用户keychain上保存的还是就的验证密码，但是用户已用新密码登陆系统一个多月了，也不记得旧密码，因此某些app启动时会要求输入keychan的密码。因此只能重建keychain了。
* Close all applications and choose Go to Folder from the Go menu in the Finder-> Library
* Enter this path: ~/Library/Keychains
* Select all items in this Keychain folder and drag them to the Trash.
* Restart the computer immediately. After the user logs back in, a
new login keychain should have been created. You can verify this by
opening Keychain Access (in the Utilities folder in the Applications
folder), and checking to see that there‘s a keychain named login in the
source list. It should be unlocked automatically when the user logs in.
原文：http://helpdesk.blog.51cto.com/219783/1588129