CWE - CWE-323: Reusing a Nonce, Key Pair in Encryption (3.1)

Weakness ID: 323

Abstraction: Base
Structure: Simple

Status: Incomplete

Presentation Filter:

Description

Nonces should be used for the present occasion and only once.

Relationships

The table(s) below shows the weaknesses and high level categories that are related to this weakness. 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 PeerOf and CanAlsoBe are defined to show similar weaknesses that the user may want to explore.

Relevant to the view "Research Concepts" (CWE-1000)

Nature	Type	ID	Name
ChildOf	Base - a weakness that is described in an abstract fashion, but with sufficient details to infer specific methods for detection and prevention. More general than a Variant weakness, but more specific than a Class weakness.	344	Use of Invariant Value in Dynamically Changing Context

Relevant to the view "Architectural Concepts" (CWE-1008)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	1013	Encrypt Data

Relevant to the view "Development Concepts" (CWE-699)

Nature	Type	ID	Name
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	320	Key Management Errors

Background Details

Nonces are often bundled with a key in a communication exchange to produce a new session key for each exchange.

Modes Of Introduction

The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the software life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.

Phase	Note
Architecture and Design	REALIZATION: This weakness is caused during implementation of an architectural security tactic.

Applicable Platforms

The listings below show possible areas for which the given weakness could appear. These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. The platform is listed along with how frequently the given weakness appears for that instance.

Languages

Class: Language-Independent (Undetermined Prevalence)

Common Consequences

The table below specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. 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 weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.

Scope	Impact	Likelihood
Access Control	Technical Impact: Bypass Protection Mechanism; Gain Privileges or Assume Identity Potentially a replay attack, in which an attacker could send the same data twice, could be crafted if nonces are allowed to be reused. This could allow a user to send a message which masquerades as a valid message from a valid user.

Likelihood Of Exploit

High

Demonstrative Examples

Example 1

This code takes a password, concatenates it with a nonce, then encrypts it before sending over a network:

(bad code)

Example Language: C

void encryptAndSendPassword(char *password){

char *nonce = "bad";
...
char *data = (unsigned char*)malloc(20);
int para_size = strlen(nonce) + strlen(password);
char *paragraph = (char*)malloc(para_size);
SHA1((const unsigned char*)paragraph,parsize,(unsigned char*)data);
sendEncryptedData(data)

}

Because the nonce used is always the same, an attacker can impersonate a trusted party by intercepting and resending the encrypted password. This attack avoids the need to learn the unencrypted password.

Example 2

This code sends a command to a remote server, using an encrypted password and nonce to prove the command is from a trusted party:

(bad code)

Example Language: C++

String command = new String("some command to execute");
MessageDigest nonce = MessageDigest.getInstance("SHA");
nonce.update(String.valueOf("bad nonce"));
byte[] nonce = nonce.digest();
MessageDigest password = MessageDigest.getInstance("SHA");
password.update(nonce + "secretPassword");
byte[] digest = password.digest();
sendCommand(digest, command)

Once again the nonce used is always the same. An attacker may be able to replay previous legitimate commands or execute new arbitrary commands.

Potential Mitigations

Phase: Implementation

Refuse to reuse nonce values.

Phase: Implementation

Use techniques such as requiring incrementing, time based and/or challenge response to assure uniqueness of nonces.

Memberships

This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources.

Nature	Type	ID	Name
MemberOf	View - a subset of CWE entries that provides a way of examining CWE content. The two main view structures are Slices (flat lists) and Graphs (containing relationships between entries).	884	CWE Cross-section
MemberOf	Category - a CWE entry that contains a set of other entries that share a common characteristic.	959	SFP Secondary Cluster: Weak Cryptography

Taxonomy Mappings

Mapped Taxonomy Name	Node ID	Fit	Mapped Node Name
CLASP			Reusing a nonce, key pair in encryption

Content History

Submissions
Submission Date	Submitter	Organization
	CLASP

Modifications
Modification Date	Modifier	Organization
2008-07-01	Eric Dalci	Cigital
2008-07-01	updated Time_of_Introduction
2008-09-08	CWE Content Team	MITRE
2008-09-08	updated Background_Details, Common_Consequences, Relationships, Taxonomy_Mappings
2011-06-01	CWE Content Team	MITRE
2011-06-01	updated Common_Consequences
2012-05-11	CWE Content Team	MITRE
2012-05-11	updated Relationships
2012-10-30	CWE Content Team	MITRE
2012-10-30	updated Demonstrative_Examples, Potential_Mitigations
2014-07-30	CWE Content Team	MITRE
2014-07-30	updated Relationships
2017-11-08	CWE Content Team	MITRE
2017-11-08	updated Applicable_Platforms, Modes_of_Introduction, Relationships


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Common Weakness Enumeration

CWE-323: Reusing a Nonce, Key Pair in Encryption