heads/initrd/bin/seal-totp
Thierry Laurion 8259d3ca1e
Add TRACE function tracing function to output on console when enabled
- Add TRACE function tracing output under etc/functions, depending on CONFIG_ENABLE_FUNCTION_TRACING_OUTPUT enabled in board configs
- Replace current DEBUG to TRACE calls in code, reserving DEBUG calls for more verbose debugging later on (output of variables etc)
- add 'export CONFIG_ENABLE_FUNCTION_TRACING_OUTPUT=y' in qemu-coreboot(fb)whiptail-tpm1(-hotp) boards to see it in action
2023-02-20 11:44:52 -05:00

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#!/bin/sh
# Generate a random secret, seal it with the PCRs
# and write it to the TPM NVRAM.
#
# Pass in a hostname if you want to change it from the default string
#
. /etc/functions
TRACE "Under /bin/seal-totp"
TPM_NVRAM_SPACE=4d47
HOST="$1"
if [ -z "$HOST" ]; then
HOST="TPMTOTP"
fi
TOTP_SECRET="/tmp/secret/totp.key"
TOTP_SEALED="/tmp/secret/totp.sealed"
dd \
if=/dev/urandom \
of="$TOTP_SECRET" \
count=1 \
bs=20 \
2>/dev/null \
|| die "Unable to generate 20 random bytes"
secret="`base32 < $TOTP_SECRET`"
# Use the current values of the PCRs, which will be read
# from the TPM as part of the sealing ("X").
# PCR4 == 0 means that we are still in the boot process and
# not a recovery shell.
# should this read the storage root key?
if ! tpm sealfile2 \
-if "$TOTP_SECRET" \
-of "$TOTP_SEALED" \
-hk 40000000 \
-ix 0 X \
-ix 1 X \
-ix 2 X \
-ix 3 X \
-ix 4 0000000000000000000000000000000000000000 \
-ix 7 X \
; then
shred -n 10 -z -u "$TOTP_SECRET" 2> /dev/null
die "Unable to seal secret"
fi
shred -n 10 -z -u "$TOTP_SECRET" 2> /dev/null
# to create an nvram space we need the TPM owner password
# and the TPM physical presence must be asserted.
#
# The permissions are 0 since there is nothing special
# about the sealed file
tpm physicalpresence -s \
|| warn "Warning: Unable to assert physical presence"
# Try to write it without the password first, and then create
# the NVRAM space using the owner password if it fails for some reason.
if ! tpm nv_writevalue \
-in $TPM_NVRAM_SPACE \
-if "$TOTP_SEALED" \
; then
warn 'NVRAM space does not exist? Owner password is required'
read -s -p "TPM Owner password: " tpm_password
echo
tpm nv_definespace \
-in $TPM_NVRAM_SPACE \
-sz 312 \
-pwdo "$tpm_password" \
-per 0 \
|| die "Unable to define NVRAM space"
tpm nv_writevalue \
-in $TPM_NVRAM_SPACE \
-if "$TOTP_SEALED" \
|| die "Unable to write sealed secret to NVRAM"
fi
shred -n 10 -z -u "$TOTP_SEALED" 2> /dev/null
url="otpauth://totp/$HOST?secret=$secret"
secret=""
qrenc "$url"
echo "$url"