[codex] cap SAML SLO message inflation

[salasebas]

Summary

• Add a configurable SAML SLO logout message size limit.
• Bound both encoded SLO payloads and inflated Redirect binding XML before parsing or signature verification.
• Return 413 SAML_LOGOUT_MESSAGE_TOO_LARGE for oversized LogoutRequest/LogoutResponse messages.
• Add regression coverage for compact DEFLATE payloads that expand past the configured cap.

Root Cause

SAML SLO Redirect binding messages were decoded and inflated from attacker-controlled SAMLRequest/SAMLResponse values before any effective size limit or signature enforcement. A small compressed payload could expand into a much larger XML document and consume CPU/memory before rejection.

Validation

• cargo fmt --all --check
• cargo nextest run -p rustauth-saml --all-features
• cargo nextest run -p rustauth-sso --all-features
• cargo clippy --workspace --all-targets --all-features -- -D warnings

Notes

This branch is based on origin/main so it does not include the local AGENTS.md commit/change.

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Project	Deployment	Actions	Updated (UTC)
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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Bound the raw SAML payload before compaction

In deployments relying on max_logout_message_size as the SLO input cap, this guard runs only after encoded.split_whitespace().collect::<String>(), so an oversized SAMLRequest/SAMLResponse is fully scanned and copied before being rejected; if the excess is mostly whitespace, the compacted value can also remain below the cap and bypass this encoded-length check entirely. Check the raw length first or compact with a bounded accumulator so the new limit actually bounds attacker-controlled request work.

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