android/gatt: Add handling signed write from remote device

diff --git a/android/gatt.c b/android/gatt.c
index 913f479..f2ac482 100644 (file)
--- a/android/gatt.c
+++ b/android/gatt.c
@@ -4768,6 +4768,44 @@ static void write_cmd_request(const uint8_t *cmd, uint16_t cmd_len,
        gatt_db_write(gatt_db, handle, 0, value, vlen, cmd[0], &dev->bdaddr);
 }
 
+static void write_signed_cmd_request(const uint8_t *cmd, uint16_t cmd_len,
+                                               struct gatt_device *dev)
+{
+       uint8_t value[ATT_DEFAULT_LE_MTU];
+       uint8_t s[ATT_SIGNATURE_LEN];
+       uint16_t handle;
+       uint16_t len;
+       size_t vlen;
+       uint8_t csrk[16];
+       uint32_t sign_cnt;
+
+       if (!bt_get_csrk(&dev->bdaddr, REMOTE_CSRK, csrk, &sign_cnt)) {
+               error("gatt: No valid csrk from remote device");
+               return;
+       }
+
+       len = dec_signed_write_cmd(cmd, cmd_len, &handle, value, &vlen, s);
+       if (len) {
+               uint8_t t[ATT_SIGNATURE_LEN];
+
+               /* Generate signature and verify it */
+               if (!bt_crypto_sign_att(crypto, csrk, value, vlen, sign_cnt,
+                                                                       t)) {
+                       error("gatt: Error when generating att signature");
+                       return;
+               }
+
+               if (memcmp(t, s, ATT_SIGNATURE_LEN)) {
+                       error("gatt: signature does not match");
+                       return;
+               }
+               /* Signature OK, proceed with write */
+               bt_update_sign_counter(&dev->bdaddr, REMOTE_CSRK);
+               gatt_db_write(gatt_db, handle, 0, value, vlen, cmd[0],
+                                                               &dev->bdaddr);
+       }
+}
+
 static uint8_t write_req_request(const uint8_t *cmd, uint16_t cmd_len,
                                                struct gatt_device *dev)
 {
@@ -4881,6 +4919,10 @@ static void att_handler(const uint8_t *ipdu, uint16_t len, gpointer user_data)
                write_cmd_request(ipdu, len, dev);
                /* No response on write cmd */
                return;
+       case ATT_OP_SIGNED_WRITE_CMD:
+               write_signed_cmd_request(ipdu, len, dev);
+               /* No response on write signed cmd */
+               return;
        case ATT_OP_PREP_WRITE_REQ:
                status = write_prep_request(ipdu, len, dev);
                if (!status)