OpenVPN: EC ne-ED — kungani la magama engeyona isitebhisi samandla

Beka ec, ed, ecdh, ecdsa, auth kanye nohlu lwezinhlelo zokubethela ze-TLS eduze komunye kuphrofayela eyodwa, futhi ifayela liqala ukubonakala njengoknobhu yamandla enezindawo eziyisithupha. Akunjalo. Igama ngalinye liphendula umbuzo ohlukile, futhi amaphrofayela amabili ahluke kokukodwa kuzo akusho ukuthi elinye linamandla noma libuthaka kunelinye. Ukuhlela amagama ngomsebenzi ewawohlo owenza kuthatha cishe iminithi emihlanu futhi kuvimbela iningi lezinguquko ezimbi abantu abazenza kukho ukulungiselelwa okusebenzayo.

Ukuhlelwa okungezansi kuqala ekudidekeni uqobo, bese kusakazeka ngaphandle kwezinto zephrofayela ezinquma ngempela ukuthi yini evikela ithrafikhi yakho. Isigaba ngasinye sithatha ukufunda okungalungile kanye bese sikhombisa ukuthi igama lixhunywe ngempela kuni.

Izinhlamvu ezimbili, imibuzo emibili ehlukene

Ipheya edala ingxabano enkulu i-EC ne-ED, futhi ingxabano ivamise ukucabanga ukuthi ziyizimpendulo eziphikisanayo zombuzo owodwa. Azikho ngisho ku-eksisi eyodwa. I-EC ichaza umndeni wezibalo: i-cryptography yomugqa oyi-ellipse, lapho ukuphepha kuvela khona ebunzimeni be-logarithm ehlukile emugqeni hhayi emkhakheni omkhulu we-finite.

I-ED ichaza ukuma komugqa ngaphakathi kwalowo mndeni. Imigqa yama-Edwards ehlanekezelwe iyisethulo esikhethelwe isivinini kanye nokumelana namaphutha amaningi okusetshenziswa, futhi i-Ed25519 yigama abantu abavamise ukuqondisisa. Lo mugqa awuyona imbangi ye-cryptography yomugqa oyi-ellipse; uyindlela eyodwa yokubhala umugqa oyi-ellipse. Ukufunda i-ED ngokuthi “i-EC entsha futhi enamandla kakhulu” yindlela yokuqala engalungile, futhi konke okulandela ngokuvamile akulungile ngendlela efanayo.

Ukusayina nokushintshanisa ukhiye kuyimisebenzi ehlukene

Lapho umbuzo womndeni usulungisiwe, amagama asele ahlukana abe yimikhamo emibili engalokothi ibambisane. Umkhawulo owodwa uyasayina, omunye uvumelana ngemfihlo eyabiwe.

I-EdDSA ne-ECDSA zombili ziyasayina, kodwa ziyizinhlelo ezihlukene ezinamafomethi okhiye ahlukene, ngakho-ke isitifiketi esikhishwe kwesinye asikwazi ukusetshenziswa njengokwesinye. I-EdDSA ichazelwe iqoqo elincane lemigqa; i-P-256 ayikho kulolo qoqo, yingakho isitifiketi se-P-256 siqinisekiswa nge-ECDSA futhi asikaze siqinisekiswe nge-Ed25519.

Umkhawulo wokushintshanisa awunakho okulingana okubizwa nge-EdDH. Isivumelwano sesikhashana kukhiye we-Curve25519 yi-X25519, futhi lokho yi-ECDH enomugqa othile, njengoba kunjalo nge-P-256. I-Ed25519 isho ngokuqinile uhlelo lokusayina, nakuba leli gama lisetshenziswa ngokuxekethile ekushintshaniseni ngoba imigqa emibili ihlobene: isimo se-Edwards esisetshenziselwa ukusayina kanye nesimo se-Montgomery esisetshenziselwa i-X25519 zichaza iqembu elifanayo eliyisisekelo.

Kungani iphrofayela ye-EC ingenayo ifayela le-dh

Ifayela le-dh liqukethe amapharamitha akhiqizwe ngaphambili e-Diffie-Hellman yomkhakha we-finite, futhi lawo mapharamitha akhona ngoba inombolo enkulu eyinhloko kanye nomkhiqizi kufanele kuvele ndawana thize. Ukushintshanisa komugqa oyi-ellipse akuzidingi: umugqa oqanjwe ngegama uyisethi yamapharamitha uqobo, futhi izinhlangothi zombili zivele ziyazi. Yingakho konke iphrofayela ye-EC ingashiya lo myalelo.

Izimo ezimbili zisakhiqiza umugqa we-dh kuphrofayela ebukeka isesimanje ngenye indlela. Okokuqala isilaleli sesibili noma uzakwethu omdala ocwaninga ngempela amaqembu omkhakha we-finite. Okwesibili umbhalo osele okopishwe kusifanekiso senkathi ye-RSA futhi ongakaze ususwe. Iphrofayela eqamba umugqa wokushintshanisa kodwa isalayisha ifayela le-dh lamabhithi angu-2048 ayiphephile kakhulu ngoba yenze lokho; ithwala into engasetshenziswanga.

I-TLS 1.3 isusa ukushintshanisa ukhiye egameni

Qhathanisa i-TLS_AES_256_GCM_SHA384 ne-TLS-ECDHE-ECDSA-WITH-AES-256-GCM-SHA384 futhi igama elifushane libonakala njengokwehliswa. Ukuhlela kabusha igama, futhi isizathu sisesakhiweni: i-TLS 1.3 isusa i-RSA emile kanye nokushintshanisa ukhiye kwe-Diffie-Hellman yomkhakha we-finite, ngakho-ke ukushintshanisa komugqa oyi-ellipse kwesikhashana kuyisimo sodwa esisele esingeyona i-PSK. Ukulibiza kuyo yonke isethi kungaphinda iqiniso elifanayo izikhathi eziyishumi nambili.

Uhlobo lwesitifiketi lwanyamalala egameni ngesizathu esihlobene. Ku-1.3 isitifiketi siqinisekisa isiginesha yokuxhawula izandla, hhayi isivumelwano sokhiye, ngakho-ke asisakhethi isethi. Yingakho futhi kukhona uhlu olwahlukile lwezinhlelo zokubethela lwe-1.3 kukho ukulungiselelwa: amasethi aqanjwa kabusha futhi ahlelwa kabusha, awancishwa amandla.

Umphumela owodwa kufanele ushiwo ngokucacile. I-ECDHE iyi-algorithm yokushintshanisa ukhiye futhi ayikaze ibe ukubethela. Isethi echazwa ngokuthi “yi-ellipse” isho okuthile ngendlela izinhlangothi ezimbili ezifike ngayo ekhiyeni elabiwe, futhi ayisho lutho ngokuphelele mayelana nokuthi yini ebethela i-payload ngemva kwalokho.

I-auth iqinisekisa amaphakethe, hhayi ama-payload

Umyalelo we-auth ukhetha i-digest ye-HMAC eqinisekisa amaphakethe, futhi inani layo elijwayelekile ngokomlando i-SHA1. Ngokubethela kwedatha okungewona i-AEAD, i-OpenVPN ibala i-digest phezu kombhalo obethelwe bese iwufaka ekugcineni, okuwukuhlelwa kokubethela-kuqala-bese-kwenza-i-MAC okwenza ukukhohlisa kokugcwalisa kungasebenzi.

Inganekwane lapha ukuthi ukukhulisa i-auth iye ku-SHA512 kuqinisa umhubhe. Lokho akukhulisi amandla okubethela, futhi uma ukubethela kwedatha okuvunyelwene ngakho kuyimodi ye-AEAD efana ne-AES-256-GCM, i-digest ayisetshenziswa nhlobo emaphaketheni edatha. Umaka we-GCM usuqinisekisa wona, futhi inani le-auth lishiyelwa i-HMAC yesiteshi sokulawula kanye nanoma yikuphi ukubethela okungewona i-AEAD okusasetshenziswa.

Ngakho-ke lo myalelo ubalulekile, kodwa ubalulekile endaweni encane kunendawo yawo efayeleni ebonisa. Ukuhlola ukuthi yikuphi ukubethela okuvunyelwene ngakho ngempela kukutshela ukuthi kusebenza noma cha.

Funda iphrofayela ngomkhawulo, hhayi ngezinga

Imibuzo emithathu ihlukanisa lezi zendlalelo ngokucacile, futhi ngamunye uphendulwa ingxenye ehlukile yesikhathi esivunyelwene ngaso. Yikuphi ukubethela okuvikela i-payload? Yimuphi umaka noma i-digest eqinisekisa iphakethe ngalinye, futhi ingabe ukubethela okusetshenziswayo kudinga ngisho okukodwa? Isitifiketi sikabani esivale ukuxhawula izandla, futhi ingabe isiteshi sokulawula sibuye sivikelwe i-tls-auth noma i-tls-crypt?

Akukho lutho ku-EC noma ilebula le-ED okunquma noma yikuphi kwalokhu kuthathu, futhi igama lesethi lodwa alinqumi lutho. Umphumela ovunyelwene ngawo uwubufakazi bodwa, ngakho-ke funda lokho esikhundleni sokuqagela amandla emagameni:

openssl x509 -in client.crt -noout -text | grep -E 'Signature Algorithm|Public Key Algorithm'
grep -i 'control channel' /var/log/openvpn.log

Umyalelo wokuqala ukutshela ukuthi isitifiketi sakho sisebenzisa luphi uhlelo lokusayina ngempela, futhi yiyo kuphela indlela ethembekile yokwazi ukuthi usebenzisa i-ECDSA noma i-Ed25519. Owesibili ukhombisa umugqa wesiteshi sokulawula iklayenti eliwubhalile kulo seshini, kufaka phakathi inguqulo ye-TLS kanye nesethi eyavunyelwana ngayo. Uma ukulungiswa kwephrofayela kungakwazi ukuthethelelwa ngomunye wale miphumela emibili, cishe kuwushintsho lwegama hhayi lwempahla.