Overview
The use of password systems as the primary means of
authentication may be subject to several flaws or
shortcomings, each reducing the effectiveness of the
mechanism.
Consequences
- Authentication: The failure of a password
authentication mechanism will almost always result in
attackers being authorized as valid users.
Exposure
period
- Design: The period of development in which
authentication mechanisms and their protections are
devised is the design phase.
Platform
Required
resources
Any
Severity
High
Likelihood
of
exploit
Very High
Avoidance
and
mitigation
- Design: Use a zero-knowledge password protocol, such
as SRP.
- Design: Ensure that passwords are sorted safely and
are not reversible.
- Design: Implement password aging functionality that
requires passwords be changed after a certain point.
- Design: Use a mechanism for determining the strength
of a password and notify the user of weak password use.
- Design: Inform the user of why password protections
are in place, how they work to protect data integrity,
and why it is important to heed their warnings.
Discussion
Password systems are the simplest and most ubiquitous
authentication mechanisms. However, they are subject to such
well known attacks, and such frequent compromise that their
use in the most simple implementation is not practical. In
order to protect password systems from compromise, the
following should be noted:
- Passwords should be stored safely to prevent insider
attack and to ensure that - if a system is compromised -
the passwords are not retrievable. Due to password
reuse, this information may be useful in the compromise
of other systems these users work with. In order to
protect these passwords, they should be stored
encrypted, in a non-reversible state, such that the
original text password cannot be extracted from the
stored value.
- Password aging should be strictly enforced to ensure
that passwords do not remain unchanged for long periods
of time. The longer a password remains in use, the
higher the probability that it has been compromised. For
this reason, passwords should require refreshing
periodically, and users should be informed of the risk
of passwords which remain in use for too long.
- Password strength should be enforced intelligently.
Rather than restrict passwords to specific content, or
specific length, users should be encouraged to use upper
and lower case letters, numbers, and symbols in their
passwords. The system should also ensure that no
passwords are derived from dictionary words.
KC
wanna
be
unsigned char *check_passwd(char *plaintext){
ctext=simple_digest("sha1",plaintext,strlen(plaintext)...);
if (ctext==secret_password())
// Log me in
}
In Java:
String plainText = new String(plainTextIn)
MessageDigest encer = MessageDigest.getInstance("SHA");
encer.update(plainTextIn);
byte[] digest = password.digest();
if (digest==secret_password())
//log me in
