Extensible Messaging and Presence Protocol (XMPP)

Extensible Messaging and
Presence Protocol (XMPP)
2016.3.1
1
Sean

Extensible Messaging and Presence
Protocol (XMPP)
• A communication protocol based on XML.
• Designed to be extensible.
• Jeremie Miller began working on the Jabber technology in 1998.
(Originally named Jabber)
2
1999~2000
RFC 3920
RFC 3921
2011
RFC 6120
RFC 6121
RFC 6122
2015
RFC 7622

XMPP的優點
• 因為使用xml，所以不限制訊息內容
• 支援的程式很多
• 很多 open source 可以使用
• 分散式
• 安全
3

XMPP的缺點
• IP 一換，整個連線需重連(驗證重做)
▫ 以手機而言，Wi-Fi/3G 轉換就會換 IP
• 不能傳二進位資訊 (但可透過base64編碼傳送)
4

XMPP RFCs
• RFC 3920 → RFC 6120
Extensible Messaging and Presence Protocol (XMPP): Core
• RFC 3921 → RFC 6121
Extensible Messaging and Presence Protocol (XMPP): Instant
Messaging and Presence
• RFC 6122 → RFC 7622
Extensible Messaging and Presence Protocol (XMPP): Address
Format
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XMPP Architecture
• Distributed client-server architecture
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cyberlink.co
m
google.co
m
sean@cyberlink.com bob@google.com
TC
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TC
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TC
P
TC
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Jabber ID (JID)
• XMPP address
• Bare JID
▫ <localpart@domainpart>
▫ EX: sean@cyberlink.com
• Full JID
▫ <localpart@domainpart/resourcepart>
▫ EX: sean@cyberlink.com/123456789
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XML Stanzas
• iq
▫ Info/query
• message
▫ Send a Message to a JID (a user or a group)
• presence
▫ Broadcast message
8

Open a Stream – Initial Stream
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<?xml version=‘1.0’?>
<stream:stream
to='u.cyberlink.com'
xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:client‘
xml:lang='en'
version='1.0'>
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sean@cyberlink.com cyberlink.co
m
Port:5222

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<?xml version >
<stream:stream
version="1.0"
from="u.cyberlink.com"
id="3053277074"
xml:lang="en“
xmlns:stream='http://etherx.jabber.org/streams' xmlns='jabber:client‘
>
TC
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Open a Stream – Response Stream

Stream Negotiation - Presence
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<presence ….>
<show/>
</presence>
TC
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Stream Negotiation - iq
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<iq id=“1” type=“get”>
…
</iq>
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<iq id=“1” type=“result”>
…
</iq>
type: get, set, result, error

Stream Negotiation - message
13
<message….>
Hello
</message>
TC
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Stream Negotiation – Close Stream
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</stream>
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</stream>

Client Server Communication Overview
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<?xml version='1.0'?>
<stream
from=“samo@cyberlink.com”
to=“cyberlink.com”>
<presence
…>Online</presence>
<iq …>…</iq>
<message
…>Hello</message>
</stream>

Authentication for XMPP
• Transport Layer Security (TLS)
▫ Secure the stream from tampering and eavesdropping.
▫ MUST send a new initial stream header after finish.
• Simple Authentication and Security Layer (SASL)
▫ Authenticate a stream. (U: base64(id+token))
▫ MUST send a new initial stream header after finish.
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Cryptography
• Symmetric
▫ Use the same key for encrypt/decrypt.
▫ Security: Poor
▫ Performance: Good
• Asymmetric
▫ Use public key for encryption and use private for decryption.
▫ Security: Good
▫ Performance: Poor
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TLS
• TLS 1.0
• TLS 1.1
• TLS 1.2
• TLS 1.3 (draft)
• Employ a handshake using asymmetric cipher.
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Stream Header
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<stream
from=“sean@cyberlink.com”
<stream
id=“++TR84Sm6A3hnt3Q065SnAbbk3Y=”
to=“sean@cyberlink.com”
from=“cyberlink.com”>
TC
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m

TLS Negotiation
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<stream:features>
<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'>
<required/>
</starttls>
</stream:features>
TC
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<stream:features xmlns="http://etherx.jabber.org/streams">
<starttls xmlns="urn:ietf:params:xml:ns:xmpp-tls" />
<mechanisms xmlns="urn:ietf:params:xml:ns:xmpp-sasl">
<mechanism>PLAIN</mechanism>
</mechanisms>
</stream:features>
<proceed xmlns="urn:ietf:params:xml:ns:xmpp-tls" />
<failure xmlns="urn:ietf:params:xml:ns:xmpp-tls" />
</stream:stream>
or
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TLS Handshake Protocol

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Client_hello(client_version, session_id, cipher_
suites, compression_methods, )
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PKc PrKc
RNc
RNc
RNc

TC
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Server_hello(client_version, session_id, cipher_ suites,
compression_methods, )
PKc PrKc PKs PrKs
RNsRNc
RNs
RNc RNs

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TC
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Server_Certificate(CA, )
PKc PrKc PKs PrKs
PKs
RNsRNc RNsRNc

25
TC
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PKc PrKc PKs PrKsPKs
Check server certificate
RNsRNcRNsRNc

26
TC
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Client_Certificate(CA, )
PKc
RNsRNcRNsRNc

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TC
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PKc PrKc PKs PrKsPKs PKc
RNsRNc RNsRNcPMS
Generate random
pre-master-secretPMS

28
TC
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Encrypted with
PKs
PKc
RNsRNc RNsRNc
PMS
PMS PMS

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TC
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PKs PrKsPKc
Calculae Master-Secret fromMS RNsRNc
RNsRNc
PMS
PMS
MS

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TC
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m
MS MS
Calculae Master-Secret fromMS RNsRNc PMS

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TC
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1. Change cipher spec
2. Client finish
MS MS

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TC
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1. Change cipher spec
2. Server finish
MS MS

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</mechanisms>
</stream:features>
<proceed xmlns="urn:ietf:params:xml:ns:xmpp-tls" />
<failure xmlns="urn:ietf:params:xml:ns:xmpp-tls" />
</stream:stream>
or
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Restarts stream
34
<stream
from=“samo@cyberlink.com”
<stream
id=“++TR84Sm6A3hnt3Q065SnAbbk2Y=”
to=“samo@cyberlink.com”
from=“cyberlink.com”>
TC
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m

Restarts
• On successful negotiation of a feature that necessitates a stream
restart, both parties MUST consider the previous stream to be
replaced but MUST NOT send a closing </stream> tag and MUST
NOT terminate the underlying TCP connection.
• The initiating entity then MUST send a new initial stream header.
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SASL Negotiation
37
<stream:features
xmlns:stream="http://etherx.jabber.org/streams">
<mechanism>SCRAM-SHA-1-PLUS</mechanism>
<mechanism>SCRAM-SHA-1</mechanism>
</mechanisms>
</stream:features>
TC
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m

SASL Negotiation
38
</mechanisms>
</stream:features>
<auth xmlns="urn:ietf:params:xml:ns:xmpp-sasl“
mechanism="PLAIN">
ADc2ODAwMQBkMGY2ZjllMi00YmRlLTQ2ZjItOGI2Yi1lNDM0OTk
2ZjczZGQ=
</auth>
<success xmlns="urn:ietf:params:xml:ns:xmpp-sasl" />
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SASL Negotiation
39
• Restart

Resource Binding
40
<stream:features xmlns:stream="http://etherx.jabber.org/streams">
<bind xmlns="urn:ietf:params:xml:ns:xmpp-bind"/>
</stream:features>
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Resource Binding
41
<bind xmlns="urn:ietf:params:xml:ns:xmpp-bind" />
<session xmlns="urn:ietf:params:xml:ns:xmpp-session" />
</stream:features>
<iq type="set" id="97fe2b99-dfa6-4fa0-a963-f27e840b1adb-1">
<bind xmlns="urn:ietf:params:xml:ns:xmpp-bind">
<resource>mobile</resource>
</bind>
</iq>
<iq type="result" id="97fe2b99-dfa6-4fa0-a963-f27e840b1adb-1">
<bind xmlns="urn:ietf:params:xml:ns:xmpp-bind">
<jid>juliet@im.example.com/mobile</jid>
</bind>
</iq>
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Currently Design for U
• Remove the mechanism of RESTART.
• Add <CLResumed/> for doing SASL and binding again after reconnecting.
42

CLResume: server give info
43
<clresumed xmlns="urn:xmpp:custom:resume"
status="success"
sessionid="g2gEbQAAAAYzMTgwMDFtAAAAD3UuY3liZXJsa
W5rLmNvbW0AAAAkRjg5MjlFMzctRTAwMi00QzdGLTlEOTgt
RjkxNTFGNUQ3NEI5aANiAAAFkmIACeRcYgAM3cE="
expiration="2592000"/>
TC
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Begin Resume
44
sessionid="g2gEbQAAAAYzMTgwMDFtAAAAD3UuY3liZX
JsaW5rLmNvbW0AAAAkRjg5MjlFMzctRTAwMi00QzdGL
TlEOTgtRjkxNTFGNUQ3NEI5aANiAAAFkmIACeRcYgAM3
cE=" />
TC
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m

Resume success
45
status="success"
sessionid="g2gEbQAAAAYzMTgwMDFtAAAAD3UuY3liZXJsa
W5rLmNvbW0AAAAkRjg5MjlFMzctRTAwMi00QzdGLTlEOTgt
RjkxNTFGNUQ3NEI5aANiAAAFkmIACeRcYgAM3cE="
expiration="2592000"/>
TC
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m

XMPP Connection Steps w/o clresume
C -> S stream
C <- S stream / feature:starttls
C -> S starttls
C <- S proceed
C <> S tls handshake
C -> S stream
C <- S stream / feature:sasl
C -> S auth
C <- S auth
C -> S stream
C <- S stream / feature:bind
C -> S bind
C <- S bind

XMPP Connection Steps w/ clresume
(not resume case)
C -> S stream
C -> S starttls
C <- S proceed
C -> S stream
C -> S auth
C <- S auth
C -> S stream
C <- S stream / feature:bind
C -> S bind
C <- S bind
C <- S clresume

XMPP Connection Steps w/ CLResume
(resume case)
C -> S stream
C -> S starttls
C <- S proceed
C -> S stream
C -> S clresume
C <- S clresume

Extensible Messaging and Presence Protocol (XMPP)

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