[CMAKE]
[reactos.git] / ntoskrnl / se / semgr.c
index 8ed056b..406003b 100644 (file)
 
 PSE_EXPORTS SeExports = NULL;
 SE_EXPORTS SepExports;
+ULONG SidInTokenCalls = 0;
 
 extern ULONG ExpInitializationPhase;
 extern ERESOURCE SepSubjectContextLock;
 
 /* PRIVATE FUNCTIONS **********************************************************/
 
-static BOOLEAN INIT_FUNCTION
+static BOOLEAN
+INIT_FUNCTION
 SepInitExports(VOID)
 {
     SepExports.SeCreateTokenPrivilege = SeCreateTokenPrivilege;
@@ -118,6 +120,7 @@ NTAPI
 SepInitializationPhase1(VOID)
 {
     NTSTATUS Status;
+
     PAGED_CODE();
 
     /* Insert the system token into the tree */
@@ -279,8 +282,6 @@ SeDefaultObjectMethod(IN PVOID Object,
     return STATUS_SUCCESS;
 }
 
-ULONG SidInTokenCalls = 0;
-
 static BOOLEAN
 SepSidInToken(PACCESS_TOKEN _Token,
               PSID Sid)
@@ -292,7 +293,7 @@ SepSidInToken(PACCESS_TOKEN _Token,
 
     SidInTokenCalls++;
     if (!(SidInTokenCalls % 10000)) DPRINT1("SidInToken Calls: %d\n", SidInTokenCalls);
-    
+
     if (Token->UserAndGroupCount == 0)
     {
         return FALSE;
@@ -314,8 +315,34 @@ SepSidInToken(PACCESS_TOKEN _Token,
     return FALSE;
 }
 
+static BOOLEAN
+SepTokenIsOwner(PACCESS_TOKEN Token,
+                PSECURITY_DESCRIPTOR SecurityDescriptor)
+{
+    NTSTATUS Status;
+    PSID Sid = NULL;
+    BOOLEAN Defaulted;
+
+    Status = RtlGetOwnerSecurityDescriptor(SecurityDescriptor,
+                                           &Sid,
+                                           &Defaulted);
+    if (!NT_SUCCESS(Status))
+    {
+        DPRINT1("RtlGetOwnerSecurityDescriptor() failed (Status %lx)\n", Status);
+        return FALSE;
+    }
 
-VOID NTAPI
+    if (Sid == NULL)
+    {
+        DPRINT1("Owner Sid is NULL\n");
+        return FALSE;
+    }
+
+    return SepSidInToken(Token, Sid);
+}
+
+VOID
+NTAPI
 SeQuerySecurityAccessMask(IN SECURITY_INFORMATION SecurityInformation,
                           OUT PACCESS_MASK DesiredAccess)
 {
@@ -326,13 +353,15 @@ SeQuerySecurityAccessMask(IN SECURITY_INFORMATION SecurityInformation,
     {
         *DesiredAccess |= READ_CONTROL;
     }
+
     if (SecurityInformation & SACL_SECURITY_INFORMATION)
     {
         *DesiredAccess |= ACCESS_SYSTEM_SECURITY;
     }
 }
 
-VOID NTAPI
+VOID
+NTAPI
 SeSetSecurityAccessMask(IN SECURITY_INFORMATION SecurityInformation,
                         OUT PACCESS_MASK DesiredAccess)
 {
@@ -342,31 +371,40 @@ SeSetSecurityAccessMask(IN SECURITY_INFORMATION SecurityInformation,
     {
         *DesiredAccess |= WRITE_OWNER;
     }
+
     if (SecurityInformation & DACL_SECURITY_INFORMATION)
     {
         *DesiredAccess |= WRITE_DAC;
     }
+
     if (SecurityInformation & SACL_SECURITY_INFORMATION)
     {
         *DesiredAccess |= ACCESS_SYSTEM_SECURITY;
     }
 }
 
+
+#define OLD_ACCESS_CHECK
+
 BOOLEAN NTAPI
 SepAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
                IN PSECURITY_SUBJECT_CONTEXT SubjectSecurityContext,
-               IN BOOLEAN SubjectContextLocked,
                IN ACCESS_MASK DesiredAccess,
                IN ACCESS_MASK PreviouslyGrantedAccess,
                OUT PPRIVILEGE_SET* Privileges,
                IN PGENERIC_MAPPING GenericMapping,
                IN KPROCESSOR_MODE AccessMode,
                OUT PACCESS_MASK GrantedAccess,
-               OUT PNTSTATUS AccessStatus,
-               SECURITY_IMPERSONATION_LEVEL LowestImpersonationLevel)
+               OUT PNTSTATUS AccessStatus)
 {
     LUID_AND_ATTRIBUTES Privilege;
+#ifdef OLD_ACCESS_CHECK
     ACCESS_MASK CurrentAccess, AccessMask;
+#endif
+    ACCESS_MASK RemainingAccess;
+    ACCESS_MASK TempAccess;
+    ACCESS_MASK TempGrantedAccess = 0;
+    ACCESS_MASK TempDeniedAccess = 0;
     PACCESS_TOKEN Token;
     ULONG i;
     PACL Dacl;
@@ -377,44 +415,6 @@ SepAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
     NTSTATUS Status;
     PAGED_CODE();
 
-    /* Check if this is kernel mode */
-    if (AccessMode == KernelMode)
-    {
-        /* Check if kernel wants everything */
-        if (DesiredAccess & MAXIMUM_ALLOWED)
-        {
-            /* Give it */
-            *GrantedAccess = GenericMapping->GenericAll;
-            *GrantedAccess |= (DesiredAccess &~ MAXIMUM_ALLOWED);
-            *GrantedAccess |= PreviouslyGrantedAccess;
-        }
-        else
-        {
-            /* Give the desired and previous access */
-            *GrantedAccess = DesiredAccess | PreviouslyGrantedAccess;
-        }
-
-        /* Success */
-        *AccessStatus = STATUS_SUCCESS;
-        return TRUE;
-    }
-
-    /* Check if we didn't get an SD */
-    if (!SecurityDescriptor)
-    {
-        /* Automatic failure */
-        *AccessStatus = STATUS_ACCESS_DENIED;
-        return FALSE;
-    }
-
-    /* Check for invalid impersonation */
-    if ((SubjectSecurityContext->ClientToken) &&
-        (SubjectSecurityContext->ImpersonationLevel < LowestImpersonationLevel))
-    {
-        *AccessStatus = STATUS_BAD_IMPERSONATION_LEVEL;
-        return FALSE;
-    }
-
     /* Check for no access desired */
     if (!DesiredAccess)
     {
@@ -433,23 +433,50 @@ SepAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
         return TRUE;
     }
 
-    /* Acquire the lock if needed */
-    if (!SubjectContextLocked) SeLockSubjectContext(SubjectSecurityContext);
-
     /* Map given accesses */
     RtlMapGenericMask(&DesiredAccess, GenericMapping);
     if (PreviouslyGrantedAccess)
         RtlMapGenericMask(&PreviouslyGrantedAccess, GenericMapping);
 
-
-
+#ifdef OLD_ACCESS_CHECK
     CurrentAccess = PreviouslyGrantedAccess;
-
-
+#endif
+    /* Initialize remaining access rights */
+    RemainingAccess = DesiredAccess;
 
     Token = SubjectSecurityContext->ClientToken ?
     SubjectSecurityContext->ClientToken : SubjectSecurityContext->PrimaryToken;
 
+    /* Check for system security access */
+    if (RemainingAccess & ACCESS_SYSTEM_SECURITY)
+    {
+        Privilege.Luid = SeSecurityPrivilege;
+        Privilege.Attributes = SE_PRIVILEGE_ENABLED;
+
+        /* Fail if we do not the SeSecurityPrivilege */
+        if (!SepPrivilegeCheck(Token,
+                               &Privilege,
+                               1,
+                               PRIVILEGE_SET_ALL_NECESSARY,
+                               AccessMode))
+        {
+            *AccessStatus = STATUS_PRIVILEGE_NOT_HELD;
+            return FALSE;
+        }
+
+        /* Adjust access rights */
+        RemainingAccess &= ~ACCESS_SYSTEM_SECURITY;
+        PreviouslyGrantedAccess |= ACCESS_SYSTEM_SECURITY;
+
+        /* Succeed if there are no more rights to grant */
+        if (RemainingAccess == 0)
+        {
+            *GrantedAccess = PreviouslyGrantedAccess;
+            *AccessStatus = STATUS_SUCCESS;
+            return TRUE;
+        }
+    }
+
     /* Get the DACL */
     Status = RtlGetDaclSecurityDescriptor(SecurityDescriptor,
                                           &Present,
@@ -457,23 +484,13 @@ SepAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
                                           &Defaulted);
     if (!NT_SUCCESS(Status))
     {
-        if (SubjectContextLocked == FALSE)
-        {
-            SeUnlockSubjectContext(SubjectSecurityContext);
-        }
-
         *AccessStatus = Status;
         return FALSE;
     }
 
     /* RULE 1: Grant desired access if the object is unprotected */
-    if (Present == TRUE && Dacl == NULL)
+    if (Present == FALSE || Dacl == NULL)
     {
-        if (SubjectContextLocked == FALSE)
-        {
-            SeUnlockSubjectContext(SubjectSecurityContext);
-        }
-
         if (DesiredAccess & MAXIMUM_ALLOWED)
         {
             *GrantedAccess = GenericMapping->GenericAll;
@@ -483,138 +500,197 @@ SepAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
         {
             *GrantedAccess = DesiredAccess | PreviouslyGrantedAccess;
         }
-        
+
         *AccessStatus = STATUS_SUCCESS;
         return TRUE;
     }
 
+#ifdef OLD_ACCESS_CHECK
     CurrentAccess = PreviouslyGrantedAccess;
+#endif
 
     /* RULE 2: Check token for 'take ownership' privilege */
-    Privilege.Luid = SeTakeOwnershipPrivilege;
-    Privilege.Attributes = SE_PRIVILEGE_ENABLED;
-
-    if (SepPrivilegeCheck(Token,
-                          &Privilege,
-                          1,
-                          PRIVILEGE_SET_ALL_NECESSARY,
-                          AccessMode))
-    {
-        CurrentAccess |= WRITE_OWNER;
-        if ((DesiredAccess & ~VALID_INHERIT_FLAGS) == 
-            (CurrentAccess & ~VALID_INHERIT_FLAGS))
+    if (DesiredAccess & WRITE_OWNER)
+    {
+        Privilege.Luid = SeTakeOwnershipPrivilege;
+        Privilege.Attributes = SE_PRIVILEGE_ENABLED;
+
+        if (SepPrivilegeCheck(Token,
+                              &Privilege,
+                              1,
+                              PRIVILEGE_SET_ALL_NECESSARY,
+                              AccessMode))
         {
-            if (SubjectContextLocked == FALSE)
+            /* Adjust access rights */
+            RemainingAccess &= ~WRITE_OWNER;
+            PreviouslyGrantedAccess |= WRITE_OWNER;
+#ifdef OLD_ACCESS_CHECK
+            CurrentAccess |= WRITE_OWNER;
+#endif
+
+            /* Succeed if there are no more rights to grant */
+            if (RemainingAccess == 0)
             {
-                SeUnlockSubjectContext(SubjectSecurityContext);
+                *GrantedAccess = PreviouslyGrantedAccess;
+                *AccessStatus = STATUS_SUCCESS;
+                return TRUE;
             }
-
-            *GrantedAccess = CurrentAccess;
-            *AccessStatus = STATUS_SUCCESS;
-            return TRUE;
         }
     }
 
-    /* RULE 3: Check whether the token is the owner */
-    Status = RtlGetOwnerSecurityDescriptor(SecurityDescriptor,
-                                           &Sid,
-                                           &Defaulted);
-    if (!NT_SUCCESS(Status))
+    /* Deny access if the DACL is empty */
+    if (Dacl->AceCount == 0)
     {
-        DPRINT1("RtlGetOwnerSecurityDescriptor() failed (Status %lx)\n", Status);
-        if (SubjectContextLocked == FALSE)
+        if (RemainingAccess == MAXIMUM_ALLOWED && PreviouslyGrantedAccess != 0)
         {
-            SeUnlockSubjectContext(SubjectSecurityContext);
+            *GrantedAccess = PreviouslyGrantedAccess;
+            *AccessStatus = STATUS_SUCCESS;
+            return TRUE;
+        }
+        else
+        {
+            *GrantedAccess = 0;
+            *AccessStatus = STATUS_ACCESS_DENIED;
+            return FALSE;
         }
+    }
 
-        *AccessStatus = Status;
+    /* Fail if DACL is absent */
+    if (Present == FALSE)
+    {
+        *GrantedAccess = 0;
+        *AccessStatus = STATUS_ACCESS_DENIED;
         return FALSE;
     }
 
-    if (Sid && SepSidInToken(Token, Sid))
+    /* Determine the MAXIMUM_ALLOWED access rights according to the DACL */
+    if (DesiredAccess & MAXIMUM_ALLOWED)
     {
-        CurrentAccess |= (READ_CONTROL | WRITE_DAC);
-        if ((DesiredAccess & ~VALID_INHERIT_FLAGS) == 
-            (CurrentAccess & ~VALID_INHERIT_FLAGS))
+        CurrentAce = (PACE)(Dacl + 1);
+        for (i = 0; i < Dacl->AceCount; i++)
         {
-            if (SubjectContextLocked == FALSE)
+            if (!(CurrentAce->Header.AceFlags & INHERIT_ONLY_ACE))
             {
-                SeUnlockSubjectContext(SubjectSecurityContext);
+                Sid = (PSID)(CurrentAce + 1);
+                if (CurrentAce->Header.AceType == ACCESS_DENIED_ACE_TYPE)
+                {
+                    if (SepSidInToken(Token, Sid))
+                    {
+                        /* Map access rights from the ACE */
+                        TempAccess = CurrentAce->AccessMask;
+                        RtlMapGenericMask(&TempAccess, GenericMapping);
+
+                        /* Deny access rights that have not been granted yet */
+                        TempDeniedAccess |= (TempAccess & ~TempGrantedAccess);
+                    }
+                }
+                else if (CurrentAce->Header.AceType == ACCESS_ALLOWED_ACE_TYPE)
+                {
+                    if (SepSidInToken(Token, Sid))
+                    {
+                        /* Map access rights from the ACE */
+                        TempAccess = CurrentAce->AccessMask;
+                        RtlMapGenericMask(&TempAccess, GenericMapping);
+
+                        /* Grant access rights that have not been denied yet */
+                        TempGrantedAccess |= (TempAccess & ~TempDeniedAccess);
+                    }
+                }
+                else
+                {
+                    DPRINT1("Unsupported ACE type 0x%lx\n", CurrentAce->Header.AceType);
+                }
             }
 
-            *GrantedAccess = CurrentAccess;
-            *AccessStatus = STATUS_SUCCESS;
-            return TRUE;
+            /* Get the next ACE */
+            CurrentAce = (PACE)((ULONG_PTR)CurrentAce + CurrentAce->Header.AceSize);
         }
-    }
 
-    /* Fail if DACL is absent */
-    if (Present == FALSE)
-    {
-        if (SubjectContextLocked == FALSE)
+        /* Fail if some rights have not been granted */
+        RemainingAccess &= ~(MAXIMUM_ALLOWED | TempGrantedAccess);
+        if (RemainingAccess != 0)
         {
-            SeUnlockSubjectContext(SubjectSecurityContext);
+            *GrantedAccess = 0;
+            *AccessStatus = STATUS_ACCESS_DENIED;
+            return FALSE;
         }
 
-        *GrantedAccess = 0;
-        *AccessStatus = STATUS_ACCESS_DENIED;
-        return FALSE;
+        /* Set granted access right and access status */
+        *GrantedAccess = TempGrantedAccess | PreviouslyGrantedAccess;
+        if (*GrantedAccess != 0)
+        {
+            *AccessStatus = STATUS_SUCCESS;
+            return TRUE;
+        }
+        else
+        {
+            *AccessStatus = STATUS_ACCESS_DENIED;
+            return FALSE;
+        }
     }
 
     /* RULE 4: Grant rights according to the DACL */
     CurrentAce = (PACE)(Dacl + 1);
     for (i = 0; i < Dacl->AceCount; i++)
     {
-        Sid = (PSID)(CurrentAce + 1);
-        if (CurrentAce->Header.AceType == ACCESS_DENIED_ACE_TYPE)
+        if (!(CurrentAce->Header.AceFlags & INHERIT_ONLY_ACE))
         {
-            if (SepSidInToken(Token, Sid))
+            Sid = (PSID)(CurrentAce + 1);
+            if (CurrentAce->Header.AceType == ACCESS_DENIED_ACE_TYPE)
             {
-                if (SubjectContextLocked == FALSE)
+                if (SepSidInToken(Token, Sid))
                 {
-                    SeUnlockSubjectContext(SubjectSecurityContext);
+#ifdef OLD_ACCESS_CHECK
+                    *GrantedAccess = 0;
+                    *AccessStatus = STATUS_ACCESS_DENIED;
+                    return FALSE;
+#else
+                    /* Map access rights from the ACE */
+                    TempAccess = CurrentAce->AccessMask;
+                    RtlMapGenericMask(&TempAccess, GenericMapping);
+
+                    /* Leave if a remaining right must be denied */
+                    if (RemainingAccess & TempAccess)
+                        break;
+#endif
                 }
-
-                *GrantedAccess = 0;
-                *AccessStatus = STATUS_ACCESS_DENIED;
-                return FALSE;
             }
-        }
-
-        else if (CurrentAce->Header.AceType == ACCESS_ALLOWED_ACE_TYPE)
-        {
-            if (SepSidInToken(Token, Sid))
+            else if (CurrentAce->Header.AceType == ACCESS_ALLOWED_ACE_TYPE)
             {
-                AccessMask = CurrentAce->AccessMask;
-                RtlMapGenericMask(&AccessMask, GenericMapping);
-                CurrentAccess |= AccessMask;
+                if (SepSidInToken(Token, Sid))
+                {
+#ifdef OLD_ACCESS_CHECK
+                    AccessMask = CurrentAce->AccessMask;
+                    RtlMapGenericMask(&AccessMask, GenericMapping);
+                    CurrentAccess |= AccessMask;
+#else
+                    /* Map access rights from the ACE */
+                    TempAccess = CurrentAce->AccessMask;
+                    RtlMapGenericMask(&TempAccess, GenericMapping);
+
+                    /* Remove granted rights */
+                    RemainingAccess &= ~TempAccess;
+#endif
+                }
+            }
+            else
+            {
+                DPRINT1("Unsupported ACE type 0x%lx\n", CurrentAce->Header.AceType);
             }
         }
-        else
-        {
-            DPRINT1("Unknown Ace type 0x%lx\n", CurrentAce->Header.AceType);
-        }
-        CurrentAce = (PACE)((ULONG_PTR)CurrentAce + CurrentAce->Header.AceSize);
-    }
 
-    if (SubjectContextLocked == FALSE)
-    {
-        SeUnlockSubjectContext(SubjectSecurityContext);
+        /* Get the next ACE */
+        CurrentAce = (PACE)((ULONG_PTR)CurrentAce + CurrentAce->Header.AceSize);
     }
 
+#ifdef OLD_ACCESS_CHECK
     DPRINT("CurrentAccess %08lx\n DesiredAccess %08lx\n",
            CurrentAccess, DesiredAccess);
 
     *GrantedAccess = CurrentAccess & DesiredAccess;
 
-    if (DesiredAccess & MAXIMUM_ALLOWED)
-    {
-        *GrantedAccess = CurrentAccess;
-        *AccessStatus = STATUS_SUCCESS;
-        return TRUE;
-    }
-    else if ((*GrantedAccess & ~VALID_INHERIT_FLAGS) == 
-             (DesiredAccess & ~VALID_INHERIT_FLAGS))
+    if ((*GrantedAccess & ~VALID_INHERIT_FLAGS) == 
+        (DesiredAccess & ~VALID_INHERIT_FLAGS))
     {
         *AccessStatus = STATUS_SUCCESS;
         return TRUE;
@@ -628,14 +704,73 @@ SepAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
         *AccessStatus = STATUS_SUCCESS;
         return TRUE;
     }
+#else
+    DPRINT("DesiredAccess %08lx\nPreviouslyGrantedAccess %08lx\nRemainingAccess %08lx\n",
+           DesiredAccess, PreviouslyGrantedAccess, RemainingAccess);
+
+    /* Fail if some rights have not been granted */
+    if (RemainingAccess != 0)
+    {
+        *GrantedAccess = 0;
+        *AccessStatus = STATUS_ACCESS_DENIED;
+        return FALSE;
+    }
+
+    /* Set granted access rights */
+    *GrantedAccess = DesiredAccess | PreviouslyGrantedAccess;
+
+    DPRINT("GrantedAccess %08lx\n", *GrantedAccess);
+
+    /* Fail if no rights have been granted */
+    if (*GrantedAccess == 0)
+    {
+        *AccessStatus = STATUS_ACCESS_DENIED;
+        return FALSE;
+    }
+
+    *AccessStatus = STATUS_SUCCESS;
+    return TRUE;
+#endif
+}
+
+static PSID
+SepGetSDOwner(IN PSECURITY_DESCRIPTOR _SecurityDescriptor)
+{
+    PISECURITY_DESCRIPTOR SecurityDescriptor = _SecurityDescriptor;
+    PSID Owner;
+
+    if (SecurityDescriptor->Control & SE_SELF_RELATIVE)
+        Owner = (PSID)((ULONG_PTR)SecurityDescriptor->Owner +
+                       (ULONG_PTR)SecurityDescriptor);
+    else
+        Owner = (PSID)SecurityDescriptor->Owner;
+
+    return Owner;
+}
+
+static PSID
+SepGetSDGroup(IN PSECURITY_DESCRIPTOR _SecurityDescriptor)
+{
+    PISECURITY_DESCRIPTOR SecurityDescriptor = _SecurityDescriptor;
+    PSID Group;
+
+    if (SecurityDescriptor->Control & SE_SELF_RELATIVE)
+        Group = (PSID)((ULONG_PTR)SecurityDescriptor->Group +
+                       (ULONG_PTR)SecurityDescriptor);
+    else
+        Group = (PSID)SecurityDescriptor->Group;
+
+    return Group;
 }
 
+
 /* PUBLIC FUNCTIONS ***********************************************************/
 
 /*
  * @implemented
  */
-BOOLEAN NTAPI
+BOOLEAN
+NTAPI
 SeAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
               IN PSECURITY_SUBJECT_CONTEXT SubjectSecurityContext,
               IN BOOLEAN SubjectContextLocked,
@@ -647,18 +782,95 @@ SeAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
               OUT PACCESS_MASK GrantedAccess,
               OUT PNTSTATUS AccessStatus)
 {
-    /* Call the internal function */
-    return SepAccessCheck(SecurityDescriptor,
-                          SubjectSecurityContext,
-                          SubjectContextLocked,
-                          DesiredAccess,
-                          PreviouslyGrantedAccess,
-                          Privileges,
-                          GenericMapping,
-                          AccessMode,
-                          GrantedAccess,
-                          AccessStatus,
-                          SecurityImpersonation);
+    BOOLEAN ret;
+
+    PAGED_CODE();
+
+    /* Check if this is kernel mode */
+    if (AccessMode == KernelMode)
+    {
+        /* Check if kernel wants everything */
+        if (DesiredAccess & MAXIMUM_ALLOWED)
+        {
+            /* Give it */
+            *GrantedAccess = GenericMapping->GenericAll;
+            *GrantedAccess |= (DesiredAccess &~ MAXIMUM_ALLOWED);
+            *GrantedAccess |= PreviouslyGrantedAccess;
+        }
+        else
+        {
+            /* Give the desired and previous access */
+            *GrantedAccess = DesiredAccess | PreviouslyGrantedAccess;
+        }
+
+        /* Success */
+        *AccessStatus = STATUS_SUCCESS;
+        return TRUE;
+    }
+
+    /* Check if we didn't get an SD */
+    if (!SecurityDescriptor)
+    {
+        /* Automatic failure */
+        *AccessStatus = STATUS_ACCESS_DENIED;
+        return FALSE;
+    }
+
+    /* Check for invalid impersonation */
+    if ((SubjectSecurityContext->ClientToken) &&
+        (SubjectSecurityContext->ImpersonationLevel < SecurityImpersonation))
+    {
+        *AccessStatus = STATUS_BAD_IMPERSONATION_LEVEL;
+        return FALSE;
+    }
+
+    /* Acquire the lock if needed */
+    if (!SubjectContextLocked)
+        SeLockSubjectContext(SubjectSecurityContext);
+
+    /* Check if the token is the owner and grant WRITE_DAC and READ_CONTROL rights */
+    if (DesiredAccess & (WRITE_DAC | READ_CONTROL | MAXIMUM_ALLOWED))
+    {
+         PACCESS_TOKEN Token = SubjectSecurityContext->ClientToken ?
+             SubjectSecurityContext->ClientToken : SubjectSecurityContext->PrimaryToken;
+
+        if (SepTokenIsOwner(Token,
+                            SecurityDescriptor))
+        {
+            if (DesiredAccess & MAXIMUM_ALLOWED)
+                PreviouslyGrantedAccess |= (WRITE_DAC | READ_CONTROL);
+            else
+                PreviouslyGrantedAccess |= (DesiredAccess & (WRITE_DAC | READ_CONTROL));
+
+            DesiredAccess &= ~(WRITE_DAC | READ_CONTROL);
+        }
+    }
+
+    if (DesiredAccess == 0)
+    {
+        *GrantedAccess = PreviouslyGrantedAccess;
+        *AccessStatus = STATUS_SUCCESS;
+        ret = TRUE;
+    }
+    else
+    {
+        /* Call the internal function */
+        ret = SepAccessCheck(SecurityDescriptor,
+                             SubjectSecurityContext,
+                             DesiredAccess,
+                             PreviouslyGrantedAccess,
+                             Privileges,
+                             GenericMapping,
+                             AccessMode,
+                             GrantedAccess,
+                             AccessStatus);
+    }
+
+    /* Release the lock if needed */
+    if (!SubjectContextLocked)
+        SeUnlockSubjectContext(SubjectSecurityContext);
+
+    return ret;
 }
 
 /* SYSTEM CALLS ***************************************************************/
@@ -677,8 +889,10 @@ NtAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
               OUT PACCESS_MASK GrantedAccess,
               OUT PNTSTATUS AccessStatus)
 {
+    PSECURITY_DESCRIPTOR CapturedSecurityDescriptor = NULL;
     SECURITY_SUBJECT_CONTEXT SubjectSecurityContext;
     KPROCESSOR_MODE PreviousMode = ExGetPreviousMode();
+    ACCESS_MASK PreviouslyGrantedAccess = 0;
     PTOKEN Token;
     NTSTATUS Status;
     PAGED_CODE();
@@ -704,6 +918,27 @@ NtAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
         return STATUS_SUCCESS;
     }
 
+    /* Protect probe in SEH */
+    _SEH2_TRY
+    {
+        /* Probe all pointers */
+        ProbeForRead(GenericMapping, sizeof(GENERIC_MAPPING), sizeof(ULONG));
+        ProbeForRead(PrivilegeSetLength, sizeof(ULONG), sizeof(ULONG));
+        ProbeForWrite(PrivilegeSet, *PrivilegeSetLength, sizeof(ULONG));
+        ProbeForWrite(GrantedAccess, sizeof(ACCESS_MASK), sizeof(ULONG));
+        ProbeForWrite(AccessStatus, sizeof(NTSTATUS), sizeof(ULONG));
+    }
+    _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
+    {
+        /* Return the exception code */
+        _SEH2_YIELD(return _SEH2_GetExceptionCode());
+    }
+    _SEH2_END;
+
+    /* Check for unmapped access rights */
+    if (DesiredAccess & (GENERIC_READ | GENERIC_WRITE | GENERIC_EXECUTE | GENERIC_ALL))
+        return STATUS_GENERIC_NOT_MAPPED;
+
     /* Reference the token */
     Status = ObReferenceObjectByHandle(TokenHandle,
                                        TOKEN_QUERY,
@@ -713,16 +948,57 @@ NtAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
                                        NULL);
     if (!NT_SUCCESS(Status))
     {
-        DPRINT1("Failed to reference token (Status %lx)\n", Status);
+        DPRINT("Failed to reference token (Status %lx)\n", Status);
         return Status;
     }
 
     /* Check token type */
     if (Token->TokenType != TokenImpersonation)
     {
-        DPRINT1("No impersonation token\n");
+        DPRINT("No impersonation token\n");
+        ObDereferenceObject(Token);
+        return STATUS_NO_IMPERSONATION_TOKEN;
+    }
+
+    /* Check the impersonation level */
+    if (Token->ImpersonationLevel < SecurityIdentification)
+    {
+        DPRINT("Impersonation level < SecurityIdentification\n");
         ObDereferenceObject(Token);
-        return STATUS_ACCESS_DENIED;
+        return STATUS_BAD_IMPERSONATION_LEVEL;
+    }
+
+    /* Capture the security descriptor */
+    Status = SeCaptureSecurityDescriptor(SecurityDescriptor,
+                                         PreviousMode,
+                                         PagedPool,
+                                         FALSE,
+                                         &CapturedSecurityDescriptor);
+    if (!NT_SUCCESS(Status))
+    {
+        DPRINT("Failed to capture the Security Descriptor\n");
+        ObDereferenceObject(Token);
+        return Status;
+    }
+
+    /* Check the captured security descriptor */
+    if (CapturedSecurityDescriptor == NULL)
+    {
+        DPRINT("Security Descriptor is NULL\n");
+        ObDereferenceObject(Token);
+        return STATUS_INVALID_SECURITY_DESCR;
+    }
+
+    /* Check security descriptor for valid owner and group */
+    if (SepGetSDOwner(SecurityDescriptor) == NULL ||  // FIXME: use CapturedSecurityDescriptor
+        SepGetSDGroup(SecurityDescriptor) == NULL)    // FIXME: use CapturedSecurityDescriptor
+    {
+        DPRINT("Security Descriptor does not have a valid group or owner\n");
+        SeReleaseSecurityDescriptor(CapturedSecurityDescriptor,
+                                    PreviousMode,
+                                    FALSE);
+        ObDereferenceObject(Token);
+        return STATUS_INVALID_SECURITY_DESCR;
     }
 
     /* Set up the subject context, and lock it */
@@ -732,21 +1008,48 @@ NtAccessCheck(IN PSECURITY_DESCRIPTOR SecurityDescriptor,
     SubjectSecurityContext.ProcessAuditId = NULL;
     SeLockSubjectContext(&SubjectSecurityContext);
 
-    /* Now perform the access check */
-    SepAccessCheck(SecurityDescriptor,
-                   &SubjectSecurityContext,
-                   TRUE,
-                   DesiredAccess,
-                   0,
-                   &PrivilegeSet, //FIXME
-                   GenericMapping,
-                   PreviousMode,
-                   GrantedAccess,
-                   AccessStatus,
-                   SecurityIdentification);
-
-    /* Unlock subject context and dereference the token */
+    /* Check if the token is the owner and grant WRITE_DAC and READ_CONTROL rights */
+    if (DesiredAccess & (WRITE_DAC | READ_CONTROL | MAXIMUM_ALLOWED))
+    {
+        if (SepTokenIsOwner(Token, SecurityDescriptor)) // FIXME: use CapturedSecurityDescriptor
+        {
+            if (DesiredAccess & MAXIMUM_ALLOWED)
+                PreviouslyGrantedAccess |= (WRITE_DAC | READ_CONTROL);
+            else
+                PreviouslyGrantedAccess |= (DesiredAccess & (WRITE_DAC | READ_CONTROL));
+
+            DesiredAccess &= ~(WRITE_DAC | READ_CONTROL);
+        }
+    }
+
+    if (DesiredAccess == 0)
+    {
+        *GrantedAccess = PreviouslyGrantedAccess;
+        *AccessStatus = STATUS_SUCCESS;
+    }
+    else
+    {
+        /* Now perform the access check */
+        SepAccessCheck(SecurityDescriptor, // FIXME: use CapturedSecurityDescriptor
+                       &SubjectSecurityContext,
+                       DesiredAccess,
+                       PreviouslyGrantedAccess,
+                       &PrivilegeSet, //FIXME
+                       GenericMapping,
+                       PreviousMode,
+                       GrantedAccess,
+                       AccessStatus);
+    }
+
+    /* Unlock subject context */
     SeUnlockSubjectContext(&SubjectSecurityContext);
+
+    /* Release the captured security descriptor */
+    SeReleaseSecurityDescriptor(CapturedSecurityDescriptor,
+                                PreviousMode,
+                                FALSE);
+
+    /* Dereference the token */
     ObDereferenceObject(Token);
 
     /* Check succeeded */