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The Android-specific chmod and chown operations on the client socket (for communication with wpa_supplicant) did not protect against file replacement between the bind() and chmod()/chown() calls. If the directory in which the client socket is created (depends a bit on the version and platform, but /data/misc/wifi/sockets is commonly used) allows write access to processes that are different (less privileged) compared to the process calling wpa_ctrl_open2(), it might be possible to delete the socket file and replace it with something else (mainly, a symlink) before the chmod/chown operations occur. This could have resulted in the owner or permissions of the target of that symlink being modified. In general, it would be safest to use a directory which has more limited write privileges (/data/misc/wifi/sockets normally has 'wifi' group (AID_WIFI) with write access), but if that cannot be easily changed due to other constraints, it is better to make wpa_ctrl_open2() less likely to enable this type of race condition between the operations. Replace chown() with lchown() (i.e., a version that does not dereference symlinks) and chmod() with fchmod() on the socket before the bind() call which is also not going to dereference a symlink (whereas chmod() would). lchown() is a standard operation, but the fchmod() on the socket is less so (unspecified behavior in some systems). However, it seems to work on Linux and in particular, on Android, where this code is executed. Signed-off-by: Jouni Malinen <j@w1.fi>
wpa_supplicant and hostapd -------------------------- Copyright (c) 2002-2019, Jouni Malinen <j@w1.fi> and contributors All Rights Reserved. These programs are licensed under the BSD license (the one with advertisement clause removed). If you are submitting changes to the project, please see CONTRIBUTIONS file for more instructions. This package may include either wpa_supplicant, hostapd, or both. See README file respective subdirectories (wpa_supplicant/README or hostapd/README) for more details. Source code files were moved around in v0.6.x releases and compared to earlier releases, the programs are now built by first going to a subdirectory (wpa_supplicant or hostapd) and creating build configuration (.config) and running 'make' there (for Linux/BSD/cygwin builds). License ------- This software may be distributed, used, and modified under the terms of BSD license: Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. 3. Neither the name(s) of the above-listed copyright holder(s) nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.