Verify Google Play In-app billing receipt in command line using OpenSSL

verify_receipt.sh

# Convert base64 string from Google to a pem file
openssl enc -base64 -d -in publickey.base64 -A | openssl rsa -inform DER -pubin > public.pem
 
# Decode base64 signature to binary
openssl base64 -d -A -in signature.txt -out signature.sha1
 
# Verify signature
openssl dgst -sha1 -verify public.pem -signature signature.sha1 receipt.json