#!/usr/bin/env python3

import argparse

import sys

import urllib.request

import urllib.parse

import urllib.error

from http.client import HTTPMessage # For type hinting response.info()

# --- Configuration ---

USER_AGENT = "Python-StdLib-HeaderCheck/1.1" # Version bump

def check_url_features(url: str):

"""

Performs checks on a given URL for Gzip, ETag, and Last-Modified support.

Args:

url: The URL string to test.

Returns:

None. Prints results to stdout. Exits with code 1 on critical errors.

"""

print(f"[*] Testing URL: {url}")

# --- State Variables ---

supports_gzip = False

etag = None

last_modified = None

etag_conditional_worked = None # None = N/A, False = Failed, True = Worked (304)

last_modified_conditional_worked = (

None # None = N/A, False = Failed, True = Worked (304)

)

# --- Initial Request (Check for Gzip, ETag, Last-Modified) ---

print("[*] Performing initial GET request...")

initial_headers = {

"Accept-Encoding": "gzip",

"User-Agent": USER_AGENT,

}

req_initial = urllib.request.Request(url, headers=initial_headers, method="GET")

try:

with urllib.request.urlopen(

req_initial, timeout=15

) as response: # Increased timeout slightly

initial_info = response.info() # Headers object

status_code = response.getcode()

print(f"[+] Initial request successful (Status: {status_code})")

# Check for Gzip support in response

content_encoding = initial_info.get("Content-Encoding", "").lower()

if "gzip" in content_encoding:

supports_gzip = True

print("[+] Gzip: Supported (Server sent 'Content-Encoding: gzip')")

else:

print("[-] Gzip: Not detected in response headers.")

# Extract ETag and Last-Modified for conditional requests

etag = initial_info.get("ETag")

last_modified = initial_info.get("Last-Modified")

if etag:

print(f"[+] ETag: Found ('{etag}')")

else:

print("[-] ETag: Header not found.")

if last_modified:

print(f"[+] Last-Modified: Found ('{last_modified}')")

else:

print("[-] Last-Modified: Header not found.")

# Ensure response body is read and connection potentially closed/reused

response.read()

except urllib.error.HTTPError as e:

print(

f"[!] Initial Request Failed: HTTP Error {e.code} - {e.reason}",

file=sys.stderr,

)

if e.headers:

print("[!] Server response headers (on error):")

print(e.headers)

sys.exit(1)

except urllib.error.URLError as e:

print(f"[!] Initial Request Failed: URL Error - {e.reason}", file=sys.stderr)

sys.exit(1)

except Exception as e:

print(

f"[!] Initial Request Failed: An unexpected error occurred - {e}",

file=sys.stderr,

)

sys.exit(1)

# --- Conditional GET Request (ETag) ---

if etag:

print("\n[*] Performing conditional GET request using ETag...")

etag_conditional_worked = False # Assume failure unless we get 304

conditional_headers_etag = {

"User-Agent": USER_AGENT,

"If-None-Match": etag,

"Accept-Encoding": "gzip",

}

req_conditional_etag = urllib.request.Request(

url, headers=conditional_headers_etag, method="GET"

)

try:

with urllib.request.urlopen(req_conditional_etag, timeout=10) as response:

status_code = response.getcode()

# If we get here without a 304, the conditional GET didn't work as expected

print(

f"[-] ETag Conditional GET: Did not work as expected. Received Status {status_code} (expected 304). Server sent full response."

)

response.read() # Consume body

except urllib.error.HTTPError as e:

if e.code == 304:

print(

"[+] ETag Conditional GET: Worked! Received Status 304 (Not Modified)."

)

etag_conditional_worked = True

else:

print(

f"[!] ETag Conditional GET: Failed. Server responded with HTTP Error {e.code} - {e.reason}",

file=sys.stderr,

)

except urllib.error.URLError as e:

print(

f"[!] ETag Conditional GET: Request failed. URL Error - {e.reason}",

file=sys.stderr,

)

except Exception as e:

print(

f"[!] ETag Conditional GET: Request failed. An unexpected error occurred - {e}",

file=sys.stderr,

)

else:

print(

"\n[*] Skipping ETag conditional GET (No ETag found in initial response)."

)

# etag_conditional_worked remains None

# --- Conditional GET Request (Last-Modified) ---

if last_modified:

print("\n[*] Performing conditional GET request using Last-Modified...")

last_modified_conditional_worked = False # Assume failure unless we get 304

conditional_headers_lm = {

"User-Agent": USER_AGENT,

"If-Modified-Since": last_modified,

"Accept-Encoding": "gzip",

}

req_conditional_lm = urllib.request.Request(

url, headers=conditional_headers_lm, method="GET"

)

try:

with urllib.request.urlopen(req_conditional_lm, timeout=10) as response:

status_code = response.getcode()

# If we get here without a 304, the conditional GET didn't work as expected

print(

f"[-] Last-Modified Conditional GET: Did not work as expected. Received Status {status_code} (expected 304). Server sent full response."

)

response.read() # Consume body

except urllib.error.HTTPError as e:

if e.code == 304:

print(

"[+] Last-Modified Conditional GET: Worked! Received Status 304 (Not Modified)."

)

last_modified_conditional_worked = True

else:

print(

f"[!] Last-Modified Conditional GET: Failed. Server responded with HTTP Error {e.code} - {e.reason}",

file=sys.stderr,

)

except urllib.error.URLError as e:

print(

f"[!] Last-Modified Conditional GET: Request failed. URL Error - {e.reason}",

file=sys.stderr,

)

except Exception as e:

print(

f"[!] Last-Modified Conditional GET: Request failed. An unexpected error occurred - {e}",

file=sys.stderr,

)

else:

print(

"\n[*] Skipping Last-Modified conditional GET (No Last-Modified header found)."

)

# last_modified_conditional_worked remains None

# --- Final Summary ---

print("\n--- Summary ---")

print(f"URL: {url}")

print(f"Gzip Supported by Server: {'Yes' if supports_gzip else 'No'}")

print(f"ETag Header Present: {'Yes' if etag else 'No'}")

if etag:

print(

f"ETag Conditional GET Works (Returns 304): {'Yes' if etag_conditional_worked else 'No'}"

)

else:

print(f"ETag Conditional GET Works (Returns 304): N/A")

print(f"Last-Modified Header Present: {'Yes' if last_modified else 'No'}")

if last_modified:

print(

f"Last-Modified Conditional GET Works (Returns 304): {'Yes' if last_modified_conditional_worked else 'No'}"

)

else:

print(f"Last-Modified Conditional GET Works (Returns 304): N/A")

print("-------------\n")

def main():

"""Parses arguments and runs the check."""

parser = argparse.ArgumentParser(

description="Check a URL for Gzip, ETag, and Last-Modified support using only Python's standard library.",

formatter_class=argparse.ArgumentDefaultsHelpFormatter,

)

parser.add_argument("url", help="The URL to test (e.g., https://www.example.com)")

args = parser.parse_args()

# Basic URL validation and scheme addition

parsed_url = urllib.parse.urlparse(args.url)

if not parsed_url.scheme:

# Try https first if no scheme provided, fall back to http if needed?

# For simplicity now, just default to http and warn.

print(

f"[!] URL '{args.url}' is missing a scheme (e.g., http:// or https://). Assuming 'http://'.",

file=sys.stderr,

)

url_to_test = f"http://{args.url}"

parsed_url = urllib.parse.urlparse(url_to_test) # Re-parse

if not parsed_url.netloc:

print(

f"[!] Invalid URL structure even after adding http://: '{url_to_test}'",

file=sys.stderr,

)

sys.exit(1)

else:

url_to_test = args.url

if not parsed_url.netloc:

print(f"[!] Invalid URL structure: '{url_to_test}'", file=sys.stderr)

sys.exit(1)

check_url_features(url_to_test)

if __name__ == "__main__":

main()