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ruma rejects Authorization: X-Matrix ... headers that include optional whitespace around parameter pairs #1801

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anoadragon453 opened this issue May 8, 2024 · 1 comment · May be fixed by #1805
Open

ruma rejects Authorization: X-Matrix ... headers that include optional whitespace around parameter pairs #1801

anoadragon453 opened this issue May 8, 2024 · 1 comment · May be fixed by #1805
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area/server-util effort/medium type/bug

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@anoadragon453
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The spec states that the format of the Authorization header on the Federation API is given by RFC 7235. Part of that specification allows for zero or more spaces or tabs around the commas in the parameter list. For example, the following should be a valid Authorization header:

Authorization: X-Matrix origin=foo , key="ed25519:1",  sig="sig",		destination="bar"

Yet upon looking at ruma's source code, I believe it would reject this header:

Pair names or values are not trimmed for whitespace:

ruma/crates/ruma-server-util/src/authorization.rs

Lines 110 to 125 in b4d0ab4

fn parse_xmatrix_field<'a>(tokens: &mut impl Tokens<Item = &'a u8>) -> Option<(String, Vec<u8>)> {
tokens.optional(|t| {
let name = parse_token(t).and_then(|name| {
let name = std::str::from_utf8(&name).ok()?.to_ascii_lowercase();
match name.as_str() {
"origin" | "destination" | "key" | "sig" => Some(name),
name => {
debug!(
"Encountered an invalid field name {} at location {}",
name,
t.location().offset()
);
None
}
}
})?;

And space or tab is not allowed in the name field:

ruma/crates/ruma-server-util/src/authorization.rs

Lines 192 to 196 in b4d0ab4

fn is_tchar(c: u8) -> bool {
const TOKEN_CHARS: [u8; 15] =
[b'!', b'#', b'$', b'%', b'&', b'\'', b'*', b'+', b'-', b'.', b'^', b'_', b'`', b'|', b'~'];
is_alpha(c) || is_digit(c) || TOKEN_CHARS.contains(&c)
}

This fact was omitted from the summary of RFC 7235 in the spec, which is likely why it didn't make it into ruma as well. That is now being corrected: matrix-org/matrix-spec#1818

The code should be updated to allow whitespace in the parameter list in the header, such that any homeserver implementations following the spec would not have their federation requests rejected by homeservers that rely on ruma.

See matrix-org/matrix-spec#1817 for more context.
@zecakeh
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zecakeh commented May 8, 2024 •
edited

I am wondering if we should just use the http-auth crate instead of reimplementing a parser ourselves. It has a parser for RFC 7235 and all the features we don't need are behind cargo features.

@zecakeh zecakeh linked a pull request May 9, 2024 that will close this issue
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@zecakeh zecakeh mentioned this issue Jun 7, 2024
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server-util: Use http-auth crate to parse XMatrix ruma/ruma
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@anoadragon453 @zecakeh