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Avoid all compiler optimization on embedded apphost hash #110554

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merged 4 commits into from
Mar 29, 2025
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Avoid all compiler optimization on embedded apphost hash #110554

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Avoid all compiler optimization on embedded apphost hash
omajid Dec 9, 2024
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AaronRobinsonMSFT Mar 27, 2025
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AaronRobinsonMSFT Mar 28, 2025
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23 changes: 18 additions & 5 deletions src/native/corehost/corehost.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,19 @@
#define EMBED_HASH_LO_PART_UTF8 "74e592c2fa383d4a3960714caef0c4f2"
#define EMBED_HASH_FULL_UTF8 (EMBED_HASH_HI_PART_UTF8 EMBED_HASH_LO_PART_UTF8) // NUL terminated

// This avoids compiler optimization which cause EMBED_HASH_HI_PART_UTF8 EMBED_HASH_LO_PART_UTF8
// to be placed adjacent causing them to match EMBED_HASH_FULL_UTF8 when searched for replacing.
// See https://github.com/dotnet/runtime/issues/109611 for more details.
static bool compare_memory_nooptimization(volatile const char* a, volatile const char* b, size_t length)
{
for (size_t i = 0; i < length; i++)
{
if (*a++ != *b++)
return false;
}
return true;
}

bool is_exe_enabled_for_execution(pal::string_t* app_dll)
{
constexpr int EMBED_SZ = sizeof(EMBED_HASH_FULL_UTF8) / sizeof(EMBED_HASH_FULL_UTF8[0]);
Expand All @@ -59,10 +72,10 @@ bool is_exe_enabled_for_execution(pal::string_t* app_dll)
return false;
}

std::string binding(&embed[0]);
size_t binding_len = strlen(&embed[0]);

// Check if the path exceeds the max allowed size
if (binding.size() > EMBED_MAX - 1) // -1 for null terminator
if (binding_len > EMBED_MAX - 1) // -1 for null terminator
{
trace::error(_X("The managed DLL bound to this executable is longer than the max allowed length (%d)"), EMBED_MAX - 1);
return false;
Expand All @@ -73,9 +86,9 @@ bool is_exe_enabled_for_execution(pal::string_t* app_dll)
// So use two parts of the string that will be unaffected by the edit.
size_t hi_len = (sizeof(hi_part) / sizeof(hi_part[0])) - 1;
size_t lo_len = (sizeof(lo_part) / sizeof(lo_part[0])) - 1;
if (binding.size() >= (hi_len + lo_len)
&& binding.compare(0, hi_len, &hi_part[0]) == 0
&& binding.compare(hi_len, lo_len, &lo_part[0]) == 0)
if (binding_len >= (hi_len + lo_len)
&& compare_memory_nooptimization(&embed[0], hi_part, hi_len)
&& compare_memory_nooptimization(&embed[hi_len], lo_part, lo_len))
{
trace::error(_X("This executable is not bound to a managed DLL to execute. The binding value is: '%s'"), app_dll->c_str());
return false;
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