CWE-209 通过错误消息导致的信息暴露

Information Exposure Through an Error Message

结构: Simple

Abstraction: Base

状态: Draft

被利用可能性: High

基本描述

The software generates an error message that includes sensitive information about its environment, users, or associated data.

扩展描述

The sensitive information may be valuable information on its own (such as a password), or it may be useful for launching other, more deadly attacks. If an attack fails, an attacker may use error information provided by the server to launch another more focused attack. For example, an attempt to exploit a path traversal weakness (CWE-22) might yield the full pathname of the installed application. In turn, this could be used to select the proper number of ".." sequences to navigate to the targeted file. An attack using SQL injection (CWE-89) might not initially succeed, but an error message could reveal the malformed query, which would expose query logic and possibly even passwords or other sensitive information used within the query.

相关缺陷

  • cwe_Nature: ChildOf cwe_CWE_ID: 200 cwe_View_ID: 1000 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 200 cwe_View_ID: 699 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 200 cwe_View_ID: 1003 cwe_Ordinal: Primary

  • cwe_Nature: ChildOf cwe_CWE_ID: 755 cwe_View_ID: 1000

适用平台

Language: [{'cwe_Name': 'PHP', 'cwe_Prevalence': 'Often'}, {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}]

常见的影响

范围 影响 注释
Confidentiality Read Application Data Often this will either reveal sensitive information which may be used for a later attack or private information stored in the server.

检测方法

Manual Analysis

This weakness generally requires domain-specific interpretation using manual analysis. However, the number of potential error conditions may be too large to cover completely within limited time constraints.

Automated Analysis

Automated methods may be able to detect certain idioms automatically, such as exposed stack traces or pathnames, but violation of business rules or privacy requirements is not typically feasible.

DM-2 Automated Dynamic Analysis

This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash, or generate incorrect results.

Error conditions may be triggered with a stress-test by calling the software simultaneously from a large number of threads or processes, and look for evidence of any unexpected behavior.

DM-12 Manual Dynamic Analysis

Identify error conditions that are not likely to occur during normal usage and trigger them. For example, run the program under low memory conditions, run with insufficient privileges or permissions, interrupt a transaction before it is completed, or disable connectivity to basic network services such as DNS. Monitor the software for any unexpected behavior. If you trigger an unhandled exception or similar error that was discovered and handled by the application's environment, it may still indicate unexpected conditions that were not handled by the application itself.

可能的缓解方案

MIT-39 Implementation

策略:

Ensure that error messages only contain minimal details that are useful to the intended audience, and nobody else. The messages need to strike the balance between being too cryptic and not being cryptic enough. They should not necessarily reveal the methods that were used to determine the error. Such detailed information can be used to refine the original attack to increase the chances of success. If errors must be tracked in some detail, capture them in log messages - but consider what could occur if the log messages can be viewed by attackers. Avoid recording highly sensitive information such as passwords in any form. Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a username is valid or not.

Implementation

策略:

Handle exceptions internally and do not display errors containing potentially sensitive information to a user.

MIT-33 Implementation

策略: Attack Surface Reduction

Use naming conventions and strong types to make it easier to spot when sensitive data is being used. When creating structures, objects, or other complex entities, separate the sensitive and non-sensitive data as much as possible.

MIT-40 ['Implementation', 'Build and Compilation']

策略: Compilation or Build Hardening

Debugging information should not make its way into a production release.

MIT-40 ['Implementation', 'Build and Compilation']

策略: Environment Hardening

Debugging information should not make its way into a production release.

System Configuration

策略:

Where available, configure the environment to use less verbose error messages. For example, in PHP, disable the display_errors setting during configuration, or at runtime using the error_reporting() function.

System Configuration

策略:

Create default error pages or messages that do not leak any information.

示例代码

例

In the following example, sensitive information might be printed depending on the exception that occurs.

bad Java

try {
/.../
}
catch (Exception e) {
System.out.println(e);
}

If an exception related to SQL is handled by the catch, then the output might contain sensitive information such as SQL query structure or private information. If this output is redirected to a web user, this may represent a security problem.

例

This code tries to open a database connection, and prints any exceptions that occur.

bad Java

try {
openDbConnection();
}
//print exception message that includes exception message and configuration file location
catch (Exception $e) {
echo 'Caught exception: ', $e->getMessage(), '\n';
echo 'Check credentials in config file at: ', $Mysql_config_location, '\n';
}

If an exception occurs, the printed message exposes the location of the configuration file the script is using. An attacker can use this information to target the configuration file (perhaps exploiting a Path Traversal weakness). If the file can be read, the attacker could gain credentials for accessing the database. The attacker may also be able to replace the file with a malicious one, causing the application to use an arbitrary database.

例

The following code generates an error message that leaks the full pathname of the configuration file.

bad Perl

$ConfigDir = "/home/myprog/config";
$uname = GetUserInput("username");

# avoid CWE-22, CWE-78, others.
ExitError("Bad hacker!") if ($uname !~ /^\w+$/);
$file = "$ConfigDir/$uname.txt";
if (! (-e $file)) {
ExitError("Error: $file does not exist");
}
...

If this code is running on a server, such as a web application, then the person making the request should not know what the full pathname of the configuration directory is. By submitting a username that does not produce a $file that exists, an attacker could get this pathname. It could then be used to exploit path traversal or symbolic link following problems that may exist elsewhere in the application.

例

In the example below, the method getUserBankAccount retrieves a bank account object from a database using the supplied username and account number to query the database. If an SQLException is raised when querying the database, an error message is created and output to a log file.

bad Java

public BankAccount getUserBankAccount(String username, String accountNumber) {
BankAccount userAccount = null;
String query = null;
try {
if (isAuthorizedUser(username)) {
query = "SELECT * FROM accounts WHERE owner = "
+ username + " AND accountID = " + accountNumber;
DatabaseManager dbManager = new DatabaseManager();
Connection conn = dbManager.getConnection();
Statement stmt = conn.createStatement();
ResultSet queryResult = stmt.executeQuery(query);
userAccount = (BankAccount)queryResult.getObject(accountNumber);
}
} catch (SQLException ex) {
String logMessage = "Unable to retrieve account information from database,\nquery: " + query;
Logger.getLogger(BankManager.class.getName()).log(Level.SEVERE, logMessage, ex);
}
return userAccount;
}

The error message that is created includes information about the database query that may contain sensitive information about the database or query logic. In this case, the error message will expose the table name and column names used in the database. This data could be used to simplify other attacks, such as SQL injection (CWE-89) to directly access the database.

分析过的案例

标识 说明 链接
CVE-2008-2049 POP3 server reveals a password in an error message after multiple APOP commands are sent. Might be resultant from another weakness. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-2049
CVE-2007-5172 Program reveals password in error message if attacker can trigger certain database errors. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-5172
CVE-2008-4638 Composite: application running with high privileges allows user to specify a restricted file to process, which generates a parsing error that leaks the contents of the file. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-4638
CVE-2008-1579 Existence of user names can be determined by requesting a nonexistent blog and reading the error message. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-1579
CVE-2007-1409 Direct request to library file in web application triggers pathname leak in error message. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-1409
CVE-2008-3060 Malformed input to login page causes leak of full path when IMAP call fails. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-3060
CVE-2005-0603 Malformed regexp syntax leads to information exposure in error message. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-0603
CVE-2017-9615 verbose logging stores admin credentials in a world-readablelog file https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-9615
CVE-2018-1999036 SSH password for private key stored in build log https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-1999036

分类映射

映射的分类名 ImNode ID Fit Mapped Node Name
CLASP Accidental leaking of sensitive information through error messages
OWASP Top Ten 2007 A6 CWE More Specific Information Leakage and Improper Error Handling
OWASP Top Ten 2004 A7 CWE More Specific Improper Error Handling
OWASP Top Ten 2004 A10 CWE More Specific Insecure Configuration Management
The CERT Oracle Secure Coding Standard for Java (2011) ERR01-J Do not allow exceptions to expose sensitive information
Software Fault Patterns SFP23 Exposed Data

相关攻击模式

  • CAPEC-214
  • CAPEC-215
  • CAPEC-463
  • CAPEC-54
  • CAPEC-7

引用