Returning large binary to browswer via CGI

• Oct 8, 2012

• #2

feherke

Programmer

Aug 5, 2002

9,541

RO

Hi

Hard to say anything as you posted no CGI code so far.

Anyway, a generic advice : if not using the CGI module, try to set [tt]binmode[/tt].

Feherke.
[link feherke.github.com/]

http://feherke.github.com/

[/url]

 

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• Oct 8, 2012

• Thread starter
• #3

dolfantimmy

MIS

Oct 8, 2012

5

US

Here's the perl code. Binmode is being used.

#!/usr/bin/perl

print "Content-type: application/octet-stream\n";
print "Content-Disposition: attachment\; filename=\"kickstart.iso\"\n";
print "Content-Transfer-Encoding: binary\n\n";

binmode(STDOUT);

exec("mkisofs -r -T -J -V \"Redhat KSBoot\" -b pub/isolinux/isolinux.bin -c pub/isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -v .");

 

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• Oct 8, 2012

• #4

feherke

Programmer

Aug 5, 2002

9,541

RO

Hi

I was able to reproduce the problem.

But I am quite sure the problem is not with the transfer. If I redirect [tt]exec[teal]([/teal][green]"mkisofs --all-that-stuff > /tmp/dolfantimmy.iso"[/green][teal]);[/teal][/tt], the resulted file will be also 34816 byte long.

As [tt]mkisofs[/tt]'s STDERR is not redirected, it gets written to the web server's error log file. There is a line :

error_log said:

[Mon Oct 08 19:43:00 2012] [error] [client 192.168.2.81] mkisofs: Permission denied. Error opening boot image file 'pub/isolinux/isolinux.bin' for update.

Click to expand...

If I set write permission on the pub/isolinux/ directory and the isolinux.bin file for the web server's user, the error message disappears and the downloaded file's size seems to be correct.

I have no experience with [tt]mkisofs[/tt], but I would give a try to the above.


Feherke.
[link feherke.github.com/]

http://feherke.github.com/

[/url]

 

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• Oct 8, 2012

• Thread starter
• #5

dolfantimmy

MIS

Oct 8, 2012

5

US

Thanks so much for trying to help. Essentially the mkisofs is building a kickstart installation cd image.

I suspect you have a permissions issue on your side. The above perl script is called iso.pl If I execute the following....

perl ./iso.pl > foo.iso

a 4GB is generated as I would suspect.

 

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• Oct 8, 2012

• #6

feherke

Programmer

Aug 5, 2002

9,541

RO

Hi

dolfantimmy said:

If I execute the following....

perl ./iso.pl > foo.iso

a 4GB is generated as I would suspect.

Click to expand...

Also if you [tt]su - webserveruser[/tt] first ? ( I mean, become to user with who's permissions the web server runs. Search the configuration files for [tt]User[/tt] directive to find out the given user. )


Feherke.
[link feherke.github.com/]

http://feherke.github.com/

[/url]

 

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• Oct 8, 2012

• Thread starter
• #7

dolfantimmy

MIS

Oct 8, 2012

5

US

I am running as root

 

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• Oct 8, 2012

• #8

feherke

Programmer

Aug 5, 2002

9,541

RO

Hi

dolfantimmy said:

I am running as root

Click to expand...

You mean, you have a [tt]User root[/tt] directive in your web server configuration ? You read the warning before setting that, right ?

httpd documentation said:

Security
Don't set [tt]User[/tt] (or [tt]Group[/tt]) to root unless you know exactly what you are doing, and what the dangers are.

Click to expand...

( Apache HTTP Server Version 2.2 Documentation | Apache MPM Common Directives | User Directive )

Anyway, one thing you can still do : check your web server's logs.

Feherke.
[link feherke.github.com/]

http://feherke.github.com/

[/url]

 

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• Oct 10, 2012

• Thread starter
• #9

dolfantimmy

MIS

Oct 8, 2012

5

US

Feherke,

I must have overlooked your suggestion regarding the write bit on isolinux directory isolinux.bin file. That solved the problem. Thanks a TON!!!

 

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