[PATCH v2 13/13] hw/usb: Add U2F device autoscan to passthru mode

[César Belley]

Signed-off-by: César Belley <cesar.belley@lse.epita.fr>
---
 docs/u2f.txt          |   9 ++++
 hw/usb/meson.build    |   2 +-
 hw/usb/u2f-passthru.c | 113 +++++++++++++++++++++++++++++++++++++-----
 3 files changed, 110 insertions(+), 14 deletions(-)

diff --git a/docs/u2f.txt b/docs/u2f.txt
index f60052882e..8f44994818 100644
--- a/docs/u2f.txt
+++ b/docs/u2f.txt
@@ -42,6 +42,10 @@ on libu2f-emu: configuring and building:
 
     ./configure --enable-u2f && make
 
+The pass-through mode is built by default on Linux. To take advantage
+of the autoscan option it provides, make sure you have a working libudev
+installed on the host.
+
 
 3. Using u2f-emulated
 
@@ -90,6 +94,11 @@ On the host specify the u2f-passthru device with a suitable 
hidraw:
 
     qemu -usb -device u2f-passthru,hidraw=/dev/hidraw0
 
+Alternately, the u2f-passthru device can autoscan to take the first
+U2F device it finds on the host (this requires a working libudev):
+
+    qemu -usb -device u2f-passthru
+
 
 5. Libu2f-emu
 
diff --git a/hw/usb/meson.build b/hw/usb/meson.build
index cac7639924..40c283ceb5 100644
--- a/hw/usb/meson.build
+++ b/hw/usb/meson.build
@@ -52,7 +52,7 @@ endif
 
 # U2F
 softmmu_ss.add(when: 'CONFIG_USB_U2F', if_true: files('u2f.c'))
-softmmu_ss.add(when: ['CONFIG_LINUX', 'CONFIG_USB_U2F'], if_true: 
files('u2f-passthru.c'))
+softmmu_ss.add(when: ['CONFIG_LINUX', 'CONFIG_USB_U2F'], if_true: [libudev, 
files('u2f-passthru.c')])
 softmmu_ss.add(when: ['CONFIG_U2F', 'CONFIG_USB_U2F'], if_true: [u2f, 
files('u2f-emulated.c')])
 
 # usb redirect
diff --git a/hw/usb/u2f-passthru.c b/hw/usb/u2f-passthru.c
index f8771966c7..1311530ee5 100644
--- a/hw/usb/u2f-passthru.c
+++ b/hw/usb/u2f-passthru.c
@@ -378,6 +378,84 @@ static bool u2f_passthru_is_u2f_device(int fd)
                   sizeof(u2f_hid_report_desc_header)) == 0;
 }
 
+#ifdef CONFIG_LIBUDEV
+static int u2f_passthru_open_from_device(struct udev_device *device)
+{
+    const char *devnode = udev_device_get_devnode(device);
+
+    int fd = qemu_open(devnode, O_RDWR);
+    if (fd < 0) {
+        return -1;
+    } else if (!u2f_passthru_is_u2f_device(fd)) {
+        qemu_close(fd);
+        return -1;
+    }
+    return fd;
+}
+
+static int u2f_passthru_open_from_enumerate(struct udev *udev,
+                                            struct udev_enumerate *enumerate)
+{
+    struct udev_list_entry *devices, *entry;
+    int ret, fd;
+
+    ret = udev_enumerate_scan_devices(enumerate);
+    if (ret < 0) {
+        return -1;
+    }
+
+    devices = udev_enumerate_get_list_entry(enumerate);
+    udev_list_entry_foreach(entry, devices) {
+        struct udev_device *device;
+        const char *syspath = udev_list_entry_get_name(entry);
+
+        if (syspath == NULL) {
+            continue;
+        }
+
+        device = udev_device_new_from_syspath(udev, syspath);
+        if (device == NULL) {
+            continue;
+        }
+
+        fd = u2f_passthru_open_from_device(device);
+        udev_device_unref(device);
+        if (fd >= 0) {
+            return fd;
+        }
+    }
+    return -1;
+}
+
+static int u2f_passthru_open_from_scan(void)
+{
+    struct udev *udev;
+    struct udev_enumerate *enumerate;
+    int ret, fd = -1;
+
+    udev = udev_new();
+    if (udev == NULL) {
+        return -1;
+    }
+
+    enumerate = udev_enumerate_new(udev);
+    if (enumerate == NULL) {
+        udev_unref(udev);
+        return -1;
+    }
+
+    ret = udev_enumerate_add_match_subsystem(enumerate, "hidraw");
+    if (ret >= 0) {
+        fd = u2f_passthru_open_from_enumerate(udev, enumerate);
+    }
+
+    udev_enumerate_unref(enumerate);
+    udev_unref(udev);
+
+    return fd;
+}
+#endif
+
 static void u2f_passthru_unrealize(U2FKeyState *base)
 {
     U2FPassthruState *key = PASSTHRU_U2F_KEY(base);
@@ -392,22 +470,31 @@ static void u2f_passthru_realize(U2FKeyState *base, Error 
**errp)
     int fd;
 
     if (key->hidraw == NULL) {
+#ifdef CONFIG_LIBUDEV
+        fd = u2f_passthru_open_from_scan();
+        if (fd < 0) {
+            error_setg(errp, "%s: Failed to find a U2F USB device",
+                       TYPE_U2F_PASSTHRU);
+            return;
+        }
+#else
         error_setg(errp, "%s: Missing hidraw", TYPE_U2F_PASSTHRU);
         return;
-    }
-
-    fd = qemu_open(key->hidraw, O_RDWR);
-    if (fd < 0) {
-        error_setg(errp, "%s: Failed to open %s", TYPE_U2F_PASSTHRU,
-                   key->hidraw);
-        return;
-    }
+#endif
+    } else {
+        fd = qemu_open(key->hidraw, O_RDWR);
+        if (fd < 0) {
+            error_setg(errp, "%s: Failed to open %s", TYPE_U2F_PASSTHRU,
+                       key->hidraw);
+            return;
+        }
 
-    if (!u2f_passthru_is_u2f_device(fd)) {
-        qemu_close(fd);
-        error_setg(errp, "%s: Passed hidraw does not represent "
-                   "a U2F HID device", TYPE_U2F_PASSTHRU);
-        return;
+        if (!u2f_passthru_is_u2f_device(fd)) {
+            qemu_close(fd);
+            error_setg(errp, "%s: Passed hidraw does not represent "
+                       "a U2F HID device", TYPE_U2F_PASSTHRU);
+            return;
+        }
     }
     key->hidraw_fd = fd;
     u2f_passthru_reset(key);
-- 
2.28.0