Fix error handling in wolfTPM examples

[aidangarske]

F-11902, F-11904, F-11905, F-11906, F-11907, F-13455, F-13458, F-13528

[Copilot]

🟡 Changes recommended

There are a few correctness/debuggability gaps in the updated error handling (including a potential UINT64 wrap in clock_set.c) that should be addressed before merge.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR tightens error handling and correctness in several wolfTPM example programs, reducing “silent success/failure” cases and avoiding insecure example behavior (notably certificate verification override).

Changes:

• TLS verify callback now honors preverify instead of always overriding certificate failures.
• Example utilities improve file I/O error handling (open/write/read) and propagate failures via rc/goto exit.
• Timestamp and PCR examples adjust time/digest handling for more correct behavior across build configurations.

File summaries

File	Description
examples/tls/tls_common.h	Stop overriding certificate verification failures; return preverify.
examples/timestamp/clock_set.c	Treat CLI argument as a forward increment (adds to current clock).
examples/pkcs7/pkcs7.c	Fail fast on output file open failure in two code paths.
examples/pcr/quote.c	Add explicit open/write failure handling when saving quote output.
examples/pcr/extend.c	Improve file read loop error handling; add “digest-from-file” path when wolfCrypt is disabled.
examples/attestation/make_credential.c	Check wolfTPM2_GetRandom result; harden file write handling for output blob/secret.

Review details

Suppressed comments (1)

examples/pkcs7/pkcs7.c:314

• On file open failure, this now returns -1 but doesn't print any error, which makes it hard to diagnose why the example failed. Emit a message that includes the output path before exiting.

    else {
        rc = -1; goto exit;
    }

• Files reviewed: 6/6 changed files
• Comments generated: 3
• Review effort level: Lite

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.