/* Management of a process's keyrings * * Copyright (C) 2004-2005, 2008 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. */ #include <linux/module.h> #include <linux/init.h> #include <linux/sched.h> #include <linux/slab.h> #include <linux/keyctl.h> #include <linux/fs.h> #include <linux/err.h> #include <linux/mutex.h> #include <asm/uaccess.h> #include "internal.h" /* session keyring create vs join semaphore */ static DEFINE_MUTEX(key_session_mutex); /* user keyring creation semaphore */ static DEFINE_MUTEX(key_user_keyring_mutex); /* the root user's tracking struct */ struct key_user root_key_user = { .usage = ATOMIC_INIT(3), .cons_lock = __MUTEX_INITIALIZER(root_key_user.cons_lock), .lock = __SPIN_LOCK_UNLOCKED(root_key_user.lock), .nkeys = ATOMIC_INIT(2), .nikeys = ATOMIC_INIT(2), .uid = 0, }; /*****************************************************************************/ /* * install user and user session keyrings for a particular UID */ int install_user_keyrings(void) { struct user_struct *user; const struct cred *cred; struct key *uid_keyring, *session_keyring; char buf[20]; int ret; cred = current_cred(); user = cred->user; kenter("%p{%u}", user, user->uid); if (user->uid_keyring) { kleave(" = 0 [exist]"); return 0; } mutex_lock(&key_user_keyring_mutex); ret = 0; if (!user->uid_keyring) { /* get the UID-specific keyring * - there may be one in existence already as it may have been * pinned by a session, but the user_struct pointing to it * may have been destroyed by setuid */ sprintf(buf, "_uid.%u", user->uid); uid_keyring = find_keyring_by_name(buf, true); if (IS_ERR(uid_keyring)) { uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, cred, KEY_ALLOC_IN_QUOTA, NULL); if (IS_ERR(uid_keyring)) { ret = PTR_ERR(uid_keyring); goto error; } } /* get a default session keyring (which might also exist * already) */ sprintf(buf, "_uid_ses.%u", user->uid); session_keyring = find_keyring_by_name(buf, true); if (IS_ERR(session_keyring)) { session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, cred, KEY_ALLOC_IN_QUOTA, NULL); if (IS_ERR(session_keyring)) { ret = PTR_ERR(session_keyring); goto error_release; } /* we install a link from the user session keyring to * the user keyring */ ret = key_link(session_keyring, uid_keyring); if (ret < 0) goto error_release_both; } /* install the keyrings */ user->uid_keyring = uid_keyring; user->session_keyring = session_keyring; } mutex_unlock(&key_user_keyring_mutex); kleave(" = 0"); return 0; error_release_both: key_put(session_keyring); error_release: key_put(uid_keyring); error: mutex_unlock(&key_user_keyring_mutex); kleave(" = %d", ret); return ret; } /* * install a fresh thread keyring directly to new credentials */ int install_thread_keyring_to_cred(struct cred *new) { struct key *keyring; keyring = keyring_alloc("_tid", new->uid, new->gid, new, KEY_ALLOC_QUOTA_OVERRUN, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); new->thread_keyring = keyring; return 0; } /* * install a fresh thread keyring, discarding the old one */ static int install_thread_keyring(void) { struct cred *new; int ret; new = prepare_creds(); if (!new) return -ENOMEM; BUG_ON(new->thread_keyring); ret = install_thread_keyring_to_cred(new); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); } /* * install a process keyring directly to a credentials struct * - returns -EEXIST if there was already a process keyring, 0 if one installed, * and other -ve on any other error */ int install_process_keyring_to_cred(struct cred *new) { struct key *keyring; int ret; if (new->tgcred->process_keyring) return -EEXIST; keyring = keyring_alloc("_pid", new->uid, new->gid, new, KEY_ALLOC_QUOTA_OVERRUN, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); spin_lock_irq(&new->tgcred->lock); if (!new->tgcred->process_keyring) { new->tgcred->process_keyring = keyring; keyring = NULL; ret = 0; } else { ret = -EEXIST; } spin_unlock_irq(&new->tgcred->lock); key_put(keyring); return ret; } /* * make sure a process keyring is installed * - we */ static int install_process_keyring(void) { struct cred *new; int ret; new = prepare_creds(); if (!new) return -ENOMEM; ret = install_process_keyring_to_cred(new); if (ret < 0) { abort_creds(new); return ret != -EEXIST ?: 0; } return commit_creds(new); } /* * install a session keyring directly to a credentials struct */ static int install_session_keyring_to_cred(struct cred *cred, struct key *keyring) { unsigned long flags; struct key *old; might_sleep(); /* create an empty session keyring */ if (!keyring) { flags = KEY_ALLOC_QUOTA_OVERRUN; if (cred->tgcred->session_keyring) flags = KEY_ALLOC_IN_QUOTA; keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred, flags, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); } else { atomic_inc(&keyring->usage); } /* install the keyring */ spin_lock_irq(&cred->tgcred->lock); old = cred->tgcred->session_keyring; rcu_assign_pointer(cred->tgcred->session_keyring, keyring); spin_unlock_irq(&cred->tgcred->lock); /* we're using RCU on the pointer, but there's no point synchronising * on it if it didn't previously point to anything */ if (old) { synchronize_rcu(); key_put(old); } return 0; } /* * install a session keyring, discarding the old one * - if a keyring is not supplied, an empty one is invented */ static int install_session_keyring(struct key *keyring) { struct cred *new; int ret; new = prepare_creds(); if (!new) return -ENOMEM; ret = install_session_keyring_to_cred(new, NULL); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); } /*****************************************************************************/ /* * the filesystem user ID changed */ void key_fsuid_changed(struct task_struct *tsk) { /* update the ownership of the thread keyring */ BUG_ON(!tsk->cred); if (tsk->cred->thread_keyring) { down_write(&tsk->cred->thread_keyring->sem); tsk->cred->thread_keyring->uid = tsk->cred->fsuid; up_write(&tsk->cred->thread_keyring->sem); } } /* end key_fsuid_changed() */ /*****************************************************************************/ /* * the filesystem group ID changed */ void key_fsgid_changed(struct task_struct *tsk) { /* update the ownership of the thread keyring */ BUG_ON(!tsk->cred); if (tsk->cred->thread_keyring) { down_write(&tsk->cred->thread_keyring->sem); tsk->cred->thread_keyring->gid = tsk->cred->fsgid; up_write(&tsk->cred->thread_keyring->sem); } } /* end key_fsgid_changed() */ /*****************************************************************************/ /* * search the process keyrings for the first matching key * - we use the supplied match function to see if the description (or other * feature of interest) matches * - we return -EAGAIN if we didn't find any matching key * - we return -ENOKEY if we found only negative matching keys */ key_ref_t search_process_keyrings(struct key_type *type, const void *description, key_match_func_t match, const struct cred *cred) { struct request_key_auth *rka; key_ref_t key_ref, ret, err; might_sleep(); /* we want to return -EAGAIN or -ENOKEY if any of the keyrings were * searchable, but we failed to find a key or we found a negative key; * otherwise we want to return a sample error (probably -EACCES) if * none of the keyrings were searchable * * in terms of priority: success > -ENOKEY > -EAGAIN > other error */ key_ref = NULL; ret = NULL; err = ERR_PTR(-EAGAIN); /* search the thread keyring first */ if (cred->thread_keyring) { key_ref = keyring_search_aux( make_key_ref(cred->thread_keyring, 1), cred, type, description, match); if (!IS_ERR(key_ref)) goto found; switch (PTR_ERR(key_ref)) { case -EAGAIN: /* no key */ if (ret) break; case -ENOKEY: /* negative key */ ret = key_ref; break; default: err = key_ref; break; } } /* search the process keyring second */ if (cred->tgcred->process_keyring) { key_ref = keyring_search_aux( make_key_ref(cred->tgcred->process_keyring, 1), cred, type, description, match); if (!IS_ERR(key_ref)) goto found; switch (PTR_ERR(key_ref)) { case -EAGAIN: /* no key */ if (ret) break; case -ENOKEY: /* negative key */ ret = key_ref; break; default: err = key_ref; break; } } /* search the session keyring */ if (cred->tgcred->session_keyring) { rcu_read_lock(); key_ref = keyring_search_aux( make_key_ref(rcu_dereference( cred->tgcred->session_keyring), 1), cred, type, description, match); rcu_read_unlock(); if (!IS_ERR(key_ref)) goto found; switch (PTR_ERR(key_ref)) { case -EAGAIN: /* no key */ if (ret) break; case -ENOKEY: /* negative key */ ret = key_ref; break; default: err = key_ref; break; } } /* or search the user-session keyring */ else if (cred->user->session_keyring) { key_ref = keyring_search_aux( make_key_ref(cred->user->session_keyring, 1), cred, type, description, match); if (!IS_ERR(key_ref)) goto found; switch (PTR_ERR(key_ref)) { case -EAGAIN: /* no key */ if (ret) break; case -ENOKEY: /* negative key */ ret = key_ref; break; default: err = key_ref; break; } } /* if this process has an instantiation authorisation key, then we also * search the keyrings of the process mentioned there * - we don't permit access to request_key auth keys via this method */ if (cred->request_key_auth && cred == current_cred() && type != &key_type_request_key_auth ) { /* defend against the auth key being revoked */ down_read(&cred->request_key_auth->sem); if (key_validate(cred->request_key_auth) == 0) { rka = cred->request_key_auth->payload.data; key_ref = search_process_keyrings(type, description, match, rka->cred); up_read(&cred->request_key_auth->sem); if (!IS_ERR(key_ref)) goto found; switch (PTR_ERR(key_ref)) { case -EAGAIN: /* no key */ if (ret) break; case -ENOKEY: /* negative key */ ret = key_ref; break; default: err = key_ref; break; } } else { up_read(&cred->request_key_auth->sem); } } /* no key - decide on the error we're going to go for */ key_ref = ret ? ret : err; found: return key_ref; } /* end search_process_keyrings() */ /*****************************************************************************/ /* * see if the key we're looking at is the target key */ static int lookup_user_key_possessed(const struct key *key, const void *target) { return key == target; } /* end lookup_user_key_possessed() */ /*****************************************************************************/ /* * lookup a key given a key ID from userspace with a given permissions mask * - don't create special keyrings unless so requested * - partially constructed keys aren't found unless requested */ key_ref_t lookup_user_key(key_serial_t id, int create, int partial, key_perm_t perm) { struct request_key_auth *rka; const struct cred *cred; struct key *key; key_ref_t key_ref, skey_ref; int ret; try_again: cred = get_current_cred(); key_ref = ERR_PTR(-ENOKEY); switch (id) { case KEY_SPEC_THREAD_KEYRING: if (!cred->thread_keyring) { if (!create) goto error; ret = install_thread_keyring(); if (ret < 0) { key = ERR_PTR(ret); goto error; } goto reget_creds; } key = cred->thread_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_PROCESS_KEYRING: if (!cred->tgcred->process_keyring) { if (!create) goto error; ret = install_process_keyring(); if (ret < 0) { key = ERR_PTR(ret); goto error; } goto reget_creds; } key = cred->tgcred->process_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_SESSION_KEYRING: if (!cred->tgcred->session_keyring) { /* always install a session keyring upon access if one * doesn't exist yet */ ret = install_user_keyrings(); if (ret < 0) goto error; ret = install_session_keyring( cred->user->session_keyring); if (ret < 0) goto error; goto reget_creds; } rcu_read_lock(); key = rcu_dereference(cred->tgcred->session_keyring); atomic_inc(&key->usage); rcu_read_unlock(); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_USER_KEYRING: if (!cred->user->uid_keyring) { ret = install_user_keyrings(); if (ret < 0) goto error; } key = cred->user->uid_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_USER_SESSION_KEYRING: if (!cred->user->session_keyring) { ret = install_user_keyrings(); if (ret < 0) goto error; } key = cred->user->session_keyring; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_GROUP_KEYRING: /* group keyrings are not yet supported */ key = ERR_PTR(-EINVAL); goto error; case KEY_SPEC_REQKEY_AUTH_KEY: key = cred->request_key_auth; if (!key) goto error; atomic_inc(&key->usage); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_REQUESTOR_KEYRING: if (!cred->request_key_auth) goto error; down_read(&cred->request_key_auth->sem); if (cred->request_key_auth->flags & KEY_FLAG_REVOKED) { key_ref = ERR_PTR(-EKEYREVOKED); key = NULL; } else { rka = cred->request_key_auth->payload.data; key = rka->dest_keyring; atomic_inc(&key->usage); } up_read(&cred->request_key_auth->sem); if (!key) goto error; key_ref = make_key_ref(key, 1); break; default: key_ref = ERR_PTR(-EINVAL); if (id < 1) goto error; key = key_lookup(id); if (IS_ERR(key)) { key_ref = ERR_CAST(key); goto error; } key_ref = make_key_ref(key, 0); /* check to see if we possess the key */ skey_ref = search_process_keyrings(key->type, key, lookup_user_key_possessed, cred); if (!IS_ERR(skey_ref)) { key_put(key); key_ref = skey_ref; } break; } if (!partial) { ret = wait_for_key_construction(key, true); switch (ret) { case -ERESTARTSYS: goto invalid_key; default: if (perm) goto invalid_key; case 0: break; } } else if (perm) { ret = key_validate(key); if (ret < 0) goto invalid_key; } ret = -EIO; if (!partial && !test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) goto invalid_key; /* check the permissions */ ret = key_task_permission(key_ref, cred, perm); if (ret < 0) goto invalid_key; error: put_cred(cred); return key_ref; invalid_key: key_ref_put(key_ref); key_ref = ERR_PTR(ret); goto error; /* if we attempted to install a keyring, then it may have caused new * creds to be installed */ reget_creds: put_cred(cred); goto try_again; } /* end lookup_user_key() */ /*****************************************************************************/ /* * join the named keyring as the session keyring if possible, or attempt to * create a new one of that name if not * - if the name is NULL, an empty anonymous keyring is installed instead * - named session keyring joining is done with a semaphore held */ long join_session_keyring(const char *name) { const struct cred *old; struct cred *new; struct key *keyring; long ret, serial; /* only permit this if there's a single thread in the thread group - * this avoids us having to adjust the creds on all threads and risking * ENOMEM */ if (!is_single_threaded(current)) return -EMLINK; new = prepare_creds(); if (!new) return -ENOMEM; old = current_cred(); /* if no name is provided, install an anonymous keyring */ if (!name) { ret = install_session_keyring_to_cred(new, NULL); if (ret < 0) goto error; serial = new->tgcred->session_keyring->serial; ret = commit_creds(new); if (ret == 0) ret = serial; goto okay; } /* allow the user to join or create a named keyring */ mutex_lock(&key_session_mutex); /* look for an existing keyring of this name */ keyring = find_keyring_by_name(name, false); if (PTR_ERR(keyring) == -ENOKEY) { /* not found - try and create a new one */ keyring = keyring_alloc(name, old->uid, old->gid, old, KEY_ALLOC_IN_QUOTA, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); goto error2; } } else if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); goto error2; } /* we've got a keyring - now to install it */ ret = install_session_keyring_to_cred(new, keyring); if (ret < 0) goto error2; commit_creds(new); mutex_unlock(&key_session_mutex); ret = keyring->serial; key_put(keyring); okay: return ret; error2: mutex_unlock(&key_session_mutex); error: abort_creds(new); return ret; }