user: In gokey versions <0.2.0,
 a flaw in the seed decryption logic resulted in passwords incorrectly 
being derived solely from the initial vector and the AES-GCM 
authentication tag of the key seed.


This issue has been fixed in gokey version 0.2.0. This is a breaking change. The fix has invalidated any passwords/secrets that were derived from the seed file (using the -s option). Even if the input seed file stays the same, version 0.2.0 gokey will generate different secrets.


Impact
This vulnerability impacts generated keys/secrets using a seed file as an entropy input (using the -s option). Keys/secrets generated just from the master password (without the -s
 option) are not impacted. The confidentiality of the seed itself is 
also not impacted (it is not required to regenerate the seed itself). 
Specific impact includes:



  *  keys/secrets generated from a seed file may have lower entropy: it 
was expected that the whole seed would be used to generate keys (240 
bytes of entropy input), where in vulnerable versions only 28 bytes was 
used

  *  a malicious entity could have recovered all passwords, generated 
from a particular seed, having only the seed file in possession without 
the knowledge of the seed master password




Patches
The code logic bug has been fixed in gokey version 0.2.0
 and above. Due to the deterministic nature of gokey, fixed versions 
will produce different passwords/secrets using seed files, as all seed 
entropy will be used now.


System secret rotation guidance
It is advised for users to regenerate passwords/secrets using the patched version of gokey (0.2.0
 and above), and provision/rotate these secrets into respective systems 
in place of the old secret. A specific rotation procedure is 
system-dependent, but most common patterns are described below.


Systems that do not require the old password/secret for rotation
Such systems usually have a "Forgot password" facility or a
 similar facility allowing users to rotate their password/secrets by 
sending a unique "magic" link to the user's email or phone. In such 
cases users are advised to use this facility and input the newly 
generated password secret, when prompted by the system.


Systems that require the old password/secret for rotation
Such systems usually have a modal password rotation window
 usually in the user settings section requiring the user to input the 
old and the new password sometimes with a confirmation. To 
generate/recover the old password in such cases users are advised to:



  *  temporarily download  gokey version 0.1.3 https://github.com/cloudflare/gokey/releases/tag/v0.1.3  for their respective operating system to recover the old password

  *  use gokey version 0.2.0 or above to generate the new password

  *  populate the system provided password rotation form




Systems that allow multiple credentials for the same account to be provisioned
Such systems usually require a secret or a cryptographic 
key as a credential for access, but allow several credentials at the 
same time. One example is SSH: a particular user may have several 
authorized public keys configured on the SSH server for access. For such
 systems users are advised to:



  *  generate a new secret/key/credential using gokey version 0.2.0 or above

  *  provision the new secret/key/credential in addition to the existing credential on the system

  *  verify that the access or required system operation is still possible with the new secret/key/credential

  *  revoke authorization for the existing/old credential from the system




Credit
This vulnerability was found by Théo Cusnir ( @mister_mime https://hackerone.com/mister_mime ) and responsibly disclosed through Cloudflare's bug bounty program.

assistant: CWE-330