《Extensible Messaging and Presence Protocol (XMPP): Core》阅读笔记（二）

最新推荐文章于 2019-02-13 10:33:19 发布

最新推荐文章于 2019-02-13 10:33:19 发布 · 73 阅读

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本文详细介绍了服务器间使用SASL（Simple Authentication and Security Layer）进行验证的过程，并阐述了服务器回拨机制的具体实现。包括初始化、响应、认证挑战与响应等关键步骤，以及一种不安全的验证方式——服务器回拨的详细过程。

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服务器到服务器SASL验证示例：

Step 1: Server1 initiates stream to Server2:

<stream:stream

xmlns='jabber:server'

xmlns:stream='http://etherx.jabber.org/streams'

to='example.com'

version='1.0'>

Step 2: Server2 responds with a stream tag sent to Server1:

<stream:stream

xmlns='jabber:server'

xmlns:stream='http://etherx.jabber.org/streams'

from='example.com'

id='s2s_234'

version='1.0'>

Step 3: Server2 informs Server1 of available authentication mechanisms:

<stream:features>

<mechanismsxmlns='urn:ietf:params:xml:ns:xmpp-sasl'>

<mechanism>DIGEST-MD5</mechanism>

<mechanism>KERBEROS_V4</mechanism>

</mechanisms>

</stream:features>

Step 4: Server1 selects an authentication mechanism:

<authxmlns='urn:ietf:params:xml:ns:xmpp-sasl'

mechanism='DIGEST-MD5'/>

Step 5: Server2 sends a BASE64 encoded challenge to Server1:

<challengexmlns='urn:ietf:params:xml:ns:xmpp-sasl'>

cmVhbG09InNvbWVyZWFsbSIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIixxb3A9

ImF1dGgiLGNoYXJzZXQ9dXRmLTgsYWxnb3JpdGhtPW1kNS1zZXNz

</challenge>

The decoded challenge is:

realm="somerealm",nonce="OA6MG9tEQGm2hh","

qop="auth",charset=utf-8,algorithm=md5-sess

Step 5 (alt): Server2 returns error to Server1:

<failurexmlns='urn:ietf:params:xml:ns:xmpp-sasl'>

<incorrect-encoding/>

</failure>

</stream:stream>

Step 6: Server1 sends a BASE64 encoded response to the challenge:

<responsexmlns='urn:ietf:params:xml:ns:xmpp-sasl'>

dXNlcm5hbWU9ImV4YW1wbGUub3JnIixyZWFsbT0ic29tZXJlYWxtIixub25j

ZT0iT0E2TUc5dEVRR20yaGgiLGNub25jZT0iT0E2TUhYaDZWcVRyUmsiLG5j

PTAwMDAwMDAxLHFvcD1hdXRoLGRpZ2VzdC11cmk9InhtcHAvZXhhbXBsZS5v

cmciLHJlc3BvbnNlPWQzODhkYWQ5MGQ0YmJkNzYwYTE1MjMyMWYyMTQzYWY3

LGNoYXJzZXQ9dXRmLTgK

</response>

The decoded response is:

username="example.org",realm="somerealm","

nonce="OA6MG9tEQGm2hh",cnonce="OA6MHXh6VqTrRk","

nc=00000001,qop=auth,digest-uri="xmpp/example.org","

response=d388dad90d4bbd760a152321f2143af7,charset=utf-8

Step 7: Server2 sends another BASE64 encoded challenge to Server1:

<challengexmlns='urn:ietf:params:xml:ns:xmpp-sasl'>

cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZAo=

</challenge>

The decoded challenge is:

rspauth=ea40f60335c427b5527b84dbabcdfffd

Step 7 (alt): Server2 returns error to Server1:

<failurexmlns='urn:ietf:params:xml:ns:xmpp-sasl'>

<invalid-authzid/>

</failure>

</stream:stream>

Step 8: Server1 responds to the challenge:

<responsexmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>

Step 8 (alt): Server1 aborts negotiation:

<abortxmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>

Step 9: Server2 informs Server1 of successful authentication:

<successxmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>

Step 9 (alt): Server2 informs Server1 of failed authentication:

<failurexmlns='urn:ietf:params:xml:ns:xmpp-sasl'>

</failure>

</stream:stream>

Step 10: Server1 initiates a new stream to Server2:

<stream:stream

xmlns='jabber:server'

xmlns:stream='http://etherx.jabber.org/streams'

to='example.com'

version='1.0'>

Step 11: Server2 responds by sending a stream header to Server1 along with any additional features (or an empty features element):

<stream:stream

xmlns='jabber:server'

xmlns:stream='http://etherx.jabber.org/streams'

from='example.com'

id='s2s_345'

version='1.0'>

<stream:features/>

服务器回拨

这是一种单向的，不安全的验证方式。

具体过程：

1， 服务器A发送流头部给服务器B:

<stream:stream

xmlns:stream='http://etherx.jabber.org/streams'

xmlns='jabber:server'

xmlns:db='jabber:server:dialback'>

2,服务器B回送一个应答给A,包含了此次交互的ID:
<stream:stream

 xmlns:stream='http://etherx.jabber.org/streams'

 xmlns='jabber:server'

 xmlns:db='jabber:server:dialback'

id='457F9224A0...'>

3,服务器A发送一个回拨key给B

<db:result

 to='Receiving Server'

 from='Originating Server'>

98AF014EDC0...

</db:result>

4,服务器B同验证服务器C建立TCP连接,向C发送流头部：

<stream:stream

 xmlns:stream='http://etherx.jabber.org/streams'

 xmlns='jabber:server'

 xmlns:db='jabber:server:dialback'>

5，C回送应答：

<stream:stream

 xmlns:stream='http://etherx.jabber.org/streams'

 xmlns='jabber:server'

 xmlns:db='jabber:server:dialback'

 id='1251A342B...'>

6，B发送验证key的请求

<db:verify

 from='Receiving Server'

 to='Originating Server'

 id='457F9224A0...'>

98AF014EDC0...

</db:verify>

7，验证服务器验证key是否合法：

<db:verify

from='Originating Server'

to='Receiving Server'

type='valid'

id='457F9224A0...'/>

<db:verify

from='Originating Server'

to='Receiving Server'

type='invalid'

id='457F9224A0...'/>

8，B通知A结果：

<db:result

 from='Receiving Server'

 to='Originating Server'

 type='valid'/>

上面这个示例只是验证了从A到B的流是否合法，但不能保证从B到A是否合法，因此需要在反方向再进行一次验证。