File an advisory for async-h1 < 2.3.0

crates/async-h1/RUSTSEC-0000-0000.md

@@ -0,0 +1,35 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "async-h1"
+date = "2020-12-17"
+url = "https://github.com/http-rs/async-h1"
+categories = ["request-smuggling"]
+keywords = ["request", "smuggling"]
+aliases = ["GHSA-4vr9-8cjf-vf9c"]
+#cvss = "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H"
+
+[versions]
+patched = [">= 2.3.0"]
+unaffected = []
+
+[affected]
+#arch = ["x86"]
+#os = ["windows"]
+functions = {
+  "async_h1::server::decode" = ["< 2.3.0"],
+  "async_h1::server::accept" = ["< 2.3.0"]
+}
+```
+
+# Async-h1 request smuggling possible with long unread bodies
+
+This vulnerability affects any webserver that uses async-h1 behind a reverse proxy, including all such Tide applications.
+
+If the server does not read the body of a request which is longer than some buffer length, async-h1 will attempt to read a subsequent request from the body content starting at that offset into the body.
+
+One way to exploit this vulnerability would be for an adversary to craft a request such that the body contains a request that would not be noticed by a reverse proxy, allowing it to forge forwarded/x-forwarded headers. If an application trusted the authenticity of these headers, it could be misled by the smuggled request.
+
+Another potential concern with this vulnerability is that if a reverse proxy is sending multiple http clients' requests along the same keep-alive connection, it would be possible for the smuggled request to specify a long content and capture another user's request in its body. This content could be captured in a post request to an endpoint that allows the content to be subsequently retrieved by the adversary.
+
+The flaw was corrected in commit [7df79f](https://github.com/http-rs/async-h1/commit/7df79f1d5d99fc0f492b315eebc7f0d301a85212) by ensuring that the request body is always consumed from the tcp stream before attempting to read subsequent keep-alive request headers from it.