HTTP Request Replay Script

run_http_capture.py

#!/usr/bin/env python3
# Author: Sean Pesce

"""
This script takes in a captured (well-formed) HTTP request dump and runs the request.

Example input:

GET /test HTTP/1.1
Accept:application/json
Accept-Charset:UTF-8
Host:test.com
"""

import requests
import sys

REQUEST_METHOD = {
    'GET': requests.get,
    'HEAD': requests.head,
    'POST': requests.post,
    'PUT': requests.put
}


def do_print(data, out_file=None, encoding='utf8'):
    if out_file is None:
        print(data)
    else:
        if type(data) == str:
            data = data.encode(encoding)
        out_file.write(data + b'\n')
    return


def parse_header_from_line(line, encoding='utf8'):
    if type(line) == bytes:
        line = line.decode(encoding)
    colon_idx = line.find(':')
    assert colon_idx >= 0, f'Invalid header line:\n{line}'
    key = line[:colon_idx].strip()
    val = line[colon_idx+1:].strip()
    return key, val


def do_http_request(http_req_data, use_ssl=True, out_file=None, encoding='utf8'):
    if b'\r\n' not in http_req_data:
        hdrs_end = http_req_data.find(b'\n\n')
        assert hdrs_end >= 0, 'Failed to find double line break'
        p1 = http_req_data[:hdrs_end]
        p2 = http_req_data[hdrs_end+2:]
        http_req_data = p1.replace(b'\n', b'\r\n') + b'\r\n\r\n' + p2

    lines = http_req_data.split(b'\r\n')

    method_line = lines[0].split(b' ')
    lines = lines[1:]
    method = method_line[0].decode('ascii')
    path = method_line[1].decode('ascii')
    protocol = method_line[2].decode('ascii')

    headers = {}
    i = 0
    for line in lines:
        try:
            key, val = parse_header_from_line(line, encoding)
            headers[key] = val
            i += 1
        except AssertionError:
            break

    while i < len(lines) and lines[i].strip() == b'':
        i += 1
        lines = lines[i:]

    body = b'\r\n'.join(lines).strip()
    url = 'https://'
    if not use_ssl:
        url = 'http://'
    url += headers['Host'] + path

    do_print(f'{method} {path} {protocol}\n\n', out_file)

    if method in ('GET', 'HEAD'):
        resp = REQUEST_METHOD[method](url=url, headers=headers)
    elif method in ('POST', 'PUT'):
        resp = REQUEST_METHOD[method](url=url, headers=headers, data=body)
    else:
        raise ValueError(f'Unsupported HTTP method: {method}')

    return resp


def print_http_response(resp, out_file=None):
    http_ver = 'HTTP/'
    if resp.raw.version == 9:
        http_ver += '0.9'  # Not actually in the documentation, but I assume this would be the case
    elif resp.raw.version == 10:
        http_ver += '1.0'
    elif resp.raw.version == 11:
        http_ver += '1.1'
    elif resp.raw.version == 20:
        http_ver += '2.0'  # Not actually in the documentation, but I assume this would be the case
    else:
        http_ver += '?'
    do_print(f'{http_ver} {resp.status_code} {resp.reason}', out_file)
    for hdr in resp.headers:
        do_print(f'{hdr}: {resp.headers[hdr]}', out_file)
    do_print('', out_file)
    if len(resp.content) > 0:
        # Attempt ASCII decode
        try:
            do_print(resp.text, out_file)
            return
        except UnicodeEncodeError:
            pass
        # Attempt unicode decode
        try:
            do_print(resp.content.decode('utf8'), out_file)
            return
        except UnicodeEncodeError:
            pass
        # Print raw Python byte string
        do_print(resp.content, out_file)
    return


if __name__ == '__main__':
    NO_SSL_FLAG = '--no-ssl'
    if len(sys.argv) < 2:
        print(f'Usage:\n  {sys.argv[0]} <HTTP request file> [{NO_SSL_FLAG}] [output file]')
        exit()

    USE_SSL = True
    if (len(sys.argv) > 2 and sys.argv[2] == NO_SSL_FLAG) or (len(sys.argv) > 3 and sys.argv[3] == NO_SSL_FLAG):
        USE_SSL = False

    OUT_FILE = None
    OUT_FPATH = None
    if len(sys.argv) > 2 and sys.argv[2] != NO_SSL_FLAG:
        OUT_FPATH = sys.argv[2]
    elif len(sys.argv) > 3 and sys.argv[3] != NO_SSL_FLAG:
        OUT_FPATH = sys.argv[3]

    if OUT_FPATH is not None:
        OUT_FILE = open(OUT_FPATH, 'wb')

    FPATH = sys.argv[1]
    HTTP_DATA = b''
    with open(FPATH, 'rb') as f:
        HTTP_DATA = f.read()

    RESPONSE = do_http_request(HTTP_DATA, USE_SSL, OUT_FILE)
    print_http_response(RESPONSE, OUT_FILE)

    if OUT_FILE is not None:
        OUT_FILE.close()