crypto/krb5/krb5_api.c - pub/scm/linux/kernel/git/mkl/linux-can - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /* Kerberos 5 crypto library.
  *
  * 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/module.h>
 #include <linux/export.h>
 #include <linux/kernel.h>
 #include "internal.h"

 MODULE_DESCRIPTION("Kerberos 5 crypto");
 MODULE_AUTHOR("Red Hat, Inc.");
 MODULE_LICENSE("GPL");

 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,
 	&krb5_camellia128_cts_cmac,
 	&krb5_camellia256_cts_cmac,
 };

 /**
  * crypto_krb5_find_enctype - Find the handler for a Kerberos5 encryption type
  * @enctype: The standard Kerberos encryption type number
  *
  * Look up a Kerberos encryption type by number.  If successful, returns a
  * pointer to the type tables; returns NULL otherwise.
  */
 const struct krb5_enctype *crypto_krb5_find_enctype(u32 enctype)
 {
 	const struct krb5_enctype *krb5;
 	size_t i;

 	for (i = 0; i < ARRAY_SIZE(krb5_supported_enctypes); i++) {
 		krb5 = krb5_supported_enctypes[i];
 		if (krb5->etype == enctype)
 			return krb5;
 	}

 	return NULL;
 }
 EXPORT_SYMBOL(crypto_krb5_find_enctype);

 /**
  * crypto_krb5_how_much_buffer - Work out how much buffer is required for an amount of data
  * @krb5: The encoding to use.
  * @mode: The mode in which to operated (checksum/encrypt)
  * @data_size: How much data we want to allow for
  * @_offset: Where to place the offset into the buffer
  *
  * Calculate how much buffer space is required to wrap a given amount of data.
  * This allows for a confounder, padding and checksum as appropriate.  The
  * amount of buffer required is returned and the offset into the buffer at
  * which the data will start is placed in *_offset.
  */
 size_t crypto_krb5_how_much_buffer(const struct krb5_enctype *krb5,
 				   enum krb5_crypto_mode mode,
 				   size_t data_size, size_t *_offset)
 {
 	switch (mode) {
 	case KRB5_CHECKSUM_MODE:
 		*_offset = krb5->cksum_len;
 		return krb5->cksum_len + data_size;

 	case KRB5_ENCRYPT_MODE:
 		*_offset = krb5->conf_len;
 		return krb5->conf_len + data_size + krb5->cksum_len;

 	default:
 		WARN_ON(1);
 		*_offset = 0;
 		return 0;
 	}
 }
 EXPORT_SYMBOL(crypto_krb5_how_much_buffer);

 /**
  * crypto_krb5_how_much_data - Work out how much data can fit in an amount of buffer
  * @krb5: The encoding to use.
  * @mode: The mode in which to operated (checksum/encrypt)
  * @_buffer_size: How much buffer we want to allow for (may be reduced)
  * @_offset: Where to place the offset into the buffer
  *
  * Calculate how much data can be fitted into given amount of buffer.  This
  * allows for a confounder, padding and checksum as appropriate.  The amount of
  * data that will fit is returned, the amount of buffer required is shrunk to
  * allow for alignment and the offset into the buffer at which the data will
  * start is placed in *_offset.
  */
 size_t crypto_krb5_how_much_data(const struct krb5_enctype *krb5,
 				 enum krb5_crypto_mode mode,
 				 size_t *_buffer_size, size_t *_offset)
 {
 	size_t buffer_size = *_buffer_size, data_size;

 	switch (mode) {
 	case KRB5_CHECKSUM_MODE:
 		if (WARN_ON(buffer_size < krb5->cksum_len + 1))
 			goto bad;
 		*_offset = krb5->cksum_len;
 		return buffer_size - krb5->cksum_len;

 	case KRB5_ENCRYPT_MODE:
 		if (WARN_ON(buffer_size < krb5->conf_len + 1 + krb5->cksum_len))
 			goto bad;
 		data_size = buffer_size - krb5->cksum_len;
 		*_offset = krb5->conf_len;
 		return data_size - krb5->conf_len;

 	default:
 		WARN_ON(1);
 		goto bad;
 	}

 bad:
 	*_offset = 0;
 	return 0;
 }
 EXPORT_SYMBOL(crypto_krb5_how_much_data);

 /**
  * crypto_krb5_where_is_the_data - Find the data in a decrypted message
  * @krb5: The encoding to use.
  * @mode: Mode of operation
  * @_offset: Offset of the secure blob in the buffer; updated to data offset.
  * @_len: The length of the secure blob; updated to data length.
  *
  * Find the offset and size of the data in a secure message so that this
  * information can be used in the metadata buffer which will get added to the
  * digest by crypto_krb5_verify_mic().
  */
 void crypto_krb5_where_is_the_data(const struct krb5_enctype *krb5,
 				   enum krb5_crypto_mode mode,
 				   size_t *_offset, size_t *_len)
 {
 	switch (mode) {
 	case KRB5_CHECKSUM_MODE:
 		*_offset += krb5->cksum_len;
 		*_len -= krb5->cksum_len;
 		return;
 	case KRB5_ENCRYPT_MODE:
 		*_offset += krb5->conf_len;
 		*_len -= krb5->conf_len + krb5->cksum_len;
 		return;
 	default:
 		WARN_ON_ONCE(1);
 		return;
 	}
 }
 EXPORT_SYMBOL(crypto_krb5_where_is_the_data);

 /*
  * Prepare the encryption with derived key data.
  */
 struct crypto_aead *krb5_prepare_encryption(const struct krb5_enctype *krb5,
 					    const struct krb5_buffer *keys,
 					    gfp_t gfp)
 {
 	struct crypto_aead *ci = NULL;
 	int ret = -ENOMEM;

 	ci = crypto_alloc_aead(krb5->encrypt_name, 0, 0);
 	if (IS_ERR(ci)) {
 		ret = PTR_ERR(ci);
 		if (ret == -ENOENT)
 			ret = -ENOPKG;
 		goto err;
 	}

 	ret = crypto_aead_setkey(ci, keys->data, keys->len);
 	if (ret < 0) {
 		pr_err("Couldn't set AEAD key %s: %d\n", krb5->encrypt_name, ret);
 		goto err_ci;
 	}

 	ret = crypto_aead_setauthsize(ci, krb5->cksum_len);
 	if (ret < 0) {
 		pr_err("Couldn't set AEAD authsize %s: %d\n", krb5->encrypt_name, ret);
 		goto err_ci;
 	}

 	return ci;
 err_ci:
 	crypto_free_aead(ci);
 err:
 	return ERR_PTR(ret);
 }

 /**
  * crypto_krb5_prepare_encryption - Prepare AEAD crypto object for encryption-mode
  * @krb5: The encoding to use.
  * @TK: The transport key to use.
  * @usage: The usage constant for key derivation.
  * @gfp: Allocation flags.
  *
  * Allocate a crypto object that does all the necessary crypto, key it and set
  * its parameters and return the crypto handle to it.  This can then be used to
  * dispatch encrypt and decrypt operations.
  */
 struct crypto_aead *crypto_krb5_prepare_encryption(const struct krb5_enctype *krb5,
 						   const struct krb5_buffer *TK,
 						   u32 usage, gfp_t gfp)
 {
 	struct crypto_aead *ci = NULL;
 	struct krb5_buffer keys = {};
 	int ret;

 	ret = krb5->profile->derive_encrypt_keys(krb5, TK, usage, &keys, gfp);
 	if (ret < 0)
 		goto err;

 	ci = krb5_prepare_encryption(krb5, &keys, gfp);
 	if (IS_ERR(ci)) {
 		ret = PTR_ERR(ci);
 		goto err;
 	}

 	kfree(keys.data);
 	return ci;
 err:
 	kfree(keys.data);
 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(crypto_krb5_prepare_encryption);

 /*
  * Prepare the checksum with derived key data.
  */
 struct crypto_shash *krb5_prepare_checksum(const struct krb5_enctype *krb5,
 					   const struct krb5_buffer *Kc,
 					   gfp_t gfp)
 {
 	struct crypto_shash *ci = NULL;
 	int ret = -ENOMEM;

 	ci = crypto_alloc_shash(krb5->cksum_name, 0, 0);
 	if (IS_ERR(ci)) {
 		ret = PTR_ERR(ci);
 		if (ret == -ENOENT)
 			ret = -ENOPKG;
 		goto err;
 	}

 	ret = crypto_shash_setkey(ci, Kc->data, Kc->len);
 	if (ret < 0) {
 		pr_err("Couldn't set shash key %s: %d\n", krb5->cksum_name, ret);
 		goto err_ci;
 	}

 	return ci;
 err_ci:
 	crypto_free_shash(ci);
 err:
 	return ERR_PTR(ret);
 }

 /**
  * crypto_krb5_prepare_checksum - Prepare AEAD crypto object for checksum-mode
  * @krb5: The encoding to use.
  * @TK: The transport key to use.
  * @usage: The usage constant for key derivation.
  * @gfp: Allocation flags.
  *
  * Allocate a crypto object that does all the necessary crypto, key it and set
  * its parameters and return the crypto handle to it.  This can then be used to
  * dispatch get_mic and verify_mic operations.
  */
 struct crypto_shash *crypto_krb5_prepare_checksum(const struct krb5_enctype *krb5,
 						  const struct krb5_buffer *TK,
 						  u32 usage, gfp_t gfp)
 {
 	struct crypto_shash *ci = NULL;
 	struct krb5_buffer keys = {};
 	int ret;

 	ret = krb5->profile->derive_checksum_key(krb5, TK, usage, &keys, gfp);
 	if (ret < 0) {
 		pr_err("get_Kc failed %d\n", ret);
 		goto err;
 	}

 	ci = krb5_prepare_checksum(krb5, &keys, gfp);
 	if (IS_ERR(ci)) {
 		ret = PTR_ERR(ci);
 		goto err;
 	}

 	kfree(keys.data);
 	return ci;
 err:
 	kfree(keys.data);
 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL(crypto_krb5_prepare_checksum);

 /**
  * crypto_krb5_encrypt - Apply Kerberos encryption and integrity.
  * @krb5: The encoding to use.
  * @aead: The keyed crypto object to use.
  * @sg: Scatterlist defining the crypto buffer.
  * @nr_sg: The number of elements in @sg.
  * @sg_len: The size of the buffer.
  * @data_offset: The offset of the data in the @sg buffer.
  * @data_len: The length of the data.
  * @preconfounded: True if the confounder is already inserted.
  *
  * Using the specified Kerberos encoding, insert a confounder and padding as
  * needed, encrypt this and the data in place and insert an integrity checksum
  * into the buffer.
  *
  * The buffer must include space for the confounder, the checksum and any
  * padding required.  The caller can preinsert the confounder into the buffer
  * (for testing, for example).
  *
  * The resulting secured blob may be less than the size of the buffer.
  *
  * Returns the size of the secure blob if successful, -ENOMEM on an allocation
  * failure, -EFAULT if there is insufficient space, -EMSGSIZE if the confounder
  * is too short or the data is misaligned.  Other errors may also be returned
  * from the crypto layer.
  */
 ssize_t crypto_krb5_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)
 {
 	if (WARN_ON(data_offset > sg_len ||
 		    data_len > sg_len ||
 		    data_offset > sg_len - data_len))
 		return -EMSGSIZE;
 	return krb5->profile->encrypt(krb5, aead, sg, nr_sg, sg_len,
 				      data_offset, data_len, preconfounded);
 }
 EXPORT_SYMBOL(crypto_krb5_encrypt);

 /**
  * crypto_krb5_decrypt - Validate and remove Kerberos encryption and integrity.
  * @krb5: The encoding to use.
  * @aead: The keyed crypto object to use.
  * @sg: Scatterlist defining the crypto buffer.
  * @nr_sg: The number of elements in @sg.
  * @_offset: Offset of the secure blob in the buffer; updated to data offset.
  * @_len: The length of the secure blob; updated to data length.
  *
  * Using the specified Kerberos encoding, check and remove the integrity
  * checksum and decrypt the secure region, stripping off the confounder.
  *
  * If successful, @_offset and @_len are updated to outline the region in which
  * the data plus the trailing padding are stored.  The caller is responsible
  * for working out how much padding there is and removing it.
  *
  * Returns the 0 if successful, -ENOMEM on an allocation failure; sets
  * *_error_code and returns -EPROTO if the data cannot be parsed, or -EBADMSG
  * if the integrity checksum doesn't match).  Other errors may also be returned
  * from the crypto layer.
  */
 int crypto_krb5_decrypt(const struct krb5_enctype *krb5,
 			struct crypto_aead *aead,
 			struct scatterlist *sg, unsigned int nr_sg,
 			size_t *_offset, size_t *_len)
 {
 	return krb5->profile->decrypt(krb5, aead, sg, nr_sg, _offset, _len);
 }
 EXPORT_SYMBOL(crypto_krb5_decrypt);

 /**
  * crypto_krb5_get_mic - Apply Kerberos integrity checksum.
  * @krb5: The encoding to use.
  * @shash: The keyed hash to use.
  * @metadata: Metadata to add into the hash before adding the data.
  * @sg: Scatterlist defining the crypto buffer.
  * @nr_sg: The number of elements in @sg.
  * @sg_len: The size of the buffer.
  * @data_offset: The offset of the data in the @sg buffer.
  * @data_len: The length of the data.
  *
  * Using the specified Kerberos encoding, calculate and insert an integrity
  * checksum into the buffer.
  *
  * The buffer must include space for the checksum at the front.
  *
  * Returns the size of the secure blob if successful, -ENOMEM on an allocation
  * failure, -EFAULT if there is insufficient space, -EMSGSIZE if the gap for
  * the checksum is too short.  Other errors may also be returned from the
  * crypto layer.
  */
 ssize_t crypto_krb5_get_mic(const struct krb5_enctype *krb5,
 			    struct crypto_shash *shash,
 			    const struct krb5_buffer *metadata,
 			    struct scatterlist *sg, unsigned int nr_sg,
 			    size_t sg_len,
 			    size_t data_offset, size_t data_len)
 {
 	if (WARN_ON(data_offset > sg_len ||
 		    data_len > sg_len ||
 		    data_offset > sg_len - data_len))
 		return -EMSGSIZE;
 	return krb5->profile->get_mic(krb5, shash, metadata, sg, nr_sg, sg_len,
 				      data_offset, data_len);
 }
 EXPORT_SYMBOL(crypto_krb5_get_mic);

 /**
  * crypto_krb5_verify_mic - Validate and remove Kerberos integrity checksum.
  * @krb5: The encoding to use.
  * @shash: The keyed hash to use.
  * @metadata: Metadata to add into the hash before adding the data.
  * @sg: Scatterlist defining the crypto buffer.
  * @nr_sg: The number of elements in @sg.
  * @_offset: Offset of the secure blob in the buffer; updated to data offset.
  * @_len: The length of the secure blob; updated to data length.
  *
  * Using the specified Kerberos encoding, check and remove the integrity
  * checksum.
  *
  * If successful, @_offset and @_len are updated to outline the region in which
  * the data is stored.
  *
  * Returns the 0 if successful, -ENOMEM on an allocation failure; sets
  * *_error_code and returns -EPROTO if the data cannot be parsed, or -EBADMSG
  * if the checksum doesn't match).  Other errors may also be returned from the
  * crypto layer.
  */
 int crypto_krb5_verify_mic(const struct krb5_enctype *krb5,
 			   struct crypto_shash *shash,
 			   const struct krb5_buffer *metadata,
 			   struct scatterlist *sg, unsigned int nr_sg,
 			   size_t *_offset, size_t *_len)
 {
 	return krb5->profile->verify_mic(krb5, shash, metadata, sg, nr_sg,
 					 _offset, _len);
 }
 EXPORT_SYMBOL(crypto_krb5_verify_mic);

 static int __init crypto_krb5_init(void)
 {
 	return krb5_selftest();
 }
 module_init(crypto_krb5_init);

 static void __exit crypto_krb5_exit(void)
 {
 }
 module_exit(crypto_krb5_exit);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* Kerberos 5 crypto library.
	*
	* 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/module.h>
	#include <linux/export.h>
	#include <linux/kernel.h>
	#include "internal.h"

	MODULE_DESCRIPTION("Kerberos 5 crypto");
	MODULE_AUTHOR("Red Hat, Inc.");
	MODULE_LICENSE("GPL");

	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,
	&krb5_camellia128_cts_cmac,
	&krb5_camellia256_cts_cmac,
	};

	/**
	* crypto_krb5_find_enctype - Find the handler for a Kerberos5 encryption type
	* @enctype: The standard Kerberos encryption type number
	*
	* Look up a Kerberos encryption type by number. If successful, returns a
	* pointer to the type tables; returns NULL otherwise.
	*/
	const struct krb5_enctype *crypto_krb5_find_enctype(u32 enctype)
	{
	const struct krb5_enctype *krb5;
	size_t i;

	for (i = 0; i < ARRAY_SIZE(krb5_supported_enctypes); i++) {
	krb5 = krb5_supported_enctypes[i];
	if (krb5->etype == enctype)
	return krb5;
	}

	return NULL;
	}
	EXPORT_SYMBOL(crypto_krb5_find_enctype);

	/**
	* crypto_krb5_how_much_buffer - Work out how much buffer is required for an amount of data
	* @krb5: The encoding to use.
	* @mode: The mode in which to operated (checksum/encrypt)
	* @data_size: How much data we want to allow for
	* @_offset: Where to place the offset into the buffer
	*
	* Calculate how much buffer space is required to wrap a given amount of data.
	* This allows for a confounder, padding and checksum as appropriate. The
	* amount of buffer required is returned and the offset into the buffer at
	* which the data will start is placed in *_offset.
	*/
	size_t crypto_krb5_how_much_buffer(const struct krb5_enctype *krb5,
	enum krb5_crypto_mode mode,
	size_t data_size, size_t *_offset)
	{
	switch (mode) {
	case KRB5_CHECKSUM_MODE:
	*_offset = krb5->cksum_len;
	return krb5->cksum_len + data_size;

	case KRB5_ENCRYPT_MODE:
	*_offset = krb5->conf_len;
	return krb5->conf_len + data_size + krb5->cksum_len;

	default:
	WARN_ON(1);
	*_offset = 0;
	return 0;
	}
	}
	EXPORT_SYMBOL(crypto_krb5_how_much_buffer);

	/**
	* crypto_krb5_how_much_data - Work out how much data can fit in an amount of buffer
	* @krb5: The encoding to use.
	* @mode: The mode in which to operated (checksum/encrypt)
	* @_buffer_size: How much buffer we want to allow for (may be reduced)
	* @_offset: Where to place the offset into the buffer
	*
	* Calculate how much data can be fitted into given amount of buffer. This
	* allows for a confounder, padding and checksum as appropriate. The amount of
	* data that will fit is returned, the amount of buffer required is shrunk to
	* allow for alignment and the offset into the buffer at which the data will
	* start is placed in *_offset.
	*/
	size_t crypto_krb5_how_much_data(const struct krb5_enctype *krb5,
	enum krb5_crypto_mode mode,
	size_t _buffer_size, size_t _offset)
	{
	size_t buffer_size = *_buffer_size, data_size;

	switch (mode) {
	case KRB5_CHECKSUM_MODE:
	if (WARN_ON(buffer_size < krb5->cksum_len + 1))
	goto bad;
	*_offset = krb5->cksum_len;
	return buffer_size - krb5->cksum_len;

	case KRB5_ENCRYPT_MODE:
	if (WARN_ON(buffer_size < krb5->conf_len + 1 + krb5->cksum_len))
	goto bad;
	data_size = buffer_size - krb5->cksum_len;
	*_offset = krb5->conf_len;
	return data_size - krb5->conf_len;

	default:
	WARN_ON(1);
	goto bad;
	}

	bad:
	*_offset = 0;
	return 0;
	}
	EXPORT_SYMBOL(crypto_krb5_how_much_data);

	/**
	* crypto_krb5_where_is_the_data - Find the data in a decrypted message
	* @krb5: The encoding to use.
	* @mode: Mode of operation
	* @_offset: Offset of the secure blob in the buffer; updated to data offset.
	* @_len: The length of the secure blob; updated to data length.
	*
	* Find the offset and size of the data in a secure message so that this
	* information can be used in the metadata buffer which will get added to the
	* digest by crypto_krb5_verify_mic().
	*/
	void crypto_krb5_where_is_the_data(const struct krb5_enctype *krb5,
	enum krb5_crypto_mode mode,
	size_t _offset, size_t _len)
	{
	switch (mode) {
	case KRB5_CHECKSUM_MODE:
	*_offset += krb5->cksum_len;
	*_len -= krb5->cksum_len;
	return;
	case KRB5_ENCRYPT_MODE:
	*_offset += krb5->conf_len;
	*_len -= krb5->conf_len + krb5->cksum_len;
	return;
	default:
	WARN_ON_ONCE(1);
	return;
	}
	}
	EXPORT_SYMBOL(crypto_krb5_where_is_the_data);

	/*
	* Prepare the encryption with derived key data.
	*/
	struct crypto_aead krb5_prepare_encryption(const struct krb5_enctype krb5,
	const struct krb5_buffer *keys,
	gfp_t gfp)
	{
	struct crypto_aead *ci = NULL;
	int ret = -ENOMEM;

	ci = crypto_alloc_aead(krb5->encrypt_name, 0, 0);
	if (IS_ERR(ci)) {
	ret = PTR_ERR(ci);
	if (ret == -ENOENT)
	ret = -ENOPKG;
	goto err;
	}

	ret = crypto_aead_setkey(ci, keys->data, keys->len);
	if (ret < 0) {
	pr_err("Couldn't set AEAD key %s: %d\n", krb5->encrypt_name, ret);
	goto err_ci;
	}

	ret = crypto_aead_setauthsize(ci, krb5->cksum_len);
	if (ret < 0) {
	pr_err("Couldn't set AEAD authsize %s: %d\n", krb5->encrypt_name, ret);
	goto err_ci;
	}

	return ci;
	err_ci:
	crypto_free_aead(ci);
	err:
	return ERR_PTR(ret);
	}

	/**
	* crypto_krb5_prepare_encryption - Prepare AEAD crypto object for encryption-mode
	* @krb5: The encoding to use.
	* @TK: The transport key to use.
	* @usage: The usage constant for key derivation.
	* @gfp: Allocation flags.
	*
	* Allocate a crypto object that does all the necessary crypto, key it and set
	* its parameters and return the crypto handle to it. This can then be used to
	* dispatch encrypt and decrypt operations.
	*/
	struct crypto_aead crypto_krb5_prepare_encryption(const struct krb5_enctype krb5,
	const struct krb5_buffer *TK,
	u32 usage, gfp_t gfp)
	{
	struct crypto_aead *ci = NULL;
	struct krb5_buffer keys = {};
	int ret;

	ret = krb5->profile->derive_encrypt_keys(krb5, TK, usage, &keys, gfp);
	if (ret < 0)
	goto err;

	ci = krb5_prepare_encryption(krb5, &keys, gfp);
	if (IS_ERR(ci)) {
	ret = PTR_ERR(ci);
	goto err;
	}

	kfree(keys.data);
	return ci;
	err:
	kfree(keys.data);
	return ERR_PTR(ret);
	}
	EXPORT_SYMBOL(crypto_krb5_prepare_encryption);

	/*
	* Prepare the checksum with derived key data.
	*/
	struct crypto_shash krb5_prepare_checksum(const struct krb5_enctype krb5,
	const struct krb5_buffer *Kc,
	gfp_t gfp)
	{
	struct crypto_shash *ci = NULL;
	int ret = -ENOMEM;

	ci = crypto_alloc_shash(krb5->cksum_name, 0, 0);
	if (IS_ERR(ci)) {
	ret = PTR_ERR(ci);
	if (ret == -ENOENT)
	ret = -ENOPKG;
	goto err;
	}

	ret = crypto_shash_setkey(ci, Kc->data, Kc->len);
	if (ret < 0) {
	pr_err("Couldn't set shash key %s: %d\n", krb5->cksum_name, ret);
	goto err_ci;
	}

	return ci;
	err_ci:
	crypto_free_shash(ci);
	err:
	return ERR_PTR(ret);
	}

	/**
	* crypto_krb5_prepare_checksum - Prepare AEAD crypto object for checksum-mode
	* @krb5: The encoding to use.
	* @TK: The transport key to use.
	* @usage: The usage constant for key derivation.
	* @gfp: Allocation flags.
	*
	* Allocate a crypto object that does all the necessary crypto, key it and set
	* its parameters and return the crypto handle to it. This can then be used to
	* dispatch get_mic and verify_mic operations.
	*/
	struct crypto_shash crypto_krb5_prepare_checksum(const struct krb5_enctype krb5,
	const struct krb5_buffer *TK,
	u32 usage, gfp_t gfp)
	{
	struct crypto_shash *ci = NULL;
	struct krb5_buffer keys = {};
	int ret;

	ret = krb5->profile->derive_checksum_key(krb5, TK, usage, &keys, gfp);
	if (ret < 0) {
	pr_err("get_Kc failed %d\n", ret);
	goto err;
	}

	ci = krb5_prepare_checksum(krb5, &keys, gfp);
	if (IS_ERR(ci)) {
	ret = PTR_ERR(ci);
	goto err;
	}

	kfree(keys.data);
	return ci;
	err:
	kfree(keys.data);
	return ERR_PTR(ret);
	}
	EXPORT_SYMBOL(crypto_krb5_prepare_checksum);

	/**
	* crypto_krb5_encrypt - Apply Kerberos encryption and integrity.
	* @krb5: The encoding to use.
	* @aead: The keyed crypto object to use.
	* @sg: Scatterlist defining the crypto buffer.
	* @nr_sg: The number of elements in @sg.
	* @sg_len: The size of the buffer.
	* @data_offset: The offset of the data in the @sg buffer.
	* @data_len: The length of the data.
	* @preconfounded: True if the confounder is already inserted.
	*
	* Using the specified Kerberos encoding, insert a confounder and padding as
	* needed, encrypt this and the data in place and insert an integrity checksum
	* into the buffer.
	*
	* The buffer must include space for the confounder, the checksum and any
	* padding required. The caller can preinsert the confounder into the buffer
	* (for testing, for example).
	*
	* The resulting secured blob may be less than the size of the buffer.
	*
	* Returns the size of the secure blob if successful, -ENOMEM on an allocation
	* failure, -EFAULT if there is insufficient space, -EMSGSIZE if the confounder
	* is too short or the data is misaligned. Other errors may also be returned
	* from the crypto layer.
	*/
	ssize_t crypto_krb5_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)
	{
	if (WARN_ON(data_offset > sg_len \|\|
	data_len > sg_len \|\|
	data_offset > sg_len - data_len))
	return -EMSGSIZE;
	return krb5->profile->encrypt(krb5, aead, sg, nr_sg, sg_len,
	data_offset, data_len, preconfounded);
	}
	EXPORT_SYMBOL(crypto_krb5_encrypt);

	/**
	* crypto_krb5_decrypt - Validate and remove Kerberos encryption and integrity.
	* @krb5: The encoding to use.
	* @aead: The keyed crypto object to use.
	* @sg: Scatterlist defining the crypto buffer.
	* @nr_sg: The number of elements in @sg.
	* @_offset: Offset of the secure blob in the buffer; updated to data offset.
	* @_len: The length of the secure blob; updated to data length.
	*
	* Using the specified Kerberos encoding, check and remove the integrity
	* checksum and decrypt the secure region, stripping off the confounder.
	*
	* If successful, @_offset and @_len are updated to outline the region in which
	* the data plus the trailing padding are stored. The caller is responsible
	* for working out how much padding there is and removing it.
	*
	* Returns the 0 if successful, -ENOMEM on an allocation failure; sets
	* *_error_code and returns -EPROTO if the data cannot be parsed, or -EBADMSG
	* if the integrity checksum doesn't match). Other errors may also be returned
	* from the crypto layer.
	*/
	int crypto_krb5_decrypt(const struct krb5_enctype *krb5,
	struct crypto_aead *aead,
	struct scatterlist *sg, unsigned int nr_sg,
	size_t _offset, size_t _len)
	{
	return krb5->profile->decrypt(krb5, aead, sg, nr_sg, _offset, _len);
	}
	EXPORT_SYMBOL(crypto_krb5_decrypt);

	/**
	* crypto_krb5_get_mic - Apply Kerberos integrity checksum.
	* @krb5: The encoding to use.
	* @shash: The keyed hash to use.
	* @metadata: Metadata to add into the hash before adding the data.
	* @sg: Scatterlist defining the crypto buffer.
	* @nr_sg: The number of elements in @sg.
	* @sg_len: The size of the buffer.
	* @data_offset: The offset of the data in the @sg buffer.
	* @data_len: The length of the data.
	*
	* Using the specified Kerberos encoding, calculate and insert an integrity
	* checksum into the buffer.
	*
	* The buffer must include space for the checksum at the front.
	*
	* Returns the size of the secure blob if successful, -ENOMEM on an allocation
	* failure, -EFAULT if there is insufficient space, -EMSGSIZE if the gap for
	* the checksum is too short. Other errors may also be returned from the
	* crypto layer.
	*/
	ssize_t crypto_krb5_get_mic(const struct krb5_enctype *krb5,
	struct crypto_shash *shash,
	const struct krb5_buffer *metadata,
	struct scatterlist *sg, unsigned int nr_sg,
	size_t sg_len,
	size_t data_offset, size_t data_len)
	{
	if (WARN_ON(data_offset > sg_len \|\|
	data_len > sg_len \|\|
	data_offset > sg_len - data_len))
	return -EMSGSIZE;
	return krb5->profile->get_mic(krb5, shash, metadata, sg, nr_sg, sg_len,
	data_offset, data_len);
	}
	EXPORT_SYMBOL(crypto_krb5_get_mic);

	/**
	* crypto_krb5_verify_mic - Validate and remove Kerberos integrity checksum.
	* @krb5: The encoding to use.
	* @shash: The keyed hash to use.
	* @metadata: Metadata to add into the hash before adding the data.
	* @sg: Scatterlist defining the crypto buffer.
	* @nr_sg: The number of elements in @sg.
	* @_offset: Offset of the secure blob in the buffer; updated to data offset.
	* @_len: The length of the secure blob; updated to data length.
	*
	* Using the specified Kerberos encoding, check and remove the integrity
	* checksum.
	*
	* If successful, @_offset and @_len are updated to outline the region in which
	* the data is stored.
	*
	* Returns the 0 if successful, -ENOMEM on an allocation failure; sets
	* *_error_code and returns -EPROTO if the data cannot be parsed, or -EBADMSG
	* if the checksum doesn't match). Other errors may also be returned from the
	* crypto layer.
	*/
	int crypto_krb5_verify_mic(const struct krb5_enctype *krb5,
	struct crypto_shash *shash,
	const struct krb5_buffer *metadata,
	struct scatterlist *sg, unsigned int nr_sg,
	size_t _offset, size_t _len)
	{
	return krb5->profile->verify_mic(krb5, shash, metadata, sg, nr_sg,
	_offset, _len);
	}
	EXPORT_SYMBOL(crypto_krb5_verify_mic);

	static int __init crypto_krb5_init(void)
	{
	return krb5_selftest();
	}
	module_init(crypto_krb5_init);

	static void __exit crypto_krb5_exit(void)
	{
	}
	module_exit(crypto_krb5_exit);