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