// GetEKCert reads the Endorsement Key certificate from the TPM's NVRAM and
// returns it, along with any error generated.
func GetEKCert(context *tspi.Context) (ekcert []byte, err error) {
var wellKnown [20]byte
tpm := context.GetTPM()
nv, err := context.CreateNV()
if err != nil {
return nil, err
}
policy, err := tpm.GetPolicy(tspi.TSS_POLICY_USAGE)
if err != nil {
return nil, err
}
policy.SetSecret(tspi.TSS_SECRET_MODE_SHA1, wellKnown[:])
nv.SetIndex(0x1000f000)
nv.AssignPolicy(policy)
data, err := nv.ReadValue(0, 5)
if err != nil {
return nil, err
}
tag := (uint)((uint)(data[0])<<8 | (uint)(data[1]))
if tag != 0x1001 {
return nil, fmt.Errorf("Invalid tag: %x", tag)
}
if data[2] != 0 {
return nil, fmt.Errorf("Invalid certificate")
}
ekbuflen := (uint)(uint(data[3])<<8 | (uint)(data[4]))
offset := (uint)(5)
data, err = nv.ReadValue(offset, 2)
tag = (uint)((uint)(data[0])<<8 | (uint)(data[1]))
if tag == 0x1002 {
offset += 2
ekbuflen -= 2
} else if data[0] != 0x30 {
return nil, fmt.Errorf("Invalid header: %x\n", tag)
}
ekoffset := (uint)(0)
var ekbuf []byte
for ekoffset < ekbuflen {
length := (uint)(ekbuflen - ekoffset)
if length > 128 {
length = 128
}
data, err = nv.ReadValue(offset, length)
if err != nil {
return nil, err
}
ekbuf = append(ekbuf, data...)
offset += length
ekoffset += length
}
return ekbuf, nil
}
