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https://github.com/Mbed-TLS/mbedtls.git
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use CT interface in add_zeros_and_len_padding()
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
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6b7e2a5809
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@ -935,7 +935,8 @@ static int get_zeros_and_len_padding(unsigned char *input, size_t input_len,
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size_t *data_len)
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{
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size_t i, pad_idx;
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unsigned char padding_len, bad = 0;
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unsigned char padding_len;
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mbedtls_ct_condition_t bad;
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if (NULL == input || NULL == data_len) {
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return MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA;
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@ -945,16 +946,18 @@ static int get_zeros_and_len_padding(unsigned char *input, size_t input_len,
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*data_len = input_len - padding_len;
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/* Avoid logical || since it results in a branch */
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bad |= padding_len > input_len;
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bad |= padding_len == 0;
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bad = mbedtls_ct_uint_gt(padding_len, input_len);
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bad = mbedtls_ct_bool_or(bad, mbedtls_ct_uint_eq(padding_len, 0));
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/* The number of bytes checked must be independent of padding_len */
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pad_idx = input_len - padding_len;
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for (i = 0; i < input_len - 1; i++) {
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bad |= input[i] * (i >= pad_idx);
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mbedtls_ct_condition_t is_padding = mbedtls_ct_uint_ge(i, pad_idx);
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mbedtls_ct_condition_t nonzero_pad_byte = mbedtls_ct_uint_if_else_0(is_padding, mbedtls_ct_bool(input[i]));
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bad = mbedtls_ct_bool_or(bad, nonzero_pad_byte);
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}
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return MBEDTLS_ERR_CIPHER_INVALID_PADDING * (bad != 0);
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return -((int) mbedtls_ct_uint_if_else_0(bad, -MBEDTLS_ERR_CIPHER_INVALID_PADDING));
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}
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#endif /* MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN */
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