crypto/krb5/rfc6803_camellia.c

Source file repositories/reference/linux-study-clean/crypto/krb5/rfc6803_camellia.c

File Facts

System
Linux kernel
Corpus path
crypto/krb5/rfc6803_camellia.c
Extension
.c
Size
5845 bytes
Lines
238
Domain
Kernel Services
Bucket
crypto
Inferred role
Kernel Services: implementation source
Status
source implementation candidate

Why This File Exists

Shared kernel service surface used by multiple subsystems, including helpers, cryptography, virtualization support, and async I/O infrastructure.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-or-later
/* rfc6803 Camellia Encryption for Kerberos 5
 *
 * Copyright (C) 2025 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/slab.h>
#include "internal.h"

/*
 * Calculate the key derivation function KDF-FEEDBACK_CMAC(key, constant)
 *
 *	n = ceiling(k / 128)
 *	K(0) = zeros
 *	K(i) = CMAC(key, K(i-1) | i | constant | 0x00 | k)
 *	DR(key, constant) = k-truncate(K(1) | K(2) | ... | K(n))
 *	KDF-FEEDBACK-CMAC(key, constant) = random-to-key(DR(key, constant))
 *
 *	[rfc6803 sec 3]
 */
static int rfc6803_calc_KDF_FEEDBACK_CMAC(const struct krb5_enctype *krb5,
					  const struct krb5_buffer *key,
					  const struct krb5_buffer *constant,
					  struct krb5_buffer *result,
					  gfp_t gfp)
{
	struct crypto_shash *shash;
	struct krb5_buffer K, data;
	struct shash_desc *desc;
	__be32 tmp;
	size_t bsize, offset, seg;
	void *buffer;
	u32 i = 0, k = result->len * 8;
	u8 *p;
	int ret = -ENOMEM;

	shash = crypto_alloc_shash(krb5->cksum_name, 0, 0);
	if (IS_ERR(shash))
		return (PTR_ERR(shash) == -ENOENT) ? -ENOPKG : PTR_ERR(shash);
	ret = crypto_shash_setkey(shash, key->data, key->len);
	if (ret < 0)
		goto error_shash;

	ret = -ENOMEM;
	K.len = crypto_shash_digestsize(shash);
	data.len = K.len + 4 + constant->len + 1 + 4;
	bsize = krb5_shash_size(shash) +
		krb5_digest_size(shash) +
		crypto_roundup(K.len) +
		crypto_roundup(data.len);
	buffer = kzalloc(bsize, GFP_NOFS);
	if (!buffer)
		goto error_shash;

	desc = buffer;
	desc->tfm = shash;

	K.data = buffer +
		krb5_shash_size(shash) +
		krb5_digest_size(shash);
	data.data = buffer +
		krb5_shash_size(shash) +
		krb5_digest_size(shash) +
		crypto_roundup(K.len);

	p = data.data + K.len + 4;
	memcpy(p, constant->data, constant->len);
	p += constant->len;
	*p++ = 0x00;
	tmp = htonl(k);
	memcpy(p, &tmp, 4);
	p += 4;

	ret = -EINVAL;
	if (WARN_ON(p - (u8 *)data.data != data.len))
		goto error;

	offset = 0;
	do {
		i++;
		p = data.data;
		memcpy(p, K.data, K.len);
		p += K.len;
		*(__be32 *)p = htonl(i);

		ret = crypto_shash_init(desc);
		if (ret < 0)

Annotation

Implementation Notes