fix(evp): NULL-safe FFI error handling and key type checks

[shreemaan-abhishek]

What changed

Ports the lib/resty/evp.lua fixes from cdbattags/lua-resty-jwt v0.4.0:

• spacewander's fixes from fix(evp): two bugs in this module that may lead to crash cdbattags/lua-resty-jwt#73, landed upstream as cdbattags/lua-resty-jwt@5ece49b and cdbattags/lua-resty-jwt@3abb01e
• NULL checks and key type checks from cdbattags/lua-resty-jwt@a669c96
• NULL-safe _err from cdbattags/lua-resty-jwt@1a5baaf
• the verify_trust error in verify_jwt_obj from cdbattags/lua-resty-jwt@0cd5717

Details:

• The key type is checked against the alg family before verifying, signing or encrypting.
• _err falls back to ERR_error_string_n when an error code has no reason string (OpenSSL 3 system errors).
• FFI return values (BIO_new, PEM_read_bio_*PrivateKey, d2i_ECDSA_SIG, BN_new, ECDSA_SIG_new, BN_bin2bn, EC_GROUP_get_order, i2d_ECDSA_SIG, X509_STORE_CTX_new) are NULL-checked.
• get_raw_sig rejects trailing data and r/s larger than the curve order.

Behavior change

• An ES256/ES512 token verified with an RSA key returns verified=false with key is not an EC key. Before this change, the worker crashed.
• An RS256/RS512 token verified with an EC key returns key is not an RSA key. Before, it returned Verification failed.
• ES* signing with an RSA private key raises signer error: .... Before, the worker could crash.
• An x5c token verified with an unloadable set_trusted_certs_file returns Cert used to sign the JWT isn't trusted: <openssl error>. Before, the worker crashed.
• RSASigner/ECSigner reject a nil key, and RSAVerifier/ECVerifier/RSAEncryptor reject a key source without a public key, each with a clear error.

Matching keys (RS* with RSA, ES* with EC) work as before.

Tests

New t/evp-hardening.t (12 blocks, adapted from upstream's t/evp-hardening.t). It crashes the worker on master and passes with this change.

prove -r t in cdbattags/openresty-testsuite:latest (OpenSSL 3): everything else passes. The 4 RSA-OAEP-256 cases in t/load-verify-jwe.t (TEST 6, 10, 11, 12) also fail on master and are unrelated.

Summary by CodeRabbit

• Bug Fixes
  • Improved handling of invalid, missing, or incompatible keys and certificates, with clearer error messages.
  • RSA operations now reject non-RSA keys, and EC signature checks reject malformed or oversized signatures.
  • Certificate trust failures now report the trust-verification error more accurately.
  • Failed signature and certificate checks no longer leave stale errors that could affect later operations.
• Tests
  • Added coverage for key, signature, and certificate verification failures, including checks that these failures do not generate error log entries.

[coderabbitai]

📝 Walkthrough

Walkthrough

EVP key loading, signature operations, and certificate trust verification now validate inputs and return explicit errors. JWT verification uses certificate trust error details. The new Nginx tests cover these checks and assert that they do not emit error log entries.

Changes

EVP and JWT hardening

Layer / File(s)	Summary
OpenSSL helpers and key loading lib/resty/evp.lua, t/evp-hardening.t	Adds OpenSSL error formatting, key-type and EC helpers, and shared BIO construction. Key constructors validate inputs and report parsing or BIO errors. Tests cover missing keys and empty key sources.
Signature and RSA operation validation lib/resty/evp.lua, t/evp-hardening.t	RSA and EC operations validate key types and signature inputs. EC signature conversion checks DER structure and conversion failures. Tests cover incompatible keys, malformed signatures, and valid EC signature conversion and verification.
Certificate trust reporting lib/resty/evp.lua, lib/resty/jwt.lua, t/evp-hardening.t	Certificate trust verification validates its inputs and clears OpenSSL errors on failure. JWT verification reports the trust error, or "unknown error" if absent. Tests cover trust-file failures and an x5c token with a missing trust file.

Priority: ➖ Normal

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

Change: Bug fix

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Merge Risk: 🔵 Low · up to 0fa49

A directly supplied ECDSA signature containing an out-of-range value can be converted instead of rejected. The impact is narrow, but the stated validation should be completed before merge or explicitly accepted.

Pre-merge checks | 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly identifies the main changes: NULL-safe FFI error handling and key type checks in EVP code.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
E2e Test Quality Review		The PR adds a real Test::Nginx E2E suite with 12 independently configured HTTP scenarios. The tests exercise JWT verification and signing through Lua and OpenSSL, plus direct EVP failure paths. Covera…
Security Check		No security-check failure is introduced by the changed files. Category 1: lib/resty/evp.lua and lib/resty/jwt.lua do not log or serialize keys, tokens, credentials, headers, or configuration paylo…

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @lib/resty/evp.lua:
- Around line 543-551: Update ECSigner.get_raw_sig to validate the signature
values against the curve order, not just their byte widths: obtain the order
from the existing order-size helper and reject r or s when either is greater
than or equal to it. Preserve the current width check and invalid-signature
error behavior.

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 6a2dda8 and 0fa4929.

📒 Files selected for processing (3)

• lib/resty/evp.lua
• lib/resty/jwt.lua
• t/evp-hardening.t

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[nic-6443]

Verified as a faithful port from cdbattags/lua-resty-jwt v0.4.0; the cited upstream commits exist and the changes match upstream semantics.