extracted challenge-response calculator

app/scripts/comp/app/chal-resp-calculator.js

@@ -0,0 +1,41 @@
+import { Logger } from 'util/logger';
+import { YubiKey } from 'comp/app/yubikey';
+
+const logger = new Logger('chal-resp');
+
+const ChalRespCalculator = {
+    cache: {},
+
+    build(params) {
+        if (!params) {
+            return null;
+        }
+        return challenge => {
+            return new Promise((resolve, reject) => {
+                const ts = logger.ts();
+
+                challenge = Buffer.from(challenge);
+                const hexChallenge = challenge.toString('hex');
+
+                const key = `${params.vid}:${params.pid}:${params.serial}:${hexChallenge}`;
+                if (this.cache[key]) {
+                    logger.debug('Found ChalResp in cache');
+                    return resolve(Buffer.from(this.cache[key], 'hex'));
+                }
+
+                logger.debug('Calculating ChalResp using a YubiKey');
+
+                YubiKey.calculateChalResp(params, challenge, (err, response) => {
+                    if (err) {
+                        return reject(err);
+                    }
+                    this.cache[key] = response.toString('hex');
+                    logger.info('Calculated ChalResp', logger.ts(ts));
+                    resolve(response);
+                });
+            });
+        };
+    }
+};
+
+export { ChalRespCalculator };

app/scripts/models/file-model.js

@@ -8,7 +8,7 @@ import { GroupModel } from 'models/group-model';
 import { IconUrlFormat } from 'util/formatting/icon-url-format';
 import { Logger } from 'util/logger';
 import { mapObject } from 'util/fn';
-import { YubiKey } from 'comp/app/yubikey';
+import { ChalRespCalculator } from 'comp/app/chal-resp-calculator';
 
 const logger = new Logger('file');
 
@@ -23,7 +23,7 @@ class FileModel extends Model {
 
     open(password, fileData, keyFileData, chalResp, callback) {
         try {
-            const challengeResponse = this.makeChallengeResponse(chalResp);
+            const challengeResponse = ChalRespCalculator.build(chalResp);
             const credentials = new kdbxweb.Credentials(password, keyFileData, challengeResponse);
             const ts = logger.ts();
 
@@ -69,26 +69,6 @@ class FileModel extends Model {
         }
     }
 
-    makeChallengeResponse(params) {
-        if (!params) {
-            return null;
-        }
-        return challenge => {
-            return new Promise((resolve, reject) => {
-                logger.debug('Calculating ChalResp using a YubiKey');
-                const ts = logger.ts();
-                challenge = Buffer.from(challenge);
-                YubiKey.calculateChalResp(params, challenge, (err, response) => {
-                    if (err) {
-                        return reject(err);
-                    }
-                    logger.info('Calculated ChalResp', logger.ts(ts));
-                    resolve(response);
-                });
-            });
-        };
-    }
-
     kdfArgsToString(header) {
         if (header.kdfParameters) {
             return header.kdfParameters