519
Scope Impact Likelihood
Confidentiality Read Application Data
When cryptographic primitives are vulnerable to sidechannel-
attacks, this could be used to reveal unencrypted
plaintext in the worst case.
Potential Mitigations
Phase: Architecture and Design
Strategy = Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be
unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always
be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate
compartmentalization is built into the system design, and the compartmentalization allows for and
reinforces privilege separation functionality. Architects and designers should rely on the principle
of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Phase: Implementation
Ensure that error messages only contain minimal details that are useful to the intended audience
and no one else. The messages need to strike the balance between being too cryptic (which
can confuse users) or being too detailed (which may reveal more than intended). The messages
should not reveal the methods that were used to determine the error. Attackers can use detailed
information to refine or optimize their original attack, thereby increasing their chances of success.
If errors must be captured in some detail, record them in log messages, but consider what
could occur if the log messages can be viewed by attackers. Highly sensitive information such
as passwords should never be saved to log files. Avoid inconsistent messaging that might
accidentally tip off an attacker about internal state, such as whether a user account exists or not.
Demonstrative Examples
Example 1:
The following code checks validity of the supplied username and password and notifies the user of
a successful or failed login.
Example Language: Perl (Bad)
my $username=param('username');
my $password=param('password');
if (IsValidUsername($username) == 1)
{
if (IsValidPassword($username, $password) == 1)
{
print "Login Successful";
}
else
{
print "Login Failed - incorrect password";
}
}
else
{
print "Login Failed - unknown username";
}
In the above code, there are different messages for when an incorrect username is supplied,
versus when the username is correct but the password is wrong. This difference enables a
potential attacker to understand the state of the login function, and could allow an attacker
to discover a valid username by trying different values until the incorrect password message
CWE Version 4.14
CWE-203: Observable Discrepancy
CWE-203: Observable Discrepancy