Close connections that fail to authenticate after a while.

Like ScrambleSuit, a random interval between 1x and 5x of additional
data from the peer is read and immediately discarded before closing.

Additionally, obfs4 will close off invalid connections anywhere between
0 and 60 seconds after it determines that the incoming connection will
never complete the handshake successfully.

1 files changed, 48 insertions, 0 deletions

diff --git a/utils.go b/utils.go
new file mode 100644
index 0000000..ae7bc41
--- /dev/null
+++ b/utils.go
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2014, Yawning Angel <yawning at torproject dot org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  * Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ *  * Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package obfs4
+
+import (
+	"crypto/rand"
+	"fmt"
+	"math/big"
+)
+
+func randRange(min, max int64) (int64, error) {
+	if max < min {
+		panic(fmt.Sprintf("randRange: min > max (%d, %d)", min, max))
+	}
+
+	r := (max + 1) - min
+	ret, err := rand.Int(rand.Reader, big.NewInt(r))
+	if err != nil {
+		return 0, err
+	}
+
+	return ret.Int64() + min, nil
+}