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ge_operations: keep sc_reduce and sc_muladd results in [0, l) #12076

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ge_operations: keep sc_reduce and sc_muladd results in [0, l) #12076

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122 changes: 122 additions & 0 deletions wolfcrypt/src/ge_operations.c
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,7 @@ void sc_reduce(byte* s)
{
sword64 t[24];
sword64 carry;
sword64 mask;
#ifdef WOLFSSL_WIDE_BYTE
int i;
#endif
Expand Down Expand Up @@ -273,6 +274,28 @@ void sc_reduce(byte* s)
carry = t[ 9] >> 21; t[10] += carry; t[ 9] &= MASK_21;
carry = t[10] >> 21; t[11] += carry; t[10] &= MASK_21;

/* Add l back when the result is negative. */
mask = t[11] >> 63;
t[ 0] += ORDER_0 & mask;
t[ 1] += ORDER_1 & mask;
t[ 2] += ORDER_2 & mask;
t[ 3] += ORDER_3 & mask;
t[ 4] += ORDER_4 & mask;
t[ 5] += ORDER_5 & mask;
t[11] += ((sword64)1 << 21) & mask;

carry = t[ 0] >> 21; t[ 1] += carry; t[ 0] &= MASK_21;
carry = t[ 1] >> 21; t[ 2] += carry; t[ 1] &= MASK_21;
carry = t[ 2] >> 21; t[ 3] += carry; t[ 2] &= MASK_21;
carry = t[ 3] >> 21; t[ 4] += carry; t[ 3] &= MASK_21;
carry = t[ 4] >> 21; t[ 5] += carry; t[ 4] &= MASK_21;
carry = t[ 5] >> 21; t[ 6] += carry; t[ 5] &= MASK_21;
carry = t[ 6] >> 21; t[ 7] += carry; t[ 6] &= MASK_21;
carry = t[ 7] >> 21; t[ 8] += carry; t[ 7] &= MASK_21;
carry = t[ 8] >> 21; t[ 9] += carry; t[ 8] &= MASK_21;
carry = t[ 9] >> 21; t[10] += carry; t[ 9] &= MASK_21;
carry = t[10] >> 21; t[11] += carry; t[10] &= MASK_21;

s[ 0] = (byte)(t[ 0] >> 0);
s[ 1] = (byte)(t[ 0] >> 8);
s[ 2] = (byte)(t[ 0] >> 16) | (byte)((byte)t[ 1] << 5);
Expand Down Expand Up @@ -327,6 +350,7 @@ void sc_muladd(byte* s, const byte* a, const byte* b, const byte* c)
word32 ad[12], bd[12], cd[12];
sword64 t[24];
sword64 carry;
sword64 mask;
#ifdef WOLFSSL_WIDE_BYTE
int i;
#endif
Expand Down Expand Up @@ -601,6 +625,28 @@ void sc_muladd(byte* s, const byte* a, const byte* b, const byte* c)
carry = t[ 9] >> 21; t[10] += carry; t[ 9] &= MASK_21;
carry = t[10] >> 21; t[11] += carry; t[10] &= MASK_21;

/* Add l back when the result is negative. */
mask = t[11] >> 63;
t[ 0] += ORDER_0 & mask;
t[ 1] += ORDER_1 & mask;
t[ 2] += ORDER_2 & mask;
t[ 3] += ORDER_3 & mask;
t[ 4] += ORDER_4 & mask;
t[ 5] += ORDER_5 & mask;
t[11] += ((sword64)1 << 21) & mask;

carry = t[ 0] >> 21; t[ 1] += carry; t[ 0] &= MASK_21;
carry = t[ 1] >> 21; t[ 2] += carry; t[ 1] &= MASK_21;
carry = t[ 2] >> 21; t[ 3] += carry; t[ 2] &= MASK_21;
carry = t[ 3] >> 21; t[ 4] += carry; t[ 3] &= MASK_21;
carry = t[ 4] >> 21; t[ 5] += carry; t[ 4] &= MASK_21;
carry = t[ 5] >> 21; t[ 6] += carry; t[ 5] &= MASK_21;
carry = t[ 6] >> 21; t[ 7] += carry; t[ 6] &= MASK_21;
carry = t[ 7] >> 21; t[ 8] += carry; t[ 7] &= MASK_21;
carry = t[ 8] >> 21; t[ 9] += carry; t[ 8] &= MASK_21;
carry = t[ 9] >> 21; t[10] += carry; t[ 9] &= MASK_21;
carry = t[10] >> 21; t[11] += carry; t[10] &= MASK_21;

s[ 0] = (byte)(t[ 0] >> 0);
s[ 1] = (byte)(t[ 0] >> 8);
s[ 2] = (byte)(t[ 0] >> 16) | (byte)((byte)t[ 1] << 5);
Expand Down Expand Up @@ -685,6 +731,7 @@ void sc_reduce(byte* s)
{
__int128_t t[12];
__int128_t carry;
__int128_t mask;

t[ 0] = MASK_42 & (load_6(s + 0) >> 0);
t[ 1] = MASK_42 & (load_6(s + 5) >> 2);
Expand Down Expand Up @@ -747,6 +794,43 @@ void sc_reduce(byte* s)
carry = t[ 3] >> 42; t[ 4] += carry; t[ 3] &= MASK_42;
carry = t[ 4] >> 42; t[ 5] += carry; t[ 4] &= MASK_42;

/* The result is in [-l, 2l). Add l back if it is negative, then
* subtract l and add it back if that makes it negative. */
mask = t[ 5] >> 127;
t[ 0] += ORDER_0 & mask;
t[ 1] += ORDER_1 & mask;
t[ 2] += ORDER_2 & mask;
t[ 5] += ((__int128_t)1 << 42) & mask;

carry = t[ 0] >> 42; t[ 1] += carry; t[ 0] &= MASK_42;
carry = t[ 1] >> 42; t[ 2] += carry; t[ 1] &= MASK_42;
carry = t[ 2] >> 42; t[ 3] += carry; t[ 2] &= MASK_42;
carry = t[ 3] >> 42; t[ 4] += carry; t[ 3] &= MASK_42;
carry = t[ 4] >> 42; t[ 5] += carry; t[ 4] &= MASK_42;

t[ 0] -= ORDER_0;
t[ 1] -= ORDER_1;
t[ 2] -= ORDER_2;
t[ 5] -= (__int128_t)1 << 42;

carry = t[ 0] >> 42; t[ 1] += carry; t[ 0] &= MASK_42;
carry = t[ 1] >> 42; t[ 2] += carry; t[ 1] &= MASK_42;
carry = t[ 2] >> 42; t[ 3] += carry; t[ 2] &= MASK_42;
carry = t[ 3] >> 42; t[ 4] += carry; t[ 3] &= MASK_42;
carry = t[ 4] >> 42; t[ 5] += carry; t[ 4] &= MASK_42;

mask = t[ 5] >> 127;
t[ 0] += ORDER_0 & mask;
t[ 1] += ORDER_1 & mask;
t[ 2] += ORDER_2 & mask;
t[ 5] += ((__int128_t)1 << 42) & mask;

carry = t[ 0] >> 42; t[ 1] += carry; t[ 0] &= MASK_42;
carry = t[ 1] >> 42; t[ 2] += carry; t[ 1] &= MASK_42;
carry = t[ 2] >> 42; t[ 3] += carry; t[ 2] &= MASK_42;
carry = t[ 3] >> 42; t[ 4] += carry; t[ 3] &= MASK_42;
carry = t[ 4] >> 42; t[ 5] += carry; t[ 4] &= MASK_42;

s[ 0] = (byte)(t[ 0] >> 0);
s[ 1] = (byte)(t[ 0] >> 8);
s[ 2] = (byte)(t[ 0] >> 16);
Expand Down Expand Up @@ -796,6 +880,7 @@ void sc_muladd(byte* s, const byte* a, const byte* b, const byte* c)
word64 ad[6], bd[6], cd[6];
__int128_t t[12];
__int128_t carry;
__int128_t mask;

ad[ 0] = MASK_42 & (load_6(a + 0) >> 0);
ad[ 1] = MASK_42 & (load_6(a + 5) >> 2);
Expand Down Expand Up @@ -899,6 +984,43 @@ void sc_muladd(byte* s, const byte* a, const byte* b, const byte* c)
carry = t[ 3] >> 42; t[ 4] += carry; t[ 3] &= MASK_42;
carry = t[ 4] >> 42; t[ 5] += carry; t[ 4] &= MASK_42;

/* The result is in [-l, 2l). Add l back if it is negative, then
* subtract l and add it back if that makes it negative. */
mask = t[ 5] >> 127;
t[ 0] += ORDER_0 & mask;
t[ 1] += ORDER_1 & mask;
t[ 2] += ORDER_2 & mask;
t[ 5] += ((__int128_t)1 << 42) & mask;

carry = t[ 0] >> 42; t[ 1] += carry; t[ 0] &= MASK_42;
carry = t[ 1] >> 42; t[ 2] += carry; t[ 1] &= MASK_42;
carry = t[ 2] >> 42; t[ 3] += carry; t[ 2] &= MASK_42;
carry = t[ 3] >> 42; t[ 4] += carry; t[ 3] &= MASK_42;
carry = t[ 4] >> 42; t[ 5] += carry; t[ 4] &= MASK_42;

t[ 0] -= ORDER_0;
t[ 1] -= ORDER_1;
t[ 2] -= ORDER_2;
t[ 5] -= (__int128_t)1 << 42;

carry = t[ 0] >> 42; t[ 1] += carry; t[ 0] &= MASK_42;
carry = t[ 1] >> 42; t[ 2] += carry; t[ 1] &= MASK_42;
carry = t[ 2] >> 42; t[ 3] += carry; t[ 2] &= MASK_42;
carry = t[ 3] >> 42; t[ 4] += carry; t[ 3] &= MASK_42;
carry = t[ 4] >> 42; t[ 5] += carry; t[ 4] &= MASK_42;

mask = t[ 5] >> 127;
t[ 0] += ORDER_0 & mask;
t[ 1] += ORDER_1 & mask;
t[ 2] += ORDER_2 & mask;
t[ 5] += ((__int128_t)1 << 42) & mask;

carry = t[ 0] >> 42; t[ 1] += carry; t[ 0] &= MASK_42;
carry = t[ 1] >> 42; t[ 2] += carry; t[ 1] &= MASK_42;
carry = t[ 2] >> 42; t[ 3] += carry; t[ 2] &= MASK_42;
carry = t[ 3] >> 42; t[ 4] += carry; t[ 3] &= MASK_42;
carry = t[ 4] >> 42; t[ 5] += carry; t[ 4] &= MASK_42;

s[ 0] = (byte)(t[ 0] >> 0);
s[ 1] = (byte)(t[ 0] >> 8);
s[ 2] = (byte)(t[ 0] >> 16);
Expand Down
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