How to validate Attestation Key name in Platform Certificate

This process uses the Endorsement Key's public key to verify that the TPM holds the attestation key, which is identified by the name in the Platform Certificate.

# Extract public key from EK certificate and platform certificate
openssl x509 -pubkey -noout -in ek.crt > ek-public-key.pem
# Extract AK Name from Platform Certificate
ak_name=$(\
  openssl x509 -noout -text -in device-platform-certificate.crt | \
  grep -A 1 '1.3.6.1.4.1.42518.4.2.1.1.1.20' | tail -n 1 | \
  tr -d ' ' | sed 's/^.D//'
)

# Create a nonce (challenge)
echo "$RANDOM" > nonce.txt
# Create TPM credential using nonce as secret (challenge)
tpm2_makecredential -Q \
  -T none \
  -u ek-public-key.pem \
  -s "nonce.txt" \
  -n "$ak_name" \
  -o "credential.out" \
  -G rsa

# credential conversion to base64
credential_base64="$(cat credential.out | base64)"
# EK/TPM challenge
curl -s -X POST \
   "https://nodegrid/api/v1/system/platformcertificate/challenge" \
  --insecure \
  -H "Content-Type: text/plain" \
  -H 'accept: application/json' \
  -H "ticket: ${ticket}" \
  -d "$credential_base64" | \
  jq . > response.json

# check if replied nonce matches with nonce.txt
jq -r .data.nonce response.json | base64 -d > device-nonce.txt
cmp nonce.txt device-nonce.txt && echo "EK was successfully challenged"
#EK was successfully challenged