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![Eric Biggers](/assets/img/avatar_default.png)
->pkey_algo used to be an enum, but was changed to a string by commit4e8ae72a75
("X.509: Make algo identifiers text instead of enum"). But two comparisons were not updated. Fix them to use strcmp(). This bug broke signature verification in certain configurations, depending on whether the string constants were deduplicated or not. Fixes:4e8ae72a75
("X.509: Make algo identifiers text instead of enum") Cc: <stable@vger.kernel.org> # v4.6+ Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: David Howells <dhowells@redhat.com>
275 lines
6.4 KiB
C
275 lines
6.4 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 <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 "x509_parser.h"
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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 public_key_signature *sig = cert->sig;
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struct crypto_shash *tfm;
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struct shash_desc *desc;
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size_t desc_size;
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int ret;
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pr_devel("==>%s()\n", __func__);
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if (!cert->pub->pkey_algo)
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cert->unsupported_key = true;
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if (!sig->pkey_algo)
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cert->unsupported_sig = true;
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/* We check the hash if we can - even if we can't then verify it */
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if (!sig->hash_algo) {
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cert->unsupported_sig = true;
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return 0;
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}
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sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
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if (!sig->s)
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return -ENOMEM;
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sig->s_size = cert->raw_sig_size;
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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(sig->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_sig = true;
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return 0;
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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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sig->digest_size = crypto_shash_digestsize(tfm);
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ret = -ENOMEM;
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sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
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if (!sig->digest)
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goto error;
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desc = kzalloc(desc_size, GFP_KERNEL);
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if (!desc)
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goto error;
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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_digest(desc, cert->tbs, cert->tbs_size, sig->digest);
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if (ret < 0)
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goto error_2;
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ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
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if (ret == -EKEYREJECTED) {
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pr_err("Cert %*phN is blacklisted\n",
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sig->digest_size, sig->digest);
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cert->blacklisted = true;
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ret = 0;
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}
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error_2:
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kfree(desc);
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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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/*
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* Check for self-signedness in an X.509 cert and if found, check the signature
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* immediately if we can.
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*/
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int x509_check_for_self_signed(struct x509_certificate *cert)
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{
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int ret = 0;
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pr_devel("==>%s()\n", __func__);
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if (cert->raw_subject_size != cert->raw_issuer_size ||
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memcmp(cert->raw_subject, cert->raw_issuer,
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cert->raw_issuer_size) != 0)
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goto not_self_signed;
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if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
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/* If the AKID is present it may have one or two parts. If
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* both are supplied, both must match.
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*/
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bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
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bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
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if (!a && !b)
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goto not_self_signed;
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ret = -EKEYREJECTED;
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if (((a && !b) || (b && !a)) &&
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cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
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goto out;
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}
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ret = -EKEYREJECTED;
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if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
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goto out;
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ret = public_key_verify_signature(cert->pub, cert->sig);
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if (ret < 0) {
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if (ret == -ENOPKG) {
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cert->unsupported_sig = true;
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ret = 0;
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}
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goto out;
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}
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pr_devel("Cert Self-signature verified");
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cert->self_signed = true;
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out:
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pr_devel("<==%s() = %d\n", __func__, ret);
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return ret;
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not_self_signed:
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pr_devel("<==%s() = 0 [not]\n", __func__);
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return 0;
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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->unsupported_key) {
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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", 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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cert->pub->id_type = "X509";
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if (cert->unsupported_sig) {
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public_key_signature_free(cert->sig);
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cert->sig = NULL;
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} else {
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pr_devel("Cert Signature: %s + %s\n",
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cert->sig->pkey_algo, cert->sig->hash_algo);
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}
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/* Don't permit addition of blacklisted keys */
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ret = -EKEYREJECTED;
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if (cert->blacklisted)
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goto error_free_cert;
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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->payload.data[asym_auth] = cert->sig;
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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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cert->sig = 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_AUTHOR("Red Hat, Inc.");
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MODULE_LICENSE("GPL");
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