Auditing WriteDiary.com

October 27, 2017
android cve

WriteDiary consists of a webapp and an Android app (version 4.72). For the audit, the android app was the primary target.

The developer and owner of both the webapp and android app has been contacted multiple times to develop a quick fix for the issues addressed in this blog post and a vulnerability concerning the webapp which isn’t described here. However, no response has been received. This is bad, as you will see in the first finding:

Embedded Management Credentails

Yes, really. The developer decided to embed his personal GMail credential in the Android app. These credentials may or may not work in the management interface of this product - of course I haven’t tried ;)

CVE-2017-15581: Lack of HTTPS-usage, lack of user data encryption when transmitting

In the “Diary with lock” (aka WriteDiary) application 4.72 for Android, neither HTTPS nor other encryption is used for transmitting data, despite the website states that the product is intended for “a personal journal of secrets and feelings,” which allows remote attackers to obtain sensitive information by sniffing the network during LoginActivity or NoteActivity execution. You can simply check the file strings.xml for api_url_prod with the value of http://diary.adpog.com/api2.

Password transmission in plain text

Plaintet body

Summary

The CVE details can be found here

Vulnerability Type Plaintext data transport
Affected Product Code Base WriteDiary - 4.72
Affected Component LoginActivity, NoteActivity
Impact Information disclosure of sensitive user data

CVE-2017-15582: Usage of static AES parameters

In net.MCrypt in the “Diary with lock” (aka WriteDiary) application 4.72 for Android, hardcoded SecretKey and iv variables are used for the AES parameters, which makes it easier for attackers to obtain the cleartext of stored diary entries:

Static AES parameters

As you can see, the specific values are:

secret key = "f8djD2kfdU31wuRu"
iv = "aBcNvn71dkdjf8hf"

Summary

The CVE details can be found here

Vulnerability Type Hard coded AES parameters
Affected Product Code Base WriteDiary - 4.72
Affected Component net.MCrypt
Impact Information disclosure of sensitive user data

Additional note

Further analysis showed that the data stored on the web application server is not encrypted. This means, that the whole concept isn’t as private as it claims it is. On top of that, there’s a built-in backdoor which lets the administrator access the confidential diary entries of every user.

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