src/common/base64.h

@@ -4,4 +4,4 @@
 #include <cstdint>
 #include <vector>
 
-std::vector<uint8_t> b64_decode(const uint8_t* input, size_t len);
+std::vector<uint8_t> b64_decode(const uint8_t *input, size_t len);

src/jobs.hpp

@@ -59,11 +59,6 @@ class KggTask {
         }
 
         auto qmc2 = QMC2::Create(ekey);
-        if (!qmc2) {
-            error(L"create qmc2 instance failed (ekey decode error?)");
-            fprintf(stderr, "%s\n", ekey.c_str());
-            return;
-        }
 
         std::string magic(4, 0);
         kgg_stream_in.seekg(offset_to_audio, std::ios::beg);

src/qmc2/ekey.cpp

@@ -3,59 +3,67 @@
 #include "tc_tea.h"
 
 #include <algorithm>
-#include <array>
 #include <string>
+#include <array>
 #include <vector>
 
 const static std::string kEKeyV2Prefix = "UVFNdXNpYyBFbmNWMixLZXk6";
 const static std::array<uint8_t, 16> kEKeyV2Key1{
-    0x33, 0x38, 0x36, 0x5A, 0x4A, 0x59, 0x21, 0x40, 0x23, 0x2A, 0x24, 0x25, 0x5E, 0x26, 0x29, 0x28,
+    0x33, 0x38, 0x36, 0x5A, 0x4A, 0x59, 0x21, 0x40,
+    0x23, 0x2A, 0x24, 0x25, 0x5E, 0x26, 0x29, 0x28,
 };
 const static std::array<uint8_t, 16> kEKeyV2Key2{
-    0x2A, 0x2A, 0x23, 0x21, 0x28, 0x23, 0x24, 0x25, 0x26, 0x5E, 0x61, 0x31, 0x63, 0x5A, 0x2C, 0x54,
+    0x2A, 0x2A, 0x23, 0x21, 0x28, 0x23, 0x24, 0x25,
+    0x26, 0x5E, 0x61, 0x31, 0x63, 0x5A, 0x2C, 0x54,
 };
 
-template <typename T>
+template <typename T> std::span<T> ss2span(std::string_view sv) {
-std::span<T> ss2span(std::string_view sv) {
+  auto *data = reinterpret_cast<const T *>(sv.data());
-    auto* data = reinterpret_cast<const T*>(sv.data());
+  return std::span<T>(const_cast<T *>(data), sv.size());
-    return std::span<T>(const_cast<T*>(data), sv.size());
 }
 
-template <typename T>
+template <typename T> std::string_view span2ss(std::span<T> span) {
-std::string_view span2ss(std::span<T> span) {
+  return std::string_view(reinterpret_cast<char *>(span.data()), span.size());
-    return std::string_view(reinterpret_cast<char*>(span.data()), span.size());
+}
+
+void remove_trailing_zeros(std::vector<uint8_t> &vec) {
+  auto it = std::find_if(vec.rbegin(), vec.rend(),
+                         [](uint8_t value) { return value != 0; });
+  vec.erase(it.base(), vec.end());
 }
 
 std::vector<uint8_t> decrypt_ekey_v1(std::string_view ekey) {
-    std::vector<uint8_t> result = b64_decode(reinterpret_cast<const uint8_t*>(ekey.data()), ekey.size());
+  std::vector<uint8_t> result =
+      b64_decode(reinterpret_cast<const uint8_t *>(ekey.data()), ekey.size());
+  remove_trailing_zeros(result);
 
-    uint32_t tea_key[4] = {
+  uint32_t tea_key[4] = {
-        0x69005600 | static_cast<uint32_t>(result[0] << 16) | (result[1]),
+      0x69005600 | static_cast<uint32_t>(result[0] << 16) | (result[1]),
-        0x46003800 | static_cast<uint32_t>(result[2] << 16) | (result[3]),
+      0x46003800 | static_cast<uint32_t>(result[2] << 16) | (result[3]),
-        0x2b002000 | static_cast<uint32_t>(result[4] << 16) | (result[5]),
+      0x2b002000 | static_cast<uint32_t>(result[4] << 16) | (result[5]),
-        0x15000b00 | static_cast<uint32_t>(result[6] << 16) | (result[7]),
+      0x15000b00 | static_cast<uint32_t>(result[6] << 16) | (result[7]),
-    };
+  };
-    auto decrypted = tc_tea_cbc_decrypt(std::span(result).subspan(8), tea_key);
+  auto decrypted = tc_tea_cbc_decrypt(std::span(result).subspan(8), tea_key);
-    if (decrypted.empty()) {
+  if (decrypted.empty()) {
-        return {};
+    return {};
-    }
+  }
-    result.resize(8);
+  result.resize(8);
-    result.insert(result.end(), decrypted.begin(), decrypted.end());
+  result.insert(result.end(), decrypted.begin(), decrypted.end());
-    return result;
+  return result;
 }
 
 std::vector<uint8_t> decrypt_ekey_v2(std::string_view ekey) {
-    std::vector<uint8_t> result;
+  std::vector<uint8_t> result;
-    result = tc_tea_cbc_decrypt(ss2span<uint8_t>(ekey), kEKeyV2Key1.data());
+  result = tc_tea_cbc_decrypt(ss2span<uint8_t>(ekey), kEKeyV2Key1.data());
-    result = tc_tea_cbc_decrypt(std::span(result), kEKeyV2Key2.data());
+  result = tc_tea_cbc_decrypt(std::span(result), kEKeyV2Key2.data());
-    return decrypt_ekey_v1(span2ss(std::span(result)));
+  return decrypt_ekey_v1(span2ss(std::span(result)));
 }
 
 std::vector<uint8_t> decrypt_ekey(std::string_view ekey) {
-    if (ekey.starts_with(kEKeyV2Prefix)) {
+  if (ekey.starts_with(kEKeyV2Prefix)) {
-        ekey.remove_prefix(kEKeyV2Prefix.size());
+    ekey.remove_prefix(kEKeyV2Prefix.size());
-        return decrypt_ekey_v2(ekey);
+    return decrypt_ekey_v2(ekey);
-    }
+  }
 
-    return decrypt_ekey_v1(ekey);
+  return decrypt_ekey_v1(ekey);
 }

src/qmc2/qmc2_factory.cpp

@@ -4,17 +4,17 @@
 namespace QMC2 {
 
 std::unique_ptr<QMC2_Base> Create(std::string_view ekey) {
-    auto key = decrypt_ekey(ekey);
+  auto key = decrypt_ekey(ekey);
-    auto key_len = key.size();
+  auto key_len = key.size();
-    if (key_len == 0) {
+  if (key_len == 0) {
-        return nullptr;
+    return nullptr;
-    }
+  }
 
-    if (key_len < 300) {
+  if (key_len < 300) {
-        return std::make_unique<QMC2_MAP>(std::span(key));
+    return std::make_unique<QMC2_MAP>(std::span(key));
-    } else {
+  } else {
-        return std::make_unique<QMC2_RC4>(std::span(key));
+    return std::make_unique<QMC2_RC4>(std::span(key));
-    }
+  }
 }
 
-}  // namespace QMC2
+} // namespace QMC2

src/tc_tea/tc_tea.cpp

@@ -10,62 +10,61 @@ constexpr size_t kTeaBlockSize = 8;
 constexpr size_t kFixedSaltLen = 2;
 constexpr size_t kZeroPadLen = 7;
 
-inline void decrypt_round(uint8_t* p_plain,
+inline void decrypt_round(uint8_t *p_plain, const uint8_t *p_cipher,
-                          const uint8_t* p_cipher,
+                          uint64_t *iv1, uint64_t *iv2, const uint32_t *key) {
-                          uint64_t* iv1,
+  uint64_t iv1_next = Endian::be_u64_read(p_cipher);
-                          uint64_t* iv2,
+  uint64_t iv2_next = tc_tea_ecb_decrypt(iv1_next ^ *iv2, key);
-                          const uint32_t* key) {
+  uint64_t plain = iv2_next ^ *iv1;
-    uint64_t iv1_next = Endian::be_u64_read(p_cipher);
+  *iv1 = iv1_next;
-    uint64_t iv2_next = tc_tea_ecb_decrypt(iv1_next ^ *iv2, key);
+  *iv2 = iv2_next;
-    uint64_t plain = iv2_next ^ *iv1;
+  Endian::be_u64_write(p_plain, plain);
-    *iv1 = iv1_next;
-    *iv2 = iv2_next;
-    Endian::be_u64_write(p_plain, plain);
 }
 
-std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher, const uint32_t* key) {
+std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher,
-    // It needs to have at least 2 blocks long, due to the nature of the padding
+                                        const uint32_t *key) {
-    // scheme used.
+  // It needs to have at least 2 blocks long, due to the nature of the padding
-    if (cipher.size() % kTeaBlockSize != 0 || cipher.size() < kTeaBlockSize * 2) {
+  // scheme used.
-        return {};
+  if (cipher.size() % kTeaBlockSize != 0 || cipher.size() < kTeaBlockSize * 2) {
+    return {};
+  }
+
+  uint64_t iv1 = 0;
+  uint64_t iv2 = 0;
+  uint8_t header[kTeaBlockSize * 2];
+  const uint8_t *in_cipher = cipher.data();
+  decrypt_round(header, in_cipher, &iv1, &iv2, key);
+  in_cipher += kTeaBlockSize;
+  decrypt_round(header + kTeaBlockSize, in_cipher, &iv1, &iv2, key);
+  in_cipher += kTeaBlockSize;
+
+  size_t hdr_skip_len = 1 + (header[0] & 7) + kFixedSaltLen;
+  size_t real_plain_len = cipher.size() - hdr_skip_len - kZeroPadLen;
+  std::vector<uint8_t> result(real_plain_len);
+
+  auto p_output = result.data();
+
+  // copy first block of plain text
+  size_t copy_len = std::min(sizeof(header) - hdr_skip_len, real_plain_len);
+  std::copy_n(header + hdr_skip_len, real_plain_len, p_output);
+  p_output += copy_len;
+
+  if (real_plain_len != copy_len) {
+    // Decrypt the rest of the blocks
+    for (size_t i = cipher.size() - kTeaBlockSize * 3; i != 0;
+         i -= kTeaBlockSize) {
+      decrypt_round(p_output, in_cipher, &iv1, &iv2, key);
+      in_cipher += kTeaBlockSize;
+      p_output += kTeaBlockSize;
     }
 
-    uint64_t iv1 = 0;
-    uint64_t iv2 = 0;
-    uint8_t header[kTeaBlockSize * 2];
-    const uint8_t* in_cipher = cipher.data();
-    decrypt_round(header, in_cipher, &iv1, &iv2, key);
-    in_cipher += kTeaBlockSize;
     decrypt_round(header + kTeaBlockSize, in_cipher, &iv1, &iv2, key);
-    in_cipher += kTeaBlockSize;
+    p_output[0] = header[kTeaBlockSize];
+  }
+  // Validate zero padding
+  auto verify = Endian::be_u64_read(header + kTeaBlockSize) << 8;
+  if (verify != 0) {
+    result.resize(0);
+  }
 
-    size_t hdr_skip_len = 1 + (header[0] & 7) + kFixedSaltLen;
+  return result;
-    size_t real_plain_len = cipher.size() - hdr_skip_len - kZeroPadLen;
-    std::vector<uint8_t> result(real_plain_len);
-
-    auto p_output = result.data();
-
-    // copy first block of plain text
-    size_t copy_len = std::min(sizeof(header) - hdr_skip_len, real_plain_len);
-    std::copy_n(header + hdr_skip_len, real_plain_len, p_output);
-    p_output += copy_len;
-
-    if (real_plain_len != copy_len) {
-        // Decrypt the rest of the blocks
-        for (size_t i = cipher.size() - kTeaBlockSize * 3; i != 0; i -= kTeaBlockSize) {
-            decrypt_round(p_output, in_cipher, &iv1, &iv2, key);
-            in_cipher += kTeaBlockSize;
-            p_output += kTeaBlockSize;
-        }
-
-        decrypt_round(header + kTeaBlockSize, in_cipher, &iv1, &iv2, key);
-        p_output[0] = header[kTeaBlockSize];
-    }
-    // Validate zero padding
-    auto verify = Endian::be_u64_read(header + kTeaBlockSize) << 8;
-    if (verify != 0) {
-        result.resize(0);
-    }
-
-    return result;
 }

src/tc_tea/tc_tea.h

@@ -6,12 +6,14 @@
 #include <span>
 #include <vector>
 
-std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher, const uint32_t* key);
+std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher,
+                                        const uint32_t *key);
 
-inline std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher, const uint8_t* key) {
+inline std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher,
-    uint32_t key_u32[4];
+                                               const uint8_t *key) {
-    for (int i = 0; i < 4; i++) {
+  uint32_t key_u32[4];
-        key_u32[i] = Endian::be_u32_read(key + i * 4);
+  for (int i = 0; i < 4; i++) {
-    }
+    key_u32[i] = Endian::be_u32_read(key + i * 4);
-    return tc_tea_cbc_decrypt(cipher, key_u32);
+  }
+  return tc_tea_cbc_decrypt(cipher, key_u32);
 }