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/* Module signature checker
*
* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/err.h>
#include <keys/system_keyring.h>
#include <crypto/public_key.h>
#include <crypto/pkcs7.h>
#include "module-internal.h"
/*
* Module signature information block.
*
* The constituents of the signature section are, in order:
*
* - Signer's name
* - Key identifier
* - Signature data
* - Information block
*/
struct module_signature {
u8 algo; /* Public-key crypto algorithm [0] */
u8 hash; /* Digest algorithm [0] */
u8 id_type; /* Key identifier type [PKEY_ID_PKCS7] */
u8 signer_len; /* Length of signer's name [0] */
u8 key_id_len; /* Length of key identifier [0] */
u8 __pad[3];
__be32 sig_len; /* Length of signature data */
};
/*
* Verify a PKCS#7-based signature on a module.
*/
static int mod_verify_pkcs7(const void *mod, unsigned long modlen,
const void *raw_pkcs7, size_t pkcs7_len)
{
struct pkcs7_message *pkcs7;
bool trusted;
int ret;
pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
if (IS_ERR(pkcs7))
return PTR_ERR(pkcs7);
/* The data should be detached - so we need to supply it. */
if (pkcs7_supply_detached_data(pkcs7, mod, modlen) < 0) {
pr_err("PKCS#7 signature with non-detached data\n");
ret = -EBADMSG;
goto error;
}
ret = pkcs7_verify(pkcs7);
if (ret < 0)
goto error;
ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
if (ret < 0)
goto error;
if (!trusted) {
pr_err("PKCS#7 signature not signed with a trusted key\n");
ret = -ENOKEY;
}
error:
pkcs7_free_message(pkcs7);
pr_devel("<==%s() = %d\n", __func__, ret);
return ret;
}
/*
* Verify the signature on a module.
*/
int mod_verify_sig(const void *mod, unsigned long *_modlen)
{
struct module_signature ms;
size_t modlen = *_modlen, sig_len;
pr_devel("==>%s(,%zu)\n", __func__, modlen);
if (modlen <= sizeof(ms))
return -EBADMSG;
memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
modlen -= sizeof(ms);
sig_len = be32_to_cpu(ms.sig_len);
if (sig_len >= modlen)
return -EBADMSG;
modlen -= sig_len;
*_modlen = modlen;
if (ms.id_type != PKEY_ID_PKCS7) {
pr_err("Module is not signed with expected PKCS#7 message\n");
return -ENOPKG;
}
if (ms.algo != 0 ||
ms.hash != 0 ||
ms.signer_len != 0 ||
ms.key_id_len != 0 ||
ms.__pad[0] != 0 ||
ms.__pad[1] != 0 ||
ms.__pad[2] != 0) {
pr_err("PKCS#7 signature info has unexpected non-zero params\n");
return -EBADMSG;
}
return mod_verify_pkcs7(mod, modlen, mod + modlen, sig_len);
}
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