Bug 1303428

Summary: Checksum calculation may lead to memory exhaustion
Product: [Retired] Fedora Documentation Reporter: Ansgar Wiechers <redhat>
Component: install-guideAssignee: Pete Travis <me>
Status: CLOSED DUPLICATE QA Contact: Fedora Docs QA <docs-qa>
Severity: low Docs Contact:
Priority: unspecified    
Version: develCC: me, pbokoc, zach
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Hardware: All   
OS: Windows   
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Last Closed: 2016-02-02 14:30:41 UTC Type: Bug
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Description Ansgar Wiechers 2016-01-31 17:24:19 UTC 
Description of problem:

Chapter 3.3.1 of the Installation Guide[1] ("Verifying checksums on Windows systems") suggests to pass the image as a byte array to the ComputeHash() method for calculating the SHA-256 checksum:

> $download_checksum = [System.BitConverter]::ToString($sha256.ComputeHash([System.IO.File]::ReadAllBytes("$PWD\$image"))).ToLower() -replace '-', ''

This reads the entire image into memory and may thus result in memory exhaustion (System.OutOfMemoryException), depending on the size of the image and the available memory in the computer running the verification.


Solution:

Read the image as a stream[2] instead of a byte array.

> $stream = (Get-Item "$PWD\$image").OpenRead()
> $hash = $sha256.ComputeHash($stream)
> $stream.Close()
> $download_checksum = [System.BitConverter]::ToString($hash).ToLower() -replace '-'


 [1]: https://docs.fedoraproject.org/en-US/Fedora/23/html/Installation_Guide/sect-verifying-images.html
 [2]: https://msdn.microsoft.com/en-us/library/xa627k19.aspx
Comment 1 Pete Travis 2016-02-02 14:30:41 UTC 

*** This bug has been marked as a duplicate of bug 1175759 ***