add ability to decrypt Ep3 GCI files

README.md

@@ -102,11 +102,15 @@ There are multiple PSO quest formats out there; newserv supports most of them. I
 | Format                    | Extension         | Supported online? | Offline decode option     |
 |---------------------------|-------------------|-------------------|---------------------------|
 | Compressed                | .bin/.dat         | Yes               | None (1)                  |
+| Compressed Ep3            | .bin              | Download only     | None (1)                  |
 | Uncompressed              | .bind/.datd       | Yes               | --compress-data (2)       |
+| Uncompressed Ep3          | .bind             | Download only     | --compress-data (2)       |
 | Unencrypted GCI           | .bin.gci/.dat.gci | Yes               | --decode-gci=FILENAME     |
 | Encrypted GCI with key    | .bin.gci/.dat.gci | Yes               | --decode-gci=FILENAME     |
 | Encrypted GCI without key | .bin.gci/.dat.gci | No                | --decode-gci=FILENAME (3) |
+| Ep3 GCI                   | .bin.gci          | Download only     | --decode-gci=FILENAME     |
 | Encrypted DLQ             | .bin.dlq/.dat.dlq | Yes               | --decode-dlq=FILENAME     |
+| Ep3 DLQ                   | .bin.dlq          | Download only     | --decode-dlq=FILENAME     |
 | QST                       | .qst              | Yes               | --decode-qst=FILENAME     |
 
 *Notes:*

src/Episode3.hh

@@ -237,7 +237,7 @@ struct Ep3CompressedMapHeader { // .mnm file format
   // Compressed data immediately follows (which decompresses to an Ep3Map)
 } __attribute__((packed));
 
-struct Ep3Map { // .mnmd format
+struct Ep3Map { // .mnmd format; also the format of (decompressed) Ep3 quests
   /* 0000 */ be_uint32_t unknown_a1;
   /* 0004 */ be_uint32_t map_number;
   /* 0008 */ uint8_t width;

src/Quest.cc

@@ -70,8 +70,10 @@ struct ShuffleTables {
 };
 
 struct PSOGCIFileHeader {
-  parray<uint8_t, 0x40> gci_header;
+  parray<char, 4> game_id; // 'GPOE', 'GPSP', etc.
-  ptext<char, 0x1C> game_name; // e.g. "PSO EPISODE I & II"
+  parray<char, 2> developer_id; // '8P' for Sega
+  parray<uint8_t, 0x3A> remaining_gci_header; // There is a structure for this but we don't use it
+  ptext<char, 0x1C> game_name; // e.g. "PSO EPISODE I & II" or "PSO EPISODE III"
   be_uint32_t embedded_seed; // Used in some of Ralf's quest packs
   ptext<char, 0x20> quest_name;
   parray<uint8_t, 0x2000> banner_and_icon;
@@ -294,18 +296,6 @@ struct PSOQuestHeaderGC {
   ptext<char, 0x120> long_description;
 } __attribute__((packed));
 
-struct PSOQuestHeaderGCEpisode3 {
-  // there's actually a lot of other important stuff in here but I'm lazy. it
-  // looks like map data, cutscene data, and maybe special cards used during
-  // the quest
-  parray<uint8_t, 0x1DF0> unknown_a1;
-  ptext<char, 0x14> name;
-  ptext<char, 0x14> location;
-  ptext<char, 0x3C> location2;
-  ptext<char, 0x190> description;
-  parray<uint8_t, 0x3A34> unknown_a2;
-} __attribute__((packed));
-
 struct PSOQuestHeaderBB {
   uint32_t start_offset;
   uint32_t unknown_offset1;
@@ -464,14 +454,14 @@ Quest::Quest(const string& bin_filename)
     case GameVersion::GC: {
       if (this->category == QuestCategory::EPISODE_3) {
         // these all appear to be the same size
-        if (bin_decompressed.size() != sizeof(PSOQuestHeaderGCEpisode3)) {
+        if (bin_decompressed.size() != sizeof(Ep3Map)) {
           throw invalid_argument("file is incorrect size");
         }
-        auto* header = reinterpret_cast<const PSOQuestHeaderGCEpisode3*>(bin_decompressed.data());
+        auto* header = reinterpret_cast<const Ep3Map*>(bin_decompressed.data());
         this->joinable = false;
         this->episode = 0xFF;
         this->name = decode_sjis(header->name);
-        this->short_description = decode_sjis(header->location2);
+        this->short_description = decode_sjis(header->quest_name);
         this->long_description = decode_sjis(header->description);
       } else {
         if (bin_decompressed.size() < sizeof(PSOQuestHeaderGC)) {
@@ -596,6 +586,17 @@ string Quest::decode_gci(
     throw runtime_error("GCI file unencrypted header checksum is incorrect");
   }
 
+  if (header.developer_id[0] != '8' || header.developer_id[1] != 'P') {
+    throw runtime_error("GCI file is not for a Sega game");
+  }
+  if (header.game_id[0] != 'G') {
+    throw runtime_error("GCI file is not for a GameCube game");
+  }
+  if (header.game_id[1] != 'P') {
+    throw runtime_error("GCI file is not for Phantasy Star Online");
+  }
+
+  if (header.game_id[2] == 'O') { // Episodes 1&2 (GPO*)
     const auto& encrypted_header = r.get<PSOGCIFileEncryptedHeader>(false);
     // Unencrypted GCI files appear to always have zeroes in these fields.
     // Encrypted GCI files are highly unlikely to have zeroes in ALL of these
@@ -634,6 +635,48 @@ string Quest::decode_gci(
 
       return compressed_data;
     }
+
+  } else if (header.game_id[2] == 'S') { // Episode 3
+    // The first 0x10 bytes in the data segment appear to be unused. In most
+    // files I've seen, the last half of it (8 bytes) are duplicates of the
+    // first 8 bytes of the unscrambled, compressed data, though this is likely
+    // the result of an uninitialized memory bug when the client encodes the
+    // file and not an actual constraint on what should be in these 8 bytes.
+    r.skip(16);
+    // The game treats this field as a 16-byte string (including the \0). The 8
+    // bytes after it appear to be completely unused.
+    if (r.readx(15) != "SONICTEAM,SEGA.") {
+      throw runtime_error("Episode 3 GCI file is not a quest");
+    }
+    r.skip(9);
+
+    data = r.readx(header.data_size - 40);
+
+    // For some reason, Sega decided not to encrypt Episode 3 quest files in the
+    // same way as Episodes 1&2 quest files (see above). Instead, they just
+    // wrote a fairly trivial XOR loop over the first 0x100 bytes, leaving the
+    // remaining bytes completely unencrypted (but still compressed).
+    size_t unscramble_size = min<size_t>(0x100, data.size());
+    {
+      uint8_t key = 0x80; // Technically basis + 0x80, but basis is zero
+      for (size_t z = 0; z < unscramble_size; z++) {
+        key = (key * 5) + 1;
+        data[z] ^= key;
+      }
+    }
+
+    size_t decompressed_size = prs_decompress_size(data);
+    if (decompressed_size != sizeof(Ep3Map)) {
+      throw runtime_error(string_printf(
+          "decompressed quest is 0x%zX bytes; expected 0x%zX bytes",
+          decompressed_size, sizeof(Ep3Map)));
+    }
+
+    return data;
+
+  } else {
+    throw runtime_error("unknown game name in GCI header");
+  }
 }
 
 string Quest::decode_dlq(const string& filename) {

src/Text.hh

@@ -11,12 +11,6 @@
 
 
 
-// TODO: delete these if not needed
-// int char16ncmp(const char16_t* s1, const char16_t* s2, size_t count);
-// size_t char16len(const char16_t* s);
-
-
-
 // (1a) Conversion functions
 
 // These return the number of characters written, including the terminating null