[Cast Streaming] Implement sender session class

This patch adds a new SenderSession class along with unit testing for
this class.

Embedders can create an instance of this class in order to start a
streaming session with an already known receiver. The embedder is
expected to have a valid TLS connection already established with
the receiver.

Bug: b/162542753
Change-Id: Ia91df728d947e1fa20ed0b360f595f75d41bf11c
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/2378540
Reviewed-by: Jordan Bayles <jophba@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Commit-Queue: Jordan Bayles <jophba@chromium.org>

4 files changed, 99 insertions, 0 deletions

diff --git a/util/BUILD.gn b/util/BUILD.gn
index 7eaf3d30..d2f756e7 100644
--- a/util/BUILD.gn
+++ b/util/BUILD.gn
@@ -30,6 +30,8 @@ source_set("util") {
     "crypto/digest_sign.h",
     "crypto/openssl_util.cc",
     "crypto/openssl_util.h",
+    "crypto/random_bytes.cc",
+    "crypto/random_bytes.h",
     "crypto/rsa_private_key.cc",
     "crypto/rsa_private_key.h",
     "crypto/secure_hash.cc",
@@ -83,6 +85,7 @@ source_set("unittests") {
   sources = [
     "alarm_unittest.cc",
     "big_endian_unittest.cc",
+    "crypto/random_bytes_unittest.cc",
     "crypto/rsa_private_key_unittest.cc",
     "crypto/secure_hash_unittest.cc",
     "crypto/sha2_unittest.cc",
diff --git a/util/crypto/random_bytes.cc b/util/crypto/random_bytes.cc
new file mode 100644
index 00000000..c090a762
--- /dev/null
+++ b/util/crypto/random_bytes.cc
@@ -0,0 +1,25 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "util/crypto/random_bytes.h"
+
+#include "openssl/rand.h"
+#include "util/osp_logging.h"
+
+namespace openscreen {
+namespace crypto {
+
+std::array<uint8_t, 16> GenerateRandomBytes16() {
+  std::array<uint8_t, 16> result;
+  GenerateRandomBytes(result.begin(), result.size());
+  return result;
+}
+
+void GenerateRandomBytes(uint8_t* out, int len) {
+  // Working cryptography is mandatory for our library to run.
+  OSP_CHECK(RAND_bytes(out, len) == 1);
+}
+
+}  // namespace crypto
+}  // namespace openscreen
diff --git a/util/crypto/random_bytes.h b/util/crypto/random_bytes.h
new file mode 100644
index 00000000..be7381f0
--- /dev/null
+++ b/util/crypto/random_bytes.h
@@ -0,0 +1,19 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UTIL_CRYPTO_RANDOM_BYTES_H_
+#define UTIL_CRYPTO_RANDOM_BYTES_H_
+
+#include <array>
+
+namespace openscreen {
+namespace crypto {
+
+std::array<uint8_t, 16> GenerateRandomBytes16();
+void GenerateRandomBytes(uint8_t* out, int len);
+
+}  // namespace crypto
+}  // namespace openscreen
+
+#endif  // UTIL_CRYPTO_RANDOM_BYTES_H_
diff --git a/util/crypto/random_bytes_unittest.cc b/util/crypto/random_bytes_unittest.cc
new file mode 100644
index 00000000..b42e3f08
--- /dev/null
+++ b/util/crypto/random_bytes_unittest.cc
@@ -0,0 +1,52 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "util/crypto/random_bytes.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "gtest/gtest.h"
+
+namespace openscreen {
+namespace crypto {
+namespace {
+
+struct NonZero {
+  NonZero() = default;
+  bool operator()(int n) const { return n > 0; }
+};
+
+}  // namespace
+
+TEST(RandomBytesTest, CanGenerateRandomBytes) {
+  std::array<uint8_t, 4> bytes;
+  GenerateRandomBytes(bytes.begin(), bytes.size());
+
+  NonZero pred;
+  ASSERT_TRUE(std::any_of(bytes.begin(), bytes.end(), pred));
+}
+
+TEST(RandomBytesTest, CanGenerate16RandomBytes) {
+  std::array<uint8_t, 16> bytes = GenerateRandomBytes16();
+
+  NonZero pred;
+  ASSERT_TRUE(std::any_of(bytes.begin(), bytes.end(), pred));
+}
+
+TEST(RandomBytesTest, KeysAreNotIdentical) {
+  constexpr int kNumKeys = 100;
+  constexpr int kKeyLength = 100;
+  std::array<std::array<uint8_t, kKeyLength>, kNumKeys> keys;
+  for (int i = 0; i < kNumKeys; ++i) {
+    GenerateRandomBytes(keys[i].begin(), kKeyLength);
+  }
+
+  std::sort(std::begin(keys), std::end(keys));
+  ASSERT_TRUE(std::adjacent_find(std::begin(keys), std::end(keys)) ==
+              std::end(keys));
+}
+
+}  // namespace crypto
+}  // namespace openscreen