key(key); + } + + kleave(" = %p", key); + return key; +} +EXPORT_SYMBOL(request_key_rcu); |