From: Amaury Denoyelle <adenoyelle@haproxy.com>
Date: Fri, 30 May 2025 16:00:48 +0000 (+0200)
Subject: MINOR: h3: adjust auth request encoding or fallback to host
X-Git-Tag: v3.3-dev2~44
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=555ec99d437f3c55afeb9056e3ba8affd68fafd6;p=thirdparty%2Fhaproxy.git

MINOR: h3: adjust auth request encoding or fallback to host

Implement proper encoding of HTTP/3 authority pseudo-header during
request transcoding on the backend side. A pseudo-header :authority is
encoded if a value can be extracted from HTX start-line. A special check
is also implemented to ensure that a host header is not encoded if
:authority already is.

A new function qpack_encode_auth() is defined to implement QPACK
encoding of :authority header using literal field line with name ref.
---

diff --git a/include/haproxy/qpack-enc.h b/include/haproxy/qpack-enc.h
index 29136191b..7bc3783a4 100644
--- a/include/haproxy/qpack-enc.h
+++ b/include/haproxy/qpack-enc.h
@@ -11,6 +11,7 @@ int qpack_encode_int_status(struct buffer *out, unsigned int status);
 int qpack_encode_method(struct buffer *out, enum http_meth_t meth, struct ist other);
 int qpack_encode_scheme(struct buffer *out, const struct ist scheme);
 int qpack_encode_path(struct buffer *out, const struct ist path);
+int qpack_encode_auth(struct buffer *out, const struct ist auth);
 int qpack_encode_header(struct buffer *out, const struct ist n, const struct ist v);
 
 #endif /* QPACK_ENC_H_ */
diff --git a/src/h3.c b/src/h3.c
index 41d9250b1..0f642daee 100644
--- a/src/h3.c
+++ b/src/h3.c
@@ -1797,9 +1797,10 @@ static int h3_req_headers_send(struct qcs *qcs, struct htx *htx)
 	if (qpack_encode_path(&headers_buf, uri))
 		goto err;
 
-	/* :authority */
-	if (h3_encode_header(&headers_buf, ist(":authority"), ist("127.0.0.1:20443")))
-		goto err;
+	if (istlen(auth)) {
+		if (qpack_encode_auth(&headers_buf, auth))
+			goto err;
+	}
 
 	/* Encode every parsed headers, stop at empty one. */
 	for (hdr = 0; hdr < sizeof(list) / sizeof(list[0]); ++hdr) {
@@ -1830,6 +1831,10 @@ static int h3_req_headers_send(struct qcs *qcs, struct htx *htx)
 			list[hdr].v = ist("trailers");
 		}
 
+		/* host only encoded if authority is not set */
+		if (istlen(auth) && isteq(list[hdr].n, ist("host")))
+			continue;
+
 		if (h3_encode_header(&headers_buf, list[hdr].n, list[hdr].v))
 			goto err;
 	}
diff --git a/src/qpack-enc.c b/src/qpack-enc.c
index 5f4694979..f6a18397f 100644
--- a/src/qpack-enc.c
+++ b/src/qpack-enc.c
@@ -228,6 +228,25 @@ int qpack_encode_path(struct buffer *out, const struct ist path)
 	}
 }
 
+/* Encode pseudo-header authority defined to <auth> into <out> buffer.
+ *
+ * Returns 0 on success else non-zero.
+ */
+int qpack_encode_auth(struct buffer *out, const struct ist auth)
+{
+	size_t sz;
+
+	sz = 1 + qpack_get_prefix_int_size(istlen(auth), 7) + istlen(auth);
+	if (b_room(out) < sz)
+		return 1;
+
+	qpack_encode_prefix_integer(out, 0, 4, 0x50);
+	qpack_encode_prefix_integer(out, istlen(auth), 7, 0);
+	for (size_t i = 0; i < istlen(auth); ++i)
+		b_putchr(out, istptr(auth)[i]);
+	return 0;
+}
+
 /* Returns 0 on success else non-zero. */
 int qpack_encode_field_section_line(struct buffer *out)
 {