Improve retrieving entropy on Apple platforms

- replace call to SecRandomCopyBytes() by call to CCRandomGenerateBytes() (see #207)
- remove dependency on the Security framework

Author: utelle

Makefile.am

@@ -40,9 +40,9 @@ else
 AM_CFLAGS += -DSQLIT3MC_USE_MINIZ=1
 endif
 
-if HOST_OSX
-AM_LDFLAGS += -framework Security
-endif
+#if HOST_OSX
+#AM_LDFLAGS += -framework Security
+#endif
 
 LDADD = lib@[email protected]
 
@@ -159,8 +159,8 @@ else
 # use it only in the "else" branch.
 sqlite3shell_LDFLAGS += -no-install
 
-if HOST_OSX
-sqlite3shell_LDFLAGS += -framework Security
-endif
+#if HOST_OSX
+#sqlite3shell_LDFLAGS += -framework Security
+#endif
 
 endif

src/chacha20poly1305.c

@@ -383,42 +383,13 @@ static size_t read_urandom(void* buf, size_t n)
 }
 
 #if defined(__APPLE__)
-#include <AvailabilityMacros.h>
-#include <TargetConditionals.h>
-
-/* Define version macros if needed */
-#ifndef MAC_OS_X_VERSION_MIN_REQUIRED
-#define MAC_OS_X_VERSION_MIN_REQUIRED 0
-#endif
-#ifndef __IPHONE_OS_VERSION_MIN_REQUIRED
-#define __IPHONE_OS_VERSION_MIN_REQUIRED 0
-#endif
-#ifndef __TV_OS_VERSION_MIN_REQUIRED
-#define __TV_OS_VERSION_MIN_REQUIRED 0
-#endif
-#ifndef __WATCH_OS_VERSION_MIN_REQUIRED
-#define __WATCH_OS_VERSION_MIN_REQUIRED 0
-#endif
-
-#define CAN_USE_SECRANDOM() ( \
-    (TARGET_OS_OSX && MAC_OS_X_VERSION_MIN_REQUIRED >= 1070) || \
-    (TARGET_OS_IOS && __IPHONE_OS_VERSION_MIN_REQUIRED >= 80000) || \
-    (TARGET_OS_TV && __TV_OS_VERSION_MIN_REQUIRED >= 90000) || \
-    (TARGET_OS_WATCH && __WATCH_OS_VERSION_MIN_REQUIRED >= 20000) \
-  )
-
-#if CAN_USE_SECRANDOM()
-#include <Security/SecRandom.h>
-#endif
-
-#else /* !__APPLE__ */
-#define CAN_USE_SECRANDOM() 0
+#include <CommonCrypto/CommonRandom.h>
 #endif
 
 static size_t entropy(void* buf, size_t n)
 {
-#if defined(__APPLE__) && CAN_USE_SECRANDOM()
-  if (SecRandomCopyBytes(kSecRandomDefault, n, (uint8_t*) buf) == 0)
+#if defined(__APPLE__)
+  if (CCRandomGenerateBytes(buf, n) == kCCSuccess)
     return n;
 #elif defined(__linux__) && defined(SYS_getrandom)
   if (syscall(SYS_getrandom, buf, n, 0) == n)