Bug 52975

Summary: Receiving files is suboptimal
Product: Apache httpd-2 Reporter: Mikhail T. <mi+apache>
Component: mod_ftpAssignee: Apache HTTPD Bugs Mailing List <bugs>
Status: RESOLVED LATER    
Severity: normal Keywords: MassUpdate
Priority: P2    
Version: 2.2.22   
Target Milestone: ---   
Hardware: PC   
OS: FreeBSD   

Description Mikhail T. 2012-03-23 00:57:03 UTC
While a new file is being received, its mode is set to 0, but its name is already that of the new file. If, for whatever reason, httpd dies during transmission, a zero-mode file under the desired name will remain on the filesystem.

Also, sites, which mirror FTP-content periodically can occasionally suffer from races -- if the mirroring program (such as rsync) runs, while a file-upload is in progress, it will try, but fail to mirror it.

A possible solution would be to open new files under a different name. For example, if the (new) keyword specifies a prefix:

FTPTemporaryFilePrefix       .in-flight-

the new file foo/bar can be opened as (using apr_file_mktemp()):

foo/.in-flight-35CH21bar

Then, upon completion of upload, it can be renamed into foo/bar, if the uploaded was successful, or deleted, if the upload failed. (The renaming is conveniently atomic.)

The existing files can be similarly-handled, when a complete overwrite is requested:

1. Receive under new (temporary) name.
2. Rename the existing name into another temporary name.
3. Rename the temporary name from 1. into the desired name.
4. Unlink the temporary name from 2.

This approach will help preserve file-integrity during the (potentially lengthy) uploads and also help tools like rsync, who can be told to skip any file, that matches certain pattern (such as ".in-flight-*").

If this is deemed acceptable in principle, I can begin working on a patch.
Comment 1 William A. Rowe Jr. 2018-11-07 21:09:36 UTC
Please help us to refine our list of open and current defects; this is a mass update of old and inactive Bugzilla reports which reflect user error, already resolved defects, and still-existing defects in httpd.

As repeatedly announced, the Apache HTTP Server Project has discontinued all development and patch review of the 2.2.x series of releases. The final release 2.2.34 was published in July 2017, and no further evaluation of bug reports or security risks will be considered or published for 2.2.x releases. All reports older than 2.4.x have been updated to status RESOLVED/LATER; no further action is expected unless the report still applies to a current version of httpd.

If your report represented a question or confusion about how to use an httpd feature, an unexpected server behavior, problems building or installing httpd, or working with an external component (a third party module, browser etc.) we ask you to start by bringing your question to the User Support and Discussion mailing list, see [https://httpd.apache.org/lists.html#http-users] for details. Include a link to this Bugzilla report for completeness with your question.

If your report was clearly a defect in httpd or a feature request, we ask that you retest using a modern httpd release (2.4.33 or later) released in the past year. If it can be reproduced, please reopen this bug and change the Version field above to the httpd version you have reconfirmed with.

Your help in identifying defects or enhancements still applicable to the current httpd server software release is greatly appreciated.