Ukulahleka kwe-Ping ku-VPN: hlanganisa izicelo ze-Echo ngaphambi kwephesenti

Ukuqoshwa okukodwa kuqukethe izicelo ze-Echo eziyisithupha nezimpendulo ezintathu, futhi othile ubhala ukulahleka kwamaphakethe kwamaphesenti angu-50 kuthikithi. Leyo nombolo ingaba yiqiniso kokuqoshwa futhi ingabi yiqiniso kumhubhe. Lezo zicelo eziyisithupha zingase zibe zezingxoxo ezimbili ezihlukene ezinemibandela emibili ehlukene yokulethwa. Zihlanganise ngaphambi kokuhlukanisa, futhi isilinganiso siyoyeka ukuba yingxenye ethakazelisayo yombiko.

Isinyathelo 1: hlukanisa imifudlana ngomthombo nendawo ekuyiwa kuyo

Isicelo se-Echo sithwala umthombo nendawo ekuyiwa kuyo, futhi lezo zinkambu ezimbili zinquma ukuthi singesiphi isingxoxo. I-probe ekhiqizwa yisango isebenzisa ikheli lomhubhe wesango, kuyilapho i-probe edluliselwa egameni lomsingathi we-LAN igcina ikheli lalowo msingathi. Uhlangothi olukude lungaba nomzila wokubuya komunye hhayi komunye, okwenza amaqembu amabili aziphathe ngendlela ehlukene ngenxa yezizathu ezingahlobene nomhubhe.

Hlukanisa ukuqoshwa kulezo zinkambu ngaphambi kokubala noma yini, futhi gcina indawo ekuyiwa kuyo njengengxenye yokhiye. Imifudlana emibili eya kubalingani abahlukene ayinakuqhathaniswa ngisho noma yabelana ngomthombo.

Bhala amaqembu namanani awo, ngoba isinyathelo esilandelayo sinquma ukuthi yiziphi izimpendulo ezingeqembu liphi. Iqembu elinezicelo ezintathu futhi lingenayo impendulo ehambisanayo liyinto etholakele. Iqembu elinezicelo ezintathu nezimpendulo ezintathu iwumugqa wesisekelo.

Isinyathelo 2: fanisa ngesihlonzi nokulandelana

Ifomethi ye-Echo ku-RFC 792 ithwala isihlonzi nenombolo yokulandelana, futhi izithatha njengezinkambu ezihlanganisa impendulo nesicelo sayo. Zombili ziyadingeka kulo msebenzi. Inombolo yokulandelana iyodwa ayiyingqayizivele, ngoba abathumeli noma izinqubo ezahlukene bangase basebenzise futhi inani elifanayo ngaphakathi kwewindi elilodwa lokuqoshwa. Isihlonzi sinciphisa umthumeli kanti ukulandelana kunciphisa indawo, futhi ipheya ndawonye yilona elenza ukufanisa kube yinto engavikeleka.

Impendulo iguqula isiqondiso samakheli esicelo sayo, ngakho ukufanisa kuyipheya lesicelo-nempendulo hhayi ama-tuple amabili afanayo. Qhathanisa umthombo wesicelo nendawo ekuyiwa kuyo yempendulo nendawo ekuyiwa kuyo yesicelo nomthombo wempendulo, bese uqinisekisa ukuthi isihlonzi nokulandelana kuyavumelana.

Gcina newindi lokubuka, ngoba ukuqoshwa okude kungaqukatha ukusetshenziswa kabusha okusemthethweni kwazo zombili izinkambu. Ukusika iwindi kube ukuqhuma okukodwa kususa ingxenye enkulu yalokho kungacaci. Kwenze futhi izibalo zikwazi ukuphindwa yinoma ubani ofunda ithikithi.

tshark -r capture.pcap -Y 'icmp.type == 8' -T fields -e frame.time -e ip.src -e ip.dst -e icmp.ident -e icmp.seq
tshark -r capture.pcap -Y 'icmp.type == 0' -T fields -e frame.time -e ip.src -e ip.dst -e icmp.ident -e icmp.seq

Isinyathelo 3: qhathanisa ama-tuple emngceleni ofanayo

Uma ukuhumusha kwamakheli wenethiwekhi kungaphakathi kwephoyinti lokuqoshwa nomlingani, amakheli esicelweni nasempendulweni azohluka ngokwakhiwa. Qhathanisa ama-tuple emngceleni owodwa, noma thwala ukumephu ngokusobala ukuze umehluko ubalwe. Ukuhlanganisa izicelo zangaphambi kokuhumusha nezimpendulo zangemva kokuhumusha kwakha ukungafani okungakaze kube khona ocingweni.

Nquma umngcele ngaphambi kokuba uqale ukubala, futhi uwusho embikweni ukuze umuntu olandelayo akwazi ukuphinda ukuhlanganisa. Ukuqoshwa kwelinye uhlangothi lweklayenti nelinye ohlangothini lweseva kuyimigcele emibili ehlukene. Ngakunye kuphendula umbuzo ohlukile mayelana nokuthi impendulo yanyamalala kuphi.

Iqembu lamaprobe ahumushiwe lizuza njengefa isimo sokuqoshwa kwedivayisi yokuhumusha uqobo, okungaba yisizathu sangempela sokuthi impendulo ingafiki. Hlola leso simo ngaphambi kokusola indlela engaphesheya kwayo.

tcpdump -ni any icmp and host 10.90.0.1 -c 20
tshark -r capture.pcap -Y 'icmp' -T fields -e ip.src -e ip.dst -e ip.ttl | head -20

Isinyathelo 4: shono ukuthi ukuqoshwa kungafakazela ini futhi akukwazi ukufakazela ini

Isikhala esibonakele asifakazeli ukuthi umsingathi okude wathula. Iphoyinti lokuqoshwa lingabona isiqondiso esisodwa kuphela, isihlungi singadiliza impendulo, noma ibhafa yagcwala phakathi kwewindi. Ngakunye kwalokho kuletha ukungabikhona okufanayo nesiphetho esihlukile.

Qopha indawo yokuqoshwa, isisho sesihlungi nezibali zokudiliza eceleni kwezibalo, ngoba isilinganiso ngaphandle kwazo asikwazi ukucwaningwa. Yileyo mitsara emithathu eyenza inombolo ikwazi ukuvikeleka kamuva.

Bese uhlukanisa lokho ukubuka okukufakazayo nalokho okukusikiselayo, emishwaneni emibili hhayi eminye eyodwa. Umshwana wokuqala usho izibalo nomngcele. Owesibili usho umcabango nokuthi yini engawuqinisekisa.

Lapho umbuzo uwukuthi ingabe indlela ethile idiliza amaphakethe, iprobe elawulwayo enekheli lomthombo elicacile iwubufakazi obuqinile kunokubala okungenzi lutho kwethrafikhi exubile. Yithumele kusuka emshinini ofanayo, ngesikhathi esifanayo, kumlingani ofanayo. Shintsha okuguquguqukayo okukodwa futhi ukuqhathanisa kuyahlala.

Bika amaqembu nomngcele olandelayo

Umbiko unemitsara emithathu: incazelo yeqembu, izibalo ezihambisanayo ngaphakathi kweqembu ngalinye, nomngcele lapho ukuqhathanisa kwenziwa khona. Khona-ke umfundi angabona ukuthi iqembu elilodwa laphendula ngokuphelele kanti elinye alizange liphendule, okukhomba umzila noma imvume hhayi ukulahleka okungahleliwe.

Namathisela ifayela lokuqoshwa nezisho zesihlungi ukuze ukuhlanganisa kukwazi ukuphindwa. Isifinyezo esingenalo ifayela isimangalo, hhayi umphumela.

ping -c 5 -I 10.80.0.6 10.90.0.1
ping -c 5 -I 10.30.0.25 10.90.0.1
tshark -r capture.pcap -Y 'icmp.type == 8 || icmp.type == 0' -T fields -e ip.src -e ip.dst -e icmp.ident -e icmp.seq | sort | uniq -c | head

Lapho iqembu elilodwa likhombisa izimpendulo ezinhlanu kanti elinye alibonisi lutho, okutholakele ukuthi umthombo owodwa unomzila wokubuya osebenzayo kanti omunye awunawo. Lelo yithikithi elingcono kakhulu kunephesenti elixubile, futhi liqondisa ukuhlola okulandelayo emzileni wokubuya hhayi esenzakalweni se-VPN esingahlobene.