Podman# Attestation

Attestation is a process that starts by default at virtual instance creation, ensures that the virtual server instance image is indeed built by IBM, and that it was not modified. This process also provides information and allows validation of any data that is provided to the instance at the time of deployment.

When you create a virtual server instance by using the IBM Hyper Protect Container Runtime (HPCR) image, the image uses an initial file system that is protected by encryption and signed by IBM Secure Execution (SE). For more information, see Confidential computing with LinuxONE. To know more about the attestation process, see this video.

The boot process creates a unique root disk encryption key to ensure protection of the root disk. To perform attestation, the virtual server instance image contains an attestation-signing key and the hash of the root partition at build time. The boot process validates the root partition. If the hash of the root partition does not match, the boot process does not continue because it assumes that the image was modified before boot. The attestation signing key is a random RSA 4 K key that is signed by an IBM root key that is maintained in Hyper Protect Crypto Services. The IBM root key is signed by Digicert.

During deployment of the virtual server instance, an attestation record is created. It contains hashes of the following items:

• The original base image
• The root partition at the moment of the first boot
• The root partition at build time
• The cloud initialization options

The attestation record is signed by the attestation key. As an extra protection layer, you can provide a public key during deployment, against which the attestation record is encrypted. The hash of this public key is added to the attestation record to ensure that the record can be viewed only by the compliance authority, and the expected authority can be easily identified through that hash.

Before you upload any workload to your instance, you need to validate the attestation record. After an instance is created, you can validate the attestation record within the created instance. Your instance must have access to the /var/hyperprotect directory. If so, follow these procedures:

• The attestation record is signed by the attestation signing key.
• The attestation signing key can be confirmed by the IBM intermediate certificate. The IBM intermediate certificate is signed by DigiCert, which is proven by the root certificate of DigiCert, thus completing the chain of trust.

The encryption and attestation certificates are signed by the IBM intermediate certificate and this has been signed by the IBM Digicert intermediate cert (which in turn is signed by DigiCert Trusted Root G4). For more information about the certificates, see DigiCert Trusted Root Authority Certificates.

Use the following procedure to validate the attestation record and hashes:

• Obtain the attestation record se-checksums.txt and the signature file se-signature.bin from your IBM Hyper Protect Virtual Servers instance. To do so, you can implement your container to provide the attestation record and the signature file. The attestation record and the signature file are made available to your container in the /var/hyperprotect directory.

• Get the IBM attestation certificate that is a part of the image TAR file.

• Validate the attestation certificate by following the instructions here.

• Extract the encryption public key from the encryption certificate by using the following command:

   openssl x509 -pubkey -noout -in ibm-hyper-protect-container-runtime-23.11.0-attestation.crt > contract-public-key.pub
  

• Verify the signature of the attestation record:

  openssl sha256 -verify contract-public-key.pub -signature se-signature.bin se-checksums.txt
  

  Note: Signature verification must be done on a decrypted attestation file.

• You can now use the hashes from the attestation record for validation.

In case you provided a public key for encrypting the attestation record, the following script might help in decrypting the record.

#!/bin/bash
#
# Example script to decrypt attestation document.
#
# Usage:
#   ./decrypt-attestation.sh <rsa-priv-key.pem> [file]
#
# Token Format:
#   hyper-protect-basic.<ENC_AES_KEY_BASE64>.<ENC_MESSAGE_BASE64>


RSA_PRIV_KEY="$1"
if [ -z "$RSA_PRIV_KEY" ]; then
    echo "Usage: $0 <rsa-priv-key.pem>"
    exit 1
fi
INPUT_FILE="${2:-se-checksums.txt.enc}"
TMP_DIR="$(mktemp -d)"
#trap 'rm -r $TMP_DIR' EXIT


PASSWORD_ENC="${TMP_DIR}/password_enc"
MESSAGE_ENC="${TMP_DIR}/message_enc"


# extract encrypted AES key and encrypted message
cut -d. -f 2 "$INPUT_FILE"| base64 -d > "$PASSWORD_ENC"
cut -d. -f 3 "$INPUT_FILE"| base64 -d > "$MESSAGE_ENC"

# decrypt password
PASSWORD=$(openssl pkeyutl -decrypt -inkey "$RSA_PRIV_KEY" -in "$PASSWORD_ENC")


# decrypt message
echo -n "$PASSWORD" | openssl aes-256-cbc -d -pbkdf2 -in "$MESSAGE_ENC" -pass stdin --out se-checksums.txt

In the case of a docker container, the decrypt-attestation.sh file can be accessed by mounting /var/hyperprotect in the docker container. For example,

 volumes:
      - "/var/hyperprotect/:/var/hyperprotect/:ro"

In the case of a Podman container, the decrypt-attestation.sh file can be accessed by mounting /var/hyperprotect in the Podman container. For example,

 volumeMounts:
     - name: attestation
       readOnly: true
       mountPath: /var/hyperprotect:Z,U

/var/hyperprotect
|-- cidata
|   |-- meta-data
|   |-- user-data
|   `-- vendor-data
|-- README
|-- se-checksums.txt[.enc]
|-- se-signature.bin
|-- se-commit-id
|-- se-version
`-- user-data.decrypted

sha256sum <file>

1.0.0
Machine Type/Plant/Serial: 3932/02/860A8
71ea00241774e638085af4dc95f9b157ffd6c7bc0e604583cc1e6722ade6f181 baseimage
2d290fcafca295cd2de49e7246a5a5a080f503cb066d451b008a863b84a82ee1 root.tar.gz
2d43b2ffeb1c543d3b3a5b0b96d5417f79d8245f1e085f5e3f150390d093fc6b /dev/disk/by-label/cidata
6dc2640b909f4077b17059f3edc1d0f3c1d286f4afc9f3d28f9ee9e72509ca51 cidata/meta-data
272aa3529571b4fc592bf89e9242d3f57ae8ff29fb514c4ee6d7ce1eeb2ac1ee cidata/user-data
baef972e58d4362d97f822d8ff4c5339c5898a0dc184d88d29e5b010b9835ed6 cidata/vendor-data
d388326d90583b2140831e821311aedaee1ad4b4e721b458f8769d3f9267b0dc attestationPublicKey

15cacfc3dbe3a87a72954bb1a524075a73ef799da07ddbc7abf2bc7a69b267e5 baseimage

817642e8a0886c8535128cc70cf881172eb1a49e7f6ce9be1a9142c0faf892d9 root.tar.gz

 volumes:
      - "/var/hyperprotect/:/var/hyperprotect/:ro"

 volumeMounts:
     - name: attestation
       readOnly: true
       mountPath: /var/hyperprotect:Z,U