Achievements: Add encryption of login tokens

dep/rcheevos/include/rc_client.h

@@ -217,6 +217,47 @@ typedef struct rc_client_user_game_summary_t {
  */
 RC_EXPORT void RC_CCONV rc_client_get_user_game_summary(const rc_client_t* client, rc_client_user_game_summary_t* summary);
 
+/**
+ * Simple encryption that can be used to protect API tokens in configuration. We do not provide
+ * any cryptographic guarantees other than a significantly increased difficulty of getting the
+ * API token if a user shares their configuration file.
+ */
+
+#define RC_CLIENT_LOGIN_ENCRYPTION_KEY_LENGTH 32 /* 128-bit key, 128-bit IV */
+
+/**
+ * Computes the AES key to use for encryption API tokens.
+ * This key is based on a UUID that is unique to the computer that it is running on, with an
+ * optional salt. One possible option for a salt is the username.
+ */
+RC_EXPORT int RC_CCONV rc_client_get_login_encryption_key(uint8_t key[RC_CLIENT_LOGIN_ENCRYPTION_KEY_LENGTH],
+                                                          const void* salt, size_t salt_length);
+
+/**
+ * Returns the length of a given API token after it has been encrypted. AES operates in blocks
+ * of 128 bits/16 bytes, therefore the encrypted token must be a multiple of 16 bytes in size.
+ */
+RC_EXPORT size_t RC_CCONV rc_client_get_encrypted_login_length(size_t plaintext_length);
+
+/**
+ * Encrypts an API token, protecting it against accidental exposure by sharing configurations.
+ * The token is encrypted using AES-128. You should convert the returned ciphertext to hex before
+ * storing it in a configuration file, as it will contain non-printable characters. ciphertext
+ * should be sized according to rc_client_get_encrypted_login_length().
+ */
+RC_EXPORT int RC_CCONV rc_client_encrypt_login(const uint8_t key[RC_CLIENT_LOGIN_ENCRYPTION_KEY_LENGTH],
+                                               const char* plaintext, size_t plaintext_length, uint8_t* ciphertext,
+                                               size_t ciphertext_length);
+
+/**
+ * Decrypts a previously-encrypted API token.
+ * plaintext should be at least ciphertext_length in size. If the token is not a multiple of 16
+ * bytes in size, the actual size of the token will be returned in plaintext_length.
+ */
+RC_EXPORT int RC_CCONV rc_client_decrypt_login(const uint8_t key[RC_CLIENT_LOGIN_ENCRYPTION_KEY_LENGTH],
+                                               const uint8_t* ciphertext, size_t ciphertext_length, char* plaintext,
+                                               size_t* plaintext_length);
+
 /*****************************************************************************\
 | Game                                                                        |
 \*****************************************************************************/

dep/rcheevos/src/rc_client.c

@@ -11,6 +11,10 @@
 
 #include "rcheevos/rc_internal.h"
 
+/* TODO: Is this appropriate? */
+#include "rhash/aes.h"
+#include "rhash/sha256.h"
+
 #include <stdarg.h>
 
 #ifdef _WIN32
@@ -18,6 +22,8 @@
 #include <windows.h>
 #include <profileapi.h>
 #else
+#include <unistd.h>
+#include <sys/stat.h>
 #include <time.h>
 #endif
 
@@ -901,6 +907,168 @@ void rc_client_get_user_game_summary(const rc_client_t* client, rc_client_user_g
   rc_mutex_unlock((rc_mutex_t*)&client->state.mutex); /* remove const cast for mutex access */
 }
 
+static int rc_client_get_machine_uuid_string(const void** uuid, size_t* uuid_length)
+{
+#ifdef _WIN32
+  HKEY hKey;
+  DWORD machine_guid_length;
+  const char* machine_guid;
+
+  if (RegOpenKeyExW(HKEY_LOCAL_MACHINE, L"SOFTWARE\\Microsoft\\Cryptography", 0, KEY_READ, &hKey) != ERROR_SUCCESS)
+    return 0;
+
+  if (RegGetValueA(hKey, NULL, "MachineGuid", RRF_RT_REG_SZ, NULL, NULL, &machine_guid_length) != ERROR_SUCCESS)
+  {
+    RegCloseKey(hKey);
+    return 0;
+  }
+
+  machine_guid = (char*)malloc(machine_guid_length);
+  if (machine_guid == NULL ||
+      RegGetValueA(hKey, NULL, "MachineGuid", RRF_RT_REG_SZ, NULL, machine_guid, &machine_guid_length) !=
+        ERROR_SUCCESS ||
+      machine_guid_length <= 1)
+  {
+    free(machine_guid);
+    RegCloseKey(hKey);
+    return 0;
+  }
+
+  RegCloseKey(hKey);
+  *uuid = machine_guid;
+  *uuid_length = machine_guid_length - 1; /* drop terminating zero */
+  return 1;
+#else
+  long hostid;
+
+#ifdef __linux__
+  /* use /etc/machine-id on Linux */
+  int fd;
+  struct stat sd;
+  char* machine_id;
+
+  fd = open("/etc/machine-id", O_RDONLY);
+  if (fd >= 0)
+  {
+    if (fstat(fd, &sd) == 0 && sd.st_size > 0)
+    {
+      machine_id = (char*)malloc(sd.st_size);
+      if (machine_id != NULL && read(fd, machine_id, sd.st_size) == sd.st_size)
+      {
+        *uuid = machine_id;
+        *uuid_length = sd.st_size;
+        close(fd);
+        return 1;
+      }
+
+      free(machine_id);
+    }
+
+    close(fd);
+  }
+#endif
+
+  // fallback to POSIX gethostid()
+  hostid = gethostid();
+  *uuid = malloc(sizeof(hostid));
+  memcpy((void*)uuid, &hostid, sizeof(hostid));
+  return 1;
+#endif
+}
+
+int rc_client_get_login_encryption_key(uint8_t key[RC_CLIENT_LOGIN_ENCRYPTION_KEY_LENGTH], const void* salt,
+                                       size_t salt_length)
+{
+  /* super basic key stretching */
+  static const int EXTRA_ROUNDS = 100;
+
+  const void* machine_uuid;
+  size_t machine_uuid_length;
+  SHA256_CTX sha256_ctx;
+  int i;
+
+  if (!rc_client_get_machine_uuid_string(&machine_uuid, &machine_uuid_length))
+    return RC_API_FAILURE;
+
+  sha256_init(&sha256_ctx);
+  sha256_update(&sha256_ctx, (const uint8_t*)machine_uuid, machine_uuid_length);
+  if (salt_length > 0)
+    sha256_update(&sha256_ctx, (const uint8_t*)salt, salt_length);
+  sha256_final(&sha256_ctx, key);
+
+  for (int i = 0; i < EXTRA_ROUNDS; i++)
+  {
+    sha256_init(&sha256_ctx);
+    sha256_update(&sha256_ctx, key, RC_CLIENT_LOGIN_ENCRYPTION_KEY_LENGTH);
+    sha256_final(&sha256_ctx, key);
+  }
+
+  free(machine_uuid);
+
+  return RC_OK;
+}
+
+size_t rc_client_get_encrypted_login_length(size_t plaintext_length)
+{
+  /* ciphertext should be aligned to block size */
+  return (((plaintext_length + (AES_BLOCKLEN - 1)) / AES_BLOCKLEN) * AES_BLOCKLEN);
+}
+
+int rc_client_encrypt_login(const uint8_t key[RC_CLIENT_LOGIN_ENCRYPTION_KEY_LENGTH], const char* plaintext,
+                            size_t plaintext_length, uint8_t* ciphertext, size_t ciphertext_length)
+{
+  struct AES_ctx aes_ctx;
+  size_t padding_size;
+  size_t i;
+
+  /* ciphertext should be aligned to block size */
+  if (ciphertext_length < (((plaintext_length + (AES_BLOCKLEN - 1)) / AES_BLOCKLEN) * AES_BLOCKLEN) ||
+      (ciphertext_length % AES_BLOCKLEN) != 0)
+  {
+    return RC_INSUFFICIENT_BUFFER;
+  }
+
+  memcpy(ciphertext, plaintext, plaintext_length);
+  padding_size = ciphertext_length - plaintext_length;
+  if (padding_size > 0)
+    memset(&ciphertext[plaintext_length], 0, padding_size);
+
+  AES_init_ctx(&aes_ctx, key);
+  AES_ctx_set_iv(&aes_ctx, key + 16); /* second part of 256-bit key is the IV */
+  AES_CBC_encrypt_buffer(&aes_ctx, ciphertext, ciphertext_length);
+  return RC_OK;
+}
+
+int rc_client_decrypt_login(const uint8_t key[RC_CLIENT_LOGIN_ENCRYPTION_KEY_LENGTH], const uint8_t* ciphertext,
+                            size_t ciphertext_length, char* plaintext, size_t* plaintext_length)
+{
+  struct AES_ctx aes_ctx;
+  size_t len;
+
+  /* ciphertext should be aligned to block size */
+  if ((ciphertext_length % AES_BLOCKLEN) != 0)
+    return RC_INSUFFICIENT_BUFFER;
+
+  /* decrypt_buffer is an inout parameter, need to copy */
+  memcpy(plaintext, ciphertext, ciphertext_length);
+
+  AES_init_ctx(&aes_ctx, key);
+  AES_ctx_set_iv(&aes_ctx, key + 16); /* second part of 256-bit key is the IV */
+  AES_CBC_decrypt_buffer(&aes_ctx, plaintext, ciphertext_length);
+
+  /* may not be null terminated, and C89 has no safe strlen... */
+  len = 0;
+  while (len < ciphertext_length)
+  {
+    if (plaintext[len] == '\0')
+      break;
+    len++;
+  }
+
+  *plaintext_length = len;
+  return RC_OK;
+}
+
 /* ===== Game ===== */
 
 static void rc_client_free_game(rc_client_game_info_t* game)

src/core/achievements.cpp

@@ -41,6 +41,7 @@
 #include "imgui_internal.h"
 #include "rc_api_runtime.h"
 #include "rc_client.h"
+#include "rc_util.h"
 
 #include <algorithm>
 #include <atomic>
@@ -123,6 +124,8 @@ struct AchievementProgressIndicator
 };
 } // namespace
 
+using LoginEncryptionKey = std::array<u8, RC_CLIENT_LOGIN_ENCRYPTION_KEY_LENGTH>;
+
 static void ReportError(std::string_view sv);
 template<typename... T>
 static void ReportFmtError(fmt::format_string<T...> fmt, T&&... args);
@@ -144,6 +147,10 @@ static std::string GetLocalImagePath(const std::string_view image_name, int type
 static void DownloadImage(std::string url, std::string cache_filename);
 static void UpdateGlyphRanges();
 
+static LoginEncryptionKey GetLoginEncryptionKey(std::string_view username);
+static TinyString DecryptLoginToken(std::string_view encrypted_token, std::string_view username);
+static TinyString EncryptLoginToken(std::string_view token, std::string_view username);
+
 static bool CreateClient(rc_client_t** client, std::unique_ptr<HTTPDownloader>* http);
 static void DestroyClient(rc_client_t** client, std::unique_ptr<HTTPDownloader>* http);
 static void ClientMessageCallback(const char* message, const rc_client_t* client);
@@ -466,6 +473,65 @@ void Achievements::UpdateGlyphRanges()
   ImGuiManager::SetEmojiFontRange(ImGuiManager::CompactFontRange(sorted_codepoints));
 }
 
+Achievements::LoginEncryptionKey Achievements::GetLoginEncryptionKey(std::string_view username)
+{
+  LoginEncryptionKey ret;
+
+  const int res = rc_client_get_login_encryption_key(ret.data(), username.data(), username.length());
+  if (res != RC_OK)
+  {
+    WARNING_LOG("rc_client_get_login_encryption_key() failed: {}, assuming zero.", res);
+    ret = {};
+  }
+
+  return ret;
+}
+
+TinyString Achievements::EncryptLoginToken(std::string_view token, std::string_view username)
+{
+  TinyString ret;
+  if (token.empty())
+    return ret;
+
+  const size_t len = rc_client_get_encrypted_login_length(token.length());
+  DynamicHeapArray<u8> encrypted(len);
+  const int res = rc_client_encrypt_login(GetLoginEncryptionKey(username).data(), token.data(), token.length(),
+                                          encrypted.data(), len);
+  if (res != RC_OK)
+  {
+    ERROR_LOG("rc_client_encrypt_login() failed: {}", res);
+    return ret;
+  }
+
+  ret.append_hex(encrypted.data(), encrypted.size());
+  return ret;
+}
+
+TinyString Achievements::DecryptLoginToken(std::string_view encrypted_token, std::string_view username)
+{
+  TinyString ret;
+  if (encrypted_token.empty())
+    return ret;
+
+  const std::optional<std::vector<u8>> ciphertext = StringUtil::DecodeHex(encrypted_token);
+  if (!ciphertext.has_value() || ciphertext->size() >= std::numeric_limits<u32>::max())
+    return ret;
+
+  size_t token_length = ciphertext->size();
+  ret.reserve(static_cast<u32>(token_length));
+
+  const int res = rc_client_decrypt_login(GetLoginEncryptionKey(username).data(), ciphertext->data(),
+                                          ciphertext->size(), ret.data(), &token_length);
+  if (res != RC_OK)
+  {
+    ERROR_LOG("rc_client_decrypt_login() failed: {}", res);
+    return ret;
+  }
+
+  ret.set_size(static_cast<u32>(token_length));
+  return ret;
+}
+
 bool Achievements::IsActive()
 {
 #ifdef ENABLE_RAINTEGRATION
@@ -566,8 +632,18 @@ bool Achievements::Initialize()
   if (!username.empty() && !api_token.empty())
   {
     INFO_LOG("Attempting login with user '{}'...", username);
-    s_login_request = rc_client_begin_login_with_token(s_client, username.c_str(), api_token.c_str(),
-                                                       ClientLoginWithTokenCallback, nullptr);
+
+    // If we can't decrypt the token, it was an old config and we need to re-login.
+    if (const TinyString decrypted_api_token = DecryptLoginToken(api_token, username); !decrypted_api_token.empty())
+    {
+      s_login_request = rc_client_begin_login_with_token(s_client, username.c_str(), decrypted_api_token.c_str(),
+                                                         ClientLoginWithTokenCallback, nullptr);
+    }
+    else
+    {
+      WARNING_LOG("Invalid encrypted login token, requesitng a new one.");
+      Host::OnAchievementsLoginRequested(LoginRequestReason::TokenInvalid);
+    }
   }
 
   // Hardcore mode isn't enabled when achievements first starts, if a game is already running.
@@ -1878,7 +1954,7 @@ void Achievements::ClientLoginWithPasswordCallback(int result, const char* error
 
   // Store configuration.
   Host::SetBaseStringSettingValue("Cheevos", "Username", params->username);
-  Host::SetBaseStringSettingValue("Cheevos", "Token", user->token);
+  Host::SetBaseStringSettingValue("Cheevos", "Token", EncryptLoginToken(user->token, params->username));
   Host::SetBaseStringSettingValue("Cheevos", "LoginTimestamp", fmt::format("{}", std::time(nullptr)).c_str());
   Host::CommitBaseSettingChanges();