关联漏洞
描述
CVE-2022-20009 - Description and sample exploit for Android USB Gadgets
介绍
# android-gadget
## Summary
Certain revisions of the Linux kernel used in Android are affected by issue [CVE-2021-39685](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-39685).
Detailed information and a POC for CVE-2021-39685 may be found in the [inspector-gadget](https://github.com/szymonh/inspector-gadget) repository.
This repository includes POC targeting few Android specific USB gadgets including:
- f_accessory
- f_audio_source
- f_gsi
- f_mtp
- f_qc_rndis
- f_rmnet
## Description
a) f_accessory
- EP0 buffer allocated in composite.c is USB_COMP_EP0_BUFSIZ (4096) bytes large
- function's control tranfser handler acc_ctrlrequest reads ctrl->wLength to w_length
- for bRequest ACCESSORY_SEND_STRING or ACCESSORY_SEND_HID_EVENT value is set to w_length
- data transfer phase length is set to cdev->req->length = value;
- data transfer results in buffer overflow by wLength - 4096 bytes
- amount of data written to and past EP0 buffer is controller by attacker
```
int acc_ctrlrequest(struct usb_composite_dev *cdev,
const struct usb_ctrlrequest *ctrl)
{
struct acc_dev *dev = get_acc_dev();
int value = -EOPNOTSUPP;
struct acc_hid_dev *hid;
int offset;
u8 b_requestType = ctrl->bRequestType;
u8 b_request = ctrl->bRequest;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
unsigned long flags;
...
if (b_requestType == (USB_DIR_OUT | USB_TYPE_VENDOR)) {
...
} else if (b_request == ACCESSORY_SEND_STRING) {
dev_info(&cdev->gadget->dev, "%s: got ACCESSORY_SEND_STRING(52) request\n",
__func__);
schedule_work(&dev->sendstring_work);
dev->string_index = w_index;
cdev->gadget->ep0->driver_data = dev;
cdev->req->complete = acc_complete_set_string;
value = w_length;
...
} else if (b_request == ACCESSORY_SEND_HID_EVENT) {
spin_lock_irqsave(&dev->lock, flags);
hid = acc_hid_get(&dev->hid_list, w_value);
spin_unlock_irqrestore(&dev->lock, flags);
if (!hid) {
value = -EINVAL;
goto err;
}
cdev->req->context = hid;
cdev->req->complete = acc_complete_send_hid_event;
value = w_length;
}
...
if (value >= 0) {
cdev->req->zero = 0;
cdev->req->length = value;
value = usb_ep_queue(cdev->gadget->ep0, cdev->req, GFP_ATOMIC);
if (value < 0)
ERROR(cdev, "%s setup response queue error\n",
__func__);
}
```
b) f_audio_source
- EP0 buffer allocated in composite.c is USB_COMP_EP0_BUFSIZ (4096) bytes large
- function's control tranfser handler audio_setup reads ctrl->wLength to w_length
- for bRequestType matching condition USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_ENDPOINT value variable is assigned to the return value of audio_set_endpoint_req
- audio_set_endpoint_req returns wLength for bRequest equal to UAC_SET_CUR, UAC_SET_MIN, UAC_SET_MAX or UAC_SET_RES
- data transfer phase length is set to value; req->length = value;
- data transfer results in buffer overflow by wLength - 4096 bytes
- amount of data written to and past EP0 buffer is controller by attacker
```
static int
audio_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
struct usb_composite_dev *cdev = f->config->cdev;
struct usb_request *req = cdev->req;
int value = -EOPNOTSUPP;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
/* composite driver infrastructure handles everything; interface
* activation uses set_alt().
*/
switch (ctrl->bRequestType) {
case USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
value = audio_set_endpoint_req(f, ctrl);
break;
case USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_ENDPOINT:
value = audio_get_endpoint_req(f, ctrl);
break;
}
/* respond with data transfer or status phase? */
if (value >= 0) {
pr_debug("audio req%02x.%02x v%04x i%04x l%d\n",
ctrl->bRequestType, ctrl->bRequest,
w_value, w_index, w_length);
req->zero = 0;
req->length = value;
req->complete = audio_control_complete;
value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
if (value < 0)
pr_err("audio response on err %d\n", value);
}
```
```
static int audio_set_endpoint_req(struct usb_function *f,
const struct usb_ctrlrequest *ctrl)
{
int value = -EOPNOTSUPP;
u16 ep = le16_to_cpu(ctrl->wIndex);
u16 len = le16_to_cpu(ctrl->wLength);
u16 w_value = le16_to_cpu(ctrl->wValue);
pr_debug("bRequest 0x%x, w_value 0x%04x, len %d, endpoint %d\n",
ctrl->bRequest, w_value, len, ep);
switch (ctrl->bRequest) {
case UAC_SET_CUR:
case UAC_SET_MIN:
case UAC_SET_MAX:
case UAC_SET_RES:
value = len;
break;
default:
break;
}
return value;
}
```
c) f_gsi
- EP0 buffer allocated in composite.c is USB_COMP_EP0_BUFSIZ (4096) bytes large
- function's control transfer handler gsi_setup reads ctrl->wLength to w_length variable
- for bRequest set to USB_CDC_SEND_ENCAPSULATED_COMMAND value is set to w_length
- data transfer phase length is set to value; req->length = value;
- data transfer results in buffer overflow by wLength - 4096 bytes
- amount of data written to and past EP0 buffer is controller by attacker
```
static int
gsi_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
struct f_gsi *gsi = func_to_gsi(f);
struct usb_composite_dev *cdev = f->config->cdev;
struct usb_request *req = cdev->req;
int id, value = -EOPNOTSUPP;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
struct gsi_ctrl_pkt *cpkt;
u8 *buf;
u32 n;
bool line_state;
...
switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
...
case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
| USB_CDC_SEND_ENCAPSULATED_COMMAND:
log_event_dbg("USB_CDC_SEND_ENCAPSULATED_COMMAND");
if (w_value || w_index != id)
goto invalid;
/* read the request; process it later */
value = w_length;
req->context = gsi;
if (gsi->prot_id == IPA_USB_RNDIS)
req->complete = gsi_rndis_command_complete;
else
req->complete = gsi_ctrl_cmd_complete;
/* later, rndis_response_available() sends a notification */
break;
...
...
/* respond with data transfer or status phase? */
if (value >= 0) {
log_event_dbg("req%02x.%02x v%04x i%04x l%d",
ctrl->bRequestType, ctrl->bRequest,
w_value, w_index, w_length);
req->zero = (value < w_length);
req->length = value;
value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
if (value < 0)
log_event_err("response on err %d", value);
}
```
d) f_mtp
- EP0 buffer allocated in composite.c is USB_COMP_EP0_BUFSIZ (4096) bytes large
- function's control transfer handler mtp_ctrlrequest reads ctrl->wLength to w_length
- for bRequest set to MTP_REQ_CANCEL value is set to w_length
- data transfer phase length is set to value; req->length = value;
- data transfer results in buffer overflow by wLength - 4096 bytes
- amount of data written to and past EP0 buffer is controller by attacker
```
static int mtp_ctrlrequest(struct usb_composite_dev *cdev,
const struct usb_ctrlrequest *ctrl)
{
struct mtp_dev *dev = _mtp_dev;
int value = -EOPNOTSUPP;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
unsigned long flags;
...
} else if ((ctrl->bRequestType & USB_TYPE_MASK) == USB_TYPE_CLASS) {
mtp_log("class request: %d index: %d value: %d length: %d\n",
ctrl->bRequest, w_index, w_value, w_length);
if (ctrl->bRequest == MTP_REQ_CANCEL && w_index == 0
&& w_value == 0) {
mtp_log("MTP_REQ_CANCEL\n");
spin_lock_irqsave(&dev->lock, flags);
if (dev->state == STATE_BUSY) {
dev->state = STATE_CANCELED;
wake_up(&dev->read_wq);
wake_up(&dev->write_wq);
}
spin_unlock_irqrestore(&dev->lock, flags);
/* We need to queue a request to read the remaining
* bytes, but we don't actually need to look at
* the contents.
*/
value = w_length;
...
/* respond with data transfer or status phase? */
if (value >= 0) {
int rc;
cdev->req->zero = value < w_length;
cdev->req->length = value;
rc = usb_ep_queue(cdev->gadget->ep0, cdev->req, GFP_ATOMIC);
if (rc < 0)
pr_err("%s: response queue error\n", __func__);
}
```
e) f_qc_rndis
- EP0 buffer allocated in composite.c is USB_COMP_EP0_BUFSIZ (4096) bytes large
- function's control transfer handler rndis_qc_setup reads ctrl->wLength to w_length
- for bRequest set to USB_CDC_SEND_ENCAPSULATED_COMMAND value is set to w_length
- data transfer phase length is set to value; req->length = value;
- data transfer results in buffer overflow by wLength - 4096 bytes
- amount of data written to and past EP0 buffer is controller by attacker
```
static int
rndis_qc_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
struct f_rndis_qc *rndis = func_to_rndis_qc(f);
struct usb_composite_dev *cdev = f->config->cdev;
struct usb_request *req = cdev->req;
int value = -EOPNOTSUPP;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
...
switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
/* RNDIS uses the CDC command encapsulation mechanism to implement
* an RPC scheme, with much getting/setting of attributes by OID.
*/
case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
| USB_CDC_SEND_ENCAPSULATED_COMMAND:
if (w_value || w_index != rndis->ctrl_id)
goto invalid;
/* read the request; process it later */
value = w_length;
req->complete = rndis_qc_command_complete;
/* later, rndis_response_available() sends a notification */
break;
...
/* respond with data transfer or status phase? */
if (value >= 0) {
DBG(cdev, "rndis req%02x.%02x v%04x i%04x l%d\n",
ctrl->bRequestType, ctrl->bRequest,
w_value, w_index, w_length);
req->context = rndis;
req->zero = (value < w_length);
req->length = value;
value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
if (value < 0)
pr_err("rndis response on err %d\n", value);
}
```
f) f_rmnet
- EP0 buffer allocated in composite.c is USB_COMP_EP0_BUFSIZ (4096) bytes large
- function's control transfer handler frmnet_setup reads ctrl->wLength to w_length
- for bRequest set to USB_CDC_SEND_ENCAPSULATED_COMMAND ret is set to w_length
- data transfer phase length is set to ret; req->length = ret;
- data transfer results in buffer overflow by wLength - 4096 bytes
- amount of data written to and past EP0 buffer is controller by attacker
```
static int
frmnet_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
struct f_rmnet *dev = func_to_rmnet(f);
struct usb_composite_dev *cdev = dev->cdev;
struct usb_request *req = cdev->req;
u16 w_index = le16_to_cpu(ctrl->wIndex);
u16 w_value = le16_to_cpu(ctrl->wValue);
u16 w_length = le16_to_cpu(ctrl->wLength);
int ret = -EOPNOTSUPP;
...
switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
| USB_CDC_SEND_ENCAPSULATED_COMMAND:
pr_debug("%s: USB_CDC_SEND_ENCAPSULATED_COMMAND\n"
, __func__);
ret = w_length;
req->complete = frmnet_cmd_complete;
req->context = dev;
break;
...
/* respond with data transfer or status phase? */
if (ret >= 0) {
VDBG(cdev, "rmnet req%02x.%02x v%04x i%04x l%d\n",
ctrl->bRequestType, ctrl->bRequest,
w_value, w_index, w_length);
req->zero = (ret < w_length);
req->length = ret;
ret = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
if (ret < 0)
ERROR(cdev, "rmnet ep0 enqueue err %d\n", ret);
}
```
## Impact
Devices implementing affected usb device gadget classes (f_accessory, f_audio_source, f_gsi, f_mtp, f_qc_rndis, f_rmnet) may be affected by buffer overflow vulnerabilities resulting in information disclosure, denial of service or execution of arbitrary code in kernel context.
## CVE
[CVE-2022-20009](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-20009)
## Exploit
Issuing control transfer requests with wLength greater than the standard 4096 bytes requires the host to use a custom build of libusb with MAX_CTRL_BUFFER_LENGTH increased to 0xffff. This value can be altered in libusb/os/linux_usbfs.h prior to build.
The gadget.py script requires pyusb. You can install this package via pip as below.
> python3 -m pip install pyusb
Help can be accessed with -h or --help parameters.
```
usage: gadget.py [-h] -v VID -p PID [-l LENGTH] [-d {read,write}] [-f {accessory,audio_source,gsi,qc_rndis,rmnet,mtp}]
Sample exploit for CVE-2022-20009
optional arguments:
-h, --help show this help message and exit
-v VID, --vid VID vendor id
-p PID, --pid PID product id
-l LENGTH, --length LENGTH
lenght of data to write
-d {read,write}, --direction {read,write}
direction of operation from host perspective
-f {accessory,audio_source,gsi,qc_rndis,rmnet,mtp}, --function {accessory,audio_source,gsi,qc_rndis,rmnet,mtp}
```
Example invocations:
```
./gadget.py -v 0x1b67 -p 0x400c -f audio_source
./gadget.py -v 0x18d1 -p 0x4e23 -f mtp
```
## Final notes
Please update your Android to the latest stable version.
文件快照
[4.0K] /data/pocs/5a5cec9f617d4c4247b177c59e490070260120c3
├── [5.3K] gadget.py
├── [ 34K] LICENSE
└── [ 13K] README.md
0 directories, 3 files
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