Look up availability of getentropy() at runtime.
This will actually support most OSs, and at least adds support for
Solaris and OSX
Fixes: #6403
Reviewed-by: Andy Polyakov <appro@openssl.org>
GH: #6405
diff --git a/crypto/rand/rand_unix.c b/crypto/rand/rand_unix.c
index bde4ac1..0c8e0dc 100644
--- a/crypto/rand/rand_unix.c
+++ b/crypto/rand/rand_unix.c
@@ -15,6 +15,7 @@
#include "rand_lcl.h"
#include "internal/rand_int.h"
#include <stdio.h>
+#include "internal/dso.h"
#if defined(__linux)
# include <sys/syscall.h>
#endif
@@ -242,10 +243,33 @@
*/
int syscall_random(void *buf, size_t buflen)
{
+ union {
+ void *p;
+ int (*f)(void *buffer, size_t length);
+ } p_getentropy;
+
+ /*
+ * Do runtime detection to find getentropy().
+ *
+ * We could cache the result of the lookup, but we normally don't
+ * call this function often.
+ *
+ * Known OSs that should support this:
+ * - Darwin since 16 (OSX 10.12, IOS 10.0).
+ * - Solaris since 11.3
+ * - OpenBSD since 5.6
+ * - Linux since 3.17 with glibc 2.25
+ * - FreeBSD since 12.0 (1200061)
+ */
+ p_getentropy.p = DSO_global_lookup("getentropy");
+ if (p_getentropy.p != NULL)
+ return p_getentropy.f(buf, buflen);
+
# if defined(OPENSSL_HAVE_GETRANDOM)
return (int)getrandom(buf, buflen, 0);
# endif
+ /* Linux supports this since version 3.17 */
# if defined(__linux) && defined(SYS_getrandom)
return (int)syscall(SYS_getrandom, buf, buflen, 0);
# endif
@@ -254,11 +278,6 @@
return (int)sysctl_random(buf, buflen);
# endif
- /* Supported since OpenBSD 5.6 */
-# if defined(__OpenBSD__) && OpenBSD >= 201411
- return getentropy(buf, buflen);
-# endif
-
return -1;
}
