pysapsso2

A pure python library for generating SAP Assertion/Logon tickets.

SAP Logon Tickets are authentication tokens accepted by :

• SAP NetWeaver ABAP (SAP GUI, Webdynpro/Fiori, Web Services)
• SAP NetWeaver Java (Web)

This library is an opensource alternative to SAPSSOEXT (304450 - Single-Sign-On with SAP logon tickets in non-SAP systems)

Installation

pip install pysapsso2

How to generate an SAP shortcut

cf. examples/generate_shortcut.py

How to parse an SAP Logon Ticket

from pysapsso2 import SapTicket

ticket = SapTicket.from_b64(cookie_value)
print(ticket.user, ticket.source_sid, ticket.source_client, ticket.expires_at)

How to verify an SAP Logon Ticket

from pysapsso2 import SapTicket, SapTicketHandler

ticket = SapTicket.from_b64(cookie_value)
handler = SapTicketHandler("SSO", "000", certificate=trusted_cert_pem)
handler.verify(ticket)  # raises SignatureError / CertificateError

verify() checks, in order:

1. the payload digest against the message_digest signed attribute,
2. that the ticket names the supplied certificate as its signer,
3. that the certificate is within its validity period (check_certificate_validity=False to skip, at_time= to pin the moment),
4. the signature over the signed attributes.

The certificate must come from the caller. A ticket may embed a certificate, but anybody can embed one they hold the key for, so it is never used as a trust anchor. pysapsso2.crypto.get_dsa_key() exposes the embedded key for inspection only.

Signing algorithms

Every combination in the table was accepted by a live SAP NetWeaver ABAP system.

DSA with sha1 is the default, because that is what SAPSSOEXT emits. Use it if you need a ticket that SAPSSOEXT can also read. Otherwise prefer RSA or ECDSA with sha256.

Pick the algorithm on the handler:

from Crypto.PublicKey import RSA
from pysapsso2 import SapTicketHandler

handler = SapTicketHandler(
    "SSO",
    "000",
    private_key=RSA.import_key(key_pem),
    certificate=cert_pem,
    digest_algorithm="sha256",
)
ticket = handler.new("DEMOUSER")

digest_algorithm defaults to "sha1". The handler picks the signer from the key type. You can also build the signer yourself with pysapsso2.DsaSigner, pysapsso2.RsaSigner or pysapsso2.signer_for_key() and pass it as private_key; the handler's digest_algorithm is then ignored, because the signer carries its own.

Verification needs no configuration. verify() reads the digest algorithm from the ticket and the key algorithm from the certificate.

Development

This project uses uv.

# Create the virtualenv and install the project with its dev dependencies
uv sync

# Run the tests / linter
uv run pytest
uv run ruff check

# Run an example
uv run examples/generate_shortcut.py

# Build the sdist and wheel
uv build

tests/keys/ holds throwaway self-signed keys, one pair per row of the algorithm matrix. They are committed, so a clone runs the suite straight away. To replace them, or to add a key size or curve, run pwsh tools/make_test_keys.ps1 -Force. It needs openssl; on Windows it falls back to the one shipped with Git.

sapsso2.key and sapsso2.crt are the exception: the script never touches them. That key signed the SAPSSOEXT reference ticket pinned in tests/test_sapticket.py, so a regenerated key would not verify that signature.

Further reading

• docs/sapssoext.md — developer notes: signing a ticket with SAPSSOEXT itself, and running the interop suite (uv run pytest -m oracle) against it.
• docs/interop.md records what SAP actually does with a ticket, measured rather than quoted: which keys and digests each consumer signs and validates, the DSA subgroup rule, the error pairs, and the validity and base64 behaviour.