cregit-Linux how code gets into the kernel

Release 4.15 security/keys/process_keys.c

Directory: security/keys
/* Manage 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/sched/user.h>
#include <linux/keyctl.h>
#include <linux/fs.h>
#include <linux/err.h>
#include <linux/mutex.h>
#include <linux/security.h>
#include <linux/user_namespace.h>
#include <linux/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		= REFCOUNT_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		= GLOBAL_ROOT_UID,
};

/*
 * Install the user and user session keyrings for the current process's UID.
 */

int install_user_keyrings(void) { struct user_struct *user; const struct cred *cred; struct key *uid_keyring, *session_keyring; key_perm_t user_keyring_perm; char buf[20]; int ret; uid_t uid; user_keyring_perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL; cred = current_cred(); user = cred->user; uid = from_kuid(cred->user_ns, user->uid); kenter("%p{%u}", user, uid); if (user->uid_keyring && user->session_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", uid); uid_keyring = find_keyring_by_name(buf, true); if (IS_ERR(uid_keyring)) { uid_keyring = keyring_alloc(buf, user->uid, INVALID_GID, cred, user_keyring_perm, KEY_ALLOC_UID_KEYRING | KEY_ALLOC_IN_QUOTA, NULL, 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", uid); session_keyring = find_keyring_by_name(buf, true); if (IS_ERR(session_keyring)) { session_keyring = keyring_alloc(buf, user->uid, INVALID_GID, cred, user_keyring_perm, KEY_ALLOC_UID_KEYRING | KEY_ALLOC_IN_QUOTA, NULL, 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; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells32293.06%975.00%
Eric W. Biedermann185.20%18.33%
Eric Biggers41.16%18.33%
Michael LeMay20.58%18.33%
Total346100.00%12100.00%

/* * Install a thread keyring to the given credentials struct if it didn't have * one already. This is allowed to overrun the quota. * * Return: 0 if a thread keyring is now present; -errno on failure. */
int install_thread_keyring_to_cred(struct cred *new) { struct key *keyring; if (new->thread_keyring) return 0; keyring = keyring_alloc("_tid", new->uid, new->gid, new, KEY_POS_ALL | KEY_USR_VIEW, KEY_ALLOC_QUOTA_OVERRUN, NULL, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); new->thread_keyring = keyring; return 0; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells6386.30%777.78%
Eric Biggers912.33%111.11%
Michael LeMay11.37%111.11%
Total73100.00%9100.00%

/* * Install a thread keyring to the current task if it didn't have one already. * * Return: 0 if a thread keyring is now present; -errno on failure. */
static int install_thread_keyring(void) { struct cred *new; int ret; new = prepare_creds(); if (!new) return -ENOMEM; ret = install_thread_keyring_to_cred(new); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells59100.00%3100.00%
Total59100.00%3100.00%

/* * Install a process keyring to the given credentials struct if it didn't have * one already. This is allowed to overrun the quota. * * Return: 0 if a process keyring is now present; -errno on failure. */
int install_process_keyring_to_cred(struct cred *new) { struct key *keyring; if (new->process_keyring) return 0; keyring = keyring_alloc("_pid", new->uid, new->gid, new, KEY_POS_ALL | KEY_USR_VIEW, KEY_ALLOC_QUOTA_OVERRUN, NULL, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); new->process_keyring = keyring; return 0; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells7197.26%981.82%
Michael LeMay11.37%19.09%
Eric Biggers11.37%19.09%
Total73100.00%11100.00%

/* * Install a process keyring to the current task if it didn't have one already. * * Return: 0 if a process keyring is now present; -errno on failure. */
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; } return commit_creds(new); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells59100.00%3100.00%
Total59100.00%3100.00%

/* * Install the given keyring as the session keyring of the given credentials * struct, replacing the existing one if any. If the given keyring is NULL, * then install a new anonymous session keyring. * * Return: 0 on success; -errno on failure. */
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->session_keyring) flags = KEY_ALLOC_IN_QUOTA; keyring = keyring_alloc("_ses", cred->uid, cred->gid, cred, KEY_POS_ALL | KEY_USR_VIEW | KEY_USR_READ, flags, NULL, NULL); if (IS_ERR(keyring)) return PTR_ERR(keyring); } else { __key_get(keyring); } /* install the keyring */ old = cred->session_keyring; rcu_assign_pointer(cred->session_keyring, keyring); if (old) key_put(old); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells12699.21%1090.91%
Michael LeMay10.79%19.09%
Total127100.00%11100.00%

/* * Install the given keyring as the session keyring of the current task, * replacing the existing one if any. If the given keyring is NULL, then * install a new anonymous session keyring. * * Return: 0 on success; -errno on failure. */
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, keyring); if (ret < 0) { abort_creds(new); return ret; } return commit_creds(new); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells64100.00%6100.00%
Total64100.00%6100.00%

/* * Handle the fsuid changing. */
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); } }

Contributors

PersonTokensPropCommitsCommitProp
David Howells67100.00%2100.00%
Total67100.00%2100.00%

/* * Handle the fsgid changing. */
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); } }

Contributors

PersonTokensPropCommitsCommitProp
David Howells67100.00%2100.00%
Total67100.00%2100.00%

/* * Search the process keyrings attached to the supplied cred for the first * matching key. * * The search criteria are the type and the match function. The description is * given to the match function as a parameter, but doesn't otherwise influence * the search. Typically the match function will compare the description * parameter to the key's description. * * This can only search keyrings that grant Search permission to the supplied * credentials. Keyrings linked to searched keyrings will also be searched if * they grant Search permission too. Keys can only be found if they grant * Search permission to the credentials. * * Returns a pointer to the key with the key usage count incremented if * successful, -EAGAIN if we didn't find any matching key or -ENOKEY if we only * matched negative keys. * * In the case of a successful return, the possession attribute is set on the * returned key reference. */
key_ref_t search_my_process_keyrings(struct keyring_search_context *ctx) { key_ref_t key_ref, ret, err; /* 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 (ctx->cred->thread_keyring) { key_ref = keyring_search_aux( make_key_ref(ctx->cred->thread_keyring, 1), ctx); if (!IS_ERR(key_ref)) goto found; switch (PTR_ERR(key_ref)) { case -EAGAIN: /* no key */ case -ENOKEY: /* negative key */ ret = key_ref; break; default: err = key_ref; break; } } /* search the process keyring second */ if (ctx->cred->process_keyring) { key_ref = keyring_search_aux( make_key_ref(ctx->cred->process_keyring, 1), ctx); 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 (ctx->cred->session_keyring) { rcu_read_lock(); key_ref = keyring_search_aux( make_key_ref(rcu_dereference(ctx->cred->session_keyring), 1), ctx); 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 (ctx->cred->user->session_keyring) { key_ref = keyring_search_aux( make_key_ref(ctx->cred->user->session_keyring, 1), ctx); 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; } } /* no key - decide on the error we're going to go for */ key_ref = ret ? ret : err; found: return key_ref; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells357100.00%12100.00%
Total357100.00%12100.00%

/* * Search the process keyrings attached to the supplied cred for the first * matching key in the manner of search_my_process_keyrings(), but also search * the keys attached to the assumed authorisation key using its credentials if * one is available. * * Return same as search_my_process_keyrings(). */
key_ref_t search_process_keyrings(struct keyring_search_context *ctx) { struct request_key_auth *rka; key_ref_t key_ref, ret = ERR_PTR(-EACCES), err; might_sleep(); key_ref = search_my_process_keyrings(ctx); if (!IS_ERR(key_ref)) goto found; err = key_ref; /* 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 (ctx->cred->request_key_auth && ctx->cred == current_cred() && ctx->index_key.type != &key_type_request_key_auth ) { const struct cred *cred = ctx->cred; /* defend against the auth key being revoked */ down_read(&cred->request_key_auth->sem); if (key_validate(ctx->cred->request_key_auth) == 0) { rka = ctx->cred->request_key_auth->payload.data[0]; ctx->cred = rka->cred; key_ref = search_process_keyrings(ctx); ctx->cred = cred; up_read(&cred->request_key_auth->sem); if (!IS_ERR(key_ref)) goto found; ret = key_ref; } else { up_read(&cred->request_key_auth->sem); } } /* no key - decide on the error we're going to go for */ if (err == ERR_PTR(-ENOKEY) || ret == ERR_PTR(-ENOKEY)) key_ref = ERR_PTR(-ENOKEY); else if (err == ERR_PTR(-EACCES)) key_ref = ret; else key_ref = err; found: return key_ref; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells242100.00%10100.00%
Total242100.00%10100.00%

/* * See if the key we're looking at is the target key. */
bool lookup_user_key_possessed(const struct key *key, const struct key_match_data *match_data) { return key == match_data->raw_data; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells24100.00%4100.00%
Total24100.00%4100.00%

/* * Look up a key ID given us by userspace with a given permissions mask to get * the key it refers to. * * Flags can be passed to request that special keyrings be created if referred * to directly, to permit partially constructed keys to be found and to skip * validity and permission checks on the found key. * * Returns a pointer to the key with an incremented usage count if successful; * -EINVAL if the key ID is invalid; -ENOKEY if the key ID does not correspond * to a key or the best found key was a negative key; -EKEYREVOKED or * -EKEYEXPIRED if the best found key was revoked or expired; -EACCES if the * found key doesn't grant the requested permit or the LSM denied access to it; * or -ENOMEM if a special keyring couldn't be created. * * In the case of a successful return, the possession attribute is set on the * returned key reference. */
key_ref_t lookup_user_key(key_serial_t id, unsigned long lflags, key_perm_t perm) { struct keyring_search_context ctx = { .match_data.cmp = lookup_user_key_possessed, .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, .flags = KEYRING_SEARCH_NO_STATE_CHECK, }; struct request_key_auth *rka; struct key *key; key_ref_t key_ref, skey_ref; int ret; try_again: ctx.cred = get_current_cred(); key_ref = ERR_PTR(-ENOKEY); switch (id) { case KEY_SPEC_THREAD_KEYRING: if (!ctx.cred->thread_keyring) { if (!(lflags & KEY_LOOKUP_CREATE)) goto error; ret = install_thread_keyring(); if (ret < 0) { key_ref = ERR_PTR(ret); goto error; } goto reget_creds; } key = ctx.cred->thread_keyring; __key_get(key); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_PROCESS_KEYRING: if (!ctx.cred->process_keyring) { if (!(lflags & KEY_LOOKUP_CREATE)) goto error; ret = install_process_keyring(); if (ret < 0) { key_ref = ERR_PTR(ret); goto error; } goto reget_creds; } key = ctx.cred->process_keyring; __key_get(key); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_SESSION_KEYRING: if (!ctx.cred->session_keyring) { /* always install a session keyring upon access if one * doesn't exist yet */ ret = install_user_keyrings(); if (ret < 0) goto error; if (lflags & KEY_LOOKUP_CREATE) ret = join_session_keyring(NULL); else ret = install_session_keyring( ctx.cred->user->session_keyring); if (ret < 0) goto error; goto reget_creds; } else if (ctx.cred->session_keyring == ctx.cred->user->session_keyring && lflags & KEY_LOOKUP_CREATE) { ret = join_session_keyring(NULL); if (ret < 0) goto error; goto reget_creds; } rcu_read_lock(); key = rcu_dereference(ctx.cred->session_keyring); __key_get(key); rcu_read_unlock(); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_USER_KEYRING: if (!ctx.cred->user->uid_keyring) { ret = install_user_keyrings(); if (ret < 0) goto error; } key = ctx.cred->user->uid_keyring; __key_get(key); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_USER_SESSION_KEYRING: if (!ctx.cred->user->session_keyring) { ret = install_user_keyrings(); if (ret < 0) goto error; } key = ctx.cred->user->session_keyring; __key_get(key); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_GROUP_KEYRING: /* group keyrings are not yet supported */ key_ref = ERR_PTR(-EINVAL); goto error; case KEY_SPEC_REQKEY_AUTH_KEY: key = ctx.cred->request_key_auth; if (!key) goto error; __key_get(key); key_ref = make_key_ref(key, 1); break; case KEY_SPEC_REQUESTOR_KEYRING: if (!ctx.cred->request_key_auth) goto error; down_read(&ctx.cred->request_key_auth->sem); if (test_bit(KEY_FLAG_REVOKED, &ctx.cred->request_key_auth->flags)) { key_ref = ERR_PTR(-EKEYREVOKED); key = NULL; } else { rka = ctx.cred->request_key_auth->payload.data[0]; key = rka->dest_keyring; __key_get(key); } up_read(&ctx.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 */ ctx.index_key.type = key->type; ctx.index_key.description = key->description; ctx.index_key.desc_len = strlen(key->description); ctx.match_data.raw_data = key; kdebug("check possessed"); skey_ref = search_process_keyrings(&ctx); kdebug("possessed=%p", skey_ref); if (!IS_ERR(skey_ref)) { key_put(key); key_ref = skey_ref; } break; } /* unlink does not use the nominated key in any way, so can skip all * the permission checks as it is only concerned with the keyring */ if (lflags & KEY_LOOKUP_FOR_UNLINK) { ret = 0; goto error; } if (!(lflags & KEY_LOOKUP_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 (!(lflags & KEY_LOOKUP_PARTIAL) && key_read_state(key) == KEY_IS_UNINSTANTIATED) goto invalid_key; /* check the permissions */ ret = key_task_permission(key_ref, ctx.cred, perm); if (ret < 0) goto invalid_key; key->last_used_at = ktime_get_real_seconds(); error: put_cred(ctx.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(ctx.cred); goto try_again; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells95398.96%2288.00%
Dan Carpenter90.93%28.00%
Baolin Wang10.10%14.00%
Total963100.00%25100.00%

/* * Join the named keyring as the session keyring if possible else attempt to * create a new one of that name and join that. * * If the name is NULL, an empty anonymous keyring will be installed as the * session keyring. * * Named session keyrings are joined with a semaphore held to prevent the * keyrings from going away whilst the attempt is made to going them and also * to prevent a race in creating compatible session keyrings. */
long join_session_keyring(const char *name) { const struct cred *old; struct cred *new; struct key *keyring; long ret, serial; 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->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,