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schusb's avatar
schusb
Icon for Nimbostratus rankNimbostratus
Aug 28, 2018

What's the purpose of the catch block in an ASM_REQUEST_BLOCKING scenario

We're returning custom ASM-error pages by using an irule whose initial structure follows the principle of the article ASM_REQUEST_BLOCKING.

 

Some month ago i decided to remove the last block 'when HTTP_RESPONSE_RELEASE'. Today i temporarily re-added it and was quite surprised about the log entries. Although the irule works as expected, the content of the catch block is getting executed.

 

How do i identify the typ of the exception thrown by the irule? And what action should it take in this case, since everything works fine?

 

ASM Advanced WAF
asm_request_blocking
catch-block
exception
http_response_release
iRules
security

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  • Kevin_Stewart's avatar
    Kevin_Stewart
    Icon for Employee rankEmployee
    Aug 28, 2018

    You can use the more complete form of catch to return the resulting error:

    if { [catch {
        do only if  previous was event ASM_REQUEST_BLOCKING
        if { $activeViolation } {
            modify respose header
            HTTP::header remove Content-Length
            HTTP::header insert header_1 value_1
        }
    } err] } {
    log local0. "Error is ${err}"
}

    Ref: http://www.tcl.tk/man/tcl8.5/TclCmd/catch.htm