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abhinay's avatar
abhinay
Icon for Nimbostratus rankNimbostratus
Dec 21, 2022

Request for providing help on setting up an iRule

Hi All,

Can you please let me know how can I accomplish the below requirement with an iRule.

Any requests that use any method and have "cs.exe" or "llisapi.dll" in the URI and also have a query string or form post variable called "fInArgs" that contains the string "%3D%23" should return 403 Forbidden.

Thanks,

Abhinay

  • abhinay  please share how you test in postman. 
    I've tried and it works if the POST body is raw type and looks like this : fInArgs=%3D%23
    This is what rules I am using:

    when HTTP_REQUEST { 
    if { ([class match [HTTP::uri] contains example_uri_1]) and ( [HTTP::query] contains "%3D%23") }{
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    log local0. "deny URI: [HTTP::uri] query:[HTTP::query]"
    }
    if {[HTTP::method] eq "POST"}{
    # Trigger collection for up to 1MB of data
    if {[HTTP::header "Content-Length"] ne "" && [HTTP::header "Content-Length"] <= 1048576}{
    set content_length [HTTP::header "Content-Length"]
    } else {
    set content_length 1048576
    }
    # Check if $content_length is not set to 0
    if { $content_length > 0} {
    HTTP::collect $content_length
    }
    }
    }
    when HTTP_REQUEST_DATA {

    if { [HTTP::method] equals "POST" }{
    # Extract the entire HTTP request body and escape it to become a HTTP::uri string (for easier parsings)
    set http_request_body "?[HTTP::payload]"
    log local0. "http payload: $http_request_body"
    # Try to parse type value from the HTTP request body.
    if { [URI::query $http_request_body fInArgs] equals "%3D%23" } {
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    } }
    }

    if you use application/x-www-form-urlencoded you will have to match this "%253D%2523"

    if { [URI::query $http_request_body fInArgs] equals "%253D%2523" } {
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    }

    or use URI::decode :

    if { [URI::decode [URI::query $http_request_body fInArgs]] equals "%3D%23" } {
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    }

     and if it is a form-data:

    set varB [findstr [HTTP::payload] "fInArgs"]
    if { $varB contains "%3D%23" } {
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    }

     

  • I noticed from other comments in this thread that variable name is fInArgs with an uppercase "i".

    Variable name in my code has a lowercase "L" -- I must have read that wrong before. If you just copy/pasted and didn't fix it, it might not match because of this. 

    Otherwise, I'd expect it to work -- it does in my lab. 

21 Replies

  • Here is an example:

    ltm data-group internal example_uri_1 {
    records {
    cs.exe { }
    llisapi.dll { }
    }
    type string
    }
    when HTTP_REQUEST {
             if { ([matchclass [string tolower [HTTP::uri]] contains example_uri_1]) and ([string tolower [HTTP::query]] contains "%3D%23") }{
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache

    }
    }

    For the form post variable, I think you need to have APM. 

    • NetOpsCommercial's avatar
      NetOpsCommercial
      Icon for Nimbostratus rankNimbostratus

      Thanks for your response mihaic.

       

      I see that you have created a data-group for URIs and calling it in the HTTP_Request along with the HTTP Query string which contains "%3D%23". 

      Can you please let me know how to use this post variable called "fInArgs" in which I can check the string "%3D%23"

       

  • Hi abhinay , 
    As mihaic figured out his iRule , it should meet your requirements. 
    I want to add only this part to specify the ( Query string name and value ) in Requests 
    you can add to mihaic iRule : 

    [URI::query [HTTP::uri] "fInArgs"] equals "%3D%23"]
    
    #add this part after and operator in iRule instead of ([string tolower[HTTP::query]...)
    it is only to be more specified
     

    I think NetOpsCommercial asks for this part , is not it. 

    mihaic , Did you simulated this irule and get its results ? 

  • can you provide what HTTP payload looks like? 

    As far as I understand you need to look for some variable and its value in the HTTP payload.

    • abhinay's avatar
      abhinay
      Icon for Nimbostratus rankNimbostratus

      yes mihaic, the variable I am looking at is "fInArgs" that contains the string "%3D%23"

      Tried your iRule below but this is not working in the HTTP payload

  • Mohamed_Ahmed_Kansoh  is right, we need to remove "string tolower" part.

    I only tested that the syntax is ok. The functionality, no. Did not have time yet.

    Here is the irule with the variable also:(not functional tested):

    ltm data-group internal example_uri_1 {
    records {
    cs.exe { }
    llisapi.dll { }
    }
    type string
    }

    when HTTP_REQUEST {
    if { ([matchclass [string tolower [HTTP::uri]] contains example_uri_1]) and ( [HTTP::query] contains "%3D%23") }{
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache

    }
    }


    when HTTP_REQUEST_DATA {

    if { [HTTP::method] equals "POST" }{
    # Extract the entire HTTP request body and escape it to become a HTTP::uri string (for easier parsings)
    set http_request_body "?[HTTP::payload [HTTP::header value "Content-Length"]]"
    # Try to parse type value from the HTTP request body.
    if { [URI::decode [URI::query $request_body fInArgs]] equals "%3D%23" } {
    log local0. "fInArgs : $fInArgs"
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    }
    }
    }

     

    • abhinay's avatar
      abhinay
      Icon for Nimbostratus rankNimbostratus
      mihaic, URI along with query that contains "%3D%23" combination is working but the below payload with the body that contains %3D%23 doesnt seem to work. As we are decoding the query I tried "=#" too but no luck.
      Any suggestions would be appreaciated

      when HTTP_REQUEST_DATA {

      if { [HTTP::method] equals "POST" }{
      # Extract the entire HTTP request body and escape it to become a HTTP::uri string (for easier parsings)
      set http_request_body "?[HTTP::payload [HTTP::header value "Content-Length"]]"
      # Try to parse type value from the HTTP request body.
      if { [URI::decode [URI::query $request_body fInArgs]] equals "%3D%23" } {
      log local0. "fInArgs : $fInArgs"
      HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
      }
      }
      }



       

      • CA_Valli's avatar
        CA_Valli
        Icon for MVP rankMVP

        I'm noticing this code is missing an HTTP::collect statement, so HTTP_REQUEST_DATA event will never be fired. 
        abhinay  Have you checked my other response yet? 

  • Hello abhinay ,
    I've recently implemented a similar check on one of my customers. Try the following:

     

    when HTTP_REQUEST { 
     if { [HTTP::uri] contains "cs.exe" || [HTTP::uri] contains "llisapi.dll" }{ 
    
        if { [URI::decode [HTTP::query]] contains "flnArgs" }{ 
         set value [findstr [URI::decode [HTTP::query] "flnArgs" 7 &]
    	 if { $value contains "#=" }{
    	   log local0. "violation detected: flnArgs=$value"  
    	   HTTP::respond 403 content "Forbidden" 
    	   
    	   
    	 } else {
         # if URI does not contain parameter, I capture traffic (up to 1MB) and perform this check again on full payload
    
           if {[HTTP::header "Content-Length"] ne "" && [HTTP::header "Content-Length"] <= 1048576}{ 
             set content_length [HTTP::header "Content-Length"]
           } else { set content_length 1048576 }
           if { $content_length > 0} { HTTP::collect $content_length ; set checkpayload 1 }
    	   
         }
      }
    }
    when HTTP_REQUEST_DATA {
      if { $checkpayload }{ 
        set cleanpl [URI::decode [HTTP::payload]]
        set value [findstr $cleanpl "flnArgs" 7 &]
    	if { $value contains "#=" }{
    	   log local0. "violation detected: flnArgs=$value" 
    	   HTTP::respond 403 content "Forbidden" 
    	}
      }	
    }

     

    Notice that I'm decoding URI so %3D%23 will be normalized to #= , this match is more effective IMO

      • CA_Valli's avatar
        CA_Valli
        Icon for MVP rankMVP

        Oops, you're right - I've lost a couple parenthesis in the copy/paste, also #= should be inverted to =#
        Sorry! Fixed below. 

         

         

        when HTTP_REQUEST { 
         if { [HTTP::uri] contains "cs.exe" || [HTTP::uri] contains "llisapi.dll" }{ 
        
            if { [URI::decode [HTTP::query]] contains "flnArgs" }{ 
             set value [findstr [URI::decode [HTTP::query]] "flnArgs" 7 &]
        	 if { $value contains "=#" }{
        	   log local0. "violation detected: flnArgs=$value"  
        	   HTTP::respond 403 content "Forbidden" 
        	 }  
        	} else {
             # if URI does not contain parameter, I capture traffic (up to 1MB) and perform this check again on full payload
        
               if {[HTTP::header "Content-Length"] ne "" && [HTTP::header "Content-Length"] <= 1048576}{ 
                 set content_length [HTTP::header "Content-Length"]
               } else { set content_length 1048576 }
               if { $content_length > 0} { HTTP::collect $content_length ; set checkpayload 1 }
        	   
             }
          }
        }
        when HTTP_REQUEST_DATA {
          if { $checkpayload }{ 
            set cleanpl [URI::decode [HTTP::payload]] 
            set value [findstr $cleanpl "flnArgs" 7 &]
        	if { $value contains "=#" }{
        	   log local0. "violation detected: flnArgs=$value" 
        	   HTTP::respond 403 content "Forbidden" 
        	}
          }	
        }

         

         

        seems to work in my lab

         

        Dec 21 20:14:52 bigip info tmm6[11336]: Rule /Common/iRule_DC <HTTP_REQUEST>: violation detected: flnArgs===#
        Dec 21 20:14:55 bigip info tmm[11336]: Rule /Common/iRule_DC <HTTP_REQUEST_DATA>: violation detected: flnArgs===#

         

         

         

  • abhinay  please share how you test in postman. 
    I've tried and it works if the POST body is raw type and looks like this : fInArgs=%3D%23
    This is what rules I am using:

    when HTTP_REQUEST { 
    if { ([class match [HTTP::uri] contains example_uri_1]) and ( [HTTP::query] contains "%3D%23") }{
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    log local0. "deny URI: [HTTP::uri] query:[HTTP::query]"
    }
    if {[HTTP::method] eq "POST"}{
    # Trigger collection for up to 1MB of data
    if {[HTTP::header "Content-Length"] ne "" && [HTTP::header "Content-Length"] <= 1048576}{
    set content_length [HTTP::header "Content-Length"]
    } else {
    set content_length 1048576
    }
    # Check if $content_length is not set to 0
    if { $content_length > 0} {
    HTTP::collect $content_length
    }
    }
    }
    when HTTP_REQUEST_DATA {

    if { [HTTP::method] equals "POST" }{
    # Extract the entire HTTP request body and escape it to become a HTTP::uri string (for easier parsings)
    set http_request_body "?[HTTP::payload]"
    log local0. "http payload: $http_request_body"
    # Try to parse type value from the HTTP request body.
    if { [URI::query $http_request_body fInArgs] equals "%3D%23" } {
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    } }
    }

    if you use application/x-www-form-urlencoded you will have to match this "%253D%2523"

    if { [URI::query $http_request_body fInArgs] equals "%253D%2523" } {
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    }

    or use URI::decode :

    if { [URI::decode [URI::query $http_request_body fInArgs]] equals "%3D%23" } {
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    }

     and if it is a form-data:

    set varB [findstr [HTTP::payload] "fInArgs"]
    if { $varB contains "%3D%23" } {
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    }

     

    • abhinay's avatar
      abhinay
      Icon for Nimbostratus rankNimbostratus

      mihaic, small change in URI from "cs.exe" to "/cs". I dont mind having two different iRules for GET and POST.

      Below GET is working abosultely fine

      ltm data-group internal uri_list {
      records {
      /cs { }
      llisapi.dll { }
      }
      type string
      }

      when HTTP_REQUEST {
      if { ([matchclass [string tolower [HTTP::uri]] contains uri_list]) and ( [HTTP::query] contains "%3D%23") }{
      HTTP::respond 403 content "Forbidden" "Content-Type" "text/html"

      }
      }

      For POST, I have verified internally and got the postman and see that the key is "_fInArgs=" and it should contain "=#". I have modified your iRule with these values but still fails.

      The Postman body is below. Please let me know if anything else is needed.

      				"body": {
      					"mode": "urlencoded",
      					"urlencoded": [
      						{
      							"key": "_ApiName",
      							"value": "foo",
      							"type": "default"
      						},
      						{
      							"key": "_fInArgs=",
      							"value": "A<1,?,'_ApiName'='SessionFree','_ConnectionName'=#AAAA>",
      							"type": "default"
      						}
      					]
      				},
  • from what you shared  the the key is "_fInArgs= " and the value is not what you asked for . it is not "%3D%23"

    "key": "_fInArgs=",
    							"value": "A<1,?,'_ApiName'='SessionFree','_ConnectionName'=#AAAA>",

     the format you shared seems to be a JSON 

    try to put something from the value.

    • abhinay's avatar
      abhinay
      Icon for Nimbostratus rankNimbostratus

      mihaic Thats right Sorry for the confusion, an Internal team was testing this earlier. I got the Postman file from them and checked that the key and value were different. 

      I already made changes and tested for body with "_fInArgs=" that contains "=#" which did not work tried "_fInArgs=" that contains "SessionFree" which did not work either. your help will be appreciated.

      when HTTP_REQUEST_DATA {

      if { [HTTP::method] equals "POST" }{
      # Extract the entire HTTP request body and escape it to become a HTTP::uri string (for easier parsings)
      set http_request_body "?[HTTP::payload [HTTP::header value "Content-Length"]]"
      # Try to parse type value from the HTTP request body.
      if { [URI::decode [URI::query $request_body _fInArgs=]] contains "=#" } {
      log local0. "_fInArgs= : $_fInArgs="
      HTTP::respond 403 content "Forbidden" "Content-Type" "text/html"
      }
      }
      }

  • for it works this:

    set token [lindex [ regexp -inline -- {"value": "(.+)"} [HTTP::payload] ] 1]
    if { $token contains "SessionFree" } {
    log local0. "token: $token"
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    } }

     But the problem is that it checkes everything starting teh first "value" it finds till the end.

    I could not yet do a search only for key "_fInArgs=" and match only something in its value.

    As this is a json format, we need a way to parse json.

  • here is a better way.

    set varB [findstr [HTTP::payload] "fInArgs=" 33 type]
    if { $varB contains "SessionFree" } {
    HTTP::respond 403 content "You don't have authorization to view this page. Access Denied" noserver Content-Type text/html Connection Close Cache-Control no-cache
    }

     I've managed to extract the value field.

    This works for me.