signimage: add a script to show problematic sizes of data to get ...

... signed

This script creates images of various sizes and checks, whether the
signature may be validated by check_signed_image AND by AVM's utility
tr069fwupdate.

It shows some size-related values in cases of differences ... to allow
creation of problematic images, the YF_SIGNIMAGE_SKIP_WORKAROUNDS
option is used in the first pass and in cases of an error, the same
size is used again with activated workarounds. In the second attempt
shouldn't occur errors anymore.

signimage/show_signature_problem

@@ -0,0 +1,99 @@
+#! /bin/sh
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# check for MD5 computation errors from "firmwarecfg", depending on size of data to
+# sign
+#
+# the script needs full-functioning signing and verification from the "signimage"
+# folder and the own public key as "~/firmware_signing.asc"
+#
+# specify the password for the private key as first parameter
+#
+# the script will create image files with one, two and 512 blocks with 4 KB of data
+# to sign and appends from 0 to 7 further blocks, to check every possible count of
+# remaining TAR blocks after the last complete 4 KB block
+#
+# each signed image is tested afterwards - once with the "check_signed_image" script
+# and once more with AVM's tr069fwupdate utility
+#
+# You need an OpenSSL CLI utility and the "hexdump" applet as additions to the
+# original firmware from AVM to run this script successfully.
+#
+check()
+{
+	check_signed_image $1 -a ~/firmware_signing.asc
+}
+sign()
+(
+	[ -z "$3" ] && export YF_SIGNIMAGE_SKIP_WORKAROUNDS=1 || export -n YF_SIGNIMAGE_SKIP_WORKAROUNDS
+	sign_image "$1" "$2"
+)
+pack()
+{
+	tar -c "$*"
+}
+show()
+{
+	size=$(stat -c %s "$1")
+	off=$(hexdump -C "$1" | grep "\./var/signature" | sed -n -e "s|^\([^ ]*\) .*\$|\1|p")
+	sizediff=1024
+	[ "$2" = "Signed" ] && sizediff=$(( sizediff + 1024 ))
+	printf "%s file: size=%d (0x%08x), data to sign=%d (0x%08x)" "$2" $size $size $(( size - sizediff )) $(( size - sizediff ))
+	[ -z $off ] || printf ", signature offset=%s (remainder: %u)" $off $(( ( ( 0x$off - 1024 ) % 4096 ) / 512 ))
+	printf ", TAR blocks remainder - 4K: \033[36m%u\033[0m, 10K: \033[36m%u\033[0m\n" $(( ( ( size - sizediff ) % 4096 ) / 512 )) $(( ( ( size - sizediff ) % 10240 ) / 512 ))
+}
+hash()
+{
+	size=$(stat -c %s "$1")
+	blocks=$(( size / 512 ))
+	md5=$( ( dd if="$1" bs=512 count=$(( blocks - 4 )) 2>/dev/null;dd if=/dev/zero bs=512 count=4 2>/dev/null ) | md5sum | sed -n -e "s|^\([a-f0-9]*\).*\$|\1|p")
+	printf "Hash value: %s\n" $md5
+}
+run()
+{
+	printf "\033[1m\033[31mi=%u j=%u %s\033[0m\n" "$1" "$2" "$([ -n "$3" ] && printf "with workaround while signing")"
+	rm -r /var/packet 2>/dev/null
+	dir="$TMPDIR/test_signature"
+	rm -r "$dir" 2>/dev/null
+	mkdir -p "$dir/var"
+	dd if=/dev/zero of="$dir/var/zeros.bin" bs=512 count=$(( ( $1 * 8 ) - 6 + $2 )) 2>/dev/null
+	cat >"$dir/var/install" <<EOF
+#! /bin/sh
+printf "\033[1m/var/install from signed image file\n======================\n" 1>&2
+printf "\033[1mfirmware_stream_result:\033[0m\n----------------------\n" 1>&2
+cat /var/tmp/firmware_stream_result 1>&2
+printf "\033[1mfwsign.log:\033[0m\n----------\n" 1>&2
+cat /var/tmp/fwsign.log 1>&2
+exit 0
+EOF
+	chmod a+x "$dir/var/install"
+	cd "$dir"
+	pack "./var/" > "$dir/$i.image"
+	show "$dir/$i.image" "Unsigned"
+	sign "$dir/$i.image" "$keypwd" "$3" > "$dir/$i.signed.image" 2>/dev/null
+	show "$dir/$i.signed.image" "Signed"
+	check "$dir/$i.signed.image" 2>/dev/null
+	yf_check=$?
+	hash "$dir/$i.signed.image" 2>/dev/null
+	tr069fwupdate packet "file://$(realpath "$dir")/$i.signed.image" 2>/dev/null
+	avm_check=$?
+	[ $avm_check -eq 0 ] && echo "AVM signature check: $avm_check, YourFritz signature check: $yf_check" || echo -e "\033[1m\033[31mAVM signature check: $avm_check\033[0m, YourFritz signature check: $yf_check \033[31m\033[1mwithout workarounds while signing\033[0m\n"
+	if [ $avm_check -ne 0 ]; then
+		printf "\033[1mfirmware_stream_result\033[0m\n======================\n"
+		cat /var/tmp/firmware_stream_result 2>/dev/null
+		printf "\033[1mfwsign.log\033[0m\n==========\n"
+		head -n 2 /var/tmp/fwsign.log 2>/dev/null
+	fi
+	cd /var
+	rm -r "$dir" 2>/dev/null
+	printf "\n------------------------------------------------\n\n"
+	[ "$avm_check" -ne 0 ] && [ -z "$3" ] && run $1 $2 1
+}
+keypwd="$1"
+mount -o bind ~/firmware_signing.asc /etc/avm_firmware_public_key1
+for i in 1 2 512; do
+	for j in $(seq 8); do
+		run $i $(( j - 1 ))
+	done
+done
+while umount /etc/avm_firmware_public_key1 2>/dev/null; do :; done