library/chachapoly.c - security/mbedtls - Rivoreo Source Code Repositories

 /**
  * \file chachapoly.c
  *
  * \brief ChaCha20-Poly1305 AEAD construction based on RFC 7539.
  *
  *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
  *  not use this file except in compliance with the License.
  *  You may obtain a copy of the License at
  *
  *  http://www.apache.org/licenses/LICENSE-2.0
  *
  *  Unless required by applicable law or agreed to in writing, software
  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
  *
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */
 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif

 #if defined(MBEDTLS_CHACHAPOLY_C)

 #include "mbedtls/chachapoly.h"
 #include "mbedtls/platform_util.h"

 #include <string.h>

 #if defined(MBEDTLS_SELF_TEST)
 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
 #else
 #include <stdio.h>
 #define mbedtls_printf printf
 #endif /* MBEDTLS_PLATFORM_C */
 #endif /* MBEDTLS_SELF_TEST */

 #if !defined(MBEDTLS_CHACHAPOLY_ALT)

 /* Parameter validation macros */
 #define CHACHAPOLY_VALIDATE_RET( cond )                                       \
     MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA )
 #define CHACHAPOLY_VALIDATE( cond )                                           \
     MBEDTLS_INTERNAL_VALIDATE( cond )

 #define CHACHAPOLY_STATE_INIT       ( 0 )
 #define CHACHAPOLY_STATE_AAD        ( 1 )
 #define CHACHAPOLY_STATE_CIPHERTEXT ( 2 ) /* Encrypting or decrypting */
 #define CHACHAPOLY_STATE_FINISHED   ( 3 )

 /**
  * \brief           Adds nul bytes to pad the AAD for Poly1305.
  *
  * \param ctx       The ChaCha20-Poly1305 context.
  */
 static int chachapoly_pad_aad( mbedtls_chachapoly_context *ctx )
 {
     uint32_t partial_block_len = (uint32_t) ( ctx->aad_len % 16U );
     unsigned char zeroes[15];

     if( partial_block_len == 0U )
         return( 0 );

     memset( zeroes, 0, sizeof( zeroes ) );

     return( mbedtls_poly1305_update( &ctx->poly1305_ctx,
                                      zeroes,
                                      16U - partial_block_len ) );
 }

 /**
  * \brief           Adds nul bytes to pad the ciphertext for Poly1305.
  *
  * \param ctx       The ChaCha20-Poly1305 context.
  */
 static int chachapoly_pad_ciphertext( mbedtls_chachapoly_context *ctx )
 {
     uint32_t partial_block_len = (uint32_t) ( ctx->ciphertext_len % 16U );
     unsigned char zeroes[15];

     if( partial_block_len == 0U )
         return( 0 );

     memset( zeroes, 0, sizeof( zeroes ) );
     return( mbedtls_poly1305_update( &ctx->poly1305_ctx,
                                      zeroes,
                                      16U - partial_block_len ) );
 }

 void mbedtls_chachapoly_init( mbedtls_chachapoly_context *ctx )
 {
     CHACHAPOLY_VALIDATE( ctx != NULL );

     mbedtls_chacha20_init( &ctx->chacha20_ctx );
     mbedtls_poly1305_init( &ctx->poly1305_ctx );
     ctx->aad_len        = 0U;
     ctx->ciphertext_len = 0U;
     ctx->state          = CHACHAPOLY_STATE_INIT;
     ctx->mode           = MBEDTLS_CHACHAPOLY_ENCRYPT;
 }

 void mbedtls_chachapoly_free( mbedtls_chachapoly_context *ctx )
 {
     if( ctx == NULL )
         return;

     mbedtls_chacha20_free( &ctx->chacha20_ctx );
     mbedtls_poly1305_free( &ctx->poly1305_ctx );
     ctx->aad_len        = 0U;
     ctx->ciphertext_len = 0U;
     ctx->state          = CHACHAPOLY_STATE_INIT;
     ctx->mode           = MBEDTLS_CHACHAPOLY_ENCRYPT;
 }

 int mbedtls_chachapoly_setkey( mbedtls_chachapoly_context *ctx,
                                const unsigned char key[32] )
 {
     int ret;
     CHACHAPOLY_VALIDATE_RET( ctx != NULL );
     CHACHAPOLY_VALIDATE_RET( key != NULL );

     ret = mbedtls_chacha20_setkey( &ctx->chacha20_ctx, key );

     return( ret );
 }

 int mbedtls_chachapoly_starts( mbedtls_chachapoly_context *ctx,
                                const unsigned char nonce[12],
                                mbedtls_chachapoly_mode_t mode  )
 {
     int ret;
     unsigned char poly1305_key[64];
     CHACHAPOLY_VALIDATE_RET( ctx != NULL );
     CHACHAPOLY_VALIDATE_RET( nonce != NULL );

     /* Set counter = 0, will be update to 1 when generating Poly1305 key */
     ret = mbedtls_chacha20_starts( &ctx->chacha20_ctx, nonce, 0U );
     if( ret != 0 )
         goto cleanup;

     /* Generate the Poly1305 key by getting the ChaCha20 keystream output with
      * counter = 0.  This is the same as encrypting a buffer of zeroes.
      * Only the first 256-bits (32 bytes) of the key is used for Poly1305.
      * The other 256 bits are discarded.
      */
     memset( poly1305_key, 0, sizeof( poly1305_key ) );
     ret = mbedtls_chacha20_update( &ctx->chacha20_ctx, sizeof( poly1305_key ),
                                       poly1305_key, poly1305_key );
     if( ret != 0 )
         goto cleanup;

     ret = mbedtls_poly1305_starts( &ctx->poly1305_ctx, poly1305_key );

     if( ret == 0 )
     {
         ctx->aad_len        = 0U;
         ctx->ciphertext_len = 0U;
         ctx->state          = CHACHAPOLY_STATE_AAD;
         ctx->mode           = mode;
     }

 cleanup:
     mbedtls_platform_zeroize( poly1305_key, 64U );
     return( ret );
 }

 int mbedtls_chachapoly_update_aad( mbedtls_chachapoly_context *ctx,
                                    const unsigned char *aad,
                                    size_t aad_len )
 {
     CHACHAPOLY_VALIDATE_RET( ctx != NULL );
     CHACHAPOLY_VALIDATE_RET( aad_len == 0 || aad != NULL );

     if( ctx->state != CHACHAPOLY_STATE_AAD )
         return( MBEDTLS_ERR_CHACHAPOLY_BAD_STATE );

     ctx->aad_len += aad_len;

     return( mbedtls_poly1305_update( &ctx->poly1305_ctx, aad, aad_len ) );
 }

 int mbedtls_chachapoly_update( mbedtls_chachapoly_context *ctx,
                                size_t len,
                                const unsigned char *input,
                                unsigned char *output )
 {
     int ret;
     CHACHAPOLY_VALIDATE_RET( ctx != NULL );
     CHACHAPOLY_VALIDATE_RET( len == 0 || input != NULL );
     CHACHAPOLY_VALIDATE_RET( len == 0 || output != NULL );

     if( ( ctx->state != CHACHAPOLY_STATE_AAD ) &&
         ( ctx->state != CHACHAPOLY_STATE_CIPHERTEXT ) )
     {
         return( MBEDTLS_ERR_CHACHAPOLY_BAD_STATE );
     }

     if( ctx->state == CHACHAPOLY_STATE_AAD )
     {
         ctx->state = CHACHAPOLY_STATE_CIPHERTEXT;

         ret = chachapoly_pad_aad( ctx );
         if( ret != 0 )
             return( ret );
     }

     ctx->ciphertext_len += len;

     if( ctx->mode == MBEDTLS_CHACHAPOLY_ENCRYPT )
     {
         ret = mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
         if( ret != 0 )
             return( ret );

         ret = mbedtls_poly1305_update( &ctx->poly1305_ctx, output, len );
         if( ret != 0 )
             return( ret );
     }
     else /* DECRYPT */
     {
         ret = mbedtls_poly1305_update( &ctx->poly1305_ctx, input, len );
         if( ret != 0 )
             return( ret );

         ret = mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
         if( ret != 0 )
             return( ret );
     }

     return( 0 );
 }

 int mbedtls_chachapoly_finish( mbedtls_chachapoly_context *ctx,
                                unsigned char mac[16] )
 {
     int ret;
     unsigned char len_block[16];
     CHACHAPOLY_VALIDATE_RET( ctx != NULL );
     CHACHAPOLY_VALIDATE_RET( mac != NULL );

     if( ctx->state == CHACHAPOLY_STATE_INIT )
     {
         return( MBEDTLS_ERR_CHACHAPOLY_BAD_STATE );
     }

     if( ctx->state == CHACHAPOLY_STATE_AAD )
     {
         ret = chachapoly_pad_aad( ctx );
         if( ret != 0 )
             return( ret );
     }
     else if( ctx->state == CHACHAPOLY_STATE_CIPHERTEXT )
     {
         ret = chachapoly_pad_ciphertext( ctx );
         if( ret != 0 )
             return( ret );
     }

     ctx->state = CHACHAPOLY_STATE_FINISHED;

     /* The lengths of the AAD and ciphertext are processed by
      * Poly1305 as the final 128-bit block, encoded as little-endian integers.
      */
     len_block[ 0] = (unsigned char)( ctx->aad_len       );
     len_block[ 1] = (unsigned char)( ctx->aad_len >>  8 );
     len_block[ 2] = (unsigned char)( ctx->aad_len >> 16 );
     len_block[ 3] = (unsigned char)( ctx->aad_len >> 24 );
     len_block[ 4] = (unsigned char)( ctx->aad_len >> 32 );
     len_block[ 5] = (unsigned char)( ctx->aad_len >> 40 );
     len_block[ 6] = (unsigned char)( ctx->aad_len >> 48 );
     len_block[ 7] = (unsigned char)( ctx->aad_len >> 56 );
     len_block[ 8] = (unsigned char)( ctx->ciphertext_len       );
     len_block[ 9] = (unsigned char)( ctx->ciphertext_len >>  8 );
     len_block[10] = (unsigned char)( ctx->ciphertext_len >> 16 );
     len_block[11] = (unsigned char)( ctx->ciphertext_len >> 24 );
     len_block[12] = (unsigned char)( ctx->ciphertext_len >> 32 );
     len_block[13] = (unsigned char)( ctx->ciphertext_len >> 40 );
     len_block[14] = (unsigned char)( ctx->ciphertext_len >> 48 );
     len_block[15] = (unsigned char)( ctx->ciphertext_len >> 56 );

     ret = mbedtls_poly1305_update( &ctx->poly1305_ctx, len_block, 16U );
     if( ret != 0 )
         return( ret );

     ret = mbedtls_poly1305_finish( &ctx->poly1305_ctx, mac );

     return( ret );
 }

 static int chachapoly_crypt_and_tag( mbedtls_chachapoly_context *ctx,
                                      mbedtls_chachapoly_mode_t mode,
                                      size_t length,
                                      const unsigned char nonce[12],
                                      const unsigned char *aad,
                                      size_t aad_len,
                                      const unsigned char *input,
                                      unsigned char *output,
                                      unsigned char tag[16] )
 {
     int ret;

     ret = mbedtls_chachapoly_starts( ctx, nonce, mode );
     if( ret != 0 )
         goto cleanup;

     ret = mbedtls_chachapoly_update_aad( ctx, aad, aad_len );
     if( ret != 0 )
         goto cleanup;

     ret = mbedtls_chachapoly_update( ctx, length, input, output );
     if( ret != 0 )
         goto cleanup;

     ret = mbedtls_chachapoly_finish( ctx, tag );

 cleanup:
     return( ret );
 }

 int mbedtls_chachapoly_encrypt_and_tag( mbedtls_chachapoly_context *ctx,
                                         size_t length,
                                         const unsigned char nonce[12],
                                         const unsigned char *aad,
                                         size_t aad_len,
                                         const unsigned char *input,
                                         unsigned char *output,
                                         unsigned char tag[16] )
 {
     CHACHAPOLY_VALIDATE_RET( ctx   != NULL );
     CHACHAPOLY_VALIDATE_RET( nonce != NULL );
     CHACHAPOLY_VALIDATE_RET( tag   != NULL );
     CHACHAPOLY_VALIDATE_RET( aad_len == 0 || aad    != NULL );
     CHACHAPOLY_VALIDATE_RET( length  == 0 || input  != NULL );
     CHACHAPOLY_VALIDATE_RET( length  == 0 || output != NULL );

     return( chachapoly_crypt_and_tag( ctx, MBEDTLS_CHACHAPOLY_ENCRYPT,
                                       length, nonce, aad, aad_len,
                                       input, output, tag ) );
 }

 int mbedtls_chachapoly_auth_decrypt( mbedtls_chachapoly_context *ctx,
                                      size_t length,
                                      const unsigned char nonce[12],
                                      const unsigned char *aad,
                                      size_t aad_len,
                                      const unsigned char tag[16],
                                      const unsigned char *input,
                                      unsigned char *output )
 {
     int ret;
     unsigned char check_tag[16];
     size_t i;
     int diff;
     CHACHAPOLY_VALIDATE_RET( ctx   != NULL );
     CHACHAPOLY_VALIDATE_RET( nonce != NULL );
     CHACHAPOLY_VALIDATE_RET( tag   != NULL );
     CHACHAPOLY_VALIDATE_RET( aad_len == 0 || aad    != NULL );
     CHACHAPOLY_VALIDATE_RET( length  == 0 || input  != NULL );
     CHACHAPOLY_VALIDATE_RET( length  == 0 || output != NULL );

     if( ( ret = chachapoly_crypt_and_tag( ctx,
                         MBEDTLS_CHACHAPOLY_DECRYPT, length, nonce,
                         aad, aad_len, input, output, check_tag ) ) != 0 )
     {
         return( ret );
     }

     /* Check tag in "constant-time" */
     for( diff = 0, i = 0; i < sizeof( check_tag ); i++ )
         diff |= tag[i] ^ check_tag[i];

     if( diff != 0 )
     {
         mbedtls_platform_zeroize( output, length );
         return( MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED );
     }

     return( 0 );
 }

 #endif /* MBEDTLS_CHACHAPOLY_ALT */

 #if defined(MBEDTLS_SELF_TEST)

 static const unsigned char test_key[1][32] =
 {
     {
         0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
         0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
         0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
         0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f
     }
 };

 static const unsigned char test_nonce[1][12] =
 {
     {
         0x07, 0x00, 0x00, 0x00,                         /* 32-bit common part */
         0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47  /* 64-bit IV */
     }
 };

 static const unsigned char test_aad[1][12] =
 {
     {
         0x50, 0x51, 0x52, 0x53, 0xc0, 0xc1, 0xc2, 0xc3,
         0xc4, 0xc5, 0xc6, 0xc7
     }
 };

 static const size_t test_aad_len[1] =
 {
     12U
 };

 static const unsigned char test_input[1][114] =
 {
     {
         0x4c, 0x61, 0x64, 0x69, 0x65, 0x73, 0x20, 0x61,
         0x6e, 0x64, 0x20, 0x47, 0x65, 0x6e, 0x74, 0x6c,
         0x65, 0x6d, 0x65, 0x6e, 0x20, 0x6f, 0x66, 0x20,
         0x74, 0x68, 0x65, 0x20, 0x63, 0x6c, 0x61, 0x73,
         0x73, 0x20, 0x6f, 0x66, 0x20, 0x27, 0x39, 0x39,
         0x3a, 0x20, 0x49, 0x66, 0x20, 0x49, 0x20, 0x63,
         0x6f, 0x75, 0x6c, 0x64, 0x20, 0x6f, 0x66, 0x66,
         0x65, 0x72, 0x20, 0x79, 0x6f, 0x75, 0x20, 0x6f,
         0x6e, 0x6c, 0x79, 0x20, 0x6f, 0x6e, 0x65, 0x20,
         0x74, 0x69, 0x70, 0x20, 0x66, 0x6f, 0x72, 0x20,
         0x74, 0x68, 0x65, 0x20, 0x66, 0x75, 0x74, 0x75,
         0x72, 0x65, 0x2c, 0x20, 0x73, 0x75, 0x6e, 0x73,
         0x63, 0x72, 0x65, 0x65, 0x6e, 0x20, 0x77, 0x6f,
         0x75, 0x6c, 0x64, 0x20, 0x62, 0x65, 0x20, 0x69,
         0x74, 0x2e
     }
 };

 static const unsigned char test_output[1][114] =
 {
     {
         0xd3, 0x1a, 0x8d, 0x34, 0x64, 0x8e, 0x60, 0xdb,
         0x7b, 0x86, 0xaf, 0xbc, 0x53, 0xef, 0x7e, 0xc2,
         0xa4, 0xad, 0xed, 0x51, 0x29, 0x6e, 0x08, 0xfe,
         0xa9, 0xe2, 0xb5, 0xa7, 0x36, 0xee, 0x62, 0xd6,
         0x3d, 0xbe, 0xa4, 0x5e, 0x8c, 0xa9, 0x67, 0x12,
         0x82, 0xfa, 0xfb, 0x69, 0xda, 0x92, 0x72, 0x8b,
         0x1a, 0x71, 0xde, 0x0a, 0x9e, 0x06, 0x0b, 0x29,
         0x05, 0xd6, 0xa5, 0xb6, 0x7e, 0xcd, 0x3b, 0x36,
         0x92, 0xdd, 0xbd, 0x7f, 0x2d, 0x77, 0x8b, 0x8c,
         0x98, 0x03, 0xae, 0xe3, 0x28, 0x09, 0x1b, 0x58,
         0xfa, 0xb3, 0x24, 0xe4, 0xfa, 0xd6, 0x75, 0x94,
         0x55, 0x85, 0x80, 0x8b, 0x48, 0x31, 0xd7, 0xbc,
         0x3f, 0xf4, 0xde, 0xf0, 0x8e, 0x4b, 0x7a, 0x9d,
         0xe5, 0x76, 0xd2, 0x65, 0x86, 0xce, 0xc6, 0x4b,
         0x61, 0x16
     }
 };

 static const size_t test_input_len[1] =
 {
     114U
 };

 static const unsigned char test_mac[1][16] =
 {
     {
         0x1a, 0xe1, 0x0b, 0x59, 0x4f, 0x09, 0xe2, 0x6a,
         0x7e, 0x90, 0x2e, 0xcb, 0xd0, 0x60, 0x06, 0x91
     }
 };

 #define ASSERT( cond, args )            \
     do                                  \
     {                                   \
         if( ! ( cond ) )                \
         {                               \
             if( verbose != 0 )          \
                 mbedtls_printf args;    \
                                         \
             return( -1 );               \
         }                               \
     }                                   \
     while( 0 )

 int mbedtls_chachapoly_self_test( int verbose )
 {
     mbedtls_chachapoly_context ctx;
     unsigned i;
     int ret;
     unsigned char output[200];
     unsigned char mac[16];

     for( i = 0U; i < 1U; i++ )
     {
         if( verbose != 0 )
             mbedtls_printf( "  ChaCha20-Poly1305 test %u ", i );

         mbedtls_chachapoly_init( &ctx );

         ret = mbedtls_chachapoly_setkey( &ctx, test_key[i] );
         ASSERT( 0 == ret, ( "setkey() error code: %i\n", ret ) );

         ret = mbedtls_chachapoly_encrypt_and_tag( &ctx,
                                                   test_input_len[i],
                                                   test_nonce[i],
                                                   test_aad[i],
                                                   test_aad_len[i],
                                                   test_input[i],
                                                   output,
                                                   mac );

         ASSERT( 0 == ret, ( "crypt_and_tag() error code: %i\n", ret ) );

         ASSERT( 0 == memcmp( output, test_output[i], test_input_len[i] ),
                 ( "failure (wrong output)\n" ) );

         ASSERT( 0 == memcmp( mac, test_mac[i], 16U ),
                 ( "failure (wrong MAC)\n" ) );

         mbedtls_chachapoly_free( &ctx );

         if( verbose != 0 )
             mbedtls_printf( "passed\n" );
     }

     if( verbose != 0 )
         mbedtls_printf( "\n" );

     return( 0 );
 }

 #endif /* MBEDTLS_SELF_TEST */

 #endif /* MBEDTLS_CHACHAPOLY_C */
	/**
	* \file chachapoly.c
	*
	* \brief ChaCha20-Poly1305 AEAD construction based on RFC 7539.
	*
	* Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
	* SPDX-License-Identifier: Apache-2.0
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may
	* not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*
	* This file is part of mbed TLS (https://tls.mbed.org)
	*/
	#if !defined(MBEDTLS_CONFIG_FILE)
	#include "mbedtls/config.h"
	#else
	#include MBEDTLS_CONFIG_FILE
	#endif

	#if defined(MBEDTLS_CHACHAPOLY_C)

	#include "mbedtls/chachapoly.h"
	#include "mbedtls/platform_util.h"

	#include <string.h>

	#if defined(MBEDTLS_SELF_TEST)
	#if defined(MBEDTLS_PLATFORM_C)
	#include "mbedtls/platform.h"
	#else
	#include <stdio.h>
	#define mbedtls_printf printf
	#endif /* MBEDTLS_PLATFORM_C */
	#endif /* MBEDTLS_SELF_TEST */

	#if !defined(MBEDTLS_CHACHAPOLY_ALT)

	/* Parameter validation macros */
	#define CHACHAPOLY_VALIDATE_RET( cond ) \
	MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA )
	#define CHACHAPOLY_VALIDATE( cond ) \
	MBEDTLS_INTERNAL_VALIDATE( cond )

	#define CHACHAPOLY_STATE_INIT ( 0 )
	#define CHACHAPOLY_STATE_AAD ( 1 )
	#define CHACHAPOLY_STATE_CIPHERTEXT ( 2 ) /* Encrypting or decrypting */
	#define CHACHAPOLY_STATE_FINISHED ( 3 )

	/**
	* \brief Adds nul bytes to pad the AAD for Poly1305.
	*
	* \param ctx The ChaCha20-Poly1305 context.
	*/
	static int chachapoly_pad_aad( mbedtls_chachapoly_context *ctx )
	{
	uint32_t partial_block_len = (uint32_t) ( ctx->aad_len % 16U );
	unsigned char zeroes[15];

	if( partial_block_len == 0U )
	return( 0 );

	memset( zeroes, 0, sizeof( zeroes ) );

	return( mbedtls_poly1305_update( &ctx->poly1305_ctx,
	zeroes,
	16U - partial_block_len ) );
	}

	/**
	* \brief Adds nul bytes to pad the ciphertext for Poly1305.
	*
	* \param ctx The ChaCha20-Poly1305 context.
	*/
	static int chachapoly_pad_ciphertext( mbedtls_chachapoly_context *ctx )
	{
	uint32_t partial_block_len = (uint32_t) ( ctx->ciphertext_len % 16U );
	unsigned char zeroes[15];

	if( partial_block_len == 0U )
	return( 0 );

	memset( zeroes, 0, sizeof( zeroes ) );
	return( mbedtls_poly1305_update( &ctx->poly1305_ctx,
	zeroes,
	16U - partial_block_len ) );
	}

	void mbedtls_chachapoly_init( mbedtls_chachapoly_context *ctx )
	{
	CHACHAPOLY_VALIDATE( ctx != NULL );

	mbedtls_chacha20_init( &ctx->chacha20_ctx );
	mbedtls_poly1305_init( &ctx->poly1305_ctx );
	ctx->aad_len = 0U;
	ctx->ciphertext_len = 0U;
	ctx->state = CHACHAPOLY_STATE_INIT;
	ctx->mode = MBEDTLS_CHACHAPOLY_ENCRYPT;
	}

	void mbedtls_chachapoly_free( mbedtls_chachapoly_context *ctx )
	{
	if( ctx == NULL )
	return;

	mbedtls_chacha20_free( &ctx->chacha20_ctx );
	mbedtls_poly1305_free( &ctx->poly1305_ctx );
	ctx->aad_len = 0U;
	ctx->ciphertext_len = 0U;
	ctx->state = CHACHAPOLY_STATE_INIT;
	ctx->mode = MBEDTLS_CHACHAPOLY_ENCRYPT;
	}

	int mbedtls_chachapoly_setkey( mbedtls_chachapoly_context *ctx,
	const unsigned char key[32] )
	{
	int ret;
	CHACHAPOLY_VALIDATE_RET( ctx != NULL );
	CHACHAPOLY_VALIDATE_RET( key != NULL );

	ret = mbedtls_chacha20_setkey( &ctx->chacha20_ctx, key );

	return( ret );
	}

	int mbedtls_chachapoly_starts( mbedtls_chachapoly_context *ctx,
	const unsigned char nonce[12],
	mbedtls_chachapoly_mode_t mode )
	{
	int ret;
	unsigned char poly1305_key[64];
	CHACHAPOLY_VALIDATE_RET( ctx != NULL );
	CHACHAPOLY_VALIDATE_RET( nonce != NULL );

	/* Set counter = 0, will be update to 1 when generating Poly1305 key */
	ret = mbedtls_chacha20_starts( &ctx->chacha20_ctx, nonce, 0U );
	if( ret != 0 )
	goto cleanup;

	/* Generate the Poly1305 key by getting the ChaCha20 keystream output with
	* counter = 0. This is the same as encrypting a buffer of zeroes.
	* Only the first 256-bits (32 bytes) of the key is used for Poly1305.
	* The other 256 bits are discarded.
	*/
	memset( poly1305_key, 0, sizeof( poly1305_key ) );
	ret = mbedtls_chacha20_update( &ctx->chacha20_ctx, sizeof( poly1305_key ),
	poly1305_key, poly1305_key );
	if( ret != 0 )
	goto cleanup;

	ret = mbedtls_poly1305_starts( &ctx->poly1305_ctx, poly1305_key );

	if( ret == 0 )
	{
	ctx->aad_len = 0U;
	ctx->ciphertext_len = 0U;
	ctx->state = CHACHAPOLY_STATE_AAD;
	ctx->mode = mode;
	}

	cleanup:
	mbedtls_platform_zeroize( poly1305_key, 64U );
	return( ret );
	}

	int mbedtls_chachapoly_update_aad( mbedtls_chachapoly_context *ctx,
	const unsigned char *aad,
	size_t aad_len )
	{
	CHACHAPOLY_VALIDATE_RET( ctx != NULL );
	CHACHAPOLY_VALIDATE_RET( aad_len == 0 \|\| aad != NULL );

	if( ctx->state != CHACHAPOLY_STATE_AAD )
	return( MBEDTLS_ERR_CHACHAPOLY_BAD_STATE );

	ctx->aad_len += aad_len;

	return( mbedtls_poly1305_update( &ctx->poly1305_ctx, aad, aad_len ) );
	}

	int mbedtls_chachapoly_update( mbedtls_chachapoly_context *ctx,
	size_t len,
	const unsigned char *input,
	unsigned char *output )
	{
	int ret;
	CHACHAPOLY_VALIDATE_RET( ctx != NULL );
	CHACHAPOLY_VALIDATE_RET( len == 0 \|\| input != NULL );
	CHACHAPOLY_VALIDATE_RET( len == 0 \|\| output != NULL );

	if( ( ctx->state != CHACHAPOLY_STATE_AAD ) &&
	( ctx->state != CHACHAPOLY_STATE_CIPHERTEXT ) )
	{
	return( MBEDTLS_ERR_CHACHAPOLY_BAD_STATE );
	}

	if( ctx->state == CHACHAPOLY_STATE_AAD )
	{
	ctx->state = CHACHAPOLY_STATE_CIPHERTEXT;

	ret = chachapoly_pad_aad( ctx );
	if( ret != 0 )
	return( ret );
	}

	ctx->ciphertext_len += len;

	if( ctx->mode == MBEDTLS_CHACHAPOLY_ENCRYPT )
	{
	ret = mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
	if( ret != 0 )
	return( ret );

	ret = mbedtls_poly1305_update( &ctx->poly1305_ctx, output, len );
	if( ret != 0 )
	return( ret );
	}
	else /* DECRYPT */
	{
	ret = mbedtls_poly1305_update( &ctx->poly1305_ctx, input, len );
	if( ret != 0 )
	return( ret );

	ret = mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
	if( ret != 0 )
	return( ret );
	}

	return( 0 );
	}

	int mbedtls_chachapoly_finish( mbedtls_chachapoly_context *ctx,
	unsigned char mac[16] )
	{
	int ret;
	unsigned char len_block[16];
	CHACHAPOLY_VALIDATE_RET( ctx != NULL );
	CHACHAPOLY_VALIDATE_RET( mac != NULL );

	if( ctx->state == CHACHAPOLY_STATE_INIT )
	{
	return( MBEDTLS_ERR_CHACHAPOLY_BAD_STATE );
	}

	if( ctx->state == CHACHAPOLY_STATE_AAD )
	{
	ret = chachapoly_pad_aad( ctx );
	if( ret != 0 )
	return( ret );
	}
	else if( ctx->state == CHACHAPOLY_STATE_CIPHERTEXT )
	{
	ret = chachapoly_pad_ciphertext( ctx );
	if( ret != 0 )
	return( ret );
	}

	ctx->state = CHACHAPOLY_STATE_FINISHED;

	/* The lengths of the AAD and ciphertext are processed by
	* Poly1305 as the final 128-bit block, encoded as little-endian integers.
	*/
	len_block[ 0] = (unsigned char)( ctx->aad_len );
	len_block[ 1] = (unsigned char)( ctx->aad_len >> 8 );
	len_block[ 2] = (unsigned char)( ctx->aad_len >> 16 );
	len_block[ 3] = (unsigned char)( ctx->aad_len >> 24 );
	len_block[ 4] = (unsigned char)( ctx->aad_len >> 32 );
	len_block[ 5] = (unsigned char)( ctx->aad_len >> 40 );
	len_block[ 6] = (unsigned char)( ctx->aad_len >> 48 );
	len_block[ 7] = (unsigned char)( ctx->aad_len >> 56 );
	len_block[ 8] = (unsigned char)( ctx->ciphertext_len );
	len_block[ 9] = (unsigned char)( ctx->ciphertext_len >> 8 );
	len_block[10] = (unsigned char)( ctx->ciphertext_len >> 16 );
	len_block[11] = (unsigned char)( ctx->ciphertext_len >> 24 );
	len_block[12] = (unsigned char)( ctx->ciphertext_len >> 32 );
	len_block[13] = (unsigned char)( ctx->ciphertext_len >> 40 );
	len_block[14] = (unsigned char)( ctx->ciphertext_len >> 48 );
	len_block[15] = (unsigned char)( ctx->ciphertext_len >> 56 );

	ret = mbedtls_poly1305_update( &ctx->poly1305_ctx, len_block, 16U );
	if( ret != 0 )
	return( ret );

	ret = mbedtls_poly1305_finish( &ctx->poly1305_ctx, mac );

	return( ret );
	}

	static int chachapoly_crypt_and_tag( mbedtls_chachapoly_context *ctx,
	mbedtls_chachapoly_mode_t mode,
	size_t length,
	const unsigned char nonce[12],
	const unsigned char *aad,
	size_t aad_len,
	const unsigned char *input,
	unsigned char *output,
	unsigned char tag[16] )
	{
	int ret;

	ret = mbedtls_chachapoly_starts( ctx, nonce, mode );
	if( ret != 0 )
	goto cleanup;

	ret = mbedtls_chachapoly_update_aad( ctx, aad, aad_len );
	if( ret != 0 )
	goto cleanup;

	ret = mbedtls_chachapoly_update( ctx, length, input, output );
	if( ret != 0 )
	goto cleanup;

	ret = mbedtls_chachapoly_finish( ctx, tag );

	cleanup:
	return( ret );
	}

	int mbedtls_chachapoly_encrypt_and_tag( mbedtls_chachapoly_context *ctx,
	size_t length,
	const unsigned char nonce[12],
	const unsigned char *aad,
	size_t aad_len,
	const unsigned char *input,
	unsigned char *output,
	unsigned char tag[16] )
	{
	CHACHAPOLY_VALIDATE_RET( ctx != NULL );
	CHACHAPOLY_VALIDATE_RET( nonce != NULL );
	CHACHAPOLY_VALIDATE_RET( tag != NULL );
	CHACHAPOLY_VALIDATE_RET( aad_len == 0 \|\| aad != NULL );
	CHACHAPOLY_VALIDATE_RET( length == 0 \|\| input != NULL );
	CHACHAPOLY_VALIDATE_RET( length == 0 \|\| output != NULL );

	return( chachapoly_crypt_and_tag( ctx, MBEDTLS_CHACHAPOLY_ENCRYPT,
	length, nonce, aad, aad_len,
	input, output, tag ) );
	}

	int mbedtls_chachapoly_auth_decrypt( mbedtls_chachapoly_context *ctx,
	size_t length,
	const unsigned char nonce[12],
	const unsigned char *aad,
	size_t aad_len,
	const unsigned char tag[16],
	const unsigned char *input,
	unsigned char *output )
	{
	int ret;
	unsigned char check_tag[16];
	size_t i;
	int diff;
	CHACHAPOLY_VALIDATE_RET( ctx != NULL );
	CHACHAPOLY_VALIDATE_RET( nonce != NULL );
	CHACHAPOLY_VALIDATE_RET( tag != NULL );
	CHACHAPOLY_VALIDATE_RET( aad_len == 0 \|\| aad != NULL );
	CHACHAPOLY_VALIDATE_RET( length == 0 \|\| input != NULL );
	CHACHAPOLY_VALIDATE_RET( length == 0 \|\| output != NULL );

	if( ( ret = chachapoly_crypt_and_tag( ctx,
	MBEDTLS_CHACHAPOLY_DECRYPT, length, nonce,
	aad, aad_len, input, output, check_tag ) ) != 0 )
	{
	return( ret );
	}

	/* Check tag in "constant-time" */
	for( diff = 0, i = 0; i < sizeof( check_tag ); i++ )
	diff \|= tag[i] ^ check_tag[i];

	if( diff != 0 )
	{
	mbedtls_platform_zeroize( output, length );
	return( MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED );
	}

	return( 0 );
	}

	#endif /* MBEDTLS_CHACHAPOLY_ALT */

	#if defined(MBEDTLS_SELF_TEST)

	static const unsigned char test_key[1][32] =
	{
	{
	0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
	0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
	0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
	0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f
	}
	};

	static const unsigned char test_nonce[1][12] =
	{
	{
	0x07, 0x00, 0x00, 0x00, /* 32-bit common part */
	0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47 /* 64-bit IV */
	}
	};

	static const unsigned char test_aad[1][12] =
	{
	{
	0x50, 0x51, 0x52, 0x53, 0xc0, 0xc1, 0xc2, 0xc3,
	0xc4, 0xc5, 0xc6, 0xc7
	}
	};

	static const size_t test_aad_len[1] =
	{
	12U
	};

	static const unsigned char test_input[1][114] =
	{
	{
	0x4c, 0x61, 0x64, 0x69, 0x65, 0x73, 0x20, 0x61,
	0x6e, 0x64, 0x20, 0x47, 0x65, 0x6e, 0x74, 0x6c,
	0x65, 0x6d, 0x65, 0x6e, 0x20, 0x6f, 0x66, 0x20,
	0x74, 0x68, 0x65, 0x20, 0x63, 0x6c, 0x61, 0x73,
	0x73, 0x20, 0x6f, 0x66, 0x20, 0x27, 0x39, 0x39,
	0x3a, 0x20, 0x49, 0x66, 0x20, 0x49, 0x20, 0x63,
	0x6f, 0x75, 0x6c, 0x64, 0x20, 0x6f, 0x66, 0x66,
	0x65, 0x72, 0x20, 0x79, 0x6f, 0x75, 0x20, 0x6f,
	0x6e, 0x6c, 0x79, 0x20, 0x6f, 0x6e, 0x65, 0x20,
	0x74, 0x69, 0x70, 0x20, 0x66, 0x6f, 0x72, 0x20,
	0x74, 0x68, 0x65, 0x20, 0x66, 0x75, 0x74, 0x75,
	0x72, 0x65, 0x2c, 0x20, 0x73, 0x75, 0x6e, 0x73,
	0x63, 0x72, 0x65, 0x65, 0x6e, 0x20, 0x77, 0x6f,
	0x75, 0x6c, 0x64, 0x20, 0x62, 0x65, 0x20, 0x69,
	0x74, 0x2e
	}
	};

	static const unsigned char test_output[1][114] =
	{
	{
	0xd3, 0x1a, 0x8d, 0x34, 0x64, 0x8e, 0x60, 0xdb,
	0x7b, 0x86, 0xaf, 0xbc, 0x53, 0xef, 0x7e, 0xc2,
	0xa4, 0xad, 0xed, 0x51, 0x29, 0x6e, 0x08, 0xfe,
	0xa9, 0xe2, 0xb5, 0xa7, 0x36, 0xee, 0x62, 0xd6,
	0x3d, 0xbe, 0xa4, 0x5e, 0x8c, 0xa9, 0x67, 0x12,
	0x82, 0xfa, 0xfb, 0x69, 0xda, 0x92, 0x72, 0x8b,
	0x1a, 0x71, 0xde, 0x0a, 0x9e, 0x06, 0x0b, 0x29,
	0x05, 0xd6, 0xa5, 0xb6, 0x7e, 0xcd, 0x3b, 0x36,
	0x92, 0xdd, 0xbd, 0x7f, 0x2d, 0x77, 0x8b, 0x8c,
	0x98, 0x03, 0xae, 0xe3, 0x28, 0x09, 0x1b, 0x58,
	0xfa, 0xb3, 0x24, 0xe4, 0xfa, 0xd6, 0x75, 0x94,
	0x55, 0x85, 0x80, 0x8b, 0x48, 0x31, 0xd7, 0xbc,
	0x3f, 0xf4, 0xde, 0xf0, 0x8e, 0x4b, 0x7a, 0x9d,
	0xe5, 0x76, 0xd2, 0x65, 0x86, 0xce, 0xc6, 0x4b,
	0x61, 0x16
	}
	};

	static const size_t test_input_len[1] =
	{
	114U
	};

	static const unsigned char test_mac[1][16] =
	{
	{
	0x1a, 0xe1, 0x0b, 0x59, 0x4f, 0x09, 0xe2, 0x6a,
	0x7e, 0x90, 0x2e, 0xcb, 0xd0, 0x60, 0x06, 0x91
	}
	};

	#define ASSERT( cond, args ) \
	do \
	{ \
	if( ! ( cond ) ) \
	{ \
	if( verbose != 0 ) \
	mbedtls_printf args; \
	\
	return( -1 ); \
	} \
	} \
	while( 0 )

	int mbedtls_chachapoly_self_test( int verbose )
	{
	mbedtls_chachapoly_context ctx;
	unsigned i;
	int ret;
	unsigned char output[200];
	unsigned char mac[16];

	for( i = 0U; i < 1U; i++ )
	{
	if( verbose != 0 )
	mbedtls_printf( " ChaCha20-Poly1305 test %u ", i );

	mbedtls_chachapoly_init( &ctx );

	ret = mbedtls_chachapoly_setkey( &ctx, test_key[i] );
	ASSERT( 0 == ret, ( "setkey() error code: %i\n", ret ) );

	ret = mbedtls_chachapoly_encrypt_and_tag( &ctx,
	test_input_len[i],
	test_nonce[i],
	test_aad[i],
	test_aad_len[i],
	test_input[i],
	output,
	mac );

	ASSERT( 0 == ret, ( "crypt_and_tag() error code: %i\n", ret ) );

	ASSERT( 0 == memcmp( output, test_output[i], test_input_len[i] ),
	( "failure (wrong output)\n" ) );

	ASSERT( 0 == memcmp( mac, test_mac[i], 16U ),
	( "failure (wrong MAC)\n" ) );

	mbedtls_chachapoly_free( &ctx );

	if( verbose != 0 )
	mbedtls_printf( "passed\n" );
	}

	if( verbose != 0 )
	mbedtls_printf( "\n" );

	return( 0 );
	}

	#endif /* MBEDTLS_SELF_TEST */

	#endif /* MBEDTLS_CHACHAPOLY_C */