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Merge branch 'fix/mpi_incorrect_assert' into 'master'

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fix(mbedtls): Fix incorrect assert for H/W MPI operations

Closes WIFI-5591 and IDFGH-10615

See merge request espressif/esp-idf!24737
This commit is contained in:
Aditya Patwardhan
2023-07-14 08:59:10 +08:00
parent 304870dea0 20a3fcae48
commit 56f15ab017
2 changed files with 20 additions and 4 deletions
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17
components/mbedtls/port/bignum/esp_bignum.c
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@@ -632,12 +632,23 @@ static int mpi_mult_mpi_failover_mod_mult( mbedtls_mpi *Z, const mbedtls_mpi *X,
Z->MBEDTLS_PRIVATE(s) = X->MBEDTLS_PRIVATE(s) * Y->MBEDTLS_PRIVATE(s);
/*
* If this condition fails then most likely hardware peripheral
* Relevant: https://github.com/espressif/esp-idf/issues/11850
* If the first condition fails then most likely hardware peripheral
* has produced an incorrect result for MPI operation. This can
* happen if data fed to the peripheral register was incorrect.
* Relevant: https://github.com/espressif/esp-idf/issues/8710#issuecomment-1249178698
*
* z_words is calculated as the worst-case possible size of the result
* MPI Z. The difference between z_words and the actual words taken by
* the MPI result (mpi_words(Z)) can be a maximum of 1 word.
* The value z_bits (actual bits taken by the MPI result) is calculated
* as x_bits + y_bits bits, however, in some cases, z_bits can be
* x_bits + y_bits - 1 bits (see example below).
* 0b1111 * 0b1111 = 0b11100001 -> 8 bits
* 0b1000 * 0b1000 = 0b01000000 -> 7 bits.
* The code rounds up to the nearest word size, so the maximum difference
* could be of only 1 word. The second condition handles this.
*/
assert(mpi_words(Z) == z_words);
assert((z_words >= mpi_words(Z)) && (z_words - mpi_words(Z) <= (size_t)1));
cleanup:
esp_mpi_disable_hardware_hw_op();
return ret;