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/*++
Copyright (c) 1989 Microsoft Corporation
Module Name:
Sep.c
Abstract:
This Module implements the private security routine that are defined
in sep.h
Author:
Gary Kimura (GaryKi) 9-Nov-1989
Environment:
Kernel Mode
Revision History:
--*/
#include "sep.h"
#include "seopaque.h"
#ifdef ALLOC_PRAGMA
#pragma alloc_text(PAGE,SepCheckAcl)
#endif
#define LongAligned( ptr ) (LongAlign(ptr) == ((PVOID)(ptr)))
#define WordAligned( ptr ) (WordAlign(ptr) == ((PVOID)(ptr)))
BOOLEAN
SepCheckAcl (
IN PACL Acl,
IN ULONG Length
)
/*++
Routine Description:
This is a private routine that checks that an acl is well formed.
Arguments:
Acl - Supplies the acl to check
Length - Supplies the real size of the acl. The internal acl size
must agree.
Return Value:
BOOLEAN - TRUE if the acl is well formed and FALSE otherwise
--*/
{
PACE_HEADER Ace;
PISID Sid;
PISID Sid2;
ULONG i;
UCHAR AclRevision = ACL_REVISION2;
if (!ValidAclRevision(Acl)) {
return(FALSE);
}
if (!LongAligned(Acl->AclSize)) {
return(FALSE);
}
//
// Validate all of the ACEs.
//
Ace = ((PVOID)((PUCHAR)(Acl) + sizeof(ACL)));
for (i = 0; i < Acl->AceCount; i++) {
//
// Check to make sure we haven't overrun the Acl buffer
// with our ace pointer. Make sure the ACE_HEADER is in
// the ACL also.
//
if ((PUCHAR)Ace + sizeof(ACE_HEADER) >= ((PUCHAR)Acl + Acl->AclSize)) {
return(FALSE);
}
if (!WordAligned(&Ace->AceSize)) {
return(FALSE);
}
if ((PUCHAR)Ace + Ace->AceSize > ((PUCHAR)Acl + Acl->AclSize)) {
return(FALSE);
}
//
// It is now safe to reference fields in the ACE header.
//
//
// The ACE header fits into the ACL, if this is a known type of ACE,
// make sure the SID is within the bounds of the ACE
//
if (IsKnownAceType(Ace)) {
if (!LongAligned(Ace->AceSize)) {
return(FALSE);
}
if (Ace->AceSize < sizeof(KNOWN_ACE) - sizeof(ULONG) + sizeof(SID)) {
return(FALSE);
}
//
// It's now safe to reference the parts of the SID structure, though
// not the SID itself.
//
Sid = (PISID) & (((PKNOWN_ACE)Ace)->SidStart);
if (Sid->Revision != SID_REVISION) {
return(FALSE);
}
if (Sid->SubAuthorityCount > SID_MAX_SUB_AUTHORITIES) {
return(FALSE);
}
//
// SeLengthSid computes the size of the SID based on the subauthority count,
// so it is safe to use even though we don't know that the body of the SID
// is safe to reference.
//
if (Ace->AceSize < sizeof(KNOWN_ACE) - sizeof(ULONG) + SeLengthSid( Sid )) {
return(FALSE);
}
} else {
//
// If it's a compound ACE, then perform roughly the same set of tests, but
// check the validity of both SIDs.
//
if (IsCompoundAceType(Ace)) {
//
// Save away the fact that we saw a compound ACE while traversing the ACL.
//
AclRevision = ACL_REVISION3;
if (!LongAligned(Ace->AceSize)) {
return(FALSE);
}
if (Ace->AceSize < sizeof(KNOWN_COMPOUND_ACE) - sizeof(ULONG) + sizeof(SID)) {
return(FALSE);
}
//
// The only currently defined Compound ACE is an Impersonation ACE.
//
if (((PKNOWN_COMPOUND_ACE)Ace)->CompoundAceType != COMPOUND_ACE_IMPERSONATION) {
return(FALSE);
}
//
// Examine the first SID and make sure it's structurally valid,
// and it lies within the boundaries of the ACE.
//
Sid = (PISID) & (((PKNOWN_COMPOUND_ACE)Ace)->SidStart);
if (Sid->Revision != SID_REVISION) {
return(FALSE);
}
if (Sid->SubAuthorityCount > SID_MAX_SUB_AUTHORITIES) {
return(FALSE);
}
//
// Compound ACEs contain two SIDs. Make sure this ACE is large enough to contain
// not only the first SID, but the body of the 2nd.
//
if (Ace->AceSize < sizeof(KNOWN_COMPOUND_ACE) - sizeof(ULONG) + SeLengthSid( Sid ) + sizeof(SID)) {
return(FALSE);
}
//
// It is safe to reference the interior of the 2nd SID.
//
Sid2 = (PISID) ((PUCHAR)Sid + SeLengthSid( Sid ));
if (Sid2->Revision != SID_REVISION) {
return(FALSE);
}
if (Sid2->SubAuthorityCount > SID_MAX_SUB_AUTHORITIES) {
return(FALSE);
}
if (Ace->AceSize < sizeof(KNOWN_COMPOUND_ACE) - sizeof(ULONG) + SeLengthSid( Sid ) + SeLengthSid( Sid2 )) {
return(FALSE);
}
}
}
//
// And move Ace to the next ace position
//
Ace = ((PVOID)((PUCHAR)(Ace) + ((PACE_HEADER)(Ace))->AceSize));
}
return(TRUE);
}
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