gokey allows secret recovery from a seed file without the master password

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.