.NET MAUI: How Can I Dynamically Update the Barcode for an Apple Wallet .pkpass?

Below is an outline of the process you need to follow each time you want to change (for example) the barcode message and produce a signed pass file. Apple Wallet passes aren’t “signed” in one step by calling an API—instead, you create your pass bundle, update the pass.json as needed, regenerate the manifest, sign that manifest with your pass certificate and private key, and then zip everything together into a .pkpass file.

Below are the main steps:

1. Update Your pass.json
   Edit your pass.json file (or template) with the new barcode message and any other dynamic data. Make sure that the JSON conforms to the PassKit specification.

2. Create a Manifest File
   The manifest is a JSON file mapping every file name in your pass bundle (pass.json, images, etc.) to its SHA‑1 hash. For example, you can write a script that iterates over the files and calculates their SHA‑1 digest:

   BASHCopied
   #!/bin/bash
   manifest="{}"
   for file in $(find . -type f | sed 's|./||'); do
       # ignore the manifest and signature files if already present
       if [[ "$file" == "manifest.json" || "$file" == "signature" ]]; then
           continue
       fi
       hash=$(shasum -a 1 "$file" | cut -d ' ' -f1)
       manifest=$(echo "$manifest" | jq --arg key "$file" --arg value "$hash" '. + {($key): $value}')
   done
   echo "$manifest" > manifest.json

   (You can use any method to generate a JSON dictionary matching filenames to their SHA‑1 hash.)

3. Sign the Manifest
   Using your PassTypeID certificate (and the associated private key), sign the manifest to produce a detached signature. Before you do this, export your certificate and key as PEM files (and include the intermediate certificate if needed). Then use OpenSSL with the smime command. For example:

   BASHCopied
   openssl smime -binary -sign \
       -signer certificate.pem \
       -inkey key.pem \
       -in manifest.json \
       -out signature \
       -outform DER \
       -nodetach

   Be sure that:

   • Your certificate and private key have been exported in the correct PEM format.
   • If required, you include the Apple intermediate certificate (by appending it to your certificate.pem file or using the -certfile option).

   This command produces a binary file called “signature” that is part of your pass bundle.

4. Package the .pkpass File
   Once you have your updated pass.json, manifest.json, signature, and any other resources (images, logos, etc.), zip them together with no directory structure. For example:

   BASHCopied
   zip -r pass.pkpass *.json signature *.png

   This zip file is the .pkpass file you serve to your users.

5. Automate the Process on Your Backend
   Since you need to update the barcode (or other details) for every new pass instance, your backend should:

   • Update a pass.json template with the new data.
   • Recreate the manifest file.
   • Run the OpenSSL command to sign the manifest.
   • Zip the entire bundle to generate a new .pkpass file.

   Many developers use libraries or custom scripts to automate these steps—there’s no provided Apple framework to “modify barcode and sign on the fly.” Instead, follow the documented manual signing process.

Troubleshooting Tips

• Certificate Format:
  Make sure your certificate and private key are in the correct formats. If needed, convert your .p12 file to PEM:

  BASHCopied
  openssl pkcs12 -in yourfile.p12 -out key_cert.pem -nodes

  Then split out the certificate and key from that file.

• Intermediate Certificate:
  Include the Apple intermediate certificate when signing if required. This may involve appending the intermediate certificate to your certificate file or using the -certfile option.

• Environment:
  Confirm that the Linux environment has all required dependencies (such as OpenSSL and any necessary JSON tools like jq) and that security permissions on your keys are properly set.

By following this process every time you update the barcode message in pass.json, you can generate a new, valid .pkpass file to use with Apple Wallet.