From 67603162c1d5baaf17f6bf1a3a4c58d5c0524d35 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Thu, 2 Oct 2025 04:52:33 +0200 Subject: [PATCH] DOC: config: clarify some known limitations of the json_query() converter Oula Kivalo reported that different JSON libraries may process duplicate keys differently and that most JSON libraries usually decode the stream before extracting keys, while the current mjson implementation decodes the contents during extraction instead. Let's document this point so that users are aware of the limitations and do not rely on the current behavior and do not use it for what it's not made for (e.g. content sanitization). This is also the case for jwt_header_query(), jwt_payload_query() and jwt_verify(), which already refer to this converter for specificities. --- doc/configuration.txt | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/doc/configuration.txt b/doc/configuration.txt index 64314d789..5addf6c53 100644 --- a/doc/configuration.txt +++ b/doc/configuration.txt @@ -20699,6 +20699,12 @@ json_query([,]) must be a valid JSON Path string as defined in https://datatracker.ietf.org/doc/draft-ietf-jsonpath-base/ + Note: depending on the context and the underlying implementation, extraction + of duplicate JSON keys is undefined and might return the first, last, + or any other occurrence of the same key from the input content, and if + key names are passed encoded, they might not always be matched. In + short, this converter is not suitable for content sanitization. + Example: # get a integer value from the request body # "{"integer":4}" => 5 -- 2.47.3