private bool EnablesControlFlowGuard(BinaryAnalyzerContext context)
{
PEHeader peHeader = context.PE.PEHeaders.PEHeader;
if (((uint)peHeader.DllCharacteristics & IMAGE_DLLCHARACTERISTICS_CONTROLFLOWGUARD) == 0)
{
return false;
}
SafePointer loadConfigRVA = new SafePointer(context.PE.ImageBytes, peHeader.LoadConfigTableDirectory.RelativeVirtualAddress);
if (loadConfigRVA.Address == 0)
{
return false;
}
SafePointer loadConfigVA = context.PE.RVA2VA(loadConfigRVA);
if (context.PE.Is64Bit)
{
ImageLoadConfigDirectory64 loadConfig = new ImageLoadConfigDirectory64(peHeader, loadConfigVA);
Int32 imageDirectorySize = (Int32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.Size);
UInt64 guardCFCheckFunctionPointer = (UInt64)loadConfig.GetField(ImageLoadConfigDirectory64.Fields.GuardCFCheckFunctionPointer);
UInt64 guardCFFunctionTable = (UInt64)loadConfig.GetField(ImageLoadConfigDirectory64.Fields.GuardCFFunctionTable);
UInt32 guardFlags = (UInt32)loadConfig.GetField(ImageLoadConfigDirectory64.Fields.GuardFlags);
if (imageDirectorySize >= IMAGE_LOAD_CONFIG_MINIMUM_SIZE_64 &&
guardCFCheckFunctionPointer != 0 &&
guardCFFunctionTable != 0 &&
(guardFlags & IMAGE_GUARD_CF_CHECKS) == IMAGE_GUARD_CF_CHECKS)
{
return true;
}
}
else
{
ImageLoadConfigDirectory32 loadConfig = new ImageLoadConfigDirectory32(peHeader, loadConfigVA);
Int32 imageDirectorySize = (Int32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.Size);
UInt32 guardCFCheckFunctionPointer = (UInt32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.GuardCFCheckFunctionPointer);
UInt32 guardCFFunctionTable = (UInt32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.GuardCFFunctionTable);
UInt32 guardFlags = (UInt32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.GuardFlags);
if (imageDirectorySize >= IMAGE_LOAD_CONFIG_MINIMUM_SIZE_32 &&
guardCFCheckFunctionPointer != 0 &&
guardCFFunctionTable != 0 &&
(guardFlags & IMAGE_GUARD_CF_CHECKS) == IMAGE_GUARD_CF_CHECKS)
{
return true;
}
}
return false;
}
public void Analyze(BinaryAnalyzerContext context)
{
PEHeader peHeader = context.PE.PEHeaders.PEHeader;
/* IMAGE_DLLCHARACTERISTICS_NO_SEH */
if ((peHeader.DllCharacteristics & DllCharacteristics.NoSeh) == DllCharacteristics.NoSeh)
{
// '{0}' is an x86 binary that does not use SEH, making it an invalid
// target for exploits that attempt to replace SEH jump targets with
// attacker-controlled shellcode.
context.Logger.Log(MessageKind.Pass, context,
RuleUtilities.BuildMessage(context,
RulesResources.EnableSafeSEH_NoSEH_Pass));
return;
}
// This will not raise false positives for non-C and C++ code, because the above
// check for IMAGE_DLLCHARACTERISTICS_NO_SEH excludes things that don't actually
// handle SEH exceptions like .NET ngen'd code.
if (peHeader.LoadConfigTableDirectory.RelativeVirtualAddress == 0)
{
// '{0}' is an x86 binary which does not contain a load configuration table,
// indicating that it does not enable the SafeSEH mitigation. SafeSEH makes
// it more difficult to exploit memory corruption vulnerabilities that can
// overwrite SEH control blocks on the stack, by verifying that the location
// to which a thrown SEH exception would jump is indeed defined as an
// exception handler in the source program (and not shellcode). To resolve
// this issue, supply the /SafeSEH flag on the linker command line. Note
// that you will need to configure your build system to supply this flag for
// x86 builds only, as the /SafeSEH flag is invalid when linking for ARM and x64.
context.Logger.Log(MessageKind.Fail, context,
RuleUtilities.BuildMessage(context,
RulesResources.EnableSafeSEH_NoLoadConfigurationTable_Fail));
return;
}
SafePointer sp = new SafePointer(context.PE.ImageBytes, peHeader.LoadConfigTableDirectory.RelativeVirtualAddress);
SafePointer loadConfigVA = context.PE.RVA2VA(sp);
ImageLoadConfigDirectory32 loadConfig = new ImageLoadConfigDirectory32(peHeader, loadConfigVA);
Int32 seHandlerSize = (Int32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.Size);
if (seHandlerSize < 72)
{
// contains an unexpectedly small load configuration table {size 0}
string seHandlerSizeText = String.Format(RulesResources.EnableSafeSEH_LoadConfigurationIsTooSmall_Fail, seHandlerSize.ToString());
context.Logger.Log(MessageKind.Fail, context,
RuleUtilities.BuildMessage(context,
RulesResources.EnableSafeSEH_Formatted_Fail,
RulesResources.EnableSafeSEH_LoadConfigurationIsTooSmall_Fail,
seHandlerSizeText));
return;
}
UInt32 seHandlerTable = (UInt32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.SEHandlerTable);
UInt32 seHandlerCount = (UInt32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.SEHandlerCount);
if (seHandlerTable == 0 || seHandlerCount == 0)
{
string failureKind = null;
if (seHandlerTable == 0)
{
// has an empty SE handler table in the load configuration table
failureKind = RulesResources.EnableSafeSEH_EmptySEHandlerTable_Fail;
}
else if (seHandlerCount == 0)
{
// has zero SE handlers in the load configuration table
failureKind = RulesResources.EnableSafeSEH_ZeroCountSEHandlers_Fail;
}
// '{0}' is an x86 binary which {1}, indicating that it does not enable the SafeSEH
// mitigation. SafeSEH makes it more difficult to exploit memory corruption
// vulnerabilities that can overwrite SEH control blocks on the stack, by verifying
// that the location to which a thrown SEH exception would jump is indeed defined
// as an exception handler in the source program (and not shellcode). To resolve
// this issue, supply the /SafeSEH flag on the linker command line. Note that you
// will need to configure your build system to supply this flag for x86 builds only,
// as the /SafeSEH flag is invalid when linking for ARM and x64.
context.Logger.Log(MessageKind.Fail, context,
RuleUtilities.BuildMessage(context,
RulesResources.EnableSafeSEH_Formatted_Fail, failureKind));
return;
}
// ''{0}' is an x86 binary that enables SafeSEH, a mitigation that verifies SEH exception
// jump targets are defined as exception handlers in the program (and not shellcode).
context.Logger.Log(MessageKind.Pass, context,
RuleUtilities.BuildMessage(context,
RulesResources.EnableSafeSEH_SafeSEHEnabled_Pass));
}
private bool Validate32BitImage(BinaryAnalyzerContext context)
{
PEHeader peHeader = context.PE.PEHeaders.PEHeader;
SafePointer sp = new SafePointer(context.PE.ImageBytes, peHeader.LoadConfigTableDirectory.RelativeVirtualAddress);
SafePointer loadConfigVA = context.PE.RVA2VA(sp);
ImageLoadConfigDirectory32 loadConfig = new ImageLoadConfigDirectory32(peHeader, loadConfigVA);
UInt32 cookieVA = (UInt32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.SecurityCookie);
UInt32 baseAddress = (UInt32)peHeader.ImageBase;
// we need to find the offset in the file based on the cookie's VA
UInt32 sectionSize, sectionVA = 0;
SectionHeader ish = new SectionHeader();
bool foundCookieSection = false;
foreach (SectionHeader t in context.PE.PEHeaders.SectionHeaders)
{
sectionVA = (UInt32)t.VirtualAddress + baseAddress;
sectionSize = (UInt32)t.VirtualSize;
if ((cookieVA >= sectionVA) &&
(cookieVA < sectionVA + sectionSize))
{
ish = t;
foundCookieSection = true;
break;
}
}
if (!foundCookieSection)
{
LogCouldNotLocateCookie(context);
return false;
}
UInt64 fileCookieOffset = (cookieVA - baseAddress) - (sectionVA - baseAddress) + (UInt32)ish.PointerToRawData;
SafePointer fileCookiePtr = loadConfigVA;
fileCookiePtr.Address = (int)fileCookieOffset;
UInt32 cookie = BitConverter.ToUInt32(fileCookiePtr.GetBytes(8), 0);
if (!StackProtectionUtilities.DefaultCookiesX86.Contains(cookie) && context.PE.Machine == Machine.I386)
{
LogFailure(context, cookie.ToString("x"));
return false;
}
return true;
}
private bool Validate32BitImage(BinaryAnalyzerContext context)
{
PEHeader peHeader = context.PE.PEHeaders.PEHeader;
SafePointer sp = new SafePointer(context.PE.ImageBytes, peHeader.LoadConfigTableDirectory.RelativeVirtualAddress);
SafePointer loadConfigVA = context.PE.RVA2VA(sp);
ImageLoadConfigDirectory32 loadConfig = new ImageLoadConfigDirectory32(peHeader, loadConfigVA);
UInt32 cookieVA = (UInt32)loadConfig.GetField(ImageLoadConfigDirectory32.Fields.SecurityCookie);
UInt32 baseAddress = (UInt32)peHeader.ImageBase;
// we need to find the offset in the file based on the cookie's VA
UInt32 sectionSize, sectionVA = 0;
SectionHeader ish = new SectionHeader();
bool foundCookieSection = false;
foreach (SectionHeader t in context.PE.PEHeaders.SectionHeaders)
{
sectionVA = (UInt32)t.VirtualAddress + baseAddress;
sectionSize = (UInt32)t.VirtualSize;
if ((cookieVA >= sectionVA) &&
(cookieVA < sectionVA + sectionSize))
{
ish = t;
foundCookieSection = true;
break;
}
}
if (!foundCookieSection)
{
// '{0}' is a C or C++binary that enables the stack protection feature but the security cookie could not be located. The binary may be corrupted.
context.Logger.Log(MessageKind.Fail, context,
RuleUtilities.BuildMessage(context,
RulesResources.DoNotModifyStackProtectionCookie_CouldNotLocateCookie_Fail));
return false;
}
UInt64 fileCookieOffset = (cookieVA - baseAddress) - (sectionVA - baseAddress) + (UInt32)ish.PointerToRawData;
SafePointer fileCookiePtr = loadConfigVA;
fileCookiePtr.Address = (int)fileCookieOffset;
UInt32 cookie = BitConverter.ToUInt32(fileCookiePtr.GetBytes(8), 0);
if (!StackProtectionUtilities.DefaultCookiesX86.Contains(cookie) && context.PE.Machine == Machine.I386)
{
// '{0}' is a C or C++ binary that interferes with the stack protector. The
// stack protector (/GS) is a security feature of the compiler which makes
// it more difficult to exploit stack buffer overflow memory corruption
// vulnerabilities. The stack protector relies on a random number, called
// the "security cookie", to detect these buffer overflows. This 'cookie'
// is statically linked with your binary from a Visual C++ library in the
// form of the symbol __security_cookie. On recent Windows versions, the
// loader looks for the magic statically linked value of this cookie, and
// initializes the cookie with a far better source of entropy -- the system's
// secure random number generator -- rather than the limited random number
// generator available early in the C runtime startup code. When this symbol
// is not the default value, the additional entropy is not injected by the
// operating system, reducing the effectiveness of the stack protector. To
// resolve this issue, ensure that your code does not reference or create a
// symbol named __security_cookie or __security_cookie_complement. NOTE:
// the modified cookie value detected was: {1}
context.Logger.Log(MessageKind.Fail, context,
RuleUtilities.BuildMessage(context,
RulesResources.DoNotModifyStackProtectionCookie_Fail, cookie.ToString("x")));
return false;
}
return true;
}
