// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2011 Intel Corporation
 *
 * Author:
 * Dmitry Kasatkin <dmitry.kasatkin@intel.com>
 */

#include <linux/err.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/kernel_read_file.h>
#include <linux/key-type.h>
#include <linux/digsig.h>
#include <linux/vmalloc.h>
#include <crypto/public_key.h>
#include <keys/system_keyring.h>

#include "integrity.h"

static struct key *keyring[INTEGRITY_KEYRING_MAX];

static const char * const keyring_name[INTEGRITY_KEYRING_MAX] = {
#ifndef CONFIG_INTEGRITY_TRUSTED_KEYRING
        "_evm",
        "_ima",
#else
        ".evm",
        ".ima",
#endif
        ".platform",
        ".machine",
};

#ifdef CONFIG_IMA_KEYRINGS_PERMIT_SIGNED_BY_BUILTIN_OR_SECONDARY
#define restrict_link_to_ima restrict_link_by_digsig_builtin_and_secondary
#else
#define restrict_link_to_ima restrict_link_by_digsig_builtin
#endif

static struct key *integrity_keyring_from_id(const unsigned int id)
{
        if (id >= INTEGRITY_KEYRING_MAX)
                return ERR_PTR(-EINVAL);

        if (!keyring[id]) {
                keyring[id] =
                        request_key(&key_type_keyring, keyring_name[id], NULL);
                if (IS_ERR(keyring[id])) {
                        int err = PTR_ERR(keyring[id]);
                        pr_err("no %s keyring: %d\n", keyring_name[id], err);
                        keyring[id] = NULL;
                        return ERR_PTR(err);
                }
        }

        return keyring[id];
}

int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
                            const char *digest, int digestlen)
{
        struct key *keyring;

        if (siglen < 2)
                return -EINVAL;

        keyring = integrity_keyring_from_id(id);
        if (IS_ERR(keyring))
                return PTR_ERR(keyring);

        switch (sig[1]) {
        case 1:
                /* v1 API expect signature without xattr type */
                return digsig_verify(keyring, sig + 1, siglen - 1, digest,
                                     digestlen);
        case 2: /* regular file data hash based signature */
        case 3: /* struct ima_file_id data based signature */
                return asymmetric_verify(keyring, sig, siglen, digest,
                                         digestlen);
        }

        return -EOPNOTSUPP;
}

int integrity_modsig_verify(const unsigned int id, const struct modsig *modsig)
{
        struct key *keyring;

        keyring = integrity_keyring_from_id(id);
        if (IS_ERR(keyring))
                return PTR_ERR(keyring);

        return ima_modsig_verify(keyring, modsig);
}

static int __init __integrity_init_keyring(const unsigned int id,
                                           key_perm_t perm,
                                           struct key_restriction *restriction)
{
        const struct cred *cred = current_cred();
        int err = 0;

        keyring[id] = keyring_alloc(keyring_name[id], KUIDT_INIT(0),
                                    KGIDT_INIT(0), cred, perm,
                                    KEY_ALLOC_NOT_IN_QUOTA, restriction, NULL);
        if (IS_ERR(keyring[id])) {
                err = PTR_ERR(keyring[id]);
                pr_info("Can't allocate %s keyring (%d)\n",
                        keyring_name[id], err);
                keyring[id] = NULL;
        } else {
                if (id == INTEGRITY_KEYRING_PLATFORM)
                        set_platform_trusted_keys(keyring[id]);
                if (id == INTEGRITY_KEYRING_MACHINE && imputed_trust_enabled())
                        set_machine_trusted_keys(keyring[id]);
                if (id == INTEGRITY_KEYRING_IMA)
                        load_module_cert(keyring[id]);
        }

        return err;
}

int __init integrity_init_keyring(const unsigned int id)
{
        struct key_restriction *restriction;
        key_perm_t perm;
        int ret;

        perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW
                | KEY_USR_READ | KEY_USR_SEARCH;

        if (id == INTEGRITY_KEYRING_PLATFORM ||
            (id == INTEGRITY_KEYRING_MACHINE &&
            !IS_ENABLED(CONFIG_INTEGRITY_CA_MACHINE_KEYRING))) {
                restriction = NULL;
                goto out;
        }

        if (!IS_ENABLED(CONFIG_INTEGRITY_TRUSTED_KEYRING))
                return 0;

        restriction = kzalloc_obj(struct key_restriction);
        if (!restriction)
                return -ENOMEM;

        if (id == INTEGRITY_KEYRING_MACHINE)
                restriction->check = restrict_link_by_ca;
        else
                restriction->check = restrict_link_to_ima;

        /*
         * MOK keys can only be added through a read-only runtime services
         * UEFI variable during boot. No additional keys shall be allowed to
         * load into the machine keyring following init from userspace.
         */
        if (id != INTEGRITY_KEYRING_MACHINE)
                perm |= KEY_USR_WRITE;

out:
        ret = __integrity_init_keyring(id, perm, restriction);
        if (ret)
                kfree(restriction);
        return ret;
}

static int __init integrity_add_key(const unsigned int id, const void *data,
                                    off_t size, key_perm_t perm)
{
        key_ref_t key;
        int rc = 0;

        if (!keyring[id])
                return -EINVAL;

        key = key_create_or_update(make_key_ref(keyring[id], 1), "asymmetric",
                                   NULL, data, size, perm,
                                   KEY_ALLOC_NOT_IN_QUOTA);
        if (IS_ERR(key)) {
                rc = PTR_ERR(key);
                if (id != INTEGRITY_KEYRING_MACHINE)
                        pr_err("Problem loading X.509 certificate %d\n", rc);
        } else {
                pr_notice("Loaded X.509 cert '%s'\n",
                          key_ref_to_ptr(key)->description);
                key_ref_put(key);
        }

        return rc;

}

int __init integrity_load_x509(const unsigned int id, const char *path)
{
        void *data = NULL;
        size_t size;
        int rc;
        key_perm_t perm;

        rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
                                        READING_X509_CERTIFICATE);
        if (rc < 0) {
                pr_err("Unable to open file: %s (%d)", path, rc);
                return rc;
        }
        size = rc;

        perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;

        pr_info("Loading X.509 certificate: %s\n", path);
        rc = integrity_add_key(id, (const void *)data, size, perm);

        vfree(data);
        return rc;
}

int __init integrity_load_cert(const unsigned int id, const char *source,
                               const void *data, size_t len, key_perm_t perm)
{
        if (!data)
                return -EINVAL;

        pr_info("Loading X.509 certificate: %s\n", source);
        return integrity_add_key(id, data, len, perm);
}