Covert channel for conveying supplemental messages in a protocol-defined link for a system of storage devices

• US 7,571,269 B2
• Filed: 12/20/2005
• Issued: 08/04/2009
• Est. Priority Date: 08/25/2005
• Status: Active Grant

• Current Assignee: Lattice Semiconductor Corporation
• Original Assignee: Silicon Image, Inc. (Lattice Semiconductor Corporation)
• Inventors: Hanko, James Gregory, Schmidt, Brian K.
• Primary Examiner(s): Rinehart; Mark
• Assistant Examiner(s): MISIURA, BRIAN THOMAS
• Application Number:
  US11/314,162
• Publication Number:
  US 20070180172A1
• Time in Patent Office: 1,323 Days
• Field of Search: 711/146, 710/105
• US Class Current: 710/105
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices
• CPC Class Codes: G06F 13/4027 using bus bridges G06F13/4022 takes precedence

Abstract

Disclosed are communication apparatus, a SATA communication device, a system, an enhanced port multiplier and a method for, among other things, establishing a covert communication channel in a protocol-compliant link. In one embodiment, a communication apparatus includes a link interface and a supplemental message interface. The link interface is configured to communicatively couple the communication apparatus to the link for accessing a data stream passing through the link in accordance with a standardized protocol. The supplemental message interface is configured to exchange a supplemental message within the data stream to establish a covert communication channel in the link. The supplemental message supplements the standardized protocol without violating the protocol.

Claims

1. A communication apparatus for conveying supplemental messages via a link between a host and a point within a system of storage devices, the communication apparatus comprising:

a link interface configured to communicatively couple the communication apparatus to the link for accessing a data stream passing through the link in accordance with a standardized protocol; and

a supplemental message interface configured to exchange a supplemental message with the data stream to establish a covert communication channel in the link, the supplemental message interface including a supplemental message observer configured to identify a supplemental downlink message in the data stream, the supplemental message observer including;

a downlink receiver configured to;

identify a portion of the supplemental downlink message, and

acquire the portion of the supplemental downlink message, the downlink receiver being responsive to a first protocol-compliant message, and

a supplemental message composition buffer configured to compose the supplemental downlink message from a number of portions of the supplemental downlink message;

wherein the supplemental message supplements the standardized protocol.

2. The communication apparatus of claim 1, wherein the covert communication channel introduces the supplemental messages in the data stream such that the link maintains compliance with the standardized protocol.

3. The communication apparatus of claim 2, wherein the covert communication channel embeds the supplemental messages in the data stream without either altering protocol-compliant data of the data stream or accessing the system of storage devices to alter data stored therein, or both.

4. The communication apparatus of claim 1, wherein the supplemental message comprises a supplemental command configured to perform a storage-related function at a point within the system of storage devices, thereby performing the storage-related function downstream from the host.

5. The communication apparatus of claim 1, wherein the link is a serial link.

6. The communication apparatus of claim 1, wherein the supplemental message interface comprises a supplemental message interposer for interposing the supplemental message within the data stream.

7. The communication apparatus of claim 6, wherein the supplemental message interposer is configured to interpose portions of the supplemental message with portions of the data stream.

8. The communication apparatus of claim 6, wherein the supplemental message interposer comprises:

an uplink transmitter configured to transmit a portion of a supplemental uplink message, the uplink transmitter being responsive to a second protocol-compliant message.

9. The communication apparatus of claim 8, wherein the second protocol-compliant message includes a non-write command that returns a response message.

10. The communication apparatus of claim 1 wherein the first protocol-compliant message includes a read command.

15. A communication apparatus according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the standardized protocol is Serial Advanced Technology Attachment (“

SATA”

) protocol.

11. A supplemental message originator for use in a host computing device to establish a covert channel via a protocol-compliant link through which a data stream passes between the host computing device and a storage-related device in accordance with a protocol, the supplemental message originator comprising:

a message controller configured to format a first message undefined by the protocol to generate a first formatted message for transmission over the protocol-compliant link;

a host downlink transmitter configured to integrate the first formatted message into the data stream, thereby establishing at least a portion of a covert communication channel for conveying the formatted message via the protocol-compliant link; and

a host uplink receiver configured to acquire a second formatted message undefined by the protocol, thereby establishing at least a second portion of the covert communication channel;

wherein the covert communication channel facilitates transmissions of noncompliant messages over the protocol-compliant link in compliance with the protocol; and

wherein the message controller is further configured to;

detect other packets from the second portion of the covert communication channel, and

reconstruct a second message from the second formatted message in the other packets.

12. The supplemental message originator of claim 11 wherein the message controller is further configured to:

decompose the first message into portions of the first message;

determine offsets for the portions of the first message, the portions of the first message and the offsets constituting the first formatted message; and

include a portion of the first message and an offset in a packet of the portion of the covert communication channel.

13. The supplemental message originator of claim 12, wherein the packet further includes a READ command compliant with the protocol.

14. The supplemental message originator of claim 11, wherein the second packet further includes a response to an IDENTIFY DEVICE command compliant with the protocol.

16. A supplemental message originator according to any one of claims 11, 12, 13, or 14, wherein the standardized protocol is Serial Advanced Technology Attachment (“

SATA”

) protocol.