crypto/kmac/kmac.c - third_party/openssl - Git at Google

 /*
  * Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the Apache License 2.0 (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
  * in the file LICENSE in the source distribution or at
  * https://www.openssl.org/source/license.html
  */

 /*
  * See SP800-185 "Appendix A - KMAC, .... in Terms of Keccak[c]"
  *
  * Inputs are:
  *    K = Key                  (len(K) < 2^2040 bits)
  *    X = Input
  *    L = Output length        (0 <= L < 2^2040 bits)
  *    S = Customization String Default="" (len(S) < 2^2040 bits)
  *
  * KMAC128(K, X, L, S)
  * {
  *     newX = bytepad(encode_string(K), 168) ||  X || right_encode(L).
  *     T = bytepad(encode_string("KMAC") || encode_string(S), 168).
  *     return KECCAK[256](T || newX || 00, L).
  * }
  *
  * KMAC256(K, X, L, S)
  * {
  *     newX = bytepad(encode_string(K), 136) ||  X || right_encode(L).
  *     T = bytepad(encode_string("KMAC") || encode_string(S), 136).
  *     return KECCAK[512](T || newX || 00, L).
  * }
  *
  * KMAC128XOF(K, X, L, S)
  * {
  *     newX = bytepad(encode_string(K), 168) ||  X || right_encode(0).
  *     T = bytepad(encode_string("KMAC") || encode_string(S), 168).
  *     return KECCAK[256](T || newX || 00, L).
  * }
  *
  * KMAC256XOF(K, X, L, S)
  * {
  *     newX = bytepad(encode_string(K), 136) ||  X || right_encode(0).
  *     T = bytepad(encode_string("KMAC") || encode_string(S), 136).
  *     return KECCAK[512](T || newX || 00, L).
  * }
  *
  */

 #include <stdlib.h>
 #include <openssl/evp.h>
 #include "internal/cryptlib.h"
 #include "internal/evp_int.h"

 #define KMAC_MAX_BLOCKSIZE ((1600 - 128*2) / 8) /* 168 */
 #define KMAC_MIN_BLOCKSIZE ((1600 - 256*2) / 8) /* 136 */

 /* Length encoding will be  a 1 byte size + length in bits (2 bytes max) */
 #define KMAC_MAX_ENCODED_HEADER_LEN 3

 /*
  * Custom string max size is chosen such that:
  *   len(encoded_string(custom) + len(kmac_encoded_string) <= KMAC_MIN_BLOCKSIZE
  *   i.e: (KMAC_MAX_CUSTOM + KMAC_MAX_ENCODED_LEN) + 6 <= 136
  */
 #define KMAC_MAX_CUSTOM 127

 /* Maximum size of encoded custom string */
 #define KMAC_MAX_CUSTOM_ENCODED (KMAC_MAX_CUSTOM + KMAC_MAX_ENCODED_HEADER_LEN)

 /* Maximum key size in bytes = 2040 / 8 */
 #define KMAC_MAX_KEY 255

 /*
  * Maximum Encoded Key size will be padded to a multiple of the blocksize
  * i.e KMAC_MAX_KEY + KMAC_MAX_ENCODED_LEN = 258
  * Padded to a multiple of KMAC_MAX_BLOCKSIZE
  */
 #define KMAC_MAX_KEY_ENCODED (KMAC_MAX_BLOCKSIZE * 2)

 /* Fixed value of encode_string("KMAC") */
 static const unsigned char kmac_string[] = {
     0x01, 0x20, 0x4B, 0x4D, 0x41, 0x43
 };


 #define KMAC_FLAG_XOF_MODE          1

 /* typedef EVP_MAC_IMPL */
 struct evp_mac_impl_st {
     EVP_MD_CTX *ctx;
     const EVP_MD *md;
     size_t out_len;
     int key_len;
     int custom_len;
     /* If xof_mode = 1 then we use right_encode(0) */
     int xof_mode;
     /* key and custom are stored in encoded form */
     unsigned char key[KMAC_MAX_KEY_ENCODED];
     unsigned char custom[KMAC_MAX_CUSTOM_ENCODED];
 };

 static int encode_string(unsigned char *out, int *out_len,
                          const unsigned char *in, int in_len);
 static int right_encode(unsigned char *out, int *out_len, size_t bits);
 static int bytepad(unsigned char *out, int *out_len,
                    const unsigned char *in1, int in1_len,
                    const unsigned char *in2, int in2_len,
                    int w);
 static int kmac_bytepad_encode_key(unsigned char *out, int *out_len,
                                    const unsigned char *in, int in_len,
                                    int w);
 static int kmac_ctrl_str(EVP_MAC_IMPL *kctx, const char *type,
                          const char *value);


 static void kmac_free(EVP_MAC_IMPL *kctx)
 {
     if (kctx != NULL) {
         EVP_MD_CTX_free(kctx->ctx);
         OPENSSL_cleanse(kctx->key, kctx->key_len);
         OPENSSL_cleanse(kctx->custom, kctx->custom_len);
         OPENSSL_free(kctx);
     }
 }

 static EVP_MAC_IMPL *kmac_new(const EVP_MD *md)
 {
     EVP_MAC_IMPL *kctx = NULL;

     if ((kctx = OPENSSL_zalloc(sizeof(*kctx))) == NULL
             || (kctx->ctx = EVP_MD_CTX_new()) == NULL) {
         kmac_free(kctx);
         return NULL;
     }
     kctx->md = md;
     kctx->out_len = md->md_size;
     return kctx;
 }

 static EVP_MAC_IMPL *kmac128_new(void)
 {
     return kmac_new(evp_keccak_kmac128());
 }

 static EVP_MAC_IMPL *kmac256_new(void)
 {
     return kmac_new(evp_keccak_kmac256());
 }

 static int kmac_copy(EVP_MAC_IMPL *gdst, EVP_MAC_IMPL *gsrc)
 {
     gdst->md = gsrc->md;
     gdst->out_len = gsrc->out_len;
     gdst->key_len = gsrc->key_len;
     gdst->custom_len = gsrc->custom_len;
     gdst->xof_mode = gsrc->xof_mode;
     memcpy(gdst->key, gsrc->key, gsrc->key_len);
     memcpy(gdst->custom, gsrc->custom, gdst->custom_len);

     return EVP_MD_CTX_copy(gdst->ctx, gsrc->ctx);
 }

 /*
  * The init() assumes that any ctrl methods are set beforehand for
  * md, key and custom. Setting the fields afterwards will have no
  * effect on the output mac.
  */
 static int kmac_init(EVP_MAC_IMPL *kctx)
 {
     EVP_MD_CTX *ctx = kctx->ctx;
     unsigned char out[KMAC_MAX_BLOCKSIZE];
     int out_len, block_len;

     /* Check key has been set */
     if (kctx->key_len == 0) {
         EVPerr(EVP_F_KMAC_INIT, EVP_R_NO_KEY_SET);
         return 0;
     }
     if (!EVP_DigestInit_ex(kctx->ctx, kctx->md, NULL))
         return 0;

     block_len = EVP_MD_block_size(kctx->md);

     /* Set default custom string if it is not already set */
     if (kctx->custom_len == 0)
         (void)kmac_ctrl_str(kctx, "custom", "");

     return bytepad(out, &out_len, kmac_string, sizeof(kmac_string),
                    kctx->custom, kctx->custom_len, block_len)
            && EVP_DigestUpdate(ctx, out, out_len)
            && EVP_DigestUpdate(ctx, kctx->key, kctx->key_len);
 }

 static size_t kmac_size(EVP_MAC_IMPL *kctx)
 {
     return kctx->out_len;
 }

 static int kmac_update(EVP_MAC_IMPL *kctx, const unsigned char *data,
                        size_t datalen)
 {
     return EVP_DigestUpdate(kctx->ctx, data, datalen);
 }

 static int kmac_final(EVP_MAC_IMPL *kctx, unsigned char *out)
 {
     EVP_MD_CTX *ctx = kctx->ctx;
     int lbits, len;
     unsigned char encoded_outlen[KMAC_MAX_ENCODED_HEADER_LEN];

     /* KMAC XOF mode sets the encoded length to 0 */
     lbits = (kctx->xof_mode ? 0 : (kctx->out_len * 8));

     return right_encode(encoded_outlen, &len, lbits)
            && EVP_DigestUpdate(ctx, encoded_outlen, len)
            && EVP_DigestFinalXOF(ctx, out, kctx->out_len);
 }

 /*
  * The following Ctrl functions can be set any time before final():
  *     - EVP_MAC_CTRL_SET_SIZE: The requested output length.
  *     - EVP_MAC_CTRL_SET_XOF: If set, this indicates that right_encoded(0) is
  *                             part of the digested data, otherwise it uses
  *                             right_encoded(requested output length).

  * All other Ctrl functions should be set before init().
  */
 static int kmac_ctrl(EVP_MAC_IMPL *kctx, int cmd, va_list args)
 {
     const unsigned char *p;
     size_t len;
     size_t size;

     switch (cmd) {
     case EVP_MAC_CTRL_SET_XOF:
         kctx->xof_mode = va_arg(args, int);
         return 1;

     case EVP_MAC_CTRL_SET_SIZE:
         size = va_arg(args, size_t);
         kctx->out_len = size;
         return 1;

     case EVP_MAC_CTRL_SET_KEY:
         p = va_arg(args, const unsigned char *);
         len = va_arg(args, size_t);
         if (len < 4 || len > KMAC_MAX_KEY) {
             EVPerr(EVP_F_KMAC_CTRL, EVP_R_INVALID_KEY_LENGTH);
             return 0;
         }
         return kmac_bytepad_encode_key(kctx->key, &kctx->key_len, p, len,
                                        EVP_MD_block_size(kctx->md));

     case EVP_MAC_CTRL_SET_CUSTOM:
         p = va_arg(args, const unsigned char *);
         len = va_arg(args, size_t);
         if (len > KMAC_MAX_CUSTOM) {
             EVPerr(EVP_F_KMAC_CTRL, EVP_R_INVALID_CUSTOM_LENGTH);
             return 0;
         }
         return encode_string(kctx->custom, &kctx->custom_len, p, len);

     default:
         return -2;
     }
 }

 static int kmac_ctrl_int(EVP_MAC_IMPL *kctx, int cmd, ...)
 {
     int rv;
     va_list args;

     va_start(args, cmd);
     rv = kmac_ctrl(kctx, cmd, args);
     va_end(args);

     return rv;
 }

 static int kmac_ctrl_str_cb(void *kctx, int cmd, void *buf, size_t buflen)
 {
     return kmac_ctrl_int(kctx, cmd, buf, buflen);
 }

 static int kmac_ctrl_str(EVP_MAC_IMPL *kctx, const char *type,
                          const char *value)
 {
     if (value == NULL)
         return 0;

     if (strcmp(type, "outlen") == 0)
         return kmac_ctrl_int(kctx, EVP_MAC_CTRL_SET_SIZE, (size_t)atoi(value));
     if (strcmp(type, "xof") == 0)
         return kmac_ctrl_int(kctx, EVP_MAC_CTRL_SET_XOF, atoi(value));
     if (strcmp(type, "key") == 0)
         return EVP_str2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_KEY,
                             value);
     if (strcmp(type, "hexkey") == 0)
         return EVP_hex2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_KEY,
                             value);
     if (strcmp(type, "custom") == 0)
         return EVP_str2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_CUSTOM,
                             value);
     if (strcmp(type, "hexcustom") == 0)
         return EVP_hex2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_CUSTOM,
                             value);
     return -2;
 }

 /*
  * Encoding/Padding Methods.
  */

 /* Returns the number of bytes required to store 'bits' into a byte array */
 static unsigned int get_encode_size(size_t bits)
 {
     unsigned int cnt = 0, sz = sizeof(size_t);

     while (bits && (cnt < sz)) {
         ++cnt;
         bits >>= 8;
     }
     /* If bits is zero 1 byte is required */
     if (cnt == 0)
         cnt = 1;
     return cnt;
 }

 /*
  * Convert an integer into bytes . The number of bytes is appended
  * to the end of the buffer. Returns an array of bytes 'out' of size
  * *out_len.
  *
  * e.g if bits = 32, out[2] = { 0x20, 0x01 }
  *
  */
 static int right_encode(unsigned char *out, int *out_len, size_t bits)
 {
     unsigned int len = get_encode_size(bits);
     int i;

     /* The length is constrained to a single byte: 2040/8 = 255 */
     if (len > 0xFF)
         return 0;

     /* MSB's are at the start of the bytes array */
     for (i = len - 1; i >= 0; --i) {
         out[i] = (unsigned char)(bits & 0xFF);
         bits >>= 8;
     }
     /* Tack the length onto the end */
     out[len] = (unsigned char)len;

     /* The Returned length includes the tacked on byte */
     *out_len = len + 1;
     return 1;
 }

 /*
  * Encodes a string with a left encoded length added. Note that the
  * in_len is converted to bits (*8).
  *
  * e.g- in="KMAC" gives out[6] = { 0x01, 0x20, 0x4B, 0x4D, 0x41, 0x43 }
  *                                 len   bits    K     M     A     C
  */
 static int encode_string(unsigned char *out, int *out_len,
                          const unsigned char *in, int in_len)
 {
     if (in == NULL) {
         *out_len = 0;
     } else {
         int i, bits, len;

         bits = 8 * in_len;
         len = get_encode_size(bits);
         if (len > 0xFF)
             return 0;

         out[0] = len;
         for (i = len; i > 0; --i) {
             out[i] = (bits & 0xFF);
             bits >>= 8;
         }
         memcpy(out + len + 1, in, in_len);
         *out_len = (1 + len + in_len);
     }
     return 1;
 }

 /*
  * Returns a zero padded encoding of the inputs in1 and an optional
  * in2 (can be NULL). The padded output must be a multiple of the blocksize 'w'.
  * The value of w is in bytes (< 256).
  *
  * The returned output is:
  *    zero_padded(multiple of w, (left_encode(w) || in1 [|| in2])
  */
 static int bytepad(unsigned char *out, int *out_len,
                    const unsigned char *in1, int in1_len,
                    const unsigned char *in2, int in2_len, int w)
 {
     int len;
     unsigned char *p = out;
     int sz = w;

     /* Left encoded w */
     *p++ = 1;
     *p++ = w;
     /* || in1 */
     memcpy(p, in1, in1_len);
     p += in1_len;
     /* [ || in2 ] */
     if (in2 != NULL && in2_len > 0) {
         memcpy(p, in2, in2_len);
         p += in2_len;
     }
     /* Figure out the pad size (divisible by w) */
     len = p - out;
     while (len > sz) {
         sz += w;
     }
     /* zero pad the end of the buffer */
     memset(p, 0, sz - len);
     *out_len = sz;
     return 1;
 }

 /*
  * Returns out = bytepad(encode_string(in), w)
  */
 static int kmac_bytepad_encode_key(unsigned char *out, int *out_len,
                                    const unsigned char *in, int in_len,
                                    int w)
 {
     unsigned char tmp[KMAC_MAX_KEY + KMAC_MAX_ENCODED_HEADER_LEN];
     int tmp_len;

     if (!encode_string(tmp, &tmp_len, in, in_len))
         return 0;

     return bytepad(out, out_len, tmp, tmp_len, NULL, 0, w);
 }

 const EVP_MAC kmac128_meth = {
     EVP_MAC_KMAC128,
     kmac128_new,
     kmac_copy,
     kmac_free,
     kmac_size,
     kmac_init,
     kmac_update,
     kmac_final,
     kmac_ctrl,
     kmac_ctrl_str
 };

 const EVP_MAC kmac256_meth = {
     EVP_MAC_KMAC256,
     kmac256_new,
     kmac_copy,
     kmac_free,
     kmac_size,
     kmac_init,
     kmac_update,
     kmac_final,
     kmac_ctrl,
     kmac_ctrl_str
 };
	/*
	* Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
	*
	* Licensed under the Apache License 2.0 (the "License"). You may not use
	* this file except in compliance with the License. You can obtain a copy
	* in the file LICENSE in the source distribution or at
	* https://www.openssl.org/source/license.html
	*/

	/*
	* See SP800-185 "Appendix A - KMAC, .... in Terms of Keccak[c]"
	*
	* Inputs are:
	* K = Key (len(K) < 2^2040 bits)
	* X = Input
	* L = Output length (0 <= L < 2^2040 bits)
	* S = Customization String Default="" (len(S) < 2^2040 bits)
	*
	* KMAC128(K, X, L, S)
	* {
	* newX = bytepad(encode_string(K), 168) \|\| X \|\| right_encode(L).
	* T = bytepad(encode_string("KMAC") \|\| encode_string(S), 168).
	* return KECCAK[256](T \|\| newX \|\| 00, L).
	* }
	*
	* KMAC256(K, X, L, S)
	* {
	* newX = bytepad(encode_string(K), 136) \|\| X \|\| right_encode(L).
	* T = bytepad(encode_string("KMAC") \|\| encode_string(S), 136).
	* return KECCAK[512](T \|\| newX \|\| 00, L).
	* }
	*
	* KMAC128XOF(K, X, L, S)
	* {
	* newX = bytepad(encode_string(K), 168) \|\| X \|\| right_encode(0).
	* T = bytepad(encode_string("KMAC") \|\| encode_string(S), 168).
	* return KECCAK[256](T \|\| newX \|\| 00, L).
	* }
	*
	* KMAC256XOF(K, X, L, S)
	* {
	* newX = bytepad(encode_string(K), 136) \|\| X \|\| right_encode(0).
	* T = bytepad(encode_string("KMAC") \|\| encode_string(S), 136).
	* return KECCAK[512](T \|\| newX \|\| 00, L).
	* }
	*
	*/

	#include <stdlib.h>
	#include <openssl/evp.h>
	#include "internal/cryptlib.h"
	#include "internal/evp_int.h"

	#define KMAC_MAX_BLOCKSIZE ((1600 - 1282) / 8) / 168 */
	#define KMAC_MIN_BLOCKSIZE ((1600 - 2562) / 8) / 136 */

	/* Length encoding will be a 1 byte size + length in bits (2 bytes max) */
	#define KMAC_MAX_ENCODED_HEADER_LEN 3

	/*
	* Custom string max size is chosen such that:
	* len(encoded_string(custom) + len(kmac_encoded_string) <= KMAC_MIN_BLOCKSIZE
	* i.e: (KMAC_MAX_CUSTOM + KMAC_MAX_ENCODED_LEN) + 6 <= 136
	*/
	#define KMAC_MAX_CUSTOM 127

	/* Maximum size of encoded custom string */
	#define KMAC_MAX_CUSTOM_ENCODED (KMAC_MAX_CUSTOM + KMAC_MAX_ENCODED_HEADER_LEN)

	/* Maximum key size in bytes = 2040 / 8 */
	#define KMAC_MAX_KEY 255

	/*
	* Maximum Encoded Key size will be padded to a multiple of the blocksize
	* i.e KMAC_MAX_KEY + KMAC_MAX_ENCODED_LEN = 258
	* Padded to a multiple of KMAC_MAX_BLOCKSIZE
	*/
	#define KMAC_MAX_KEY_ENCODED (KMAC_MAX_BLOCKSIZE * 2)

	/* Fixed value of encode_string("KMAC") */
	static const unsigned char kmac_string[] = {
	0x01, 0x20, 0x4B, 0x4D, 0x41, 0x43
	};


	#define KMAC_FLAG_XOF_MODE 1

	/* typedef EVP_MAC_IMPL */
	struct evp_mac_impl_st {
	EVP_MD_CTX *ctx;
	const EVP_MD *md;
	size_t out_len;
	int key_len;
	int custom_len;
	/* If xof_mode = 1 then we use right_encode(0) */
	int xof_mode;
	/* key and custom are stored in encoded form */
	unsigned char key[KMAC_MAX_KEY_ENCODED];
	unsigned char custom[KMAC_MAX_CUSTOM_ENCODED];
	};

	static int encode_string(unsigned char out, int out_len,
	const unsigned char *in, int in_len);
	static int right_encode(unsigned char out, int out_len, size_t bits);
	static int bytepad(unsigned char out, int out_len,
	const unsigned char *in1, int in1_len,
	const unsigned char *in2, int in2_len,
	int w);
	static int kmac_bytepad_encode_key(unsigned char out, int out_len,
	const unsigned char *in, int in_len,
	int w);
	static int kmac_ctrl_str(EVP_MAC_IMPL kctx, const char type,
	const char *value);


	static void kmac_free(EVP_MAC_IMPL *kctx)
	{
	if (kctx != NULL) {
	EVP_MD_CTX_free(kctx->ctx);
	OPENSSL_cleanse(kctx->key, kctx->key_len);
	OPENSSL_cleanse(kctx->custom, kctx->custom_len);
	OPENSSL_free(kctx);
	}
	}

	static EVP_MAC_IMPL kmac_new(const EVP_MD md)
	{
	EVP_MAC_IMPL *kctx = NULL;

	if ((kctx = OPENSSL_zalloc(sizeof(*kctx))) == NULL
	\|\| (kctx->ctx = EVP_MD_CTX_new()) == NULL) {
	kmac_free(kctx);
	return NULL;
	}
	kctx->md = md;
	kctx->out_len = md->md_size;
	return kctx;
	}

	static EVP_MAC_IMPL *kmac128_new(void)
	{
	return kmac_new(evp_keccak_kmac128());
	}

	static EVP_MAC_IMPL *kmac256_new(void)
	{
	return kmac_new(evp_keccak_kmac256());
	}

	static int kmac_copy(EVP_MAC_IMPL gdst, EVP_MAC_IMPL gsrc)
	{
	gdst->md = gsrc->md;
	gdst->out_len = gsrc->out_len;
	gdst->key_len = gsrc->key_len;
	gdst->custom_len = gsrc->custom_len;
	gdst->xof_mode = gsrc->xof_mode;
	memcpy(gdst->key, gsrc->key, gsrc->key_len);
	memcpy(gdst->custom, gsrc->custom, gdst->custom_len);

	return EVP_MD_CTX_copy(gdst->ctx, gsrc->ctx);
	}

	/*
	* The init() assumes that any ctrl methods are set beforehand for
	* md, key and custom. Setting the fields afterwards will have no
	* effect on the output mac.
	*/
	static int kmac_init(EVP_MAC_IMPL *kctx)
	{
	EVP_MD_CTX *ctx = kctx->ctx;
	unsigned char out[KMAC_MAX_BLOCKSIZE];
	int out_len, block_len;

	/* Check key has been set */
	if (kctx->key_len == 0) {
	EVPerr(EVP_F_KMAC_INIT, EVP_R_NO_KEY_SET);
	return 0;
	}
	if (!EVP_DigestInit_ex(kctx->ctx, kctx->md, NULL))
	return 0;

	block_len = EVP_MD_block_size(kctx->md);

	/* Set default custom string if it is not already set */
	if (kctx->custom_len == 0)
	(void)kmac_ctrl_str(kctx, "custom", "");

	return bytepad(out, &out_len, kmac_string, sizeof(kmac_string),
	kctx->custom, kctx->custom_len, block_len)
	&& EVP_DigestUpdate(ctx, out, out_len)
	&& EVP_DigestUpdate(ctx, kctx->key, kctx->key_len);
	}

	static size_t kmac_size(EVP_MAC_IMPL *kctx)
	{
	return kctx->out_len;
	}

	static int kmac_update(EVP_MAC_IMPL kctx, const unsigned char data,
	size_t datalen)
	{
	return EVP_DigestUpdate(kctx->ctx, data, datalen);
	}

	static int kmac_final(EVP_MAC_IMPL kctx, unsigned char out)
	{
	EVP_MD_CTX *ctx = kctx->ctx;
	int lbits, len;
	unsigned char encoded_outlen[KMAC_MAX_ENCODED_HEADER_LEN];

	/* KMAC XOF mode sets the encoded length to 0 */
	lbits = (kctx->xof_mode ? 0 : (kctx->out_len * 8));

	return right_encode(encoded_outlen, &len, lbits)
	&& EVP_DigestUpdate(ctx, encoded_outlen, len)
	&& EVP_DigestFinalXOF(ctx, out, kctx->out_len);
	}

	/*
	* The following Ctrl functions can be set any time before final():
	* - EVP_MAC_CTRL_SET_SIZE: The requested output length.
	* - EVP_MAC_CTRL_SET_XOF: If set, this indicates that right_encoded(0) is
	* part of the digested data, otherwise it uses
	* right_encoded(requested output length).

	* All other Ctrl functions should be set before init().
	*/
	static int kmac_ctrl(EVP_MAC_IMPL *kctx, int cmd, va_list args)
	{
	const unsigned char *p;
	size_t len;
	size_t size;

	switch (cmd) {
	case EVP_MAC_CTRL_SET_XOF:
	kctx->xof_mode = va_arg(args, int);
	return 1;

	case EVP_MAC_CTRL_SET_SIZE:
	size = va_arg(args, size_t);
	kctx->out_len = size;
	return 1;

	case EVP_MAC_CTRL_SET_KEY:
	p = va_arg(args, const unsigned char *);
	len = va_arg(args, size_t);
	if (len < 4 \|\| len > KMAC_MAX_KEY) {
	EVPerr(EVP_F_KMAC_CTRL, EVP_R_INVALID_KEY_LENGTH);
	return 0;
	}
	return kmac_bytepad_encode_key(kctx->key, &kctx->key_len, p, len,
	EVP_MD_block_size(kctx->md));

	case EVP_MAC_CTRL_SET_CUSTOM:
	p = va_arg(args, const unsigned char *);
	len = va_arg(args, size_t);
	if (len > KMAC_MAX_CUSTOM) {
	EVPerr(EVP_F_KMAC_CTRL, EVP_R_INVALID_CUSTOM_LENGTH);
	return 0;
	}
	return encode_string(kctx->custom, &kctx->custom_len, p, len);

	default:
	return -2;
	}
	}

	static int kmac_ctrl_int(EVP_MAC_IMPL *kctx, int cmd, ...)
	{
	int rv;
	va_list args;

	va_start(args, cmd);
	rv = kmac_ctrl(kctx, cmd, args);
	va_end(args);

	return rv;
	}

	static int kmac_ctrl_str_cb(void kctx, int cmd, void buf, size_t buflen)
	{
	return kmac_ctrl_int(kctx, cmd, buf, buflen);
	}

	static int kmac_ctrl_str(EVP_MAC_IMPL kctx, const char type,
	const char *value)
	{
	if (value == NULL)
	return 0;

	if (strcmp(type, "outlen") == 0)
	return kmac_ctrl_int(kctx, EVP_MAC_CTRL_SET_SIZE, (size_t)atoi(value));
	if (strcmp(type, "xof") == 0)
	return kmac_ctrl_int(kctx, EVP_MAC_CTRL_SET_XOF, atoi(value));
	if (strcmp(type, "key") == 0)
	return EVP_str2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_KEY,
	value);
	if (strcmp(type, "hexkey") == 0)
	return EVP_hex2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_KEY,
	value);
	if (strcmp(type, "custom") == 0)
	return EVP_str2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_CUSTOM,
	value);
	if (strcmp(type, "hexcustom") == 0)
	return EVP_hex2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_CUSTOM,
	value);
	return -2;
	}

	/*
	* Encoding/Padding Methods.
	*/

	/* Returns the number of bytes required to store 'bits' into a byte array */
	static unsigned int get_encode_size(size_t bits)
	{
	unsigned int cnt = 0, sz = sizeof(size_t);

	while (bits && (cnt < sz)) {
	++cnt;
	bits >>= 8;
	}
	/* If bits is zero 1 byte is required */
	if (cnt == 0)
	cnt = 1;
	return cnt;
	}

	/*
	* Convert an integer into bytes . The number of bytes is appended
	* to the end of the buffer. Returns an array of bytes 'out' of size
	* *out_len.
	*
	* e.g if bits = 32, out[2] = { 0x20, 0x01 }
	*
	*/
	static int right_encode(unsigned char out, int out_len, size_t bits)
	{
	unsigned int len = get_encode_size(bits);
	int i;

	/* The length is constrained to a single byte: 2040/8 = 255 */
	if (len > 0xFF)
	return 0;

	/* MSB's are at the start of the bytes array */
	for (i = len - 1; i >= 0; --i) {
	out[i] = (unsigned char)(bits & 0xFF);
	bits >>= 8;
	}
	/* Tack the length onto the end */
	out[len] = (unsigned char)len;

	/* The Returned length includes the tacked on byte */
	*out_len = len + 1;
	return 1;
	}

	/*
	* Encodes a string with a left encoded length added. Note that the
	* in_len is converted to bits (*8).
	*
	* e.g- in="KMAC" gives out[6] = { 0x01, 0x20, 0x4B, 0x4D, 0x41, 0x43 }
	* len bits K M A C
	*/
	static int encode_string(unsigned char out, int out_len,
	const unsigned char *in, int in_len)
	{
	if (in == NULL) {
	*out_len = 0;
	} else {
	int i, bits, len;

	bits = 8 * in_len;
	len = get_encode_size(bits);
	if (len > 0xFF)
	return 0;

	out[0] = len;
	for (i = len; i > 0; --i) {
	out[i] = (bits & 0xFF);
	bits >>= 8;
	}
	memcpy(out + len + 1, in, in_len);
	*out_len = (1 + len + in_len);
	}
	return 1;
	}

	/*
	* Returns a zero padded encoding of the inputs in1 and an optional
	* in2 (can be NULL). The padded output must be a multiple of the blocksize 'w'.
	* The value of w is in bytes (< 256).
	*
	* The returned output is:
	* zero_padded(multiple of w, (left_encode(w) \|\| in1 [\|\| in2])
	*/
	static int bytepad(unsigned char out, int out_len,
	const unsigned char *in1, int in1_len,
	const unsigned char *in2, int in2_len, int w)
	{
	int len;
	unsigned char *p = out;
	int sz = w;

	/* Left encoded w */
	*p++ = 1;
	*p++ = w;
	/* \|\| in1 */
	memcpy(p, in1, in1_len);
	p += in1_len;
	/* [ \|\| in2 ] */
	if (in2 != NULL && in2_len > 0) {
	memcpy(p, in2, in2_len);
	p += in2_len;
	}
	/* Figure out the pad size (divisible by w) */
	len = p - out;
	while (len > sz) {
	sz += w;
	}
	/* zero pad the end of the buffer */
	memset(p, 0, sz - len);
	*out_len = sz;
	return 1;
	}

	/*
	* Returns out = bytepad(encode_string(in), w)
	*/
	static int kmac_bytepad_encode_key(unsigned char out, int out_len,
	const unsigned char *in, int in_len,
	int w)
	{
	unsigned char tmp[KMAC_MAX_KEY + KMAC_MAX_ENCODED_HEADER_LEN];
	int tmp_len;

	if (!encode_string(tmp, &tmp_len, in, in_len))
	return 0;

	return bytepad(out, out_len, tmp, tmp_len, NULL, 0, w);
	}

	const EVP_MAC kmac128_meth = {
	EVP_MAC_KMAC128,
	kmac128_new,
	kmac_copy,
	kmac_free,
	kmac_size,
	kmac_init,
	kmac_update,
	kmac_final,
	kmac_ctrl,
	kmac_ctrl_str
	};

	const EVP_MAC kmac256_meth = {
	EVP_MAC_KMAC256,
	kmac256_new,
	kmac_copy,
	kmac_free,
	kmac_size,
	kmac_init,
	kmac_update,
	kmac_final,
	kmac_ctrl,
	kmac_ctrl_str
	};