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poor-smime-sign

A very poor tool to generate S/MIME signatures for arbitrary content & probably insecurely too.

A quick example:

>>> smime_sign(
...     signer_cert_path="/path/to/files/signer.cert",
...     signer_key_path="/path/to/files/signer.pem",
...     recipient_cert_path="/path/to/files/recipient.cert",
...     content="test",
...     output_format="PEM",
... )

Features

  • Does S/MIME signatures.
  • Verifies S/MIME signatures.

Why?

This utility library has single purpose - provide support for making S/MIME signatures on Python2 and 3, which currently lacks any proper libraries for that purpose.

The main use case it is built for: at work our system has to generate Apple Passbook Pass files, which include an S/MIME signature. Currently it is done using M2Crypto.SMIME. While that works - we want to migrate to Python3, and unfortunately for us M2Crypto is not fully supported. smime_sign is a poor man's solution for this problem.

Internally this does nothing more than call openssl smime, so you might want to see its docs too.

Why not?

  • This may be insecure.
  • This may be slow if you are signing large blobs of text.

API

smime_sign(signer_cert_path, signer_key_path, cert_path, recipient_cert_path, content, output_format)

Generates and returns signature string for content in output_format.

All *_path arguments must be absolute paths.

content must be a string, not a path.

Example to generate signature for Passbook manifest:

>>> manifest_json = "..."  # JSON string with `manifest.json` content
>>> signature = smime_sign(
...     signer_cert_path="/path/to/files/signer.cert",
...     signer_key_path="/path/to/files/signer.pem",
...     cert_path="/path/to/files/intermediate.cert",
...     recipient_cert_path=None,
...     content=manifest_json,
...     output_format="DER",
... )

smime_verify(signer_cert_path, content_path, signature_path, signature_format)

Verifies a content_path file against a signature at signature_path.

Note: this function was added to help in the tests only.

Credits

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