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fix some edge cases in gci decryption

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This commit is contained in:
Martin Michelsen
2022-09-14 23:40:59 -07:00
parent 34d32418e3
commit 481b9b3040
2 changed files with 41 additions and 14 deletions
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src/Quest.cc
+24 -6
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@@ -71,7 +71,9 @@ struct ShuffleTables {
struct PSOGCIFileHeader {
parray<uint8_t, 0x40> gci_header;
parray<uint8_t, 0x40> pso_header;
ptext<char, 0x1C> game_name; // e.g. "PSO EPISODE I & II"
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;
// data_size specifies the number of bytes in the encrypted section, including
// the encrypted header (below) and all encrypted data after it.
@@ -82,7 +84,9 @@ struct PSOGCIFileHeader {
be_uint32_t checksum;
bool checksum_correct() const {
uint32_t cs = crc32(&this->pso_header, sizeof(this->pso_header));
uint32_t cs = crc32(&this->game_name, sizeof(this->game_name));
cs = crc32(&this->embedded_seed, sizeof(this->embedded_seed), cs);
cs = crc32(&this->quest_name, sizeof(this->quest_name), cs);
cs = crc32(&this->banner_and_icon, sizeof(this->banner_and_icon), cs);
cs = crc32(&this->data_size, sizeof(this->data_size), cs);
cs = crc32("\0\0\0\0", 4, cs);
@@ -110,7 +114,6 @@ string decrypt_gci_data_section(
shuf.shuffle(decrypted.data(), data_section, size, true);
}
decrypted.resize((decrypted.size() + 3) & (~3));
auto* be_dwords = reinterpret_cast<be_uint32_t*>(decrypted.data());
PSOV2Encryption crypt(seed);
@@ -132,13 +135,24 @@ string decrypt_gci_data_section(
throw runtime_error("incorrect decrypted data section checksum");
}
size_t orig_size = decrypted.size();
decrypted.resize((orig_size + 3) & (~3));
PSOV2Encryption(header->round3_seed).decrypt(
decrypted.data() + sizeof(PSOGCIFileEncryptedHeader),
decrypted.size() - sizeof(PSOGCIFileEncryptedHeader));
decrypted.resize(orig_size);
string ret = decrypted.substr(sizeof(PSOGCIFileEncryptedHeader));
if (prs_decompress_size(ret) != header->decompressed_size) {
throw runtime_error("decompressed size does not match size in header");
// Some GCI files have decompressed_size fields that are 8 bytes smaller than
// the actual decompressed size of the data. They seem to work fine, so we
// accept both cases as correct.
size_t decompressed_size = prs_decompress_size(ret);
if ((decompressed_size != header->decompressed_size) &&
(decompressed_size != header->decompressed_size - 8)) {
throw runtime_error(string_printf(
"decompressed size (%zu) does not match size in header (%" PRId32 ")",
decompressed_size, header->decompressed_size.load()));
}
return ret;
@@ -594,6 +608,10 @@ string Quest::decode_gci(
return decrypt_gci_data_section(
r.getv(header.data_size), header.data_size, known_seed);
} else if (header.embedded_seed != 0) {
return decrypt_gci_data_section(
r.getv(header.data_size), header.data_size, header.embedded_seed);
} else {
if (find_seed_num_threads < 0) {
throw runtime_error("GCI file appears to be encrypted");
@@ -607,7 +625,7 @@ string Quest::decode_gci(
} else { // Unencrypted GCI format
r.skip(sizeof(PSOGCIFileEncryptedHeader));
string compressed_data = r.read(r.remaining());
string compressed_data = r.readx(header.data_size - sizeof(PSOGCIFileEncryptedHeader));
size_t decompressed_bytes = prs_decompress_size(compressed_data);
size_t expected_decompressed_bytes = encrypted_header.decompressed_size - 8;