403 lines
10 KiB
C
403 lines
10 KiB
C
/* Instantiate a public key crypto key from an X.509 Certificate
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*
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* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public Licence
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* as published by the Free Software Foundation; either version
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* 2 of the Licence, or (at your option) any later version.
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*/
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#define pr_fmt(fmt) "X.509: "fmt
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/err.h>
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#include <linux/mpi.h>
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#include <linux/asn1_decoder.h>
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#include <keys/asymmetric-subtype.h>
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#include <keys/asymmetric-parser.h>
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#include <keys/system_keyring.h>
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#include <crypto/hash.h>
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#include "asymmetric_keys.h"
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#include "public_key.h"
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#include "x509_parser.h"
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static bool use_builtin_keys;
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static struct asymmetric_key_id *ca_keyid;
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#ifndef MODULE
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static struct {
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struct asymmetric_key_id id;
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unsigned char data[10];
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} cakey;
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static int __init ca_keys_setup(char *str)
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{
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if (!str) /* default system keyring */
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return 1;
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if (strncmp(str, "id:", 3) == 0) {
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struct asymmetric_key_id *p = &cakey.id;
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size_t hexlen = (strlen(str) - 3) / 2;
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int ret;
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if (hexlen == 0 || hexlen > sizeof(cakey.data)) {
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pr_err("Missing or invalid ca_keys id\n");
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return 1;
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}
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ret = __asymmetric_key_hex_to_key_id(str + 3, p, hexlen);
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if (ret < 0)
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pr_err("Unparsable ca_keys id hex string\n");
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else
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ca_keyid = p; /* owner key 'id:xxxxxx' */
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} else if (strcmp(str, "builtin") == 0) {
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use_builtin_keys = true;
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}
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return 1;
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}
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__setup("ca_keys=", ca_keys_setup);
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#endif
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/**
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* x509_request_asymmetric_key - Request a key by X.509 certificate params.
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* @keyring: The keys to search.
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* @id: The issuer & serialNumber to look for or NULL.
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* @skid: The subjectKeyIdentifier to look for or NULL.
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* @partial: Use partial match if true, exact if false.
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*
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* Find a key in the given keyring by identifier. The preferred identifier is
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* the issuer + serialNumber and the fallback identifier is the
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* subjectKeyIdentifier. If both are given, the lookup is by the former, but
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* the latter must also match.
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*/
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struct key *x509_request_asymmetric_key(struct key *keyring,
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const struct asymmetric_key_id *id,
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const struct asymmetric_key_id *skid,
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bool partial)
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{
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struct key *key;
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key_ref_t ref;
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const char *lookup;
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char *req, *p;
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int len;
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if (id) {
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lookup = id->data;
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len = id->len;
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} else {
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lookup = skid->data;
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len = skid->len;
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}
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/* Construct an identifier "id:<keyid>". */
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p = req = kmalloc(2 + 1 + len * 2 + 1, GFP_KERNEL);
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if (!req)
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return ERR_PTR(-ENOMEM);
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if (partial) {
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*p++ = 'i';
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*p++ = 'd';
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} else {
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*p++ = 'e';
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*p++ = 'x';
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}
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*p++ = ':';
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p = bin2hex(p, lookup, len);
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*p = 0;
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pr_debug("Look up: \"%s\"\n", req);
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ref = keyring_search(make_key_ref(keyring, 1),
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&key_type_asymmetric, req);
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if (IS_ERR(ref))
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pr_debug("Request for key '%s' err %ld\n", req, PTR_ERR(ref));
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kfree(req);
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if (IS_ERR(ref)) {
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switch (PTR_ERR(ref)) {
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/* Hide some search errors */
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case -EACCES:
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case -ENOTDIR:
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case -EAGAIN:
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return ERR_PTR(-ENOKEY);
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default:
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return ERR_CAST(ref);
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}
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}
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key = key_ref_to_ptr(ref);
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if (id && skid) {
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const struct asymmetric_key_ids *kids = asymmetric_key_ids(key);
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if (!kids->id[1]) {
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pr_debug("issuer+serial match, but expected SKID missing\n");
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goto reject;
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}
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if (!asymmetric_key_id_same(skid, kids->id[1])) {
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pr_debug("issuer+serial match, but SKID does not\n");
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goto reject;
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}
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}
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pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key));
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return key;
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reject:
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key_put(key);
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return ERR_PTR(-EKEYREJECTED);
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}
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EXPORT_SYMBOL_GPL(x509_request_asymmetric_key);
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/*
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* Set up the signature parameters in an X.509 certificate. This involves
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* digesting the signed data and extracting the signature.
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*/
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int x509_get_sig_params(struct x509_certificate *cert)
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{
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struct crypto_shash *tfm;
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struct shash_desc *desc;
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size_t digest_size, desc_size;
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void *digest;
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int ret;
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pr_devel("==>%s()\n", __func__);
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if (cert->unsupported_crypto)
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return -ENOPKG;
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if (cert->sig.rsa.s)
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return 0;
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cert->sig.rsa.s = mpi_read_raw_data(cert->raw_sig, cert->raw_sig_size);
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if (!cert->sig.rsa.s)
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return -ENOMEM;
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cert->sig.nr_mpi = 1;
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/* Allocate the hashing algorithm we're going to need and find out how
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* big the hash operational data will be.
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*/
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tfm = crypto_alloc_shash(hash_algo_name[cert->sig.pkey_hash_algo], 0, 0);
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if (IS_ERR(tfm)) {
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if (PTR_ERR(tfm) == -ENOENT) {
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cert->unsupported_crypto = true;
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return -ENOPKG;
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}
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return PTR_ERR(tfm);
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}
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desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
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digest_size = crypto_shash_digestsize(tfm);
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/* We allocate the hash operational data storage on the end of the
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* digest storage space.
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*/
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ret = -ENOMEM;
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digest = kzalloc(ALIGN(digest_size, __alignof__(*desc)) + desc_size,
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GFP_KERNEL);
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if (!digest)
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goto error;
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cert->sig.digest = digest;
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cert->sig.digest_size = digest_size;
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desc = PTR_ALIGN(digest + digest_size, __alignof__(*desc));
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desc->tfm = tfm;
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desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
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ret = crypto_shash_init(desc);
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if (ret < 0)
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goto error;
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might_sleep();
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ret = crypto_shash_finup(desc, cert->tbs, cert->tbs_size, digest);
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error:
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crypto_free_shash(tfm);
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pr_devel("<==%s() = %d\n", __func__, ret);
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return ret;
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}
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EXPORT_SYMBOL_GPL(x509_get_sig_params);
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/*
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* Check the signature on a certificate using the provided public key
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*/
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int x509_check_signature(const struct public_key *pub,
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struct x509_certificate *cert)
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{
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int ret;
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pr_devel("==>%s()\n", __func__);
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ret = x509_get_sig_params(cert);
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if (ret < 0)
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return ret;
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ret = public_key_verify_signature(pub, &cert->sig);
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if (ret == -ENOPKG)
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cert->unsupported_crypto = true;
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pr_debug("Cert Verification: %d\n", ret);
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return ret;
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}
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EXPORT_SYMBOL_GPL(x509_check_signature);
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/*
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* Check the new certificate against the ones in the trust keyring. If one of
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* those is the signing key and validates the new certificate, then mark the
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* new certificate as being trusted.
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*
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* Return 0 if the new certificate was successfully validated, 1 if we couldn't
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* find a matching parent certificate in the trusted list and an error if there
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* is a matching certificate but the signature check fails.
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*/
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static int x509_validate_trust(struct x509_certificate *cert,
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struct key *trust_keyring)
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{
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struct key *key;
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int ret = 1;
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if (!trust_keyring)
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return -EOPNOTSUPP;
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if (ca_keyid && !asymmetric_key_id_partial(cert->akid_skid, ca_keyid))
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return -EPERM;
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key = x509_request_asymmetric_key(trust_keyring,
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cert->akid_id, cert->akid_skid,
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false);
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if (!IS_ERR(key)) {
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if (!use_builtin_keys
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|| test_bit(KEY_FLAG_BUILTIN, &key->flags))
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ret = x509_check_signature(key->payload.data[asym_crypto],
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cert);
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key_put(key);
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}
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return ret;
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}
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/*
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* Attempt to parse a data blob for a key as an X509 certificate.
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*/
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static int x509_key_preparse(struct key_preparsed_payload *prep)
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{
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struct asymmetric_key_ids *kids;
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struct x509_certificate *cert;
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const char *q;
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size_t srlen, sulen;
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char *desc = NULL, *p;
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int ret;
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cert = x509_cert_parse(prep->data, prep->datalen);
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if (IS_ERR(cert))
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return PTR_ERR(cert);
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pr_devel("Cert Issuer: %s\n", cert->issuer);
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pr_devel("Cert Subject: %s\n", cert->subject);
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if (cert->pub->pkey_algo >= PKEY_ALGO__LAST ||
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cert->sig.pkey_algo >= PKEY_ALGO__LAST ||
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cert->sig.pkey_hash_algo >= PKEY_HASH__LAST ||
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!pkey_algo[cert->pub->pkey_algo] ||
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!pkey_algo[cert->sig.pkey_algo] ||
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!hash_algo_name[cert->sig.pkey_hash_algo]) {
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ret = -ENOPKG;
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goto error_free_cert;
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}
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pr_devel("Cert Key Algo: %s\n", pkey_algo_name[cert->pub->pkey_algo]);
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pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
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pr_devel("Cert Signature: %s + %s\n",
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pkey_algo_name[cert->sig.pkey_algo],
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hash_algo_name[cert->sig.pkey_hash_algo]);
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cert->pub->algo = pkey_algo[cert->pub->pkey_algo];
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cert->pub->id_type = PKEY_ID_X509;
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/* Check the signature on the key if it appears to be self-signed */
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if ((!cert->akid_skid && !cert->akid_id) ||
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asymmetric_key_id_same(cert->skid, cert->akid_skid) ||
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asymmetric_key_id_same(cert->id, cert->akid_id)) {
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ret = x509_check_signature(cert->pub, cert); /* self-signed */
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if (ret < 0)
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goto error_free_cert;
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} else if (!prep->trusted) {
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ret = x509_validate_trust(cert, get_system_trusted_keyring());
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if (ret)
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ret = x509_validate_trust(cert, get_ima_mok_keyring());
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if (!ret)
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prep->trusted = 1;
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}
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/* Propose a description */
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sulen = strlen(cert->subject);
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if (cert->raw_skid) {
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srlen = cert->raw_skid_size;
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q = cert->raw_skid;
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} else {
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srlen = cert->raw_serial_size;
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q = cert->raw_serial;
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}
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ret = -ENOMEM;
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desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
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if (!desc)
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goto error_free_cert;
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p = memcpy(desc, cert->subject, sulen);
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p += sulen;
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*p++ = ':';
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*p++ = ' ';
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p = bin2hex(p, q, srlen);
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*p = 0;
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kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
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if (!kids)
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goto error_free_desc;
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kids->id[0] = cert->id;
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kids->id[1] = cert->skid;
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/* We're pinning the module by being linked against it */
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__module_get(public_key_subtype.owner);
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prep->payload.data[asym_subtype] = &public_key_subtype;
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prep->payload.data[asym_key_ids] = kids;
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prep->payload.data[asym_crypto] = cert->pub;
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prep->description = desc;
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prep->quotalen = 100;
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/* We've finished with the certificate */
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cert->pub = NULL;
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cert->id = NULL;
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cert->skid = NULL;
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desc = NULL;
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ret = 0;
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error_free_desc:
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kfree(desc);
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error_free_cert:
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x509_free_certificate(cert);
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return ret;
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}
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static struct asymmetric_key_parser x509_key_parser = {
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.owner = THIS_MODULE,
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.name = "x509",
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.parse = x509_key_preparse,
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};
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/*
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* Module stuff
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*/
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static int __init x509_key_init(void)
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{
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return register_asymmetric_key_parser(&x509_key_parser);
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}
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static void __exit x509_key_exit(void)
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{
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unregister_asymmetric_key_parser(&x509_key_parser);
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}
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module_init(x509_key_init);
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module_exit(x509_key_exit);
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MODULE_DESCRIPTION("X.509 certificate parser");
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MODULE_LICENSE("GPL");
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