Merge pull request #1758 from tlaurion/improve_tpm_basic_instrospection

Improve TPM extend ops output in normal and DEBUG mode

Author: tlaurion

boards/qemu-coreboot-whiptail-tpm2/qemu-coreboot-whiptail-tpm2.config

@@ -17,10 +17,10 @@ CONFIG_LINUX_CONFIG=config/linux-qemu.config
 #export CONFIG_HAVE_GPG_KEY_BACKUP=y
 
 #Enable DEBUG output
-export CONFIG_DEBUG_OUTPUT=y
-export CONFIG_ENABLE_FUNCTION_TRACING_OUTPUT=y
+#export CONFIG_DEBUG_OUTPUT=y
+#export CONFIG_ENABLE_FUNCTION_TRACING_OUTPUT=y
 #Enable TPM2 pcap output under /tmp
-export CONFIG_TPM2_CAPTURE_PCAP=y
+#export CONFIG_TPM2_CAPTURE_PCAP=y
 
 #On-demand hardware support (modules.cpio)
 CONFIG_LINUX_USB=y

initrd/bin/cbfs-init

@@ -15,17 +15,19 @@ cbfsfiles=`cbfs -t 50 -l 2>/dev/null | grep "^heads/initrd/"`
 for cbfsname in `echo $cbfsfiles`; do
 	filename=${cbfsname:12}
 	if [ ! -z "$filename" ]; then
-		echo "Loading $filename from CBFS"
 		mkdir -p `dirname $filename` \
 		|| die "$filename: mkdir failed"
-		cbfs -t 50 -r $cbfsname > "$filename" \
+		echo "Extracting CBFS file $cbfsname into $filename"
+		cbfs -t 50 $CBFS_ARG -r $cbfsname > "$filename" \
 		|| die "$filename: cbfs file read failed"
 		if [ "$CONFIG_TPM" = "y" ]; then
-			TMPFILE=/tmp/cbfs.$$
-			echo "$filename" > $TMPFILE
-			cat $filename >> $TMPFILE
-			DEBUG "Extending TPM PCR $CONFIG_PCR with $filename"
-			tpmr extend -ix "$CONFIG_PCR" -if $TMPFILE \
+			TRACE_FUNC
+			echo "TPM: Extending PCR[$CONFIG_PCR] with $filename"
+			# Measure both the filename and its content.  This
+			# ensures that renaming files or pivoting file content
+			# will still affect the resulting PCR measurement.
+			tpmr extend -ix "$CONFIG_PCR" -ic "$filename"
+			tpmr extend -ix "$CONFIG_PCR" -if "$filename" \
 			|| die "$filename: tpm extend failed"
 		fi
 	fi

initrd/bin/flash.sh

@@ -48,9 +48,9 @@ flash_rom() {
       dd if=/tmp/pchstrp9.bin bs=1 count=4 seek=292 of=/tmp/${CONFIG_BOARD}.rom conv=notrunc >/dev/null 2>&1
     fi
 
-    warn "Do not power off computer.  Updating firmware, this will take a few minutes..."
+    warn "Do not power off computer.  Updating firmware, this will take a few minutes"
     flashrom $CONFIG_FLASHROM_OPTIONS -w /tmp/${CONFIG_BOARD}.rom 2>&1 \
-      || die "$ROM: Flash failed"
+      || recovery "$ROM: Flash failed"
   fi
 }
 

initrd/bin/kexec-insert-key

@@ -65,7 +65,8 @@ if ! kexec-unseal-key "$INITRD_DIR/secret.key"; then
 fi
 
 # Override PCR 4 so that user can't read the key
-DEBUG "Extending TPM PCR 4 to prevent further secret unsealing"
+TRACE_FUNC
+echo "TPM: Extending PCR[4] to prevent any future secret unsealing"
 tpmr extend -ix 4 -ic generic ||
 	die 'Unable to scramble PCR'
 

initrd/bin/kexec-select-boot

@@ -384,9 +384,10 @@ while true; do
 	if [ "$CONFIG_TPM" = "y" ]; then
 		if [ ! -r "$TMP_KEY_DEVICES" ]; then
 			# Extend PCR4 as soon as possible
-			DEBUG "Extending TPM PCR 4 to prevent further secret unsealing"
+			TRACE_FUNC
+			DEBUG "TPM: Extending PCR[4] to prevent further secret unsealing"
 			tpmr extend -ix 4 -ic generic ||
-				die "Failed to extend PCR 4"
+				die "Failed to extend TPM PCR[4]"
 		fi
 	fi
 

initrd/bin/qubes-measure-luks

@@ -19,6 +19,7 @@ sha256sum /tmp/lukshdr-* >/tmp/luksDump.txt || die "Unable to hash LUKS headers"
 DEBUG "Removing /tmp/lukshdr-*"
 rm /tmp/lukshdr-*
 
-DEBUG "Extending TPM PCR 6 with hash of LUKS headers from /tmp/luksDump.txt"
+TRACE_FUNC
+echo "TPM: Extending PCR[6] with hash of LUKS headers from /tmp/luksDump.txt"
 tpmr extend -ix 6 -if /tmp/luksDump.txt ||
 	die "Unable to extend PCR"

initrd/bin/tpmr

@@ -29,11 +29,11 @@ else
 	. /etc/config
 fi
 
-TRACE_FUNC
 
 # Busybox xxd lacks -r, and we get hex dumps from TPM1 commands.  This converts
 # a hex dump to binary data using sed and printf
 hex2bin() {
+	TRACE_FUNC
 	sed 's/\([0-9A-F]\{2\}\)/\\\\\\x\1/gI' | xargs printf
 }
 
@@ -43,6 +43,7 @@ hex2bin() {
 # as a file still chokes if the password begins with 'hex:', oddly tpm2-tools
 # accepts 'hex:' in the file content.)
 tpm2_password_hex() {
+	TRACE_FUNC
 	echo "hex:$(echo -n "$1" | xxd -p | tr -d ' \n')"
 }
 
@@ -61,7 +62,7 @@ tpm2_pcrread() {
 
 	if [ -z "$APPEND" ]; then
 		# Don't append - truncate file now so real command always
-		# appends
+		# overwrites
 		true >"$file"
 	fi
 
@@ -79,7 +80,7 @@ tpm1_pcrread() {
 
 	if [ -z "$APPEND" ]; then
 		# Don't append - truncate file now so real command always
-		# appends
+		# overwrites
 		true >"$file"
 	fi
 
@@ -100,11 +101,12 @@ is_hash() {
 
 # extend_pcr_state - extend a PCR state value with more hashes or raw data (which is hashed)
 # usage:
-# extend_pcr_state <alg> <initial_state> <files/hashes...>
+# extend_pcr_state <alg> <state> <files/hashes...>
 # alg - either 'sha1' or 'sha256' to specify algorithm
-# initial_state - a hash value setting the initial state
+# state - a hash value setting the initial state
 # files/hashes... - any number of files or hashes, state is extended once for each item
 extend_pcr_state() {
+	TRACE_FUNC
 	local alg="$1"
 	local state="$2"
 	local next extend
@@ -233,14 +235,20 @@ tpm2_extend() {
 	while true; do
 		case "$1" in
 		-ix)
+			# store index and shift so -ic and -if can be processed
 			index="$2"
 			shift 2
 			;;
 		-ic)
+			string=$(echo -n "$2")
 			hash="$(echo -n "$2" | sha256sum | cut -d' ' -f1)"
+			TRACE_FUNC
+			DEBUG "TPM: Will extend PCR[$index] with hash of string $string"
 			shift 2
 			;;
 		-if)
+			TRACE_FUNC
+			DEBUG "TPM: Will extend PCR[$index] with hash of file content $2"
 			hash="$(sha256sum "$2" | cut -d' ' -f1)"
 			shift 2
 			;;
@@ -250,7 +258,10 @@ tpm2_extend() {
 		esac
 	done
 	tpm2 pcrextend "$index:sha256=$hash"
-	DO_WITH_DEBUG tpm2 pcrread "sha256:$index"
+	tpm2 pcrread "sha256:$index"
+
+	TRACE_FUNC
+	DEBUG "TPM: Extended PCR[$index] with hash $hash"
 }
 
 tpm2_counter_read() {
@@ -348,9 +359,9 @@ tpm2_startsession() {
 		die "tpm2_flushcontext: unable to flush saved session"
 	tpm2 readpublic -Q -c "$PRIMARY_HANDLE" -t "$PRIMARY_HANDLE_FILE"
 	#TODO: do the right thing to not have to suppress "WARN: check public portion the tpmkey manually" see https://github.com/linuxboot/heads/pull/1630#issuecomment-2075120429
-	tpm2 startauthsession -Q -c "$PRIMARY_HANDLE_FILE" --hmac-session -S "$ENC_SESSION_FILE" 2>&1 > /dev/null
+	tpm2 startauthsession -Q -c "$PRIMARY_HANDLE_FILE" --hmac-session -S "$ENC_SESSION_FILE" > /dev/null 2>&1
 	#TODO: do the right thing to not have to suppress "WARN: check public portion the tpmkey manually" see https://github.com/linuxboot/heads/pull/1630#issuecomment-2075120429
-	tpm2 startauthsession -Q -c "$PRIMARY_HANDLE_FILE" --hmac-session -S "$DEC_SESSION_FILE" 2>&1 > /dev/null
+	tpm2 startauthsession -Q -c "$PRIMARY_HANDLE_FILE" --hmac-session -S "$DEC_SESSION_FILE" > /dev/null 2>&1
 	tpm2 sessionconfig -Q --disable-encrypt "$DEC_SESSION_FILE"
 }
 
@@ -381,6 +392,7 @@ cleanup_shred() {
 # tpm2_destroy: Destroy a sealed file in the TPM.  The mechanism differs by
 # TPM version - TPM2 evicts the file object, so it no longer exists.
 tpm2_destroy() {
+	TRACE_FUNC
 	index="$1" # Index of the sealed file
 	size="$2"  # Size of zeroes to overwrite for TPM1 (unused in TPM2)
 
@@ -396,6 +408,7 @@ tpm2_destroy() {
 # TPM version - TPM1 overwrites the file with zeroes, since this can be done
 # without authorization.  (Deletion requires authorization.)
 tpm1_destroy() {
+	TRACE_FUNC
 	index="$1" # Index of the sealed file
 	size="$2"  # Size of zeroes to overwrite for TPM1
 
@@ -761,6 +774,21 @@ if [ "$CONFIG_TPM2_TOOLS" != "y" ]; then
 		shift
 		tpm1_destroy "$@"
 		;;
+	extend)
+		#check if we extend with a hash or a file
+		if [ "$4" = "-if" ]; then
+			DEBUG "TPM: Will extend PCR[$3] hash content of file $5"
+			hash="$(sha1sum "$5" | cut -d' ' -f1)"
+		elif [ "$4" = "-ic" ]; then
+			string=$(echo -n "$5")
+			DEBUG "TPM: Will extend PCR[$3] with hash of filename $string"
+			hash="$(echo -n "$5" | sha1sum | cut -d' ' -f1)"
+		fi
+		
+		TRACE_FUNC
+		DEBUG "TPM: Extending PCR[$3] with hash $hash"
+		DO_WITH_DEBUG exec tpm "$@"
+		;;
 	seal)
 		shift
 		tpm1_seal "$@"
@@ -799,6 +827,8 @@ calcfuturepcr)
 	replay_pcr "sha256" "$@"
 	;;
 extend)
+	TRACE_FUNC
+	DEBUG "TPM: Extending PCR[$2] with $4"
 	tpm2_extend "$@"
 	;;
 counter_read)

initrd/etc/ash_functions

@@ -241,7 +241,8 @@ recovery() {
 	DEBUG "Board $CONFIG_BOARD - version $(fw_version)"
 
 	if [ "$CONFIG_TPM" = "y" ]; then
-		DEBUG "Extending TPM PCR 4 for recovery shell access"
+		TRACE_FUNC
+		echo "TPM: Extending PCR[4] to prevent any further secret unsealing"
 		tpmr extend -ix 4 -ic recovery
 	fi
 

initrd/sbin/insmod

@@ -28,7 +28,7 @@ fi
 #  Unify lsmod output to use - instead of _ for comparison
 module_name=$(basename "$MODULE" | sed 's/_/-/g' | sed 's/\.ko$//')
 if lsmod | sed 's/_/-/g' | grep -q "^$module_name\\b"; then
-	DEBUG "$MODULE: already loaded"
+	DEBUG "$MODULE: already loaded, skipping"
 	exit 0
 fi
 
@@ -39,18 +39,22 @@ if [ ! -r /sys/class/tpm/tpm0/pcrs -o ! -x /bin/tpm ]; then
 fi
 
 if [ -z "$tpm_missing" ]; then
-	DEBUG "Extending TPM PCR $MODULE_PCR with $MODULE prior of usage"
-	tpmr extend -ix "$MODULE_PCR" -if "$MODULE" \
-	|| die "$MODULE: tpm extend failed"
-fi
-
-if [ ! -z "$*" -a -z "$tpm_missing" ]; then
-	DEBUG "Extending TPM PCR $MODULE_PCR with $*"
-	TMPFILE=/tmp/insmod.$$
-	echo "$@" > $TMPFILE
-	DEBUG "Extending TPM PCR $MODULE_PCR with $MODULE prior of usage"
-	tpmr extend -ix "$MODULE_PCR" -if $TMPFILE \
-	|| die "$MODULE: tpm extend on arguments failed"
+	echo "TPM: Extending PCR[$MODULE_PCR] with $MODULE and parameters '$*' before loading"
+	# Extend with the module parameters (even if they are empty) and the
+	# module. Changing the parameters or the module content will result in a
+	# different PCR measurement.
+	if [ -n "$*" ]; then
+		TRACE_FUNC
+		DEBUG "Extending with module parameters and the module's content"
+		tpmr extend -ix "$MODULE_PCR" -ic "$*"
+		tpmr extend -ix "$MODULE_PCR" -if "$MODULE" \
+		|| die "$MODULE: tpm extend failed"
+	else
+		TRACE_FUNC
+		DEBUG "No module parameters, extending only with the module's content"
+		tpmr extend -ix "$MODULE_PCR" -if "$MODULE" \
+		|| die "$MODULE: tpm extend failed"
+	fi
 fi
 
 # Since we have replaced the real insmod, we must invoke