vgmoose/fetch_img.sh

## fetch_img.sh
URL="https://dl.google.com/dl/android/aosp/ryu-opm4.171019.021.n1-factory-1f31fdce.zip"
TMP="tmp.zip"
OUT="output.zip"

# fetch the important "PK" region from the remote zip by specifying offsets*
curl --header "Range: bytes=1842-3820027" -k $URL > $TMP

# restore "corrupted" zip data (answer yes to question it prompts)
echo y | zip -FF $TMP --out $OUT

# extract from fixed zip
unzip $OUT

# to find this "PK" region, it will have to be discovered ahead of time, but it corresponds to
#  the region of the zip file between two stretches of "PK" headers (0x504B01) that contain the
#  filename of the target file to be extracted (in this case, they surround the first instance
#  the string "bootloader-dragon-google_smaug.7900.126.0.img" appears in the HEX)

# to understand this better, you can look at the region from the curl command in a hex
# editor for the above URL, as they are hardcoded for that zip (in hex, offsets: 0x732 - 0x3a49fb)
	URL="https://dl.google.com/dl/android/aosp/ryu-opm4.171019.021.n1-factory-1f31fdce.zip"
	TMP="tmp.zip"
	OUT="output.zip"

	# fetch the important "PK" region from the remote zip by specifying offsets*
	curl --header "Range: bytes=1842-3820027" -k $URL > $TMP

	# restore "corrupted" zip data (answer yes to question it prompts)
	echo y \| zip -FF $TMP --out $OUT

	# extract from fixed zip
	unzip $OUT

	# to find this "PK" region, it will have to be discovered ahead of time, but it corresponds to
	# the region of the zip file between two stretches of "PK" headers (0x504B01) that contain the
	# filename of the target file to be extracted (in this case, they surround the first instance
	# the string "bootloader-dragon-google_smaug.7900.126.0.img" appears in the HEX)

	# to understand this better, you can look at the region from the curl command in a hex
	# editor for the above URL, as they are hardcoded for that zip (in hex, offsets: 0x732 - 0x3a49fb)