security/integrity/digsig.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Copyright (C) 2011 Intel Corporation
0004  *
0005  * Author:
0006  * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
0007  */
0008
0009 #include <linux/err.h>
0010 #include <linux/sched.h>
0011 #include <linux/slab.h>
0012 #include <linux/cred.h>
0013 #include <linux/kernel_read_file.h>
0014 #include <linux/key-type.h>
0015 #include <linux/digsig.h>
0016 #include <linux/vmalloc.h>
0017 #include <crypto/public_key.h>
0018 #include <keys/system_keyring.h>
0019
0020 #include "integrity.h"
0021
0022 static struct key *keyring[INTEGRITY_KEYRING_MAX];
0023
0024 static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = {
0025 #ifndef CONFIG_INTEGRITY_TRUSTED_KEYRING
0026     "_evm",
0027     "_ima",
0028 #else
0029     ".evm",
0030     ".ima",
0031 #endif
0032     ".platform",
0033     ".machine",
0034 };
0035
0036 #ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
0037 #define restrict_link_to_ima restrict_link_by_builtin_and_secondary_trusted
0038 #else
0039 #define restrict_link_to_ima restrict_link_by_builtin_trusted
0040 #endif
0041
0042 static struct key *integrity_keyring_from_id(const unsigned int id)
0043 {
0044     if (id >= INTEGRITY_KEYRING_MAX)
0045         return ERR_PTR(-EINVAL);
0046
0047     if (!keyring[id]) {
0048         keyring[id] =
0049             request_key(&key_type_keyring, keyring_name[id], NULL);
0050         if (IS_ERR(keyring[id])) {
0051             int err = PTR_ERR(keyring[id]);
0052             pr_err("no %s keyring: %d\n", keyring_name[id], err);
0053             keyring[id] = NULL;
0054             return ERR_PTR(err);
0055         }
0056     }
0057
0058     return keyring[id];
0059 }
0060
0061 int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
0062                 const char *digest, int digestlen)
0063 {
0064     struct key *keyring;
0065
0066     if (siglen < 2)
0067         return -EINVAL;
0068
0069     keyring = integrity_keyring_from_id(id);
0070     if (IS_ERR(keyring))
0071         return PTR_ERR(keyring);
0072
0073     switch (sig[1]) {
0074     case 1:
0075         /* v1 API expect signature without xattr type */
0076         return digsig_verify(keyring, sig + 1, siglen - 1, digest,
0077                      digestlen);
0078     case 2: /* regular file data hash based signature */
0079     case 3: /* struct ima_file_id data based signature */
0080         return asymmetric_verify(keyring, sig, siglen, digest,
0081                      digestlen);
0082     }
0083
0084     return -EOPNOTSUPP;
0085 }
0086
0087 int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
0088 {
0089     struct key *keyring;
0090
0091     keyring = integrity_keyring_from_id(id);
0092     if (IS_ERR(keyring))
0093         return PTR_ERR(keyring);
0094
0095     return ima_modsig_verify(keyring, modsig);
0096 }
0097
0098 static int __init __integrity_init_keyring(const unsigned int id,
0099                        key_perm_t perm,
0100                        struct key_restriction *restriction)
0101 {
0102     const struct cred *cred = current_cred();
0103     int err = 0;
0104
0105     keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
0106                     KGIDT_INIT(0), cred, perm,
0107                     KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
0108     if (IS_ERR(keyring[id])) {
0109         err = PTR_ERR(keyring[id]);
0110         pr_info("Can't allocate %s keyring (%d)\n",
0111             keyring_name[id], err);
0112         keyring[id] = NULL;
0113     } else {
0114         if (id == INTEGRITY_KEYRING_PLATFORM)
0115             set_platform_trusted_keys(keyring[id]);
0116         if (id == INTEGRITY_KEYRING_MACHINE && trust_moklist())
0117             set_machine_trusted_keys(keyring[id]);
0118         if (id == INTEGRITY_KEYRING_IMA)
0119             load_module_cert(keyring[id]);
0120     }
0121
0122     return err;
0123 }
0124
0125 int __init integrity_init_keyring(const unsigned int id)
0126 {
0127     struct key_restriction *restriction;
0128     key_perm_t perm;
0129
0130     perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
0131         | KEY_USR_READ | KEY_USR_SEARCH;
0132
0133     if (id == INTEGRITY_KEYRING_PLATFORM ||
0134         id == INTEGRITY_KEYRING_MACHINE) {
0135         restriction = NULL;
0136         goto out;
0137     }
0138
0139     if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
0140         return 0;
0141
0142     restriction = kzalloc(sizeof(struct key_restriction), GFP_KERNEL);
0143     if (!restriction)
0144         return -ENOMEM;
0145
0146     restriction->check = restrict_link_to_ima;
0147
0148     /*
0149      * MOK keys can only be added through a read-only runtime services
0150      * UEFI variable during boot. No additional keys shall be allowed to
0151      * load into the machine keyring following init from userspace.
0152      */
0153     if (id != INTEGRITY_KEYRING_MACHINE)
0154         perm |= KEY_USR_WRITE;
0155
0156 out:
0157     return __integrity_init_keyring(id, perm, restriction);
0158 }
0159
0160 static int __init integrity_add_key(const unsigned int id, const void *data,
0161                     off_t size, key_perm_t perm)
0162 {
0163     key_ref_t key;
0164     int rc = 0;
0165
0166     if (!keyring[id])
0167         return -EINVAL;
0168
0169     key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
0170                    NULL, data, size, perm,
0171                    KEY_ALLOC_NOT_IN_QUOTA);
0172     if (IS_ERR(key)) {
0173         rc = PTR_ERR(key);
0174         pr_err("Problem loading X.509 certificate %d\n", rc);
0175     } else {
0176         pr_notice("Loaded X.509 cert '%s'\n",
0177               key_ref_to_ptr(key)->description);
0178         key_ref_put(key);
0179     }
0180
0181     return rc;
0182
0183 }
0184
0185 int __init integrity_load_x509(const unsigned int id, const char *path)
0186 {
0187     void *data = NULL;
0188     size_t size;
0189     int rc;
0190     key_perm_t perm;
0191
0192     rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
0193                     READING_X509_CERTIFICATE);
0194     if (rc < 0) {
0195         pr_err("Unable to open file: %s (%d)", path, rc);
0196         return rc;
0197     }
0198     size = rc;
0199
0200     perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;
0201
0202     pr_info("Loading X.509 certificate: %s\n", path);
0203     rc = integrity_add_key(id, (const void *)data, size, perm);
0204
0205     vfree(data);
0206     return rc;
0207 }
0208
0209 int __init integrity_load_cert(const unsigned int id, const char *source,
0210                    const void *data, size_t len, key_perm_t perm)
0211 {
0212     if (!data)
0213         return -EINVAL;
0214
0215     pr_info("Loading X.509 certificate: %s\n", source);
0216     return integrity_add_key(id, data, len, perm);
0217 }