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Replace the RC4-based PRNG with one based on ChaCha20. 3x faster.

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FossilOrigin-Name: 084d8776fa95c75440530028171c56547a341c9a952ba2f29bb533b538603c78
This commit is contained in:
drh
2022-08-16 00:04:40 +00:00
parent 207cb6f670
commit 9113c87ef3
3 changed files with 63 additions and 39 deletions
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83
src/random.c
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@@ -22,16 +22,38 @@
** This structure is the current state of the generator.
*/
static SQLITE_WSD struct sqlite3PrngType {
unsigned char isInit; /* True if initialized */
unsigned char i, j; /* State variables */
unsigned char s[256]; /* State variables */
u32 s[16]; /* 64 bytes of chacha20 state */
u8 out[64]; /* Output bytes */
u8 n; /* Output bytes remaining */
} sqlite3Prng;
#define ROTL(a,b) (((a) << (b)) | ((a) >> (32 - (b))))
#define QR(a, b, c, d) ( \
a += b, d ^= a, d = ROTL(d,16), \
c += d, b ^= c, b = ROTL(b,12), \
a += b, d ^= a, d = ROTL(d, 8), \
c += d, b ^= c, b = ROTL(b, 7))
static void chacha_block(u32 *out, const u32 *in){
int i;
u32 x[16];
memcpy(x, in, 64);
for(i=0; i<10; i++){
QR(x[0], x[4], x[ 8], x[12]);
QR(x[1], x[5], x[ 9], x[13]);
QR(x[2], x[6], x[10], x[14]);
QR(x[3], x[7], x[11], x[15]);
QR(x[0], x[5], x[10], x[15]);
QR(x[1], x[6], x[11], x[12]);
QR(x[2], x[7], x[ 8], x[13]);
QR(x[3], x[4], x[ 9], x[14]);
}
for(i=0; i<16; i++) out[i] = x[i]+in[i];
}
/*
** Return N random bytes.
*/
void sqlite3_randomness(int N, void *pBuf){
unsigned char t;
unsigned char *zBuf = pBuf;
/* The "wsdPrng" macro will resolve to the pseudo-random number generator
@@ -61,7 +83,7 @@ void sqlite3_randomness(int N, void *pBuf){
sqlite3_mutex_enter(mutex);
if( N<=0 || pBuf==0 ){
wsdPrng.isInit = 0;
wsdPrng.s[0] = 0;
sqlite3_mutex_leave(mutex);
return;
}
@@ -75,39 +97,38 @@ void sqlite3_randomness(int N, void *pBuf){
** encryption. The RC4 algorithm is being used as a PRNG (pseudo-random
** number generator) not as an encryption device.
*/
if( !wsdPrng.isInit ){
if( wsdPrng.s[0]==0 ){
sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
int i;
char k[256];
wsdPrng.j = 0;
wsdPrng.i = 0;
static const u32 chacha20_init[] = {
0x61707865, 0x3320646e, 0x79622d32, 0x6b206574
};
memcpy(&wsdPrng.s[0], chacha20_init, 16);
if( NEVER(pVfs==0) ){
memset(k, 0, sizeof(k));
memset(&wsdPrng.s[4], 0, 44);
}else{
sqlite3OsRandomness(pVfs, 256, k);
sqlite3OsRandomness(pVfs, 44, (char*)&wsdPrng.s[4]);
}
for(i=0; i<256; i++){
wsdPrng.s[i] = (u8)i;
}
for(i=0; i<256; i++){
wsdPrng.j += wsdPrng.s[i] + k[i];
t = wsdPrng.s[wsdPrng.j];
wsdPrng.s[wsdPrng.j] = wsdPrng.s[i];
wsdPrng.s[i] = t;
}
wsdPrng.isInit = 1;
wsdPrng.s[16] = wsdPrng.s[12];
wsdPrng.s[12] = 0;
wsdPrng.n = 0;
}
assert( N>0 );
do{
wsdPrng.i++;
t = wsdPrng.s[wsdPrng.i];
wsdPrng.j += t;
wsdPrng.s[wsdPrng.i] = wsdPrng.s[wsdPrng.j];
wsdPrng.s[wsdPrng.j] = t;
t += wsdPrng.s[wsdPrng.i];
*(zBuf++) = wsdPrng.s[t];
}while( --N );
while( 1 /* exit by break */ ){
if( N<=wsdPrng.n ){
memcpy(zBuf, &wsdPrng.out[wsdPrng.n-N], N);
wsdPrng.n -= N;
break;
}
if( wsdPrng.n>0 ){
memcpy(zBuf, wsdPrng.out, wsdPrng.n);
N -= wsdPrng.n;
zBuf += wsdPrng.n;
}
wsdPrng.s[12]++;
chacha_block((u32*)wsdPrng.out, wsdPrng.s);
wsdPrng.n = 64;
}
sqlite3_mutex_leave(mutex);
}