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wasi-http: don't send forbidden headers #136

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pchickey wants to merge 3 commits into from
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wasi-http: don't send forbidden headers #136

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c2fab21
header map translation: do not set FORBIDDEN_HEADERS
pchickey Jul 17, 2026
0b0692c
server: do not add a Content-Length header
pchickey Jul 17, 2026
35872be
lowercase search
pchickey Jul 20, 2026
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23 changes: 19 additions & 4 deletions src/http/fields.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,10 +18,25 @@ pub(crate) fn header_map_from_wasi(wasi_fields: Fields) -> Result<HeaderMap, Err
pub(crate) fn header_map_to_wasi(header_map: &HeaderMap) -> Result<Fields, Error> {
let wasi_fields = Fields::new();
for (key, value) in header_map {
// Unwrap because `HeaderMap` has already validated the headers.
wasi_fields
.append(key.as_str(), value.as_bytes())
.with_context(|| format!("wasi rejected header `{key}: {value:?}`"))?
if !FORBIDDEN_HEADERS.contains(key) {

@avahahn avahahn Jul 20, 2026

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while technically HTTP headers are case sensitive, ones like Content-Length are not usually handled that way.

I recommend normalizing every entry in FORBIDDEN_HEADERS to be lowercase and also to use key.to_ascii_lowercase() here in this contains call as well.

wasi_fields
.append(key.as_str(), value.as_bytes())
.with_context(|| format!("wasi rejected header `{key}: {value:?}`"))?
}
}
Ok(wasi_fields)
}

const FORBIDDEN_HEADERS: [HeaderName; 11] = [
http::header::CONNECTION,
HeaderName::from_static("keep-alive"),
http::header::PROXY_AUTHENTICATE,
http::header::PROXY_AUTHORIZATION,
HeaderName::from_static("proxy-connection"),
http::header::TRANSFER_ENCODING,
http::header::UPGRADE,
http::header::HOST,
HeaderName::from_static("http2-settings"),
http::header::EXPECT,
http::header::CONTENT_LENGTH,
];