RawDiskService

RawDisk service provides block-level read access to remote clients. This means remote clients have full read access to any drive in the host system that supports the Read10 SCSI CDB.

The goal of this project is to enable client-side tools that work with a number of different operating systems running the service.

Example Clients

Inspect GPT Header

Say there's a need to look at a system's GPT header to verify the CRC32 and compare contents with the secondary GPT header. The GPT header is at LBA 1 and reading that block is simply

TTransport transport = new TSocket(host, port);
// a few more lines of setup...
String response = client.readLBAPretty("/dev/sda", 1);

The response is a hexdump for LBA 1, the GPT header:

000000: 45 46 49 20 50 41 52 54  00 00 01 00 5c 00 00 00  |EFI PART....\...|
000010: d2 cc 1d 05 00 00 00 00  01 00 00 00 00 00 00 00  |................|
000020: af 44 f2 1b 00 00 00 00  22 00 00 00 00 00 00 00  |.D......".......|
000030: 8e 44 f2 1b 00 00 00 00  2e 05 9a e4 8c e6 43 42  |.D............CB|
000040: a7 a5 58 64 26 20 27 af  02 00 00 00 00 00 00 00  |..Xd& '.........|
000050: 80 00 00 00 80 00 00 00  60 4b 08 e5 00 00 00 00  |........`K......|

The secondary GPT header is the 8 bytes at offset 0x20 in the above hexdump. In little endian that's 0x1bf244af (468862127 decimal), and obtain the secondary GTP header with client.readLBAPretty("/dev/sda", 0x1bf244af);

With both headers in hand, we can take over the world.

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Implementation Details

RawDiskService supports both Windows and Linux, and requires root to run the server. Typically only \\.\physicaldriveN (on windows) and /dev/sdX (on linux) will work with the service.

Two libraries made the implementation very simple (initial prototype working within 2 hours):

• Apache Thrift. It's an interface design language (IDL) that solves the problem of client-server communication. From their site: The Apache Thrift software framework, for scalable cross-language services development, combines a software stack with a code generation engine to build services that work efficiently and seamlessly. Just write a thrift file and implement the server-side handlers, and Thrift does the rest.
• sgio.d. I wrote this D libarary to simplify creating scsi device drivers and prototypes. It's used in readfromdev, which does all of the native ioctl calls.

Author

Written by Lucas Burson [email protected]