Extract private and public key from Java KeyStore file (JKS)

extract_from_jks.sh

JKS=mykeystore
JKS_PASS=changeit
JKS_ALIAS=tomcat
OUTPASS=$(cat /dev/urandom |env LC_CTYPE=C tr -dc 'a-zA-Z0-9' | fold -w 8 |head -n1)
PK12_KEY=mykeystore.pk12
PEM=server.pem
KEY=server.key

keytool -importkeystore -srckeystore $JKS -destkeystore $PK12_KEY -srcstoretype JKS -deststoretype PKCS12 -srcstorepass $JKS_PASS -deststorepass $OUTPASS -srcalias $JKS_ALIAS -destalias $JKS_ALIAS -srckeypass $JKS_PASS -destkeypass $OUTPASS -noprompt

#generate password-less pem file
openssl pkcs12 -in $PK12_KEY -passin pass:$OUTPASS  -passout pass:$OUTPASS |openssl rsa -passin pass:$OUTPASS -pubout -out $PEM
#generate password-less private-key file
openssl pkcs12 -in $PK12_KEY   -passin pass:$OUTPASS -passout pass:$OUTPASS |openssl rsa  -passin pass:$OUTPASS -out $KEY