unikernel/duniverse/mirage-crypto/rng/unix/mc_getrandom_stubs.c

@@ -0,0 +1,87 @@
+#ifndef _MSC_VER
+# include <unistd.h>
+#endif
+
+#include "mirage_crypto.h"
+
+#include <caml/mlvalues.h>
+#include <caml/memory.h>
+#include <caml/unixsupport.h>
+#include <caml/bigarray.h>
+
+#if defined(__ANDROID_API__) && __ANDROID_API__ < 28
+// on Android 27 and earlier, we use Google's <sys/random.h> recommended arc4random_buf
+# include <stdlib.h>
+
+void raw_getrandom (uint8_t *data, size_t len) {
+  arc4random_buf(data, len);
+}
+#elif defined(__linux) || defined(__GNU__)
+# include <errno.h>
+// on Linux and GNU/Hurd, we use getrandom and loop
+
+# if __GLIBC__ && __GLIBC__ <= 2 && __GLIBC_MINOR__ < 25
+# include <sys/syscall.h>
+# define getrandom(buf, len, flags) syscall(SYS_getrandom, (buf), (len), (flags))
+# else
+# include <sys/random.h>
+# define getrandom(buf, len, flags) getrandom((buf), (len), (flags))
+# endif
+
+void raw_getrandom (uint8_t *data, size_t len) {
+  size_t off = 0;
+  ssize_t r = 0;
+  while (off < len) {
+    r = getrandom(data + off, len - off, 0);
+    if (r == -1) {
+      if (errno == EINTR) continue;
+      else uerror("getrandom", Nothing);
+    }
+    off += (size_t)r;
+  }
+}
+#elif (defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)  || defined(__OpenBSD__) || defined(__APPLE__)) || defined(__NetBSD__)
+// on BSD and macOS, loop (in pieces of 256) getentropy
+#if defined(__APPLE__)
+// on macOS, getentropy is defined in sys/random.h (on BSD in unistd.h)
+#include <sys/random.h>
+#endif
+#include <sys/param.h>
+
+void raw_getrandom (uint8_t *data, size_t len) {
+  size_t rlen = 0;
+  for (size_t i = 0; i <= len; i += 256) {
+    rlen = MIN(256, len - i);
+    if (getentropy(data + i, rlen) == -1) uerror("getentropy", Nothing);
+  }
+}
+#elif (defined(_WIN32))
+/* There is a choice between using RtlGenRandom and BCryptGenRandom
+ * here, and Microsoft does not make the choice obvious. It appears
+ * that RtlGenRandom is best used when older Windows compatibility
+ * is of concern, but requires some gymnastics around binding it
+ * with the right calling convention.
+ *
+ * Therefore (https://github.com/mirage/mirage-crypto/pull/39) we
+ * have decided to go with the more modern Windows API with bcrypt,
+ * and make Windows 10 our minimum supported version of mirage-crypto.
+ */
+#include <windows.h>
+#include <ntstatus.h>
+#include <bcrypt.h>
+
+void raw_getrandom(uint8_t *data, size_t len) {
+   NTSTATUS Status;
+   Status = BCryptGenRandom(NULL, data, len, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
+   if (Status != STATUS_SUCCESS)
+     uerror("BCryptGenRandom", Nothing);
+}
+
+#else
+#error "Retrieving random data not supported on this platform"
+#endif
+
+CAMLprim value mc_getrandom (value buf, value off, value len) {
+  raw_getrandom(_bp_uint8_off(buf, off), Long_val(len));
+  return Val_unit;
+}