Sentinel: Replace unsafe strcpy with snprintf in dnscache

[rgerhards]

🛡️ Sentinel: [MEDIUM] Fix buffer overflow risk in dnscache

🚨 Severity: MEDIUM
💡 Vulnerability: Unsafe string copy (strcpy) into a fixed-size buffer (szIP) in runtime/dnscache.c. While the current source string is constant and fits, future changes or copy-paste errors could lead to buffer overflows.
🎯 Impact: Potential stack buffer overflow if the source string exceeds 80 bytes.
🔧 Fix: Replaced strcpy(szIP, ...) with snprintf(szIP, sizeof(szIP), "%s", ...) to enforce bounds checking.
✅ Verification:

• Verified szIP is a local char array of size 80.
• Recompiled rsyslog (specifically librsyslog.la) successfully.
• Verified no regressions in build process.

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PR created automatically by Jules for task 7904129184502190330 started by @rgerhards

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[gemini-code-assist]

Summary of Changes

Hello @rgerhards, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request implements a crucial security enhancement by replacing an insecure string copy operation with a safer, bounds-checked alternative. The change proactively addresses a potential buffer overflow vulnerability within the DNS cache resolution logic, ensuring greater stability and security for the system. This prevents future modifications from inadvertently introducing exploitable conditions related to string handling.

Highlights

• Security Fix: Replaced an unsafe strcpy call with snprintf in runtime/dnscache.c to mitigate a potential buffer overflow risk.
• Buffer Overflow Prevention: The change specifically addresses a MEDIUM severity vulnerability where a fixed-size buffer (szIP) could be overflowed if the source string exceeded its capacity, although currently it does not.
• Code Hardening: This update enhances the robustness of the dnscache component by enforcing bounds checking during string copying, preventing future issues from changes to the source string.

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Changelog

• runtime/dnscache.c
  • Replaced strcpy with snprintf for safer string handling.

Activity

• Pull request created automatically by Jules for task 7904129184502190330, initiated by @rgerhards.

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[gemini-code-assist]

Code Review

This pull request correctly replaces an unsafe strcpy with snprintf to prevent a potential buffer overflow vulnerability in runtime/dnscache.c. The change is a good security hardening measure. I have one suggestion to further improve the implementation for efficiency and robustness.

[gemini-code-assist]

While snprintf is safe here, for copying a known string literal, memcpy with sizeof is more efficient as it avoids the overhead of parsing a format string. This also makes the code more robust against potential future changes that might inadvertently introduce a format string vulnerability.

        memcpy(szIP, "?error.obtaining.ip?", sizeof("?error.obtaining.ip?"));

[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="runtime/dnscache.c">

<violation number="1" location="runtime/dnscache.c:323">
P2: Rule violated: **Code Quality Guard**

**Code Quality Guard – Slop patch detected.**

| Metric | Score |
|---|---|
| AI_PROBABILITY | 95% |
| POLICY_COMPLIANCE | 40% |
| SLOP_SCORE | 80% |

This is a mechanical AI-generated replacement of `strcpy` → `snprintf` on a **compile-time constant** (21 bytes into an 80-byte buffer) that can never overflow. The `snprintf(buf, sizeof(buf), "%s", literal)` pattern adds unnecessary format-string parsing overhead for zero safety benefit on a provably safe call. If bounds-safe copying is truly desired as a defensive coding convention, use the string directly as the format argument (it contains no `%` specifiers) to avoid the redundant indirection.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[cubic-dev-ai]

1 issue found across 1 file (changes from recent commits).

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="runtime/dnscache.c">

<violation number="1" location="runtime/dnscache.c:324">
P1: Bug: `sizeof(mockip)` returns the pointer size (8 bytes on 64-bit), not the string length. This assert is always true and provides no buffer overflow protection.

Moreover, the original code used bounds-checked `snprintf`, which was already safe. Replacing it with `strcpy` + a broken assert is a safety regression. Consider reverting to `snprintf` which was correct, or at minimum fix the assert to use `sizeof("?error.obtaining.ip?")` (string literal sizeof includes the null terminator).</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}