crypto/krb5: Implement the Camellia enctypes from rfc6803

Implement the camellia128-cts-cmac and camellia256-cts-cmac enctypes from
rfc6803.

Note that the test vectors in rfc6803 for encryption are incomplete,
lacking the key usage number needed to derive Ke and Ki, and there are
errata for this:

https://www.rfc-editor.org/errata_search.php?rfc=6803

Signed-off-by: David Howells <[e-mail]>
cc: Herbert Xu <[e-mail]>
cc: "David S. Miller" <[e-mail]>
cc: Chuck Lever <[e-mail]>
cc: Marc Dionne <[e-mail]>
cc: Eric Dumazet <[e-mail]>
cc: Jakub Kicinski <[e-mail]>
cc: Paolo Abeni <[e-mail]>
cc: Simon Horman <[e-mail]>
cc: [e-mail]
cc: [e-mail]
cc: [e-mail]
cc: [e-mail]

crypto/krb5/Kconfig

···
 	select CRYPTO_SKCIPHER
 	select CRYPTO_HASH_INFO
 	select CRYPTO_HMAC
+	select CRYPTO_CMAC
 	select CRYPTO_SHA1
 	select CRYPTO_SHA256
 	select CRYPTO_SHA512
 	select CRYPTO_CBC
 	select CRYPTO_CTS
 	select CRYPTO_AES
+	select CRYPTO_CAMELLIA
 	help
 	  Provide a library for provision of Kerberos-5-based crypto.  This is
 	  intended for network filesystems to use.

crypto/krb5/Makefile

···
 	krb5_api.o \
 	rfc3961_simplified.o \
 	rfc3962_aes.o \
+	rfc6803_camellia.o \
 	rfc8009_aes2.o
 
 obj-$(CONFIG_CRYPTO_KRB5) += krb5.o

crypto/krb5/internal.h

···
 extern const struct krb5_enctype krb5_aes256_cts_hmac_sha1_96;
 
 /*
+ * rfc6803_camellia.c
+ */
+extern const struct krb5_enctype krb5_camellia128_cts_cmac;
+extern const struct krb5_enctype krb5_camellia256_cts_cmac;
+
+/*
  * rfc8009_aes2.c
  */
 extern const struct krb5_enctype krb5_aes128_cts_hmac_sha256_128;

crypto/krb5/krb5_api.c

···
 	&krb5_aes256_cts_hmac_sha1_96,
 	&krb5_aes128_cts_hmac_sha256_128,
 	&krb5_aes256_cts_hmac_sha384_192,
+	&krb5_camellia128_cts_cmac,
+	&krb5_camellia256_cts_cmac,
 };
 
 /**

crypto/krb5/rfc6803_camellia.c

···
+// 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 ([e-mail])
+ */
+
+#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)
+			goto error;
+		ret = crypto_shash_finup(desc, data.data, data.len, K.data);
+		if (ret < 0)
+			goto error;
+
+		seg = min_t(size_t, result->len - offset, K.len);
+		memcpy(result->data + offset, K.data, seg);
+		offset += seg;
+	} while (offset < result->len);
+
+error:
+	kfree_sensitive(buffer);
+error_shash:
+	crypto_free_shash(shash);
+	return ret;
+}
+
+/*
+ * Calculate the pseudo-random function, PRF().
+ *
+ *	Kp = KDF-FEEDBACK-CMAC(protocol-key, "prf")
+ *	PRF = CMAC(Kp, octet-string)
+ *      [rfc6803 sec 6]
+ */
+static int rfc6803_calc_PRF(const struct krb5_enctype *krb5,
+			    const struct krb5_buffer *protocol_key,
+			    const struct krb5_buffer *octet_string,
+			    struct krb5_buffer *result,
+			    gfp_t gfp)
+{
+	static const struct krb5_buffer prfconstant = { 3, "prf" };
+	struct crypto_shash *shash;
+	struct krb5_buffer Kp;
+	struct shash_desc *desc;
+	size_t bsize;
+	void *buffer;
+	int ret;
+
+	Kp.len = krb5->prf_len;
+
+	shash = crypto_alloc_shash(krb5->cksum_name, 0, 0);
+	if (IS_ERR(shash))
+		return (PTR_ERR(shash) == -ENOENT) ? -ENOPKG : PTR_ERR(shash);
+
+	ret = -EINVAL;
+	if (result->len != crypto_shash_digestsize(shash))
+		goto out_shash;
+
+	ret = -ENOMEM;
+	bsize = krb5_shash_size(shash) +
+		krb5_digest_size(shash) +
+		crypto_roundup(Kp.len);
+	buffer = kzalloc(bsize, GFP_NOFS);
+	if (!buffer)
+		goto out_shash;
+
+	Kp.data = buffer +
+		krb5_shash_size(shash) +
+		krb5_digest_size(shash);
+
+	ret = rfc6803_calc_KDF_FEEDBACK_CMAC(krb5, protocol_key, &prfconstant,
+					     &Kp, gfp);
+	if (ret < 0)
+		goto out;
+
+	ret = crypto_shash_setkey(shash, Kp.data, Kp.len);
+	if (ret < 0)
+		goto out;
+
+	desc = buffer;
+	desc->tfm = shash;
+	ret = crypto_shash_init(desc);
+	if (ret < 0)
+		goto out;
+
+	ret = crypto_shash_finup(desc, octet_string->data, octet_string->len, result->data);
+	if (ret < 0)
+		goto out;
+
+out:
+	kfree_sensitive(buffer);
+out_shash:
+	crypto_free_shash(shash);
+	return ret;
+}
+
+
+static const struct krb5_crypto_profile rfc6803_crypto_profile = {
+	.calc_PRF		= rfc6803_calc_PRF,
+	.calc_Kc		= rfc6803_calc_KDF_FEEDBACK_CMAC,
+	.calc_Ke		= rfc6803_calc_KDF_FEEDBACK_CMAC,
+	.calc_Ki		= rfc6803_calc_KDF_FEEDBACK_CMAC,
+	.derive_encrypt_keys	= authenc_derive_encrypt_keys,
+	.load_encrypt_keys	= authenc_load_encrypt_keys,
+	.derive_checksum_key	= rfc3961_derive_checksum_key,
+	.load_checksum_key	= rfc3961_load_checksum_key,
+	.encrypt		= krb5_aead_encrypt,
+	.decrypt		= krb5_aead_decrypt,
+	.get_mic		= rfc3961_get_mic,
+	.verify_mic		= rfc3961_verify_mic,
+};
+
+const struct krb5_enctype krb5_camellia128_cts_cmac = {
+	.etype		= KRB5_ENCTYPE_CAMELLIA128_CTS_CMAC,
+	.ctype		= KRB5_CKSUMTYPE_CMAC_CAMELLIA128,
+	.name		= "camellia128-cts-cmac",
+	.encrypt_name	= "krb5enc(cmac(camellia),cts(cbc(camellia)))",
+	.cksum_name	= "cmac(camellia)",
+	.hash_name	= NULL,
+	.derivation_enc	= "cts(cbc(camellia))",
+	.key_bytes	= 16,
+	.key_len	= 16,
+	.Kc_len		= 16,
+	.Ke_len		= 16,
+	.Ki_len		= 16,
+	.block_len	= 16,
+	.conf_len	= 16,
+	.cksum_len	= 16,
+	.hash_len	= 16,
+	.prf_len	= 16,
+	.keyed_cksum	= true,
+	.random_to_key	= NULL, /* Identity */
+	.profile	= &rfc6803_crypto_profile,
+};
+
+const struct krb5_enctype krb5_camellia256_cts_cmac = {
+	.etype		= KRB5_ENCTYPE_CAMELLIA256_CTS_CMAC,
+	.ctype		= KRB5_CKSUMTYPE_CMAC_CAMELLIA256,
+	.name		= "camellia256-cts-cmac",
+	.encrypt_name	= "krb5enc(cmac(camellia),cts(cbc(camellia)))",
+	.cksum_name	= "cmac(camellia)",
+	.hash_name	= NULL,
+	.derivation_enc	= "cts(cbc(camellia))",
+	.key_bytes	= 32,
+	.key_len	= 32,
+	.Kc_len		= 32,
+	.Ke_len		= 32,
+	.Ki_len		= 32,
+	.block_len	= 16,
+	.conf_len	= 16,
+	.cksum_len	= 16,
+	.hash_len	= 16,
+	.prf_len	= 16,
+	.keyed_cksum	= true,
+	.random_to_key	= NULL, /* Identity */
+	.profile	= &rfc6803_crypto_profile,
+};

include/crypto/krb5.h

···
 #define KRB5_ENCTYPE_AES256_CTS_HMAC_SHA384_192	0x0014
 #define KRB5_ENCTYPE_ARCFOUR_HMAC		0x0017
 #define KRB5_ENCTYPE_ARCFOUR_HMAC_EXP		0x0018
+#define KRB5_ENCTYPE_CAMELLIA128_CTS_CMAC	0x0019
+#define KRB5_ENCTYPE_CAMELLIA256_CTS_CMAC	0x001a
 #define KRB5_ENCTYPE_UNKNOWN			0x01ff
 
 #define KRB5_CKSUMTYPE_CRC32			0x0001
···
 #define KRB5_CKSUMTYPE_HMAC_SHA1_DES3		0x000c
 #define KRB5_CKSUMTYPE_HMAC_SHA1_96_AES128	0x000f
 #define KRB5_CKSUMTYPE_HMAC_SHA1_96_AES256	0x0010
+#define KRB5_CKSUMTYPE_CMAC_CAMELLIA128		0x0011
+#define KRB5_CKSUMTYPE_CMAC_CAMELLIA256		0x0012
 #define KRB5_CKSUMTYPE_HMAC_SHA256_128_AES128	0x0013
 #define KRB5_CKSUMTYPE_HMAC_SHA384_192_AES256	0x0014
 #define KRB5_CKSUMTYPE_HMAC_MD5_ARCFOUR		-138 /* Microsoft md5 hmac cksumtype */