Ensure that the port number and TXID are properly randomized.
This fix reads from /dev/urandom to get the required entropy.
Bug: 6535492
Change-Id: Ibc2fec3f71a67607b608ad9b767b0b6504993c1d
diff --git a/libc/netbsd/resolv/res_init.c b/libc/netbsd/resolv/res_init.c
index ffd4054..56a25af 100644
--- a/libc/netbsd/resolv/res_init.c
+++ b/libc/netbsd/resolv/res_init.c
@@ -99,6 +99,8 @@
#include <netdb.h>
#ifdef ANDROID_CHANGES
+#include <errno.h>
+#include <fcntl.h>
#include <sys/system_properties.h>
#endif /* ANDROID_CHANGES */
@@ -716,10 +718,44 @@
return (htonl(IN_CLASSC_NET));
}
+#ifdef ANDROID_CHANGES
+static int
+real_randomid(u_int *random_value) {
+ /* open the nonblocking random device, returning -1 on failure */
+ int random_device = open("/dev/urandom", O_RDONLY);
+ if (random_device < 0) {
+ return -1;
+ }
+
+ /* read from the random device, returning -1 on failure (or too many retries)*/
+ u_int retry = 5;
+ for (retry; retry > 0; retry--) {
+ int retval = read(random_device, random_value, sizeof(u_int));
+ if (retval == sizeof(u_int)) {
+ *random_value &= 0xffff;
+ close(random_device);
+ return 0;
+ } else if ((retval < 0) && (errno != EINTR)) {
+ break;
+ }
+ }
+
+ close(random_device);
+ return -1;
+}
+#endif /* ANDROID_CHANGES */
+
u_int
res_randomid(void) {
+#ifdef ANDROID_CHANGES
+ int status = 0;
+ u_int output = 0;
+ status = real_randomid(&output);
+ if (status != -1) {
+ return output;
+ }
+#endif /* ANDROID_CHANGES */
struct timeval now;
-
gettimeofday(&now, NULL);
return (0xffff & (now.tv_sec ^ now.tv_usec ^ getpid()));
}
