Nmap error handling

[TerminalFi]

Added a NmapErrors Struct for holding errors encountered during the Nmap Scan. Since these errors are specific to nmap, we shouldn't cancel an entire multi target scan just because one host is unresolvable or causing issues.

Additionally, added a utils file that holds a RemoveDuplicates to remove Duplicate nmap errors. Nmap can under certain circumstances return duplicate errors.

This could potentially be further improved to remove duplicates of specific errors.

Example Usage:

package main

import (
	"context"
	"fmt"
	"log"
	"time"

	"github.com/theseceng/nmap"
)

func main() {
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
	defer cancel()

	// Equivalent to `/usr/local/bin/nmap -p 80,443,843 google.com facebook.com youtube.com`,
	// with a 5 minute timeout.
	scanner, err := nmap.NewScanner(
		nmap.WithTargets("facebook.com", "Bad.Domain.Com.Dsads"),
		nmap.WithPorts("80"),
		nmap.WithContext(ctx),
	)
	if err != nil {
		log.Fatalf("unable to create nmap scanner: %v", err)
	}

	result, err := scanner.Run()
	if err != nil {
		fmt.Println("Errors encountered")
	}

	for _, e := range result.NmapErrors {
		fmt.Printf("[ ERROR ] - %v\n", e.Error)
	}

	// Use the results to print an example output
	for _, host := range result.Hosts {
		if len(host.Ports) == 0 || len(host.Addresses) == 0 {
			continue
		}

		fmt.Printf("[ SUCCESS ] - Host %q:\n", host.Addresses[0])

		for _, port := range host.Ports {
			fmt.Printf("\t\tPort %d/%s %s %s\n", port.ID, port.Protocol, port.State, port.Service.Name)
		}
	}

	fmt.Printf("Nmap done: %d hosts up scanned in %.2f seconds\n", len(result.Hosts), result.Stats.Finished.Elapsed)
}

[Ullaakut]

Hi @TheSecEng!

Congratulations on your PR, I'm very excited about your contribution :) I have a few suggestions, mostly related to style, but that should be addressed before the PR can be merged 👍

Thanks a lot and let me know if you have any questions!

[TerminalFi]

Hi @TheSecEng!

Congratulations on your PR, I'm very excited about your contribution :) I have a few suggestions, mostly related to style, but that should be addressed before the PR can be merged 👍

Thanks a lot and let me know if you have any questions!

All changes have been made...This is my first PR on a project ! What a learning experience.

[Ullaakut]

Hey @TheSecEng !

Well you did a great job for a first PR! 👏 I'll just checkout the branch and test it out on my machine for a few minutes, and then it will be merged :) Thanks again for your contribution friend!

[Ullaakut]

Ah, the unit tests need an update it seems!

# github.com/Ullaakut/nmap [github.com/Ullaakut/nmap.test]
./xml_test.go:1069:24: not enough arguments in call to Parse
	have ([]byte)
	want ([]byte, []NmapError)

If you are not familiar with Go unit tests, let me know and I'll handle it :)

[TerminalFi]

Ah, the unit tests need an update it seems!

# github.com/Ullaakut/nmap [github.com/Ullaakut/nmap.test]
./xml_test.go:1069:24: not enough arguments in call to Parse
	have ([]byte)
	want ([]byte, []NmapError)

If you are not familiar with Go unit tests, let me know and I'll handle it :)

I am unfamiliar with those. I'd love to see what you have to change to make this work. As a learning experience.

[Ullaakut]

Okay so after looking into it, I think it's better for Parse not to take an extra nmapErrors arguments, since it isn't really used for parsing at all, it's simply put into the Run structure, so instead let's delegate this responsibility to the Scanner.Run method by simply setting result.NmapErrors = nmapErrors after the parsing :) This means we don't even need to update the tests 🎉

If we kept it, the way the tests would have been changed in this case would have simply been to pass a nil value for the nmapResults, since they are not used. If there was some logic to test with the nmapResults however, we'd have needed a brand new test to ensure that it behaves as expected :)

EDIT: I'll push a commit that makes those changes in a few minutes and we'll merge the PR :)

[TerminalFi]

e it isn't really used for parsing

Ahh you know, originally when I had this written out I had additional logic in the Parse() function. Since I removed that, you are right, its not needed.

Commited.