rnd: add gen_key_bytes to generate key from good entropy source

Make this a function and do not have this in curvetun hard coded.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>

3 files changed, 33 insertions, 19 deletions

diff --git a/curvetun.c b/curvetun.c
index 1b69b2d..ffb6314 100644
--- a/curvetun.c
+++ b/curvetun.c
@@ -257,17 +257,7 @@ static void create_keypair(char *home)
 
 	printf("Reading from %s (this may take a while) ...\n", HIG_ENTROPY_SOURCE);
 
-	fd = open_or_die(HIG_ENTROPY_SOURCE, O_RDONLY);
-
-	ret = read_exact(fd, secretkey, sizeof(secretkey), 0);
-	if (ret != sizeof(secretkey)) {
-		err = EIO;
-		errstr = "Cannot read from "HIG_ENTROPY_SOURCE"!\n";
-		goto out;
-	}
-
-	close(fd);
-
+	gen_key_bytes(secretkey, sizeof(secretkey));
 	crypto_scalarmult_curve25519_base(publickey, secretkey);
 
 	memset(path, 0, sizeof(path));
diff --git a/rnd.c b/rnd.c
index 3a7481d..7dd36a3 100644
--- a/rnd.c
+++ b/rnd.c
@@ -4,17 +4,20 @@
 #include <unistd.h>
 
 #include "rnd.h"
+#include "die.h"
+#include "ioexact.h"
+#include "ioops.h"
 
-static int fd_rnd = -1;
+static int fdw = -1;
 
-static void randombytes(unsigned char *x, unsigned long long xlen)
+static void randombytes_weak(unsigned char *x, unsigned long long xlen)
 {
 	int ret;
 
-	if (fd_rnd == -1) {
+	if (fdw == -1) {
 		for (;;) {
-			fd_rnd = open(LOW_ENTROPY_SOURCE, O_RDONLY);
-			if (fd_rnd != -1)
+			fdw = open(LOW_ENTROPY_SOURCE, O_RDONLY);
+			if (fdw != -1)
 				break;
 			sleep(1);
 		}
@@ -26,7 +29,7 @@ static void randombytes(unsigned char *x, unsigned long long xlen)
 		else
 			ret = 1048576;
 
-		ret = read(fd_rnd, x, ret);
+		ret = read(fdw, x, ret);
 		if (ret < 1) {
 			sleep(1);
 			continue;
@@ -37,9 +40,29 @@ static void randombytes(unsigned char *x, unsigned long long xlen)
 	}
 }
 
+static void randombytes_strong(unsigned char *x, unsigned long long xlen)
+{
+	int fds, ret;
+
+	fds = open_or_die(HIG_ENTROPY_SOURCE, O_RDONLY);
+
+	ret = read_exact(fds, x, xlen, 0);
+	if (ret != xlen)
+		panic("Error reading from entropy source!\n");
+
+	close(fds);
+}
+
 int secrand(void)
 {
 	int ret;
-	randombytes((void *) &ret, sizeof(ret));
+
+	randombytes_weak((void *) &ret, sizeof(ret));
+
 	return ret;
 }
+
+void gen_key_bytes(unsigned char *area, size_t len)
+{
+	randombytes_strong(area, len);
+}
diff --git a/rnd.h b/rnd.h
index dd128a1..154fccf 100644
--- a/rnd.h
+++ b/rnd.h
@@ -4,10 +4,11 @@
 #define HIG_ENTROPY_SOURCE	"/dev/random"
 #define LOW_ENTROPY_SOURCE	"/dev/urandom"
 
-/* Note: it's not really secure, but the name only suggests it's better to use
+/* secrand is not really secure, but the name only suggests it's better to use
  * than rand(3) when transferring bytes over the network in non-security
  * critical structure members. secrand() is only used to fill up salts actually.
  */
 extern int secrand(void);
+extern void gen_key_bytes(unsigned char *area, size_t len);
 
 #endif /* RND_H */