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Fix crash when user cancels Windows Hello dialog (nullptr from e.what()) #202

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Merged
Branden Bonaby (bbonaby) merged 1 commit into from
Apr 22, 2026
Merged

Fix crash when user cancels Windows Hello dialog (nullptr from e.what()) #202

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14 changes: 11 additions & 3 deletions src/VbsEnclaveSDK/src/veil_enclave_lib/userboundkey.vtl1.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,14 @@

namespace veil::vtl1::userboundkey
{
// Safe wrapper for e.what() — returns fallback when what() is nullptr
// (common when exceptions cross VTL boundaries)
static const char* safe_what(const std::exception& e) noexcept
{
const char* msg = e.what();
return msg ? msg : "unknown exception";
}

using unique_sessionhandle = wil::unique_any<USER_BOUND_KEY_SESSION_HANDLE, decltype(&::CloseUserBoundKeySession), ::CloseUserBoundKeySession>;

// RAII wrapper for credentials using WIL
Expand Down Expand Up @@ -480,7 +488,7 @@ wil::secure_vector<uint8_t> create_user_bound_key(
catch (const std::exception& e)
{
// Convert exception message to wide string for debug printing
std::string error_msg = e.what();
std::string error_msg = safe_what(e);
std::wstring werror_msg(error_msg.begin(), error_msg.end());
veil::vtl1::vtl0_functions::internal::debug_print((L"ERROR: create_user_bound_key - Exception caught: " + werror_msg).c_str());
throw; // Re-throw the exception
Expand Down Expand Up @@ -676,7 +684,7 @@ std::vector<uint8_t> load_user_bound_key(
catch (const std::exception& e)
{
// Convert exception message to wide string for debug printing
std::string error_msg = e.what();
std::string error_msg = safe_what(e);
std::wstring werror_msg(error_msg.begin(), error_msg.end());
veil::vtl1::vtl0_functions::internal::debug_print((L"ERROR: load_user_bound_key - Exception caught: " + werror_msg).c_str());
throw; // Re-throw the exception
Expand Down Expand Up @@ -719,7 +727,7 @@ std::vector<uint8_t> reseal_user_bound_key(
catch (const std::exception& e)
{
// Convert exception message to wide string for debug printing
std::string error_msg = e.what();
std::string error_msg = safe_what(e);
std::wstring werror_msg(error_msg.begin(), error_msg.end());
veil::vtl1::vtl0_functions::internal::debug_print((L"ERROR: reseal_user_bound_key - Exception caught: " + werror_msg).c_str());
throw; // Re-throw the exception
Expand Down
23 changes: 18 additions & 5 deletions src/VbsEnclaveSDK/src/veil_host_lib/userboundkey.vtl0.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,14 @@
using namespace winrt::Windows::Security::Credentials;
using namespace veil::vtl0::implementation::debug;

// Safe wrapper for e.what() — returns fallback when what() is nullptr
// (common when exceptions cross VTL boundaries)
static const char* safe_what(const std::exception& e) noexcept
{
const char* msg = e.what();
return msg ? msg : "unknown exception";
}

namespace veil::vtl0::userboundkey::implementation
{
// RAII wrapper that stores both the session handle and enclave pointer
Expand Down Expand Up @@ -87,7 +95,8 @@ class unique_sessionhandle
catch (const std::exception& e)
{
std::wstring errorMsg = L"ERROR: Exception during VTL0 session cleanup: ";
errorMsg += std::wstring(e.what(), e.what() + strlen(e.what()));
const char* what_msg = safe_what(e);
errorMsg += std::wstring(what_msg, what_msg + strlen(what_msg));
veil::vtl0::implementation::debug::internal::debug_wprint(errorMsg);
}
catch (...)
Expand Down Expand Up @@ -169,7 +178,8 @@ CreateChallengeCallback(std::shared_ptr<veil::vtl0::userboundkey::implementation
catch (const std::exception& e)
{
std::wstring errorMsg = L"DEBUG: Exception in " + callbackType + L" callback: ";
errorMsg += std::wstring(e.what(), e.what() + strlen(e.what()));
const char* what_msg = safe_what(e);
errorMsg += std::wstring(what_msg, what_msg + strlen(what_msg));
veil::vtl0::implementation::debug::internal::debug_wprint(errorMsg);
throw;
}
Expand Down Expand Up @@ -401,7 +411,8 @@ std::vector<uint8_t> veil_abi::Untrusted::Implementation::userboundkey_get_autho
catch (const std::exception& e)
{
std::wstring errorMsg = L"DEBUG: Exception in userboundkey_get_authorization_context_from_credential: ";
errorMsg += std::wstring(e.what(), e.what() + strlen(e.what()));
const char* what_msg = safe_what(e);
errorMsg += std::wstring(what_msg, what_msg + strlen(what_msg));
veil::vtl0::implementation::debug::internal::debug_wprint(errorMsg);
throw;
}
Expand Down Expand Up @@ -447,7 +458,8 @@ std::vector<uint8_t> veil_abi::Untrusted::Implementation::userboundkey_get_secre
catch (const std::exception& e)
{
std::wstring errorMsg = L"DEBUG: Exception in userboundkey_get_secret_from_credential: ";
errorMsg += std::wstring(e.what(), e.what() + strlen(e.what()));
const char* what_msg = safe_what(e);
errorMsg += std::wstring(what_msg, what_msg + strlen(what_msg));
veil::vtl0::implementation::debug::internal::debug_wprint(errorMsg);
throw;
}
Expand Down Expand Up @@ -493,7 +505,8 @@ void veil_abi::Untrusted::Implementation::userboundkey_delete_credential(uintptr
catch (const std::exception& e)
{
std::wstring errorMsg = L"DEBUG: Exception in userboundkey_delete_credential: ";
errorMsg += std::wstring(e.what(), e.what() + strlen(e.what()));
const char* what_msg = safe_what(e);
errorMsg += std::wstring(what_msg, what_msg + strlen(what_msg));
veil::vtl0::implementation::debug::internal::debug_wprint(errorMsg);
}
catch (...)
Expand Down
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