571106 - (CVE-2010-2753) nsTreeSelection Dangling Pointer Remote Code Execution Vulnerability (ZDI-CAN-755)

Status: RESOLVED FIXED

(Core :: XUL, defect)

Description

[Reed Loden [:reed]]

Attachment: XUL testcase

ZDI-CAN-755: Mozilla Firefox nsTreeSelection Dangling Pointer Remote Code Execution Vulnerability



-- ABSTRACT ------------------------------------------------------------



TippingPoint has identified a vulnerability affecting the following 

products:



    Mozilla Firefox 3.6.x



-- VULNERABILITY DETAILS -----------------------------------------------



This vulnerability allows remote attackers to execute arbitrary code on

vulnerable installations of Mozilla Firefox. User interaction is

required to exploit this vulnerability in that the target must visit a

malicious page or open a malicious file.



The specific flaw exists within the implementation of XUL <tree>

element's "selection" attribute. There is an integer overflow when

calculating the bounds of a new selection range. When calling

adjustSelection on this manged range both ranges are deleted leaving a

dangling reference. A remote attacker can exploit this vulnerability to

execute arbitrary code under the context of the browser.





View of XUL <tree> element exposes "selection" attribute. This in turn

allows user to precisely choose set of tree's rows to be shown as

selected. The way class nsTreeSelection

(layout/xul/base/src/tree/src/nsTreeSelection.cpp) is implemented is

quite interesting: with a linked list of nsTreeRange instances where

nsTreeRange represents single continuous range of selected rows (and

possibly a pointer to the next range). nsTreeSelection holds directly

only one pointer, to the first range, mFirstRange.



What is also important to note: whenever any nsTreeRange instance is

deleted, delete (inside destructor) is called recursively on the next

linked instances as well.



Imagine we have the following piece of Javascript code:



  [1]  sel = tree.treeBoxObject.view.selection;

  [2]  sel.rangedSelect(0, 0x7fffffff, true);

  [3]  sel.adjustSelection(1, 1);



At [1] we grab the reference to selection object. At this moment

mFirstRange is null, no row is selected, so there is no need for any

range to keep track of.



Then [2] we call method rangedSelect(). From

nsTreeSelection::RangedSelect():



  ...

  PRInt32 start = aStartIndex < aEndIndex ? aStartIndex : aEndIndex;

  PRInt32 end = aStartIndex < aEndIndex ? aEndIndex : aStartIndex;

  ...

  nsTreeRange* range = new nsTreeRange(this, start, end);

  if (!range)

    return NS_ERROR_OUT_OF_MEMORY;



  range->Invalidate();



  if (aAugment && mFirstRange)

    mFirstRange->Insert(range);

  else

    mFirstRange = range;

  ...



That makes mFirstRange being set to range <0, 2G>, or more precisely

(yet in ad hoc pseudo code):



  mFirstRange = {

    min:  0,

    max:  2G,

    prev: null,

    next: null

  }



And at [3] we hit integer overflow that causes a lot of trouble. From

nsTreeSelection::AdjustSelection(PRInt32 aIndex, PRInt32 aCount):



  ...

  nsTreeRange* newRange = nsnull;



  PRBool selChanged = PR_FALSE;

  nsTreeRange* curr = mFirstRange;

  while (curr) {

    if (aCount > 0) {

      // inserting

      if (aIndex > curr->mMax) {

        ...

      }

      else if (aIndex <= curr->mMin) {

        ...

      }

      else {

        // adjustment happen inside the range.

        // break apart the range and create two ranges

        ADD_NEW_RANGE(newRange, this, curr->mMin, aIndex - 1);

        ADD_NEW_RANGE(newRange, this, aIndex + aCount, curr->mMax +

aCount);

        selChanged = PR_TRUE;

      }

    }

    else {

      ...

    }

    curr = curr->mNext;

  }



  delete mFirstRange;

  mFirstRange = newRange;

  ...



As we are calling AdjustSelection(1, 1), two ADD_NEW_RANGE() are

executed.

This means that something like <0, 0>.Insert(<2, -2G>) will be called.

Notice that because of integer overflow lower bound (2) is above higher

bound (-2G).



  void Insert(nsTreeRange* aRange) {

    if (mMin >= aRange->mMax)

      aRange->Connect(mPrev, this);

    else if (mNext)

      mNext->Insert(aRange);

    else 

      aRange->Connect(this, nsnull);

  }



So, now <2, -2G>.Connect(mPrev = null, <0, 0>):



  void Connect(nsTreeRange* aPrev = nsnull, nsTreeRange* aNext = nsnull)

{

    if (aPrev)

      aPrev->mNext = this;

    else

      mSelection->mFirstRange = this;



    if (aNext)

      aNext->mPrev = this;



    mPrev = aPrev;

    mNext = aNext;

  }



Which results in:



  mFirstRange = {

    min:  2,

    max:  -2G,

    prev: null,

    next: {

      min:  0,

      max:  0,

      prev: mFirstRange,

      next: null

    }

  }



But we can not forget about the epilogue of AdjustSelection():



  delete mFirstRange;

  mFirstRange = newRange;



Final result: both ranges (<2, -2G>, <0, 0>) are deleted and mFirstRange

points at deleted range <0, 0>.



-- CREDIT --------------------------------------------------------------



This vulnerability was discovered by:

    * regenrecht

Comment 1

[Reed Loden [:reed]]

bp-99ea876b-1fe9-4df4-924b-dfdde2100609

Comment 2

[Daniel Veditz [:dveditz]]

On Mac 3.5.11pre and 3.6.6pre it looks like a null-deref DoS
3.5: bp-2d7a4637-6ce5-47b0-867c-a41ca2100609
3.6: bp-c584be08-5186-402e-bee2-f6af42100609

I get a similar Mac trunk crash to Reed's Linux one above.
bp-e901aaaf-6b71-4603-8d96-64f722100609

The code looks the same though, so I'd expect all versions to have the same issues as described in comment 0.

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

Attachment: simple version

Make sure nsTreeRange is created in a proper way.

Other cases when nsTreeRange is created manually without the macro are safe.

Comment 4

[[e-mail]]

Comment on attachment 450359 [details] [diff] [review]
simple version

>+    PRInt32 start = macro_start; \
Not sure why you created a temporary for macro_start but still double-evaluated macro_end?

>+    PRInt32 end = start < macro_end ? macro_end : start; \
Nit: start > macro_end is the (hopefully unlikely) bug case; start = macro_end and start < macro_end are equally likely, so this hurts branch prediction.

Comment 5

[Olli Pettay [:smaug][[e-mail]]]

ok, I'll tweak the patch a bit.

Comment 6

[Olli Pettay [:smaug][[e-mail]]]

I'll update the patch tomorrow.

Comment 7

[Olli Pettay [:smaug][[e-mail]]]

Attachment: patch

Comment 8

[Olli Pettay [:smaug][[e-mail]]]

http://hg.mozilla.org/mozilla-central/rev/1353f853b17a

Comment 9

[Daniel Veditz [:dveditz]]

Comment on attachment 451552 [details] [diff] [review]
patch

Approved for 1.9.2.6 and 1.9.1.11, a=dveditz for release-drivers

Comment 10

[Olli Pettay [:smaug][[e-mail]]]

http://hg.mozilla.org/releases/mozilla-1.9.2/rev/9003d01b2009
http://hg.mozilla.org/releases/mozilla-1.9.1/rev/a995876d5219

Comment 11

[Al Billings [:abillings - ex-MoCo]]

Verified for 1.9.1.11 using attached testcase and build 1 (Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.11) Gecko/20100701 Firefox/3.5.11 (.NET CLR 3.5.30729)). 

Verified for 1.9.2.7 with its build 1 (Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.7) Gecko/20100701 Firefox/3.6.7 (.NET CLR 3.5.30729)).

Verified that 1.9.1.10 and 1.9.2.6 both crash with the testcase.

Comment 12

[Smokey Ardisson (offline for a while; not following bugs - do not email)]

Comment on attachment 451552 [details] [diff] [review]
patch

Requesting approval1.9.0.next on this patch so that we can take it in upcoming Camino 2.0.x security and stability updates.  If approved, I'll handle the checkins, unless the patch author requests otherwise.

Comment 13

[Daniel Veditz [:dveditz]]

Comment on attachment 451552 [details] [diff] [review]
patch

Approved for 1.9.0.20, a=dveditz

Comment 14

[Smokey Ardisson (offline for a while; not following bugs - do not email)]

Checking in layout/xul/base/src/tree/src/nsTreeSelection.cpp;
/cvsroot/mozilla/layout/xul/base/src/tree/src/nsTreeSelection.cpp,v  <--  nsTreeSelection.cpp
new revision: 1.63; previous revision: 1.62
done

Comment 15

[Daniel Veditz [:dveditz]]

We need an in-tree regression test for this.

Comment 16

[Daniel Veditz [:dveditz]]

making private again while we fix bug 585815