FreeBSD VuXML: Documenting security issues in FreeBSD and the FreeBSD Ports Collection

kio: Information Leak when accessing https when using a malicious PAC file

Affected packages
kdelibs < 4.14.29_10
kf5-kio < 5.31.0_1


VuXML ID f714d8ab-028e-11e7-8042-50e549ebab6c
Discovery 2017-02-28
Entry 2017-03-11

Albert Astals Cid reports:

Using a malicious PAC file, and then using exfiltration methods in the PAC function FindProxyForURL() enables the attacker to expose full https URLs.

This is a security issue since https URLs may contain sensitive information in the URL authentication part (user:password@host), and in the path and the query (e.g. access tokens).

This attack can be carried out remotely (over the LAN) since proxy settings allow "Detect Proxy Configuration Automatically". This setting uses WPAD to retrieve the PAC file, and an attacker who has access to the victim's LAN can interfere with the WPAD protocols (DHCP/DNS+HTTP) and inject his/her own malicious PAC instead of the legitimate one.