[compiler-rt] r329633 - GetRandom / OpenBSD, using getentropy to get high quality randomness

[Vitaly Buka via llvm-commits]

Author: vitalybuka
Date: Mon Apr  9 15:46:40 2018
New Revision: 329633

URL: http://llvm.org/viewvc/llvm-project?rev=329633&view=rev
Log:
GetRandom / OpenBSD, using getentropy to get high quality randomness

Summary:
- getentropy presence since late 2014, safe to use.
- guarantees to delivers good random data up to 256 bytes.
- fall back to /dev/urandom as long the buffer is correct.

Patch by David CARLIER

Reviewers: kubamracek, vitalybuka

Reviewed By: vitalybuka

Subscribers: cryptoad, llvm-commits, #sanitizers

Differential Revision: https://reviews.llvm.org/D44866

Modified:
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc?rev=329633&r1=329632&r2=329633&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_linux.cc Mon Apr  9 15:46:40 2018
@@ -140,6 +140,9 @@ extern void internal_sigreturn();
 }
 #endif
 
+// Note : FreeBSD had implemented both
+// Linux and OpenBSD apis, available from
+// future 12.x version most likely
 #if SANITIZER_LINUX && defined(__NR_getrandom)
 # if !defined(GRND_NONBLOCK)
 #  define GRND_NONBLOCK 1
@@ -149,6 +152,12 @@ extern void internal_sigreturn();
 # define SANITIZER_USE_GETRANDOM 0
 #endif  // SANITIZER_LINUX && defined(__NR_getrandom)
 
+#if SANITIZER_OPENBSD
+# define SANITIZER_USE_GETENTROPY 1
+#else
+# define SANITIZER_USE_GETENTROPY 0
+#endif // SANITIZER_USE_GETENTROPY
+
 namespace __sanitizer {
 
 #if SANITIZER_LINUX && defined(__x86_64__)
@@ -1906,6 +1915,15 @@ uptr FindAvailableMemoryRange(uptr size,
 bool GetRandom(void *buffer, uptr length, bool blocking) {
   if (!buffer || !length || length > 256)
     return false;
+#if SANITIZER_USE_GETENTROPY
+  uptr rnd = getentropy(buffer, length);
+  int rverrno = 0;
+  if (internal_iserror(rnd, &rverrno) && rverrno == EFAULT)
+    return false;
+  else if (rnd == 0)
+    return true;
+#endif // SANITIZER_USE_GETENTROPY
+
 #if SANITIZER_USE_GETRANDOM
   static atomic_uint8_t skip_getrandom_syscall;
   if (!atomic_load_relaxed(&skip_getrandom_syscall)) {
@@ -1918,7 +1936,7 @@ bool GetRandom(void *buffer, uptr length
     else if (res == length)
       return true;
   }
-#endif  // SANITIZER_USE_GETRANDOM
+#endif // SANITIZER_USE_GETRANDOM
   // Up to 256 bytes, a read off /dev/urandom will not be interrupted.
   // blocking is moot here, O_NONBLOCK has no effect when opening /dev/urandom.
   uptr fd = internal_open("/dev/urandom", O_RDONLY);