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Credential Caching in FTP 7.0 and FTP 7.5

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I've seen a few situations where people that are using the FTP 7.0 and FTP 7.5 service have noticed that it takes a while for their password changes to be reflected by the FTP service. To put this another way, here are the typical symptoms that people describe to me:

  • A user successfully logs into their FTP site using their username and password
  • The user logs out of their FTP site
  • The user changes their password
  • The user attempts to log into their FTP site using their username and their new password, but this fails
  • The user can successfully log into their FTP site using their username and their old password
  • (Note: As a corollary, restarting the FTP service fixes the symptoms)

Here's why this happens: to help improve the performance for authentication requests, the FTP service caches the credentials for successful logins. (The cache duration is set to 15 minutes by default.) This means that if you change your password, your changes may not be reflected for the cache duration.

The good news is, the FTP credential cache settings can be changed easily, and I have documented all of the settings for FTP caching in the IIS configuration reference at the following URLs:

Quoting and paraphrasing the above documentation, there are the two settings that you can configure on the <credentialsCache> element:

Attribute Description
enabled Optional Boolean attribute. true if credential caching is enabled; otherwise, false. The default value is true.
flushInterval Optional uint attribute. Specifies the cache lifetime, in seconds, for credentials that are stored in the cache. Note: This value must be between 5 and 604,800 seconds. The default value is 900.

What this means to you is - you can completely disable credential caching, or you can specify a different timeout. For example, on several of my development servers I often disable credential caching; this allows me to change passwords whenever I want, which is very useful when I am creating custom authentication providers. For my production servers I tend to stick with the default values, although I might change those values when I'm troubleshooting a problem.

I usually configure the settings from a command line or a batch file, although the articles that I listed earlier have steps for using the IIS Manager to change the settings for FTP credential caching. Just the same, here are some examples for setting the values by using appcmd.exe:

How to Disable FTP Credential Caching

 cd /d "%SystemRoot%\System32\Inetsrv"
appcmd.exe set config -section:system.ftpServer/caching /credentialsCache.enabled:"False" /commit:apphost
net stop FTPSVC
net start FTPSVC

How to Specify a Custom Timeout for FTP Credential Caching

 cd /d "%SystemRoot%\System32\Inetsrv"
appcmd.exe set config -section:system.ftpServer/caching /credentialsCache.enabled:"True" /commit:apphost
appcmd.exe set config -section:system.ftpServer/caching /credentialsCache.flushInterval:"300" /commit:apphost
net stop FTPSVC
net start FTPSVC

I hope this helps. ;-]