From:   Tedd Ho-Jeong An <hj.tedd.an@gmail.com>
To:     linux-bluetooth@vger.kernel.org
Subject: [BlueZ V2 PATCH 3/5] tools/btgatt-server: Replace random number generation function
Date:   Wed,  8 Dec 2021 14:39:21 -0800
Message-Id: <20211208223923.519664-4-hj.tedd.an@gmail.com>
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From: Tedd Ho-Jeong An <tedd.an@intel.com>

This patch replaces the rand() function to the getrandom() syscall.

It was reported by the Coverity scan
  rand() should not be used for security-related applications, because
  linear congruential algorithms are too easy to break
---
 tools/btgatt-server.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/btgatt-server.c b/tools/btgatt-server.c
index 000145a3d..15d49a464 100644
--- a/tools/btgatt-server.c
+++ b/tools/btgatt-server.c
@@ -20,6 +20,7 @@
 #include <getopt.h>
 #include <unistd.h>
 #include <errno.h>
+#include <sys/random.h>
 
 #include "lib/bluetooth.h"
 #include "lib/hci.h"
@@ -284,9 +285,13 @@ static bool hr_msrmt_cb(void *user_data)
 	uint16_t len = 2;
 	uint8_t pdu[4];
 	uint32_t cur_ee;
+	uint32_t val;
+
+	if (getrandom(&val, sizeof(val), 0) < 0)
+		return false;
 
 	pdu[0] = 0x06;
-	pdu[1] = 90 + (rand() % 40);
+	pdu[1] = 90 + (val % 40);
 
 	if (expended_present) {
 		pdu[0] |= 0x08;
-- 
2.25.1