add extract-ppk action

src/PPKArchive.cc

@@ -0,0 +1,76 @@
+#include "AFSArchive.hh"
+
+#include <stdio.h>
+#include <string.h>
+
+#include <phosg/Encoding.hh>
+#include <phosg/Filesystem.hh>
+#include <phosg/Strings.hh>
+
+#include "Compression.hh"
+#include "Text.hh"
+
+using namespace std;
+
+struct Entry {
+  pstring<TextEncoding::ASCII, 0x80> filename;
+  le_uint32_t unknown_a1;
+  le_uint32_t decompressed_size;
+  le_uint32_t compressed_size;
+  le_uint32_t checksum;
+  // Data follows immediately here
+  // Trailer: le_uint32_t entry_size; //
+};
+
+static void decrypt_ppk_data(std::string& data, const std::string& filename, const std::string& password) {
+  if (password.size() > 0xFF) {
+    throw runtime_error("password is too long");
+  }
+
+  uint8_t key[0x100];
+  for (size_t z = 0; z < 0x100; z++) {
+    key[z] = z ^ filename[z % filename.size()];
+  }
+  for (size_t z = 0; z < password.size(); z++) {
+    key[z + 1] ^= password[z];
+  }
+  for (size_t z = 0; z < 0xFC; z++) {
+    key[z + 4] ^= key[z];
+  }
+  for (size_t z = 0; z < data.size(); z++) {
+    data[z] ^= key[z & 0xFF];
+  }
+}
+
+std::unordered_map<std::string, std::string> decode_ppk_file(const std::string& data, const std::string& password) {
+  phosg::StringReader r(data);
+
+  uint32_t signature = r.get_u32b();
+  if (signature != 0x50503130 && signature != 0x4D5A5000) { // 'PP10' or 'MZP\0'
+    throw runtime_error("file is not a ppk archive");
+  }
+
+  unordered_map<string, string> ret;
+  for (size_t offset = r.size() - 4; offset >= 4;) {
+    uint32_t size = r.pget_u32l(offset) ^ 0x12345678;
+    uint32_t entry_offset = offset - size;
+    const auto& entry = r.pget<Entry>(entry_offset);
+    string data = r.pread(entry_offset + sizeof(Entry), entry.compressed_size);
+    string filename = entry.filename.decode();
+    decrypt_ppk_data(data, phosg::tolower(filename), password);
+    uint32_t checksum = phosg::crc32(data.data(), data.size());
+    if (checksum != entry.checksum) {
+      throw runtime_error(phosg::string_printf(
+          "incorrect checksum for file %s (expected %08" PRIX32 "; received %08" PRIX32 ")",
+          filename.c_str(), entry.checksum.load(), checksum));
+    }
+    if (entry.compressed_size < entry.decompressed_size) {
+      data = prs_decompress(data);
+    }
+    if (!ret.emplace(filename, data).second) {
+      throw runtime_error(phosg::string_printf("archive contains multiple files with the same name (%s)", filename.c_str()));
+    }
+    offset = entry_offset - 4;
+  }
+  return ret;
+}