change the path to the random number generator during build time (see PR #11)

Signed-off-by: Toni Uhlig <matzeton@googlemail.com>

4 files changed, 48 insertions, 16 deletions

diff --git a/configure.ac b/configure.ac
index 6cecd6f..6625560 100644
--- a/configure.ac
+++ b/configure.ac
@@ -134,6 +134,21 @@ case ${selinux_enabled} in
 	*) AC_MSG_ERROR([Unknown option \`${selinux_enabled}\` for --disable-selinux]) ;;
 esac
 
+dnl `--with-randomdev`: Default value /dev/random
+use_customrng=no
+AC_MSG_CHECKING([for random device])
+AC_ARG_WITH([rngdev],
+	[AS_HELP_STRING([--with-rngdev], [Set an alternative random device. (default: /dev/random)])],
+	[use_customrng=yes], [with_rngdev="/dev/random"])
+case ${with_rngdev} in
+	/dev/random) ;;
+	/dev/urandom) ;;
+	*) AC_MSG_ERROR([Unknown random device \`${with_rngdev}\` for --with-rngdev: Only \`/dev/random\` xor \`/dev/urandom\` allowed. This option is unused on Windows targets.]) ;;
+esac
+AC_MSG_RESULT([${with_rngdev}])
+AC_DEFINE_UNQUOTED([RNGDEV], ["${with_rngdev}"],
+	[set the path to the random device you want to use for pt_random])
+
 dnl Check libcap headers/functions.
 if test x"${pcap_enabled}" != x -a \
         x"${use_msw}" != xyes; then
@@ -146,11 +161,10 @@ if test x"${pcap_enabled}" != x -a \
 fi
 
 dnl Check for more secure randomization functions
-AC_CHECK_HEADERS([bsd/stdlib.h],, [random_enabled=yes])
-AC_SEARCH_LIBS([arc4random], [bsd],,,)
-AC_CHECK_FUNCS([arc4random], [random_enabled=],)
-if test x"${random_enabled}" = x; then
-	arc4random_enabled=yes
+if test x"${use_customrng}" != xyes; then
+	AC_CHECK_HEADERS([bsd/stdlib.h],,)
+	AC_SEARCH_LIBS([arc4random], [bsd],,,)
+	AC_CHECK_FUNCS([arc4random], [arc4random_enabled=yes],)
 fi
 
 dnl Check for SELINUX
@@ -187,8 +201,8 @@ AM_CONDITIONAL([HAVE_PCAP], [test x"${pcap_enabled}" = xyes])
 AM_CONDITIONAL([HAVE_SELINUX], [test x"${selinux_enabled}" = xyes])
 AM_CONDITIONAL([IS_WINDOWS], [test x"${use_msw}" = xyes])
 AM_CONDITIONAL([HAVE_ICMPFILTER], [test x"${with_icmp_filter}" = xyes])
-AM_CONDITIONAL([HAVE_RANDOM], [test x"${random_enabled}" = xyes])
 AM_CONDITIONAL([HAVE_ARC4RANDOM], [test x"${arc4random_enabled}" = xyes])
+AM_CONDITIONAL([USE_CUSTOMRNG], [test x"${use_customrng}" = xyes])
 
 dnl output config headers
 AC_CONFIG_HEADERS([src/config.h:src/config.h.in])
diff --git a/src/Makefile.am b/src/Makefile.am
index 1d161a2..8d4787a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -20,10 +20,10 @@ endif
 
 if HAVE_ARC4RANDOM
 ptunnel_ng_CFLAGS += -DHAVE_ARC4RANDOM=1
-else
-if HAVE_RANDOM
-ptunnel_ng_CFLAGS += -DHAVE_RANDOM=1
 endif
+
+if USE_CUSTOMRNG
+ptunnel_ng_CFLAGS += -DUSE_CUSTOMRNG=1
 endif
 
 ptunnel_ng_SOURCES = \
diff --git a/src/ptunnel.c b/src/ptunnel.c
index 4463077..01e0ef5 100644
--- a/src/ptunnel.c
+++ b/src/ptunnel.c
@@ -136,6 +136,9 @@ int main(int argc, char *argv[]) {
 	if (parse_options(argc, argv))
 		return -1;
 
+	/* Init ptunnel RNG */
+	pt_random();
+
 #ifdef HAVE_PCAP
 	if (opts.pcap && opts.udp) {
 		pt_log(kLog_error, "Packet capture is not supported (or needed) when using UDP for transport.\n");
diff --git a/src/utils.c b/src/utils.c
index 6188543..a65f947 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -53,12 +53,12 @@
 #include <stdarg.h>
 #include <string.h>
 #include <time.h>
-#include <assert.h>
 #ifdef HAVE_BSD_STDLIB_H
 #include <bsd/stdlib.h>
 #endif
 
 #ifndef WIN32
+#include <errno.h>
 #include <syslog.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -97,7 +97,7 @@ void pt_log(int level, const char *fmt, ...) {
 		}
 		else
 #endif /* !WIN32 */
-			fprintf(opts.log_file, "%s", header[level]), vfprintf(opts.log_file, fmt, args);
+		fprintf(opts.log_file, "%s", header[level]), vfprintf(opts.log_file, fmt, args);
 		va_end(args);
 #ifndef WIN32
 		if (opts.log_file != stdout && !opts.use_syslog)
@@ -160,13 +160,28 @@ int pt_random(void) {
 #ifdef HAVE_ARC4RANDOM
 	return arc4random();
 #else
-#if defined(HAVE_RANDOM) && !defined(_WIN32)
+#if defined(USE_CUSTOMRNG) && !defined(_WIN32)
 	static int rng_fd = -1;
+	ssize_t bytes_read;
 	int rnd_val;
-	if (rng_fd < 0)
-		rng_fd = open("/dev/random", O_RDONLY);
-	assert(rng_fd >= 0);
-	assert( read(rng_fd, &rnd_val, sizeof rnd_val) == sizeof rnd_val );
+	if (rng_fd < 0) {
+		rng_fd = open(RNGDEV, O_RDONLY);
+		if (rng_fd < 0) {
+			pt_log(kLog_error, "FATAL: Could not open random device '%s': %s\n",
+			       RNGDEV, strerror(errno));
+			exit(EXIT_FAILURE);
+		}
+	}
+	bytes_read = read(rng_fd, &rnd_val, sizeof rnd_val);
+	if (bytes_read != sizeof rnd_val) {
+		if (bytes_read < 0)
+			pt_log(kLog_error, "FATAL: Read from random device failed: %s\n",
+			       strerror(errno));
+		else
+			pt_log(kLog_error, "FATAL: Read only %zd bytes (wanted %zd bytes)\n",
+			       bytes_read, sizeof rnd_val);
+		exit(EXIT_FAILURE);
+	}
 	return rnd_val;
 #else
 	srand(time(0));