uECC_vli_mmod: Avoid potential buffer overrun #182
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The shifting copy of `mod` into `mod_multiple` would overrun the destination if the high word of `mod` was zero, so `word_shift` > `num_words`. This is not the case for any curve p or n, but this part of the code is written as if to support arbitrary `mod`, comment disclaimer notwithstanding. Issue was detected via a static analysis tool. Alternative would be to reduce the genericness and just use `vli_numDigits` on the high word to get `bit_shift`, and use `num_words` as `word_shift`.
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The shifting copy of
modintomod_multiplewould overrun the destination if the high word ofmodwas zero, soword_shift>num_words.This is not the case for any curve p or n, but this part of the code is written as if to support arbitrary
mod, comment disclaimer notwithstanding.Issue was detected via a static analysis tool.
Alternative would be to reduce the genericness and just use
vli_numDigitson the high word to getbit_shift, and usenum_wordsasword_shift.