Resolve "[sync] Backport login_enabled Raw Data Collection to v1.3.1"

[geunwoonoh]

Summary

Backport the login_enabled raw data collection feature from main branch to release/v1.3.1.

This change enables alpamon to collect raw login-related data from /etc/shadow and /etc/shells, allowing the server to make more accurate login_enabled determinations.

Changes

• Add ShadowExpireDate (*int64) and ValidShells ([]string) fields to UserData struct
• Add shadowEntry struct for internal shadow file parsing
• Add loadValidShells() helper function to read /etc/shells
• Add loadShadowData() helper function to read /etc/shadow
• Update getUserData() to collect raw data for server-side login_enabled calculation
• Add unit tests for new functionality

Why Backport?

• This feature needs to be included in the v1.3.1 release
• Maintains backward compatibility with existing servers (server ignores extra fields)
• Security-related improvement requiring deployment

Files Changed

File	Changes
pkg/runner/commit_types.go	Add raw data fields to UserData, add shadowEntry struct, update GetData()
pkg/runner/commit.go	Add constants, loadValidShells(), loadShadowData(), update getUserData()
pkg/runner/commit_test.go	Add TestLoadValidShells, TestLoadShadowData, TestGetUserDataWithRawFields

Raw Data Fields

Field	Type	Source	Description
shadow_expire_date	*int64	/etc/shadow	Raw expiration date (days since epoch)
valid_shells	[]string	/etc/shells	Full list of valid login shells

Note: password_locked field is excluded - alpamon runs as root, so websh/webftp can access password-locked accounts regardless.

Example JSON Output

{
  "uid": 1000,
  "gid": 1000,
  "username": "user",
  "description": "User",
  "directory": "/home/user",
  "shell": "/bin/bash",
  "shadow_expire_date": null,
  "valid_shells": ["/bin/sh", "/bin/bash", "/bin/zsh", "/usr/bin/zsh"]
}

Testing

• go build ./... passes
• go test -v ./pkg/runner/... -p 1 passes
• go vet ./pkg/runner/... passes
• gofmt - no formatting issues

Backward Compatibility

alpamon	alpacon-server	Behavior
Old (no raw data)	Old	Server calculates based on shell only
Old (no raw data)	New	Server calculates based on shell only (fallback)
New (raw data)	Old	Server ignores extra fields
New (raw data)	New	Server uses raw data for accurate determination

Related

• Original Issue: [sync] Improve login_enabled field accuracy with native Linux checks #169
• Backport Issue: [sync] Backport login_enabled Raw Data Collection to v1.3.1 #171
• Target Branch: release/v1.3.1