ssl: retain WebPKI-selected certificate chains by youknowone · Pull Request #8653 · RustPython/RustPython

youknowone · 2026-09-05T09:27:39Z

get_verified_chain() currently extends the peer's chain by matching issuer names. With two CAs sharing a subject but using different keys, it can report the wrong root and expose that certificate through get_ca_certs() after a capath handshake. It also reads the mutable SSLContext when the chain is requested.

Port Pyre's VerifiedChainBuilder approach: retain each connection's verification inputs, rebuild the path with WebPKI, and cache the selected leaf/intermediates/root. Publish the selected capath anchor on both client and server connections, with the certificate's actual CA classification. Keep verification inputs alongside cached configurations and explicit sessions so a declined resumption uses the same configuration that rustls verifies against. Resumed sessions report no new verified chain, matching CPython; CERT_NONE still attempts chain construction without making failure fatal.

The helper is independent of Python objects. Host I/O remains in rustpython-host_env; path selection belongs to the TLS backend. #8648 already supplies hashed-directory filtering and connection-time loading, which this change builds on. Outgoing certificate-chain auto-completion is unchanged.

Validation on macOS:

Workspace Rust tests, including eight new chain regressions; C-API tests run separately from crates/capi.
Workspace and C-API clippy; existing unrelated compiler-source warnings remain.
Release test_ssl: 196 tests, 43 skips. Also ran the three certificate-chain tests separately because their enclosing PHA class is skipped on rustls.
BIO checks against CPython 3.14 for context replacement, capath statistics, explicitly trusted leaves, CERT_NONE, mutual TLS, and accepted/declined session resumption.
Repository pre-commit hooks.

Implementation and validation assisted by Codex (GPT-6).

Summary by CodeRabbit

Bug Fixes
- Improved TLS certificate-chain verification to accurately preserve and report the complete verified chain.
- Improved trust-anchor matching for more reliable certificate validation.
- Added stronger handling for trusted leaf certificates, revocation checks, and client certificate authentication.
- Improved behavior across resumed and unverified TLS connections.
Security
- Enhanced Rustls-based TLS validation using full certificate data rather than issuer-name matching alone.

Port the connection-owned chain builder from Pyre. Preserve verification inputs with TLS configurations and sessions, report the WebPKI-selected path, and publish only its selected capath anchor. Match CPython chain reporting for CERT_NONE and resumed sessions. Assisted-by: Codex:GPT-6

coderabbitai · 2026-09-05T09:31:45Z

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📥 Commits

Reviewing files that changed from the base of the PR and between dde7d24 and d112860.

⛔ Files ignored due to path filters (1)

Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (5)

Cargo.toml
crates/stdlib/Cargo.toml
crates/stdlib/src/ssl.rs
crates/stdlib/src/ssl/chain.rs
crates/stdlib/src/ssl/compat.rs

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📝 Walkthrough

Walkthrough

The SSL backend adds full certificate-chain verification with rustls-webpki. TLS configurations now retain chain builders, sockets store verified paths, and sessions preserve the builder for resumed connections.

Changes

TLS verified-chain support

Layer / File(s)	Summary
Verified chain construction `Cargo.toml`, `crates/stdlib/Cargo.toml`, `crates/stdlib/src/ssl.rs`, `crates/stdlib/src/ssl/chain.rs`	Adds `VerifiedChainBuilder` with server-auth, client-auth, unverified, revocation, trusted-leaf, and full-DER trust-anchor handling.
TLS configuration wiring `crates/stdlib/src/ssl/compat.rs`, `crates/stdlib/src/ssl.rs`	Client and server configuration builders retain chain builders with root certificates, DER certificates, CRLs, and verification settings.
Handshake and session chain state `crates/stdlib/src/ssl.rs`	Sockets record verified chains after handshakes, publish selected anchors, handle resumed sessions, and return stored chains. Sessions retain the chain builder.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: ⚪ Minimal · up to d1128

This change records the WebPKI-selected verified TLS certificate path per connection, including accurate anchor handling and resumed-session behavior. No concrete current-head merge blocker remains.

Suggested reviewers: joshuamegnauth54, shaharnaveh

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 64.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 25 functions across 3 files. (2 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: retaining the certificate chains selected by WebPKI during SSL verification.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 64.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 25 functions across 3 files. (2 skipped: 2 unsupported.)

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Port the connection-owned chain builder from Pyre. Preserve verification inputs with TLS configurations and sessions, report the WebPKI-selected path, and publish only its selected capath anchor. Match CPython chain reporting for CERT_NONE and resumed sessions. Assisted-by: Codex:GPT-6

youknowone mentioned this pull request Sep 5, 2026

ssl: add key logging with a shared host append sink #8655

Merged

youknowone merged commit a8aa383 into RustPython:main Sep 5, 2026
28 of 29 checks passed

youknowone deleted the ssl-verified-chain branch September 5, 2026 10:35

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ssl: retain WebPKI-selected certificate chains - #8653

ssl: retain WebPKI-selected certificate chains#8653
youknowone merged 1 commit into
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youknowone:ssl-verified-chain

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youknowone commented Sep 5, 2026 •

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