Crypto: Implement fast insecure RNG for overwritting memory areas.

This is mainly done to test for uninitlalized memory and find bugs
faster. Therefore it does not need to be cryptographically secure or
perfectly uniform. Xoshiro256++ seems like a good fit.

1 files changed, 18 insertions, 1 deletions

diff --git a/kernel/random.c b/kernel/random.c
index c043cdf..329b7d6 100644
--- a/kernel/random.c
+++ b/kernel/random.c
@@ -1,6 +1,7 @@
 // FIXME: This is mostlikely incredibly inefficent and insecure.
 #include <crypto/ChaCha20/chacha20.h>
 #include <crypto/SHA1/sha1.h>
+#include <crypto/xoshiro256plusplus/xoshiro256plusplus.h>
 #include <fs/devfs.h>
 #include <fs/vfs.h>
 #include <random.h>
@@ -40,7 +41,23 @@ void mix_chacha(void) {
   internal_chacha_block[COUNT] = 0;
 }
 
-void get_random(BYTEPTR buffer, u64 len) {
+void get_fast_insecure_random(u8 *buffer, u64 len) {
+  static u8 is_fast_random_seeded = 0;
+  if (!is_fast_random_seeded) {
+    uint64_t seed[4];
+    get_random((u8 *)&seed, sizeof(seed));
+    seed_xoshiro_256_pp(seed);
+    is_fast_random_seeded = 1;
+  }
+  for (; len >= 8; len -= 8, buffer += 8) {
+    *((uint64_t *)buffer) = xoshiro_256_pp();
+  }
+  for (; len > 0; len--, buffer++) {
+    *((uint8_t *)buffer) = xoshiro_256_pp() & 0xFF;
+  }
+}
+
+void get_random(u8* buffer, u64 len) {
   u8 rand_data[BLOCK_SIZE];
   for (; len > 0;) {
     if (COUNT_MAX - 1 == internal_chacha_block[COUNT]) {