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IMA may verify a file's integrity against a "good" value stored in the 'security.ima' xattr or as an appended signature, based on policy. When the "good value" is stored in the xattr, the xattr may contain a file hash or signature. In either case, the "good" value is preceded by a header. The first byte of the xattr header indicates the type of data - hash, signature - stored in the xattr. To support storing fs-verity signatures in the 'security.ima' xattr requires further differentiating the fs-verity signature from the existing IMA signature. In addition the signatures stored in 'security.ima' xattr, need to be disambiguated. Instead of directly signing the fs-verity digest, a new signature format version 3 is defined as the hash of the ima_file_id structure, which identifies the type of signature and the digest. The IMA policy defines "which" files are to be measured, verified, and/or audited. For those files being verified, the policy rules indicate "how" the file should be verified. For example to require a file be signed, the appraise policy rule must include the 'appraise_type' option. appraise_type:= [imasig] | [imasig|modsig] | [sigv3] where 'imasig' is the original or signature format v2 (default), where 'modsig' is an appended signature, where 'sigv3' is the signature format v3. The policy rule must also indicate the type of digest, if not the IMA default, by first specifying the digest type: digest_type:= [verity] The following policy rule requires fsverity signatures. The rule may be constrained, for example based on a fsuuid or LSM label. appraise func=BPRM_CHECK digest_type=verity appraise_type=sigv3 Acked-by: Stefan Berger <stefanb@linux.ibm.com> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
218 lines
5.1 KiB
C
218 lines
5.1 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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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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#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/kernel_read_file.h>
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#include <linux/key-type.h>
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#include <linux/digsig.h>
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#include <linux/vmalloc.h>
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#include <crypto/public_key.h>
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#include <keys/system_keyring.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 * const 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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".platform",
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".machine",
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};
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#ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
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#define restrict_link_to_ima restrict_link_by_builtin_and_secondary_trusted
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#else
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#define restrict_link_to_ima restrict_link_by_builtin_trusted
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#endif
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static struct key *integrity_keyring_from_id(const unsigned int id)
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{
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if (id >= INTEGRITY_KEYRING_MAX)
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return ERR_PTR(-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_PTR(err);
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}
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}
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return keyring[id];
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}
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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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struct key *keyring;
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if (siglen < 2)
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return -EINVAL;
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keyring = integrity_keyring_from_id(id);
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if (IS_ERR(keyring))
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return PTR_ERR(keyring);
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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, sig + 1, siglen - 1, digest,
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digestlen);
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case 2: /* regular file data hash based signature */
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case 3: /* struct ima_file_id data based signature */
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return asymmetric_verify(keyring, sig, siglen, digest,
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digestlen);
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}
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return -EOPNOTSUPP;
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}
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int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
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{
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struct key *keyring;
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keyring = integrity_keyring_from_id(id);
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if (IS_ERR(keyring))
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return PTR_ERR(keyring);
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return ima_modsig_verify(keyring, modsig);
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}
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static int __init __integrity_init_keyring(const unsigned int id,
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key_perm_t perm,
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struct key_restriction *restriction)
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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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keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
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KGIDT_INIT(0), cred, perm,
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KEY_ALLOC_NOT_IN_QUOTA, restriction, 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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} else {
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if (id == INTEGRITY_KEYRING_PLATFORM)
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set_platform_trusted_keys(keyring[id]);
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if (id == INTEGRITY_KEYRING_MACHINE && trust_moklist())
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set_machine_trusted_keys(keyring[id]);
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if (id == INTEGRITY_KEYRING_IMA)
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load_module_cert(keyring[id]);
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}
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return err;
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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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struct key_restriction *restriction;
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key_perm_t perm;
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perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
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| KEY_USR_READ | KEY_USR_SEARCH;
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if (id == INTEGRITY_KEYRING_PLATFORM ||
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id == INTEGRITY_KEYRING_MACHINE) {
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restriction = NULL;
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goto out;
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}
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if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
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return 0;
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restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
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if (!restriction)
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return -ENOMEM;
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restriction->check = restrict_link_to_ima;
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/*
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* MOK keys can only be added through a read-only runtime services
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* UEFI variable during boot. No additional keys shall be allowed to
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* load into the machine keyring following init from userspace.
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*/
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if (id != INTEGRITY_KEYRING_MACHINE)
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perm |= KEY_USR_WRITE;
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out:
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return __integrity_init_keyring(id, perm, restriction);
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}
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static int __init integrity_add_key(const unsigned int id, const void *data,
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off_t size, key_perm_t perm)
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{
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key_ref_t key;
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int rc = 0;
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if (!keyring[id])
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return -EINVAL;
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key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
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NULL, data, size, perm,
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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\n", rc);
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} else {
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pr_notice("Loaded X.509 cert '%s'\n",
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key_ref_to_ptr(key)->description);
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key_ref_put(key);
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}
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return rc;
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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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void *data = NULL;
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size_t size;
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int rc;
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key_perm_t perm;
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rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
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READING_X509_CERTIFICATE);
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if (rc < 0) {
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pr_err("Unable to open file: %s (%d)", path, rc);
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return rc;
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}
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size = rc;
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perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
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pr_info("Loading X.509 certificate: %s\n", path);
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rc = integrity_add_key(id, (const void *)data, size, perm);
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vfree(data);
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return rc;
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}
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int __init integrity_load_cert(const unsigned int id, const char *source,
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const void *data, size_t len, key_perm_t perm)
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{
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if (!data)
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return -EINVAL;
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pr_info("Loading X.509 certificate: %s\n", source);
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return integrity_add_key(id, data, len, perm);
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}
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