Add a global flag to customize the User-Agent

[onSec-fr]

Motivation

Previously, the User-Agent used by AzureHound was hardcoded and could only be changed by recompiling the binary.
This PR introduces a simple way to set a custom User-Agent at runtime using the --user-agent (-U) flag, making it easier for evasion or for debugging/identification purposes.

Main changes

• Added a global --user-agent (-U) flag in the CLI configuration (config.go).
• All HTTP requests now use the custom User-Agent if the flag is set; otherwise, they fall back to the default (constants-based) value.

Results

Summary by CodeRabbit

• New Features
  • Added support for a custom User-Agent header applied to all HTTP requests.
  • Configure via the new "user-agent" setting or the -U command-line flag; the value is persisted across runs.
  • If not specified, the existing default User-Agent remains in effect.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

Adds a global user-agent config option and updates HTTP request creation to use config.UserAgent.Value() when non-empty, otherwise falling back to the existing constants.UserAgent(). No other request construction behavior changed.

Changes

Cohort / File(s)	Summary
Config: Add UserAgent option config/config.go	Adds exported UserAgent config entry (name "user-agent", shorthand "U", usage "Custom User-Agent header", persistent true, default ""). Appends UserAgent to GlobalConfig.
HTTP client: Respect configurable User-Agent client/rest/http.go	NewRequest now sets User-Agent header from config.UserAgent.Value() if non-empty; otherwise uses constants.UserAgent(). Other query/body/Content-Type/Accept logic unchanged.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  actor Caller
  participant REST as REST Client
  participant Cfg as Config
  participant HTTP as http.Request

  Caller->>REST: NewRequest(method, url, body)
  REST->>Cfg: UserAgent.Value()
  alt Non-empty UserAgent
    REST->>HTTP: Set header "User-Agent" = Cfg value
  else Empty UserAgent
    REST->>HTTP: Set header "User-Agent" = constants.UserAgent()
  end
  REST->>HTTP: Set query/body/Content-Type/Accept (unchanged)
  REST-->>Caller: *http.Request

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Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

I twitch my whiskers at headers that glide,
A custom name now hops in stride.
If fields are empty, worry not—
The fallback keeps our headers hot.
Thump-thump, the request takes flight. 🐇✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: adding a global flag to customize the User-Agent header, which is exactly what the PR implements across config.go and http.go.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

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[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[onSec-fr]

I have read the CLA Document and I hereby sign the CLA

[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (2)

client/rest/http.go (1)

131-137: LGTM! Consider adding input validation for User-Agent strings.

The type assertion and fallback logic are implemented correctly. The code safely checks if the config value is a non-empty string before using it, falling back to the default User-Agent otherwise.

However, consider adding basic validation to ensure the User-Agent string doesn't contain characters that could cause issues with HTTP headers (e.g., newlines, control characters). While http.Header.Set doesn't return errors, malformed headers could potentially cause unexpected behavior with certain servers or proxies.

Example validation:

// set azurehound as user-agent, use custom if set in config
ua := config.UserAgent.Value()
if s, ok := ua.(string); ok && s != "" {
	// Basic validation: reject if contains control characters
	if strings.ContainsAny(s, "\r\n\x00") {
		return nil, fmt.Errorf("invalid User-Agent: contains control characters")
	}
	req.Header.Set("User-Agent", s)
} else {
	req.Header.Set("User-Agent", constants.UserAgent())
}

config/config.go (1)

358-364: LGTM! Consider enhancing the usage documentation.

The config definition follows the established pattern and correctly sets all required fields. The empty default ensures the fallback behavior works as intended.

The usage text could be more descriptive to help users understand when and why they might want to customize the User-Agent (e.g., for evasion, debugging, or organizational identification purposes).

Example enhanced usage:

 UserAgent = Config{
 	Name:       "user-agent",
 	Shorthand:  "U",
-	Usage:      "Custom User-Agent header",
+	Usage:      "Custom User-Agent header for HTTP requests (useful for evasion, debugging, or identification)",
 	Persistent: true,
 	Default:    "",
 }

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 6745e7b and f7bf368.

📒 Files selected for processing (2)

• client/rest/http.go (1 hunks)
• config/config.go (2 hunks)

🧰 Additional context used

🧬 Code graph analysis (2)

client/rest/http.go (1)

config/config.go (1)

• UserAgent (358-364)

config/config.go (1)

config/internal/config.go (1)

• Config (32-41)

🔇 Additional comments (2)

config/config.go (2)

375-375: LGTM!

The UserAgent config is correctly added to the GlobalConfig slice, making it available as a persistent global flag across all commands.

---

358-364: Shorthand “U” is unique – no other occurrences found in config definitions or command flags.

[onSec-fr]

I had the same need as #135