Kerberos是一种计算机网络授权协议，用来在非安全网络中，对个人通信以安全的手段进行身份认证。 采用客户端/服务器结构，并且能够进行相互认证，即客户端和服务器端均可对对方进行身份认证。
关键要素
KDC:Key Distribution Center – Each user and service shares a secret key with the KDC – The KDC generates and distributes session keys – Communicating parties prove to each other that they
KDC 包含两部分：
– Authentication Server (AS) ● Issues “Ticket-Granting Tickets” (TGT) – Ticket Granting Server (TGS) ● Issues service tickets
交互过程
- client向KDS发用户名和服务端名称
- KDC回应TGT，使用用户密码加密；
- client输入密码，解密TGT
- 到手的TGT，用来和KDC通信（我已经有TGT了，属于被你信任的列表中，给我我想要的东西吧），进一步获取service tickets. img:k1.jpg
- KDC返回用户service tickets，
- 用户拿service tickets和Server通信，请求授权；
- server端授权完成，建立session；
交互流程图： 
用户命令
- kinit # 与KDC通信，请求授权
- klist # 查看已授权列表
[email protected]:~$ klist
Ticket cache: FILE:/tmp/krb5cc_1098
Default principal: [email protected]
Valid starting Expires Service principal
06/21/2016 11:43:29 06/22/2016 11:43:26 krbtgt/[email protected] # TGT
06/21/2016 11:43:45 06/22/2016 11:43:26 host/[email protected] # host service ticket
06/21/2016 11:43:45 06/22/2016 11:43:26 host/[email protected]
Kerberos principals
Clients (users or services) are identified by “principals” Principals look like: primary/[email protected]
– Primary: user or service name – Instance: optional for user principals, but required for service principals – Realm: the Kerberos realm
Examples:
– User: [email protected] – Service: imap/[email protected]
如何搭建一个Kerberos KDC？
准备工作：
- Configure NTP (time synchronization) across all machines
- Configure DNS
- Configuration files
– /etc/krb5.conf – /etc/kadm5.acl
- Prepare the Kerberos database – Initialize the Kerberos database – Add administrator’s principal – Start the KDC and KDC administration processes
- Create user principals – Note: service principals are created when configuring your other services to support Kerberos authentication
如何搭建一个Kerberos 客户端？
- Configuration file /etc/krb5.conf You can just copy this from the KDC
- Service principals
- PAM (Pluggable Authentication Modules) （重点是这个，我们需要配置登录到服务器，就配置这个） – Needed if you want to be able to authenticate users logging into this machine via Kerberos
参考
- http://www.logicprobe.org/~octo/pres/pres_kerberos.pdf
- http://web.mit.edu/kerberos/krb5-1.12/doc/index.html