CWE-323 在加密中重用Nonce与密钥对

Reusing a Nonce, Key Pair in Encryption

结构: Simple

Abstraction: Variant

状态: Incomplete

被利用可能性: High

基本描述

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

相关缺陷

  • cwe_Nature: ChildOf cwe_CWE_ID: 344 cwe_View_ID: 1000 cwe_Ordinal: Primary

适用平台

Language: {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}

常见的影响

范围 影响 注释
Access Control ['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.

可能的缓解方案

Implementation

策略:

Refuse to reuse nonce values.

Implementation

策略:

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

示例代码

例

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

bad 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.

例

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 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.

分类映射

映射的分类名 ImNode ID Fit Mapped Node Name
CLASP Reusing a nonce, key pair in encryption