fix: initialize s2n_cert fields in s2n_connection_get_peer_cert_chain

[jouho]

Goal

Ensure s2n_connection_get_peer_cert_chain() returns fully-initialized s2n_cert nodes.

Why

The function allocated each s2n_cert node with s2n_alloc (which does not zero memory) and only set the raw and next fields. The pkey_type, public_key, and info fields were left as uninitialized heap bytes. Callers reading those fields (e.g. via s2n_cert_chain_and_key_get_pkey_type()) could leak heap residue or act on a garbage key type. The correct pattern was already used in s2n_create_cert_chain_from_stuffer().

How

• Zero each node after allocation with s2n_blob_zero(), so all fields have a defined value.
• Populate info for every cert, and pkey_type/public_key for the leaf cert, from the parsed X509, mirroring s2n_cert_chain_and_key_load().

Callouts

An unknown leaf key type now fails with S2N_ERR_CERT_TYPE_UNSUPPORTED, matching s2n_cert_chain_and_key_load().

Testing

Existing s2n_certificate_test (covers s2n_connection_get_peer_cert_chain success/failure paths) and s2n_cert_validation_callback_test pass.

Related

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