From:   Tedd Ho-Jeong An <hj.tedd.an@gmail.com>
To:     linux-bluetooth@vger.kernel.org
Subject: [BlueZ V2 PATCH 4/5] plugins: Replace random number generation function
Date:   Wed,  8 Dec 2021 14:39:22 -0800
Message-Id: <20211208223923.519664-5-hj.tedd.an@gmail.com>
In-Reply-To: <20211208223923.519664-1-hj.tedd.an@gmail.com>
References: <20211208223923.519664-1-hj.tedd.an@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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
---
 plugins/autopair.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/plugins/autopair.c b/plugins/autopair.c
index 665a4f4a6..a75ecebe4 100644
--- a/plugins/autopair.c
+++ b/plugins/autopair.c
@@ -17,6 +17,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
+#include <sys/random.h>
 
 #include <glib.h>
 
@@ -49,6 +50,7 @@ static ssize_t autopair_pincb(struct btd_adapter *adapter,
 	char pinstr[7];
 	char name[25];
 	uint32_t class;
+	uint32_t val;
 
 	ba2str(device_get_address(device), addr);
 
@@ -129,8 +131,12 @@ static ssize_t autopair_pincb(struct btd_adapter *adapter,
 			if (attempt >= 4)
 				return 0;
 
+			if (getrandom(&val, sizeof(val), 0) < 0) {
+				error("Failed to get a random pincode");
+				return 0;
+			}
 			snprintf(pinstr, sizeof(pinstr), "%06u",
-						rand() % 1000000);
+						val % 1000000);
 			*display = true;
 			memcpy(pinbuf, pinstr, 6);
 			return 6;
-- 
2.25.1