EVevanelias·Mar 6, 2022
> mysql_real_escape_string is still vulnerable when being used with some exotic character sets
Indeed -- mysql_real_escape_string "mostly" fixes this problem by requiring a db connection as one of its args. Since the driver is usually aware of the connection state, mysql_real_escape_string can check to see if one of those exotic charsets is in-use. The issue is that there are multiple ways to change the connection charset, some of which the driver is aware of (e.g. in PHP mysqli set_charset) but some it is not (running textual statements like SET NAMES or SET CHARACTER SET).
However, generally an attacker won't have the ability to set an arbitrary exotic character set for the connection anyway... unless they already have some other sql injection mechanism, in which case it's a moot point :)
Driver documentation also typically mentions thi
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s problem. For example, here's the doc for doing client-side param interpolation in the most popular MySQL driver for Golang: https://github.com/go-sql-driver/mysql#interpolateparams (see warning in italics)
It also explicitly detects if your initial connection settings attempt to use one of those charsets along with param interpolation, and throws an error if so: https://github.com/go-sql-driver/mysql/blob/21f789cd/dsn.go#...
> Couldn't one just save the extra round-trip with length-prefixed strings by sending the query together with the parameters in a single message?
AFAIK, no, not with the traditional MySQL binary protocol. The newer "X protocol" introduced in MySQL 5.7 does allow this, but it is not widely implemented in drivers.