synta 0.2.0

ASN.1 parser, decoder, and encoder library with DER/BER support and C FFI
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# 9. `example_pkcs7.py` — PKCS#7 certificate bundles

[← Example index](index.md) · [example_pkcs7.py on Codeberg](https://codeberg.org/abbra/synta/src/branch/main/examples/example_pkcs7.py)

Bindings: `load_der_pkcs7_certificates`, `load_pem_pkcs7_certificates`.

- Load a `.p7b` file and print the subject of each extracted certificate.
- Demonstrate PEM-encoded PKCS#7 with `load_pem_pkcs7_certificates`.
- Show `ValueError` for non-PKCS#7 input.

## Source

```python
#!/usr/bin/env python3
"""
Example 8: PKCS#7 certificate bundles.

Demonstrates: load_der_pkcs7_certificates, load_pem_pkcs7_certificates.

Test vectors: tests/vectors/test_bundle.p7b  (1 cert)
              tests/vectors/test_bundle_2certs.p7b  (2 certs)
"""

import pathlib
import synta

VECTORS = pathlib.Path(__file__).parent.parent / "tests" / "vectors"


def section(title):
    print(f"\n{'─' * 60}\n{title}\n{'─' * 60}")


def demo_load_der_p7b_single():
    section("load_der_pkcs7_certificates — single certificate")
    path = VECTORS / "test_bundle.p7b"
    if not path.exists():
        print(f"  Skipped: {path} not found")
        return
    data = path.read_bytes()
    certs = synta.load_der_pkcs7_certificates(data)
    print(f"  Loaded {len(certs)} certificate(s)")
    for i, cert in enumerate(certs):
        print(f"  [{i}] subject={cert.subject}  sig_alg={cert.signature_algorithm}")


def demo_load_der_p7b_multi():
    section("load_der_pkcs7_certificates — two certificates")
    path = VECTORS / "test_bundle_2certs.p7b"
    if not path.exists():
        print(f"  Skipped: {path} not found")
        return
    data = path.read_bytes()
    certs = synta.load_der_pkcs7_certificates(data)
    print(f"  Loaded {len(certs)} certificate(s)")
    for i, cert in enumerate(certs):
        print(f"  [{i}] subject={cert.subject}")
    assert len(certs) == 2


def demo_load_pem_p7b():
    section("load_pem_pkcs7_certificates — PEM-encoded PKCS#7")
    path = VECTORS / "test_bundle.p7b"
    if not path.exists():
        print(f"  Skipped: {path} not found")
        return
    # Convert the DER p7b to PEM so we can exercise load_pem_pkcs7_certificates
    der_data = path.read_bytes()
    pem_data = synta.der_to_pem(der_data, "PKCS7")

    certs_from_pem = synta.load_pem_pkcs7_certificates(pem_data)
    certs_from_der = synta.load_der_pkcs7_certificates(der_data)
    assert len(certs_from_pem) == len(certs_from_der)
    print(f"  PEM and DER loaders both return {len(certs_from_pem)} cert(s): OK")
    for i, cert in enumerate(certs_from_pem):
        print(f"  [{i}] {cert.subject}")


def demo_invalid_input():
    section("ValueError for non-PKCS#7 input")
    try:
        synta.load_der_pkcs7_certificates(b"\x30\x03\x02\x01\x01")
        print("  No error raised (unexpected)")
    except ValueError as e:
        print(f"  ValueError: {e}")


def main():
    print("=" * 60)
    print("Example 8: PKCS#7 certificate bundles")
    print("=" * 60)
    demo_load_der_p7b_single()
    demo_load_der_p7b_multi()
    demo_load_pem_p7b()
    demo_invalid_input()
    print("\nAll PKCS#7 examples completed.")


if __name__ == "__main__":
    main()
```