[xmlsec] Invalid Signature - possible whitespace handling problem

Aleksey Sanin aleksey at aleksey.com
Thu Nov 20 14:33:43 PST 2003

>in the good one has all white space preserved and intact. That is 
>all tabs and carriage returns are left intact. Exactly as XMLSec 
>returns it. The bad <ds:Signature ...> block has had xml white 
>space handling performed on it after it was returned from XMLSec, by 
>InfoPath :( . That is carriage returns and tabs have been removed and 
>most of the lines are now strung out on 1 line.
I believe Rich already answered you but let me summarize. You have a 
Document signed
by XMLSec. After that you perform *some* changes in the document. And 
verification fails. Digital signatures are used to detect *exactly* that 
situation. And I think
everything happens "as expected".

But since you are asking this question, I guess you think that 
adding/removing tabs or
spaces is not a big deal for XML. However, this is *not* the case. 
Whitespaces are important!
For example, consider these two XML fragments:

       <WelcomeMessage>Hello, user!</WelcomeMessage>

                        Hello, user!

It might have happened that someone *intentionally* left spaces to move 
"Hello, user!' string
N chars from left side. XML has no way of knowing that.


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