Apache server reverse proxy: increase file upload limit - apache

Question

I'm configuring a httpd to perform as a reverse proxy which should allow file uploads as well. Average file size is around 20MB. With basic configurations I could only upload files of max size 128KB.
After referring some materials, I installed modsecurity plugin to enable uploading files with max allowance of 30 MB.
In the mod_security.conf file, I have:
SecRuleEngine On
SecRequestBodyAccess On
SecRequestBodyLimit 31457280
SecRequestBodyNoFilesLimit 131072
SecRequestBodyInMemoryLimit 1048576
SecRequestBodyLimitAction Reject
SecRule REQBODY_ERROR "!#eq 0" "id:'200001', phase:2,t:none,log,deny,status:400,msg:'Failed to parse request body.',logdata:'%{reqbody_error_msg}',severity:2"
But if I try to upload even 1MB file, I get the below error:
[:error] [pid 7877] [client 10.192.10.186:47406] [client 10.192.10.186] ModSecurity: Multipart parsing error (init): Multipart: Invalid boundary in C-T (malformed). [hostname "<host>"] [uri "<uri>"] [unique_id "YmE-3e7SizASbXjV8cTWfQAAAAQ"]
[proxy:error] [pid 7877] (32)Broken pipe: [client 10.192.10.186:47406] AH01084: pass request body failed to 10.192.21.143:443
[proxy_http:error] [pid 7877] [client 10.192.10.186:47406] AH01097: pass request body failed to 10.192.21.143:443 () from 10.192.10.186 ()
The questions I have are:
Am I using the correct plugging?
What is the error in the above configuration?

Answer 1

OWASP ModSecurity Core Rule Set dev-on-duty here. Your error is the first alert message: "Multipart parsing error (init): Multipart: Invalid boundary in C-T (malformed)." The rest is Apache reacting to the ModSecurity parsing abort.
Based on my experience with ModSecurity I am confident we're facing a malformed multipart request. Try to submit a multipart request with curl to see if it works out. If it does, as I suspect, you need to look at your client. Probably by taking a very close look at the request body and the Content-Type header.