Add client config export command

README.md

@@ -22,6 +22,7 @@ with.
 - `m2pack list`
 - `m2pack verify`
 - `m2pack extract`
+- `m2pack export-client-config`
 
 ## Build
 
@@ -68,6 +69,15 @@ Extract:
   --key keys/master.key
 ```
 
+Export a client config header for `m2dev-client-src/src/PackLib/M2PackKeys.h`:
+
+```bash
+./build/m2pack export-client-config \
+  --key keys/master.key \
+  --public-key keys/signing.pub \
+  --output /path/to/m2dev-client-src/src/PackLib/M2PackKeys.h
+```
+
 ## Format summary
 
 - Single archive file with a fixed header

docs/client-integration.md

@@ -19,6 +19,23 @@ tool.
    - machine-bound cache
    - or a derived release secret
 
+## Client key header
+
+For the current implementation, the client expects:
+
+- `src/PackLib/M2PackKeys.h`
+
+Generate it from the release key material with:
+
+```bash
+m2pack export-client-config \
+  --key keys/master.key \
+  --public-key keys/signing.pub \
+  --output /path/to/m2dev-client-src/src/PackLib/M2PackKeys.h
+```
+
+That keeps loader constants aligned with the archive builder.
+
 ## Runtime validation
 
 Minimum validation:

src/cli.cpp

@@ -102,7 +102,8 @@ void print_usage()
         << "  build --input <dir> --output <file> --key <hex-file> --sign-secret-key <hex-file> [--json]\n"
         << "  list --archive <file> [--json]\n"
         << "  verify --archive <file> [--public-key <hex-file>] [--key <hex-file>] [--json]\n"
-        << "  extract --archive <file> --output <dir> --key <hex-file> [--json]\n";
+        << "  extract --archive <file> --output <dir> --key <hex-file> [--json]\n"
+        << "  export-client-config --key <hex-file> --public-key <hex-file> --output <file> [--json]\n";
 }
 
 void command_keygen(const ParsedArgs& args)
@@ -261,6 +262,70 @@ void command_extract(const ParsedArgs& args)
     std::cout << "Extracted " << archive.entries.size() << " files\n";
 }
 
+void command_export_client_config(const ParsedArgs& args)
+{
+    const auto master = load_hex_file(require_option(args, "key"));
+    const auto public_key = load_hex_file(require_option(args, "public-key"));
+    const auto output_path = require_option(args, "output");
+
+    if (master.size() != kAeadKeySize)
+    {
+        fail("Master key must be 32 bytes");
+    }
+
+    if (public_key.size() != crypto_sign_PUBLICKEYBYTES)
+    {
+        fail("Signing public key has invalid size");
+    }
+
+    auto render_array = [](const std::vector<std::uint8_t>& bytes) {
+        std::ostringstream out;
+        for (std::size_t i = 0; i < bytes.size(); ++i)
+        {
+            if (i % 8 == 0)
+            {
+                out << "\n\t";
+            }
+            out << "0x" << to_hex(&bytes[i], 1);
+            if (i + 1 != bytes.size())
+            {
+                out << ", ";
+            }
+        }
+        out << "\n";
+        return out.str();
+    };
+
+    std::ostringstream header;
+    header
+        << "#pragma once\n\n"
+        << "#include <array>\n"
+        << "#include <cstdint>\n\n"
+        << "// Generated by m2pack export-client-config.\n"
+        << "// Do not edit manually.\n\n"
+        << "constexpr std::array<uint8_t, M2PACK_KEY_SIZE> M2PACK_MASTER_KEY = {"
+        << render_array(master)
+        << "};\n\n"
+        << "constexpr std::array<uint8_t, M2PACK_PUBLIC_KEY_SIZE> M2PACK_SIGN_PUBLIC_KEY = {"
+        << render_array(public_key)
+        << "};\n";
+
+    const auto text = header.str();
+    write_file(output_path, std::vector<std::uint8_t>(text.begin(), text.end()));
+
+    if (args.json)
+    {
+        std::cout
+            << "{"
+            << "\"ok\":true,"
+            << "\"output\":\"" << json_escape(output_path) << "\""
+            << "}\n";
+        return;
+    }
+
+    std::cout << "Wrote client config to " << output_path << "\n";
+}
+
 }  // namespace
 
 int run_cli(int argc, char** argv)
@@ -300,6 +365,11 @@ int run_cli(int argc, char** argv)
         command_extract(args);
         return 0;
     }
+    if (args.command == "export-client-config")
+    {
+        command_export_client_config(args);
+        return 0;
+    }
     if (args.command == "help" || args.command == "--help" || args.command == "-h")
     {
         print_usage();