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initrd/bin/tpmr: replay PCR values from event log instead of assumming their values
Signed-off-by: Krystian Hebel <krystian.hebel@3mdeb.com>
This commit is contained in:
Krystian Hebel
parent
38dfa73f7c
commit
d1a18f1f83
@ -93,8 +93,8 @@ 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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# Note that PCR 4 needs to be set with the "normal-boot" path value, which is 0.
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dd if=/dev/zero bs="$(tpmr pcrsize)" count=1 status=none >> "$pcrf"
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# Note that PCR 4 needs to be set with the "normal-boot" path value, read it from event log.
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tpmr calcfuturepcr 4 >> "$pcrf"
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if [ "$CONFIG_USB_KEYBOARD" = "y" -o -r /lib/modules/libata.ko -o -x /bin/hotp_verification ]; then
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DEBUG "Sealing TPM disk unlock key with PCR5 involvement (additional kernel modules are loaded per board config)..."
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# Here, we take pcr 5 into consideration if modules are expected to be measured+loaded
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@ -102,11 +102,11 @@ if [ "$CONFIG_USB_KEYBOARD" = "y" -o -r /lib/modules/libata.ko -o -x /bin/hotp_v
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else
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DEBUG "Sealing TPM disk unlock key with PCR5=0 (NO additional kernel modules are loaded per board config)..."
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#no kernel modules are expected to be measured+loaded
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dd if=/dev/zero bs="$(tpmr pcrsize)" count=1 status=none >> "$pcrf"
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tpmr calcfuturepcr 5 >> "$pcrf"
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fi
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# Precompute the value for pcr 6
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DEBUG "Precomputing TPM future value for PCR6 sealing/unsealing of TPM disk unlock key..."
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tpmr calcfuturepcr -a "/tmp/luksDump.txt" "$pcrf"
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tpmr calcfuturepcr 6 "/tmp/luksDump.txt" >> "$pcrf"
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# We take into consideration user files in cbfs
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tpmr pcrread -a 7 "$pcrf"
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@ -30,17 +30,17 @@ dd \
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secret="`base32 < $TOTP_SECRET`"
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pcrf="/tmp/secret/pcrf.bin"
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DEBUG "Sealing TOTP with actual state of PCR0-4)"
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DEBUG "Sealing TOTP with actual state of PCR0-3"
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tpmr pcrread 0 "$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 "$pcrf"
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DEBUG "Sealing TOTP with actual state of PCR4 (Going to recovery shell extends PCR4)"
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DEBUG "Sealing TOTP with boot state of PCR4 (Going to recovery shell extends PCR4)"
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# pcr 4 is expected to either:
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# zero on bare coreboot+linuxboot on x86 (boot mode: init)
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# already extended on ppc64 per BOOTKERNEL (skiboot) which boots heads.
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#We expect the PCR4 to be in the right state at unattended unseal operation
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tpmr pcrread -a 4 "$pcrf"
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# Read from event log to catch both cases, even when called from recovery shell.
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tpmr calcfuturepcr 4 >> "$pcrf"
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# pcr 5 (kernel modules loaded) is not measured at sealing/unsealing of totp
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DEBUG "Sealing TOTP neglecting PCR5 involvement (Dynamically loaded kernel modules are not firmware integrity attestation related)"
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# pcr 6 (drive luks header) is not measured at sealing/unsealing of totp
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163
initrd/bin/tpmr
163
initrd/bin/tpmr
@ -86,45 +86,134 @@ tpm1_pcrread() {
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DO_WITH_DEBUG tpm pcrread -ix "$index" | hex2bin >>"$file"
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}
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# usage: tpmr calcfuturepcr [-a] <input_file> <output_file>
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# Uses the scratch PCR to calculate a future PCR value (TPM2 23, TPM1 16). The
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# data in input file are hashed into a PCR, and the PCR value is placed in
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# output_file.
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# -a: Append to output_file. Default is to overwrite
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tpm2_calcfuturepcr() {
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TRACE "Under /bin/tpmr:tpm2_calcfuturepcr"
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if [ "$1" = "-a" ]; then
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APPEND=y
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shift
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fi
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input_file="$1"
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output_file="$2"
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if [ -z "$APPEND" ]; then
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true >"$output_file"
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fi
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tpm2 pcrreset -Q 23
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DO_WITH_DEBUG tpmr extend -ix 23 -if "$input_file"
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DO_WITH_DEBUG tpm2 pcrread -Q -o >(cat >>"$output_file") sha256:23
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tpm2 pcrreset -Q 23
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# is_hash - Check if a value is a valid hash of a given type
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# usage: is_hash <alg> <value>
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is_hash() {
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# Must only contain 0-9a-fA-F
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if [ "$(echo -n "$2" | tr -d '0-9a-fA-F' | wc -c)" -ne 0 ]; then return 1; fi
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# SHA-1 hashes are 40 chars
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if [ "$1" = "sha1" ] && [ "${#2}" -eq 40 ]; then return 0; fi
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# SHA-256 hashes are 64 chars
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if [ "$1" = "sha256" ] && [ "${#2}" -eq 64 ]; then return 0; fi
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return 1
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}
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tpm1_calcfuturepcr() {
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TRACE "Under /bin/tpmr:tpm1_calcfuturepcr"
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if [ "$1" = "-a" ]; then
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APPEND=y
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# extend_pcr_state - extend a PCR state value with more hashes or raw data (which is hashed)
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# usage:
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# extend_pcr_state <alg> <initial_state> <files/hashes...>
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# alg - either 'sha1' or 'sha256' to specify algorithm
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# initial_state - a hash value setting the initial state
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# files/hashes... - any number of files or hashes, state is extended once for each item
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extend_pcr_state() {
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local alg="$1"
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local state="$2"
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local next extend
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shift 2
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while [ "$#" -gt 0 ]; do
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next="$1"
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shift
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if is_hash "$alg" "$next"; then
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extend="$next"
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else
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extend="$("${alg}sum" <"$next" | cut -d' ' -f1)"
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fi
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state="$(echo "$state$extend" | hex2bin | "${alg}sum" | cut -d' ' -f1)"
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done
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echo "$state"
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}
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# There are 3 (and a half) possible formats of event log, each of them requires
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# different arguments for grep. Those formats are shown below as heredocs to
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# keep all the data, including whitespaces:
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# 1) TPM2 log, which can hold multiple hash algorithms at once:
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: << 'EOF'
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TPM2 log:
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Specification: 2.00
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Platform class: PC Client
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TPM2 log entry 1:
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PCR: 2
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Event type: Action
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Digests:
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SHA256: de73053377e1ae5ba5d2b637a4f5bfaeb410137722f11ef135e7a1be524e3092
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SHA1: 27c4f1fa214480c8626397a15981ef3a9323717f
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Event data: FMAP: FMAP
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EOF
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# 2) TPM1.2 log (aka TCPA), digest is always SHA1:
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: << 'EOF'
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TCPA log:
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Specification: 1.21
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Platform class: PC Client
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TCPA log entry 1:
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PCR: 2
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Event type: Action
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Digest: 27c4f1fa214480c8626397a15981ef3a9323717f
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Event data: FMAP: FMAP
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EOF
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# 3) coreboot-specific format:
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# 3.5) older versions printed 'coreboot TCPA log', even though it isn't TCPA
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: << 'EOF'
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coreboot TPM log:
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PCR-2 27c4f1fa214480c8626397a15981ef3a9323717f SHA1 [FMAP: FMAP]
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EOF
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# awk script to handle all of the above. Note this gets squashed to one line so
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# semicolons are required.
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AWK_PROG='
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BEGIN {
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getline;
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hash_regex="([a-fA-F0-9]{40,})";
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if ($0 == "TPM2 log:") {
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RS="\n[^[:space:]]";
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pcr="PCR: " pcr;
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alg=toupper(alg) ": " hash_regex;
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} else if ($0 == "TCPA log:") {
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RS="\n[^[:space:]]";
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pcr="PCR: " pcr;
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alg="Digest: " hash_regex;
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} else if ($0 ~ /^coreboot (TCPA|TPM) log:$/) {
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pcr="PCR-" pcr;
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alg=hash_regex " " toupper(alg) " ";
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} else {
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print "Unknown TPM event log format:", $0 > "/dev/stderr";
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exit -1;
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}
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}
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$0 ~ pcr {
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match($0, alg);
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print gensub(alg, "\\1", "g", substr($0, RSTART, RLENGTH));
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}
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'
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# usage: replay_pcr <alg> <pcr_num> [ <input_file>|<input_hash> ... ]
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# Replays PCR value from CBMEM event log. Note that this contains only the
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# measurements performed by firmware, without those performed by Heads (USB
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# modules, LUKS header etc). First argument is PCR number, followed by optional
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# hashes and/or files extended to given PCR after firmware. Resulting PCR value
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# is returned in binary form.
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replay_pcr() {
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TRACE "Under /bin/tpmr:replay_pcr"
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if [ -z "$2" ] ; then
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>&2 echo "No PCR number passed"
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return
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fi
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input_file="$1"
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output_file="$2"
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if [ -z "$APPEND" ]; then
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true >"$output_file"
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if [ "$2" -ge 8 ] ; then
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>&2 echo "Illegal PCR number ($2)"
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return
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fi
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DO_WITH_DEBUG tpm calcfuturepcr -ix 16 -if "$input_file" | hex2bin >>"$output_file"
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local log=`cbmem -L`
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local alg="$1"
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local pcr="$2"
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local alg_digits=0
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# SHA-1 hashes are 40 chars
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if [ "$alg" = "sha1" ] ; then alg_digits=40; fi
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# SHA-256 hashes are 64 chars
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if [ "$alg" = "sha256" ] ; then alg_digits=64; fi
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shift 2
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extend_pcr_state $alg $(printf "%.${alg_digits}d" 0) \
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$(echo "$log" | awk -v alg=$alg -v pcr=$pcr -f <(echo $AWK_PROG)) \
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$@ | hex2bin
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}
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tpm2_extend() {
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@ -575,7 +664,7 @@ if [ "$CONFIG_TPM2_TOOLS" != "y" ]; then
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pcrsize)
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echo "$PCR_SIZE";;
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calcfuturepcr)
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shift; tpm1_calcfuturepcr "$@";;
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shift; replay_pcr "sha1" "$@";;
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seal)
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shift; tpm1_seal "$@";;
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startsession)
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@ -606,7 +695,7 @@ case "$subcmd" in
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pcrsize)
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echo "$PCR_SIZE";;
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calcfuturepcr)
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tpm2_calcfuturepcr "$@";;
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replay_pcr "sha256" "$@";;
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extend)
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tpm2_extend "$@";;
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counter_read)
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