Date: Tue, 24 May 2016 19:34:29 -0400 (EDT) From: cve-assign@...re.org To: misc@...b.org Cc: cve-assign@...re.org, oss-security@...ts.openwall.com Subject: Re: CVE request: /tmp usage race condition in onionshare -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 > So onionshare use /tmp/onionshare to create a temporary directory > $HS that is then used for the creation of a tor hidden service, as > HiddenServiceDir configuration. Then, the tor daemon create 2 files > in $HS > > But onionshare doesn't verify the owner or the exact permission of > /tmp/onionshare. So if a attacker pre-create a directory > /tmp/onionshare with 777 permissions and him as a owner, he can use > a race condition to inject his own files in the share. > > I suspect that using setgid on /tmp/onionshare might also give > interesting potential attacks. For example, if umask is not properly > set, the attacker could steal the private key and hostname As far as we can tell, there is only one primary problem: the product accepts the existence of a pre-created /tmp/onionshare for which ownership and all permission bits are controlled by the attacker. (Control over the setgid bit isn't really an independent problem with a realistically independent solution.) Use CVE-2016-5026. > I am also not 100% sure that > https://github.com/micahflee/onionshare/blob/master/onionshare/hs.py#L217 > and > https://github.com/micahflee/onionshare/blob/master/onionshare/hs.py#L116 > are safe if a attacker control the directory that will be used for > shutil.rmtree. Nobody has commented on this today, so we are not going to assign a separate CVE ID related to an shutil.rmtree impact unless there is further research by someone. The code has "self.cleanup_filenames.append(self.hidserv_dir)" and the product should have been designed so that self.hidserv_dir is never something controlled by an arbitrary unauthorized local user. Possibly you are envisioning a threat model in which the attacker controls the process running tor but not the process running onionshare. In that situation, it might be important to understand whether there's any symlink following in shutil.rmtree, because this might allow the tor process to trigger unlink actions with the privileges of the onionshare process. - -- CVE Assignment Team M/S M300, 202 Burlington Road, Bedford, MA 01730 USA [ A PGP key is available for encrypted communications at http://cve.mitre.org/cve/request_id.html ] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCAAGBQJXRORnAAoJEHb/MwWLVhi2AjAP/213PqKqOX4HRjUx4vU2Y4gd PUqAk17+LR9BgsIbWJTCl1kcXGSlpHHqsgq/8W3OP+Aumsr6iLy5ksZmw7D9xgyW wYOslFWUA6z9Drt/P24OxiDrHfpqRAxyPclAQJbSgNwmBk9iQK9Tpb+ACLDr3yOU XBcbnBr1QKT2kOFogdB8bx+Qz/uhR9wAJ0f37nJ+iI3Y6pzeKzMDEHl/je9/Pa+X iHjUPuKYHU/A+X+2mN3nBmuXJerijn/MBKjgxW3L4DCNOr5NUC1UQ2WULE9WIds1 DS6CvpaVsZXSA5Q094HFvo0M2AoyfePpQuVuGgPZ3tens//In3pr3xkKPT316HW4 eKNH7I9L6Xc604a64TzFmSQnWui7ZlOwFy/0aR8p2mZCBYEKqMkV1OvFx78EE0pw QpZMRuoz3EcnwNfIhKYpzVzCf1UOKw7srdIfuxnLO6dAPQhMnios26mU7BnxxlLR 4UiZQWeDMZVBqwd+NJnL1NupgAs/4H1mQ+vKIn/obpYnTxGb8q1+x61eyk1Ueh/O JFBj4gfMnO7v/zA0wtlDK/otE9j/XxWHTw9gKH7BAr3wdbJFPoYnng2CMRFjBva3 Kq4j/ml0BclQDxmk4/3PVc19rO56h0EgMKccArJSVANjMrj3YDmKlTcS2YcaJIVa zFC5SNEvmY0EdRR6f2gX =RzaD -----END PGP SIGNATURE-----
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