Overview
Kerberos是一个第三方认证机制，用户和服务（known as principals）通过kerberos server (known as the Key Distribution Center, or KDC)认证彼此。KDC有三部分：
- A database of principals and their Kerberos passwords
- An Authentication Server (AS) which performs the initial authentication and isssues a TGT
- A Ticket Granting Server (TGS) that issues subsequent service tickets based on the initial TGT
User principal向AS请求认证。AS返回用用户kerberos password加密的TGT。直到ticket过期，用户都可以用该TGT向TGS申请service tickets。
由于cluster resource（hosts or services）不能每次提供password来解密TGT，他们使用keytab，一种从数据库中导出并存储在本地、包含resource principal's authentication credentials的特殊文件。
安装和配置 KDC
- 启动Kerberos 认证需要安装 KDC 服务器和必要的软件。安装KDC 的命令可以在任何机器上执行。
yum -y install krb5-server krb5-lib krb5-auth-dialog krb5-workstation
- 接着，在集群中的其他节点上安装Kerberos client和命令
yum -y install krb5-lib krb5-auth-dialog krb5-workstation
- 编辑 KDC 配置的realms，AD(active directory)
krb5.conf 文件包含 KDCs、admin 服务器的地址，是当前 realm 和 Kerberos 应用的默认配置，该配置将主机名映射到 Kerberos realms。krb5.conf一般在/etc/krb5.conf
[logging]
default = FILE:/var/log/krb5libs.log
kdc = FILE:/var/log/krb5kdc.log
admin_server = FILE:/var/log/kadmind.log [libdefaults]
default_realm = HADOOP.COM
dns_lookup_realm = false
dns_lookup_kdc = false
ticket_lifetime = 24h
renew_lifetime = 7d
forwardable = true [realms]
HADOOP.COM = {
kdc = node1.hadoop.com
admin_server = node1.hadoop.com
} AD.COM = {
kdc = windc.ad.com
admin_server = windc.ad.com
} [domain_realm]
.hadoop.com = HADOOP.COM
hadoop.com = HADOOP.COM
.ad.com = AD.COM
ad.com = AD.COM [capaths]
AD.COM = {
HADOOP.COM = .
}
realms: HADOOP_COM下的 kdc, admin_server是我们安装KDC的主机地址，AD.COM下的是 Domain Controller主机地址。
domain_realm: 提供domain name 或者主机名字到kerberos realms名字的转换。两者都必须小写。
capaths: cross-realm authentication中，不同 realms 之间需要数据库去创建authentication paths。 这部分定义存储。
- 编辑 kdc.conf，默认在 /var/Kerberos/krb5kdc/kdc.conf。包含 KDC 配置信息，包括发放 Kerberos tickets 时的默认值。
[realms]
HADOOP.COM = {
#master_key_type = aes256-cts
acl_file = /var/kerberos/krb5kdc/kadm5.acl
dict_file = /usr/share/dict/words
admin_keytab = /var/kerberos/krb5kdc/kadm5.keytab
supported_enctypes = aes256-cts:normal aes128-cts:normal des3-hmac-sha1:normal arcfour-hmac:normal des-hmac-sha1:normal des-cbc-md5:normal des-cbc-crc:normal
}
创建数据库和第一个administrator
- 创建 Kerberos database. -s表明将数据库的master server key存在隐藏文件stash file中
kdb5_util create -s
- 添加admin到ACL文件 (编辑 /var/kerberos/krb5kdc/kadm5.acl)
- 创建第一个administrator.
kadmin.local -q "addprinc <username>/admin"
- 启动 Kerberos
service krb5kdc start
service kadmin start
验证安装
# enter kadmin shell
kadmin.local
kadmin.local: listprincs # enter kadmin
kadmin
kadmin: Client not found in Kerberos database kinit <username>/admin klist kadmin
其他Kerberos管理命令
- kadmin: kadmin provides for the maintenance of Kerberos principals, password policies, and service key tables (keytabs).
- kadmind
- kdb5_util: allows an administrator to perform maintenance procedures on the KDC database
- kdb5_ldap_util
- krb5kdc
- kprop
- kpropd
- kproplog
- ktutil：The ktutil command invokes a command interface from which an administrator can read, write, or edit entries in a keytab or Kerberos V4 srvtab file.
- k5srvutil
- sserver
kadmin and kadmin.local are command-line interfaces to the Kerberos V5 administration system. They provide nearly identical functionalities; the difference is that kadmin.local directly accesses the KDC database, while kadmin performs operations using kadmind