1 files changed, 70 insertions, 0 deletions
diff --git a/dnsstub/dns_random.c b/dnsstub/dns_random.c
new file mode 100644
index 0000000..200cd6c
--- /dev/null
+++ b/dnsstub/dns_random.c
@@ -0,0 +1,70 @@
+#include <unistd.h>
+#include "taia.h"
+#include "uint_t.h"
+#include "dnsresolv.h"
+
+/**
+	@file dns_random.c
+	@author djb
+	@source ucspi-tcp
+	@brief random use of DNS resolvers given their IP
+*/
+
+static uint32 seed[32];
+static uint32 in[12];
+static uint32 out[8];
+static int outleft = 0;
+
+#define ROTATE(x,b) (((x) << (b)) | ((x) >> (32 - (b))))
+#define MUSH(i,b) x = t[i] += (((x ^ seed[i]) + sum) ^ ROTATE(x,b));
+
+static void surf(void)
+{
+  uint32 t[12]; uint32 x; uint32 sum = 0;
+  int r; int i; int loop;
+
+  for (i = 0; i < 12; ++i) t[i] = in[i] ^ seed[12 + i];
+  for (i = 0; i < 8; ++i) out[i] = seed[24 + i];
+  x = t[11];
+  for (loop = 0; loop < 2; ++loop) {
+    for (r = 0; r < 16; ++r) {
+      sum += 0x9e3779b9;
+      MUSH(0,5) MUSH(1,7) MUSH(2,9) MUSH(3,13)
+      MUSH(4,5) MUSH(5,7) MUSH(6,9) MUSH(7,13)
+      MUSH(8,5) MUSH(9,7) MUSH(10,9) MUSH(11,13)
+    }
+    for (i = 0; i < 8; ++i) out[i] ^= t[i + 4];
+  }
+}
+
+void dns_random_init(const char data[128])
+{
+  int i;
+  struct taia t;
+  char tpack[16];
+
+  for (i = 0; i < 32; ++i)
+    uint32_unpack((char *)data + 4 * i,seed + i);
+
+  taia_now(&t);
+  taia_pack(tpack,&t);
+  for (i = 0; i < 4; ++i)
+    uint32_unpack(tpack + 4 * i,in + 4 + i);
+
+  in[8] = getpid();
+  in[9] = getppid();
+  /* more space in 10 and 11, but this is probably enough */
+}
+
+unsigned int dns_random(unsigned int n)
+{
+  if (!n) return 0;
+
+  if (!outleft) {
+    if (!++in[0]) if (!++in[1]) if (!++in[2]) ++in[3];
+    surf();
+    outleft = 8;
+  }
+
+  return out[--outleft] % n;
+}