x509asn1: fix DH public key parameter extraction

[sergio-correia]

The dh(g) parameter was read from param->beg instead of from the cursor p returned by parsing dh(p). This caused dh(g) to always report the same value as dh(p) when inspecting DH certificates via CURLOPT_CERTINFO on non-OpenSSL backends.

The DSA branch correctly advances the cursor; the DH branch lost this during what appears to be a copy-paste.

Add unit1676 to verify that dh(p) and dh(g) report distinct values using a hand-crafted minimal DER certificate.

[Copilot]

Pull request overview

This PR fixes DH parameter extraction in the ASN.1 certificate info parser so that dh(g) is read from the correct cursor position (instead of re-reading dh(p)), restoring correct CURLOPT_CERTINFO output on non-OpenSSL backends that use lib/vtls/x509asn1.c.

Changes:

• Fix cursor usage when extracting DH g parameter in do_pubkey() for dhpublicnumber.
• Add unit1676 with a minimal DER certificate to ensure dh(p), dh(g), and dh(pub_key) are extracted distinctly.
• Register the new unit test in the unit and test-data makefiles.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
lib/vtls/x509asn1.c	Fixes DH g element parsing to use the advanced cursor returned after parsing p.
tests/unit/unit1676.c	Adds a unit test exercising the DH public key parsing path via Curl_extract_certinfo().
tests/unit/Makefile.inc	Includes unit1676.c in the unit test build list.
tests/data/test1676	Adds the test case definition for the new unit test.
tests/data/Makefile.am	Registers test1676 in the test data makefile list.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[bagder]

Thanks!