b35eef538
Denys Vlasenko
2021-04-28
Subject
tls: code shrink in curve 25519
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networking/tls_fe.c+27 -19
| @@ -108,26 +108,26 @@ static void raw_try_sub(byte *x, const byte *p) | |
| #if 0 //UNUSED | |
| static int prime_msb(const byte *p) | |
| { | |
| - | int i; |
| - | byte x; |
| - | int shift = 1; |
| - | int z = F25519_SIZE - 1; |
| - | |
| - | /* |
| - | Test for any hot bits. |
| - | As soon as one instance is encountered set shift to 0. |
| - | */ |
| + | int i; |
| + | byte x; |
| + | int shift = 1; |
| + | int z = F25519_SIZE - 1; |
| + | |
| + | /* |
| + | Test for any hot bits. |
| + | As soon as one instance is encountered set shift to 0. |
| + | */ |
| for (i = F25519_SIZE - 1; i >= 0; i--) { | |
| - | shift &= ((shift ^ ((-p[i] | p[i]) >> 7)) & 1); |
| - | z -= shift; |
| - | } |
| + | shift &= ((shift ^ ((-p[i] | p[i]) >> 7)) & 1); |
| + | z -= shift; |
| + | } |
| x = p[z]; | |
| z <<= 3; | |
| - | shift = 1; |
| - | for (i = 0; i < 8; i++) { |
| - | shift &= ((-(x >> i) | (x >> i)) >> (7 - i) & 1); |
| - | z += shift; |
| - | } |
| + | shift = 1; |
| + | for (i = 0; i < 8; i++) { |
| + | shift &= ((-(x >> i) | (x >> i)) >> (7 - i) & 1); |
| + | z += shift; |
| + | } |
| return z - 1; | |
| } | |
| @@ -549,6 +549,9 @@ static void curve25519(byte *result, const byte *e, const byte *q) | |
| int i; | |
| struct { | |
| + | /* for bbox's special case of q == NULL meaning "use basepoint" */ |
| + | /*static const*/ uint8_t basepoint9[CURVE25519_KEYSIZE]; // = {9}; |
| + | |
| /* from wolfssl-3.15.3/wolfssl/wolfcrypt/fe_operations.h */ | |
| /*static const*/ byte f25519_one[F25519_SIZE]; // = {1}; | |
| @@ -559,6 +562,7 @@ static void curve25519(byte *result, const byte *e, const byte *q) | |
| byte xm1[F25519_SIZE]; // = {1}; | |
| byte zm1[F25519_SIZE]; // = {0}; | |
| } z; | |
| + | #define basepoint9 z.basepoint9 |
| #define f25519_one z.f25519_one | |
| #define xm z.xm | |
| #define zm z.zm | |
| @@ -569,6 +573,11 @@ static void curve25519(byte *result, const byte *e, const byte *q) | |
| zm[0] = 1; | |
| xm1[0] = 1; | |
| + | if (!q) { |
| + | basepoint9[0] = 9; |
| + | q = basepoint9; |
| + | } |
| + | |
| /* Note: bit 254 is assumed to be 1 */ | |
| lm_copy(xm, q); | |
| @@ -606,7 +615,6 @@ void FAST_FUNC curve_x25519_compute_pubkey_and_premaster( | |
| uint8_t *pubkey, uint8_t *premaster, | |
| const uint8_t *peerkey32) | |
| { | |
| - | static const uint8_t basepoint9[CURVE25519_KEYSIZE] ALIGN8 = {9}; |
| uint8_t privkey[CURVE25519_KEYSIZE]; //[32] | |
| /* Generate random private key, see RFC 7748 */ | |
| @@ -615,7 +623,7 @@ void FAST_FUNC curve_x25519_compute_pubkey_and_premaster( | |
| privkey[CURVE25519_KEYSIZE-1] = ((privkey[CURVE25519_KEYSIZE-1] & 0x7f) | 0x40); | |
| /* Compute public key */ | |
| - | curve25519(pubkey, privkey, basepoint9); |
| + | curve25519(pubkey, privkey, NULL /* "use base point of x25519" */); |
| /* Compute premaster using peer's public key */ | |
| curve25519(premaster, privkey, peerkey32); | |