Implement AEAD-ChaCha20-Poly1305.
This implementation is based off the description in RFC 7539.
The ChaCha20 code is also updated to provide a means of generating
keystream blocks with arbitrary counter values. This is used to
generated the one-time Poly1305 key in the AEAD construction.
diff --git a/library/aead_chacha20_poly1305.c b/library/aead_chacha20_poly1305.c
new file mode 100644
index 0000000..ab29dfa
--- /dev/null
+++ b/library/aead_chacha20_poly1305.c
@@ -0,0 +1,463 @@
+/**
+ * \file aead_chacha20_poly1305.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_AEAD_CHACHA20_POLY1305_C)
+
+#include "mbedtls/aead_chacha20_poly1305.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_AEAD_CHACHA20_POLY1305_ALT)
+
+#define AEAD_CHACHA20_POLY1305_STATE_INIT ( 0 )
+#define AEAD_CHACHA20_POLY1305_STATE_AAD ( 1 )
+#define AEAD_CHACHA20_POLY1305_STATE_CIPHERTEXT ( 2 ) /* Encrypting or decrypting */
+#define AEAD_CHACHA20_POLY1305_STATE_FINISHED ( 3 )
+
+/* Implementation that should never be optimized out by the compiler */
+static void mbedtls_zeroize( void *v, size_t n ) {
+ volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+}
+
+/**
+ * \brief Adds padding bytes (zeroes) to pad the AAD for Poly1305.
+ *
+ * \param ctx The ChaCha20-Poly1305 context.
+ */
+static void mbedtls_aead_chacha20_poly1305_pad_aad( mbedtls_aead_chacha20_poly1305_context *ctx )
+{
+ uint32_t partial_block_len = (uint32_t)( ctx->aad_len % 16U );
+ unsigned char zeroes[15];
+
+ if ( partial_block_len > 0U )
+ {
+ memset( zeroes, 0, sizeof(zeroes) );
+ (void)mbedtls_poly1305_update( &ctx->poly1305_ctx,
+ 16U - partial_block_len,
+ zeroes );
+ }
+}
+
+/**
+ * \brief Adds padding bytes (zeroes) to pad the ciphertext for Poly1305.
+ *
+ * \param ctx The ChaCha20-Poly1305 context.
+ */
+static void mbedtls_aead_chacha20_poly1305_pad_ciphertext( mbedtls_aead_chacha20_poly1305_context *ctx )
+{
+ uint32_t partial_block_len = (uint32_t)( ctx->ciphertext_len % 16U );
+ unsigned char zeroes[15];
+
+ if ( partial_block_len > 0U )
+ {
+ memset( zeroes, 0, sizeof(zeroes) );
+ (void)mbedtls_poly1305_update( &ctx->poly1305_ctx,
+ 16U - partial_block_len,
+ zeroes );
+ }
+}
+
+void mbedtls_aead_chacha20_poly1305_init( mbedtls_aead_chacha20_poly1305_context *ctx )
+{
+ if ( ctx != NULL )
+ {
+ mbedtls_chacha20_init( &ctx->chacha20_ctx );
+ mbedtls_poly1305_init( &ctx->poly1305_ctx );
+ ctx->aad_len = 0U;
+ ctx->ciphertext_len = 0U;
+ ctx->state = AEAD_CHACHA20_POLY1305_STATE_INIT;
+ ctx->mode = MBEDTLS_AEAD_CHACHA20_POLY1305_ENCRYPT;
+ }
+}
+
+void mbedtls_aead_chacha20_poly1305_free( mbedtls_aead_chacha20_poly1305_context *ctx )
+{
+ if ( ctx != NULL )
+ {
+ mbedtls_chacha20_free( &ctx->chacha20_ctx );
+ mbedtls_poly1305_free( &ctx->poly1305_ctx );
+ ctx->aad_len = 0U;
+ ctx->ciphertext_len = 0U;
+ ctx->state = AEAD_CHACHA20_POLY1305_STATE_INIT;
+ ctx->mode = MBEDTLS_AEAD_CHACHA20_POLY1305_ENCRYPT;
+ }
+}
+
+int mbedtls_aead_chacha20_poly1305_setkey( mbedtls_aead_chacha20_poly1305_context *ctx,
+ const unsigned char key[32] )
+{
+ int result;
+
+ if ( ( ctx == NULL ) || ( key == NULL ) )
+ {
+ return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+ }
+
+ result = mbedtls_chacha20_setkey( &ctx->chacha20_ctx, key );
+
+ return( result );
+}
+
+int mbedtls_aead_chacha20_poly1305_starts( mbedtls_aead_chacha20_poly1305_context *ctx,
+ const unsigned char nonce[12],
+ mbedtls_aead_chacha20_poly1305_mode_t mode )
+{
+ int result;
+ unsigned char poly1305_key[64];
+
+ if ( ( ctx == NULL ) || ( nonce == NULL ) )
+ {
+ return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+ }
+
+ result = mbedtls_chacha20_starts( &ctx->chacha20_ctx, nonce, 1U );
+ if ( result != 0 )
+ goto cleanup;
+
+ /* Generate the Poly1305 key by getting the ChaCha20 keystream output with counter = 0.
+ * Only the first 256-bits (32 bytes) of the key is used for Poly1305.
+ * The other 256 bits are discarded.
+ */
+ result = mbedtls_chacha20_keystream_block( &ctx->chacha20_ctx, 0U, poly1305_key );
+ if ( result != 0 )
+ goto cleanup;
+
+ result = mbedtls_poly1305_setkey( &ctx->poly1305_ctx, poly1305_key );
+
+ if ( result == 0 )
+ {
+ ctx->aad_len = 0U;
+ ctx->ciphertext_len = 0U;
+ ctx->state = AEAD_CHACHA20_POLY1305_STATE_AAD;
+ ctx->mode = mode;
+ }
+
+cleanup:
+ mbedtls_zeroize( poly1305_key, 64U );
+ return( result );
+}
+
+int mbedtls_aead_chacha20_poly1305_update_aad( mbedtls_aead_chacha20_poly1305_context *ctx,
+ size_t aad_len,
+ const unsigned char *aad )
+{
+ if ( ( ctx == NULL ) || ( aad == NULL ) )
+ {
+ return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+ }
+ else if ( ctx->state != AEAD_CHACHA20_POLY1305_STATE_AAD )
+ {
+ return (MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_STATE );
+ }
+
+ ctx->aad_len += aad_len;
+
+ return ( mbedtls_poly1305_update( &ctx->poly1305_ctx, aad_len, aad ) );
+}
+
+int mbedtls_aead_chacha20_poly1305_update( mbedtls_aead_chacha20_poly1305_context *ctx,
+ size_t len,
+ const unsigned char *input,
+ unsigned char *output )
+{
+ if ( ( ctx == NULL ) || ( input == NULL ) || ( output == NULL ) )
+ {
+ return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+ }
+ else if ( ( ctx->state != AEAD_CHACHA20_POLY1305_STATE_AAD ) &&
+ ( ctx->state != AEAD_CHACHA20_POLY1305_STATE_CIPHERTEXT ) )
+ {
+ return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_STATE );
+ }
+
+ if ( ctx->state == AEAD_CHACHA20_POLY1305_STATE_AAD )
+ {
+ ctx->state = AEAD_CHACHA20_POLY1305_STATE_CIPHERTEXT;
+
+ mbedtls_aead_chacha20_poly1305_pad_aad( ctx );
+ }
+
+ ctx->ciphertext_len += len;
+
+ if ( ctx->mode == MBEDTLS_AEAD_CHACHA20_POLY1305_ENCRYPT )
+ {
+ /* Note: the following functions return an error only if one or more of
+ * the input pointers are NULL. Since we have checked their validity
+ * above, we can safety ignore the return value.
+ */
+ (void)mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
+ (void)mbedtls_poly1305_update( &ctx->poly1305_ctx, len, output );
+ }
+ else /* DECRYPT */
+ {
+ (void)mbedtls_poly1305_update( &ctx->poly1305_ctx, len, input );
+ (void)mbedtls_chacha20_update( &ctx->chacha20_ctx, len, input, output );
+ }
+
+ return( 0 );
+}
+
+int mbedtls_aead_chacha20_poly1305_finish( mbedtls_aead_chacha20_poly1305_context *ctx,
+ unsigned char mac[16] )
+{
+ unsigned char len_block[16];
+
+ if ( ( ctx == NULL ) || ( mac == NULL ) )
+ {
+ return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_INPUT_DATA );
+ }
+ else if ( ctx->state == AEAD_CHACHA20_POLY1305_STATE_INIT )
+ {
+ return( MBEDTLS_ERR_AEAD_CHACHA20_POLY1305_BAD_STATE );
+ }
+
+ if ( ctx->state == AEAD_CHACHA20_POLY1305_STATE_AAD )
+ {
+ mbedtls_aead_chacha20_poly1305_pad_aad( ctx );
+ }
+ else if ( ctx->state == AEAD_CHACHA20_POLY1305_STATE_CIPHERTEXT )
+ {
+ mbedtls_aead_chacha20_poly1305_pad_ciphertext( ctx );
+ }
+
+ ctx->state = AEAD_CHACHA20_POLY1305_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 );
+
+ (void)mbedtls_poly1305_update( &ctx->poly1305_ctx, 16U, len_block );
+ (void)mbedtls_poly1305_finish( &ctx->poly1305_ctx, mac );
+
+ return( 0 );
+}
+
+#endif /* MBEDTLS_AEAD_CHACHA20_POLY1305_ALT */
+
+int mbedtls_aead_chacha20_poly1305_crypt_and_mac ( const unsigned char key[32],
+ const unsigned char nonce[12],
+ mbedtls_aead_chacha20_poly1305_mode_t mode,
+ size_t aad_len,
+ const unsigned char *aad,
+ size_t ilen,
+ const unsigned char *input,
+ unsigned char *output,
+ unsigned char mac[16] )
+{
+ mbedtls_aead_chacha20_poly1305_context ctx;
+ int result;
+
+ mbedtls_aead_chacha20_poly1305_init( &ctx );
+
+ result = mbedtls_aead_chacha20_poly1305_setkey( &ctx, key );
+ if ( result != 0 )
+ goto cleanup;
+
+ result = mbedtls_aead_chacha20_poly1305_starts( &ctx, nonce, mode );
+ if ( result != 0 )
+ goto cleanup;
+
+ result = mbedtls_aead_chacha20_poly1305_update_aad( &ctx, aad_len, aad );
+ if ( result != 0 )
+ goto cleanup;
+
+ result = mbedtls_aead_chacha20_poly1305_update( &ctx, ilen, input, output );
+ if ( result != 0 )
+ goto cleanup;
+
+ result = mbedtls_aead_chacha20_poly1305_finish( &ctx, mac );
+
+cleanup:
+ mbedtls_aead_chacha20_poly1305_free( &ctx );
+ return( result );
+}
+
+#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
+ }
+};
+
+int mbedtls_aead_chacha20_poly1305_self_test( int verbose )
+{
+ size_t i;
+ int result;
+ unsigned char output[200];
+ unsigned char mac[16];
+
+ for ( i = 0U; i < 1U; i++ )
+ {
+ result = mbedtls_aead_chacha20_poly1305_crypt_and_mac( test_key[i],
+ test_nonce[i],
+ MBEDTLS_AEAD_CHACHA20_POLY1305_ENCRYPT,
+ test_aad_len[i],
+ test_aad[i],
+ test_input_len[i],
+ test_input[i],
+ output,
+ mac );
+ if ( result != 0 )
+ {
+ if ( verbose != 0 )
+ {
+ mbedtls_printf( "ChaCha20-Poly1305 test %zi error code: %i\n", i, result );
+ }
+ return( -1 );
+ }
+
+ if ( memcmp( output, test_output[i], test_input_len[i] ) != 0 )
+ {
+ if ( verbose != 0 )
+ {
+ mbedtls_printf( "ChaCha20-Poly1305 test %zi failure (wrong output)\n", i );
+ }
+ return( -1 );
+ }
+
+ if ( memcmp( mac, test_mac[i], 16U ) != 0 )
+ {
+ if ( verbose != 0 )
+ {
+ mbedtls_printf( "ChaCha20-Poly1305 test %zi failure (wrong MAC)\n", i );
+ }
+ return( -1 );
+ }
+ }
+
+ return( 0 );
+}
+
+#endif /* MBEDTLS_SELF_TEST */
+
+#endif /* MBEDTLS_AEAD_CHACHA20_POLY1305_C */