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rules.c
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rules.c
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/*
SysmonCommon
Copyright (c) Microsoft Corporation
All rights reserved.
MIT License
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the ""Software""), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED *AS IS*, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
//====================================================================
//
// Rules.c
//
// Rule engine for user-mode and kernel-mode
//
//====================================================================
#include "rules.h"
#if defined _WIN64 || defined _WIN32
#ifndef SYSMON_DRIVER
#include "windows.h"
#endif
#elif defined __linux__
#include <stdarg.h>
#include <pthread.h>
#include "linuxTypes.h"
#include "linuxHelpers.h"
#endif
#ifdef __cplusplus
extern "C" {
#endif
#if defined _WIN64 || defined _WIN32
#ifndef ALIGN_DOWN_BY
#define ALIGN_DOWN_BY(length, alignment) \
((ULONG_PTR)(length) & ~(alignment - 1))
#define ALIGN_UP_BY(length, alignment) \
(ALIGN_DOWN_BY(((ULONG_PTR)(length) + alignment - 1), alignment))
#endif // ALIGN_DOWN_BY
#elif defined __linux__
#define MAX_FIELD_VALUE_LEN 512
#define ALIGN_DOWN_BY(length, alignment) \
((uint64_t)(length) & ~((uint64_t)alignment - 1))
#define ALIGN_UP_BY(length, alignment) \
(ALIGN_DOWN_BY(((uint64_t)(length) + alignment - 1), (uint64_t)alignment))
#endif
//
// Current rule set
//
PRULE_SET g_blob = NULL;
#define SYSMON_MAX_ULONG 0xffffffffUL
//
// Critical section to access g_blog
//
#ifdef SYSMON_DRIVER
#define D_ASSERT(_x)
#define DBG_MODE(...)
#define _tprintf(...)
ERESOURCE g_Lock;
#define INIT_CRIT() ExInitializeResourceLite( &g_Lock )
#define ENTER_CRIT_READ() { KeEnterCriticalRegion(); ExAcquireResourceSharedLite( &g_Lock, TRUE ); }
#define LEAVE_CRIT_READ() { ExReleaseResourceLite( &g_Lock ); KeLeaveCriticalRegion(); }
#define ENTER_CRIT_WRITE() { KeEnterCriticalRegion(); ExAcquireResourceExclusiveLite( &g_Lock, TRUE ); }
#define LEAVE_CRIT_WRITE() { ExReleaseResourceLite( &g_Lock ); KeLeaveCriticalRegion(); }
extern PVOID
SysmonAllocate(
POOL_TYPE PoolType,
ULONG Size,
ULONG Tag
);
#define ALLOC(_x) SysmonAllocate( PagedPool, (ULONG) _x, 'R' )
#define FREE(_x) ExFreePool( _x )
// The driver doesn't need to print errors, replacing by a noop.
#define PrintErrorEx(...)
#else
CRITICAL_SECTION g_crit;
#if defined _WIN64 || defined _WIN32
BOOLEAN g_readWrite = FALSE;
SRWLOCK g_rwLock;
#define RW_PROTO(_r, _n, _p) \
typedef _r (WINAPI * t ## _n)## _p ##; \
t ## _n l_ ## _n = NULL
#define PROTO_RESOLVE( _h, _n ) \
l_ ## _n = (t ## _n) GetProcAddress( _h, #_n );
RW_PROTO( VOID, InitializeSRWLock, ( PSRWLOCK SRWLock ) );
RW_PROTO( VOID, AcquireSRWLockExclusive, ( PSRWLOCK SRWLock ) );
RW_PROTO( VOID, AcquireSRWLockShared, ( PSRWLOCK SRWLock ) );
RW_PROTO( VOID, ReleaseSRWLockExclusive, ( PSRWLOCK SRWLock ) );
RW_PROTO( VOID, ReleaseSRWLockShared, ( PSRWLOCK SRWLock ) );
//--------------------------------------------------------------------
//
// InitializeLock
//
// Try to use RW lock for better performance, default to critical
// sections
//
//--------------------------------------------------------------------
VOID
InitializeLock(
VOID
)
{
HMODULE hKernel = GetModuleHandle( _T("kernel32.dll") );
if( hKernel != NULL ) {
PROTO_RESOLVE( hKernel, InitializeSRWLock );
PROTO_RESOLVE( hKernel, AcquireSRWLockExclusive );
PROTO_RESOLVE( hKernel, AcquireSRWLockShared );
PROTO_RESOLVE( hKernel, ReleaseSRWLockExclusive );
PROTO_RESOLVE( hKernel, ReleaseSRWLockShared );
}
if( l_InitializeSRWLock != NULL &&
l_AcquireSRWLockExclusive != NULL &&
l_AcquireSRWLockShared != NULL &&
l_ReleaseSRWLockExclusive != NULL &&
l_ReleaseSRWLockShared != NULL ) {
g_readWrite = TRUE;
l_InitializeSRWLock( &g_rwLock );
} else {
InitializeCriticalSection( &g_crit );
}
}
#define INIT_CRIT() InitializeLock()
#define ENTER_CRIT_READ() { if( g_readWrite ) { l_AcquireSRWLockShared( &g_rwLock ); } else { EnterCriticalSection( &g_crit ); } }
#define LEAVE_CRIT_READ() { if( g_readWrite ) { l_ReleaseSRWLockShared( &g_rwLock ); } else { LeaveCriticalSection( &g_crit ); } }
#define ENTER_CRIT_WRITE() { if( g_readWrite ) { l_AcquireSRWLockExclusive( &g_rwLock ); } else { EnterCriticalSection( &g_crit ); } }
#define LEAVE_CRIT_WRITE() { if( g_readWrite ) { l_ReleaseSRWLockExclusive( &g_rwLock ); } else { LeaveCriticalSection( &g_crit ); } }
#elif defined __linux__
VOID
InitializeLock(
VOID
)
{
InitializeCriticalSection( &g_crit );
}
#define INIT_CRIT() InitializeLock()
#define ENTER_CRIT_READ() { EnterCriticalSection( &g_crit ); }
#define LEAVE_CRIT_READ() { LeaveCriticalSection( &g_crit ); }
#define ENTER_CRIT_WRITE() { EnterCriticalSection( &g_crit ); }
#define LEAVE_CRIT_WRITE() { LeaveCriticalSection( &g_crit ); }
LONG
InterlockedIncrement(
LONG volatile *Addend
)
{
(*Addend)++;
return *Addend;
}
LONG
InterlockedDecrement(
LONG volatile *Addend
)
{
(*Addend)--;
return *Addend;
}
void PrintErrorEx( PTCHAR ID, DWORD ErrorCode, PTCHAR Format, ... )
{
va_list args;
va_start( args, Format );
fprintf(stderr, "Sysmon error. ID:'%s', ERROR:%d\n", ID, ErrorCode);
vfprintf(stderr, Format, args);
}
#define min(a,b) (((a) < (b)) ? (a) : (b))
#endif
#define ALLOC(_x) malloc( _x )
#define FREE(_x) free( _x )
#endif
// WIDECHAR simplifies using a WCHAR character between Windows and Linux.
#if defined _WIN64 || defined _WIN32
#define WIDECHAR(x) L##x
#elif defined __linux__
#define WIDECHAR(x) (WCHAR)x
#endif
//----------------------------------------------------------------------
//
// NextItem
//
// An helper function to iterate a string list using Delim.
//
// Context tracks the next item in the list.
// Delim is the delimiter WCHAR between elements in the list.
// Token is the current item tracked.
// TokenCchSize is the SIZE in character of the current position.
//
// Returns TRUE if an entry is available, false if done.
//
//----------------------------------------------------------------------
BOOLEAN NextItem( _Inout_ PCWSTR *Context, _In_ WCHAR Delim, _Out_ PCWSTR *Token, _Out_ PSIZE_T TokenCchSize ) {
PCWSTR start, end;
start = *Context;
end = start;
// Indicates the end of the iteration.
if( start == NULL ) {
return FALSE;
}
// Iterate to the next entry or the end.
while( *end && *end != Delim ) {
end++;
}
// Fill information.
*TokenCchSize = end - start;
*Token = start;
// If the end was not \0 WCHAR, put context on the next WCHAR.
// Else set it to NULL to end during the next iteratior.
if( *end ) {
*Context = end + 1;
} else {
*Context = NULL;
}
return TRUE;
}
//----------------------------------------------------------------------
//
// FindSubString
//
// str is the string which is checked.
// sub is the string being looked for in str. It was lowered when loading
// the rule data.
//
//----------------------------------------------------------------------
PCWSTR FindSubString( _In_ PCWSTR str, _In_ PCWSTR sub, _In_ SIZE_T subCchMax )
{
PCWSTR str1, str2, subMax = NULL;
PCWSTR pos = str;
WCHAR c1, c2;
if( subCchMax != 0 ) {
subMax = sub + subCchMax;
}
while( *pos ) {
str1 = pos;
str2 = sub;
while( TRUE ) {
c1 = *str1;
c2 = *str2;
// Matched the whole sub string.
if( !c2 ) {
return pos;
}
// Ended iteration on str without a full match.
if( !c1 ) {
return NULL;
}
if( TOWLOWER( c1 ) != c2 ) {
break;
}
++str1;
++str2;
// Matched the whole string at that point.
if( str2 == subMax ) {
return pos;
}
}
++pos;
}
return NULL;
}
//--------------------------------------------------------------------
//
// IsVersionGreater
//
// Simple version comparison without using floating point for the kernel
//
//--------------------------------------------------------------------
BOOLEAN
IsVersionGreater(
ULONG Version,
ULONG Major,
ULONG Minor
)
{
if( V_MAJOR( Version ) < Major ) {
return FALSE;
}
if( V_MAJOR(Version) == Major &&
V_MINOR(Version) <= Minor ) {
return FALSE;
}
return TRUE;
}
//--------------------------------------------------------------------
//
// IsVersionGreaterFromContext
//
// Similar to IsVersionGreater but take RULE_CONTEXT as input.
//
//--------------------------------------------------------------------
BOOLEAN
IsVersionGreaterFromContext(
_In_ PRULE_CONTEXT Context,
_In_ ULONG Major,
_In_ ULONG Minor
)
{
PRULE_REG ruleBase = (PRULE_REG)Context->Current->Rules;
return IsVersionGreater( ruleBase->Version, Major, Minor );
}
//--------------------------------------------------------------------
//
// InitializeRules
//
// Initialize the rule engine
//
//--------------------------------------------------------------------
BOOLEAN
InitializeRules(
VOID
)
{
static BOOLEAN wasInitialized = FALSE;
if( !wasInitialized ) {
INIT_CRIT();
wasInitialized = TRUE;
}
return TRUE;
}
//--------------------------------------------------------------------
//
// GetBlobReference
//
// Get a refrence to the current ruleset, increase the reference count
//
//--------------------------------------------------------------------
PRULE_SET
GetBlobReference(
VOID
)
{
PRULE_SET ret = NULL;
LONG value;
ENTER_CRIT_READ();
if( g_blob != NULL ) {
ret = g_blob;
value = InterlockedIncrement( &ret->ReferenceCount );
//
// Unlikely to happen
//
if( value < 0 ) {
InterlockedDecrement( &ret->ReferenceCount );
ret = NULL;
D_ASSERT( !"Reference count bug in the rule engine" );
}
}
LEAVE_CRIT_READ();
return ret;
}
//--------------------------------------------------------------------
//
// CleanupQuickAccessTable
//
// Clean-up a fully or half-initialized table.
//
//--------------------------------------------------------------------
VOID
CleanupQuickAccessTable(
_In_ PRULE_INDEX_TABLE IndexingTable
)
{
ULONG i;
if( IndexingTable == NULL ) {
return;
}
for( i = 0; i < _countof( IndexingTable->Entries ); i++ ) {
FREE( IndexingTable->Entries[i].Events );
}
FREE( IndexingTable );
}
//--------------------------------------------------------------------
//
// ReleaseBlobReference
//
// Release reference to a rule set, free it if needed
//
//--------------------------------------------------------------------
VOID
ReleaseBlobReference(
_In_ PRULE_SET RuleSet
)
{
BOOLEAN release = FALSE;
LONG decr;
if (NULL != RuleSet) {
ENTER_CRIT_READ();
decr = InterlockedDecrement( &RuleSet->ReferenceCount );
if( decr == 0 ) {
release = TRUE;
}
LEAVE_CRIT_READ();
D_ASSERT( decr >= 0 );
//
// Free the rule set as needed
//
if( release ) {
CleanupQuickAccessTable( RuleSet->IndexingTable );
#if !defined(SYSMON_PUBLIC)
CleanupQuickAccessTable( RuleSet->ShadowIndexingTable );
#endif
FREE( RuleSet->Rules );
FREE( RuleSet );
}
}
}
//--------------------------------------------------------------------
//
// GetIndexFromEventId
//
// Transform the event id to an index on the quick access table.
// Returns -1 if the event id is not meant for the target table.
//
//--------------------------------------------------------------------
LONG
GetIndexFromEventId(
_In_ ULONG EventId,
_In_ BOOLEAN Internal
)
{
LONG ret = -1;
ULONG highestMatchingId;
//
// For rule types like Registry and Pipe, we need to find highest matching rule
//
highestMatchingId = EventId;
while( highestMatchingId+1 < AllEventsCount &&
AllEvents[highestMatchingId+1]->RuleName != NULL &&
!_tcsicmp( AllEvents[EventId]->RuleName, AllEvents[highestMatchingId+1]->RuleName ) ) {
highestMatchingId++;
}
EventId = highestMatchingId;
#if !defined(SYSMON_PUBLIC)
BOOLEAN isInternal;
isInternal = ( ( EventId & INTERNAL_EVENT_MASK ) != 0 );
if( isInternal != Internal ) {
ret = -1;
} else {
ret = (LONG)( EventId & ~INTERNAL_EVENT_MASK );
}
#else
//
// Public version does not need any change
//
D_ASSERT( Internal == FALSE );
Internal;
ret = (LONG)EventId;
#endif
if( ret == 255 ) {
ret = 0;
}
D_ASSERT( ret < 255 );
return ret;
}
//--------------------------------------------------------------------
//
// GetIndexAndTableFromEventId
//
// Transform the event id to an index on the quick access table.
// Returns -1 if the event id is not meant for the target table.
//
// This function also set the target indexing table
//
//--------------------------------------------------------------------
LONG
GetIndexAndTableFromEventId(
_In_ PRULE_CONTEXT Context,
_In_ ULONG EventId,
_Out_ PRULE_INDEX_TABLE* IndexingTable
)
{
LONG curId;
*IndexingTable = NULL;
curId = GetIndexFromEventId( EventId, FALSE );
if( curId >= 0 ) {
*IndexingTable = Context->Current->IndexingTable;
}
#if !defined(SYSMON_PUBLIC)
else {
curId = GetIndexFromEventId( EventId, TRUE );
if( curId >= 0 ) {
*IndexingTable = Context->Current->ShadowIndexingTable;
}
}
#endif
return curId;
}
//--------------------------------------------------------------------
// LowerRuleFilter
//
// All rule filters are case insensitive, lower the rule data by default
// to make matching faster in many conditions.
//
//--------------------------------------------------------------------
VOID LowerRuleFilter(_In_ PRULE_FILTER ruleFilter)
{
PWCHAR pos;
ULONG i;
for( i = 0; i < ruleFilter->DataSize; i += sizeof(WCHAR) ) {
pos = &((PWCHAR)ruleFilter->Data)[i/sizeof(WCHAR)];
*pos = TOWLOWER(*pos);
}
}
//--------------------------------------------------------------------
//
// BackwardFillEventList
//
// Add entries at the back of the event list based on the event count.
// Simplifies the logic on filling the event rule filter list.
//
//--------------------------------------------------------------------
BOOLEAN
BackwardFillEventList(
_In_ PRULE_CONTEXT Context,
_In_ PRULE_INDEX_TABLE Table,
_In_ BOOLEAN Internal,
_In_ PUSHORT EventCount,
_In_ RuleDefaultType DefaultFilter
)
{
LONG curId;
USHORT pos;
PRULE_EVENT ruleEvent;
for( ruleEvent = NextRuleEvent( Context, NULL );
ruleEvent != NULL;
ruleEvent = NextRuleEvent( Context, ruleEvent ) ) {
curId = GetIndexFromEventId( ruleEvent->EventId, Internal );
if( curId < 0 || ruleEvent->RuleDefault != DefaultFilter ) {
continue;
}
// The counter should never underflow, still check for it.
if( EventCount[curId] == 0 ) {
PrintErrorEx( _T("RuleEngine"), ERROR_INVALID_DATA, _T("Invalid data in rules") );
return FALSE;
}
pos = --EventCount[curId];
Table->Entries[curId].Events[pos] = ruleEvent;
}
return TRUE;
}
//--------------------------------------------------------------------
//
// ComputeQuickAccessTables
//
// Compute a quick access table from the blob so rules can be processed
// as fast as possible without going through all entries.
//
//--------------------------------------------------------------------
BOOLEAN
ComputeQuickAccessTables(
_In_ PRULE_SET RuleSet,
_In_ BOOLEAN Internal,
_Out_ PRULE_INDEX_TABLE* IndexingTable,
_In_ BOOLEAN Transform
)
{
RULE_CONTEXT customContext;
PRULE_EVENT ruleEvent;
PRULE_FILTER ruleFilter;
LONG curId;
ULONG i, allocSize;
PRULE_INDEX_TABLE table;
PRULE_EVENT* events;
RULE_REG ruleReg;
RULE_REG_EXT ruleRegExt;
USHORT eventCount[SYSMON_MAX_EVENT_ID + 1] = {0,};
*IndexingTable = NULL;
customContext.Current = RuleSet;
//
// Check version is correct
//
if( !GetRuleRegInformation( &customContext, &ruleReg ) ||
ruleReg.RuleCount == 0 ) {
PrintErrorEx( _T("RuleEngine"), ERROR_INVALID_DATA, _T("Invalid configuration") );
return FALSE;
}
if( !IsCompatibleBinaryVersion( ruleReg.Version ) ) {
if( IsVersionGreater( ruleReg.Version, 1, 0 ) && GetRuleRegExtInformation( &customContext, &ruleRegExt ) ) {
PrintErrorEx( _T("RuleEngine"), 0, _T("Registry rule version %.2f (binary %.2f) is incompatible with Sysmon rule")
_T(" version %.2f (binary %.2f). ")
_T("Please rebuild your manifest with Sysmon schema %.2f."),
TO_DOUBLE( ruleRegExt.SchemaVersion ),
TO_DOUBLE( ruleReg.Version ),
TO_DOUBLE( ConfigurationVersion ),
TO_DOUBLE( BinaryVersion ),
TO_DOUBLE( ConfigurationVersion ) );
} else {
PrintErrorEx( _T("RuleEngine"), 0, _T("Registry rule version %.2f is incompatible with Sysmon rule version %.2f. ")
_T("Please rebuild your manifest with Sysmon schema %.2f."),
TO_DOUBLE( ruleReg.Version ),
TO_DOUBLE( BinaryVersion ),
TO_DOUBLE( ConfigurationVersion ) );
}
return FALSE;
}
table = ALLOC( sizeof( *table ) );
if( table == NULL ) {
PrintErrorEx( _T("RuleEngine"), ERROR_OUTOFMEMORY, _T("Failed to allocate memory") );
return FALSE;
}
memset( table, 0, sizeof( *table ) );
// Check rules are valid, count number of events per type and apply transformation if needed.
for( ruleEvent = NextRuleEvent( &customContext, NULL );
ruleEvent != NULL;
ruleEvent = NextRuleEvent( &customContext, ruleEvent ) ) {
curId = GetIndexFromEventId( ruleEvent->EventId, Internal );
if( curId < 0 ) {
continue;
}
// Check rules default are valid too
if( curId > SYSMON_MAX_EVENT_ID ) {
PrintErrorEx( _T("RuleEngine"), ERROR_INVALID_DATA, _T("Invalid event id in rules") );
goto failed;
}
if( ruleEvent->RuleDefault != Rule_include && ruleEvent->RuleDefault != Rule_exclude ) {
PrintErrorEx( _T("RuleEngine"), ERROR_INVALID_DATA, _T("Invalid data in rules") );
goto failed;
}
// Check if the value will overflow now or on allocation next.
if( eventCount[curId] >= 0xFFFE ) {
PrintErrorEx( _T("RuleEngine"), ERROR_INVALID_DATA, _T("Invalid event count in rules") );
goto failed;
}
eventCount[curId]++;
if( !Transform ) {
continue;
}
for( ruleFilter = NextRuleFilter( &customContext, ruleEvent, NULL );
ruleFilter != NULL;
ruleFilter = NextRuleFilter( &customContext, ruleEvent, ruleFilter ) ) {
LowerRuleFilter( ruleFilter );
#if defined _WIN64 || defined _WIN32
// Add the Filter_Environment tag so expansion is done only if needed.
if( wcschr( (PWCHAR)ruleFilter->Data, WIDECHAR( '%' ) ) != NULL ) {
ruleFilter->FilterType |= Filter_Environment;
}
#endif
}
}
// Allocate the list for each event id.
for( i = 0; i < _countof( eventCount ); i++ ) {
// All events needed and a NULL pointer at the end.
allocSize = ( eventCount[i] + 1 ) * sizeof( PVOID );
if( allocSize == 0 ) {
continue;
}
events = ALLOC( allocSize );
if( events == NULL ) {
PrintErrorEx( _T("RuleEngine"), ERROR_OUTOFMEMORY, _T("Failed to allocate memory") );
goto failed;
}
memset( events, 0, allocSize );
table->Entries[i].Events = events;
}
// Add default exclude to the back first, then include.
if( !BackwardFillEventList( &customContext, table, Internal, eventCount, Rule_exclude ) ||
!BackwardFillEventList( &customContext, table, Internal, eventCount, Rule_include ) ) {
goto failed;
}
// All events should have been added, check in debug mode that eventCount is zero.
for( i = 0; i < _countof( eventCount ); i++ ) {
D_ASSERT( eventCount[i] == 0 );
}
*IndexingTable = table;
return TRUE;
failed:
CleanupQuickAccessTable( table );
return FALSE;
}
//--------------------------------------------------------------------
//
// SetRuleBlob
//
// Set the current rules to apply and compute the quick access tables.
//
// The Transform parameter indicates if the rule data should be
// modified for quick matching. It is expected to be TRUE when rules
// are loaded in the service or driver.
//
//--------------------------------------------------------------------
BOOLEAN
SetRuleBlob(
_In_ PVOID Rules,
_In_ ULONG RulesSize,
_In_ BOOLEAN Transform
)
{
PRULE_SET newSet = NULL, oldSet;
// The Sysmon driver should always do transformation.
#if defined( SYSMON_DRIVER )
D_ASSERT( Transform == TRUE );
#endif
if( Rules != NULL && RulesSize != 0 ) {
newSet = (PRULE_SET) ALLOC( sizeof(*newSet) );
if( newSet == NULL ) {
PrintErrorEx( _T("RuleEngine"), ERROR_OUTOFMEMORY, _T("Failed to allocate memory") );
return FALSE;
}
newSet->Version = 1;
newSet->Rules = Rules;
newSet->RulesSize = RulesSize;
newSet->ReferenceCount = 1;
if( !ComputeQuickAccessTables( newSet, FALSE, &newSet->IndexingTable, Transform ) ) {
FREE( newSet );
return FALSE;
}
#if !defined(SYSMON_PUBLIC)
if( !ComputeQuickAccessTables( newSet, TRUE, &newSet->ShadowIndexingTable, Transform ) ) {
CleanupQuickAccessTable( newSet->IndexingTable );
FREE( newSet );
return FALSE;
}
#endif
}
ENTER_CRIT_WRITE();
oldSet = g_blob;
g_blob = newSet;
if( oldSet != NULL && newSet != NULL ) {
newSet->Version = oldSet->Version + 1;
}
LEAVE_CRIT_WRITE();
//
// Decrease reference count on the old set
//
if( oldSet != NULL ) {
ReleaseBlobReference( oldSet );
}
return TRUE;
}
//--------------------------------------------------------------------
//
// InitializeRuleContext
//
// Initialize the context used to keep state
//
//--------------------------------------------------------------------
BOOLEAN
InitializeRuleContext(
_Out_ PRULE_CONTEXT Context
)
{
PRULE_SET ruleSet;
memset( Context, 0, sizeof( *Context ) );
ruleSet = GetBlobReference();
if( ruleSet == NULL ) {
return FALSE;
}
Context->Current = ruleSet;
return TRUE;
}
//--------------------------------------------------------------------
//
// ReleaseRuleContext
//
// Released an initialized context
//
//--------------------------------------------------------------------
VOID
ReleaseRuleContext(
_In_ PRULE_CONTEXT Context
)
{
ReleaseBlobReference( Context->Current );
Context->Current = NULL;
}
//--------------------------------------------------------------------
//
// GetRuleVersion
//
// Get the current rule version
//
//--------------------------------------------------------------------
ULONG
GetRuleVersion(
VOID
)
{
ULONG ret = 0;
RULE_CONTEXT ctx;
if( InitializeRuleContext( &ctx ) ) {
ret = GET_RULECTX_VERSION( &ctx );
ReleaseRuleContext( &ctx );
}
return ret;
}
//--------------------------------------------------------------------
//
// IsValidPointer
//
// Verify a pointer is within the rule bounds
//
//--------------------------------------------------------------------
BOOLEAN
IsValidPointer(
_In_ PRULE_CONTEXT Context,
_In_ PVOID ptr
)
{
PUCHAR start = (PUCHAR)Context->Current->Rules;
PUCHAR end = start + Context->Current->RulesSize;
if( (PUCHAR)ptr < start || (PUCHAR)ptr >= end ) {
return FALSE;