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CAPEC-55: Rainbow Table Password Cracking

Attack Pattern ID: 55
Abstraction: Standard
Status: Draft
Presentation Filter:
+ Description
An attacker gets access to the database table where hashes of passwords are stored. He then uses a rainbow table of pre-computed hash chains to attempt to look up the original password. Once the original password corresponding to the hash is obtained, the attacker uses the original password to gain access to the system. A password rainbow table stores hash chains for various passwords. A password chain is computed, starting from the original password, P, via a reduce(compression) function R and a hash function H. A recurrence relation exists where Xi+1 = R(H(Xi)), X0 = P. Then the hash chain of length n for the original password P can be formed: X1, X2, X3, ... , Xn-2, Xn-1, Xn, H(Xn). P and H(Xn) are then stored together in the rainbow table. Constructing the rainbow tables takes a very long time and is computationally expensive. A separate table needs to be constructed for the various hash algorithms (e.g. SHA1, MD5, etc.). However, once a rainbow table is computed, it can be very effective in cracking the passwords that have been hashed without the use of salt.
+ Likelihood Of Attack

Medium

+ Typical Severity

Medium

+ Relationships

The table(s) below shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf, ParentOf, MemberOf and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.

+ Relevant to the view "Mechanisms of Attack" (CAPEC-1000)
NatureTypeIDName
ChildOfStandard Attack PatternStandard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.49Password Brute Forcing
+ Execution Flow
Explore
  1. Determine application's/system's password policy: Determine the password policies of the target application/system. Determine minimum and maximum allowed password lengths. Determine format of allowed passwords (whether they are required or allowed to contain numbers, special characters, etc.). Determine account lockout policy (a strict account lockout policy will prevent brute force attacks).

    Techniques
    Determine minimum and maximum allowed password lengths.
    Determine format of allowed passwords (whether they are required or allowed to contain numbers, special characters, etc.).
    Determine account lockout policy (a strict account lockout policy will prevent brute force attacks).
  2. Obtain password hashes: An attacker gets access to the database table storing hashes of passwords or potentially just discovers a hash of an individual password. Obtain copy of database table or flat file containing password hashes (by breaking access controls, using SQL Injection, etc.) Obtain password hashes from platform-specific storage locations (e.g. Windows registry) Sniff network packets containing password hashes.

    Techniques
    Obtain copy of database table or flat file containing password hashes (by breaking access controls, using SQL Injection, etc.)
    Obtain password hashes from platform-specific storage locations (e.g. Windows registry)
    Sniff network packets containing password hashes.
Exploit
  1. Run rainbow table-based password cracking tool: An attacker finds or writes a password cracking tool that uses a previously computed rainbow table for the right hashing algorithm. It helps if the attacker knows what hashing algorithm was used by the password system. Run rainbow table-based password cracking tool such as Ophcrack or RainbowCrack. Reduction function must depend on application's/system's password policy.

    Techniques
    Run rainbow table-based password cracking tool such as Ophcrack or RainbowCrack. Reduction function must depend on application's/system's password policy.
+ Prerequisites
Hash of the original password is available to the attacker. For a better chance of success, an attacker should have more than one hash of the original password, and ideally the whole table.
Salt was not used to create the hash of the original password. Otherwise the rainbow tables have to be re-computed, which is very expensive and will make the attack effectively infeasible (especially if salt was added in iterations).
The system uses one factor password based authentication.
+ Skills Required
[Level: Low]
A variety of password cracking tools are available that can leverage a rainbow table. The more difficult part is to obtain the password hash(es) in the first place.
+ Resources Required
Rainbow table of password hash chains with the right algorithm used. A password cracking tool that leverages this rainbow table will also be required. Hash(es) of the password is required.
+ Indicators
This is a completely offline attack that an attacker can perform at their leisure after the password hashes are obtained.
+ Consequences

The table below specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

ScopeImpactLikelihood
Confidentiality
Access Control
Authorization
Gain Privileges
+ Mitigations
Use salt when computing password hashes. That is, concatenate the salt (random bits) with the original password prior to hashing it.
+ Example Instances
BusyBox 1.1.1 does not use a salt when generating passwords, which makes it easier for local users to guess passwords from a stolen password file using techniques such as rainbow tables. See also: CVE-2006-1058
+ Content History
Submissions
Submission DateSubmitterOrganization
2014-06-23CAPEC Content TeamThe MITRE Corporation

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Page Last Updated or Reviewed: July 31, 2018