Secure firmware interface
A mailbox mechanism is used for communication of secure messages from a server to the firmware of a device. Mailbox content provided by the server is authenticated in a driver execution environment of the device, using reboots across the communication sessions, and then stored in secure storage. The communication sessions include first receiving a signed server key, and then receiving a message from the server that is based on a hash of a nonce generated by the device.
1. A system for sending a command to a device, comprising:
at least one server;
the at least one server having a server processor and server memory connected to the server processor;
at least one device configured to be in communication with the at least on server, and
the at least one device having a device processor; and
device memory connected to the device processor;
the server memory comprising server instructions that when executed by the server processor cause the at least one server to send a signed server key to any one or more of the at least one device;
upon reboot of the at least one device a first time, the at least one device executes device instructions stored in the device memory which cause the device to verify the signed server key in a DXE (driver execution environment) of firmware in the at least one device's firmware and send a nonce to the at least one server, the nonce being encrypted using the signed server key;
upon receipt of the nonce, the at least one server sends a message to the at least one device that includes a first portion with a secure command and a second portion that is based on a hash of the nonce;
the at least one device configured to reboot a second time after receipt of the message and verify the message in the DXE of the at least one device's, firmware; and
execute the secure command on the at least one device.
2. The system according to claim 1 , wherein the second portion is the nonce hash of the nonce.
3. The system according to claim 1 , wherein the at least one device comprises a plurality of devices and the signed server key is sent by the at least one server to the plurality of devices that are served by the at least one server.
4. The system according to claim 3 , wherein the plurality of devices have the same make and model.
5. The system according to claim 1 , wherein the signed server key is signed by a further, signing server.
6. The system according to claim 1 , wherein the second portion is a signature that is calculated as if the nonce hash of the nonce were in the message.
7. The system according to claim 1 , further configured wherein the device instructions, when executed by the device processor, cause the at least one device to save state data in secure storage in the device in response to verifying the message.