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5ac7eace2d
Add a facility whereby proposed new links to be added to a keyring can be
vetted, permitting them to be rejected if necessary. This can be used to
block public keys from which the signature cannot be verified or for which
the signature verification fails. It could also be used to provide
blacklisting.
This affects operations like add_key(), KEYCTL_LINK and KEYCTL_INSTANTIATE.
To this end:
(1) A function pointer is added to the key struct that, if set, points to
the vetting function. This is called as:
int (*restrict_link)(struct key *keyring,
const struct key_type *key_type,
unsigned long key_flags,
const union key_payload *key_payload),
where 'keyring' will be the keyring being added to, key_type and
key_payload will describe the key being added and key_flags[*] can be
AND'ed with KEY_FLAG_TRUSTED.
[*] This parameter will be removed in a later patch when
KEY_FLAG_TRUSTED is removed.
The function should return 0 to allow the link to take place or an
error (typically -ENOKEY, -ENOPKG or -EKEYREJECTED) to reject the
link.
The pointer should not be set directly, but rather should be set
through keyring_alloc().
Note that if called during add_key(), preparse is called before this
method, but a key isn't actually allocated until after this function
is called.
(2) KEY_ALLOC_BYPASS_RESTRICTION is added. This can be passed to
key_create_or_update() or key_instantiate_and_link() to bypass the
restriction check.
(3) KEY_FLAG_TRUSTED_ONLY is removed. The entire contents of a keyring
with this restriction emplaced can be considered 'trustworthy' by
virtue of being in the keyring when that keyring is consulted.
(4) key_alloc() and keyring_alloc() take an extra argument that will be
used to set restrict_link in the new key. This ensures that the
pointer is set before the key is published, thus preventing a window
of unrestrictedness. Normally this argument will be NULL.
(5) As a temporary affair, keyring_restrict_trusted_only() is added. It
should be passed to keyring_alloc() as the extra argument instead of
setting KEY_FLAG_TRUSTED_ONLY on a keyring. This will be replaced in
a later patch with functions that look in the appropriate places for
authoritative keys.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
130 lines
2.8 KiB
C
130 lines
2.8 KiB
C
/*
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* Copyright (C) 2011 Intel Corporation
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*
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* Author:
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* Dmitry Kasatkin <dmitry.kasatkin@intel.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2 of the License.
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*
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/err.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <linux/cred.h>
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#include <linux/key-type.h>
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#include <linux/digsig.h>
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#include "integrity.h"
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static struct key *keyring[INTEGRITY_KEYRING_MAX];
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static const char *keyring_name[INTEGRITY_KEYRING_MAX] = {
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#ifndef CONFIG_INTEGRITY_TRUSTED_KEYRING
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"_evm",
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"_ima",
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#else
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".evm",
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".ima",
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#endif
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"_module",
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};
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#ifdef CONFIG_INTEGRITY_TRUSTED_KEYRING
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static bool init_keyring __initdata = true;
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#else
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static bool init_keyring __initdata;
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#endif
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int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
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const char *digest, int digestlen)
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{
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if (id >= INTEGRITY_KEYRING_MAX)
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return -EINVAL;
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if (!keyring[id]) {
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keyring[id] =
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request_key(&key_type_keyring, keyring_name[id], NULL);
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if (IS_ERR(keyring[id])) {
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int err = PTR_ERR(keyring[id]);
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pr_err("no %s keyring: %d\n", keyring_name[id], err);
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keyring[id] = NULL;
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return err;
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}
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}
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switch (sig[1]) {
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case 1:
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/* v1 API expect signature without xattr type */
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return digsig_verify(keyring[id], sig + 1, siglen - 1,
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digest, digestlen);
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case 2:
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return asymmetric_verify(keyring[id], sig, siglen,
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digest, digestlen);
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}
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return -EOPNOTSUPP;
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}
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int __init integrity_init_keyring(const unsigned int id)
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{
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const struct cred *cred = current_cred();
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int err = 0;
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if (!init_keyring)
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return 0;
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keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
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KGIDT_INIT(0), cred,
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((KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW | KEY_USR_READ |
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KEY_USR_WRITE | KEY_USR_SEARCH),
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KEY_ALLOC_NOT_IN_QUOTA,
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NULL, NULL);
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if (IS_ERR(keyring[id])) {
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err = PTR_ERR(keyring[id]);
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pr_info("Can't allocate %s keyring (%d)\n",
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keyring_name[id], err);
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keyring[id] = NULL;
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}
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return err;
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}
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int __init integrity_load_x509(const unsigned int id, const char *path)
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{
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key_ref_t key;
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char *data;
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int rc;
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if (!keyring[id])
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return -EINVAL;
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rc = integrity_read_file(path, &data);
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if (rc < 0)
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return rc;
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key = key_create_or_update(make_key_ref(keyring[id], 1),
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"asymmetric",
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NULL,
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data,
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rc,
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((KEY_POS_ALL & ~KEY_POS_SETATTR) |
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KEY_USR_VIEW | KEY_USR_READ),
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KEY_ALLOC_NOT_IN_QUOTA);
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if (IS_ERR(key)) {
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rc = PTR_ERR(key);
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pr_err("Problem loading X.509 certificate (%d): %s\n",
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rc, path);
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} else {
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pr_notice("Loaded X.509 cert '%s': %s\n",
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key_ref_to_ptr(key)->description, path);
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key_ref_put(key);
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}
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kfree(data);
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return 0;
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}
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