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fix bug in get_one_and_zeros_padding()

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add test case (“0000000082”) which fails with the old implementation.
This commit is contained in:
Micha Kraus 2017-12-23 23:40:08 +01:00
parent 312391f810
commit ba8316f790
2 changed files with 7 additions and 3 deletions
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4
library/cipher.c
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@ -516,14 +516,14 @@ static int get_one_and_zeros_padding( unsigned char *input, size_t input_len,
if( NULL == input || NULL == data_len )
return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
bad = 0xFF;
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] ^ 0x80 ) | ( done == prev_done );
bad ^= input[i - 1] * ( done != prev_done );
}
return( MBEDTLS_ERR_CIPHER_INVALID_PADDING * ( bad != 0 ) );

4
tests/suites/test_suite_cipher.padding.data
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@ -184,6 +184,10 @@ Check one and zeros padding #7 (overlong)
depends_on:MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS
check_padding:MBEDTLS_PADDING_ONE_AND_ZEROS:"0000000000":MBEDTLS_ERR_CIPHER_INVALID_PADDING:4
Check one and zeros padding #8 (last byte 0x80 | x)
depends_on:MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS
check_padding:MBEDTLS_PADDING_ONE_AND_ZEROS:"0000000082":MBEDTLS_ERR_CIPHER_INVALID_PADDING:4
Check zeros and len padding #1 (correct)
depends_on:MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN
check_padding:MBEDTLS_PADDING_ZEROS_AND_LEN:"DABBAD0001":0:4