Date: Wed, 06 Dec 2017 18:21:04 +0100 From: Adam Maris <amaris@...hat.com> To: oss-security@...ts.openwall.com Subject: Re: Info Leak in the Linux Kernel via Bluetooth On Wed, 2017-12-06 at 16:23 +0000, Armis Security wrote: > Hello, > > We are writing to disclose an information leak vulnerability in the > Bluetooth stack of the Linux Kernel (BlueZ). > This vulnerability has been disclosed to the Kernel's security team ( > security@...nel.org), and a patch for it is in stages of review. > This patch is also attached here. > > This vulnerability lies in the processing of incoming L2CAP commands > - ConfigRequest, and ConfigResponse messages. > This info leak is a result of uninitialized stack variables that may > be returned to an attacker in their uninitialized state. > By manipulating the code flows that precede the handling of these > configuration messages, an attacker can also gain some control over > which data will be held in the uninitialized stack variables. > This can allow him to bypass KASLR, and stack canaries protection - > as both pointers and stack canaries may be leaked in this manner. > > Combining this vulnerability (for example) with the previously > disclosed RCE vulnerability in L2CAP configuration parsing (CVE-2017- > 1000251) may allow an attacker to exploit the RCE against kernels > which were built with the above mitigations. > > These are the specifics of this vulnerability: > In the function l2cap_parse_conf_rsp and in the function > l2cap_parse_conf_req the following variable is declared without > initialization: > > struct l2cap_conf_efs efs; > > In addition, when parsing input configuration parameters in both of > these functions, the switch case for handling EFS elements may skip > the memcpy call that will write to the efs variable: > > ... > case L2CAP_CONF_EFS: > if (olen == sizeof(efs)) > memcpy(&efs, (void *)val, olen); > ... > > The olen in the above if is attacker controlled, and regardless of > that if, in both of these functions the efs variable would eventually > be added to the outgoing configuration request that is being built: > > l2cap_add_conf_opt(&ptr, L2CAP_CONF_EFS, sizeof(efs), (unsigned long) > &efs); > > So by sending a configuration request, or response, that contains an > L2CAP_CONF_EFS element, but with an element length that is not > sizeof(efs) - the memcpy to the uninitialized efs variable can be > avoided, > and the uninitialized variable would be returned to the attacker (16 > bytes). > For reference, this issue was assigned CVE-2017-1000410. Regards, -- Adam Mariš, Red Hat Product Security 1CCD 3446 0529 81E3 86AF 2D4C 4869 76E7 BEF0 6BC2
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.