1 files changed, 157 insertions, 0 deletions
diff --git a/src/random.c b/src/random.c
new file mode 100644
index 0000000..ea8431b
--- /dev/null
+++ b/src/random.c
@@ -0,0 +1,157 @@
+/*
+** 2001 September 15
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains code to implement a pseudo-random number
+** generator (PRNG) for SQLite.
+**
+** Random numbers are used by some of the database backends in order
+** to generate random integer keys for tables or random filenames.
+*/
+#include "sqliteInt.h"
+
+
+/* All threads share a single random number generator.
+** This structure is the current state of the generator.
+*/
+static SQLITE_WSD struct sqlite3PrngType {
+  u32 s[16];                 /* 64 bytes of chacha20 state */
+  u8 out[64];                /* Output bytes */
+  u8 n;                      /* Output bytes remaining */
+} sqlite3Prng;
+
+
+/* The RFC-7539 ChaCha20 block function
+*/
+#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 *zBuf = pBuf;
+
+  /* The "wsdPrng" macro will resolve to the pseudo-random number generator
+  ** state vector.  If writable static data is unsupported on the target,
+  ** we have to locate the state vector at run-time.  In the more common
+  ** case where writable static data is supported, wsdPrng can refer directly
+  ** to the "sqlite3Prng" state vector declared above.
+  */
+#ifdef SQLITE_OMIT_WSD
+  struct sqlite3PrngType *p = &GLOBAL(struct sqlite3PrngType, sqlite3Prng);
+# define wsdPrng p[0]
+#else
+# define wsdPrng sqlite3Prng
+#endif
+
+#if SQLITE_THREADSAFE
+  sqlite3_mutex *mutex;
+#endif
+
+#ifndef SQLITE_OMIT_AUTOINIT
+  if( sqlite3_initialize() ) return;
+#endif
+
+#if SQLITE_THREADSAFE
+  mutex = sqlite3MutexAlloc(SQLITE_MUTEX_STATIC_PRNG);
+#endif
+
+  sqlite3_mutex_enter(mutex);
+  if( N<=0 || pBuf==0 ){
+    wsdPrng.s[0] = 0;
+    sqlite3_mutex_leave(mutex);
+    return;
+  }
+
+  /* Initialize the state of the random number generator once,
+  ** the first time this routine is called.
+  */
+  if( wsdPrng.s[0]==0 ){
+    sqlite3_vfs *pVfs = sqlite3_vfs_find(0);
+    static const u32 chacha20_init[] = {
+      0x61707865, 0x3320646e, 0x79622d32, 0x6b206574
+    };
+    memcpy(&wsdPrng.s[0], chacha20_init, 16);
+    if( NEVER(pVfs==0) ){
+      memset(&wsdPrng.s[4], 0, 44);
+    }else{
+      sqlite3OsRandomness(pVfs, 44, (char*)&wsdPrng.s[4]);
+    }
+    wsdPrng.s[15] = wsdPrng.s[12];
+    wsdPrng.s[12] = 0;
+    wsdPrng.n = 0;
+  }
+
+  assert( N>0 );
+  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);
+}
+
+#ifndef SQLITE_UNTESTABLE
+/*
+** For testing purposes, we sometimes want to preserve the state of
+** PRNG and restore the PRNG to its saved state at a later time, or
+** to reset the PRNG to its initial state.  These routines accomplish
+** those tasks.
+**
+** The sqlite3_test_control() interface calls these routines to
+** control the PRNG.
+*/
+static SQLITE_WSD struct sqlite3PrngType sqlite3SavedPrng;
+void sqlite3PrngSaveState(void){
+  memcpy(
+    &GLOBAL(struct sqlite3PrngType, sqlite3SavedPrng),
+    &GLOBAL(struct sqlite3PrngType, sqlite3Prng),
+    sizeof(sqlite3Prng)
+  );
+}
+void sqlite3PrngRestoreState(void){
+  memcpy(
+    &GLOBAL(struct sqlite3PrngType, sqlite3Prng),
+    &GLOBAL(struct sqlite3PrngType, sqlite3SavedPrng),
+    sizeof(sqlite3Prng)
+  );
+}
+#endif /* SQLITE_UNTESTABLE */