- in compat/arc4random call getentropy_urandom when getentropy fails

with ENOSYS.


git-svn-id: file:///svn/unbound/trunk@4699 be551aaa-1e26-0410-a405-d3ace91eadb9

compat/arc4random.c

@@ -71,6 +71,70 @@ static struct {
 
 static inline void _rs_rekey(u_char *dat, size_t datlen);
 
+/*
+ * Basic sanity checking; wish we could do better.
+ */
+static int
+fallback_gotdata(char *buf, size_t len)
+{
+	char	any_set = 0;
+	size_t	i;
+
+	for (i = 0; i < len; ++i)
+		any_set |= buf[i];
+	if (any_set == 0)
+		return -1;
+	return 0;
+}
+
+/* fallback for getentropy in case libc returns failure */
+static int
+fallback_getentropy_urandom(void *buf, size_t len)
+{
+	size_t i;
+	int fd, flags;
+	int save_errno = errno;
+
+start:
+
+	flags = O_RDONLY;
+#ifdef O_NOFOLLOW
+	flags |= O_NOFOLLOW;
+#endif
+#ifdef O_CLOEXEC
+	flags |= O_CLOEXEC;
+#endif
+	fd = open("/dev/urandom", flags, 0);
+	if (fd == -1) {
+		if (errno == EINTR)
+			goto start;
+		goto nodevrandom;
+	}
+#ifndef O_CLOEXEC
+	fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
+#endif
+	for (i = 0; i < len; ) {
+		size_t wanted = len - i;
+		ssize_t ret = read(fd, (char*)buf + i, wanted);
+
+		if (ret == -1) {
+			if (errno == EAGAIN || errno == EINTR)
+				continue;
+			close(fd);
+			goto nodevrandom;
+		}
+		i += ret;
+	}
+	close(fd);
+	if (fallback_gotdata(buf, len) == 0) {
+		errno = save_errno;
+		return 0;		/* satisfied */
+	}
+nodevrandom:
+	errno = EIO;
+	return -1;
+}
+
 static inline void
 _rs_init(u_char *buf, size_t n)
 {
@@ -114,12 +178,15 @@ _rs_stir(void)
 	u_char rnd[KEYSZ + IVSZ];
 
 	if (getentropy(rnd, sizeof rnd) == -1) {
+		if(errno != ENOSYS ||
+			fallback_getentropy_urandom(rnd, sizeof rnd) == -1) {
 #ifdef SIGKILL
 			raise(SIGKILL);
 #else
 			exit(9); /* windows */
 #endif
 		}
+	}
 
 	if (!rs)
 		_rs_init(rnd, sizeof(rnd));

doc/Changelog

@@ -1,3 +1,7 @@
+29 May 2018: Wouter
+	- in compat/arc4random call getentropy_urandom when getentropy fails
+	  with ENOSYS.
+
 28 May 2018: Wouter
 	- Fix windows tcp and tls spin on events.
 	- Add routine from getdns to add windows cert store to the SSL_CTX.