[PATCH 1/2] gweb: Normalize received HTTP header field names to lowercase

[Giuseppe Eletto <giuseppe.eletto98@gmail.com>]

Modern HTTP servers, including HTTP/2 and HTTP/3 backends acting
as proxies, commonly send header field names in lowercase. While
RFC 9110 Section 5.1 defines field names as case-insensitive,
connman was performing case-sensitive hash table lookups against
fixed mixed-case strings, causing lookups to silently fail when
the server used lowercase names.

Normalize incoming response header field names to lowercase at
parse time so that lookups succeed regardless of the case used
by the server.

- add_header_field: use g_ascii_strdown() instead of g_strdup()
  to normalize the key before inserting it into the hash table
- received_data_continue: look up "transfer-encoding" in lowercase
  to match the normalized store
- g_web_result_get_header: scan the caller-supplied name for
  uppercase characters and normalize with g_ascii_strdown() only
  when needed

Outgoing request headers are left in mixed case. HTTP/1.1
requires that servers recognize header field names regardless
of case, so no change is needed on the sending side.

Signed-off-by: Giuseppe Eletto <giuseppe.eletto98@gmail.com>
---
 gweb/gweb.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/gweb/gweb.c b/gweb/gweb.c
index 0a87da64..26d18544 100644
--- a/gweb/gweb.c
+++ b/gweb/gweb.c
@@ -1201,7 +1201,7 @@ static void add_header_field(struct web_session *session)
 		*pos = '\0';
 		pos++;
 
-		key = g_strdup(str);
+		key = g_ascii_strdown(str, -1);
 
 		/* remove preceding white spaces */
 		while (*pos == ' ')
@@ -1390,7 +1390,7 @@ static bool received_data_continue(struct web_session *session,
 			session->header_done = true;
 
 			val = g_hash_table_lookup(session->result.headers,
-							"Transfer-Encoding");
+							"transfer-encoding");
 			if (val) {
 				val = g_strrstr(val, "chunked");
 				if (val) {
@@ -2789,13 +2789,26 @@ bool g_web_result_get_chunk(GWebResult *result,
 bool g_web_result_get_header(GWebResult *result,
 				const char *header, const char **value)
 {
+	const char *p;
+	gchar *lower = NULL;
+
 	if (!result)
 		return false;
 
 	if (!value)
 		return false;
 
-	*value = g_hash_table_lookup(result->headers, header);
+	p = header;
+	while (*p && !g_ascii_isupper(*p))
+		p++;
+
+	if (!*p) {
+		*value = g_hash_table_lookup(result->headers, header);
+	} else {
+		lower = g_ascii_strdown(header, -1);
+		*value = g_hash_table_lookup(result->headers, lower);
+		g_free(lower);
+	}
 
 	if (!*value)
 		return false;
-- 
2.50.1