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HTTP Headers line folding seems to break Hackvertor tags

Antoine | Last updated: Aug 09, 2021 06:53AM UTC

Hello, I was playing with line folding in HTTP headers after reading the as-usual-amazing paper from albinowax (https://portswigger.net/research/http2), and I noticed something strange with Hackvertor tags when testing with HTTP TRACE requests. If I put a "folded" line (a line starting with a space), the Hackvertor tags are not interpreted (even if they are in another line). With the following request, everything will work normally: TRACE / HTTP/2 Host: foo.com User-Agent: foobar X: Y A: B<@repeat(10)>D<@/repeat> W: Z If will see: HTTP/2 200 Ok [... other headers... then the TRACE request reflected back] TRACE / HTTP/2 Host: foo.com User-Agent: foobar X: Y a: BDDDDDDDDDD W: Z If I use a "folded" line in the TRACE request, I'll have something different: TRACE / HTTP/2 User-Agent: FOOBAR x: b A: BBB<@repeat(10)>D<@/repeat> W: Z HTTP/2 200 OK [... other headers... then the TRACE request reflected back] user-agent: FOOBAR x: b a: BBB<@repeat(10)>D<@/repeat> Note that this is the case with HTTP/1.1 and HTTP/2.

Uthman, PortSwigger Agent | Last updated: Aug 09, 2021 02:33PM UTC