mbedtls: fix hw accelerated big-num mul if operand and result overlap
this issue is mainly exposed when using larger (4096) client key in TLS mutual auth, since it uses multiplications > 2048 when mbedtls_mpi_mul_mpi is used in recursion, which works only if both operands point to different location than result since mpi_mult_mpi_overlong() called mbedtls_mpi_grow() to reallocate buffers used in previous pointer arithmetics and thus corrupting it. Fixed by growing the mpi buffer before calling mpi_mult_mpi_overlong()
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1 changed files with 3 additions and 5 deletions
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@ -506,6 +506,9 @@ int mbedtls_mpi_mul_mpi( mbedtls_mpi *Z, const mbedtls_mpi *X, const mbedtls_mpi
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return ret;
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return ret;
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}
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}
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/* Grow Z to result size early, avoid interim allocations */
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MBEDTLS_MPI_CHK( mbedtls_mpi_grow(Z, z_words) );
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/* If either factor is over 2048 bits, we can't use the standard hardware multiplier
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/* If either factor is over 2048 bits, we can't use the standard hardware multiplier
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(it assumes result is double longest factor, and result is max 4096 bits.)
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(it assumes result is double longest factor, and result is max 4096 bits.)
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@ -550,8 +553,6 @@ int mbedtls_mpi_mul_mpi( mbedtls_mpi *Z, const mbedtls_mpi *X, const mbedtls_mpi
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start_op(RSA_MULT_START_REG);
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start_op(RSA_MULT_START_REG);
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MBEDTLS_MPI_CHK( mbedtls_mpi_grow(Z, z_words) );
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wait_op_complete(RSA_MULT_START_REG);
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wait_op_complete(RSA_MULT_START_REG);
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/* Read back the result */
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/* Read back the result */
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@ -658,9 +659,6 @@ static int mpi_mult_mpi_overlong(mbedtls_mpi *Z, const mbedtls_mpi *X, const mbe
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};
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};
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mbedtls_mpi_init(&Ztemp);
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mbedtls_mpi_init(&Ztemp);
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/* Grow Z to result size early, avoid interim allocations */
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mbedtls_mpi_grow(Z, z_words);
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/* Get result Ztemp = Yp * X (need temporary variable Ztemp) */
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/* Get result Ztemp = Yp * X (need temporary variable Ztemp) */
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MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi(&Ztemp, X, &Yp) );
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MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi(&Ztemp, X, &Yp) );
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