POINTGUARD: METHOD AND SYSTEM FOR PROTECTING PROGRAMS AGAINST POINTER CORRUPTION ATTACKS

• US 20080060077A1
• Filed: 10/31/2007
• Published: 03/06/2008
• Est. Priority Date: 12/06/2001
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Novell Incorporated (Open Text Corporation)
• Inventors: Arnold, Seth, Beattie, Steven, Wagle, Perry, Cowan, Stanley
• Granted Patent: US 8,631,248 B2
• Time in Patent Office: Days
• US Class Current: 726/25
• CPC Class Codes: G06F 12/1408 by using cryptography for digital transmission H04L9/00
• CPC Class Codes: G06F 21/125 by manipulating the program code, e.g. source code, compiled code, interpreted code, machine code
• CPC Class Codes: G06F 21/52 during program execution, e.g. stack integrity ; Preventing unwanted data erasure; Buffer overflow
• CPC Class Codes: G06F 9/4486 Formation of subprogram jump address

Abstract

To protect computer programs against security attacks that attempt to corrupt pointers within the address space of the program, the value of a pointer is encrypted each time the pointer is initialized or modified, and then the value is decrypted before use, i.e., each time the pointer is read. Preferably, the encrypting and decrypting steps are effected by instructions generated by a compiler during compilation of the program. One convenient method of implementing the encrypting and decrypting steps is by XOR'"'"'ing the pointer with a predetermined encryption key value, which could be specially selected or selected at random.

Claims

1. A method of protecting an application computer program against pointer corruption attacks while employing a shared library, the method comprising the steps of:

in the library, responsive to a function call, exporting at least two versions of the called function, including a first version and a second version, wherein one of the first and second versions effects pointer protection by encrypting a value of a pointer each time the value of the pointer is modified; and

decrypting the encrypted value of the pointer each time the pointer is read.

2. A method according to claim 1, wherein encrypting a value of a pointer includes XOR'"'"'ing the value of the pointer with an encryption key.

3. A method according to claim 2, further comprising initializing the encryption key at program load time.

4. A method according to claim 3, further comprising:

loading the computer program;

scanning code being dynamically linked by the program; and

determining if all of the code being linked by the program uses encrypted pointers.

5. A method according to claim 4, further comprising setting the encryption key value to a random value if all of the code being linked by the program uses encrypted pointers.

6. A method according to claim 4, further comprising initializing the encryption key value to zero if at least one library being linked by the program does not use encrypted pointers.

7. A method according to claim 3, further comprising initializing the encryption key at system boot time.

8. A method of protecting a computer program against pointer corruption attacks while employing a shared library, comprising:

running a program; and

linking the program to a shared library, wherein at least one of the program and the shared library includes un-encrypted pointers, and at least one of the program and the shared library includes encrypted pointers.