用户工具

站点工具


cwe:cn:definition:285

CWE-285:授权机制不恰当

Description Summary

The software does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.

Extended Description

Assuming a user with a given identity, authorization is the process of determining whether that user can access a given resource, based on the user's privileges and any permissions or other access-control specifications that apply to the resource.

When access control checks are not applied consistently - or not at all - users are able to access data or perform actions that they should not be allowed to perform. This can lead to a wide range of problems, including information exposures, denial of service, and arbitrary code execution.

Modes of Introduction

A developer may introduce authorization weaknesses because of a lack of understanding about the underlying technologies. For example, a developer may assume that attackers cannot modify certain inputs such as headers or cookies.

Authorization weaknesses may arise when a single-user application is ported to a multi-user environment.

Background Details

An access control list (ACL) represents who/what has permissions to a given object. Different operating systems implement (ACLs) in different ways. In UNIX, there are three types of permissions: read, write, and execute. Users are divided into three classes for file access: owner, group owner, and all other users where each class has a separate set of rights. In Windows NT, there are four basic types of permissions for files: “No access”, “Read access”, “Change access”, and “Full control”. Windows NT extends the concept of three types of users in UNIX to include a list of users and groups along with their associated permissions. A user can create an object (file) and assign specified permissions to that object.

Likelihood of Exploit

High

Common Consequences

Scope Technical Impace Note
ConfidentialityRead application data
Read files or directories
An attacker could read sensitive data, either by reading the data directly from a data store that is not properly restricted, or by accessing insufficiently-protected, privileged functionality to read the data.
IntegrityModify application data
Modify files or directories
An attacker could modify sensitive data, either by writing the data directly to a data store that is not properly restricted, or by accessing insufficiently-protected, privileged functionality to write the data.
Access_ControlGain privileges / assume identityAn attacker could gain privileges by modifying or reading critical data directly, or by accessing insufficiently-protected, privileged functionality.

Detection Methods

Detection Method - 1

Automated Static Analysis

Automated static analysis is useful for detecting commonly-used idioms for authorization. A tool may be able to analyze related configuration files, such as .htaccess in Apache web servers, or detect the usage of commonly-used authorization libraries.

Generally, automated static analysis tools have difficulty detecting custom authorization schemes. Even if they can be customized to recognize these schemes, they might not be able to tell whether the scheme correctly performs the authorization in a way that cannot be bypassed or subverted by an attacker.

2013/05/30 09:37

Detection Method - 2

Automated Dynamic Analysis

Automated dynamic analysis may find many or all possible interfaces that do not require authorization, but manual analysis is required to determine if the lack of authorization violates business logic

Detection Method - 3

Manual Analysis

This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.

Specifically, manual static analysis is useful for evaluating the correctness of custom authorization mechanisms.>These may be more effective than strictly automated techniques. This is especially the case with weaknesses that are related to design and business rules. However, manual efforts might not achieve desired code coverage within limited time constraints.

Detection Method - 4

Manual Static Analysis - Binary / Bytecode

According to SOAR, the following detection techniques may be useful:

Detection Method - 5

=== Dynamic Analysis with automated results interpretation === According to SOAR, the following detection techniques may be useful:

Detection Method - 6

Dynamic Analysis with manual results interpretation

According to SOAR, the following detection techniques may be useful:

Detection Method - 7

Manual Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Detection Method - 8

Automated Static Analysis - Source Code

According to SOAR, the following detection techniques may be useful:

Detection Method - 9

Architecture / Design Review

According to SOAR, the following detection techniques may be useful:

Potential Mitigations

Mitigation - 1

Architecture and Design

Divide the software into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.

Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.

Mitigation - 2

Architecture and Design

Ensure that you perform access control checks related to your business logic. These checks may be different than the access control checks that you apply to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor.

Mitigation - 3

Architecture and Design

Strategy:Libraries or Frameworks

Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

For example, consider using authorization frameworks such as the JAAS Authorization Framework [R.863.4] and the OWASP ESAPI Access Control feature [R.863.5].

2013/05/30 09:37

Mitigation - 4

Architecture and Design

For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.

One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

Mitigation - 5

System Configuration Installation

Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a “default deny” policy when defining these ACLs.

Demonstrative Examples

Example - 1

This function runs an arbitrary SQL query on a given database, returning the result of the query.

function runEmployeeQuery($dbName, $name){ 
mysql_select_db($dbName,$globalDbHandle) or die("Could not open Database".$dbName); 
//Use a prepared statement to avoid CWE-89 
$preparedStatement = $globalDbHandle->prepare('SELECT * FROM employees WHERE name = :name'); 
$preparedStatement->execute(array(':name' => $name)); 
return $preparedStatement->fetchAll(); 
 
} 
/.../ 
$employeeRecord = runEmployeeQuery('EmployeeDB',$_GET['EmployeeName']); 

While this code is careful to avoid SQL Injection, the function does not confirm the user sending the query is authorized to do so. An attacker may be able to obtain sensitive employee information from the database.

2013/05/30 13:23

Example - 2

The following program could be part of a bulletin board system that allows users to send private messages to each other. This program intends to authenticate the user before deciding whether a private message should be displayed. Assume that LookupMessageObject() ensures that the $id argument is numeric, constructs a filename based on that id, and reads the message details from that file. Also assume that the program stores all private messages for all users in the same directory.

sub DisplayPrivateMessage { 
my($id) = @_; 
my $Message = LookupMessageObject($id); 
print "From: " . encodeHTML($Message->{from}) . "<br>\n"; 
print "Subject: " . encodeHTML($Message->{subject}) . "\n"; 
print "<hr>\n"; 
print "Body: " . encodeHTML($Message->{body}) . "\n"; 
 
} 
 
my $q = new CGI; 
# For purposes of this example, assume that CWE-309 and 
# CWE-523 do not apply. 
if (! AuthenticateUser($q->param('username'), $q->param('password'))) { 
ExitError("invalid username or password"); 
 
} 
 
my $id = $q->param('id'); 
DisplayPrivateMessage($id); 

While the program properly exits if authentication fails, it does not ensure that the message is addressed to the user. As a result, an authenticated attacker could provide any arbitrary identifier and read private messages that were intended for other users.

One way to avoid this problem would be to ensure that the “to” field in the message object matches the username of the authenticated user.

2013/05/30 13:23

Observed Examples

Reference Description
CVE-2009-3168Web application does not restrict access to admin scripts, allowing authenticated users to reset administrative passwords.
CVE-2009-2960Web application does not restrict access to admin scripts, allowing authenticated users to modify passwords of other users.
CVE-2009-3597Web application stores database file under the web root with insufficient access control (CWE-219), allowing direct request.
CVE-2009-2282Terminal server does not check authorization for guest access.
CVE-2009-3230Database server does not use appropriate privileges for certain sensitive operations.
CVE-2009-2213Gateway uses default “Allow” configuration for its authorization settings.
CVE-2009-0034Chain: product does not properly interpret a configuration option for a system group, allowing users to gain privileges.
CVE-2008-6123Chain: SNMP product does not properly parse a configuration option for which hosts are allowed to connect, allowing unauthorized IP addresses to connect.
CVE-2008-5027System monitoring software allows users to bypass authorization by creating custom forms.
CVE-2008-7109Chain: reliance on client-side security (CWE-602) allows attackers to bypass authorization using a custom client.
CVE-2008-3424Chain: product does not properly handle wildcards in an authorization policy list, allowing unintended access.
CVE-2009-3781Content management system does not check access permissions for private files, allowing others to view those files.
CVE-2008-4577ACL-based protection mechanism treats negative access rights as if they are positive, allowing bypass of intended restrictions.
CVE-2008-6548Product does not check the ACL of a page accessed using an “include” directive, allowing attackers to read unauthorized files.
CVE-2007-2925Default ACL list for a DNS server does not set certain ACLs, allowing unauthorized DNS queries.
CVE-2006-6679Product relies on the X-Forwarded-For HTTP header for authorization, allowing unintended access by spoofing the header.
CVE-2005-3623OS kernel does not check for a certain privilege before setting ACLs for files.
CVE-2005-2801Chain: file-system code performs an incorrect comparison (CWE-697), preventing default ACLs from being properly applied.
CVE-2001-1155Chain: product does not properly check the result of a reverse DNS lookup because of operator precedence (CWE-783), allowing bypass of DNS-based access restrictions.
cwe/cn/definition/285.txt · 最后更改: 2014/09/04 14:31 (外部编辑)