Verifying container image signatures

Digital signatures provide a way for consumers of content to ensure that what they download is both authentic (it originated from the expected source) and has integrity (it is what we expect it to be). All images for the Event Endpoint Management certified container in the IBM Entitled Registry are signed following the approach from Red Hat.

You can use the signature to verify that the images came from IBM when they are pulled onto the system.

Before you begin

  • Ensure that the following command-line tools are installed on your computer. On Linux systems, these images can typically be installed by using the package manager.

  • On the computer where the command-line tools are installed, copy the following text block exactly as shown into a text editor, and save it in a file named event-integration.pub.asc. The following text block represents the Event Endpoint Management-certified container public key in the GNU Privacy Guard (GPG) format:

    -----BEGIN PGP PUBLIC KEY BLOCK-----
    
    mQINBGP9DMgBEADCSPlk3GN4qbs+kHFuYnKR3d25Tpv0w1FR04krE4eJZleGzv9V
    ipZ21ywcKxE9Y9KOseKt4/QT+vsJbmDdrhZQNCqJzxGkL27lS/Dfqc6GfSas3qhY
    Zghmd6+S9Wo4G9oIAAE7/wZcchltoEyYd4/VihuU5uKmcRZ8U/k7+lCMQV2qt0+l
    PgCtyQ6dlbqtwm4gjNeHu6rz69Hk4PA9EN1h2J0yHtiTDYL4wV0tjbh7t6s/WYHW
    KkLbDbXybWdTD7CitcZ3mneXI+ij5N0iB63HIrmVQKaP/bWsuWwaijGGZM+LjUf6
    MRBTjfiqLKrmlnaL2xwo200Z+vHV705et81aOefOLxCE2bqnXnhyMup5NE+U4BVx
    57aTVW4sL03OpSF0Lj+Jms2JjoNtG84qLv2w7XKozhc+yunv7wghnuaubqiAc3tO
    3pHuP92r8IVMcHkFsbGZAJxi891nYthIQAQwUNkvfgVC83y3BdPrxlwUu9qD9nhl
    q56n7c571keXlTQ1fT/Km4o2yhG7JfkpJvvChTVTYx8g+ST4dEgxY3A8tmxTo0ss
    pHBp1f3ry1QAyp72yjobar/xZOB1+O2YBmGHhM1cm4pZNdd7DcxJNYqgP+Y/o83l
    UATX/QUInD1Jjz1aPiCplwd7J3rctEE+TZ1gSLwhLFBKrynOte+GVERO0wARAQAB
    tCZRdWlubmlwaWFjIFByb2R1Y3RzIDxwc2lydEB1cy5pYm0uY29tPokCOgQTAQgA
    JAUCY/0MyAIbDwULCQgHAgYVCgkICwIEFgIDAQIeAQUJAAAAAAAKCRDSz7jRu6g0
    HsY8EAC4nvJW5QPxhSY5oaUtA5bx5KLt4LQ8ib316C0lhZV+YilvkOkcXsfvLdon
    Y61xrp/WBTjzmAm6X7EFypJI33Olo+pBtBq7lOOuwOH8Y/n/BM9qSSzL9EQmqO8r
    rZ3Qk7jsSVLT18NhEX76dC72MnXJwK6p0A+4Gc7UiG1sSOZgi5pqrLWaWlABWVp8
    fVwWVRy7rcQMulJOxD6FRrt/HsIZm0hPQrxeXMLn9pKzKm3DVwSUD91xLjjh+/cQ
    gRpIaV1AYvV8+74d29cBAaNMZigfrbSROfxWtgBpIKuBxCvEdSjzJe6G34Usdg0Q
    Owcm+FHsyk/QTAClSueCz/fpUirYQM2SKweeelhYNQr0gII1P8LF0RpmKJ8I68dn
    sZZI8JlIs0stz+kU4FZLPF+vMwl9Fq6/EJ0tNQcleWiDpH8Gz7hwCbpoLBnWyR0j
    NDZ9xZ8KxUtfdchptja93t0hJpcTs97HyRtgKydguWT3wbvH31U2J+hR45/PQgYE
    UV8yeGx9p2WNi2G4FbPw7f/781RZgZ4ZesTBzQrdZwfyz/brBBv2jWfg6bHmTGh3
    QuRoFeqg9GW3p2QGFIIazDZJ+XHAk7NKNH5m3ao9U/x0g/fth4iUKxIGp4c7A54L
    fROemzTVxd8jHEGGUlgZ6Bi0NdSGOF1htWBDo88XnewLiKNpHw==
    =jPze
    -----END PGP PUBLIC KEY BLOCK-----
    

Obtaining the container images

Obtain the list of Event Endpoint Management-certified container images to verify as described in the following sections.

Prepare your bastion host

Ensure you meet the following prerequisites before downloading the CASE archive and obtaining the images:

  • A computer with internet access on which you can run the required commands. This computer must also have access to the cluster, and is referred to as a bastion host.
  • A cluster that is already set up and running a supported version of the Red Hat OpenShift Container Platform. For more information, see the support matrix for supported versions.
  • A private Docker registry that can be accessed by the cluster and the bastion host, and which will be used to store all images on your restricted network.

If the cluster has a bastion host which has access to the public internet, then the following steps can be performed from the bastion host.

Note: In the absence of a bastion host, prepare a portable device that has access to the public internet to download the CASE archive and images, and also has access to the target registry where the images will be mirrored.

Download the CASE archive

Download the Container Application Software for Enterprises (CASE) archive. This archive, which is typically provided for installing within a restricted network, includes metadata and files that you will require later.

Complete the following steps to download the CASE archive:

  1. Log in to your Red Hat OpenShift Container Platform as a cluster administrator by using the oc CLI (oc login).

  2. Configure the public IBM Cloud-Pak Github repository for downloading the CASE archive:

    oc ibm-pak config repo 'default' -r "https://github.com/IBM/cloud-pak/raw/master/repo/case/" --enable
    
  3. Identify the available Event Endpoint Management CASE versions:

    oc ibm-pak list ibm-eventendpointmanagement
    
  4. Run the following command to download, validate, and extract a specific version of the CASE archive.

    oc ibm-pak get ibm-eventendpointmanagement --version 11.1.5
    

    By default, the CASE will be downloaded and extracted to ~/.ibm-pak/data/cases. The following output is displayed:

    Downloading and extracting the CASE ...
    - Success
    Retrieving CASE version ...
    - Success
    Validating the CASE ...
    Validating the signature for the ibm-eventendpointmanagement CASE...
    - Success
    Creating inventory ...
    - Success
    Finding inventory items
    - Success
    Resolving inventory items ...
    Parsing inventory items
    - Success
    Download of CASE: ibm-eventendpointmanagement, version: 11.1.5 is complete
    
  5. Verify that the CASE archive and images .csv files have been generated for Event Endpoint Management. For example, ensure you have the following files generated for the Event Endpoint Management CASE.

    $ tree ~/.ibm-pak
    
    ├── config
    │   └── config.yaml
    ├── data
    │   ├── cases
    │   │   └── ibm-eventendpointmanagement
    │   │       └── 11.1.5
    │   │           ├── caseDependencyMapping.csv
    │   │           ├── charts
    │   │           ├── component-set-config.yaml
    │   │           ├── ibm-eventendpointmanagement-11.1.5-airgap-metadata.yaml
    │   │           ├── ibm-eventendpointmanagement-11.1.5-charts.csv
    │   │           ├── ibm-eventendpointmanagement-11.1.5-images.csv
    │   │           ├── ibm-eventendpointmanagement-11.1.5.tgz
    │   │           └── resourceIndexes
    │   │               └── ibm-eventendpointmanagement-resourcesIndex.yaml
    │   └── mirror
    └── logs
        └── oc-ibm_pak.log
    
    9 directories, 9 files
    

Obtain the files

Obtain the required files as follows:

  1. After meeting the required prerequisites and downloading the CASE archive, obtain the following files:

    • The downloaded CASE archives, which contain metadata for the container images required to deploy each Event Endpoint Management capability. Each CASE archive also contains the required scripts to mirror images to a private registry, and to configure the target cluster to use the private registry as a mirror.

    • Generated comma-separated value (CSV) files listing the images. Obtain an IBM Entitled Registry entitlement key from the IBM Container software library. The CSV files, combined with your entitlement key, are used for downloading or mirroring the images manually.

    To verify the image signatures for a Event Endpoint Management-certified container, use the file that is named in the format ibm-eventendpointmanagement-<v.r.m>-images.csv, where v.r.m represents the Event Endpoint Management CASE version.

  2. Use a shell script to parse through the CSV file and print out the list of “manifest list images” with their tags. You can use the listed names when pulling and verifying image signatures. In the tail command, ~/.ibm-pak/data/cases represents the default directory where the ibm-pak plugin will download the CASE archive. To list images by tag:

    tail -q -n +2 ~/.ibm-pak/data/cases/ibm-eventendpointmanagement/11.1.5/ibm-eventendpointmanagement-11.1.5-images.csv \
    | while IFS="," read registry image_name tag digest mtype os arch variant insecure digest_source image_type groups; do
    if [[ "$mtype" == "IMAGE" ]]; then
        echo "$registry/$image_name:$tag"
    fi
    done
    

Note: You can also copy the output to a file for ease of reference while verifying the image signatures.

Verifying the signature

To verify the image signatures, complete the following steps:

  1. Import the Event Endpoint Management-certified container public key on the computer where you saved the public key to a file as described in the before you begin section.

    • Run the following command to import the public GPG key:

      gpg --import event-integration.pub.asc
      

    Note: This step needs to be done only once on each computer that you use for signature verification.

  2. Retrieve the fingerprint of the public GPG key.

    • Run the following command:

      fingerprint=$(gpg --fingerprint --with-colons | grep fpr | tr -d 'fpr:')
      

    This command stores the key’s fingerprint in an environment variable called fingerprint, which is needed for the command to verify the signature.

    Note: When you exit your shell session, the variable will be deleted. The next time you log in to your computer, you can set the environment variable again by rerunning the command in this step.

  3. Log in to skopeo to access the entitled registry. Use cp as the username and your entitlement key as the password. For example:

    skopeo login cp.icr.io --username cp --password myEntitlementKey
    
  4. Create a directory (for example, images) for the image. Then use skopeo to pull the image into local storage, where imageName represents the image name.

    mkdir images
    skopeo copy docker://<imageName> dir:./images
    

    For example:

    mkdir images
    skopeo copy docker://icr.io/cpopen/ibm-eventendpointmanagement-operator-catalog:11.1.4 dir:./images
    

    This command downloads the image as a set of files and places them in the images directory, or in a directory that you specified. A manifest file named images/manifest.json, and a set of signature files named images/signature-1, images/signature-2, and images/signature-3 are added to the directory. You will use these files to verify the signature in the next step.

  5. Verify the signature for each required image, where imageName is the name of the image and signature-N relates to a format for the name.

    skopeo standalone-verify ./images/manifest.json <imageName> ${fingerprint} ./images/<signature-N>
    

    For example:

    skopeo standalone-verify ./images/manifest.json icr.io/cpopen/ibm-eventendpointmanagement-operator-catalog:11.1.4 ${fingerprint} ./images/signature-1
    

    You will receive a confirmation similar to the following:

    Signature verified, digest sha256:0000000000000000000000000000000000000000000000000000000000000000