From 450dfb09ee72ffedea8f2a25fdce17295f01f62f Mon Sep 17 00:00:00 2001
From: Stephan Mueller <smueller@chronox.de>
Date: Tue, 8 Aug 2017 10:04:06 +0200
Subject: [PATCH] Unify code to read from seed sources

Remove the code duplication for FD reads and syscall reads.

This patch also fixes the use of __NR_getrandom resolution.

[Upstream commit: https://github.com/smuellerDD/libkcapi/commit/450dfb09ee72ffedea8f2a25fdce17295f01f62f]
Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>

---
 apps/kcapi-rng.c | 71 +++++++++++++++++++++++++-------------------------------
 1 file changed, 32 insertions(+), 39 deletions(-)

diff --git a/apps/kcapi-rng.c b/apps/kcapi-rng.c
index e15edf9..96da111 100644
--- a/apps/kcapi-rng.c
+++ b/apps/kcapi-rng.c
@@ -17,7 +17,9 @@
  * DAMAGE.
  */
 
+#define _GNU_SOURCE
 #include <unistd.h>
+#include <sys/syscall.h>
 #include <errno.h>
 #include <limits.h>
 #include <stdint.h>
@@ -41,56 +43,48 @@
 /* Minimum seed is 256 bits. */
 #define KCAPI_RNG_MINSEEDSIZE 32
 
-struct kcapi_handle *rng = NULL;
-unsigned int Verbosity = 0;
-char *rng_name = NULL;
+static struct kcapi_handle *rng = NULL;
+static unsigned int Verbosity = 0;
+static char *rng_name = NULL;
 
-#ifndef HAVE_GETRANDOM
-static int read_complete(int fd, uint8_t *buf, uint32_t buflen)
+#if !defined(HAVE_GETRANDOM) && !defined(__NR_getrandom)
+static int random_fd = -1;
+static int open_random(void)
 {
-	ssize_t ret;
+	random_fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC);
+	if (0 > random_fd)
+		return random_fd;
 
-	do {
-		ret = read(fd, buf, buflen);
-		if (0 < ret) {
-			buflen -= ret;
-			buf += ret;
-		}
-	} while ((0 < ret || EINTR == errno || ERESTART == errno)
-		 && buflen > 0);
-
-	if (buflen == 0)
-		return 0;
-	return 1;
+	return 0;
 }
 
-static int read_random(uint8_t *buf, uint32_t buflen)
+static void close_random(void)
 {
-	int fd;
-	int ret = 0;
-
-	fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC);
-	if (0 > fd)
-		return fd;
-
-	ret = read_complete(fd, buf, buflen);
-	close(fd);
-	return ret;
+	close(random_fd);
 }
 #endif
 
 static int get_random(uint8_t *buf, uint32_t buflen)
 {
+	ssize_t ret;
+
 	if (buflen > INT_MAX)
 		return 1;
 
+#if (!defined(HAVE_GETRANDOM) && !defined(__NR_getrandom))
+	ret = open_random();
+	if (ret)
+		return ret;
+#endif
+
+	do {
 #ifdef HAVE_GETRANDOM
-	return getrandom(buf, buflen, 0);
+		ret = getrandom(buf, buflen, 0);
+#elif defined __NR_getrandom
+		ret = syscall(__NR_getrandom, buf, buflen, 0);
 #else
-# ifdef __NR_getrandom
-	do {
-		int ret = syscall(__NR_getrandom, buf, buflen, 0);
-
+		ret = read(random_fd, buf, buflen);
+#endif
 		if (0 < ret) {
 			buflen -= ret;
 			buf += ret;
@@ -98,14 +92,13 @@ static int get_random(uint8_t *buf, uint32_t buflen)
 	} while ((0 < ret || EINTR == errno || ERESTART == errno)
 		 && buflen > 0);
 
+#if (!defined(HAVE_GETRANDOM) && !defined(__NR_getrandom))
+	close_random();
+#endif
+
 	if (buflen == 0)
 		return 0;
-
 	return 1;
-# else
-	return read_random(buf, buflen);
-# endif
-#endif
 }
 
 static void usage(void)