fix: read a signing publicCert given as bare base64, and document that it needs a certificate

[cjbarth]

Closes #605.

When signing, publicCert has one job: supplying the certificate for KeyInfo. The default getKeyInfoContent looked only for PEM CERTIFICATE messages, so a certificate given as bare base64 was dropped, even though toPem(value, "CERTIFICATE") and getCertFromKeyInfo() both read that form. The README also described the signing publicCert as "your public key", which produces no KeyInfo at all.

Changes

• When publicCert holds no PEM certificate, getKeyInfoContent reads it as the bare base64 of one certificate. It publishes the value if Node's X509Certificate reads it as exactly one certificate. For anything else it returns null, as before: this fallback catches its own errors, so no configuration that signs today throws. The PEM path keeps its existing errors.
• A Buffer is read as text, as getKeyInfoContent already read one and as Node's crypto reads a Buffer key.
• In the README's signing options, publicCert is now described as a certificate or a chain of them. It can be given as PEM or as one certificate's base64 without the PEM boundaries, in a String or Buffer. A value that holds no certificate produces no KeyInfo. The README requires no chain order, because XMLDSig 4.5.4 says "No ordering is implied" among an X509Data's certificates.
• No warning. See below.

Result

publicCert	6.3.0	this branch
PEM certificate	KeyInfo	KeyInfo
PEM public key	none	none
PEM private key	none	none
bare base64 of a certificate	none	KeyInfo
"not a certificate"	none	none
KeyObject	none	none
bare base64 of a private key	none	none
bare base64 of a certificate with more bytes after it	none	none
Buffer of bare base64 text	none	KeyInfo
Buffer of DER	none	none

A signature made with a bare-base64 publicCert verifies through SignedXml.getCertFromKeyInfo.

What stays with Node

Node's X509Certificate decides whether the bare base64 holds a certificate. The base64 check stays here: Node reads a certificate only from PEM or DER, and Buffer.from(value, "base64") silently drops characters it doesn't recognize, which is what #603 fixed.

The fallback is an internal bareCertificate(), which reads base64 given without boundaries as exactly one certificate. It refuses PEM outright rather than passing it through, so a key can't come out of it as a certificate. It parses the certificate as often as the PEM path does: two X509Certificate calls, the check #603 requires. toPem() is unchanged.

No warning

The issue left a warning to review. It isn't here: KeyInfo is optional (XMLDSig 4.5), so signing without one is valid output, and making it an error was already declined as adding nothing to security or function. A warning for something that shouldn't throw is code to maintain for no gain. It was built in one commit and removed in a later one, so the net diff has none of it.

Tests

These cover the issue's rows at the SignedXml boundary:

• PEM certificate: the existing "adds X509Certificate element during signature".
• PEM public key and KeyObject: existing tests in "omits KeyInfo when there is no content for it".
• PEM private key, "not a certificate", the bare base64 of a private key, and the bare base64 of a certificate with more data after it: added to that describe. The last two aren't in the issue's table. They stop the new path from publishing a key, or a certificate with trailing bytes, as an X509Certificate.
• Bare base64 of a certificate, on one line, wrapped, and as a Buffer: "publishes a publicCert given as the base64 of a certificate, without boundaries". Before the fix it failed with expected [] to deeply equal [ Array(1) ], meaning no certificate was published.

Each safety property has a test that fails when it is broken. I checked this by mutating the code: skipping the certificate check, passing PEM through, or accepting bytes after the certificate each fail a test.

npm run build, npm test (433 passing), and npm run lint all pass.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Added support for publishing a single X.509 certificate from boundary-less base64 input, including values with line breaks.
  • Certificate handling now accepts PEM strings and buffers while ignoring unsupported or invalid certificate data.

• Bug Fixes

  • Prevented private keys, malformed certificate data, and certificate data with trailing bytes from producing <KeyInfo>.

• Documentation

  • Clarified supported publicCert formats and when <KeyInfo> is omitted.

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• README.md
• src/signed-xml.ts
• src/utils.ts
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📝 Walkthrough

Walkthrough

publicCert now accepts boundary-less Base64 certificates for KeyInfo. Certificate-free values omit KeyInfo without warnings. Documentation, parsing logic, and regression tests cover these behaviors.

Changes

Certificate publishing

Layer / File(s)	Summary
Certificate input and publishing src/utils.ts, src/signed-xml.ts, README.md	bareCertificate validates and canonicalizes one Base64 X.509 certificate. SignedXml publishes valid PEM or bare Base64 certificates and omits KeyInfo for other values. The README documents these inputs and removes the signing-certificate-first requirement.
Certificate handling regression tests test/signature-unit-tests.spec.ts	Tests verify that private keys, public keys, key Base64, and arbitrary strings omit KeyInfo. Tests also verify publication of boundary-less certificate Base64 with and without newlines.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Low

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant SignedXml
  participant utils
  participant KeyInfo
  Caller->>SignedXml: provide publicCert
  SignedXml->>utils: validate PEM or bare Base64 certificate
  utils-->>SignedXml: return certificate or no certificate
  alt certificate found
    SignedXml->>KeyInfo: publish certificate
  else no certificate
    SignedXml-->>Caller: omit KeyInfo
  end

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Suggested reviewers: shunkica

Merge Risk: 🟡 Moderate · up to 5d0fe

Signing can fail when callers provide a malformed PEM-like publicCert, even though invalid certificate content is intended to omit optional KeyInfo and allow signing to continue. This should be fixed before merge.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 3 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The pull request meets the coding requirements in #605. README.md documents publicCert as an X.509 certificate or certificate chain in PEM or bare base64 form. certificatesToPublish accepts bare…
Out of Scope Changes check	✅ Passed	The changes stay within #605. The new certificate helper supports the required signing behavior and related verification parsing. The documentation and regression tests support the same objective. No …
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main changes: accepting bare base64 certificates for signing publicCert and documenting the certificate requirement.

Full details: Docstring Coverage

Explanation

Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 3 files. (1 skipped: 1 unsupported.)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.85%. Comparing base (6c4ac70) to head (5cb753c).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #610      +/-   ##
==========================================
+ Coverage   82.67%   82.85%   +0.18%     
==========================================
  Files           9        9              
  Lines        1183     1196      +13     
  Branches      296      298       +2     
==========================================
+ Hits          978      991      +13     
  Misses        121      121              
  Partials       84       84              

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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:
In `@src/signed-xml.ts`:
- Line 52: Update the certificate parsing flow around utils.pemCertificates and
utils.bareCertificate so both operations execute within the same try block.
Preserve returning parsed PEM certificates when available, fall back to the bare
certificate parser otherwise, and return an empty array from the catch block for
either parsing failure so signing can omit optional KeyInfo.

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