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HTTPS 완전정복 김기영 / Founder and CEO kiyoung.kim@flyhigh-x.com FlyHigh Co., LTD. / 주식회사플라이하이

Cipher Suite ClientHello 지원하는 TLS version ServerHello Cipher suite 목록 [session ID] TLS version 결정 선택한 Cipher suite Client Cert Request Server Certificate Client Certificate [session ID] Certificate Verify Change Cipher Spec Client Finished Message Change Cipher Spec Certificate Verify Server Finished Message FlyHigh all rights reserved 6

다음은 Cipher Suite 안전한 Cipher Suite - https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml Value Description DTLS-OK Reference 0x00,0x9E TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 Y [RFC5288] 0x00,0x9F TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 Y [RFC5288] 0xC0,0x2B TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 Y [RFC5289] 0xC0,0x2C TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 Y [RFC5289] 0xC0,0x2F0x2F TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 AES SHA256 Y [RFC5289] 0xC0,0x30 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 Y [RFC5289] 0xC0,0xA2 TLS_ DHE_ RSA_ WITH_ AES_ 128_ CCM_ 8 Y [RFC6655] 0xC0,0xA3 TLS_DHE_RSA_WITH_AES_256_CCM_8 Y [RFC6655] 0xC0,0xAC TLS_ECDHE_ECDSA_WITH_AES_128_CCM Y [RFC7251] 0xC0,0xAD TLS_ECDHE_ECDSA_WITH_AES_256_CCM Y [RFC7251] 0xC0,0xAE TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 Y [RFC7251] 0xC0,0xAF TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8 Y [RFC7251] FlyHigh all rights reserved 8

Cipher Suite 구조 TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 키교환 authentication 암호모드무결성 순방향비밀성 (Forward Secrecy) 앞알고리즘명의뒤에 E 가붙은놈만 서버인증서버인증서의알고리즘대로설정하면됨 RSA, ECDSA, DSA 현실적으로 AES128 이최적 없으면 3DES GCM/CCM 없으면 CBC SHA256 이상만안전 없으면 SHA ECDHE, DHE FlyHigh all rights reserved 9

국내에서는 HTTPS 를어떻게하고있나? 클라이언트와무관한 Cipher Suites 설정, 들쑥날쑥한보안강도설정, Forward Secrecy 무시 ( 은행 ) SHA1 인증서 AES256_CBC, SHA1, RSA SHA1 인증서, TLS1.0, RC4, SHA1, RSA TLS1.0 AES256_CBC, SHA1. RSA FlyHigh all rights reserved 11

이미오래전부터했어야하지만 정책적으로이미정해진일정 SHA-1 서명,2 년,3 년인증서주문불가. SHA-1 인증서발급의유효기간은 2016년 12월 31일로제한 11. 2014 4 년, 5 년다년인증서발급중단. 인증서재발급은최대 39 개월로제한 03 2015 SHA-1 인증서발급및재발급중단 12. 2015 Microsoft 는 SHA-1 서명발급된모든 SSL, CA 인증서신뢰중단 01. 2016 FlyHigh Co., Ltd all rights reserved. 18

인증 서버인증서 SSLCipherSuite ECDHE-ECDSA-AES128-SHA256:AES128-GCM-SHA256:HIGH:+TLSv1.2:!MD5:!aNULL or SSLCipherSuite ECDHE-RSA-AES128-SHA256:AES128-GCM-SHA256:HIGH:+TLSv1.2:!MD5:!aNULL SSLCertificateFile "${SRVROOT}/conf/ssl/flyhigh.com.crt SSLCertificateKeyFile "${SRVROOT}/conf/ssl/flyhigh.com.key" FlyHigh all rights reserved 19

HTTPS 에대한공격 주요취약점 취약점내용대상 취약한키유도 MD5 ~SSL 3.0 Cipher Suite Downgrade handshake ~SSL 3.0 POODLE Attack CBC + Downgrade SSL 3.0 RC4 Attack SSL/TLS Truncation attack 로그아웃차단 SSL/TLS FREAK attack Logjam attack Heartbleed bug BERserk attack Timing attacks on padding OpenSSL 512-bit DH 무기수출통제정책 OpenSSL 일부제품의 ASN.1 decoding 오류 SSL/TLS SSL/TLS Padding Oracle Attack ~TLS 1.1 AES_GCM 만안전 https://en.wikipedia.org/wiki/arms_export_control_act FlyHigh all rights reserved 23

그래서 TLS Spec 을계속수정하고있다. TLS History : ActiveX를도입했던이유가뭐였었는지도잊었는지 이제는제발흐름을따라가기만이라도서버와클라이언트를안전하게연결하기위한보안프로토콜 TLS 1.0(2246) ----------------------------------------------- 1999( 암호강화, 효율 ) AES Ciphersuites for TLS(3268) --------------------------------------- 2002 TLS Extensions (3546) ------------------------------------------------ 2003 TLS 1.1(4346) ----------------------------------------------- 2006(IV 명시 ) TLS Extensions (4366) ------------------------------------------------ 2006 ECC Cipher Suites TLS(4492) ------------------------------------------ 2006 TLS 1.2(5246) ----------------------------------------------- 2008(SHA256 도입 ) TLS Authorization Extensions(5878) ----------------------------------- 2010 TLS Renegotiation Indication Extension(5746) ------------------------- 2010 Prohibiting Secure Sockets Layer (SSL) Version 2.09(6176) ------------ 2011 TLS Fallback SCSV for Preventing Protocol Downgrade Attacks(7507) ---- 2015 Prohibiting RC4 Cipher Suites(7465) ---------------------------------- 2015 Deprecating SSL Version 3.0(7568) ------------------------------------ 2015 TLS Session Hash and Extended Master Secret Extension(7627) ---------- 2015 TLS 1.3(draft 9)---------------------------------------------- 2015(RSA-PSS, SHA1 X) The SHA-3 standard was released by NIST on August 5, 2015. 조만간반영되겠죠.. FlyHigh all rights reserved 24

HTTPS 만가지고는안전하게지킬수가없다. 웹을더욱안전하게하기위해서 W3C 와 IETF 는지속적으로새로운보완기술을도입하고있다 Considerations for Web Transaction Security(2084)------- 1997 The Web Origin Concept(6454)---------------------------- 2011 HTTP Strict Transport Security(6797)-------------------- 2012 Public Key Pinning Extension for HTTP(7469)------------- 2015 System for Cross-domain Identity Management(7642) ------ 2015 Content Security Policy Pinning ------------------------ 2015 Content Security Policy Level 2 ------------------------ 2015 FlyHigh all rights reserved 25

HTTPS 성능과 Mixed Contents 30~40% 는느려진다. 특히 CPU 의부하가크다 가속장비사용 : 컨텐츠관리 Image 를 http 로처리 : 모든브라우저에서허용했음, iframe 랩핑 의도하지않은정보유출 http://www.securitee.org/files/mixedinc_isc2013.pdf FlyHigh all rights reserved 27

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