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04a342cc49
When we are slave role and receives l2cap conn req when encryption has
started, we should check the enc key size to avoid KNOB attack or BLUFFS
attack.
From SIG recommendation, implementations are advised to reject
service-level connections on an encrypted baseband link with key
strengths below 7 octets.
A simple and clear way to achieve this is to place the enc key size
check in hci_cc_read_enc_key_size()
The btmon log below shows the case that lacks enc key size check.
> HCI Event: Connect Request (0x04) plen 10
Address: BB:22:33:44:55:99 (OUI BB-22-33)
Class: 0x480104
Major class: Computer (desktop, notebook, PDA, organizers)
Minor class: Desktop workstation
Capturing (Scanner, Microphone)
Telephony (Cordless telephony, Modem, Headset)
Link type: ACL (0x01)
< HCI Command: Accept Connection Request (0x01|0x0009) plen 7
Address: BB:22:33:44:55:99 (OUI BB-22-33)
Role: Peripheral (0x01)
> HCI Event: Command Status (0x0f) plen 4
Accept Connection Request (0x01|0x0009) ncmd 2
Status: Success (0x00)
> HCI Event: Connect Complete (0x03) plen 11
Status: Success (0x00)
Handle: 1
Address: BB:22:33:44:55:99 (OUI BB-22-33)
Link type: ACL (0x01)
Encryption: Disabled (0x00)
...
> HCI Event: Encryption Change (0x08) plen 4
Status: Success (0x00)
Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
Encryption: Enabled with E0 (0x01)
< HCI Command: Read Encryption Key Size (0x05|0x0008) plen 2
Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
> HCI Event: Command Complete (0x0e) plen 7
Read Encryption Key Size (0x05|0x0008) ncmd 2
Status: Success (0x00)
Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
Key size: 6
// We should check the enc key size
...
> ACL Data RX: Handle 1 flags 0x02 dlen 12
L2CAP: Connection Request (0x02) ident 3 len 4
PSM: 25 (0x0019)
Source CID: 64
< ACL Data TX: Handle 1 flags 0x00 dlen 16
L2CAP: Connection Response (0x03) ident 3 len 8
Destination CID: 64
Source CID: 64
Result: Connection pending (0x0001)
Status: Authorization pending (0x0002)
> HCI Event: Number of Completed Packets (0x13) plen 5
Num handles: 1
Handle: 1 Address: BB:22:33:44:55:99 (OUI BB-22-33)
Count: 1
#35: len 16 (25 Kb/s)
Latency: 5 msec (2-7 msec ~4 msec)
< ACL Data TX: Handle 1 flags 0x00 dlen 16
L2CAP: Connection Response (0x03) ident 3 len 8
Destination CID: 64
Source CID: 64
Result: Connection successful (0x0000)
Status: No further information available (0x0000)
Cc: stable@vger.kernel.org
Signed-off-by: Alex Lu <alex_lu@realsil.com.cn>
Signed-off-by: Max Chou <max.chou@realtek.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.