crypto/krb5: Implement the AES enctypes from rfc8009

Implement the aes128-cts-hmac-sha256-128 and aes256-cts-hmac-sha384-192
enctypes from rfc8009, overriding the rfc3961 kerberos 5 simplified crypto
scheme.

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_HASH_INFO
 	select CRYPTO_HMAC
 	select CRYPTO_SHA1
+	select CRYPTO_SHA256
+	select CRYPTO_SHA512
 	select CRYPTO_CBC
 	select CRYPTO_CTS
 	select CRYPTO_AES

crypto/krb5/Makefile

···
 	krb5_kdf.o \
 	krb5_api.o \
 	rfc3961_simplified.o \
-	rfc3962_aes.o
+	rfc3962_aes.o \
+	rfc8009_aes2.o
 
 obj-$(CONFIG_CRYPTO_KRB5) += krb5.o

crypto/krb5/internal.h

···
  */
 extern const struct krb5_enctype krb5_aes128_cts_hmac_sha1_96;
 extern const struct krb5_enctype krb5_aes256_cts_hmac_sha1_96;
+
+/*
+ * rfc8009_aes2.c
+ */
+extern const struct krb5_enctype krb5_aes128_cts_hmac_sha256_128;
+extern const struct krb5_enctype krb5_aes256_cts_hmac_sha384_192;

crypto/krb5/krb5_api.c

···
 static const struct krb5_enctype *const krb5_supported_enctypes[] = {
 	&krb5_aes128_cts_hmac_sha1_96,
 	&krb5_aes256_cts_hmac_sha1_96,
+	&krb5_aes128_cts_hmac_sha256_128,
+	&krb5_aes256_cts_hmac_sha384_192,
 };
 
 /**

crypto/krb5/rfc8009_aes2.c

···
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* rfc8009 AES Encryption with HMAC-SHA2 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 <crypto/authenc.h>
+#include "internal.h"
+
+static const struct krb5_buffer rfc8009_no_context = { .len = 0, .data = "" };
+
+/*
+ * Calculate the key derivation function KDF-HMAC-SHA2(key, label, [context,] k)
+ *
+ *	KDF-HMAC-SHA2(key, label, [context,] k) = k-truncate(K1)
+ *
+ *	Using the appropriate one of:
+ *		K1 = HMAC-SHA-256(key, 0x00000001 | label | 0x00 | k)
+ *		K1 = HMAC-SHA-384(key, 0x00000001 | label | 0x00 | k)
+ *		K1 = HMAC-SHA-256(key, 0x00000001 | label | 0x00 | context | k)
+ *		K1 = HMAC-SHA-384(key, 0x00000001 | label | 0x00 | context | k)
+ *	[rfc8009 sec 3]
+ */
+static int rfc8009_calc_KDF_HMAC_SHA2(const struct krb5_enctype *krb5,
+				      const struct krb5_buffer *key,
+				      const struct krb5_buffer *label,
+				      const struct krb5_buffer *context,
+				      unsigned int k,
+				      struct krb5_buffer *result,
+				      gfp_t gfp)
+{
+	struct crypto_shash *shash;
+	struct krb5_buffer K1, data;
+	struct shash_desc *desc;
+	__be32 tmp;
+	size_t bsize;
+	void *buffer;
+	u8 *p;
+	int ret = -ENOMEM;
+
+	if (WARN_ON(result->len != k / 8))
+		return -EINVAL;
+
+	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 = -EINVAL;
+	if (WARN_ON(crypto_shash_digestsize(shash) * 8 < k))
+		goto error_shash;
+
+	ret = -ENOMEM;
+	data.len = 4 + label->len + 1 + context->len + 4;
+	bsize = krb5_shash_size(shash) +
+		krb5_digest_size(shash) +
+		crypto_roundup(data.len);
+	buffer = kzalloc(bsize, GFP_NOFS);
+	if (!buffer)
+		goto error_shash;
+
+	desc = buffer;
+	desc->tfm = shash;
+	ret = crypto_shash_init(desc);
+	if (ret < 0)
+		goto error;
+
+	p = data.data = buffer +
+		krb5_shash_size(shash) +
+		krb5_digest_size(shash);
+	*(__be32 *)p = htonl(0x00000001);
+	p += 4;
+	memcpy(p, label->data, label->len);
+	p += label->len;
+	*p++ = 0;
+	memcpy(p, context->data, context->len);
+	p += context->len;
+	tmp = htonl(k);
+	memcpy(p, &tmp, 4);
+	p += 4;
+
+	ret = -EINVAL;
+	if (WARN_ON(p - (u8 *)data.data != data.len))
+		goto error;
+
+	K1.len = crypto_shash_digestsize(shash);
+	K1.data = buffer +
+		krb5_shash_size(shash);
+
+	ret = crypto_shash_finup(desc, data.data, data.len, K1.data);
+	if (ret < 0)
+		goto error;
+
+	memcpy(result->data, K1.data, result->len);
+
+error:
+	kfree_sensitive(buffer);
+error_shash:
+	crypto_free_shash(shash);
+	return ret;
+}
+
+/*
+ * Calculate the pseudo-random function, PRF().
+ *
+ *	PRF = KDF-HMAC-SHA2(input-key, "prf", octet-string, 256)
+ *	PRF = KDF-HMAC-SHA2(input-key, "prf", octet-string, 384)
+ *
+ *      The "prfconstant" used in the PRF operation is the three-octet string
+ *      "prf".
+ *      [rfc8009 sec 5]
+ */
+static int rfc8009_calc_PRF(const struct krb5_enctype *krb5,
+			    const struct krb5_buffer *input_key,
+			    const struct krb5_buffer *octet_string,
+			    struct krb5_buffer *result,
+			    gfp_t gfp)
+{
+	static const struct krb5_buffer prfconstant = { 3, "prf" };
+
+	return rfc8009_calc_KDF_HMAC_SHA2(krb5, input_key, &prfconstant,
+					  octet_string, krb5->prf_len * 8,
+					  result, gfp);
+}
+
+/*
+ * Derive Ke.
+ *	Ke = KDF-HMAC-SHA2(base-key, usage | 0xAA, 128)
+ *	Ke = KDF-HMAC-SHA2(base-key, usage | 0xAA, 256)
+ *      [rfc8009 sec 5]
+ */
+static int rfc8009_calc_Ke(const struct krb5_enctype *krb5,
+			   const struct krb5_buffer *base_key,
+			   const struct krb5_buffer *usage_constant,
+			   struct krb5_buffer *result,
+			   gfp_t gfp)
+{
+	return rfc8009_calc_KDF_HMAC_SHA2(krb5, base_key, usage_constant,
+					  &rfc8009_no_context, krb5->key_bytes * 8,
+					  result, gfp);
+}
+
+/*
+ * Derive Kc/Ki
+ *	Kc = KDF-HMAC-SHA2(base-key, usage | 0x99, 128)
+ *	Ki = KDF-HMAC-SHA2(base-key, usage | 0x55, 128)
+ *	Kc = KDF-HMAC-SHA2(base-key, usage | 0x99, 192)
+ *	Ki = KDF-HMAC-SHA2(base-key, usage | 0x55, 192)
+ *      [rfc8009 sec 5]
+ */
+static int rfc8009_calc_Ki(const struct krb5_enctype *krb5,
+			   const struct krb5_buffer *base_key,
+			   const struct krb5_buffer *usage_constant,
+			   struct krb5_buffer *result,
+			   gfp_t gfp)
+{
+	return rfc8009_calc_KDF_HMAC_SHA2(krb5, base_key, usage_constant,
+					  &rfc8009_no_context, krb5->cksum_len * 8,
+					  result, gfp);
+}
+
+/*
+ * Apply encryption and checksumming functions to a message.  Unlike for
+ * RFC3961, for RFC8009, we have to chuck the starting IV into the hash first.
+ */
+static ssize_t rfc8009_encrypt(const struct krb5_enctype *krb5,
+			       struct crypto_aead *aead,
+			       struct scatterlist *sg, unsigned int nr_sg, size_t sg_len,
+			       size_t data_offset, size_t data_len,
+			       bool preconfounded)
+{
+	struct aead_request *req;
+	struct scatterlist bsg[2];
+	ssize_t ret, done;
+	size_t bsize, base_len, secure_offset, secure_len, pad_len, cksum_offset;
+	void *buffer;
+	u8 *iv, *ad;
+
+	if (WARN_ON(data_offset != krb5->conf_len))
+		return -EINVAL; /* Data is in wrong place */
+
+	secure_offset	= 0;
+	base_len	= krb5->conf_len + data_len;
+	pad_len		= 0;
+	secure_len	= base_len + pad_len;
+	cksum_offset	= secure_len;
+	if (WARN_ON(cksum_offset + krb5->cksum_len > sg_len))
+		return -EFAULT;
+
+	bsize = krb5_aead_size(aead) +
+		krb5_aead_ivsize(aead) * 2;
+	buffer = kzalloc(bsize, GFP_NOFS);
+	if (!buffer)
+		return -ENOMEM;
+
+	req = buffer;
+	iv = buffer + krb5_aead_size(aead);
+	ad = buffer + krb5_aead_size(aead) + krb5_aead_ivsize(aead);
+
+	/* Insert the confounder into the buffer */
+	ret = -EFAULT;
+	if (!preconfounded) {
+		get_random_bytes(buffer, krb5->conf_len);
+		done = sg_pcopy_from_buffer(sg, nr_sg, buffer, krb5->conf_len,
+					    secure_offset);
+		if (done != krb5->conf_len)
+			goto error;
+	}
+
+	/* We may need to pad out to the crypto blocksize. */
+	if (pad_len) {
+		done = sg_zero_buffer(sg, nr_sg, pad_len, data_offset + data_len);
+		if (done != pad_len)
+			goto error;
+	}
+
+	/* We need to include the starting IV in the hash. */
+	sg_init_table(bsg, 2);
+	sg_set_buf(&bsg[0], ad, krb5_aead_ivsize(aead));
+	sg_chain(bsg, 2, sg);
+
+	/* Hash and encrypt the message. */
+	aead_request_set_tfm(req, aead);
+	aead_request_set_callback(req, 0, NULL, NULL);
+	aead_request_set_ad(req, krb5_aead_ivsize(aead));
+	aead_request_set_crypt(req, bsg, bsg, secure_len, iv);
+	ret = crypto_aead_encrypt(req);
+	if (ret < 0)
+		goto error;
+
+	ret = secure_len + krb5->cksum_len;
+
+error:
+	kfree_sensitive(buffer);
+	return ret;
+}
+
+/*
+ * Apply decryption and checksumming functions to a message.  Unlike for
+ * RFC3961, for RFC8009, we have to chuck the starting IV into the hash first.
+ *
+ * The offset and length are updated to reflect the actual content of the
+ * encrypted region.
+ */
+static int rfc8009_decrypt(const struct krb5_enctype *krb5,
+			   struct crypto_aead *aead,
+			   struct scatterlist *sg, unsigned int nr_sg,
+			   size_t *_offset, size_t *_len)
+{
+	struct aead_request *req;
+	struct scatterlist bsg[2];
+	size_t bsize;
+	void *buffer;
+	int ret;
+	u8 *iv, *ad;
+
+	if (WARN_ON(*_offset != 0))
+		return -EINVAL; /* Can't set offset on aead */
+
+	if (*_len < krb5->conf_len + krb5->cksum_len)
+		return -EPROTO;
+
+	bsize = krb5_aead_size(aead) +
+		krb5_aead_ivsize(aead) * 2;
+	buffer = kzalloc(bsize, GFP_NOFS);
+	if (!buffer)
+		return -ENOMEM;
+
+	req = buffer;
+	iv = buffer + krb5_aead_size(aead);
+	ad = buffer + krb5_aead_size(aead) + krb5_aead_ivsize(aead);
+
+	/* We need to include the starting IV in the hash. */
+	sg_init_table(bsg, 2);
+	sg_set_buf(&bsg[0], ad, krb5_aead_ivsize(aead));
+	sg_chain(bsg, 2, sg);
+
+	/* Decrypt the message and verify its checksum. */
+	aead_request_set_tfm(req, aead);
+	aead_request_set_callback(req, 0, NULL, NULL);
+	aead_request_set_ad(req, krb5_aead_ivsize(aead));
+	aead_request_set_crypt(req, bsg, bsg, *_len, iv);
+	ret = crypto_aead_decrypt(req);
+	if (ret < 0)
+		goto error;
+
+	/* Adjust the boundaries of the data. */
+	*_offset += krb5->conf_len;
+	*_len -= krb5->conf_len + krb5->cksum_len;
+	ret = 0;
+
+error:
+	kfree_sensitive(buffer);
+	return ret;
+}
+
+static const struct krb5_crypto_profile rfc8009_crypto_profile = {
+	.calc_PRF		= rfc8009_calc_PRF,
+	.calc_Kc		= rfc8009_calc_Ki,
+	.calc_Ke		= rfc8009_calc_Ke,
+	.calc_Ki		= rfc8009_calc_Ki,
+	.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		= rfc8009_encrypt,
+	.decrypt		= rfc8009_decrypt,
+	.get_mic		= rfc3961_get_mic,
+	.verify_mic		= rfc3961_verify_mic,
+};
+
+const struct krb5_enctype krb5_aes128_cts_hmac_sha256_128 = {
+	.etype		= KRB5_ENCTYPE_AES128_CTS_HMAC_SHA256_128,
+	.ctype		= KRB5_CKSUMTYPE_HMAC_SHA256_128_AES128,
+	.name		= "aes128-cts-hmac-sha256-128",
+	.encrypt_name	= "authenc(hmac(sha256),cts(cbc(aes)))",
+	.cksum_name	= "hmac(sha256)",
+	.hash_name	= "sha256",
+	.derivation_enc	= "cts(cbc(aes))",
+	.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	= 20,
+	.prf_len	= 32,
+	.keyed_cksum	= true,
+	.random_to_key	= NULL, /* Identity */
+	.profile	= &rfc8009_crypto_profile,
+};
+
+const struct krb5_enctype krb5_aes256_cts_hmac_sha384_192 = {
+	.etype		= KRB5_ENCTYPE_AES256_CTS_HMAC_SHA384_192,
+	.ctype		= KRB5_CKSUMTYPE_HMAC_SHA384_192_AES256,
+	.name		= "aes256-cts-hmac-sha384-192",
+	.encrypt_name	= "authenc(hmac(sha384),cts(cbc(aes)))",
+	.cksum_name	= "hmac(sha384)",
+	.hash_name	= "sha384",
+	.derivation_enc	= "cts(cbc(aes))",
+	.key_bytes	= 32,
+	.key_len	= 32,
+	.Kc_len		= 24,
+	.Ke_len		= 32,
+	.Ki_len		= 24,
+	.block_len	= 16,
+	.conf_len	= 16,
+	.cksum_len	= 24,
+	.hash_len	= 20,
+	.prf_len	= 48,
+	.keyed_cksum	= true,
+	.random_to_key	= NULL, /* Identity */
+	.profile	= &rfc8009_crypto_profile,
+};

include/crypto/krb5.h

···
 #define KRB5_ENCTYPE_DES3_CBC_SHA1		0x0010
 #define KRB5_ENCTYPE_AES128_CTS_HMAC_SHA1_96	0x0011
 #define KRB5_ENCTYPE_AES256_CTS_HMAC_SHA1_96	0x0012
+#define KRB5_ENCTYPE_AES128_CTS_HMAC_SHA256_128	0x0013
+#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_UNKNOWN			0x01ff
···
 #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_HMAC_SHA256_128_AES128	0x0013
+#define KRB5_CKSUMTYPE_HMAC_SHA384_192_AES256	0x0014
 #define KRB5_CKSUMTYPE_HMAC_MD5_ARCFOUR		-138 /* Microsoft md5 hmac cksumtype */
 
 /*