Fix FillSigner to clear pubkeystored

[embhorn]

Description

Added cert->pubKeyStored = 0 and cert->subjectCNStored = 0 after the pointers are transferred to the signer, so subsequent calls to FillSigner on the same DecodedCert won't copy stale NULL pointers.

Fixes #10028

Testing

Added fill_signer_twice_test

Checklist

• added tests
• updated/added doxygen
• updated appropriate READMEs
• Updated manual and documentation

[Copilot]

Pull request overview

Fixes a FillSigner() ownership-transfer edge case by clearing DecodedCert “stored” flags after transferring pointers to a Signer, and adds a regression test to ensure repeated FillSigner() calls on the same DecodedCert don’t propagate stale NULL pointers.

Changes:

• Clear cert->pubKeyStored and cert->subjectCNStored after ownership transfer in FillSigner().
• Expose a small set of ASN/signer helpers with test visibility so they can be invoked from the test suite.
• Add fill_signer_twice_test regression test and wire it into the cert test flow.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
wolfssl/wolfcrypt/asn.h	Adjusts visibility/macros for FillSigner/signer helpers and DER alloc/free so tests can call them.
wolfcrypt/src/asn.c	Clears pubKeyStored and subjectCNStored when FillSigner() transfers ownership.
wolfcrypt/test/test.c	Adds and runs a regression test that calls FillSigner() twice on the same DecodedCert.

Comments suppressed due to low confidence (3)

wolfcrypt/test/test.c:1

• cert is a stack variable that is not initialized before potential ERROR_OUT(..., done) jumps (e.g., file open/read failures). Calling FreeDecodedCert(&cert) on an uninitialized DecodedCert can invoke frees on garbage pointers. Fix by zero-initializing cert at declaration (e.g., XMEMSET(&cert, 0, sizeof(cert));) or tracking whether InitDecodedCert() has been called and only calling FreeDecodedCert() when initialized.
  wolfcrypt/test/test.c:1
• The test silently truncates the cert if the file is larger than FOURK_BUF (e.g., bytes == FOURK_BUF), which makes the test brittle and can cause confusing parse failures when test certs change. Consider sizing the buffer to the file length (seek/tell + allocate), or at least detect truncation (bytes == FOURK_BUF and not EOF) and fail with a clear error.
  wolfcrypt/test/test.c:1
• The test silently truncates the cert if the file is larger than FOURK_BUF (e.g., bytes == FOURK_BUF), which makes the test brittle and can cause confusing parse failures when test certs change. Consider sizing the buffer to the file length (seek/tell + allocate), or at least detect truncation (bytes == FOURK_BUF and not EOF) and fail with a clear error.

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