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Last active August 29, 2015 14:05
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Asserts physical presence on the Atmel I2C TPM. Stop tcsd, send the command, and restart tcsd. Thanks to @theopolis for initial version of this code!
/* -*- mode: c; c-file-style: "gnu" -*-
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <>.
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netinet/in.h>
int main() {
/* startup contains the raw bytes for issuing a TPM startup and
specifying physical presence. This is needed to clear the compliance
vectors. This is a TCG command see the TCG specification or page 281
of "Trusted Platform Module Basics" by Steven Kinney
char startup[] = {
0x0, 0xc1, /* Authorization Tag */
0x0, 0x0, 0x0, 0xc, /* Parameter Size */
0x40, 0x0, 0x0, 0xa, /* Ordinal */
0x0, 0x8, /* Startup Type */
int fd;
int err;
int rc = 1;
fd = open ("/dev/tpm0", O_RDWR);
if ( fd < 0 )
printf ("%s\n", "Unable to open the device.");
goto out_noclose;
err = write (fd, startup, sizeof (startup));
if ( err != sizeof (startup) )
printf( "%s%d\n", "Error occurred while sending command: ", errno );
goto out;
rc = 0;
printf ("%s\n", "Physical presence asserted." );
return rc;
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