Provide a function for fetching random values, either by reading
/dev/urandom or using libc. The caller is responsible for seeding
the libc random function prior to use, should a fallback to libc
function take place.
---
gdhcp/common.c | 41 ++++++++++++++++++++++++++++++++++++++++-
gdhcp/gdhcp.h | 4 ++++
2 files changed, 44 insertions(+), 1 deletion(-)
diff --git a/gdhcp/common.c b/gdhcp/common.c
index 45278a8..4a7270b 100644
--- a/gdhcp/common.c
+++ b/gdhcp/common.c
@@ -35,6 +35,7 @@
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include <arpa/inet.h>
+#include <fcntl.h>
#include "gdhcp.h"
#include "common.h"
@@ -58,6 +59,42 @@ static const DHCPOption client_options[] = {
{ OPTION_UNKNOWN, 0x00 },
};
+#define URANDOM "/dev/urandom"
+static int random_fd = -1;
+
+int dhcp_get_random(uint64_t *val)
+{
+ int r;
+
+ if (random_fd < 0) {
+ random_fd = open(URANDOM, O_RDONLY);
+ if (random_fd < 0) {
+ r = -errno;
+ *val = random();
+
+ return r;
+ }
+ }
+
+ if (read(random_fd, &val, sizeof(*val)) < 0) {
+ r = -errno;
+ *val = random();
+
+ return r;
+ }
+
+ return 0;
+}
+
+void dhcp_cleanup_random(void)
+{
+ if (random_fd < 0)
+ return;
+
+ close(random_fd);
+ random_fd = -1;
+}
+
GDHCPOptionType dhcp_get_code_type(uint8_t code)
{
int i;
@@ -356,12 +393,14 @@ void dhcp_init_header(struct dhcp_packet *packet, char
type)
void dhcpv6_init_header(struct dhcpv6_packet *packet, uint8_t type)
{
int id;
+ uint64_t rand;
memset(packet, 0, sizeof(*packet));
packet->message = type;
- id = random();
+ dhcp_get_random(&rand);
+ id = rand;
packet->transaction_id[0] = (id >> 16) & 0xff;
packet->transaction_id[1] = (id >> 8) & 0xff;
diff --git a/gdhcp/gdhcp.h b/gdhcp/gdhcp.h
index f3e47bf..ac24454 100644
--- a/gdhcp/gdhcp.h
+++ b/gdhcp/gdhcp.h
@@ -223,6 +223,10 @@ void g_dhcp_server_set_lease_time(GDHCPServer *dhcp_server,
unsigned int lease_time);
void g_dhcp_server_set_save_lease(GDHCPServer *dhcp_server,
GDHCPSaveLeaseFunc func, gpointer user_data);
+
+int dhcp_get_random(uint64_t *val);
+void dhcp_cleanup_random(void);
+
#ifdef __cplusplus
}
#endif
--
2.1.1
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