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mpi_lt_mpi_ct: fix condition handling

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The code previously only set the done flag if the return value was one.
This led to overriding the correct return value later on.
This commit is contained in:
Janos Follath 2019-11-05 12:24:52 +00:00 committed by Simon Butcher
parent 47b56a159e
commit e9db2aa5b4
1 changed files with 8 additions and 9 deletions
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17
library/bignum.c
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@ -1147,26 +1147,25 @@ int mbedtls_mpi_lt_mpi_ct( const mbedtls_mpi *X, const mbedtls_mpi *Y,
for( i = X->n; i > 0; i-- ) for( i = X->n; i > 0; i-- )
{ {
/* /*
* If Y->p[i - 1] < X->p[i - 1] and both X and Y are negative, then * If Y->p[i - 1] < X->p[i - 1] then X < Y is true if and only if both
* X < Y. * X and Y are negative.
* *
* Again even if we can make a decision, we just mark the result and * Again even if we can make a decision, we just mark the result and
* the fact that we are done and continue looping. * the fact that we are done and continue looping.
*/ */
cond = ct_lt_mpi_uint( Y->p[i - 1], X->p[i - 1] ) & X_is_negative; cond = ct_lt_mpi_uint( Y->p[i - 1], X->p[i - 1] );
*ret |= cond & ( 1 - done ); *ret |= cond & ( 1 - done ) & X_is_negative;
done |= cond; done |= cond;
/* /*
* If X->p[i - 1] < Y->p[i - 1] and both X and Y are positive, then * If X->p[i - 1] < Y->p[i - 1] then X < Y is true if and only if both
* X < Y. * X and Y are positive.
* *
* Again even if we can make a decision, we just mark the result and * Again even if we can make a decision, we just mark the result and
* the fact that we are done and continue looping. * the fact that we are done and continue looping.
*/ */
cond = ct_lt_mpi_uint( X->p[i - 1], Y->p[i - 1] ) cond = ct_lt_mpi_uint( X->p[i - 1], Y->p[i - 1] );
& ( 1 - X_is_negative ); *ret |= cond & ( 1 - done ) & ( 1 - X_is_negative );
*ret |= cond & ( 1 - done );
done |= cond; done |= cond;
} }