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Heap Math exptmod: fixes for valid modulus checks #6599

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Merged
JacobBarthelmeh merged 1 commit into from
Jul 12, 2023
Merged

Heap Math exptmod: fixes for valid modulus checks #6599

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10 changes: 6 additions & 4 deletions wolfcrypt/src/integer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -955,7 +955,7 @@ int wolfcrypt_mp_exptmod (mp_int * G, mp_int * X, mp_int * P, mp_int * Y)
}

#ifdef BN_MP_EXPTMOD_BASE_2
if (G->used == 1 && G->dp[0] == 2) {
if (G->used == 1 && G->dp[0] == 2 && mp_isodd(P) == MP_YES) {
return mp_exptmod_base_2(X, P, Y);
}
#endif
Expand Down Expand Up @@ -985,7 +985,7 @@ int wolfcrypt_mp_exptmod (mp_int * G, mp_int * X, mp_int * P, mp_int * Y)
}
#endif

/* if the modulus is odd or dr != 0 use the montgomery method */
/* if the modulus is odd use the montgomery method, or use other known */
#ifdef BN_MP_EXPTMOD_FAST_C
if (mp_isodd (P) == MP_YES || dr != 0) {
return mp_exptmod_fast (G, X, P, Y, dr);
Expand Down Expand Up @@ -1985,7 +1985,6 @@ int mp_dr_is_modulus(mp_int *a)
return 1;
}


/* computes Y == G**X mod P, HAC pp.616, Algorithm 14.85
*
* Uses a left-to-right k-ary sliding window to compute the modular
Expand Down Expand Up @@ -2113,7 +2112,10 @@ int mp_exptmod_fast (mp_int * G, mp_int * X, mp_int * P, mp_int * Y,
if ((err = mp_reduce_2k_setup(P, &mp)) != MP_OKAY) {
goto LBL_M;
}
redux = mp_reduce_2k;
/* mp of zero is not usable */
if (mp != 0) {
redux = mp_reduce_2k;
}
#endif
}

Expand Down