X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/39cc1c879e3d75b3cafd79e4e139a7f6673dd349..700d8687944db0a48535f818b59b6c9859952c61:/common/mbedtls/cipher.c?ds=inline

diff --git a/common/mbedtls/cipher.c b/common/mbedtls/cipher.c
new file mode 100644
index 00000000..de9402a2
--- /dev/null
+++ b/common/mbedtls/cipher.c
@@ -0,0 +1,1108 @@
+/**
+ * \file cipher.c
+ *
+ * \brief Generic cipher wrapper for mbed TLS
+ *
+ * \author Adriaan de Jong <dejong@fox-it.com>
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: GPL-2.0
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ *  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_CIPHER_C)
+
+#include "mbedtls/cipher.h"
+#include "mbedtls/cipher_internal.h"
+#include "mbedtls/platform_util.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#if defined(MBEDTLS_CHACHAPOLY_C)
+#include "mbedtls/chachapoly.h"
+#endif
+
+#if defined(MBEDTLS_GCM_C)
+#include "mbedtls/gcm.h"
+#endif
+
+#if defined(MBEDTLS_CCM_C)
+#include "mbedtls/ccm.h"
+#endif
+
+#if defined(MBEDTLS_CHACHA20_C)
+#include "mbedtls/chacha20.h"
+#endif
+
+#if defined(MBEDTLS_CMAC_C)
+#include "mbedtls/cmac.h"
+#endif
+
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#define mbedtls_calloc calloc
+#define mbedtls_free   free
+#endif
+
+#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
+/* Compare the contents of two buffers in constant time.
+ * Returns 0 if the contents are bitwise identical, otherwise returns
+ * a non-zero value.
+ * This is currently only used by GCM and ChaCha20+Poly1305.
+ */
+static int mbedtls_constant_time_memcmp( const void *v1, const void *v2, size_t len )
+{
+    const unsigned char *p1 = (const unsigned char*) v1;
+    const unsigned char *p2 = (const unsigned char*) v2;
+    size_t i;
+    unsigned char diff;
+
+    for( diff = 0, i = 0; i < len; i++ )
+        diff |= p1[i] ^ p2[i];
+
+    return (int)diff;
+}
+#endif /* MBEDTLS_GCM_C || MBEDTLS_CHACHAPOLY_C */
+
+static int supported_init = 0;
+
+const int *mbedtls_cipher_list( void )
+{
+    const mbedtls_cipher_definition_t *def;
+    int *type;
+
+    if( ! supported_init )
+    {
+        def = mbedtls_cipher_definitions;
+        type = mbedtls_cipher_supported;
+
+        while( def->type != 0 )
+            *type++ = (*def++).type;
+
+        *type = 0;
+
+        supported_init = 1;
+    }
+
+    return( mbedtls_cipher_supported );
+}
+
+const mbedtls_cipher_info_t *mbedtls_cipher_info_from_type( const mbedtls_cipher_type_t cipher_type )
+{
+    const mbedtls_cipher_definition_t *def;
+
+    for( def = mbedtls_cipher_definitions; def->info != NULL; def++ )
+        if( def->type == cipher_type )
+            return( def->info );
+
+    return( NULL );
+}
+
+const mbedtls_cipher_info_t *mbedtls_cipher_info_from_string( const char *cipher_name )
+{
+    const mbedtls_cipher_definition_t *def;
+
+    if( NULL == cipher_name )
+        return( NULL );
+
+    for( def = mbedtls_cipher_definitions; def->info != NULL; def++ )
+        if( !  strcmp( def->info->name, cipher_name ) )
+            return( def->info );
+
+    return( NULL );
+}
+
+const mbedtls_cipher_info_t *mbedtls_cipher_info_from_values( const mbedtls_cipher_id_t cipher_id,
+                                              int key_bitlen,
+                                              const mbedtls_cipher_mode_t mode )
+{
+    const mbedtls_cipher_definition_t *def;
+
+    for( def = mbedtls_cipher_definitions; def->info != NULL; def++ )
+        if( def->info->base->cipher == cipher_id &&
+            def->info->key_bitlen == (unsigned) key_bitlen &&
+            def->info->mode == mode )
+            return( def->info );
+
+    return( NULL );
+}
+
+void mbedtls_cipher_init( mbedtls_cipher_context_t *ctx )
+{
+    memset( ctx, 0, sizeof( mbedtls_cipher_context_t ) );
+}
+
+void mbedtls_cipher_free( mbedtls_cipher_context_t *ctx )
+{
+    if( ctx == NULL )
+        return;
+
+#if defined(MBEDTLS_CMAC_C)
+    if( ctx->cmac_ctx )
+    {
+       mbedtls_platform_zeroize( ctx->cmac_ctx,
+                                 sizeof( mbedtls_cmac_context_t ) );
+       mbedtls_free( ctx->cmac_ctx );
+    }
+#endif
+
+    if( ctx->cipher_ctx )
+        ctx->cipher_info->base->ctx_free_func( ctx->cipher_ctx );
+
+    mbedtls_platform_zeroize( ctx, sizeof(mbedtls_cipher_context_t) );
+}
+
+int mbedtls_cipher_setup( mbedtls_cipher_context_t *ctx, const mbedtls_cipher_info_t *cipher_info )
+{
+    if( NULL == cipher_info || NULL == ctx )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    memset( ctx, 0, sizeof( mbedtls_cipher_context_t ) );
+
+    if( NULL == ( ctx->cipher_ctx = cipher_info->base->ctx_alloc_func() ) )
+        return( MBEDTLS_ERR_CIPHER_ALLOC_FAILED );
+
+    ctx->cipher_info = cipher_info;
+
+#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
+    /*
+     * Ignore possible errors caused by a cipher mode that doesn't use padding
+     */
+#if defined(MBEDTLS_CIPHER_PADDING_PKCS7)
+    (void) mbedtls_cipher_set_padding_mode( ctx, MBEDTLS_PADDING_PKCS7 );
+#else
+    (void) mbedtls_cipher_set_padding_mode( ctx, MBEDTLS_PADDING_NONE );
+#endif
+#endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
+
+    return( 0 );
+}
+
+int mbedtls_cipher_setkey( mbedtls_cipher_context_t *ctx, const unsigned char *key,
+        int key_bitlen, const mbedtls_operation_t operation )
+{
+    if( NULL == ctx || NULL == ctx->cipher_info )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    if( ( ctx->cipher_info->flags & MBEDTLS_CIPHER_VARIABLE_KEY_LEN ) == 0 &&
+        (int) ctx->cipher_info->key_bitlen != key_bitlen )
+    {
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+    }
+
+    ctx->key_bitlen = key_bitlen;
+    ctx->operation = operation;
+
+    /*
+     * For OFB, CFB and CTR mode always use the encryption key schedule
+     */
+    if( MBEDTLS_ENCRYPT == operation ||
+        MBEDTLS_MODE_CFB == ctx->cipher_info->mode ||
+        MBEDTLS_MODE_OFB == ctx->cipher_info->mode ||
+        MBEDTLS_MODE_CTR == ctx->cipher_info->mode )
+    {
+        return ctx->cipher_info->base->setkey_enc_func( ctx->cipher_ctx, key,
+                ctx->key_bitlen );
+    }
+
+    if( MBEDTLS_DECRYPT == operation )
+        return ctx->cipher_info->base->setkey_dec_func( ctx->cipher_ctx, key,
+                ctx->key_bitlen );
+
+    return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+}
+
+int mbedtls_cipher_set_iv( mbedtls_cipher_context_t *ctx,
+                   const unsigned char *iv, size_t iv_len )
+{
+    size_t actual_iv_size;
+
+    if( NULL == ctx || NULL == ctx->cipher_info || NULL == iv )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    /* avoid buffer overflow in ctx->iv */
+    if( iv_len > MBEDTLS_MAX_IV_LENGTH )
+        return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
+
+    if( ( ctx->cipher_info->flags & MBEDTLS_CIPHER_VARIABLE_IV_LEN ) != 0 )
+        actual_iv_size = iv_len;
+    else
+    {
+        actual_iv_size = ctx->cipher_info->iv_size;
+
+        /* avoid reading past the end of input buffer */
+        if( actual_iv_size > iv_len )
+            return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+    }
+
+#if defined(MBEDTLS_CHACHA20_C)
+    if ( ctx->cipher_info->type == MBEDTLS_CIPHER_CHACHA20 )
+    {
+        if ( 0 != mbedtls_chacha20_starts( (mbedtls_chacha20_context*)ctx->cipher_ctx,
+                                           iv,
+                                           0U ) ) /* Initial counter value */
+        {
+            return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+        }
+    }
+#endif
+
+    memcpy( ctx->iv, iv, actual_iv_size );
+    ctx->iv_size = actual_iv_size;
+
+    return( 0 );
+}
+
+int mbedtls_cipher_reset( mbedtls_cipher_context_t *ctx )
+{
+    if( NULL == ctx || NULL == ctx->cipher_info )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    ctx->unprocessed_len = 0;
+
+    return( 0 );
+}
+
+#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
+int mbedtls_cipher_update_ad( mbedtls_cipher_context_t *ctx,
+                      const unsigned char *ad, size_t ad_len )
+{
+    if( NULL == ctx || NULL == ctx->cipher_info )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+#if defined(MBEDTLS_GCM_C)
+    if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
+    {
+        return mbedtls_gcm_starts( (mbedtls_gcm_context *) ctx->cipher_ctx, ctx->operation,
+                           ctx->iv, ctx->iv_size, ad, ad_len );
+    }
+#endif
+
+#if defined(MBEDTLS_CHACHAPOLY_C)
+    if (MBEDTLS_CIPHER_CHACHA20_POLY1305 == ctx->cipher_info->type )
+    {
+        int result;
+        mbedtls_chachapoly_mode_t mode;
+
+        mode = ( ctx->operation == MBEDTLS_ENCRYPT )
+                ? MBEDTLS_CHACHAPOLY_ENCRYPT
+                : MBEDTLS_CHACHAPOLY_DECRYPT;
+
+        result = mbedtls_chachapoly_starts( (mbedtls_chachapoly_context*) ctx->cipher_ctx,
+                                                        ctx->iv,
+                                                        mode );
+        if ( result != 0 )
+            return( result );
+
+        return mbedtls_chachapoly_update_aad( (mbedtls_chachapoly_context*) ctx->cipher_ctx,
+                                                          ad, ad_len );
+    }
+#endif
+
+    return( 0 );
+}
+#endif /* MBEDTLS_GCM_C || MBEDTLS_CHACHAPOLY_C */
+
+int mbedtls_cipher_update( mbedtls_cipher_context_t *ctx, const unsigned char *input,
+                   size_t ilen, unsigned char *output, size_t *olen )
+{
+    int ret;
+    size_t block_size = 0;
+
+    if( NULL == ctx || NULL == ctx->cipher_info || NULL == olen )
+    {
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+    }
+
+    *olen = 0;
+    block_size = mbedtls_cipher_get_block_size( ctx );
+
+    if( ctx->cipher_info->mode == MBEDTLS_MODE_ECB )
+    {
+        if( ilen != block_size )
+            return( MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED );
+
+        *olen = ilen;
+
+        if( 0 != ( ret = ctx->cipher_info->base->ecb_func( ctx->cipher_ctx,
+                    ctx->operation, input, output ) ) )
+        {
+            return( ret );
+        }
+
+        return( 0 );
+    }
+
+#if defined(MBEDTLS_GCM_C)
+    if( ctx->cipher_info->mode == MBEDTLS_MODE_GCM )
+    {
+        *olen = ilen;
+        return mbedtls_gcm_update( (mbedtls_gcm_context *) ctx->cipher_ctx, ilen, input,
+                           output );
+    }
+#endif
+
+#if defined(MBEDTLS_CHACHAPOLY_C)
+    if ( ctx->cipher_info->type == MBEDTLS_CIPHER_CHACHA20_POLY1305 )
+    {
+        *olen = ilen;
+        return mbedtls_chachapoly_update( (mbedtls_chachapoly_context*) ctx->cipher_ctx,
+                                                      ilen, input, output );
+    }
+#endif
+
+    if ( 0 == block_size )
+    {
+        return MBEDTLS_ERR_CIPHER_INVALID_CONTEXT;
+    }
+
+    if( input == output &&
+       ( ctx->unprocessed_len != 0 || ilen % block_size ) )
+    {
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+    }
+
+#if defined(MBEDTLS_CIPHER_MODE_CBC)
+    if( ctx->cipher_info->mode == MBEDTLS_MODE_CBC )
+    {
+        size_t copy_len = 0;
+
+        /*
+         * If there is not enough data for a full block, cache it.
+         */
+        if( ( ctx->operation == MBEDTLS_DECRYPT && NULL != ctx->add_padding &&
+                ilen <= block_size - ctx->unprocessed_len ) ||
+            ( ctx->operation == MBEDTLS_DECRYPT && NULL == ctx->add_padding &&
+                ilen < block_size - ctx->unprocessed_len ) ||
+             ( ctx->operation == MBEDTLS_ENCRYPT &&
+                ilen < block_size - ctx->unprocessed_len ) )
+        {
+            memcpy( &( ctx->unprocessed_data[ctx->unprocessed_len] ), input,
+                    ilen );
+
+            ctx->unprocessed_len += ilen;
+            return( 0 );
+        }
+
+        /*
+         * Process cached data first
+         */
+        if( 0 != ctx->unprocessed_len )
+        {
+            copy_len = block_size - ctx->unprocessed_len;
+
+            memcpy( &( ctx->unprocessed_data[ctx->unprocessed_len] ), input,
+                    copy_len );
+
+            if( 0 != ( ret = ctx->cipher_info->base->cbc_func( ctx->cipher_ctx,
+                    ctx->operation, block_size, ctx->iv,
+                    ctx->unprocessed_data, output ) ) )
+            {
+                return( ret );
+            }
+
+            *olen += block_size;
+            output += block_size;
+            ctx->unprocessed_len = 0;
+
+            input += copy_len;
+            ilen -= copy_len;
+        }
+
+        /*
+         * Cache final, incomplete block
+         */
+        if( 0 != ilen )
+        {
+            if( 0 == block_size )
+            {
+                return MBEDTLS_ERR_CIPHER_INVALID_CONTEXT;
+            }
+
+            /* Encryption: only cache partial blocks
+             * Decryption w/ padding: always keep at least one whole block
+             * Decryption w/o padding: only cache partial blocks
+             */
+            copy_len = ilen % block_size;
+            if( copy_len == 0 &&
+                ctx->operation == MBEDTLS_DECRYPT &&
+                NULL != ctx->add_padding)
+            {
+                copy_len = block_size;
+            }
+
+            memcpy( ctx->unprocessed_data, &( input[ilen - copy_len] ),
+                    copy_len );
+
+            ctx->unprocessed_len += copy_len;
+            ilen -= copy_len;
+        }
+
+        /*
+         * Process remaining full blocks
+         */
+        if( ilen )
+        {
+            if( 0 != ( ret = ctx->cipher_info->base->cbc_func( ctx->cipher_ctx,
+                    ctx->operation, ilen, ctx->iv, input, output ) ) )
+            {
+                return( ret );
+            }
+
+            *olen += ilen;
+        }
+
+        return( 0 );
+    }
+#endif /* MBEDTLS_CIPHER_MODE_CBC */
+
+#if defined(MBEDTLS_CIPHER_MODE_CFB)
+    if( ctx->cipher_info->mode == MBEDTLS_MODE_CFB )
+    {
+        if( 0 != ( ret = ctx->cipher_info->base->cfb_func( ctx->cipher_ctx,
+                ctx->operation, ilen, &ctx->unprocessed_len, ctx->iv,
+                input, output ) ) )
+        {
+            return( ret );
+        }
+
+        *olen = ilen;
+
+        return( 0 );
+    }
+#endif /* MBEDTLS_CIPHER_MODE_CFB */
+
+#if defined(MBEDTLS_CIPHER_MODE_OFB)
+    if( ctx->cipher_info->mode == MBEDTLS_MODE_OFB )
+    {
+        if( 0 != ( ret = ctx->cipher_info->base->ofb_func( ctx->cipher_ctx,
+                ilen, &ctx->unprocessed_len, ctx->iv, input, output ) ) )
+        {
+            return( ret );
+        }
+
+        *olen = ilen;
+
+        return( 0 );
+    }
+#endif /* MBEDTLS_CIPHER_MODE_OFB */
+
+#if defined(MBEDTLS_CIPHER_MODE_CTR)
+    if( ctx->cipher_info->mode == MBEDTLS_MODE_CTR )
+    {
+        if( 0 != ( ret = ctx->cipher_info->base->ctr_func( ctx->cipher_ctx,
+                ilen, &ctx->unprocessed_len, ctx->iv,
+                ctx->unprocessed_data, input, output ) ) )
+        {
+            return( ret );
+        }
+
+        *olen = ilen;
+
+        return( 0 );
+    }
+#endif /* MBEDTLS_CIPHER_MODE_CTR */
+
+#if defined(MBEDTLS_CIPHER_MODE_XTS)
+    if( ctx->cipher_info->mode == MBEDTLS_MODE_XTS )
+    {
+        if( ctx->unprocessed_len > 0 ) {
+            /* We can only process an entire data unit at a time. */
+            return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
+        }
+
+        ret = ctx->cipher_info->base->xts_func( ctx->cipher_ctx,
+                ctx->operation, ilen, ctx->iv, input, output );
+        if( ret != 0 )
+        {
+            return( ret );
+        }
+
+        *olen = ilen;
+
+        return( 0 );
+    }
+#endif /* MBEDTLS_CIPHER_MODE_XTS */
+
+#if defined(MBEDTLS_CIPHER_MODE_STREAM)
+    if( ctx->cipher_info->mode == MBEDTLS_MODE_STREAM )
+    {
+        if( 0 != ( ret = ctx->cipher_info->base->stream_func( ctx->cipher_ctx,
+                                                    ilen, input, output ) ) )
+        {
+            return( ret );
+        }
+
+        *olen = ilen;
+
+        return( 0 );
+    }
+#endif /* MBEDTLS_CIPHER_MODE_STREAM */
+
+    return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
+}
+
+#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
+#if defined(MBEDTLS_CIPHER_PADDING_PKCS7)
+/*
+ * PKCS7 (and PKCS5) padding: fill with ll bytes, with ll = padding_len
+ */
+static void add_pkcs_padding( unsigned char *output, size_t output_len,
+        size_t data_len )
+{
+    size_t padding_len = output_len - data_len;
+    unsigned char i;
+
+    for( i = 0; i < padding_len; i++ )
+        output[data_len + i] = (unsigned char) padding_len;
+}
+
+static int get_pkcs_padding( unsigned char *input, size_t input_len,
+        size_t *data_len )
+{
+    size_t i, pad_idx;
+    unsigned char padding_len, bad = 0;
+
+    if( NULL == input || NULL == data_len )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    padding_len = input[input_len - 1];
+    *data_len = input_len - padding_len;
+
+    /* Avoid logical || since it results in a branch */
+    bad |= padding_len > input_len;
+    bad |= padding_len == 0;
+
+    /* The number of bytes checked must be independent of padding_len,
+     * so pick input_len, which is usually 8 or 16 (one block) */
+    pad_idx = input_len - padding_len;
+    for( i = 0; i < input_len; i++ )
+        bad |= ( input[i] ^ padding_len ) * ( i >= pad_idx );
+
+    return( MBEDTLS_ERR_CIPHER_INVALID_PADDING * ( bad != 0 ) );
+}
+#endif /* MBEDTLS_CIPHER_PADDING_PKCS7 */
+
+#if defined(MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS)
+/*
+ * One and zeros padding: fill with 80 00 ... 00
+ */
+static void add_one_and_zeros_padding( unsigned char *output,
+                                       size_t output_len, size_t data_len )
+{
+    size_t padding_len = output_len - data_len;
+    unsigned char i = 0;
+
+    output[data_len] = 0x80;
+    for( i = 1; i < padding_len; i++ )
+        output[data_len + i] = 0x00;
+}
+
+static int get_one_and_zeros_padding( unsigned char *input, size_t input_len,
+                                      size_t *data_len )
+{
+    size_t i;
+    unsigned char done = 0, prev_done, bad;
+
+    if( NULL == input || NULL == data_len )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    bad = 0x80;
+    *data_len = 0;
+    for( i = input_len; i > 0; i-- )
+    {
+        prev_done = done;
+        done |= ( input[i - 1] != 0 );
+        *data_len |= ( i - 1 ) * ( done != prev_done );
+        bad ^= input[i - 1] * ( done != prev_done );
+    }
+
+    return( MBEDTLS_ERR_CIPHER_INVALID_PADDING * ( bad != 0 ) );
+
+}
+#endif /* MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS */
+
+#if defined(MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN)
+/*
+ * Zeros and len padding: fill with 00 ... 00 ll, where ll is padding length
+ */
+static void add_zeros_and_len_padding( unsigned char *output,
+                                       size_t output_len, size_t data_len )
+{
+    size_t padding_len = output_len - data_len;
+    unsigned char i = 0;
+
+    for( i = 1; i < padding_len; i++ )
+        output[data_len + i - 1] = 0x00;
+    output[output_len - 1] = (unsigned char) padding_len;
+}
+
+static int get_zeros_and_len_padding( unsigned char *input, size_t input_len,
+                                      size_t *data_len )
+{
+    size_t i, pad_idx;
+    unsigned char padding_len, bad = 0;
+
+    if( NULL == input || NULL == data_len )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    padding_len = input[input_len - 1];
+    *data_len = input_len - padding_len;
+
+    /* Avoid logical || since it results in a branch */
+    bad |= padding_len > input_len;
+    bad |= padding_len == 0;
+
+    /* The number of bytes checked must be independent of padding_len */
+    pad_idx = input_len - padding_len;
+    for( i = 0; i < input_len - 1; i++ )
+        bad |= input[i] * ( i >= pad_idx );
+
+    return( MBEDTLS_ERR_CIPHER_INVALID_PADDING * ( bad != 0 ) );
+}
+#endif /* MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN */
+
+#if defined(MBEDTLS_CIPHER_PADDING_ZEROS)
+/*
+ * Zero padding: fill with 00 ... 00
+ */
+static void add_zeros_padding( unsigned char *output,
+                               size_t output_len, size_t data_len )
+{
+    size_t i;
+
+    for( i = data_len; i < output_len; i++ )
+        output[i] = 0x00;
+}
+
+static int get_zeros_padding( unsigned char *input, size_t input_len,
+                              size_t *data_len )
+{
+    size_t i;
+    unsigned char done = 0, prev_done;
+
+    if( NULL == input || NULL == data_len )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    *data_len = 0;
+    for( i = input_len; i > 0; i-- )
+    {
+        prev_done = done;
+        done |= ( input[i-1] != 0 );
+        *data_len |= i * ( done != prev_done );
+    }
+
+    return( 0 );
+}
+#endif /* MBEDTLS_CIPHER_PADDING_ZEROS */
+
+/*
+ * No padding: don't pad :)
+ *
+ * There is no add_padding function (check for NULL in mbedtls_cipher_finish)
+ * but a trivial get_padding function
+ */
+static int get_no_padding( unsigned char *input, size_t input_len,
+                              size_t *data_len )
+{
+    if( NULL == input || NULL == data_len )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    *data_len = input_len;
+
+    return( 0 );
+}
+#endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
+
+int mbedtls_cipher_finish( mbedtls_cipher_context_t *ctx,
+                   unsigned char *output, size_t *olen )
+{
+    if( NULL == ctx || NULL == ctx->cipher_info || NULL == olen )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    *olen = 0;
+
+    if( MBEDTLS_MODE_CFB == ctx->cipher_info->mode ||
+        MBEDTLS_MODE_OFB == ctx->cipher_info->mode ||
+        MBEDTLS_MODE_CTR == ctx->cipher_info->mode ||
+        MBEDTLS_MODE_GCM == ctx->cipher_info->mode ||
+        MBEDTLS_MODE_XTS == ctx->cipher_info->mode ||
+        MBEDTLS_MODE_STREAM == ctx->cipher_info->mode )
+    {
+        return( 0 );
+    }
+
+    if ( ( MBEDTLS_CIPHER_CHACHA20          == ctx->cipher_info->type ) ||
+         ( MBEDTLS_CIPHER_CHACHA20_POLY1305 == ctx->cipher_info->type ) )
+    {
+        return( 0 );
+    }
+
+    if( MBEDTLS_MODE_ECB == ctx->cipher_info->mode )
+    {
+        if( ctx->unprocessed_len != 0 )
+            return( MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED );
+
+        return( 0 );
+    }
+
+#if defined(MBEDTLS_CIPHER_MODE_CBC)
+    if( MBEDTLS_MODE_CBC == ctx->cipher_info->mode )
+    {
+        int ret = 0;
+
+        if( MBEDTLS_ENCRYPT == ctx->operation )
+        {
+            /* check for 'no padding' mode */
+            if( NULL == ctx->add_padding )
+            {
+                if( 0 != ctx->unprocessed_len )
+                    return( MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED );
+
+                return( 0 );
+            }
+
+            ctx->add_padding( ctx->unprocessed_data, mbedtls_cipher_get_iv_size( ctx ),
+                    ctx->unprocessed_len );
+        }
+        else if( mbedtls_cipher_get_block_size( ctx ) != ctx->unprocessed_len )
+        {
+            /*
+             * For decrypt operations, expect a full block,
+             * or an empty block if no padding
+             */
+            if( NULL == ctx->add_padding && 0 == ctx->unprocessed_len )
+                return( 0 );
+
+            return( MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED );
+        }
+
+        /* cipher block */
+        if( 0 != ( ret = ctx->cipher_info->base->cbc_func( ctx->cipher_ctx,
+                ctx->operation, mbedtls_cipher_get_block_size( ctx ), ctx->iv,
+                ctx->unprocessed_data, output ) ) )
+        {
+            return( ret );
+        }
+
+        /* Set output size for decryption */
+        if( MBEDTLS_DECRYPT == ctx->operation )
+            return ctx->get_padding( output, mbedtls_cipher_get_block_size( ctx ),
+                                     olen );
+
+        /* Set output size for encryption */
+        *olen = mbedtls_cipher_get_block_size( ctx );
+        return( 0 );
+    }
+#else
+    ((void) output);
+#endif /* MBEDTLS_CIPHER_MODE_CBC */
+
+    return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
+}
+
+#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
+int mbedtls_cipher_set_padding_mode( mbedtls_cipher_context_t *ctx, mbedtls_cipher_padding_t mode )
+{
+    if( NULL == ctx ||
+        MBEDTLS_MODE_CBC != ctx->cipher_info->mode )
+    {
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+    }
+
+    switch( mode )
+    {
+#if defined(MBEDTLS_CIPHER_PADDING_PKCS7)
+    case MBEDTLS_PADDING_PKCS7:
+        ctx->add_padding = add_pkcs_padding;
+        ctx->get_padding = get_pkcs_padding;
+        break;
+#endif
+#if defined(MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS)
+    case MBEDTLS_PADDING_ONE_AND_ZEROS:
+        ctx->add_padding = add_one_and_zeros_padding;
+        ctx->get_padding = get_one_and_zeros_padding;
+        break;
+#endif
+#if defined(MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN)
+    case MBEDTLS_PADDING_ZEROS_AND_LEN:
+        ctx->add_padding = add_zeros_and_len_padding;
+        ctx->get_padding = get_zeros_and_len_padding;
+        break;
+#endif
+#if defined(MBEDTLS_CIPHER_PADDING_ZEROS)
+    case MBEDTLS_PADDING_ZEROS:
+        ctx->add_padding = add_zeros_padding;
+        ctx->get_padding = get_zeros_padding;
+        break;
+#endif
+    case MBEDTLS_PADDING_NONE:
+        ctx->add_padding = NULL;
+        ctx->get_padding = get_no_padding;
+        break;
+
+    default:
+        return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
+    }
+
+    return( 0 );
+}
+#endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
+
+#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
+int mbedtls_cipher_write_tag( mbedtls_cipher_context_t *ctx,
+                      unsigned char *tag, size_t tag_len )
+{
+    if( NULL == ctx || NULL == ctx->cipher_info || NULL == tag )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+    if( MBEDTLS_ENCRYPT != ctx->operation )
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+#if defined(MBEDTLS_GCM_C)
+    if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
+        return mbedtls_gcm_finish( (mbedtls_gcm_context *) ctx->cipher_ctx, tag, tag_len );
+#endif
+
+#if defined(MBEDTLS_CHACHAPOLY_C)
+    if ( MBEDTLS_CIPHER_CHACHA20_POLY1305 == ctx->cipher_info->type )
+    {
+        /* Don't allow truncated MAC for Poly1305 */
+        if ( tag_len != 16U )
+            return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+        return mbedtls_chachapoly_finish( (mbedtls_chachapoly_context*) ctx->cipher_ctx,
+                                                      tag );
+    }
+#endif
+
+    return( 0 );
+}
+
+int mbedtls_cipher_check_tag( mbedtls_cipher_context_t *ctx,
+                      const unsigned char *tag, size_t tag_len )
+{
+    unsigned char check_tag[16];
+    int ret;
+
+    if( NULL == ctx || NULL == ctx->cipher_info ||
+        MBEDTLS_DECRYPT != ctx->operation )
+    {
+        return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+    }
+
+#if defined(MBEDTLS_GCM_C)
+    if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
+    {
+        if( tag_len > sizeof( check_tag ) )
+            return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+        if( 0 != ( ret = mbedtls_gcm_finish( (mbedtls_gcm_context *) ctx->cipher_ctx,
+                                     check_tag, tag_len ) ) )
+        {
+            return( ret );
+        }
+
+        /* Check the tag in "constant-time" */
+        if( mbedtls_constant_time_memcmp( tag, check_tag, tag_len ) != 0 )
+            return( MBEDTLS_ERR_CIPHER_AUTH_FAILED );
+
+        return( 0 );
+    }
+#endif /* MBEDTLS_GCM_C */
+
+#if defined(MBEDTLS_CHACHAPOLY_C)
+    if ( MBEDTLS_CIPHER_CHACHA20_POLY1305 == ctx->cipher_info->type )
+    {
+        /* Don't allow truncated MAC for Poly1305 */
+        if ( tag_len != sizeof( check_tag ) )
+            return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+
+        ret = mbedtls_chachapoly_finish( (mbedtls_chachapoly_context*) ctx->cipher_ctx,
+                                                     check_tag );
+        if ( ret != 0 )
+        {
+            return( ret );
+        }
+
+        /* Check the tag in "constant-time" */
+        if( mbedtls_constant_time_memcmp( tag, check_tag, tag_len ) != 0 )
+            return( MBEDTLS_ERR_CIPHER_AUTH_FAILED );
+
+        return( 0 );
+    }
+#endif /* MBEDTLS_CHACHAPOLY_C */
+
+    return( 0 );
+}
+#endif /* MBEDTLS_GCM_C || MBEDTLS_CHACHAPOLY_C */
+
+/*
+ * Packet-oriented wrapper for non-AEAD modes
+ */
+int mbedtls_cipher_crypt( mbedtls_cipher_context_t *ctx,
+                  const unsigned char *iv, size_t iv_len,
+                  const unsigned char *input, size_t ilen,
+                  unsigned char *output, size_t *olen )
+{
+    int ret;
+    size_t finish_olen;
+
+    if( ( ret = mbedtls_cipher_set_iv( ctx, iv, iv_len ) ) != 0 )
+        return( ret );
+
+    if( ( ret = mbedtls_cipher_reset( ctx ) ) != 0 )
+        return( ret );
+
+    if( ( ret = mbedtls_cipher_update( ctx, input, ilen, output, olen ) ) != 0 )
+        return( ret );
+
+    if( ( ret = mbedtls_cipher_finish( ctx, output + *olen, &finish_olen ) ) != 0 )
+        return( ret );
+
+    *olen += finish_olen;
+
+    return( 0 );
+}
+
+#if defined(MBEDTLS_CIPHER_MODE_AEAD)
+/*
+ * Packet-oriented encryption for AEAD modes
+ */
+int mbedtls_cipher_auth_encrypt( mbedtls_cipher_context_t *ctx,
+                         const unsigned char *iv, size_t iv_len,
+                         const unsigned char *ad, size_t ad_len,
+                         const unsigned char *input, size_t ilen,
+                         unsigned char *output, size_t *olen,
+                         unsigned char *tag, size_t tag_len )
+{
+#if defined(MBEDTLS_GCM_C)
+    if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
+    {
+        *olen = ilen;
+        return( mbedtls_gcm_crypt_and_tag( ctx->cipher_ctx, MBEDTLS_GCM_ENCRYPT, ilen,
+                                   iv, iv_len, ad, ad_len, input, output,
+                                   tag_len, tag ) );
+    }
+#endif /* MBEDTLS_GCM_C */
+#if defined(MBEDTLS_CCM_C)
+    if( MBEDTLS_MODE_CCM == ctx->cipher_info->mode )
+    {
+        *olen = ilen;
+        return( mbedtls_ccm_encrypt_and_tag( ctx->cipher_ctx, ilen,
+                                     iv, iv_len, ad, ad_len, input, output,
+                                     tag, tag_len ) );
+    }
+#endif /* MBEDTLS_CCM_C */
+#if defined(MBEDTLS_CHACHAPOLY_C)
+    if ( MBEDTLS_CIPHER_CHACHA20_POLY1305 == ctx->cipher_info->type )
+    {
+        /* ChachaPoly has fixed length nonce and MAC (tag) */
+        if ( ( iv_len != ctx->cipher_info->iv_size ) ||
+             ( tag_len != 16U ) )
+        {
+            return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+        }
+
+        *olen = ilen;
+        return( mbedtls_chachapoly_encrypt_and_tag( ctx->cipher_ctx,
+                                ilen, iv, ad, ad_len, input, output, tag ) );
+    }
+#endif /* MBEDTLS_CHACHAPOLY_C */
+
+    return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
+}
+
+/*
+ * Packet-oriented decryption for AEAD modes
+ */
+int mbedtls_cipher_auth_decrypt( mbedtls_cipher_context_t *ctx,
+                         const unsigned char *iv, size_t iv_len,
+                         const unsigned char *ad, size_t ad_len,
+                         const unsigned char *input, size_t ilen,
+                         unsigned char *output, size_t *olen,
+                         const unsigned char *tag, size_t tag_len )
+{
+#if defined(MBEDTLS_GCM_C)
+    if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
+    {
+        int ret;
+
+        *olen = ilen;
+        ret = mbedtls_gcm_auth_decrypt( ctx->cipher_ctx, ilen,
+                                iv, iv_len, ad, ad_len,
+                                tag, tag_len, input, output );
+
+        if( ret == MBEDTLS_ERR_GCM_AUTH_FAILED )
+            ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
+
+        return( ret );
+    }
+#endif /* MBEDTLS_GCM_C */
+#if defined(MBEDTLS_CCM_C)
+    if( MBEDTLS_MODE_CCM == ctx->cipher_info->mode )
+    {
+        int ret;
+
+        *olen = ilen;
+        ret = mbedtls_ccm_auth_decrypt( ctx->cipher_ctx, ilen,
+                                iv, iv_len, ad, ad_len,
+                                input, output, tag, tag_len );
+
+        if( ret == MBEDTLS_ERR_CCM_AUTH_FAILED )
+            ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
+
+        return( ret );
+    }
+#endif /* MBEDTLS_CCM_C */
+#if defined(MBEDTLS_CHACHAPOLY_C)
+    if ( MBEDTLS_CIPHER_CHACHA20_POLY1305 == ctx->cipher_info->type )
+    {
+        int ret;
+
+        /* ChachaPoly has fixed length nonce and MAC (tag) */
+        if ( ( iv_len != ctx->cipher_info->iv_size ) ||
+             ( tag_len != 16U ) )
+        {
+            return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
+        }
+
+        *olen = ilen;
+        ret = mbedtls_chachapoly_auth_decrypt( ctx->cipher_ctx, ilen,
+                                iv, ad, ad_len, tag, input, output );
+
+        if( ret == MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED )
+            ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
+
+        return( ret );
+    }
+#endif /* MBEDTLS_CHACHAPOLY_C */
+
+    return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
+}
+#endif /* MBEDTLS_CIPHER_MODE_AEAD */
+
+#endif /* MBEDTLS_CIPHER_C */