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usblib: usb_device_get_string decoding fixes.

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usb_device_get_string converts incoming ucs-2 text
to ascii by truncating the upper byte of each
character.  This is error prone.

This patch introduces usb_device_get_string_ucs2
to access raw USB string descriptors, as well as
changes usb_device_get_string to replace any non
ascii character with '?'.

Bug: 70163357
Change-Id: If8f98fee4be6ea75dc0f7ce7beba7fd7b6aabf88
Test: Connected & disconnected a NuForceDAC.
This commit is contained in:
Andrew Chant 2017-12-07 16:51:49 -08:00
parent 588f5ba383
commit 169742e2db
2 changed files with 82 additions and 22 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
libusbhost/include/usbhost/usbhost.h
View file

@ -140,6 +140,23 @@ uint16_t usb_device_get_product_id(struct usb_device *device);
/* Returns a pointer to device descriptor */
const struct usb_device_descriptor* usb_device_get_device_descriptor(struct usb_device *device);
/* Returns a USB descriptor string for the given string ID.
* Return value: < 0 on error. 0 on success.
* The string is returned in ucs2_out in USB-native UCS-2 encoding.
*
* parameters:
* id - the string descriptor index.
* timeout - in milliseconds (see Documentation/driver-api/usb/usb.rst)
* ucs2_out - Must point to null on call.
* Will be filled in with a buffer on success.
* If this is non-null on return, it must be free()d.
* response_size - size, in bytes, of ucs-2 string in ucs2_out.
* The size isn't guaranteed to include null termination.
* Call free() to free the result when you are done with it.
*/
int usb_device_get_string_ucs2(struct usb_device* device, int id, int timeout, void** ucs2_out,
size_t* response_size);
/* Returns the length in bytes read into the raw descriptors array */
size_t usb_device_get_descriptors_length(const struct usb_device* device);
@ -149,6 +166,7 @@ const unsigned char* usb_device_get_raw_descriptors(const struct usb_device* dev
/* Returns a USB descriptor string for the given string ID.
* Used to implement usb_device_get_manufacturer_name,
* usb_device_get_product_name and usb_device_get_serial.
* Returns ascii - non ascii characters will be replaced with '?'.
* Call free() to free the result when you are done with it.
*/
char* usb_device_get_string(struct usb_device *device, int id, int timeout);

86
libusbhost/usbhost.c
View file

@ -475,17 +475,30 @@ const unsigned char* usb_device_get_raw_descriptors(const struct usb_device* dev
return device->desc;
}
char* usb_device_get_string(struct usb_device *device, int id, int timeout)
{
char string[256];
__u16 buffer[MAX_STRING_DESCRIPTOR_LENGTH / sizeof(__u16)];
/* Returns a USB descriptor string for the given string ID.
* Return value: < 0 on error. 0 on success.
* The string is returned in ucs2_out in USB-native UCS-2 encoding.
*
* parameters:
* id - the string descriptor index.
* timeout - in milliseconds (see Documentation/driver-api/usb/usb.rst)
* ucs2_out - Must point to null on call.
* Will be filled in with a buffer on success.
* If this is non-null on return, it must be free()d.
* response_size - size, in bytes, of ucs-2 string in ucs2_out.
* The size isn't guaranteed to include null termination.
* Call free() to free the result when you are done with it.
*/
int usb_device_get_string_ucs2(struct usb_device* device, int id, int timeout, void** ucs2_out,
size_t* response_size) {
__u16 languages[MAX_STRING_DESCRIPTOR_LENGTH / sizeof(__u16)];
int i, result;
char response[MAX_STRING_DESCRIPTOR_LENGTH];
int result;
int languageCount = 0;
if (id == 0) return NULL;
if (id == 0) return -1;
if (*ucs2_out != NULL) return -1;
string[0] = 0;
memset(languages, 0, sizeof(languages));
// read list of supported languages
@ -496,25 +509,54 @@ char* usb_device_get_string(struct usb_device *device, int id, int timeout)
if (result > 0)
languageCount = (result - 2) / 2;
for (i = 1; i <= languageCount; i++) {
memset(buffer, 0, sizeof(buffer));
for (int i = 1; i <= languageCount; i++) {
memset(response, 0, sizeof(response));
result = usb_device_control_transfer(device,
USB_DIR_IN|USB_TYPE_STANDARD|USB_RECIP_DEVICE, USB_REQ_GET_DESCRIPTOR,
(USB_DT_STRING << 8) | id, languages[i], buffer, sizeof(buffer),
timeout);
if (result > 0) {
int i;
// skip first word, and copy the rest to the string, changing shorts to bytes.
result /= 2;
for (i = 1; i < result; i++)
string[i - 1] = buffer[i];
string[i - 1] = 0;
return strdup(string);
result = usb_device_control_transfer(
device, USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE, USB_REQ_GET_DESCRIPTOR,
(USB_DT_STRING << 8) | id, languages[i], response, sizeof(response), timeout);
if (result >= 2) { // string contents begin at offset 2.
int descriptor_len = result - 2;
char* out = malloc(descriptor_len + 3);
if (out == NULL) {
return -1;
}
memcpy(out, response + 2, descriptor_len);
// trail with three additional NULLs, so that there's guaranteed
// to be a UCS-2 NULL character beyond whatever USB returned.
// The returned string length is still just what USB returned.
memset(out + descriptor_len, '\0', 3);
*ucs2_out = (void*)out;
*response_size = descriptor_len;
return 0;
}
}
return -1;
}
return NULL;
/* Warning: previously this blindly returned the lower 8 bits of
* every UCS-2 character in a USB descriptor. Now it will replace
* values > 127 with ascii '?'.
*/
char* usb_device_get_string(struct usb_device* device, int id, int timeout) {
char* ascii_string = NULL;
size_t raw_string_len = 0;
size_t i;
if (usb_device_get_string_ucs2(device, id, timeout, (void**)&ascii_string, &raw_string_len) < 0)
return NULL;
if (ascii_string == NULL) return NULL;
for (i = 0; i < raw_string_len / 2; ++i) {
// wire format for USB is always little-endian.
char lower = ascii_string[2 * i];
char upper = ascii_string[2 * i + 1];
if (upper || (lower & 0x80)) {
ascii_string[i] = '?';
} else {
ascii_string[i] = lower;
}
}
ascii_string[i] = '\0';
return ascii_string;
}
char* usb_device_get_manufacturer_name(struct usb_device *device, int timeout)