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Vadym_Chepkov's avatar
Vadym_Chepkov
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Mar 05, 2021

How to preserve HTTP headers for HTTP::respond

I need to preserve HTTP headers for HTTP::respond, I tried the following approach when HTTP_RESPONSE { if {[HTTP::has_responded]} {return} catch { unset hdrs } foreach header [HTTP::header ...
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Vadym_Chepkov's avatar
Vadym_Chepkov
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Thank you,  , it helped. Is it enough to put $hdrs in curly braces to avoid TCL injection ?

Or maybe append HTTP::respond statement with an additional header? Article doesn't provide detailed recommendation how to protect from malicious input.

Also, I solved the problems of quoting by converting $hdrs to a list, i.e.

    set headers {}
 
    foreach header [HTTP::header names] {
        lappend headers $header [HTTP::header value $header]
    }

Thanks,

Vadym

Simon_Blakely's avatar
Simon_Blakely
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Mar 08, 2021

>Is it enough to put $hdrs in curly braces to avoid TCL injection ?

No - that just makes {$hrds} a single parameter with spaces in it.

I suspect you need to individually wrap each element (the headers and the values) in curly braces prior to the eval

So you end up doing an eval on

HTTP::respond 301 -version auto {header1} {header1_value} {header2} {header2_value} ...

That prevents eval from further expanding the strings in the curly braces.

But I don't really get TCL injection either - I know it is possible via unsanitized input, and eval is a common problem, and curly braces help, but I still struggle with it.