// 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);