[PATCH 13/18] usbip: Pass session keys to the kernel

[Maximilian Eschenbacher]

From: Dominik Paulus <dominik.paulus@xxxxxx>

This extends the userspace code to write the generated session keys to
sysfs in hexadecimal encoding after establishing the connection.
The kernel code is modified to parse the session keys.

Signed-off-by: Maximilian Eschenbacher <maximilian@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Fjodor Schelichow <fjodor.schelichow@xxxxxxxxxxx>
Signed-off-by: Johannes Stadlinger <johannes.stadlinger@xxxxxx>
Signed-off-by: Dominik Paulus <dominik.paulus@xxxxxx>
Signed-off-by: Tobias Polzer <tobias.polzer@xxxxxx>
---
 drivers/usb/usbip/stub_dev.c               | 36 +++++++++++++++++++++++++----
 drivers/usb/usbip/usbip_common.h           | 10 ++++++++
 drivers/usb/usbip/vhci_sysfs.c             | 37 ++++++++++++++++++++++++++++--
 tools/usb/usbip/libsrc/usbip_common.c      | 15 ++++++++++++
 tools/usb/usbip/libsrc/usbip_common.h      |  2 ++
 tools/usb/usbip/libsrc/usbip_host_driver.c | 14 ++++++++---
 tools/usb/usbip/libsrc/vhci_driver.c       |  8 ++++---
 7 files changed, 110 insertions(+), 12 deletions(-)

diff --git a/drivers/usb/usbip/stub_dev.c b/drivers/usb/usbip/stub_dev.c
index e6624f1..d237351 100644
--- a/drivers/usb/usbip/stub_dev.c
+++ b/drivers/usb/usbip/stub_dev.c
@@ -57,18 +57,46 @@ static ssize_t store_sockfd(struct device *dev, struct device_attribute *attr,
 			    const char *buf, size_t count)
 {
 	struct stub_device *sdev = dev_get_drvdata(dev);
-	int sockfd = 0;
+	int sockfd = 0, ret;
 	struct socket *socket;
-	int rv;
+	char sendkey[USBIP_KEYSIZE], recvkey[USBIP_KEYSIZE];
+	char sendkey_hex[2 * USBIP_KEYSIZE + 1];
+	char recvkey_hex[2 * USBIP_KEYSIZE + 1];
 
 	if (!sdev) {
 		dev_err(dev, "sdev is null\n");
 		return -ENODEV;
 	}
 
-	rv = sscanf(buf, "%d", &sockfd);
-	if (rv != 1)
+	/*
+	 * Read symmetric crypto keys. They are randomly
+	 * generated by userspace and passed to the kernel
+	 * via sysfs (encoded in hexadecimal)
+	 */
+	if (sscanf(buf, "%d %d %32s %32s", &sockfd, &sdev->ud.use_crypto,
+		   sendkey_hex, recvkey_hex) < 1) {
+		dev_err(dev, "Invalid write to sysfs: Invalid sockfd\n");
 		return -EINVAL;
+	}
+	if (sdev->ud.use_crypto) {
+		int i;
+
+		dev_info(dev, "Using encrypted data transport\n");
+		for (i = USBIP_KEYSIZE - 1; i >= 0; --i) {
+			sendkey_hex[2 * (i + 1)] = 0;
+			ret = sscanf(sendkey_hex + (2 * i), "%2hhX",
+				     &sendkey[i]);
+			if (ret < 1)
+				return -EINVAL;
+		}
+		for (i = USBIP_KEYSIZE - 1; i >= 0; --i) {
+			recvkey_hex[2 * (i + 1)] = 0;
+			ret = sscanf(recvkey_hex + (2 * i), "%2hhX",
+				     &recvkey[i]);
+			if (ret < 1)
+				return -EINVAL;
+		}
+	}
 
 	if (sockfd != -1) {
 		int err;
diff --git a/drivers/usb/usbip/usbip_common.h b/drivers/usb/usbip/usbip_common.h
index 86b0847..69b3f8a 100644
--- a/drivers/usb/usbip/usbip_common.h
+++ b/drivers/usb/usbip/usbip_common.h
@@ -33,6 +33,13 @@
 
 #define USBIP_VERSION "1.0.0"
 
+/*
+ * Length of symmetric keys. Currently, this should be fixed at 16 bytes.
+ * Will break code if changed, look at userspace and stub_dev.c/vhci_sysfs.c
+ * where this constant is used before changing.
+ */
+#define USBIP_KEYSIZE 16
+
 #undef pr_fmt
 
 #ifdef DEBUG
@@ -275,6 +282,9 @@ struct usbip_device {
 		void (*reset)(struct usbip_device *);
 		void (*unusable)(struct usbip_device *);
 	} eh_ops;
+
+	/* Crypto support */
+	int use_crypto;
 };
 
 #define kthread_get_run(threadfn, data, namefmt, ...)			   \
diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index 211f43f..fa948ad 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -174,18 +174,51 @@ static ssize_t store_attach(struct device *dev, struct device_attribute *attr,
 {
 	struct vhci_device *vdev;
 	struct socket *socket;
-	int sockfd = 0;
+	int sockfd = 0, ret;
 	__u32 rhport = 0, devid = 0, speed = 0;
 	int err;
+	unsigned char sendkey[USBIP_KEYSIZE], recvkey[USBIP_KEYSIZE];
+	char sendkey_hex[2*USBIP_KEYSIZE+1], recvkey_hex[2*USBIP_KEYSIZE+1];
+	int use_crypto = 0;
 
 	/*
 	 * @rhport: port number of vhci_hcd
 	 * @sockfd: socket descriptor of an established TCP connection
 	 * @devid: unique device identifier in a remote host
 	 * @speed: usb device speed in a remote host
+	 * @use_crypto: Whether to use an encrypted connection
+	 * @recvkey_hex/@sendkey_hex: Hexadecimal encoded 128bit
+	 *              symmetric encryption keys to be used.
+	 *              Generated randomly for each connection
+	 *              by userspace.
 	 */
-	if (sscanf(buf, "%u %u %u %u", &rhport, &sockfd, &devid, &speed) != 4)
+	sendkey_hex[0] = 0;
+	recvkey_hex[0] = 0;
+	ret = sscanf(buf, "%u %u %u %u %d %32s %32s", &rhport, &sockfd, &devid,
+		     &speed, &use_crypto, sendkey_hex, recvkey_hex);
+	if (ret < 1)
 		return -EINVAL;
+	if (use_crypto && strlen(sendkey_hex) == 32 &&
+			strlen(recvkey_hex) == 32) {
+		int i;
+
+		dev_info(dev, "Using encrypted data transport\n");
+		/* Decode decimal representation */
+		for (i = USBIP_KEYSIZE - 1; i >= 0; --i) {
+			sendkey_hex[2 * (i + 1)] = 0;
+			ret = sscanf(sendkey_hex + (2 * i), "%2hhX",
+				     &sendkey[i]);
+			if (ret < 1)
+				return -EINVAL;
+		}
+		for (i = USBIP_KEYSIZE - 1; i >= 0; --i) {
+			recvkey_hex[2 * (i + 1)] = 0;
+			ret = sscanf(recvkey_hex + (2 * i), "%2hhX",
+				     &recvkey[i]);
+			if (ret < 1)
+				return -EINVAL;
+		}
+	}
 
 	usbip_dbg_vhci_sysfs("rhport(%u) sockfd(%u) devid(%u) speed(%u)\n",
 			     rhport, sockfd, devid, speed);
diff --git a/tools/usb/usbip/libsrc/usbip_common.c b/tools/usb/usbip/libsrc/usbip_common.c
index ac73710..ebca98b 100644
--- a/tools/usb/usbip/libsrc/usbip_common.c
+++ b/tools/usb/usbip/libsrc/usbip_common.c
@@ -283,3 +283,18 @@ void usbip_names_get_class(char *buff, size_t size, uint8_t class,
 
 	snprintf(buff, size, "%s / %s / %s (%02x/%02x/%02x)", c, s, p, class, subclass, protocol);
 }
+
+/*
+ * Converts a 16-byte key to hexadecimal to be pushed to kernelspace
+ *
+ * Output buffer must be at least 33 bytes long
+ */
+char *keytohex(unsigned char *key, char *out)
+{
+	int i;
+
+	out[32] = 0;
+	for (i = 0; i != 16; ++i)
+		sprintf(out + (2 * i), "%02X", key[i]);
+	return out;
+}
diff --git a/tools/usb/usbip/libsrc/usbip_common.h b/tools/usb/usbip/libsrc/usbip_common.h
index 86d21f2..b185c2c 100644
--- a/tools/usb/usbip/libsrc/usbip_common.h
+++ b/tools/usb/usbip/libsrc/usbip_common.h
@@ -156,4 +156,6 @@ void usbip_names_get_product(char *buff, size_t size, uint16_t vendor,
 void usbip_names_get_class(char *buff, size_t size, uint8_t class,
 			   uint8_t subclass, uint8_t protocol);
 
+char *keytohex(unsigned char *key, char *out);
+
 #endif /* __USBIP_COMMON_H */
diff --git a/tools/usb/usbip/libsrc/usbip_host_driver.c b/tools/usb/usbip/libsrc/usbip_host_driver.c
index f7c85da..9ee218e 100644
--- a/tools/usb/usbip/libsrc/usbip_host_driver.c
+++ b/tools/usb/usbip/libsrc/usbip_host_driver.c
@@ -226,7 +226,7 @@ int usbip_host_export_device(struct usbip_exported_device *edev,
 {
 	char attr_name[] = "usbip_sockfd";
 	char sockfd_attr_path[SYSFS_PATH_MAX];
-	char sockfd_buff[30];
+	char sockfd_buff[512];
 	int ret;
 
 	if (edev->status != SDEV_ST_AVAILABLE) {
@@ -244,12 +244,20 @@ int usbip_host_export_device(struct usbip_exported_device *edev,
 		return -1;
 	}
 
+	{
+		char key1[33], key2[33];
+
+		snprintf(sockfd_buff, sizeof(sockfd_buff), "%d %d %s %s\n",
+			 conf->sockfd, conf->use_crypto,
+			 keytohex(conf->key2, key2),
+			 keytohex(conf->key1, key1));
+		dbg("write: %s", sockfd_buff);
+	}
+
 	/* only the first interface is true */
 	snprintf(sockfd_attr_path, sizeof(sockfd_attr_path), "%s/%s",
 		 edev->udev.path, attr_name);
 
-	snprintf(sockfd_buff, sizeof(sockfd_buff), "%d\n", conf->sockfd);
-
 	ret = write_sysfs_attribute(sockfd_attr_path, sockfd_buff,
 				    strlen(sockfd_buff));
 	if (ret < 0) {
diff --git a/tools/usb/usbip/libsrc/vhci_driver.c b/tools/usb/usbip/libsrc/vhci_driver.c
index c0928e2..b34e53a 100644
--- a/tools/usb/usbip/libsrc/vhci_driver.c
+++ b/tools/usb/usbip/libsrc/vhci_driver.c
@@ -300,14 +300,16 @@ int usbip_vhci_get_free_port(void)
 
 int usbip_vhci_attach_device(struct vhci_conf *conf)
 {
-	char buff[200]; /* what size should be ? */
+	char buff[512], key1[33], key2[33];
 	char attach_attr_path[SYSFS_PATH_MAX];
 	char attr_attach[] = "attach";
 	const char *path;
 	int ret;
 
-	snprintf(buff, sizeof(buff), "%u %d %u %u",
-			conf->port, conf->sockfd, conf->devid, conf->speed);
+	snprintf(buff, sizeof(buff), "%u %u %u %u %d %s %s",
+		 conf->port, conf->sockfd, conf->devid, conf->speed,
+		 conf->use_crypto, keytohex(conf->key1, key1),
+		 keytohex(conf->key2, key2));
 	dbg("writing: %s", buff);
 
 	path = udev_device_get_syspath(vhci_driver->hc_device);
-- 
2.1.0

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