opensaml

Pure-Rust SAML 2.0 Service Provider and Identity Provider support. The protocol layer uses Rust XML parsing and does not require libxml2, xmlsec1, or an OpenSSL build chain. XML cryptography (XML-DSig, XML-Enc, C14N, detached message signatures) is delegated to bergshamra behind the default crypto-bergshamra feature.

[dependencies]
opensaml = "0.1"

# Crypto-free protocol layer only:
# opensaml = { version = "0.1", default-features = false }

This package is a maintained compatibility re-export. Its Rust import path is opensaml.

Why opensaml?

opensaml is aimed at applications that need SAML SP/IdP flows without a C XML security stack in their build and deployment environment.

Compared with samael, the main tradeoff is deployment shape: samael is the established Rust SAML crate and commonly uses the native xmlsec stack, while opensaml keeps the SAML protocol path Rust-only and delegates XML crypto to a Rust crate.

What you can do

Unsupported SAML profiles

The high-level Saml API currently focuses on browser Web SSO, metadata-driven SP/IdP setup, XML signature/encryption through bergshamra, and Single Logout. It does not yet implement Artifact resolution, SOAP/back-channel profiles, ECP/PAOS, SAML query protocols, NameID management, or metadata federation. If you need one of those profiles for a real interoperability target, please open an issue with the profile, binding, IdP/SP product, and a minimal expected flow so we can consider the implementation.

Quick Start

The primary API is the typed Saml facade. Build local SP/IdP configuration with SpConfig::builder and IdpConfig::builder, import peer metadata into typed descriptors, and keep the returned Pending<_> value with your browser session while the SAML round trip is in flight.

Runnable typed SSO

A signed SP -> IdP -> SP round trip is available as an executable example:

cargo run -p opensaml --example sso

Source: examples/sso.rs.

The repository also includes a typed Single Logout walkthrough in examples/slo.rs and a low-level compatibility walkthrough in examples/raw_compat.rs.

The crate-root docs contain doctested fragments for the typed Saml facade, including Saml<Sp>::start_sso, Saml<Sp>::finish_sso, Saml<Idp>::receive_sso, and Saml<Sp>::finish_slo. Those rustdoc snippets are compiled by cargo test --doc; the README stays as an entry point and links to the complete examples above.

Service Provider SSO flow

1. Build local SP state with SpConfig::builder and Saml::sp.
2. Import peer IdP metadata into IdpDescriptor.
3. Start SSO with sp.start_sso(...) and store started.pending with the browser session.
4. In the ACS handler, pass the posted response fields and the matching pending value to sp.finish_sso(...).

See examples/sso.rs for a complete signed SP -> IdP -> SP round trip and the doctested crate-root SSO fragment for the compact API shape.

Identity Provider - receive and respond

The IdP side mirrors the SP flow: import peer SP metadata into SpDescriptor, parse an AuthnRequest with idp.receive_sso(...), then produce a typed browser response with idp.respond_sso(...). The complete path is exercised in examples/sso.rs, and the short rustdoc version is in the Identity Provider flows crate-root section.

Single Logout

Typed Single Logout starts from session.logout_subject(), stores the PendingLogoutRequest, and finishes only with the matching LogoutResponse. Peer-initiated logout uses Received<LogoutRequest> rather than free-form request ID strings. See examples/slo.rs for the complete typed walkthrough and the doctested SLO fragment for the compact shape.

Metadata

Metadata trust is explicit. The rustdoc Metadata trust section describes production-shaped signed metadata validation with pinned certificates. MetadataTrustPolicy::UnsignedForCompatibility is available for legacy interoperability, but it is a compatibility exception rather than a production default.

The compact rustdoc flow snippets use ReplayPolicy::DisabledForCompatibility only to keep examples dependency-free. Production inbound validation should use ReplayPolicy::RequireCache with a caller-owned replay cache and the retention guidance in SamlValidationContext.

Advanced/raw compatibility

The low-level compatibility API remains available under opensaml::raw for callers that need direct access to ServiceProvider, IdentityProvider, HttpRequest, BindingContext, or protocol helper functions. New browser SSO/SLO integrations should start with Saml, typed descriptors, and the builder-backed config types shown above. Use visible docs.rs modules, crate-root re-exports, and opensaml::raw before reaching for hidden lower-level module paths.

Features

[features]
default = ["crypto-bergshamra"]
crypto-bergshamra = ["dep:bergshamra"]

With default-features = false, the protocol layer still builds messages, parses metadata, and runs extraction. Operations that need signing, verification, or encryption return OpenSamlError::Unsupported.

The default crypto-bergshamra feature currently requires Rust 1.85 because the bergshamra 0.6.3 dependency graph reaches kryptering 0.4.1 and crypto-bigint 0.7.5, which declares Rust 1.85.

With crypto-bergshamra enabled:

• XML signatures can be verified against metadata-declared keys.
• Signed-reference placement checks help mitigate XML Signature Wrapping (XSW).
• XML-Enc support is available, but software RSA key-transport decryption is gated off by default and requires an explicit compatibility opt-in through XmlEncryptionPolicy.

Security

opensaml is pre-1.0 and has not had an external security audit. Review the crate, configuration, and peer metadata trust model before production use.

Security-sensitive defaults and checks include:

• #![forbid(unsafe_code)] on the crate root.
• DOCTYPE / XXE rejection and bounded XML parsing before authentication.
• XML escaping for generated templates, metadata endpoint locations, and SAML attribute values.
• Response validation for issuer, SAML status, assertion time window, audience, destination/recipient, bearer subject confirmation, and InResponseTo.
• Logout validation for issuer and request/response correlation.
• Signed metadata verification with root coverage requirements.
• AuthnRequest root-signature coverage when signed requests are required.
• Detached Redirect/SimpleSign signatures bound to the fields consumed by the flow parser.
• HTTP-Redirect raw DEFLATE output limits.
• XML-Enc software RSA key-transport decryption disabled by default because the bundled RustCrypto RSA backend, reached through bergshamra / kryptering, is affected by RUSTSEC-2023-0071.

Schema validation is optional defense in depth via context::set_schema_validator.

Development

cargo fmt --all --check
cargo clippy -p opensaml --all-targets -- -D warnings
cargo nextest run -p opensaml
cargo test -p opensaml --doc
RUSTDOCFLAGS="-D warnings -D missing_docs" cargo doc -p opensaml --lib --all-features --no-deps
cargo test -p opensaml --doc --no-default-features
cargo check -p opensaml --no-default-features

License

MIT.