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59 lines
1.8 KiB
Bash
Executable File
59 lines
1.8 KiB
Bash
Executable File
#!/bin/bash
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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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TRACE "Under /bin/seal-totp"
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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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TPM_PASSWORD="$2"
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TOTP_SECRET="/tmp/secret/totp.key"
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TOTP_SEALED="/tmp/secret/totp.sealed"
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dd \
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if=/dev/urandom \
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of="$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 < $TOTP_SECRET`"
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pcrf="/tmp/secret/pcrf.bin"
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DEBUG "Sealing TOTP with actual state of PCR0-4)"
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tpmr pcrread 0 "$pcrf"
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tpmr pcrread -a 1 "$pcrf"
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tpmr pcrread -a 2 "$pcrf"
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tpmr pcrread -a 3 "$pcrf"
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DEBUG "Sealing TOTP with actual state of PCR4 (Going to recovery shell extends PCR4)"
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# pcr 4 is expected to either:
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# zero on bare coreboot+linuxboot on x86 (boot mode: init)
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# already extended on ppc64 per BOOTKERNEL (skiboot) which boots heads.
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#We expect the PCR4 to be in the right state at unattended unseal operation
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tpmr pcrread -a 4 "$pcrf"
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# pcr 5 (kernel modules loaded) is not measured at sealing/unsealing of totp
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DEBUG "Sealing TOTP neglecting PCR5 involvement (Dynamically loaded kernel modules are not firmware integrity attestation related)"
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# pcr 6 (drive luks header) is not measured at sealing/unsealing of totp
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DEBUG "Sealing TOTP without PCR6 involvement (LUKS header consistency is not firmware integrity attestation related)"
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# pcr 7 is containing measurements of user injected stuff in cbfs
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tpmr pcrread -a 7 "$pcrf"
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tpmr seal "$TOTP_SECRET" "$TPM_NVRAM_SPACE" 0,1,2,3,4,7 "$pcrf" 312 "" "$TPM_PASSWORD" \
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|| die "Unable to write sealed secret to NVRAM"
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shred -n 10 -z -u "$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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