Date: Mon, 2 May 2016 23:30:45 +0300 From: Jouni Malinen <j@...fi> To: oss-security@...ts.openwall.com Subject: hostapd/wpa_supplicant - psk configuration parameter update allowing arbitrary data to be written psk configuration parameter update allowing arbitrary data to be written Published: May 2, 2016 Identifier: related to CVE-2016-2447 Latest version available from: http://w1.fi/security/2016-1/ Vulnerability A vulnerability was found in how hostapd and wpa_supplicant writes the configuration file update for the WPA/WPA2 passphrase parameter. If this parameter has been updated to include control characters either through a WPS operation or through local configuration change over the wpa_supplicant control interface, the resulting configuration file may prevent the hostapd and wpa_supplicant from starting when the updated file is used. In addition for wpa_supplicant, it may be possible to load a local library file and execute code from there with the same privileges under which the wpa_supplicant process runs. The WPS trigger for this requires local user action to authorize the WPS operation in which a new configuration would be received. The attacker would also need to be in radio range of the device or have access to the IP network to act as a WPS External Registrar. Such an attack could result in denial of service by not allowing hostapd or wpa_supplicant to start after they have been stopped. The local configuration update through the control interface SET_NETWORK command could allow privilege escalation for the local user to run code from a locally stored library file under the same privileges as the wpa_supplicant process has. The assumption here is that a not fully trusted user/application might have access through a connection manager to set network profile parameters like psk, but would not have access to set other configuration file parameters. If the connection manager in such a case does not filter out control characters from the psk value, it could have been possible to practically update the global parameters by embedding a newline character within the psk value. In addition, the untrusted user/application would need to be able to install a library file somewhere on the device from where the wpa_supplicant process has privileges to load the library. Similarly to the SET_NETWORK case, if a connection manager exposes access to the SET_CRED or SET commands, similar issue with newline characters can exist as those commands do not filter out control characters from the value. It should also be noted that providing unlimited access to the wpa_supplicant control interface would allow arbitrary SET commands to be issued. Such unlimited access should not be provided to untrusted users/applications. Vulnerable versions/configurations For the local control interface attack vector: wpa_supplicant v0.4.0-v2.5 with control interface enabled update_config=1 must have been enabled in the configuration file. For the WPS attack vector: wpa_supplicant v0.6.7-v2.5 with CONFIG_WPS build option enabled hostapd v0.6.7-v2.5 with CONFIG_WPS build option enabled WPS needs to be enabled in the runtime operation and the WPS operation needs to have been authorized by the local user over the control interface. For wpa_supplicant, update_config=1 must have been enabled in the configuration file. Acknowledgments Thanks to Google for reporting this issue and Imre Rad of SEARCH-LAB Ltd. discovering it. Possible mitigation steps - Merge the following commits to hostapd/wpa_supplicant and rebuild it: WPS: Reject a Credential with invalid passphrase Reject psk parameter set with invalid passphrase character Remove newlines from wpa_supplicant config network output Reject SET_CRED commands with newline characters in the string values Reject SET commands with newline characters in the string values These patches are available from http://w1.fi/security/2016-1/ - Update to wpa_supplicant v2.6 or newer, once available -- Jouni Malinen PGP id EFC895FA
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