generate JWT token

jwt.sh

#!/usr/bin/env bash
set -e

# see https://techdocs.akamai.com/iot-token-access-control/reference/generate-jwt-rsa-keys

PRIVATE_KEY_PEM="$1"

b64encode() {
  echo -n "$*" | base64 -w 0 | sed s/\+/-/ | sed -E s/=+$//
}

sign() {
  echo -n "$*" | openssl dgst -sha256 -binary -sign "$PRIVATE_KEY_PEM"  | openssl enc -base64 | tr -d '\n=' | tr -- '+/' '-_'
}

header='{
  "alg": "RS256",
  "typ": "JWT"
}'

iat=$(date +%s)
exp=$(expr $iat + 600)
payload=$(cat - <<EOF
{
  "jti": "$(uuidgen)",
  "iat": $iat,
  "exp": $exp
}
EOF
)

content=$(echo -n "$(b64encode $header).$(b64encode $payload)")
echo $header
echo $payload
echo "$content.$(sign $content)"