How to parse audit.log using logstash

I want to use logstash to collect a log file, and the format of the file was like this:

type=USER_START msg=audit(1404170401.294:157): user pid=29228 uid=0 auid=0 ses=7972 subj=system_u:system_r:crond_t:s0-s0:c0.c1023 msg='op=PAM:session_open acct="root" exe="/usr/sbin/crond" hostname=? addr=? terminal=cron res=success'

Which filter should i use to match the line? or there is another way to handle it.

Any help would be appreciated.

Used the pattern below to match the line with grok debugger , but still got a No matches message.

type=%{WORD:audit_type} msg=audit\(%{NUMBER:audit_epoch}:%{NUMBER:audit_counter}\): user pid=%{NUMBER:audit_pid} uid=%{NUMBER:audit_uid} auid=%{NUMBER:audit_audid} subj=%{WORD:audit_subject} msg=%{GREEDYDATA:audit_message}

But when i removed subj=%{WORD:audit_subject} msg=%{GREEDYDATA:audit_message}, it successed and got a JSON object like this.

{
  "audit_type": [
    [
      "USER_END"
    ]
  ],
  "audit_epoch": [
    [
      "1404175981.491"
    ]
  ],
  "BASE10NUM": [
    [
      "1404175981.491",
      "524",
      "1465",
      "0",
      "0"
    ]
  ],
  "audit_counter": [
    [
      "524"
    ]
  ],
  "audit_pid": [
    [
      "1465"
    ]
  ],
  "audit_uid": [
    [
      "0"
    ]
  ],
  "audit_audid": [
    [
      "0"
    ]
  ]
}

Don't know why subj and msg can't work on.