Create subdomain_finder_in_python.md

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# How to Create a Sub-Domain Finder in Python
The following is a sample Python script to find subdomains using DNS. This script is using the `dns.resolver` module from the `dnspython` library. If you don't have the library installed, you can install it using pip:
```
pip install dnspython
```
The following is the Python script that can be used to find subdomains for a given domain using a provided wordlist file:
```
import dns.resolver
import argparse
def load_subdomains(file_path):
with open(file_path, 'r') as file:
subdomains = file.read().splitlines()
return subdomains
def find_subdomains(domain, subdomains):
found_subdomains = []
resolver = dns.resolver.Resolver()
for subdomain in subdomains:
target = f'{subdomain}.{domain}'
try:
answers = resolver.resolve(target, 'A')
found_subdomains.append((target, [str(answer) for answer in answers]))
except dns.resolver.NXDOMAIN:
pass
except Exception as e:
print(f'Error resolving {target}: {e}')
return found_subdomains
def main():
parser = argparse.ArgumentParser(description='Find subdomains using DNS')
parser.add_argument('domain', type=str, help='Domain to search for subdomains')
parser.add_argument('wordlist', type=str, help='Path to subdomain wordlist file')
args = parser.parse_args()
subdomains = load_subdomains(args.wordlist)
found_subdomains = find_subdomains(args.domain,
```
- Import necessary libraries: The script imports the dns.resolver module from the dnspython library, as well as the argparse module to handle command-line arguments.
- `load_subdomains(file_path)`: This function takes a file path as input and reads the file, splitting the content by lines to get a list of subdomains. It returns the list of subdomains.
- `find_subdomains(domain, subdomains)`: This function takes a domain and a list of subdomains as input. It initializes a DNS resolver object and iterates through the subdomains list, attempting to resolve each subdomain by appending it to the domain and performing a DNS lookup for the 'A' record (IPv4 address). If the lookup is successful, the subdomain and its corresponding IP addresses are added to the found_subdomains list. If the lookup fails with a `dns.resolver.NXDOMAIN` exception, the subdomain does not exist, and the script continues to the next subdomain. For other exceptions, an error message is printed. The function returns the `found_subdomains` list containing the successfully resolved subdomains and their IP addresses.
- `main()`: This function sets up the command-line argument parser, which expects two arguments: the target domain and the path to the subdomain wordlist file. It then calls `load_subdomains()` to load the subdomains from the wordlist file, and `find_subdomains()` to perform the DNS lookups.