all: add basic USB fuzzing support

This commits implements 4 syzcalls: syz_usb_connect, syz_usb_io_control,
syz_usb_ep_write and syz_usb_disconnect. Those syzcalls are used to emit USB
packets through a custom GadgetFS-like interface (currently exposed at
/sys/kernel/debug/usb-fuzzer), which requires special kernel patches.

USB fuzzing support is quite basic, as it mostly covers only the USB device
enumeration process. Even though the syz_usb_ep_write syzcall does allow to
communicate with USB endpoints after the device has been enumerated, no
coverage is collected from that code yet.

Makefile

@@ -168,6 +168,9 @@ upgrade:
 trace2syz:
 	GOOS=$(HOSTOS) GOARCH=$(HOSTARCH) $(HOSTGO) build $(GOHOSTFLAGS) -o ./bin/syz-trace2syz github.com/google/syzkaller/tools/syz-trace2syz
 
+usbgen:
+	GOOS=$(HOSTOS) GOARCH=$(HOSTARCH) $(HOSTGO) build $(GOHOSTFLAGS) -o ./bin/syz-usbgen github.com/google/syzkaller/tools/syz-usbgen
+
 # `extract` extracts const files from various kernel sources, and may only
 # re-generate parts of files.
 extract: bin/syz-extract

executor/common.h

@@ -41,7 +41,7 @@ NORETURN void doexit(int status)
 
 #if SYZ_EXECUTOR || SYZ_PROCS || SYZ_REPEAT && SYZ_ENABLE_CGROUPS ||         \
     SYZ_ENABLE_NETDEV || __NR_syz_mount_image || __NR_syz_read_part_table || \
-    (GOOS_openbsd || GOOS_freebsd) && SYZ_TUN_ENABLE
+    __NR_syz_usb_connect || (GOOS_openbsd || GOOS_freebsd) && SYZ_TUN_ENABLE
 unsigned long long procid;
 #endif
 
@@ -137,7 +137,8 @@ static void kill_and_wait(int pid, int* status)
 #endif
 
 #if !GOOS_windows
-#if SYZ_EXECUTOR || SYZ_THREADED || SYZ_REPEAT && SYZ_EXECUTOR_USES_FORK_SERVER
+#if SYZ_EXECUTOR || SYZ_THREADED || SYZ_REPEAT && SYZ_EXECUTOR_USES_FORK_SERVER || \
+    __NR_syz_usb_connect
 static void sleep_ms(uint64 ms)
 {
 	usleep(ms * 1000);

executor/common_linux.h

@@ -798,6 +798,21 @@ static long syz_extract_tcp_res(volatile long a0, volatile long a1, volatile lon
 }
 #endif
 
+#if SYZ_EXECUTOR || __NR_syz_usb_connect
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/usb/ch9.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "common_usb.h"
+#endif
+
 #if SYZ_EXECUTOR || __NR_syz_open_dev
 #include <fcntl.h>
 #include <string.h>

executor/common_usb.h

@@ -0,0 +1,452 @@
+// Copyright 2019 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+// This file is shared between executor and csource package.
+
+// Implementation of syz_usb_* pseudo-syscalls.
+
+#define USB_MAX_EP_NUM 32
+
+struct usb_device_index {
+	struct usb_device_descriptor* dev;
+	struct usb_config_descriptor* config;
+	unsigned config_length;
+	struct usb_interface_descriptor* iface;
+	struct usb_endpoint_descriptor* eps[USB_MAX_EP_NUM];
+	unsigned eps_num;
+};
+
+static bool parse_usb_descriptor(char* buffer, size_t length, struct usb_device_index* index)
+{
+	if (length < sizeof(*index->dev) + sizeof(*index->config) + sizeof(*index->iface))
+		return false;
+
+	index->dev = (struct usb_device_descriptor*)buffer;
+	index->config = (struct usb_config_descriptor*)(buffer + sizeof(*index->dev));
+	index->config_length = length - sizeof(*index->dev);
+	index->iface = (struct usb_interface_descriptor*)(buffer + sizeof(*index->dev) + sizeof(*index->config));
+
+	index->eps_num = 0;
+	size_t offset = 0;
+
+	while (true) {
+		if (offset == length)
+			break;
+		if (offset + 1 < length)
+			break;
+		uint8 length = buffer[offset];
+		uint8 type = buffer[offset + 1];
+		if (type == USB_DT_ENDPOINT) {
+			index->eps[index->eps_num] = (struct usb_endpoint_descriptor*)(buffer + offset);
+			index->eps_num++;
+		}
+		if (index->eps_num == USB_MAX_EP_NUM)
+			break;
+		offset += length;
+	}
+
+	return true;
+}
+
+enum usb_fuzzer_event_type {
+	USB_FUZZER_EVENT_INVALID,
+	USB_FUZZER_EVENT_CONNECT,
+	USB_FUZZER_EVENT_DISCONNECT,
+	USB_FUZZER_EVENT_SUSPEND,
+	USB_FUZZER_EVENT_RESUME,
+	USB_FUZZER_EVENT_CONTROL,
+};
+
+struct usb_fuzzer_event {
+	uint32 type;
+	uint32 length;
+	char data[0];
+};
+
+struct usb_fuzzer_init {
+	uint64 speed;
+	const char* driver_name;
+	const char* device_name;
+};
+
+struct usb_fuzzer_ep_io {
+	uint16 ep;
+	uint16 flags;
+	uint32 length;
+	char data[0];
+};
+
+#define USB_FUZZER_IOCTL_INIT _IOW('U', 0, struct usb_fuzzer_init)
+#define USB_FUZZER_IOCTL_RUN _IO('U', 1)
+#define USB_FUZZER_IOCTL_EP0_READ _IOWR('U', 2, struct usb_fuzzer_event)
+#define USB_FUZZER_IOCTL_EP0_WRITE _IOW('U', 3, struct usb_fuzzer_ep_io)
+#define USB_FUZZER_IOCTL_EP_ENABLE _IOW('U', 4, struct usb_endpoint_descriptor)
+#define USB_FUZZER_IOCTL_EP_WRITE _IOW('U', 6, struct usb_fuzzer_ep_io)
+#define USB_FUZZER_IOCTL_CONFIGURE _IO('U', 8)
+#define USB_FUZZER_IOCTL_VBUS_DRAW _IOW('U', 9, uint32)
+
+int usb_fuzzer_open()
+{
+	return open("/sys/kernel/debug/usb-fuzzer", O_RDWR);
+}
+
+int usb_fuzzer_init(int fd, uint32 speed, const char* driver, const char* device)
+{
+	struct usb_fuzzer_init arg;
+	arg.speed = speed;
+	arg.driver_name = driver;
+	arg.device_name = device;
+	return ioctl(fd, USB_FUZZER_IOCTL_INIT, &arg);
+}
+
+int usb_fuzzer_run(int fd)
+{
+	return ioctl(fd, USB_FUZZER_IOCTL_RUN, 0);
+}
+
+int usb_fuzzer_ep0_read(int fd, struct usb_fuzzer_event* event)
+{
+	return ioctl(fd, USB_FUZZER_IOCTL_EP0_READ, event);
+}
+
+int usb_fuzzer_ep0_write(int fd, struct usb_fuzzer_ep_io* io)
+{
+	return ioctl(fd, USB_FUZZER_IOCTL_EP0_WRITE, io);
+}
+
+int usb_fuzzer_ep_write(int fd, struct usb_fuzzer_ep_io* io)
+{
+	return ioctl(fd, USB_FUZZER_IOCTL_EP_WRITE, io);
+}
+
+int usb_fuzzer_ep_enable(int fd, struct usb_endpoint_descriptor* desc)
+{
+	return ioctl(fd, USB_FUZZER_IOCTL_EP_ENABLE, desc);
+}
+
+int usb_fuzzer_configure(int fd)
+{
+	return ioctl(fd, USB_FUZZER_IOCTL_CONFIGURE, 0);
+}
+
+int usb_fuzzer_vbus_draw(int fd, uint32 power)
+{
+	return ioctl(fd, USB_FUZZER_IOCTL_VBUS_DRAW, power);
+}
+
+#define USB_MAX_PACKET_SIZE 1024
+
+struct usb_fuzzer_control_event {
+	struct usb_fuzzer_event inner;
+	struct usb_ctrlrequest ctrl;
+};
+
+struct usb_fuzzer_ep_io_data {
+	struct usb_fuzzer_ep_io inner;
+	char data[USB_MAX_PACKET_SIZE];
+};
+
+struct vusb_connect_string_descriptor {
+	uint32 len;
+	char* str;
+} __attribute__((packed));
+
+struct vusb_connect_descriptors {
+	uint32 qual_len;
+	char* qual;
+	uint32 bos_len;
+	char* bos;
+	uint32 strs_len;
+	struct vusb_connect_string_descriptor strs[0];
+} __attribute__((packed));
+
+static volatile long syz_usb_connect(volatile long a0, volatile long a1, volatile long a2, volatile long a3)
+{
+	int64_t speed = a0;
+	int64_t dev_len = a1;
+	char* dev = (char*)a2;
+	struct vusb_connect_descriptors* conn_descs = (struct vusb_connect_descriptors*)a3;
+
+	debug("syz_usb_connect: dev: %p\n", dev);
+	if (!dev)
+		return -1;
+
+	debug("syz_usb_connect: device data:\n");
+	debug_dump_data(dev, dev_len);
+
+	struct usb_device_index index;
+	memset(&index, 0, sizeof(index));
+	int rv = parse_usb_descriptor(dev, dev_len, &index);
+	if (!rv)
+		return -1;
+	debug("syz_usb_connect: parsed usb descriptor\n");
+
+	int fd = usb_fuzzer_open();
+	if (fd < 0)
+		return -1;
+	debug("syz_usb_connect: usb_fuzzer_open success\n");
+
+	char device[32];
+	sprintf(&device[0], "dummy_udc.%llu", procid);
+	rv = usb_fuzzer_init(fd, speed, "dummy_udc", &device[0]);
+	if (rv < 0)
+		return -1;
+	debug("syz_usb_connect: usb_fuzzer_init success\n");
+
+	rv = usb_fuzzer_run(fd);
+	if (rv < 0)
+		return -1;
+	debug("syz_usb_connect: usb_fuzzer_run success\n");
+
+	bool done = false;
+	while (!done) {
+		char* response_data = NULL;
+		uint32 response_length = 0;
+
+		unsigned ep;
+		uint8 str_idx;
+
+		struct usb_fuzzer_control_event event;
+		event.inner.type = 0;
+		event.inner.length = sizeof(event.ctrl);
+		rv = usb_fuzzer_ep0_read(fd, (struct usb_fuzzer_event*)&event);
+		if (rv < 0)
+			return -1;
+		if (event.inner.type != USB_FUZZER_EVENT_CONTROL)
+			continue;
+
+		debug("syz_usb_connect: bRequestType: 0x%x, bRequest: 0x%x, wValue: 0x%x, wIndex: 0x%x, wLength: %d\n",
+		      event.ctrl.bRequestType, event.ctrl.bRequest, event.ctrl.wValue, event.ctrl.wIndex, event.ctrl.wLength);
+
+		switch (event.ctrl.bRequestType & USB_TYPE_MASK) {
+		case USB_TYPE_STANDARD:
+			switch (event.ctrl.bRequest) {
+			case USB_REQ_GET_DESCRIPTOR:
+				switch (event.ctrl.wValue >> 8) {
+				case USB_DT_DEVICE:
+					response_data = (char*)index.dev;
+					response_length = sizeof(*index.dev);
+					goto reply;
+				case USB_DT_CONFIG:
+					response_data = (char*)index.config;
+					response_length = index.config_length;
+					goto reply;
+				case USB_DT_STRING:
+					str_idx = (uint8)event.ctrl.wValue;
+					if (str_idx >= conn_descs->strs_len)
+						goto reply;
+					response_data = conn_descs->strs[str_idx].str;
+					response_length = conn_descs->strs[str_idx].len;
+					goto reply;
+				case USB_DT_BOS:
+					response_data = conn_descs->bos;
+					response_length = conn_descs->bos_len;
+					goto reply;
+				case USB_DT_DEVICE_QUALIFIER:
+					response_data = conn_descs->qual;
+					response_length = conn_descs->qual_len;
+					goto reply;
+				default:
+					fail("syz_usb_connect: no response");
+					continue;
+				}
+				break;
+			case USB_REQ_SET_CONFIGURATION:
+				rv = usb_fuzzer_vbus_draw(fd, index.config->bMaxPower);
+				if (rv < 0)
+					return -1;
+				rv = usb_fuzzer_configure(fd);
+				if (rv < 0)
+					return -1;
+				for (ep = 0; ep < index.eps_num; ep++) {
+					rv = usb_fuzzer_ep_enable(fd, index.eps[ep]);
+					if (rv < 0)
+						fail("syz_usb_connect: ep enable failed");
+				}
+				done = true;
+				goto reply;
+			default:
+				fail("syz_usb_connect: no response");
+				continue;
+			}
+			break;
+		default:
+			fail("syz_usb_connect: no response");
+			continue;
+		}
+
+		struct usb_fuzzer_ep_io_data response;
+
+	reply:
+		response.inner.ep = 0;
+		response.inner.flags = 0;
+		if (response_length > sizeof(response.data))
+			response_length = 0;
+		response.inner.length = response_length;
+		if (response_data)
+			memcpy(&response.data[0], response_data, response_length);
+		if (event.ctrl.wLength < response.inner.length)
+			response.inner.length = event.ctrl.wLength;
+		debug("syz_usb_connect: reply length = %d\n", response.inner.length);
+		usb_fuzzer_ep0_write(fd, (struct usb_fuzzer_ep_io*)&response);
+	}
+
+	sleep_ms(200);
+
+	debug("syz_usb_connect: configured\n");
+
+	return fd;
+}
+
+#if SYZ_EXECUTOR || __NR_syz_usb_control_io
+struct vusb_descriptor {
+	uint8 req_type;
+	uint8 desc_type;
+	uint32 len;
+	char data[0];
+} __attribute__((packed));
+
+struct vusb_descriptors {
+	uint32 len;
+	struct vusb_descriptor* generic;
+	struct vusb_descriptor* descs[0];
+} __attribute__((packed));
+
+struct vusb_response {
+	uint8 type;
+	uint8 req;
+	uint32 len;
+	char data[0];
+} __attribute__((packed));
+
+struct vusb_responses {
+	uint32 len;
+	struct vusb_response* generic;
+	struct vusb_response* resps[0];
+} __attribute__((packed));
+
+static volatile long syz_usb_control_io(volatile long a0, volatile long a1, volatile long a2)
+{
+	int fd = a0;
+	struct vusb_descriptors* descs = (struct vusb_descriptors*)a1;
+	struct vusb_responses* resps = (struct vusb_responses*)a2;
+
+	struct usb_fuzzer_control_event event;
+	event.inner.type = 0;
+	event.inner.length = sizeof(event.ctrl);
+	int rv = usb_fuzzer_ep0_read(fd, (struct usb_fuzzer_event*)&event);
+	if (rv < 0)
+		return -1;
+	if (event.inner.type != USB_FUZZER_EVENT_CONTROL)
+		return -1;
+
+	debug("syz_usb_control_io: bRequestType: 0x%x, bRequest: 0x%x, wValue: 0x%x, wIndex: 0x%x, wLength: %d\n",
+	      event.ctrl.bRequestType, event.ctrl.bRequest, event.ctrl.wValue, event.ctrl.wIndex, event.ctrl.wLength);
+
+	uint8 req = event.ctrl.bRequest;
+	uint8 req_type = event.ctrl.bRequestType & USB_TYPE_MASK;
+	uint8 desc_type = event.ctrl.wValue >> 8;
+
+	char* response_data = NULL;
+	uint32 response_length = 0;
+
+	if (req == USB_REQ_GET_DESCRIPTOR) {
+		int i;
+		int descs_num = (descs->len - offsetof(struct vusb_descriptors, descs)) / sizeof(descs->descs[0]);
+
+		for (i = 0; i < descs_num; i++) {
+			struct vusb_descriptor* desc = descs->descs[i];
+			if (!desc)
+				continue;
+			if (desc->req_type == req_type && desc->desc_type == desc_type) {
+				response_length = desc->len;
+				if (response_length != 0)
+					response_data = &desc->data[0];
+				goto reply;
+			}
+		}
+
+		if (descs->generic) {
+			response_data = &descs->generic->data[0];
+			response_length = descs->generic->len;
+			goto reply;
+		}
+	} else {
+		int i;
+		int resps_num = (resps->len - offsetof(struct vusb_responses, resps)) / sizeof(resps->resps[0]);
+
+		for (i = 0; i < resps_num; i++) {
+			struct vusb_response* resp = resps->resps[i];
+			if (!resp)
+				continue;
+			if (resp->type == req_type && resp->req == req) {
+				response_length = resp->len;
+				if (response_length != 0)
+					response_data = &resp->data[0];
+				goto reply;
+			}
+		}
+
+		if (resps->generic) {
+			response_data = &resps->generic->data[0];
+			response_length = resps->generic->len;
+			goto reply;
+		}
+	}
+
+	return -1;
+
+	struct usb_fuzzer_ep_io_data response;
+
+reply:
+	response.inner.ep = 0;
+	response.inner.flags = 0;
+	if (response_length > sizeof(response.data))
+		response_length = 0;
+	response.inner.length = response_length;
+	if (response_data)
+		memcpy(&response.data[0], response_data, response_length);
+	if (event.ctrl.wLength < response.inner.length)
+		response.inner.length = event.ctrl.wLength;
+	debug("syz_usb_control_io: reply length = %d\n", response.inner.length);
+	usb_fuzzer_ep0_write(fd, (struct usb_fuzzer_ep_io*)&response);
+
+	sleep_ms(200);
+
+	return 0;
+}
+#endif
+
+#if SYZ_EXECUTOR || __NR_syz_usb_ep_write
+static volatile long syz_usb_ep_write(volatile long a0, volatile long a1, volatile long a2, volatile long a3)
+{
+	int fd = a0;
+	uint16 ep = a1;
+	uint32 len = a2;
+	char* data = (char*)a3;
+
+	struct usb_fuzzer_ep_io_data response;
+	response.inner.ep = ep;
+	response.inner.flags = 0;
+	if (len > sizeof(response.data))
+		len = 0;
+	response.inner.length = len;
+	if (data)
+		memcpy(&response.data[0], data, len);
+
+	return usb_fuzzer_ep_write(fd, (struct usb_fuzzer_ep_io*)&response);
+}
+#endif
+
+#if SYZ_EXECUTOR || __NR_syz_usb_disconnect
+static volatile long syz_usb_disconnect(volatile long a0)
+{
+	int fd = a0;
+
+	int rv = close(fd);
+
+	sleep_ms(200);
+
+	return rv;
+}
+#endif

executor/executor.cc

@@ -572,10 +572,16 @@ retry:
 	}
 
 	int call_index = 0;
+	bool usb_prog = false;
 	for (;;) {
 		uint64 call_num = read_input(&input_pos);
 		if (call_num == instr_eof)
 			break;
+		bool usb_call = false;
+		if (strcmp(syscalls[call_num].name, "syz_usb_connect") == 0) {
+			usb_prog = true;
+			usb_call = true;
+		}
 		if (call_num == instr_copyin) {
 			char* addr = (char*)read_input(&input_pos);
 			uint64 typ = read_input(&input_pos);
@@ -684,7 +690,7 @@ retry:
 		} else if (flag_threaded) {
 			// Wait for call completion.
 			// Note: sys knows about this 25ms timeout when it generates timespec/timeval values.
-			const uint64 timeout_ms = flag_debug ? 1000 : 45;
+			const uint64 timeout_ms = usb_call ? 2000 : (flag_debug ? 1000 : 45);
 			if (event_timedwait(&th->done, timeout_ms))
 				handle_completion(th);
 			// Check if any of previous calls have completed.
@@ -712,6 +718,8 @@ retry:
 		uint64 wait_end = wait_start + wait;
 		if (wait_end < start + 800)
 			wait_end = start + 800;
+		if (usb_prog)
+			wait_end += 2000;
 		while (running > 0 && current_time_ms() <= wait_end) {
 			sleep_ms(1);
 			for (int i = 0; i < kMaxThreads; i++) {
@@ -738,6 +746,11 @@ retry:
 	close_fds();
 #endif
 
+	if (!colliding && !collide && usb_prog) {
+		sleep_ms(500);
+		write_extra_output();
+	}
+
 	if (flag_collide && !flag_inject_fault && !colliding && !collide) {
 		debug("enabling collider\n");
 		collide = colliding = true;

pkg/csource/gen.go

@@ -32,6 +32,7 @@ func main() {
 		"common_test.h",
 		"common_kvm_amd64.h",
 		"common_kvm_arm64.h",
+		"common_usb.h",
 		"kvm.h",
 		"kvm.S.h",
 	} {

pkg/host/host_linux.go

@@ -201,6 +201,9 @@ func isSupportedSyzkall(sandbox string, c *prog.Syscall) (bool, string) {
 	case "syz_emit_ethernet", "syz_extract_tcp_res":
 		reason := checkNetworkInjection()
 		return reason == "", reason
+	case "syz_usb_connect", "syz_usb_disconnect", "syz_usb_control_io", "syz_usb_ep_write":
+		reason := checkUSBInjection()
+		return reason == "", reason
 	case "syz_kvm_setup_cpu":
 		switch c.Name {
 		case "syz_kvm_setup_cpu$x86":
@@ -634,6 +637,13 @@ func checkNetworkInjection() string {
 	return checkNetworkDevices()
 }
 
+func checkUSBInjection() string {
+	if err := osutil.IsAccessible("/sys/kernel/debug/usb-fuzzer"); err != nil {
+		return err.Error()
+	}
+	return ""
+}
+
 func checkNetworkDevices() string {
 	if _, err := exec.LookPath("ip"); err != nil {
 		return "ip command is not found"

sys/linux/init.go

@@ -50,17 +50,18 @@ func InitTarget(target *prog.Target) {
 	target.SanitizeCall = arch.sanitizeCall
 	target.SpecialTypes = map[string]func(g *prog.Gen, typ prog.Type, old prog.Arg) (
 		prog.Arg, []*prog.Call){
-		"timespec":           arch.generateTimespec,
-		"timeval":            arch.generateTimespec,
-		"sockaddr_alg":       arch.generateSockaddrAlg,
-		"alg_name":           arch.generateAlgName,
-		"alg_aead_name":      arch.generateAlgAeadName,
-		"alg_hash_name":      arch.generateAlgHashName,
-		"alg_blkcipher_name": arch.generateAlgBlkcipherhName,
-		"ipt_replace":        arch.generateIptables,
-		"ip6t_replace":       arch.generateIptables,
-		"arpt_replace":       arch.generateArptables,
-		"ebt_replace":        arch.generateEbtables,
+		"timespec":              arch.generateTimespec,
+		"timeval":               arch.generateTimespec,
+		"sockaddr_alg":          arch.generateSockaddrAlg,
+		"alg_name":              arch.generateAlgName,
+		"alg_aead_name":         arch.generateAlgAeadName,
+		"alg_hash_name":         arch.generateAlgHashName,
+		"alg_blkcipher_name":    arch.generateAlgBlkcipherhName,
+		"ipt_replace":           arch.generateIptables,
+		"ip6t_replace":          arch.generateIptables,
+		"arpt_replace":          arch.generateArptables,
+		"ebt_replace":           arch.generateEbtables,
+		"usb_device_descriptor": arch.generateUsbDeviceDescriptor,
 	}
 	// TODO(dvyukov): get rid of this, this must be in descriptions.
 	target.StringDictionary = []string{

sys/linux/init_vusb.go

@@ -0,0 +1,127 @@
+// Copyright 2019 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+package linux
+
+import (
+	"encoding/binary"
+	"fmt"
+	"strings"
+
+	"github.com/google/syzkaller/prog"
+)
+
+const (
+	USB_DEVICE_ID_MATCH_VENDOR = 1 << iota
+	USB_DEVICE_ID_MATCH_PRODUCT
+	USB_DEVICE_ID_MATCH_DEV_LO
+	USB_DEVICE_ID_MATCH_DEV_HI
+	USB_DEVICE_ID_MATCH_DEV_CLASS
+	USB_DEVICE_ID_MATCH_DEV_SUBCLASS
+	USB_DEVICE_ID_MATCH_DEV_PROTOCOL
+	USB_DEVICE_ID_MATCH_INT_CLASS
+	USB_DEVICE_ID_MATCH_INT_SUBCLASS
+	USB_DEVICE_ID_MATCH_INT_PROTOCOL
+	USB_DEVICE_ID_MATCH_INT_NUMBER
+
+	BytesPerUsbID = 17
+)
+
+type UsbDeviceID struct {
+	MatchFlags         uint16
+	IDVendor           uint16
+	IDProduct          uint16
+	BcdDeviceLo        uint16
+	BcdDeviceHi        uint16
+	BDeviceClass       uint8
+	BDeviceSubClass    uint8
+	BDeviceProtocol    uint8
+	BInterfaceClass    uint8
+	BInterfaceSubClass uint8
+	BInterfaceProtocol uint8
+	BInterfaceNumber   uint8
+}
+
+func (arch *arch) generateUsbDeviceDescriptor(g *prog.Gen, typ0 prog.Type, old prog.Arg) (
+	arg prog.Arg, calls []*prog.Call) {
+
+	if old == nil {
+		arg = g.GenerateSpecialArg(typ0, &calls)
+	} else {
+		arg = old
+		calls = g.MutateArg(arg)
+	}
+	if g.Target().ArgContainsAny(arg) {
+		return
+	}
+
+	totalIds := len(usbIds) / BytesPerUsbID
+	idNum := g.Rand().Intn(totalIds)
+	base := usbIds[idNum*BytesPerUsbID : (idNum+1)*BytesPerUsbID]
+
+	p := strings.NewReader(base)
+	var id UsbDeviceID
+	if binary.Read(p, binary.LittleEndian, &id) != nil {
+		panic("not enough data to read")
+	}
+
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_VENDOR) == 0 {
+		id.IDVendor = uint16(g.Rand().Intn(0xffff + 1))
+	}
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_PRODUCT) == 0 {
+		id.IDProduct = uint16(g.Rand().Intn(0xffff + 1))
+	}
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_DEV_LO) == 0 {
+		id.BcdDeviceLo = 0x0
+	}
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_DEV_HI) == 0 {
+		id.BcdDeviceHi = 0xffff
+	}
+	bcdDevice := id.BcdDeviceLo + uint16(g.Rand().Intn(int(id.BcdDeviceHi-id.BcdDeviceLo)+1))
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_DEV_CLASS) == 0 {
+		id.BDeviceClass = uint8(g.Rand().Intn(0xff + 1))
+	}
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_DEV_SUBCLASS) == 0 {
+		id.BDeviceSubClass = uint8(g.Rand().Intn(0xff + 1))
+	}
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_DEV_PROTOCOL) == 0 {
+		id.BDeviceProtocol = uint8(g.Rand().Intn(0xff + 1))
+	}
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_INT_CLASS) == 0 {
+		id.BInterfaceClass = uint8(g.Rand().Intn(0xff + 1))
+	}
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_INT_SUBCLASS) == 0 {
+		id.BInterfaceSubClass = uint8(g.Rand().Intn(0xff + 1))
+	}
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_INT_PROTOCOL) == 0 {
+		id.BInterfaceProtocol = uint8(g.Rand().Intn(0xff + 1))
+	}
+	if (id.MatchFlags & USB_DEVICE_ID_MATCH_INT_NUMBER) == 0 {
+		id.BInterfaceNumber = uint8(g.Rand().Intn(0xff + 1))
+	}
+
+	patchGroupArg(arg, 7, "idVendor", uint64(id.IDVendor))
+	patchGroupArg(arg, 8, "idProduct", uint64(id.IDProduct))
+	patchGroupArg(arg, 9, "bcdDevice", uint64(bcdDevice))
+	patchGroupArg(arg, 3, "bDeviceClass", uint64(id.BDeviceClass))
+	patchGroupArg(arg, 4, "bDeviceSubClass", uint64(id.BDeviceSubClass))
+	patchGroupArg(arg, 5, "bDeviceProtocol", uint64(id.BDeviceProtocol))
+
+	configArg := arg.(*prog.GroupArg).Inner[14].(*prog.GroupArg).Inner[0]
+	interfaceArg := configArg.(*prog.GroupArg).Inner[8].(*prog.GroupArg).Inner[0]
+
+	patchGroupArg(interfaceArg, 5, "bInterfaceClass", uint64(id.BInterfaceClass))
+	patchGroupArg(interfaceArg, 6, "bInterfaceSubClass", uint64(id.BInterfaceSubClass))
+	patchGroupArg(interfaceArg, 7, "bInterfaceProtocol", uint64(id.BInterfaceProtocol))
+	patchGroupArg(interfaceArg, 2, "bInterfaceNumber", uint64(id.BInterfaceNumber))
+
+	return
+}
+
+func patchGroupArg(arg prog.Arg, index int, field string, value uint64) {
+	fieldArg := arg.(*prog.GroupArg).Inner[index].(*prog.ConstArg)
+	if fieldArg.Type().FieldName() != field {
+		panic(fmt.Sprintf("bad field, expected %v, found %v", field, fieldArg.Type().FieldName()))
+	}
+	fieldArg.Val = value
+}