On 2/6/2020 3:42 PM, Martin Galvan wrote:
Hi all,
I'm working on an application that needs to retrieve some information
from a 1.2 TPM, such as its manufacturer info and values of its
Permanent flags. My application usually just opens the TPM driver and
talks directly to it; however, I saw that tcsd will open the driver
and make it return EBUSY whenever my app tries to open it. Looking at
man tcsd I saw the following:
"tcsd is a user space daemon that should be (according to the TSS
spec) the only portal to the TPM device driver. At boot time, tcsd
should be started, it should open the TPM device driver and from that
point on, all requests to the TPM should go through the TSS stack."
I understand that, in order to talk to tcsd, my app should be linked
against libtspi. This is undesirable for many reasons, so I'd like to
know whether there's another way for me to communicate with the TPM
when tcsd is running.
tcsd locks the TPM device driver by design because it handles
scheduling and resource management. If another process could,
e.g., flush a key, applications would break.
In theory, you don't have to link to the TSS to connect to
tcsd. However, I don't think the tcsd interface is documented,
so it may be a lot of work.
BTW, for TPM 2.0, the resource manager is built into the device
driver. There is no tcsd or other user space daemon. It's
a much cleaner design.
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