Implement Cast Streaming mirroring, DLNA casting, daemon+GUI, and breadd integration

Builds out the full v1 scope: a vendored+patched openscreen subset for
low-latency Cast Streaming (Mirroring receiver 0F5096E8) alongside the
existing Cast V2/HLS and new DLNA/AVTransport casting paths, breadcastd's
Idle/Casting state machine with a private IPC socket, the breadcast GTK4
popup as a thin IPC client, and bread.cast.*/bread.command.cast.* breadd
integration (device discovery, start/stop, mirroring lifecycle events).
Also adds bakery/systemd/Forgejo CI packaging.

Validated end-to-end against a real Chromecast/Google TV: negotiated
Cast Streaming session, live pipeline playback, and daemon+GUI click-to-cast/
stop through the actual popup.

breadcast-caststream-sys/vendor/openscreen/util/crypto/openssl_util.cc

@@ -0,0 +1,62 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "util/crypto/openssl_util.h"
+
+#include <openssl/crypto.h>
+#include <openssl/err.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <utility>
+
+#include "util/osp_logging.h"
+
+namespace openscreen {
+
+namespace {
+
+// Callback routine for OpenSSL to print error messages. `str` is a
+// nullptr-terminated string of length `len` containing diagnostic information
+// such as the library, function and reason for the error, the file and line
+// where the error originated, plus potentially any context-specific
+// information about the error. `context` contains a pointer to user-supplied
+// data, which is currently unused.
+// If this callback returns a value <= 0, OpenSSL will stop processing the
+// error queue and return, otherwise it will continue calling this function
+// until all errors have been removed from the queue.
+int OpenSSLErrorCallback(const char* str, size_t len, void* context) {
+  OSP_DVLOG << "\t" << std::string_view(str, len);
+  return 1;
+}
+
+}  // namespace
+
+void EnsureOpenSSLInit() {
+  // LOCAL PATCH (breadcast): upstream calls OPENSSL_init_ssl() here, but
+  // this vendored subset never touches libssl (no TLS -- see
+  // ../../../PATCHES.md), so this just does the general libcrypto init
+  // instead. Safe to call repeatedly; OpenSSL 3.x makes this optional
+  // anyway, but frame_crypto.cc's key setup wants it done up front.
+  OPENSSL_init_crypto(0, nullptr);
+}
+
+void ClearOpenSSLERRStack(const Location& location) {
+  if (OSP_DCHECK_IS_ON()) {
+    uint32_t error_num = ERR_peek_error();
+    if (error_num == 0) {
+      return;
+    }
+
+    OSP_DVLOG << "OpenSSL ERR_get_error stack from " << location;
+    ERR_print_errors_cb(&OpenSSLErrorCallback, nullptr);
+  } else {
+    ERR_clear_error();
+  }
+}
+
+}  // namespace openscreen

breadcast-caststream-sys/vendor/openscreen/util/crypto/openssl_util.h

@@ -0,0 +1,61 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UTIL_CRYPTO_OPENSSL_UTIL_H_
+#define UTIL_CRYPTO_OPENSSL_UTIL_H_
+
+#include <stddef.h>
+
+#include <cstring>
+
+#include "platform/base/error.h"
+#include "platform/base/location.h"
+
+// LOCAL PATCH (breadcast): dropped SSLErrorCodeToError()/GetSSLError(),
+// which format an SSL_get_error() result and reference BoringSSL's
+// SSL_error_description() (not part of system OpenSSL's public API). Unused
+// here -- the TLS CASTV2 control channel is handled by the existing
+// rust_cast-based Rust code, not this vendored openscreen subset, which only
+// needs the general ERR_*/AES pieces. See vendor/openscreen/PATCHES.md.
+
+namespace openscreen {
+// Initialize OpenSSL if it isn't already initialized. This must be called
+// before any other OpenSSL functions though it is safe and cheap to call this
+// multiple times.
+// This function is thread-safe, and OpenSSL will only ever be initialized once.
+// OpenSSL will be properly shut down on program exit.
+// Multiple sequential calls to EnsureOpenSSLInit or EnsureOpenSSLCleanup are
+// ignored by OpenSSL itself.
+void EnsureOpenSSLInit();
+
+// Drains the OpenSSL ERR_get_error stack. On a debug build the error codes
+// are send to VLOG(1), on a release build they are disregarded. In most
+// cases you should pass CURRENT_LOCATION as the `location`.
+void ClearOpenSSLERRStack(const Location& location);
+
+// Place an instance of this class on the call stack to automatically clear
+// the OpenSSL error stack on function exit.
+class OpenSSLErrStackTracer {
+ public:
+  // Pass CURRENT_LOCATION as `location`, to help track the source of OpenSSL
+  // error messages. Note any diagnostic emitted will be tagged with the
+  // location of the constructor call as it's not possible to trace a
+  // destructor's callsite.
+  explicit OpenSSLErrStackTracer(const Location& location)
+      : location_(location) {
+    EnsureOpenSSLInit();
+  }
+  OpenSSLErrStackTracer(const OpenSSLErrStackTracer&) = delete;
+  OpenSSLErrStackTracer(OpenSSLErrStackTracer&&) noexcept = delete;
+  OpenSSLErrStackTracer& operator=(const OpenSSLErrStackTracer&) = delete;
+  OpenSSLErrStackTracer& operator=(OpenSSLErrStackTracer&&) = delete;
+  ~OpenSSLErrStackTracer() { ClearOpenSSLERRStack(location_); }
+
+ private:
+  const Location location_;
+};
+
+}  // namespace openscreen
+
+#endif  // UTIL_CRYPTO_OPENSSL_UTIL_H_

breadcast-caststream-sys/vendor/openscreen/util/crypto/random_bytes.cc

@@ -0,0 +1,23 @@
+// Copyright 2020 The Chromium Authors
+// 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 {
+
+std::array<uint8_t, 16> GenerateRandomBytes16() {
+  std::array<uint8_t, 16> result;
+  GenerateRandomBytes(result);
+  return result;
+}
+
+void GenerateRandomBytes(ByteBuffer out) {
+  // Working cryptography is mandatory for our library to run.
+  OSP_CHECK(RAND_bytes(out.data(), out.size()) == 1);
+}
+
+}  // namespace openscreen

breadcast-caststream-sys/vendor/openscreen/util/crypto/random_bytes.h

@@ -0,0 +1,20 @@
+// Copyright 2020 The Chromium Authors
+// 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>
+#include <cstdint>
+
+#include "platform/base/span.h"
+
+namespace openscreen {
+
+std::array<uint8_t, 16> GenerateRandomBytes16();
+void GenerateRandomBytes(ByteBuffer out);
+
+}  // namespace openscreen
+
+#endif  // UTIL_CRYPTO_RANDOM_BYTES_H_