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List:       busybox
Subject:    [PATCH v3] getrandom: new applet
From:       Etienne CHAMPETIER <champetier.etienne () gmail ! com>
Date:       2016-06-29 15:32:15
Message-ID: 1467214335-13627-1-git-send-email-champetier.etienne () gmail ! com
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first user of this applet will be LEDE (OpenWrt) to save an urandom seed
using getrandom() (so we are sure /dev/urandom pool is initialized)

function                                             old     new   delta
getrandom_main                                         -     162    +162
.rodata                                           156181  156208     +27
applet_names                                        2536    2546     +10
applet_main                                         2936    2944      +8
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 3/0 up/down: 207/0)             Total: 207 bytes

v2: reduce size by 40 bytes thanks to Tito <farmatito@tiscali.it>
v3: release under GPLv2 or later, thanks Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

Signed-off-by: Etienne CHAMPETIER <champetier.etienne@gmail.com>
---
 include/applets.src.h  |  1 +
 util-linux/Config.src  |  8 ++++++++
 util-linux/Kbuild.src  |  1 +
 util-linux/getrandom.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 53 insertions(+)
 create mode 100644 util-linux/getrandom.c

diff --git a/include/applets.src.h b/include/applets.src.h
index 6e1b02f..b617d14 100644
--- a/include/applets.src.h
+++ b/include/applets.src.h
@@ -153,6 +153,7 @@ IF_FTPPUT(APPLET_ODDNAME(ftpput, ftpgetput, BB_DIR_USR_BIN, BB_SUID_DROP, ftpput
 IF_FUSER(APPLET(fuser, BB_DIR_USR_BIN, BB_SUID_DROP))
 IF_GETENFORCE(APPLET(getenforce, BB_DIR_USR_SBIN, BB_SUID_DROP))
 IF_GETOPT(APPLET(getopt, BB_DIR_BIN, BB_SUID_DROP))
+IF_GETRANDOM(APPLET(getrandom, BB_DIR_USR_BIN, BB_SUID_DROP))
 IF_GETSEBOOL(APPLET(getsebool, BB_DIR_USR_SBIN, BB_SUID_DROP))
 IF_HD(APPLET_NOEXEC(hd, hexdump, BB_DIR_USR_BIN, BB_SUID_DROP, hd))
 IF_HDPARM(APPLET(hdparm, BB_DIR_SBIN, BB_SUID_DROP))
diff --git a/util-linux/Config.src b/util-linux/Config.src
index 922cabd..9f47db7 100644
--- a/util-linux/Config.src
+++ b/util-linux/Config.src
@@ -304,6 +304,14 @@ config FEATURE_GETOPT_LONG
 	help
 	  Enable support for long options (option -l).
 
+config GETRANDOM
+	bool "getrandom"
+	default y
+	select PLATFORM_LINUX
+	help
+	  The getrandom utility get NBYTES random bytes using getrandom()
+	  syscall (available since Linux 3.17)
+
 config HEXDUMP
 	bool "hexdump"
 	default y
diff --git a/util-linux/Kbuild.src b/util-linux/Kbuild.src
index 0b87c52..b164fb7 100644
--- a/util-linux/Kbuild.src
+++ b/util-linux/Kbuild.src
@@ -19,6 +19,7 @@ lib-$(CONFIG_FLOCK)             += flock.o
 lib-$(CONFIG_FREERAMDISK)       += freeramdisk.o
 lib-$(CONFIG_FSCK_MINIX)        += fsck_minix.o
 lib-$(CONFIG_GETOPT)            += getopt.o
+lib-$(CONFIG_GETRANDOM)         += getrandom.o
 lib-$(CONFIG_HEXDUMP)           += hexdump.o
 lib-$(CONFIG_HWCLOCK)           += hwclock.o
 lib-$(CONFIG_IPCRM)             += ipcrm.o
diff --git a/util-linux/getrandom.c b/util-linux/getrandom.c
new file mode 100644
index 0000000..d61b53a
--- /dev/null
+++ b/util-linux/getrandom.c
@@ -0,0 +1,43 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * getrandom.c - read random bytes using getrandom() syscall
+ *
+ * Copyright (C) 2016 Etienne Champetier <champetier.etienne@gmail.com>
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+
+//usage:#define getrandom_trivial_usage
+//usage:       "N"
+//usage:#define getrandom_full_usage "\n\n"
+//usage:       "Read N random bytes using getrandom()"
+
+#include <sys/syscall.h>
+#include "libbb.h"
+
+int getrandom_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int getrandom_main(int argc, char **argv)
+{
+	int nbytes, len;
+	char buf[256]; /* getrandom(2) calls up to 256 bytes always succeed */
+
+	if (argc != 2)
+		bb_show_usage();
+
+	if (isatty(STDOUT_FILENO))
+		bb_error_msg_and_die("isatty");
+
+	nbytes = xatoi_range(argv[1], 1, INT_MAX);
+
+	for (len = sizeof(buf); nbytes > 0; nbytes -= sizeof(buf)) {
+		if (nbytes < sizeof(buf)) {
+			len = nbytes;
+		}
+		if (syscall(SYS_getrandom, buf, len, 0) != len) {
+			bb_perror_msg_and_die("getrandom");
+		}
+		xwrite(STDOUT_FILENO, buf, len);
+	}
+
+	return EXIT_SUCCESS;
+}
-- 
2.5.5

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