fall back to /dev/urandom if /dev/random is out of entropy Bug 138 by rireland

--- dropbear-0.45/options.h

+++ dropbear-0.45/options.h

@@ -148,6 +148,10 @@

 /* prngd must be manually set up to produce output */

 /*#define DROPBEAR_PRNGD_SOCKET "/var/run/dropbear-rng"*/

+/* If the normal random source would block for a while, fall back to 

+ * the urandom source so that connections don't hang forever. */

+#define DROPBEAR_URANDOM_DEV "/dev/urandom"

+

 /* Specify the number of clients we will allow to be connected but

  * not yet authenticated. After this limit, connections are rejected */

 #ifndef MAX_UNAUTH_CLIENTS

--- dropbear-0.45/random.c

+++ dropbear-0.45/random.c

@@ -57,9 +57,14 @@

 	struct sockaddr_un egdsock;

 	char egdcmd[2];

 #endif

+	mode_t readmode = O_RDONLY;

+#ifdef DROPBEAR_URANDOM_DEV

+	unsigned int readtries = 0;

+	readmode |= O_NONBLOCK;

+#endif

 #ifdef DROPBEAR_RANDOM_DEV

-	readfd = open(DROPBEAR_RANDOM_DEV, O_RDONLY);

+	readfd = open(DROPBEAR_RANDOM_DEV, readmode);

 	if (readfd < 0) {

 		dropbear_exit("couldn't open random device");

 	}

@@ -97,6 +102,24 @@

 			if (readlen < 0 && errno == EINTR) {

 				continue;

 			}

+#ifdef DROPBEAR_URANDOM_DEV

+			/* if the main random source blocked, lets retry a few times, 

+			 * but then give up and try a constant random source. */

+			if (readlen < 0 && errno == EAGAIN) {

+				++readtries;

+				if (readtries < 5) {

+					sleep(1);

+					continue;

+				} else if (readtries == 5) {

+					close (readfd);

+					readfd = open(DROPBEAR_URANDOM_DEV, readmode);

+					if (readfd < 0) {

+						dropbear_exit("couldn't open secondary random device");

+					}

+					continue;

+				}

+			}

+#endif

 			dropbear_exit("error reading random source");

 		}

 		readpos += readlen;

# dropbear_sshd

#

#############################################################

DROPBEAR_SSHD_SOURCE:=dropbear-0.46.tar.bz2

DROPBEAR_SSHD_VER:=0.46

DROPBEAR_SSHD_SOURCE:=dropbear-$(DROPBEAR_SSHD_VER).tar.bz2

DROPBEAR_SSHD_SITE:=http://matt.ucc.asn.au/dropbear/releases/

DROPBEAR_SSHD_DIR:=$(BUILD_DIR)/dropbear-0.46

DROPBEAR_SSHD_DIR:=$(BUILD_DIR)/dropbear-$(DROPBEAR_SSHD_VER)

DROPBEAR_SSHD_CAT:=bzcat

DROPBEAR_SSHD_BINARY:=dropbearmulti

DROPBEAR_SSHD_TARGET_BINARY:=usr/sbin/dropbear