32ec5f170
Denys Vlasenko
2018-12-08
Subject
tls: AES-GCM: in GMULT, avoid memcpy, use one less variable in bit loop
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networking/tls_aesgcm.c+11 -11
| @@ -97,25 +97,25 @@ static void RIGHTSHIFTX(byte* x) | |
| #undef l | |
| } | |
| + | // Caller guarantees X is aligned |
| static void GMULT(byte* X, byte* Y) | |
| { | |
| byte Z[AES_BLOCK_SIZE] ALIGNED_long; | |
| - | byte V[AES_BLOCK_SIZE] ALIGNED_long; |
| - | int i, j; |
| + | //byte V[AES_BLOCK_SIZE] ALIGNED_long; |
| + | int i; |
| XMEMSET(Z, 0, AES_BLOCK_SIZE); | |
| - | XMEMCPY(V, X, AES_BLOCK_SIZE); |
| - | for (i = 0; i < AES_BLOCK_SIZE; i++) |
| - | { |
| - | byte y = Y[i]; |
| - | for (j = 0; j < 8; j++) |
| - | { |
| + | //XMEMCPY(V, X, AES_BLOCK_SIZE); |
| + | for (i = 0; i < AES_BLOCK_SIZE; i++) { |
| + | uint32_t y = 0x800000 | Y[i]; |
| + | for (;;) { // for every bit in Y[i], from msb to lsb |
| if (y & 0x80) { | |
| - | xorbuf_aligned_AES_BLOCK_SIZE(Z, V); |
| + | xorbuf_aligned_AES_BLOCK_SIZE(Z, X); // was V, not X |
| } | |
| - | |
| - | RIGHTSHIFTX(V); |
| + | RIGHTSHIFTX(X); // was V, not X |
| y = y << 1; | |
| + | if ((int32_t)y < 0) // if bit 0x80000000 set = if 8 iterations done |
| + | break; |
| } | |
| } | |
| XMEMCPY(X, Z, AES_BLOCK_SIZE); | |