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Use CT interface in get_one_and_zeros_padding

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-09-19 14:37:50 +01:00
parent 6cec41c3bb
commit 89a9bd5887
1 changed files with 15 additions and 11 deletions
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26
library/cipher.c
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@ -894,24 +894,28 @@ static void add_one_and_zeros_padding(unsigned char *output,
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;
mbedtls_ct_condition_t in_padding = MBEDTLS_CT_TRUE;
mbedtls_ct_condition_t bad = MBEDTLS_CT_TRUE;
*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);
for (int i = input_len - 1; i >= 0; i--) {
mbedtls_ct_condition_t is_nonzero = mbedtls_ct_bool(input[i]);
mbedtls_ct_condition_t hit_first_nonzero = mbedtls_ct_bool_and(is_nonzero, in_padding);
*data_len = mbedtls_ct_size_if(hit_first_nonzero, i, *data_len);
bad = mbedtls_ct_uint_if(hit_first_nonzero, mbedtls_ct_uint_ne(input[i], 0x80), bad);
in_padding = mbedtls_ct_bool_and(in_padding, mbedtls_ct_bool_not(is_nonzero));
}
return MBEDTLS_ERR_CIPHER_INVALID_PADDING * (bad != 0);
return -((int) mbedtls_ct_uint_if_else_0(bad, -MBEDTLS_ERR_CIPHER_INVALID_PADDING));
}
#endif /* MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS */