Methods, Systems, and Computer Program Products for Class Verification

• US 20090031202A1
• Filed: 07/27/2007
• Published: 01/29/2009
• Est. Priority Date: 07/27/2007
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Stecher, John J., Branda, Steven J.
• Granted Patent: US 8,060,812 B2
• Time in Patent Office: Days
• US Class Current: 714/807
• CPC Class Codes: G06F 11/1004 to protect a block of data words, e.g. CRC or checksum G06F11/1076 takes precedence; security arrangements for protecting computers or computer systems against unauthorized activity G06F21/00
• CPC Class Codes: G06F 9/44589 Program code verification, e.g. Java bytecode verification, proof-carrying code high-level semantic checks G06F8/43; testing and debugging software G06F11/36

Abstract

A method, system, and computer program product for class verification are provided. The method includes initiating loading of a class, and searching for the class in verification caches. A record from the verification caches, including a checksum, is returned upon locating the class. The method further includes comparing the checksum in the record to a checksum of the class being loaded, and completing the loading of the class when the checksums match. The method additionally includes performing bytecode verification of the class upon one of: a checksum comparison mismatch, and a failure to locate the class in the verification caches. The method also includes calculating a new checksum of the class upon a successful bytecode verification, and storing the new checksum in the verification caches.

Claims

1. A method for class verification, comprising:

initiating loading of a class;

searching for the class in verification caches, wherein a record from the verification caches, including a checksum, is returned upon locating the class;

comparing the checksum in the record to a checksum of the class being loaded;

completing the loading of the class when the checksums match;

performing bytecode verification of the class upon one of;

a checksum comparison mismatch, and a failure to locate the class in the verification caches;

calculating a new checksum of the class upon a successful bytecode verification; and

storing the new checksum in the verification caches.

2. The method of claim 1 further comprising:

creating a new record in the verification caches upon a failure to locate the class in the verification caches, wherein the new checksum is stored in the new record.

3. The method of claim 1 wherein searching for the class in a verification cache further comprises using the class name as a key into a verification index to locate the record for the class.

4. The method of claim 1 wherein performing bytecode verification includes scanning the bytecode for conformance with a programming language standard.

5. The method of claim 1 wherein the class is a component class and further comprising:

checking the component class for an extension point tag, wherein the extension point tag defines a relationship between the component class and another class referenced by the component class.

6. The method of claim 5 further comprising performing class verification on the class referenced by the component class.

7. The method of claim 1 wherein the class is a compressed file, and the checksum of the class is calculated without decompressing the compressed file.

8. The method of claim 1 further comprising:

applying a verification tag to the loaded class upon a successful bytecode verification of the class; and

performing a partial verification on a class attempting to access verification tagged loaded class, wherein the partial verification includes checking variable access to prevent scoping constraint violations.

9. A system for class verification, comprising:

a data storage device holding verification caches; and

a host system in communication with the data storage device, the host system executing a virtual machine (VM), including a class verifier, the VM performing;

initiating loading of a class;

searching for the class in the verification caches, wherein a record from the verification caches, including a checksum, is returned upon locating the class;

comparing the checksum in the record to a checksum of the class being loaded;

completing the loading of the class when the checksums match;

performing bytecode verification of the class upon one of;

a checksum comparison mismatch, and a failure to locate the class in the verification caches;

calculating a new checksum of the class upon a successful bytecode verification; and

storing the new checksum in the verification caches.

10. The system of claim 9 wherein the VM further performs:

creating a new record in the verification caches upon a failure to locate the class in the verification caches, wherein the new checksum is stored in the new record.

11. The system of claim 9 wherein searching for the class in a verification cache further comprises using the class name as a key into a verification index to locate the record for the class.

12. The system of claim 9 wherein performing bytecode verification includes scanning the bytecode for conformance with a programming language standard.

13. The system of claim 9 wherein the class is a component class and the VM further performs:

checking the component class for an extension point tag, wherein the extension point tag defines a relationship between the component class and another class referenced by the component class.

14. The system of claim 13 wherein the VM further performs class verification on the class referenced by the component class.

15. The system of claim 9 wherein the class is a compressed file, and the checksum of the class is calculated without decompressing the compressed file.

16. The system of claim 9 wherein the VM further performs:

applying a verification tag to the loaded class upon a successful bytecode verification of the class; and

performing a partial verification on a class attempting to access verification tagged loaded class, wherein the partial verification includes checking variable access to prevent scoping constraint violations.

17. A computer program product for class verification, the computer program product comprising:

a storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for implementing a method, the method comprising;

initiating loading of a class;

searching for the class in verification caches, wherein a record from the verification caches, including a checksum, is returned upon locating the class;

comparing the checksum in the record to a checksum of the class being loaded;

completing the loading of the class when the checksums match;

performing bytecode verification of the class upon one of;

a checksum comparison mismatch, and a failure to locate the class in the verification caches;

calculating a new checksum of the class upon a successful bytecode verification; and

storing the new checksum in the verification caches.

18. The computer program product of claim 17 wherein the class is a component class and further comprising:

checking the component class for an extension point tag, wherein the extension point tag defines a relationship between the component class and another class referenced by the component class; and

performing class verification on the class referenced by the component class.

19. The computer program product of claim 17 wherein the class is a compressed file, and the checksum of the class is calculated without decompressing the compressed file.

20. The computer program product of claim 17 further comprising:

applying a verification tag to the loaded class upon a successful bytecode verification of the class; and

performing a partial verification on a class attempting to access verification tagged loaded class, wherein the partial verification includes checking variable access to prevent scoping constraint violations.