oauth-backend/addon/redirect_uri_check.py

from mitmproxy import http
import aiohttp
from urllib.parse import urlparse, parse_qs, urlencode, urlunparse  
import lib.target as target  
from lib.report import save_report 

class BypassPayload:
    """ 우회 패턴 정의 """
    def __init__(self, name: str, mutate_func, description: str):
        self.name = name
        self.mutate = mutate_func #우회 url 만드는 함수
        self.description = description


class RedirectBypassChecker:
    def __init__(self):
        """ 우회 페이로드 목록 """
        self.bypass_payloads = [
            BypassPayload(
                name=r"@",
                mutate_func=self._mutate_pattern1,
                description=r"@ 기호를 이용한 호스트 우회 공격: evil.com@target.com"
            ),
            
        ]
        self.session = None

    """ 우회 URL 생성 목록 """
    # 1. @
    def _mutate_pattern1(self, original: str) -> str:
        parsed = urlparse(original)
        mutated = f"https://evil.com@{parsed.netloc}{parsed.path}"
        print(f"[redirect_uri_check] original: {original} → mutated: {mutated}")
        return mutated

    '''aiohttp 세션 생성 (재사용)'''
    async def _get_session(self):
        if self.session is None:
            timeout = aiohttp.ClientTimeout(total=10)
            self.session = aiohttp.ClientSession(timeout=timeout)
        return self.session

    '''세션 정리'''
    async def close_session(self):
        if self.session:
            await self.session.close()
            self.session = None

    """ 우회된 URL에 GET 요청을 보내고, 서버 응답 정보 반환 """
    async def _send_request(self, url, headers=None):
        try:
            session = await self._get_session() # 세션 준비
            request_headers = headers or {} # 요청 헤더 설정 - headers가 주어지지 않았다면 빈 딕셔너리 사용
            
            # 서버에 GET 요청 전송 
            async with session.get(url, allow_redirects=False, headers=request_headers) as response:
                return {
                    'status': response.status,
                    'location': response.headers.get("Location", ""),
                    'headers': dict(response.headers)
                }
        except Exception as e:
            print(f"[ERROR] 요청 실패 ({url}): {e}")
            return {'status': 500, 'location': '', 'headers': {}}

    """ redirect_uri가 기준 도메인(baseUrl)에 속하는지 판단 """
    def _is_baseline_valid(self, redirect_uri: str, base_url: str) -> bool:
        try:
            redirect_parsed = urlparse(redirect_uri)
            base_parsed = urlparse(base_url)
            
            redirect_host = redirect_parsed.hostname
            base_host = base_parsed.hostname
            
            if not redirect_host or not base_host:
                return False
            
            if "@" in redirect_uri:
                if redirect_host != base_host:
                    print(f"[ALERT] 우회 공격 탐지: {redirect_host} != {base_host}")
                    return False
                
                at_parts = redirect_uri.split('@')
                if len(at_parts) > 1:
                    before_at = at_parts[0]
                    if '//' in before_at:
                        potential_domain = before_at.split('//')[-1]
                        if '.' in potential_domain and potential_domain != base_host:
                            print(f"[CRITICAL] @ 우회 공격: {potential_domain}@{base_host}")
                            return False
            
            is_valid = (redirect_host == base_host or redirect_host.endswith(f".{base_host}"))
            return is_valid
            
        except Exception as e:
            print(f"[ERROR] 도메인 검증 실패: {e}")
            return False
        
    """ Location 헤더에서 authorization code 추출 """    
    def _extract_code_from_location(self, location: str) -> str:
        if not location:
            return ""
        
        try:
            parsed = urlparse(location)
            query = parse_qs(parsed.query)
            return query.get('code', [''])[0]
        except:
            return ""

    """ 메인 테스트 함수 - mitmproxy flow 처리 """
    async def test(self, flow: http.HTTPFlow):
        url = flow.request.pretty_url
        parsed = urlparse(url)
        query = parse_qs(parsed.query)

        if "redirect_uri" not in query:
            return

        original_redirect_uri = query["redirect_uri"][0]
        print(f"[DEBUG] 원본 redirect_uri: {original_redirect_uri}")

        for payload in self.bypass_payloads:
            try:
                await self._test_bypass_pattern(
                    url, query, parsed, original_redirect_uri, payload, headers={}
                )
            except Exception as e:
                print(f"[ERROR] 우회 패턴 테스트 실패 ({payload.name}): {e}")
                continue

    """ 개별 우회 패턴 테스트 """
    async def _test_bypass_pattern(self, original_url, query, parsed_url, original_redirect_uri, payload, headers):
        
        print(f"[SCAN] 우회 패턴 테스트: {payload.name}")
        
        # 우회 URL 생성
        bypassed_uri = payload.mutate(original_redirect_uri)
        
        # 새로운 쿼리 파라미터 구성
        modified_query = query.copy()
        modified_query["redirect_uri"] = [bypassed_uri]
        new_query_string = urlencode(modified_query, doseq=True)
        test_url = urlunparse(parsed_url._replace(query=new_query_string))
        
        # 요청 전송
        response = await self._send_request(test_url, headers)

        # 응답 분석
        await self._analyze_response(original_url, test_url, bypassed_uri, response, payload)

    """ 응답 분석 및 취약점 판단 """
    async def _analyze_response(self, original_url, test_url, bypassed_uri, response, payload):
        status = response['status']
        location = response['location']
        
        # 리다이렉트 응답이 아니면 스킵
        if status not in [301, 302, 303, 307, 308]:
            return
            
        # Location 헤더에서 code 추출
        auth_code = self._extract_code_from_location(location)
        
        if auth_code and not self._is_baseline_valid(bypassed_uri, original_url):
            # 취약점 발견 시에만 로그
            print(f"[🎯 VULNERABILITY] {payload.name} 우회 성공!")
            await self._report_vulnerability(original_url, test_url, bypassed_uri, location, auth_code, payload)


    """ 취약점 보고서 생성 """
    async def _report_vulnerability(self, original_url, test_url, bypassed_uri, location, auth_code, payload):
        # payload가 문자열인지 객체인지 확인
        if hasattr(payload, 'name'):
            pattern_name = payload.name
            pattern_description = payload.description
        else:
            pattern_name = str(payload)
            pattern_description = "Unknown bypass pattern"
            
        description = (
            f"Redirect URI 우회 취약점 발견!\n\n"
            f"-- 상세 정보 --:\n"
            f"• 우회 패턴: {pattern_name}\n"
            f"• 설명: {pattern_description}\n"
            f"• 원본 URL: {original_url}\n"
            f"• 우회된 redirect_uri: {bypassed_uri}\n"
            f"• 테스트 URL: {test_url}\n"
            f"• 리다이렉트 위치: {location}\n"
            f"• 발급된 인가 코드: {auth_code[:10]}...\n\n"
        )
        
        report_data = [{
            "target": target.load(),
            "status": "CRITICAL",  
            "title": "Redirect URI Bypass Vulnerability",
            "description": description,
            "uri": test_url  # uri 필드 추가
        }]
        
        save_report(report_data)
        print(f"[🎯 CRITICAL] Redirect URI 우회 취약점 발견 및 보고 완료!")
        print(f"[INFO] 패턴: {pattern_name}, 우회 URI: {bypassed_uri}")