Golangで作るFTPプロキシサーバ

ʙय़ͩʂ౦ژͩʂʂʂ߹ίϯͩʂʂʂʂ̍̍ʙ QZBNB(.01FQBCP *OD (P$POGFSFODF4QSJOH (PMBOHͰ࡞Δ '51ϓϩΩγαʔό

ϗεςΟϯάࣄۀ෦νʔϑςΫχΧϧϦʔυ ࢁԼ࿨඙!QZBNB

-JOVYͷ౷߹Ϣʔβʔ؅ཧ 50.-ܗࣜ )551 +40/ -%"1΍%#ͷ؅ཧͷӡ༻ෛՙ ѻ͍΍͍͢ϑΥʔϚοτ ൚༻ੑɾ֦ுੑ

ϖύϘ෱Ԭ

ࠓ೔࿩͢͜ͱ wࠓɺ೥य़ɺ'51͕೤͍ w'51ϓϩΩγαʔόΛ։ൃͨ͠ͱ͖ͷ5JQT

ͳͥࠓ'51͕೤͍ͷ͔ʁ

4 ੈքతͳ , ج४Ͱ : Ϡό͍

4 ੈքతͳ , ج४Ͱ : Ϡό͍ 4FSWFS 4FSWJDF 4ZOD

Ϩϯαόͷߏ੒্ͷ՝୊ 44) '51 VTFS VTFSDPOUFOUT ෺ཧαʔό

Ϩϯαόͷߏ੒্ͷ՝୊ VTFSDPOUFOUT 44) '51 VTFS VTFSDPOUFOUT 44) '51 ౰ࣾϨϯλϧαʔόαʔϏε͓͍ͯ͸෺ཧαʔόʹ͓٬༷ͷίϯςϯπ͕഑ஔ͞Ε͓ͯΓɺ ෛՙঢ়گͳͲΛؑΈͯɺαʔόҠઃ͢Δࡍʹɺ͓٬༷ͷ'51΍44)ͷ઀ଓઌ͕
มΘͬͯ͠·͏ߏ੒্ͷ՝୊͕͋Δ Ҡઃ

44)͸طʹ044͕ଘࡏ͢Δ wIUUQTHJUIVCDPNUHTTIQJQFS wϢʔβʔ໊ϕʔεͷ44)ϓϩΩγ VTFS" VTFS# TTIQJQFS 4FSWFS" 4FSWFS# Ϣʔβʔ໊ʹԠͯ͡ɺ઀ଓઌΛมߋ

QGUQΛόʔϯ࡞Δ͜ͱͰطଘͷ՝୊Λղܾ wIUUQTHJUIVCDPNQZBNBQGUQ wಈత'51ϓϩΩγ VTFS" VTFS# QGUQ 4FSWFS" 4FSWFS# ೚ҙͷϛυϧ΢ΣΞΛར༻ͯ͠઀ଓઌΛมߋ "1*
.JEEMFXBSF-BZFS

'51 'JMF5SBOTGFS1SPUPDPM wฏจςΩετͷίϚϯυૢ࡞ % ftp 127.0.0.1 2121 Connected to 127.0.0.1.
220 Welcome on ftpserver Name (127.0.0.1:yamashitakazuhiko): test 331 OK Password: 230 Password ok, continue ftp> ls 227 Entering Passive Mode (127,0,0,1,224,164) 150 Using transfer connection drw-rw-rw- 1 ftp ftp 4096 Mar 28 06:38 virtual 226 Closing transfer connection

QGUQ͕໨ࢦ͢ੈք QGUQ PSJHJO DMJFOU 64&3 64&3 0, 0, QGUQ͸֤ίϚϯυʹॲཧΛϑοΫͭͭ͠ɺϓϩΩγ ṖϑοΫ

5$1ίωΫγϣϯΛ ॲཧ͢Δ

OFU-JTUFOͰίωΫγϣϯΛ͏͚Δ OFU-JTUFOFS HPSPVUJOF IBOEMFS HPSPVUJOF IBOEMFS HPSPVUJOF IBOEMFS DPOO DPOO
DPOO listener, _ := net.Listen(“tcp”,”127.0.0.1:21") for { connection, _ := listener.Accept() ɹ // ίωΫγϣϯΛgroutine΁ }

ίωΫγϣϯ͝ͱʹίϚϯυΛಡΈࠐΈॲཧ reader = bufio.NewReader(connection) line, err := reader.ReadString('\n') => line:
USER test ftp> open 127.0.0.1 2121 ftp> user test CVpP3FBEFSΛར༻͢Δ͜ͱͰ ιέοτ͔Βͷಡࠐ͕ศརʹ

ಉ࣌઀ଓ਺؅ཧ͢Δ OFU-JTUFOFS HPSPVUJOF IBOEMFS HPSPVUJOF IBOEMFS HPSPVUJOF IBOEMFS DPOO DPOO
DPOO HPSPVUJOF։࢝࣌ʹΧ΢ϯτΞοϓ͠ɺ HPSPVUJOFͷऴྃ࣌ʹΧ΢ϯτμ΢ϯ͢Δ͜ͱͰ ಉ࣌઀ଓ਺Λ؅ཧ

*EMFλΠϜΞ΢τΛઃ͚Δ͜ͱͰࣗಈ੾அ OFU-JTUFOFS HPSPVUJOF IBOEMFS HPSPVUJOF IBOEMFS HPSPVUJOF IBOEMFS DPOO DPOO
DPOO OFU$POO4FU%FBEMJOFΛར༻͠ɺૢ࡞ͷͳ͍ΫϥΠΞϯτΛ λΠϜΞ΢τॲཧ

OFU$POO4FU%FBEMJOF for { connection.SetDeadline( ɹɹɹtime.Now().Add( ɹɹɹtime.Duration(time.Second.Nanoseconds() * int64(idleTimeout))) ɹ )
// 1ߦͣͭಡΉ line, err := reader.ReadString('\n') // ड͚औͬͨίϚϯυͷॲཧ } %FBEMJOF౸ୡͨ͠৔߹ɺJPUJNFPVU

'51ϓϩΩγ OFU-JTUFOFS HPSPVUJOF IBOEMFS HPSPVUJOF IBOEMFS HPSPVUJOF IBOEMFS DPOO DPOO
DPOO PSJHJO PSJHJO PSJHJO $0.."/% $0.."/% $0.."/% $0.."/% $0.."/% $0.."/% HPSPVUJOF୯ҐͰϓϩΩγίωΫγϣϯΛுΔ

'51ίϚϯυΛॲཧ͢Δ

'51ʹ͸ଟ͘ͷίϚϯυ͕ଘࡏ w64&3ίϚϯυϨεϙϯε w'&"5ίϚϯυ/Ϩεϙϯε w1"47ίϚϯυϨεϙϯε ίωΫγϣϯʂʂʂ̍ ίϚϯυ͝ͱͷڍಈͷҧ͍͔ΒϓϩΩγͳͷʹ ϓϩτίϧͷཧղ͕ඞཁ

'51͸ίωΫγϣϯར༻͢Δ w'51͸ίϚϯυͷ΍ΓऔΓΛ͢Δ੍ޚίωΫγϣϯͱɺσʔλͷసૹ Λߦ͏సૹίωΫγϣϯͷ̎ͭΛར༻͢Δ QGUQ PSJHJO DMJFOU -*45 -*45 ίϚϯυૢ࡞Ҏ֎ΛσʔλసૹίωΫγϣϯͰߦ͏ EBUBDPOFDUJPO
DPOUSPMDPOOFDUJPO pMFUYU pMFUYU

'51ͷσʔλసૹํࣜ͸ͭ w"DWJWFํࣜαʔό͔ΒσʔλసૹίωΫγϣϯΛுΔ w1BTTJWFํࣜΫϥΠΞϯτ͔ΒσʔλసૹίωΫγϣϯΛுΔ wͲͷϙʔτͰαʔό͕-JTUFOͯ͠Δ͔Λ1BTTJWFํࣜͷ৔߹͸ɺ1"47 ίϚϯυͰ௨஌͢Δ DMJFOU QGUQ EBUBDPOFDUJPO DMJFOU QGUQ
EBUBDPOFDUJPO "DUJWFํࣜ 1BTTJWFํࣜ

1"47ίϚϯυ͸த਎Λॻ͖׵͑Δ &OUFSJOH1BTTJWF.PEF º
QGUQ PSJHJO DMJFOU 1"47 1"47

σʔλίωΫγϣϯͷϓϩΩγ QGUQ PSJHJO DMJFOU σʔλίωΫγϣϯཁٻ

σʔλίωΫγϣϯͷϓϩΩγ QGUQ PSJHJO DMJFOU σʔλίωΫγϣϯཁٻ σʔλίωΫγϣϯཁٻ

σʔλίωΫγϣϯͷϓϩΩγ QGUQ PSJHJO DMJFOU σʔλίωΫγϣϯཁٻ σʔλίωΫγϣϯཁٻ 999Ͱ-JTUFO։࢝

σʔλίωΫγϣϯͷϓϩΩγ QGUQ PSJHJO DMJFOU σʔλίωΫγϣϯཁٻ σʔλίωΫγϣϯཁٻ 999Ͱ-JTUFO։࢝ :::Ͱ-JTUFO։࢝

σʔλίωΫγϣϯͷϓϩΩγ QGUQ PSJHJO DMJFOU σʔλίωΫγϣϯཁٻ σʔλίωΫγϣϯཁٻ 999Ͱ-JTUFO։࢝ :::Ͱ-JTUFO։࢝ ϑΝΠϧసૹཁٻ

σʔλίωΫγϣϯͷϓϩΩγ QGUQ PSJHJO DMJFOU σʔλίωΫγϣϯཁٻ σʔλίωΫγϣϯཁٻ 999Ͱ-JTUFO։࢝ :::Ͱ-JTUFO։࢝ ϑΝΠϧసૹཁٻ ϑΝΠϧసૹཁٻ

σʔλίωΫγϣϯͷϓϩΩγ QGUQ PSJHJO DMJFOU σʔλίωΫγϣϯཁٻ EBUBDPOFDUJPO σʔλίωΫγϣϯཁٻ 999Ͱ-JTUFO։࢝ :::Ͱ-JTUFO։࢝ 999UPQGUQ΁σʔλసૹ։࢝
ϑΝΠϧసૹཁٻ ϑΝΠϧసૹཁٻ

σʔλίωΫγϣϯͷϓϩΩγ QGUQ PSJHJO DMJFOU σʔλίωΫγϣϯཁٻ DMJFOU͔Βݟͨ৔߹ɺQGUQ͸αʔόɺ ΦϦδϯ͔Βݟͨ৔߹ɺQGUQ͸ΫϥΠΞϯτͷڍಈ͕ٻΊΒΕΔ EBUBDPOFDUJPO EBUBDPOFDUJPO σʔλίωΫγϣϯཁٻ
999Ͱ-JTUFO։࢝ :::Ͱ-JTUFO։࢝ :::UPDMJFOU΁σʔλసૹ։࢝ 999UPQGUQ΁σʔλసૹ։࢝ ϑΝΠϧసૹཁٻ ϑΝΠϧసૹཁٻ

ɹɹEPXOMPBEHPSPVUJOF func proxy() { … // ϦϨʔ༻ͷgoroutineΛىಈ eg.Go(func() error {
return relay(ctx, server, client) }) eg.Go(func() error { return relay(ctx, client, server) }) // ׬ྃ·Ͱ଴ͪ߹ΘͤΔ if err := eg.Wait(); err != nil { return err } } HSPVUJOFͰϓϩΩγ PSJHJO DMJFOU ɹɹVQMPBEHPSPVUJOF QGUQ

ී௨ʹ΍Δͱ͏·͍͔͘ͳ͍ func relay(from, to net.Conn) error { buff := make([]byte,
BUFFER_SIZE) for { select { case <-ctx.Done(): return ctx.Err() default: if err := from.Read(buff); err != nil { return errr } if err := to.Write(b); err != nil { return errr } } } } Ξοϓϩʔυɺ΋͘͠͸μ΢ϯϩʔυͷऴྃͰ ྆ํίωΫγϣϯΛऴ͍ྃͨ͠ DUY%POF Ͱ΋ऴྃ͠ͳ͍

ɹɹEPXOMPBEHPSPVUJOF ϑΝΠϧΞοϓϩʔυͷॲཧ PSJHJO DMJFOU ɹɹVQMPBEHPSPVUJOF QGUQ 3FBE 8SJUF 3FBE 8SJUF
Ξοϓϩʔυ࣌ɺVQMPBEHSPVUJOF͸3FBE͕ൃੜ͢Δ͕ɺ EPXOMPBEHSPVUOF͸3FBE͕ൃੜ͠ͳ͍

3FBE͸ϒϩοΩϯά func relay(from, to net.Conn) error { buff := make([]byte,
BUFFER_SIZE) for { select { case <-ctx.Done(): return ctx.Err() default: if err := from.Read(buff); err != nil { return errr } if err := to.Write(b); err != nil { return errr } } } } 3FBEͰϒϩοΩϯά͞ΕΔ͕Ώ͑ʹɺ ࣍ͷϧʔϓ΁͍͔ͳ͍

ϊϯϒϩοΩϯά3FBE for { select { case <-ctx.Done(): return ctx.Err() case
err := <-errChan: return err // ಡࠐgoroutineΛىಈ͠ɺඇಉظͰಡΈࠐΉ case b := <-read: _, err := to.Write(b) if err != nil { return err } } } νϟϯωϧܦ༝ͰಡΈࠐΉ͜ͱʹΑΓ ϊϯϒϩοΩϯά΁

-FBLDPOUFYU8JUI$BODFM NBJO HPSPVUJOF HPSPVUJOF SFUVSO DUY%POF ctx, done := context.WithCancel(context.Background())
defer done() eg, ctx := errgroup.WithContext(ctx) // ϦϨʔ༻ͷgoroutineΛىಈ eg.Go(func() error { return p.relay(ctx, server, client) }) eg.Go(func() error { return p.relay(ctx, client, server }) // ׬ྃ·Ͱ଴ͪ߹ΘͤΔ if err := eg.Wait(); err != nil { return err } EPOF

-FBLDPOOFDUJPO$MPTF HPGVOD \ GPS\
O FSSGSPN3FBE CV⒎ JGFSSOJM\ FSS$IBOFSS SFUVSO ^ SFBECV⒎<O> ^ ^ ίωΫγϣϯΤϥʔ͕ൃੜɺ ϒϩοΫ͕ղআ͞ΕΔ for { select { case <-ctx.Done(): from.Close() case err := <-errChan: return err case b := <-read: _, err := to.Write(b) if err != nil { return err } } } ૬ํͷసૹ͕ऴΘΓ࣍ୈ ίωΫγϣϯΛ Ϋϩʔζ Τϥʔνϟϯωϧܦ༝ Ͱॲཧऴྃ

࣮૷ґଘ

ϓϩτίϧʹ͸࣮૷ґଘ͕͖ͭ΋ͷ w3'$ͷղऍͷҧ͍ʹΑΓɺඍົʹ࣮૷͕ҟͳΔ wओཁͳαʔόɺΫϥΠΞϯτͷ࠷௿ݶͷಈ࡞ςετ͸͢΂͖

·ͱΊ

4 ੈքతͳ , ج४Ͱ : ΍͹͍

ϓϩτίϧαʔό͸ϓϩτίϧ࣮૷ɺ 3'$Λͻͨ͢Β ಡΉͱ࡞ΕΔ

σʔλసૹϓϩτίϧ͸ ϊϯϒϩοΩϯά໋

HPSPVUJOFϦʔΫͤͪ͞ΌͩΊɺ ໿ଋͩΑʁ

5IBOLZPV ࠷৽ͷ࠾༻৘ใΛνΣοΫˠ !QC@SFDSVJU

Golangで作るFTPプロキシサーバ

Golangで作るFTPプロキシサーバ

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