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package main
import (
"compress/gzip"
"flag"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"os"
"regexp"
"strings"
"time"
)
var (
input string
timeout int
headers headerFlags
userAgent string
depth int
delay int
httpClient = &http.Client{}
visited = make(map[string]bool)
)
type headerFlags []string
func (h *headerFlags) String() string {
return strings.Join(*h, ", ")
}
func (h *headerFlags) Set(value string) error {
*h = append(*h, value)
return nil
}
var defaultRegex = regexp.MustCompile(`(?:"|')((?:[a-zA-Z]{1,10}://|//)[^"'/]+\.[a-zA-Z]{2,}[^"']*|(?:/|\.\./|\./)[^"'><,;|()*\[\]\s][^"'><,;|()]{1,}|[a-zA-Z0-9_\-/]+/[a-zA-Z0-9_\-/.]+\.(?:php|asp|aspx|jsp|json|action|html|js|txt|xml)(?:[\?|#][^"']*)?)["']`)
func resolveInput(input string) (string, error) {
if strings.HasPrefix(input, "http://") || strings.HasPrefix(input, "https://") {
return "url", nil
}
if info, err := os.Stat(input); err == nil && !info.IsDir() {
return "file", nil
}
return "", fmt.Errorf("input must be a valid url or file path")
}
func fetchContent(sourceType, target string) (string, error) {
if sourceType == "url" {
if visited[target] {
return "", nil
}
visited[target] = true
req, err := http.NewRequest("GET", target, nil)
if err != nil {
return "", err
}
req.Header.Set("User-Agent", userAgent)
req.Header.Set("Accept-Encoding", "gzip")
for _, h := range headers {
parts := strings.SplitN(h, ":", 2)
if len(parts) == 2 {
req.Header.Add(strings.TrimSpace(parts[0]), strings.TrimSpace(parts[1]))
}
}
resp, err := httpClient.Do(req)
if err != nil {
return "", err
}
defer resp.Body.Close()
var reader io.ReadCloser
switch resp.Header.Get("Content-Encoding") {
case "gzip":
reader, err = gzip.NewReader(resp.Body)
if err != nil {
return "", err
}
defer reader.Close()
default:
reader = resp.Body
}
body, err := io.ReadAll(reader)
if err != nil {
return "", err
}
return string(body), nil
}
f, err := os.Open(target)
if err != nil {
return "", err
}
defer f.Close()
content, err := ioutil.ReadAll(f)
return string(content), err
}
func parseContent(content string, re *regexp.Regexp) []string {
seen := make(map[string]bool)
results := []string{}
for _, match := range re.FindAllStringSubmatch(content, -1) {
link := match[1]
if !seen[link] {
seen[link] = true
results = append(results, link)
}
}
return results
}
func printMatches(source string, matches []string) {
fmt.Printf("[inf] %s\n", strings.ToLower(source))
for _, match := range matches {
fmt.Println(strings.ToLower(match))
}
fmt.Println()
}
func crawl(target string, base *url.URL, maxDepth int) {
if maxDepth < 0 {
return
}
content, err := fetchContent("url", target)
if err != nil || content == "" {
fmt.Printf("[err] failed to fetch %s: %v\n", target, err)
return
}
matches := parseContent(content, defaultRegex)
printMatches(target, matches)
for _, match := range matches {
u := resolveURL(base, match)
if u == "" {
continue
}
parsed, err := url.Parse(u)
if err != nil || parsed.Host != base.Host {
continue
}
if maxDepth > 0 && delay > 0 {
time.Sleep(time.Duration(delay) * time.Second)
}
crawl(u, base, maxDepth-1)
}
}
func resolveURL(base *url.URL, href string) string {
href = strings.TrimSpace(href)
if strings.HasPrefix(href, "//") {
return base.Scheme + ":" + href
}
if strings.HasPrefix(href, "http://") || strings.HasPrefix(href, "https://") {
return href
}
ref, err := url.Parse(href)
if err != nil {
return ""
}
return base.ResolveReference(ref).String()
}
func init() {
const usageHeader = `
web crawling and link extraction tool written in Go, inspired by https://github.com/GerbenJavado/LinkFinder
author: heqnx - https://heqnx.com
`
flag.Usage = func() {
fmt.Fprint(os.Stderr, usageHeader)
fmt.Fprintf(os.Stderr, "usage of %s:\n", os.Args[0])
flag.PrintDefaults()
}
flag.CommandLine.SetOutput(os.Stderr)
}
func main() {
flag.StringVar(&input, "input", "", "url or file path")
flag.IntVar(&timeout, "timeout", 10, "timeout for http requests in seconds")
flag.StringVar(&userAgent, "user-agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.10 Safari/605.1.1", "set user-agent")
flag.Var(&headers, "header", "add http header to request (e.g. -header \"Authorization: Bearer val1\")")
flag.IntVar(&depth, "depth", 0, "recursion depth for same-domain links (0 disables crawling)")
flag.IntVar(&delay, "delay", 4, "delay between requests in seconds when crawling (only applies if depth > 0)")
flag.Parse()
if flag.NFlag() == 0 && flag.NArg() == 0 {
flag.Usage()
os.Exit(1)
}
if input == "" {
fmt.Printf("[err] input is required. use -input <url|file>\n")
os.Exit(1)
}
httpClient.Timeout = time.Duration(timeout) * time.Second
sourceType, err := resolveInput(input)
if err != nil {
fmt.Printf("[err] %v\n", err)
os.Exit(1)
}
if sourceType == "url" {
baseURL, _ := url.Parse(input)
crawl(input, baseURL, depth)
} else {
content, err := fetchContent("file", input)
if err != nil {
fmt.Printf("[err] failed to fetch %s: %v\n", input, err)
os.Exit(1)
}
matches := parseContent(content, defaultRegex)
printMatches(input, matches)
}
}
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