COMMON ATTACK PATTERN ENUMERATION AND CLASSIFICATIONMITRE canlı kaydı

CAPEC-55

Rainbow Table Password Cracking

An attacker gets access to the database table where hashes of passwords are stored. They then use 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.

Soyutlama

Detailed

Tipik ciddiyet

Medium

Saldırı ihtimali

Medium

Saldırıyı anla

Bu saldırı kalıbı nedir?

An attacker gets access to the database table where hashes of passwords are stored. They then use 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.

Genişletilmiş açıklama

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.

Uygulama akışı

Saldırı adım adım nasıl ilerler?

1

Explore

Determine application's/system's password policy

Determine the password policies of the target application/system.

Kullanılan teknikler

  • 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).

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.

Kullanılan teknikler

  • 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.
2

Exploit

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.

Kullanılan teknikler

  • Run rainbow table-based password cracking tool such as Ophcrack or RainbowCrack. Reduction function must depend on application's/system's password policy.

Gereksinimler

Saldırının gerçekleşmesi için ne gerekir?

Ön koşullar

  • 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.

Gerekli beceri

  • 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.

Gerekli kaynak

  • 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.

Tespit

Saldırının göstergeleri nelerdir?

This is a completely offline attack that an attacker can perform at their leisure after the password hashes are obtained.

Etki

Başarılı saldırı neye yol açar?

Gain Privileges

Etkilenen alanlar: Confidentiality, Access Control, Authorization

Savunma

Nasıl önlenir ve etkisi azaltılır?

1
Use salt when computing password hashes. That is, concatenate the salt (random bits) with the original password prior to hashing it.

Gerçek dünya

MITRE örnek olayları

Örnek olay 1Detay
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
CAPEC-55: Rainbow Table Password Cracking — DayBreach Saldırı Sözlüğü · DayBreach