fix #2: do not discard trailing zero in decrypted ekey.

src/jobs.hpp

@@ -59,6 +59,11 @@ 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

@@ -3,39 +3,31 @@
 #include "tc_tea.h"
 
 #include <algorithm>
-#include <string>
 #include <array>
+#include <string>
 #include <vector>
 
 const static std::string kEKeyV2Prefix = "UVFNdXNpYyBFbmNWMixLZXk6";
 const static std::array<uint8_t, 16> kEKeyV2Key1{
-    0x33, 0x38, 0x36, 0x5A, 0x4A, 0x59, 0x21, 0x40,
+    0x33, 0x38, 0x36, 0x5A, 0x4A, 0x59, 0x21, 0x40, 0x23, 0x2A, 0x24, 0x25, 0x5E, 0x26, 0x29, 0x28,
-    0x23, 0x2A, 0x24, 0x25, 0x5E, 0x26, 0x29, 0x28,
 };
 const static std::array<uint8_t, 16> kEKeyV2Key2{
-    0x2A, 0x2A, 0x23, 0x21, 0x28, 0x23, 0x24, 0x25,
+    0x2A, 0x2A, 0x23, 0x21, 0x28, 0x23, 0x24, 0x25, 0x26, 0x5E, 0x61, 0x31, 0x63, 0x5A, 0x2C, 0x54,
-    0x26, 0x5E, 0x61, 0x31, 0x63, 0x5A, 0x2C, 0x54,
 };
 
-template <typename T> std::span<T> ss2span(std::string_view sv) {
+template <typename T>
+std::span<T> ss2span(std::string_view sv) {
     auto* data = reinterpret_cast<const T*>(sv.data());
     return std::span<T>(const_cast<T*>(data), sv.size());
 }
 
-template <typename T> std::string_view span2ss(std::span<T> span) {
+template <typename T>
+std::string_view span2ss(std::span<T> span) {
     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 =
+    std::vector<uint8_t> result = b64_decode(reinterpret_cast<const uint8_t*>(ekey.data()), ekey.size());
-      b64_decode(reinterpret_cast<const uint8_t *>(ekey.data()), ekey.size());
-  remove_trailing_zeros(result);
 
     uint32_t tea_key[4] = {
         0x69005600 | static_cast<uint32_t>(result[0] << 16) | (result[1]),

src/tc_tea/tc_tea.cpp

@@ -10,8 +10,11 @@ constexpr size_t kTeaBlockSize = 8;
 constexpr size_t kFixedSaltLen = 2;
 constexpr size_t kZeroPadLen = 7;
 
-inline void decrypt_round(uint8_t *p_plain, const uint8_t *p_cipher,
+inline void decrypt_round(uint8_t* p_plain,
-                          uint64_t *iv1, uint64_t *iv2, const uint32_t *key) {
+                          const uint8_t* p_cipher,
+                          uint64_t* iv1,
+                          uint64_t* iv2,
+                          const uint32_t* key) {
     uint64_t iv1_next = Endian::be_u64_read(p_cipher);
     uint64_t iv2_next = tc_tea_ecb_decrypt(iv1_next ^ *iv2, key);
     uint64_t plain = iv2_next ^ *iv1;
@@ -20,8 +23,7 @@ inline void decrypt_round(uint8_t *p_plain, const uint8_t *p_cipher,
     Endian::be_u64_write(p_plain, plain);
 }
 
-std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher,
+std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher, const uint32_t* key) {
-                                        const uint32_t *key) {
     // It needs to have at least 2 blocks long, due to the nature of the padding
     // scheme used.
     if (cipher.size() % kTeaBlockSize != 0 || cipher.size() < kTeaBlockSize * 2) {
@@ -50,8 +52,7 @@ std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher,
 
     if (real_plain_len != copy_len) {
         // Decrypt the rest of the blocks
-    for (size_t i = cipher.size() - kTeaBlockSize * 3; i != 0;
+        for (size_t i = cipher.size() - kTeaBlockSize * 3; i != 0; i -= kTeaBlockSize) {
-         i -= kTeaBlockSize) {
             decrypt_round(p_output, in_cipher, &iv1, &iv2, key);
             in_cipher += kTeaBlockSize;
             p_output += kTeaBlockSize;

src/tc_tea/tc_tea.h

@@ -6,11 +6,9 @@
 #include <span>
 #include <vector>
 
-std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher,
+std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher, const uint32_t* key);
-                                        const uint32_t *key);
 
-inline std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher,
+inline std::vector<uint8_t> tc_tea_cbc_decrypt(std::span<uint8_t> cipher, const uint8_t* key) {
-                                               const uint8_t *key) {
     uint32_t key_u32[4];
     for (int i = 0; i < 4; i++) {
         key_u32[i] = Endian::be_u32_read(key + i * 4);