Software: OAuth2 Complete For WordPress
Advisory report: https://security.dxw.com/advisories/the-oauth2-complete-plugin-for-wordpress-uses-a-pseudorandom-number-generator-which-is-non-cryptographically-secure/
CVE: Awaiting assignment
CVSS: 10 (High; AV:N/AC:L/Au:N/C:C/I:C/A:C)
The OAuth2 Complete plugin for WordPress uses a pseudorandom number generator which is non-cryptographically secure
The following refer to the generateAccessToken() function in library/OAuth2/ResponseType/AccessToken.php, andthegenerateAuthorizationCode() function in library/OAuth2/ResponseType/AuthorizationCode.php.
These functions attempt to generate secure auth tokens, but do not use the WordPress random number generator. Instead they use a series of fallback calculations depending on which PHP version is being used. Someof these calculationsare not crypographically secure:
The first is mcrypt_create_iv(100, MCRYPT_DEV_URANDOM). MCRYPT_DEV_URANDOM is expected to change to a different random value whenever it is called, but on Windows, on older versions of php it is known to be a constant value
if no other functions (e.g. /dev/urandom) areavailable then the access token is generated solely using mt_rand(), microtime(), and uniqid().
mt_rand() (Mersenne twister) is not a cryptographically secure pseudorandom number generator.
According to the documentation mt_rand() is also biassed towards even return values in some circumstances.
According to the documentation uniqid() is as secure a PRNG as microtime().
Proof of concept
See the documentation:
Upgrade to version 3.1.5 or later.
If this is not possible then ensure that you are using a recent version of php (at least 5.3), ordisable the plugin.
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This vulnerability will be published if we do not receive a response to this report with 14 days.
2015-07-21: Reported to vendor by email
2015-07-21: Requested CVE
2015-08-10: Vendor responded
2015-08-11: Vendor confirmed fixed in version3.1.5
Discovered by dxw:
Please visit security.dxw.com for more information.