[PATCH] Bluetooth: l2cap: Check encryption key size on incoming connection

["Frédéric Danis" <frederic.danis@collabora.com>]

This is required for passing GAP/SEC/SEM/BI-04-C PTS test case:
  Security Mode 4 Level 4, Responder - Invalid Encryption Key Size
  - 128 bit

This tests the security key with size from 1 to 15 bytes while the
Security Mode 4 Level 4 requests 16 bytes key size.

Currently PTS fails with the following logs:
- expected:Connection Response:
    Code: [3 (0x03)] Code
    Identifier: (lt)WildCard: Exists(gt)
    Length: [8 (0x0008)]
    Destination CID: (lt)WildCard: Exists(gt)
    Source CID: [64 (0x0040)]
    Result: [3 (0x0003)] Connection refused - Security block
    Status: (lt)WildCard: Exists(gt),
but received:Connection Response:
    Code: [3 (0x03)] Code
    Identifier: [1 (0x01)]
    Length: [8 (0x0008)]
    Destination CID: [64 (0x0040)]
    Source CID: [64 (0x0040)]
    Result: [0 (0x0000)] Connection Successful
    Status: [0 (0x0000)] No further information available

And HCI logs:
< HCI Command: Read Encrypti.. (0x05|0x0008) plen 2
        Handle: 14 Address: 00:1B:DC:F2:24:10 (Vencer Co., Ltd.)
> HCI Event: Command Complete (0x0e) plen 7
      Read Encryption Key Size (0x05|0x0008) ncmd 1
        Status: Success (0x00)
        Handle: 14 Address: 00:1B:DC:F2:24:10 (Vencer Co., Ltd.)
        Key size: 7
> ACL Data RX: Handle 14 flags 0x02 dlen 12
      L2CAP: Connection Request (0x02) ident 1 len 4
        PSM: 4097 (0x1001)
        Source CID: 64
< ACL Data TX: Handle 14 flags 0x00 dlen 16
      L2CAP: Connection Response (0x03) ident 1 len 8
        Destination CID: 64
        Source CID: 64
        Result: Connection successful (0x0000)
        Status: No further information available (0x0000)

Signed-off-by: Frédéric Danis <frederic.danis@collabora.com>
---
 net/bluetooth/l2cap_core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index c7b66b2ea9f2..f2ab09582146 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -3997,6 +3997,13 @@ static void l2cap_connect(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd,
 		goto response;
 	}
 
+	/* Check the encryption key size */
+	if (!l2cap_check_enc_key_size(conn->hcon)) {
+		conn->disc_reason = HCI_ERROR_AUTH_FAILURE;
+		result = L2CAP_CR_SEC_BLOCK;
+		goto response;
+	}
+
 	result = L2CAP_CR_NO_MEM;
 
 	/* Check for valid dynamic CID range (as per Erratum 3253) */
-- 
2.43.0