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Add zeros-and-length (ANSI X.923) padding

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Manuel Pégourié-Gonnard
2013-07-26 14:55:18 +02:00
committed by Paul Bakker
parent 679f9e90ad
commit 8d4291b52a
7 changed files with 302 additions and 0 deletions
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43
library/cipher.c
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@ -594,6 +594,42 @@ static int get_one_and_zeros_padding( unsigned char *input, size_t input_len,
return 0;
}
/*
* 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 )
{
unsigned int i, padding_len = 0;
if( NULL == input || NULL == data_len )
return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
padding_len = input[input_len - 1];
if( padding_len > input_len || padding_len == 0 )
return POLARSSL_ERR_CIPHER_INVALID_PADDING;
for( i = input_len - padding_len; i < input_len - 1; i++ )
if( input[i] != 0x00 )
return POLARSSL_ERR_CIPHER_INVALID_PADDING;
*data_len = input_len - padding_len;
return 0;
}
int cipher_finish( cipher_context_t *ctx, unsigned char *output, size_t *olen)
{
int ret = 0;
@ -666,6 +702,13 @@ int cipher_set_padding_mode( cipher_context_t *ctx, cipher_padding_t mode )
return 0;
}
if( POLARSSL_PADDING_ZEROS_AND_LEN == mode )
{
ctx->add_padding = add_zeros_and_len_padding;
ctx->get_padding = get_zeros_and_len_padding;
return 0;
}
return POLARSSL_ERR_CIPHER_BAD_INPUT_DATA;
}