服务器到服务器SASL验证示例：
Step 1: Server1 initiates stream to Server2:
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<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
to='example.com'
version='1.0'>
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Step 2: Server2 responds with a stream tag sent to Server1:
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<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
from='example.com'
id='s2s_234'
version='1.0'>
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Step 3: Server2 informs Server1 of available authentication mechanisms:
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<stream:features>
<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<mechanism>DIGEST-MD5</mechanism>
<mechanism>KERBEROS_V4</mechanism>
</mechanisms>
</stream:features>
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Step 4: Server1 selects an authentication mechanism:
<auth xmlns='urn:ietf:params:xml:ns:xmpp-sasl'
mechanism='DIGEST-MD5'/>
Step 5: Server2 sends a BASE64 encoded challenge to Server1:
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<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
cmVhbG09InNvbWVyZWFsbSIsbm9uY2U9Ik9BNk1HOXRFUUdtMmhoIixxb3A9
ImF1dGgiLGNoYXJzZXQ9dXRmLTgsYWxnb3JpdGhtPW1kNS1zZXNz
</challenge>
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The decoded challenge is:
realm="somerealm",nonce="OA6MG9tEQGm2hh","
qop="auth",charset=utf-8,algorithm=md5-sess
Step 5 (alt): Server2 returns error to Server1:
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<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<incorrect-encoding/>
</failure>
</stream:stream>
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Step 6: Server1 sends a BASE64 encoded response to the challenge:
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<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
dXNlcm5hbWU9ImV4YW1wbGUub3JnIixyZWFsbT0ic29tZXJlYWxtIixub25j
ZT0iT0E2TUc5dEVRR20yaGgiLGNub25jZT0iT0E2TUhYaDZWcVRyUmsiLG5j
PTAwMDAwMDAxLHFvcD1hdXRoLGRpZ2VzdC11cmk9InhtcHAvZXhhbXBsZS5v
cmciLHJlc3BvbnNlPWQzODhkYWQ5MGQ0YmJkNzYwYTE1MjMyMWYyMTQzYWY3
LGNoYXJzZXQ9dXRmLTgK
</response>
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The decoded response is:
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username="example.org",realm="somerealm","
nonce="OA6MG9tEQGm2hh",cnonce="OA6MHXh6VqTrRk","
nc=00000001,qop=auth,digest-uri="xmpp/example.org","
response=d388dad90d4bbd760a152321f2143af7,charset=utf-8
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Step 7: Server2 sends another BASE64 encoded challenge to Server1:
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<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
cnNwYXV0aD1lYTQwZjYwMzM1YzQyN2I1NTI3Yjg0ZGJhYmNkZmZmZAo=
</challenge>
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The decoded challenge is:
rspauth=ea40f60335c427b5527b84dbabcdfffd
Step 7 (alt): Server2 returns error to Server1:
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<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<invalid-authzid/>
</failure>
</stream:stream>
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Step 8: Server1 responds to the challenge:
<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>
Step 8 (alt): Server1 aborts negotiation:
<abort xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>
Step 9: Server2 informs Server1 of successful authentication:
<success xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>
Step 9 (alt): Server2 informs Server1 of failed authentication:
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<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
<aborted/>
</failure>
</stream:stream>
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Step 10: Server1 initiates a new stream to Server2:
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<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
to='example.com'
version='1.0'>
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Step 11: Server2 responds by sending a stream header to Server1 along with any additional features (or an empty features element):
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<stream:stream
xmlns='jabber:server'
xmlns:stream='http://etherx.jabber.org/streams'
from='example.com'
id='s2s_345'
version='1.0'>
<stream:features/>
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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:
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<stream:stream
xmlns:stream='http://etherx.jabber.org/streams'
xmlns='jabber:server'
xmlns:db='jabber:server:dialback'>
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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...'/>
or
<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。
本文转自Phinecos(洞庭散人)博客园博客，原文链接：http://www.cnblogs.com/phinecos/archive/2008/07/15/1243470.html，如需转载请自行联系原作者
