Fix Incorrect conversion between integer types

[opsysdebug]

To address the incorrect conversion, we should ensure that only valid, positive, in-range user and group IDs are allowed to flow to the place they are cast to uint32. The best fix is to add explicit range checks where the conversion from int (parsed from string) to the UID/GID storage location happens—specifically in the return statements of getentGetID, FindUID, and FindGID in internal/pkg/agent/install/user_linux.go. These must only return an id if it is within [0, math.MaxUint32], otherwise return an error. This prevents any "out of range" id from ever being used to populate the ownership struct or to reach the cast in the credential setup.

To implement this:

• In internal/pkg/agent/install/user_linux.go:
  • At the end of getentGetID, after parsing the id, check that 0 <= val <= math.MaxUint32. If not, return error.
  • Update imports to include "math" for math.MaxUint32.

This patch does not change the user-facing functionality; it only ensures that the code safely handles ids from the OS and will fail fast if there are anomalies.

References

Integer overflow
Go language specification Integer overflow
strconv.Atoi
strconv.ParseInt
strconv.ParseUint

Checklist

• I have read and understood the pull request guidelines of this project.
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

[mergify]

This pull request does not have a backport label. Could you fix it @opsysdebug? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-./d./d is the label that automatically backports to the 8./d branch. /d is the digit
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)