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mod_nss now supports changing the SSL renegotiation buffer size
This update adds the `NSSRenegBufferSize` parameter to the _mod_nss_ package. The parameter allows users to configure the amount of memory to be used for buffering a POST request when a per-location SSL renegotiation is required. Previously, _mod_nss_ did not support this functionality, which caused such requests to fail with the following message recorded in Apache logging:
request body exceeds maximum size for SSL buffer, could not buffer message body to allow SSL renegotiation to proceed.
`NSSRenegBufferSize` accepts buffer size in bytes. The default value is 128K. Setting `NSSRenegBufferSize` to `0` disables the buffering.
Description of problem: When POSTing a 1MB file, I received an HTTP 413 (Request Entity Too Large) and got the following error in Apache logging:
request body exceeds maximum size for SSL buffer, could not buffer message body to allow SSL renegotiation to proceed.
I am not able to increase the renegotiation buffer size.
Version-Release number of selected component (if applicable):
Issue applies to all currently released mod_nss versions at the time of creating this bug.
How reproducible: Always
Steps to Reproduce:
1. POST 1MB file to https URL (SSL must be configured using mod_nss)
Actual results: Receive HTTP 413 on client. See error stating that "body exceed maximum size for SSL buffer" on server side.
Expected results: File should be POSTed to server successfully.
Additional info: Need to be able to configure renegotiation buffer size just like mod_ssl's SSLRenegBufferSize.
The default buffer size is 128k (131072 bytes).
To verify create a CGI to accept the POST. I created one that simply echo's the data back and put it into /var/www/cgi-bin:
#!/usr/bin/perl
binmode(STDOUT);
binmode(STDIN);
print "Content-Type: text/plain\r\n";
print "\r\n";
while (<>) {
print $_;
}
Modify nss.conf and set a specific cipher for cgi-bin which will cause a re-negotiation:
<Directory "/var/www/cgi-bin">
NSSCipherSuite +rsa_3des_sha
NSSOptions +ExportCertData +CompatEnvVars +StdEnvVars
</Directory>
Restart Apache
Generate a file that is within the default range:
$ tr -dc A-Za-z0-9 </dev/urandom | head -c 131072 > /tmp/data
Try to get the file:
$ wget -O - --no-check-certificate --post-file /tmp/data https://`hostname`:8443/cgi-bin/echo.pl
It should succeed.
Try a bigger file:
$ tr -dc A-Za-z0-9 </dev/urandom | head -c 131073 > /tmp/data
$ wget -O - --no-check-certificate --post-file /tmp/data https://`hostname`:8443/cgi-bin/echo.pl
It should fail with 413 Request Entity Too Large
Edit nss.conf again and set a new, larger buffer size to the cgi-bin Directory block:
NSSRenegBufferSize 1048576
Restart Apache
Try the same POST again:
$ wget -O - --no-check-certificate --post-file /tmp/data https://`hostname`:8443/cgi-bin/echo.pl
It should succeed
Comment 11Abhijeet Kasurde
2016-02-18 06:37:46 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://rhn.redhat.com/errata/RHBA-2016-0751.html