Microsoft SQL Server 2022 Instance Security Technical Implementation Guide

Database management includes the ability to control the number of users and user sessions using a DBMS. Unlimited concurrent connections to the DBMS could allow a successful denial-of-service (DoS) attack by exhausting connection resources; and a system can also fail or be degraded by an overload of legitimate users. Limiting the number of concurrent sessions per user is helpful in reducing these risks. This requirement addresses concurrent session control for a single account. It does not address concurrent sessions by a single user via multiple system accounts; and it does not deal with the total number of sessions across all accounts. The capability to limit the number of concurrent sessions per user must be configured in or added to the DBMS (for example, by use of a logon trigger), when this is technically feasible. Note that it is not sufficient to limit sessions via a web server or application server alone, because legitimate users and adversaries can potentially connect to the DBMS by other means. The organization will need to define the maximum number of concurrent sessions by account type, by account, or a combination thereof. In deciding on the appropriate number, it is important to consider the work requirements of the various types of users. For example, two might be an acceptable limit for general users accessing the database via an application; but 10 might be too few for a database administrator using a database management GUI tool, where each query tab and navigation pane may count as a separate session. Sessions may also be referred to as connections or logons, which for the purposes of this requirement are synonyms.

Nonrepudiation of actions taken is required to maintain data integrity. Examples of particular actions taken by individuals include creating information, sending a message, approving information (e.g., indicating concurrence or signing a contract), and receiving a message. Nonrepudiation protects against later claims by a user of not having created, modified, or deleted a particular data item or collection of data in the database. In designing a database, the organization must define the types of data and the user actions that must be protected from repudiation. The implementation must then include building audit features into the application data tables and configuring the DBMS's audit tools to capture the necessary audit trail. Design and implementation also must ensure that applications pass individual user identification to the DBMS, even where the application connects to the DBMS with a standard, shared account. If the computer account of a remote computer is granted access to SQL Server, any service or scheduled task running as NT AUTHORITY\SYSTEM or NT AUTHORITY\NETWORK SERVICE can log into the instance and perform actions. These actions cannot be traced back to a specific user or process.

Nonrepudiation of actions taken is required to maintain data integrity. Examples of particular actions taken by individuals include creating information, sending a message, approving information (e.g., indicating concurrence or signing a contract), and receiving a message. Nonrepudiation protects against later claims by a user of not having created, modified, or deleted a particular data item or collection of data in the database. In designing a database, the organization must define the types of data and the user actions that must be protected from repudiation. The implementation must then include building audit features into the application data tables and configuring the DBMS's audit tools to capture the necessary audit trail. Design and implementation also must ensure that applications pass individual user identification to the DBMS, even where the application connects to the DBMS with a standard, shared account. Any user with enough access to the server can execute a task that will be run as NT AUTHORITY\SYSTEM either using task scheduler or other tools. At this point, NT AUTHORITY\SYSTEM essentially becomes a shared account because the operating system and SQL Server are unable to determine who created the process. Prior to SQL Server 2012, NT AUTHORITY\SYSTEM was a member of the sysadmin role by default. This allowed jobs/tasks to be executed in SQL Server without the approval or knowledge of the DBA because it looked like operating system activity.

Nonrepudiation of actions taken is required to maintain data integrity. Examples of particular actions taken by individuals include creating information, sending a message, approving information (e.g., indicating concurrence or signing a contract), and receiving a message. Nonrepudiation protects against later claims by a user of not having created, modified, or deleted a particular data item or collection of data in the database. In designing a database, the organization must define the types of data and the user actions that must be protected from repudiation. The implementation must then include building audit features into the application data tables and configuring SQL Server's audit tools to capture the necessary audit trail. Design and implementation also must ensure that applications pass individual user identification to SQL Server, even where the application connects to SQL Server with a standard, shared account. Satisfies: SRG-APP-000080-DB-000063, SRG-APP-000815-DB-000160

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within SQL Server (e.g., process, module). Certain specific application functionalities may be audited as well. The list of audited events is the set of events for which audits are to be generated. This set of events is typically a subset of the list of all events for which the system is capable of generating audit records. DOD has defined the list of events for which SQL Server will provide an audit record generation capability as the following: (i) Successful and unsuccessful attempts to access, modify, or delete privileges, security objects, security levels, or categories of information (e.g., classification levels); (ii) Access actions, such as successful and unsuccessful logon attempts, privileged activities, or other system-level access, starting and ending time for user access to the system, concurrent logons from different workstations, successful and unsuccessful accesses to objects, all program initiations, and all direct access to the information system; and (iii) All account creation, modification, disabling, and termination actions. Organizations may define additional events requiring continuous or ad hoc auditing.

Without the capability to restrict which roles and individuals can select which events are audited, unauthorized personnel may be able to prevent or interfere with the auditing of critical events. Suppression of auditing could permit an adversary to evade detection. Misconfigured audits can degrade the system's performance by overwhelming the audit log. Misconfigured audits may also make it more difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Under some circumstances, it may be useful to monitor who/what is reading privilege/permission/role information. Therefore, monitoring must be possible. DBMSs typically make such information available through views or functions. This requirement includes explicit requests for privilege/permission/role membership information. It does not refer to the implicit retrieval of privileges/permissions/role memberships that SQL Server continually performs to determine if any and every action on the database is permitted. Changes to the security configuration must also be tracked. Security configuration tracking applies to situations where security data is retrieved or modified via data manipulation operations, as opposed to via specialized security functionality. In a SQL environment, types of access include but are not necessarily limited to: SELECT INSERT UPDATE DELETE EXECUTE Changes in categorized information must be tracked. Without an audit trail, unauthorized access to protected data could go undetected. For detailed information on categorizing information, refer to FIPS Publication 199, Standards for Security Categorization of Federal Information and Information Systems, and FIPS Publication 200, Minimum Security Requirements for Federal Information and Information Systems. To aid in diagnosis, it is necessary to track failed attempts in addition to the successful ones. Satisfies: SRG-APP-000091-DB-000325, SRG-APP-000091-DB-000066, SRG-APP-000492-DB-000332, SRG-APP-000492-DB-000333, SRG-APP-000494-DB-000344, SRG-APP-000494-DB-000345, SRG-APP-000498-DB-000346, SRG-APP-000498-DB-000347, SRG-APP-000502-DB-000348, SRG-APP-000502-DB-000349, SRG-APP-000507-DB-000356, SRG-APP-000507-DB-000357

Session auditing is for use when a user's activities are under investigation. To be sure of capturing all activity during those periods when session auditing is in use, it needs to be in operation for the whole time SQL Server is running.

Information system auditing capability is critical for accurate forensic analysis. Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information. To support analysis, some types of events will need information to be logged that exceeds the basic requirements of event type, time stamps, location, source, outcome, and user identity. If additional information is not available, it could negatively impact forensic investigations into user actions or other malicious events. The organization must determine what additional information is required for complete analysis of the audited events. The additional information required is dependent on the type of information (e.g., sensitivity of the data and the environment within which it resides). At a minimum, the organization must employ either full-text recording of privileged commands or the individual identities of users of shared accounts, or both. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. Examples of detailed information the organization may require in audit records are full-text recording of privileged commands or the individual identities of shared account users.

If audit data were to become compromised, competent forensic analysis and discovery of the true source of potentially malicious system activity would be difficult, if not impossible, to achieve. In addition, access to audit records provides information an attacker could potentially use to their advantage. To ensure the veracity of audit data, the information system and/or the application must protect audit information from any and all unauthorized access. This includes read, write, copy, etc. This requirement can be achieved through multiple methods, which will depend on system architecture and design. Some commonly employed methods include ensuring log files enjoy the proper file system permissions using file system protections and limiting log data location. Additionally, applications with user interfaces to audit records should not allow for the unfettered manipulation of or access to those records via the application. If the application provides access to the audit data, the application becomes accountable for ensuring that audit information is protected from unauthorized access. SQL Server is able to view and manipulate audit file data. Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity. Satisfies: SRG-APP-000118-DB-000059, SRG-APP-000119-DB-000060, SRG-APP-000120-DB-000061

Protecting audit data also includes identifying and protecting the tools used to view and manipulate log data. Therefore, protecting audit tools is necessary to prevent unauthorized operation on audit data. Applications providing tools to interface with audit data will leverage user permissions and roles identifying the user accessing the tools and the corresponding rights the user enjoys in order make access decisions regarding the modification of audit tools. SQL Server is an application that does provide access to audit data. Audit tools include, but are not limited to, vendor-provided and open-source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. If an attacker were to gain access to audit tools, they could analyze audit logs for system weaknesses or weaknesses in the auditing itself. An attacker could also manipulate logs to hide evidence of malicious activity. Satisfies: SRG-APP-000121-DB-000202, SRG-APP-000122-DB-000203, SRG-APP-000123-DB-000204

If the system were to allow any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process. Accordingly, only qualified and authorized individuals must be allowed to obtain access to information system components for purposes of initiating changes, including upgrades and modifications. Unmanaged changes that occur to the database software libraries or configuration can lead to unauthorized or compromised installations.

If the system were to allow any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process. Accordingly, only qualified and authorized individuals must be allowed to obtain access to information system components for purposes of initiating changes, including upgrades and modifications. Unmanaged changes that occur to the database software libraries or configuration can lead to unauthorized or compromised installations.

When dealing with change control issues, it should be noted any changes to the hardware, software, and/or firmware components of the information system and/or application can potentially have significant effects on the overall security of the system. Multiple applications can provide a cumulative negative effect. A vulnerability and subsequent exploit to one application can lead to an exploit of other applications sharing the same security context. For example, an exploit to a web server process that leads to unauthorized administrative access to host system directories can most likely lead to a compromise of all applications hosted by the same system. Database software not installed using dedicated directories both threatens and is threatened by other hosted applications. Access controls defined for one application may by default provide access to the other application's database objects or directories. Any method that provides any level of separation of security context assists in the protection between applications.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for software products to provide, or install by default, functionality exceeding requirements or mission objectives. Examples include, but are not limited to, installing advertising software, demonstrations, or browser plugins not related to requirements or providing a wide array of functionality, not required for every mission, that cannot be disabled. DBMSs must adhere to the principles of least functionality by providing only essential capabilities. Demonstration and sample database objects and applications present publicly known attack points for malicious users. These demonstration and sample objects are meant to provide simple examples of coding specific functions and are not developed to prevent vulnerabilities from being introduced to SQL Server and host system.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for software products to provide, or install by default, functionality exceeding requirements or mission objectives. DBMSs must adhere to the principles of least functionality by providing only essential capabilities.

SQL Server is capable of providing a wide range of features and services. Some of the default features and services may not be necessary and enabling them could adversely affect the security of the system. Enabling the replication Xps opens a significant attack surface area that can be used by an attacker to gather information about the system and potentially abuse the privileges of SQL Server.

SQL Server is capable of providing a wide range of features and services. Some of the default features and services may not be necessary and enabling them could adversely affect the security of the system. The External Scripts Enabled feature allows scripts external to SQL such as files located in an R library to be executed.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different OS security context than SQL Server and provide unauthorized access to the host system. SQL Server is capable of providing a wide range of features and services. Some of the features and services, provided by default, may not be necessary, and enabling them could adversely affect the security of the system. The Remote Data Archive feature allows an export of local SQL Server data to an Azure SQL Database. An exploit to the SQL Server instance could result in a compromise of the host system and external SQL Server resources.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different OS security context than SQL Server and provide unauthorized access to the host system. The Allow Polybase Export feature allows an export of data to an external data source such as Hadoop File System or Azure Data Lake. An exploit to the SQL Server instance could result in a compromise of the host system and external SQL Server resources.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different OS security context than SQL Server and provide unauthorized access to the host system. SQL Server is capable of providing a wide range of features and services. Some of the features and services, provided by default, may not be necessary, and enabling them could adversely affect the security of the system. The "Hadoop Connectivity" feature allows multiple types of external data sources to be created and used across all sessions on the server. An exploit to the SQL Server instance could result in a compromise of the host system and external SQL Server resources.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different OS security context than SQL Server and provide unauthorized access to the host system. The "Remote Access" option controls the execution of local stored procedures on remote servers or remote stored procedures on local server. Remote access functionality can be abused to launch a denial-of-service (DoS) attack on remote servers by off-loading query processing to a target.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different OS security context than SQL Server and provide unauthorized access to the host system. A linked server allows for access to distributed, heterogeneous queries against OLE DB data sources. After a linked server is created, distributed queries can be run against this server, and queries can join tables from more than one data source. If the linked server is defined as an instance of SQL Server, remote stored procedures can be executed. This access may be exploited by malicious users who have compromised the integrity of the SQL Server.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different OS security context than SQL Server and provide unauthorized access to the host system. Extended stored procedures are DLLs that an instance of SQL Server can dynamically load and run. Extended stored procedures run directly in the address space of an instance of SQL Server and are programmed by using the SQL Server Extended Stored Procedure API. Nonstandard extended stored procedures can compromise the integrity of the SQL Server process. This feature will be removed in a future version of Microsoft SQL Server. Do not use this feature in new development work and modify applications that currently use this feature as soon as possible.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different OS security context than SQL Server and provide unauthorized access to the host system. The CLR component of the .NET Framework for Microsoft Windows in SQL Server allows users to write stored procedures, triggers, user-defined types, user-defined functions, user-defined aggregates, and streaming table-valued functions, using any .NET Framework language, including Microsoft Visual Basic .NET and Microsoft Visual C#. CLR packing assemblies can access resources protected by .NET Code Access Security when it runs managed code. Specifying UNSAFE enables the code in the assembly complete freedom to perform operations in the SQL Server process space that can potentially compromise the robustness of SQL Server. UNSAFE assemblies can also potentially subvert the security system of either SQL Server or the common language runtime.

Information systems are capable of providing a wide variety of functions and services. Some of the default functions and services may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different OS security context than SQL Server and provide unauthorized access to the host system. The xp_cmdshell extended stored procedure allows execution of host executables outside the controls of database access permissions. This access may be exploited by malicious users who have compromised the integrity of the SQL Server database process to control the host operating system to perpetrate additional malicious activity.

To prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary physical and logical ports on information systems. Applications are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., email and web services); however, doing so increases risk over limiting the services provided by any one component. To support the requirements and principles of least functionality, the application must support the organizational requirements providing only essential capabilities and limiting the use of ports to only those required, authorized, and approved to conduct official business or to address authorized quality of life issues. SQL Server using ports deemed unsafe is open to attack through those ports. This can allow unauthorized access to the database and through the database to other components of the information system.

To prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary protocols on information systems. Applications are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., email and web services); however, doing so increases risk over limiting the services provided by any one component. To support the requirements and principles of least functionality, the application must support the organizational requirements providing only essential capabilities and limiting the use of protocols to only those required, authorized, and approved to conduct official business or to address authorized quality of life issues. SQL Server using protocols deemed unsafe is open to attack through those protocols. This can allow unauthorized access to the database and through the database to other components of the information system. Satisfies: SRG-APP-000142-DB-000094, SRG-APP-000383-DB-000364

To ensure accountability and prevent unauthenticated access, organizational users must be identified and authenticated to prevent potential misuse and compromise of the system. Organizational users include organizational employees or individuals the organization deems to have equivalent status of employees (e.g., contractors). Organizational users (and any processes acting on behalf of users) must be uniquely identified and authenticated for all accesses, except the following: (i) Accesses explicitly identified and documented by the organization. Organizations document specific user actions that can be performed on the information system without identification or authentication; and (ii) Accesses that occur through authorized use of group authenticators without individual authentication. Organizations may require unique identification of individuals using shared accounts for detailed accountability of individual activity. Satisfies: SRG-APP-000148-DB-000103, SRG-APP-000180-DB-000115

The purpose of this control is to prevent information, including encrypted representations of information, produced by the actions of a prior user/role (or the actions of a process acting on behalf of a prior user/role) from being available to any current user/role (or current process) that obtains access to a shared system resource (e.g., registers, main memory, secondary storage) after the resource has been released back to the information system. Control of information in shared resources is also referred to as object reuse. When IFI is in use, the deleted disk content is overwritten only as new data is written to the files. For this reason, the deleted content might be accessed by an unauthorized principal until some other data writes on that specific area of the data file. Historically, transaction log files couldn't be initialized instantaneously. However, starting with SQL Server 2022 (16.x) (all editions), transaction log autogrowth events up to 64 MB can benefit from instant file initialization. The default auto growth size increment for new databases is 64 MB. Transaction log file autogrowth events larger than 64 MB can't benefit from instant file initialization. Instant file initialization is allowed for transaction log growth on databases that have transparent data encryption (TDE) enabled, due to the nature of how the transaction log file is expanded, and the fact that the transaction log is written into in a serial fashion.

The purpose of this control is to prevent information, including encrypted representations of information, produced by the actions of a prior user/role (or the actions of a process acting on behalf of a prior user/role) from being available to any current user/role (or current process) that obtains access to a shared system resource (e.g., registers, main memory, secondary storage) after the resource has been released back to the information system. Control of information in shared resources is also referred to as object reuse.

Applications, including SQL Server, must prevent unauthorized and unintended information transfer via shared system resources. Permitting only DBMS processes and authorized, administrative users to have access to the files where the database resides helps ensure that those files are not shared inappropriately and are not open to backdoor access and manipulation.

With respect to database management systems, one class of threat is known as SQL Injection, or more generally, code injection. It takes advantage of the dynamic execution capabilities of various programming languages, including dialects of SQL. In such cases, the attacker deduces the manner in which SQL statements are being processed, either from inside knowledge or by observing system behavior in response to invalid inputs. When the attacker identifies scenarios where SQL queries are being assembled by application code (which may be within the database or separate from it) and executed dynamically, the attacker is then able to craft input strings that subvert the intent of the query. Potentially, the attacker can gain unauthorized access to data, including security settings, and severely corrupt or destroy the database. The principal protection against code injection is not to use dynamic execution except where it provides necessary functionality that cannot be used otherwise. Use strongly typed data items rather than general-purpose strings as input parameters to task-specific, precompiled stored procedures and functions (and triggers). This calls for inspection of application source code, which will require collaboration with the application developers. It is recognized that in many cases, the database administrator (DBA) is organizationally separate from the application developers, and may have limited, if any, access to source code. Nevertheless, protections of this type are so important to the secure operation of databases that they must not be ignored. At a minimum, the DBA must attempt to obtain assurances from the development organization that this issue has been addressed and must document what has been discovered.

With respect to database management systems, one class of threat is known as SQL Injection, or more generally, code injection. It takes advantage of the dynamic execution capabilities of various programming languages, including dialects of SQL. In such cases, the attacker deduces the manner in which SQL statements are being processed, either from inside knowledge or by observing system behavior in response to invalid inputs. When the attacker identifies scenarios where SQL queries are being assembled by application code (which may be within the database or separate from it) and executed dynamically, the attacker is then able to craft input strings that subvert the intent of the query. Potentially, the attacker can gain unauthorized access to data, including security settings, and severely corrupt or destroy the database. The principal protection against code injection is not to use dynamic execution except where it provides necessary functionality that cannot be used otherwise. Use strongly typed data items rather than general-purpose strings as input parameters to task-specific, precompiled stored procedures and functions (and triggers). When dynamic execution is necessary, ways to mitigate the risk include the following, which should be implemented both in the on-screen application and at the database level, in the stored procedures: - Allow strings as input only when necessary. - Rely on data typing to validate numbers, dates, etc. Do not accept invalid values. If substituting other values for them, think carefully about whether this could be subverted. - Limit the size of input strings to what is truly necessary. - If single quotes/apostrophes, double quotes, semicolons, equals signs, angle brackets, or square brackets will never be valid as input, reject them. - If comment markers will never be valid as input, reject them. In SQL, these are -- or /* */ - If HTML and XML tags, entities, comments, etc., will never be valid, reject them. - If wildcards are present, reject them unless truly necessary. In SQL these are the underscore and the percentage sign, and the word ESCAPE is also a clue that wildcards are in use. - If SQL key words, such as SELECT, INSERT, UPDATE, DELETE, CREATE, ALTER, DROP, ESCAPE, UNION, GRANT, REVOKE, DENY, MODIFY will never be valid, reject them. Use case-insensitive comparisons when searching for these. Bear in mind that some of these words, particularly Grant (as a person's name), could also be valid input. - If there are range limits on the values that may be entered, enforce those limits. - Institute procedures for inspection of programs for correct use of dynamic coding, by a party other than the developer. - Conduct rigorous testing of program modules that use dynamic coding, searching for ways to subvert the intended use. - Record the inspection and testing in the system documentation. - Bear in mind that all this applies not only to screen input, but also to the values in an incoming message to a web service or to a stored procedure called by a software component that has not itself been hardened in these ways. Not only can the caller be subject to such vulnerabilities; it may itself be the attacker. This calls for inspection of application source code, which will require collaboration with the application developers. It is recognized that in many cases, the database administrator (DBA) is organizationally separate from the application developers, and may have limited, if any, access to source code. Nevertheless, protections of this type are so important to the secure operation of databases that they must not be ignored. At a minimum, the DBA must attempt to obtain assurances from the development organization that this issue has been addressed and must document what has been discovered.

If SQL Server provides too much information in error logs and administrative messages to the screen, this could lead to compromise. The structure and content of error messages need to be carefully considered by the organization and development team. The extent to which the information system is able to identify and handle error conditions is guided by organizational policy and operational requirements. Some default DBMS error messages can contain information that could aid an attacker in, among other things, identifying the database type, host address, or state of the database. Custom errors may contain sensitive customer information. It is important that detailed error messages be visible only to those who are authorized to view them; that general users receive only generalized acknowledgment that errors have occurred; and that these generalized messages appear only when relevant to the user's task. For example, a message along the lines of, "An error has occurred. Unable to save your changes. If this problem persists, please contact your help desk." would be relevant. A message such as "Warning: your transaction generated a large number of page splits" would likely not be relevant. "ABGQ is not a valid widget code." would be appropriate; but "The INSERT statement conflicted with the FOREIGN KEY constraint "WidgetTransactionFK". The conflict occurred in database "DB7", table "dbo.WidgetMaster", column 'WidgetCode'" would not, as it reveals too much about the database structure.

Preventing nonprivileged users from executing privileged functions mitigates the risk that unauthorized individuals or processes may gain unnecessary access to information or privileges. System documentation should include a definition of the functionality considered privileged. Depending on circumstances, privileged functions can include, for example, establishing accounts, performing system integrity checks, or administering cryptographic key management activities. Nonprivileged users are individuals that do not possess appropriate authorizations. Circumventing intrusion detection and prevention mechanisms or malicious code protection mechanisms are examples of privileged functions that require protection from nonprivileged users. A privileged function in SQL Server/database context is any operation that modifies the structure of the database, its built-in logic, or its security settings. This would include all Data Definition Language (DDL) statements and all security-related statements. In an SQL environment, it encompasses, but is not necessarily limited to: CREATE ALTER DROP GRANT REVOKE DENY There may also be Data Manipulation Language (DML) statements that, subject to context, should be regarded as privileged. Possible examples include: TRUNCATE TABLE; DELETE, or DELETE affecting more than n rows, for some n, or DELETE without a WHERE clause; UPDATE or UPDATE affecting more than n rows, for some n, or UPDATE without a WHERE clause; Any SELECT, INSERT, UPDATE, or DELETE to an application-defined security table executed by other than a security principal. Depending on the capabilities of SQL Server and the design of the database and associated applications, the prevention of unauthorized use of privileged functions may be achieved by means of DBMS security features, database triggers, other mechanisms, or a combination of these.

In certain situations, to provide required functionality, a DBMS needs to execute internal logic (stored procedures, functions, triggers, etc.) and/or external code modules with elevated privileges. However, if the privileges required for execution are at a higher level than the privileges assigned to organizational users invoking the functionality applications/programs, those users are indirectly provided with greater privileges than assigned by organizations. Privilege elevation must be used only where necessary and protected from misuse.

Organizations are required to use a central log management system, so, under normal conditions, the audit space allocated to SQL Server on its own server will not be an issue. However, space will still be required on the server for SQL Server Audit records in transit, and, under abnormal conditions, this could fill up. Since a requirement exists to halt processing upon audit failure, a service outage would result. If support personnel are not notified immediately upon storage volume utilization reaching 75 percent, they are unable to plan for storage capacity expansion. The appropriate support staff include, at a minimum, the information system security officer (ISSO), the database administrator (DBA), and system administrator (SA). Monitoring of free space can be accomplished using Microsoft System Center or a third-party monitoring tool.

Organizations are required to use a central log management system, so, under normal conditions, the audit space allocated to SQL Server on its own server will not be an issue. However, space will still be required on the server for SQL Server Audit records in transit, and, under abnormal conditions, this could fill up. Since a requirement exists to halt processing upon audit failure, a service outage would result. If support personnel are not notified immediately upon storage volume utilization reaching 75 percent, they are unable to plan for storage capacity expansion. The appropriate support staff include, at a minimum, the information system security officer (ISSO), the database administrator (DBA), and the system administrator (SA). Monitoring of free space can be accomplished using Microsoft System Center or a third-party monitoring tool.

It is critical for the appropriate personnel to be aware if a system is at risk of failing to process audit logs as required. Without a real-time alert, security personnel may be unaware of an impending failure of the audit capability, and system operation may be adversely affected. The appropriate support staff include, at a minimum, the information system security officer (ISSO), the database administrator (DBA), and the system administrator (SA). A failure of database auditing will result in either the database continuing to function without auditing or in a complete halt to database operations. When audit processing fails, appropriate personnel must be alerted immediately to avoid further downtime or unaudited transactions. Alerts provide organizations with urgent messages. Real-time alerts provide these messages immediately (i.e., the time from event detection to alert occurs in seconds or less). Alerts can be generated using tools like the SQL Server Agent Alerts and Database Mail.

If time stamps are not consistently applied and there is no common time reference, it is difficult to perform forensic analysis. Time stamps generated by SQL Server must include date and time. Time is commonly expressed in UTC, a modern continuation of GMT, or local time with an offset from UTC.

Failure to provide logical access restrictions associated with changes to configuration may have significant effects on the overall security of the system. When dealing with access restrictions pertaining to change control, it should be noted that any changes to the hardware, software, and/or firmware components of the information system can potentially have significant effects on the overall security of the system. Accordingly, only qualified and authorized individuals should be allowed to obtain access to system components for the purposes of initiating changes, including upgrades and modifications.

Failure to provide logical access restrictions associated with changes to configuration may have significant effects on the overall security of the system. When dealing with access restrictions pertaining to change control, it should be noted that any changes to the hardware, software, and/or firmware components of the information system can potentially have significant effects on the overall security of the system. Accordingly, only qualified and authorized individuals should be allowed to obtain access to system components for the purposes of initiating changes, including upgrades and modifications.

Without auditing the enforcement of access restrictions against changes to configuration, it would be difficult to identify attempted attacks, and an audit trail would not be available for forensic investigation for after-the-fact actions. Enforcement actions are the methods or mechanisms used to prevent unauthorized changes to configuration settings. Enforcement action methods may be as simple as denying access to a file based on the application of file permissions (access restriction). Audit items may consist of lists of actions blocked by access restrictions or changes identified after the fact. Changes in the permissions, privileges, and roles granted to users and roles, as well as privileged activity, must be tracked. Without an audit trail, unauthorized elevation or restriction of privileges could go undetected. Elevated privileges give users access to information and functionality that they should not have; restricted privileges wrongly deny access to authorized users. A privileged function in this context is any operation that modifies the structure of the database, its built-in logic, or its security settings. This would include all Data Definition Language (DDL) statements and all security-related statements. In a SQL environment, it encompasses, but is not necessarily limited to, CREATE, ALTER, DROP, GRANT, REVOKE, and DENY. There may also be Data Manipulation Language (DML) statements that, subject to context, should be regarded as privileged. Possible examples in SQL include TRUNCATE TABLE, SELECT, INSERT, UPDATE, or DELETE (to a security table executed by a user other than a security principal). Depending on the capabilities of SQL Server and the design of the database and associated applications, audit logging may be achieved by means of DBMS auditing features, database triggers, other mechanisms, or a combination of these. Note that it is particularly important to audit, and tightly control, any action that weakens the implementation of this requirement, since the objective is to have a complete audit trail of all administrative activity. To aid in diagnosis, it is necessary to track failed attempts in addition to the successful ones. Satisfies: SRG-APP-000381-DB-000361, SRG-APP-000495-DB-000326, SRG-APP-000495-DB-000327, SRG-APP-000495-DB-000328, SRG-APP-000495-DB-000329, SRG-APP-000499-DB-000330, SRG-APP-000499-DB-000331, SRG-APP-000504-DB-000354, SRG-APP-000504-DB-000355

Database management systems can maintain separate execution domains for each executing process by assigning each process a separate address space. Each process has a distinct address space so that communication between processes is controlled through the security functions, and one process cannot modify the executing code of another process. Maintaining separate execution domains for executing processes can be achieved, for example, by implementing separate address spaces.

Database management systems can maintain separate execution domains for each executing process by assigning each process a separate address space. Each process has a distinct address space so that communication between processes is controlled through the security functions, and one process cannot modify the executing code of another process. Maintaining separate execution domains for executing processes can be achieved, for example, by implementing separate address spaces.

A common vulnerability is unplanned behavior when invalid inputs are received. This requirement guards against adverse or unintended system behavior caused by invalid inputs, where information system responses to the invalid input may be disruptive or cause the system to fail into an unsafe state. The behavior will be derived from the organizational and system requirements and includes, but is not limited to, notification of the appropriate personnel, creating an audit record, and rejecting invalid input. This calls for inspection of application source code, which will require collaboration with the application developers. It is recognized that in many cases, the database administrator (DBA) is organizationally separate from the application developers, and may have limited, if any, access to source code. Nevertheless, protections of this type are so important to the secure operation of databases that they must not be ignored. At a minimum, the DBA must attempt to obtain assurances from the development organization that this issue has been addressed and must document what has been discovered.

Security flaws with software applications, including database management systems, are discovered daily. Vendors are constantly updating and patching their products to address newly discovered security vulnerabilities. Organizations (including any contractor to the organization) are required to promptly install security-relevant software updates (e.g., patches, service packs, and hot fixes). Flaws discovered during security assessments, continuous monitoring, incident response activities, or information system error handling must also be addressed expeditiously. Organization-defined time periods for updating security-relevant software may vary based on a variety of factors including, for example, the security category of the information system or the criticality of the update (i.e., severity of the vulnerability related to the discovered flaw). This requirement will apply to software patch management solutions that are used to install patches across the enclave and also to applications themselves that are not part of that patch management solution. For example, many browsers today provide the capability to install their own patch software. Patch criticality, as well as system criticality, will vary. Therefore, the tactical situations regarding the patch management process will also vary. This means that the time period used must be a configurable parameter. Time frames for application of security-relevant software updates may be dependent upon the Information Assurance Vulnerability Management (IAVM) process. SQL Server will be configured to check for and install security-relevant software updates within an identified time period from the availability of the update. The specific time period will be defined by an authoritative source (e.g., IAVM, CTOs, DTMs, and STIGs).

Changes and deletions of the database objects (tables, views, procedures, functions) that record and control permissions, privileges, and roles granted to users and roles must be tracked. Without an audit trail, unauthorized changes to the security subsystem could go undetected. The database could be severely compromised or rendered inoperative. To aid in diagnosis, it is necessary to track failed attempts in addition to the successful ones. Satisfies: SRG-APP-000496-DB-000334, SRG-APP-000496-DB-000335, SRG-APP-000501-DB-000336, SRG-APP-000501-DB-000337

For completeness of forensic analysis, it is necessary to track who/what (a user or other principal) logs on to SQL Server. It is also necessary to track failed attempts to log on to SQL Server. While positive identification may not be possible in a case of failed authentication, as much information as possible about the incident must be captured. Satisfies: SRG-APP-000503-DB-000350, SRG-APP-000503-DB-000351, SRG-APP-000506-DB-000353

In this context, direct access is any query, command, or call to SQL Server that comes from any source other than the application(s) that it supports. Examples would be the command line or a database management utility program. The intent is to capture all activity from administrative and nonstandard sources.

Information stored in one location is vulnerable to accidental or incidental deletion or alteration. Off-loading is a common process in information systems with limited audit storage capacity. The system SQL Server may write audit records to database tables, to files in the file system, to other kinds of local repository, or directly to a centralized log management system. Whatever the method used, it must be compatible with off-loading the records to the centralized system.

The SQL Server Browser simplifies the administration of SQL Server, particularly when multiple instances of SQL Server coexist on the same computer. It avoids the need to hard-assign port numbers to the instances and to set and maintain those port numbers in client systems. It enables administrators and authorized users to discover database management system instances, and the databases they support, over the network. SQL Server uses the SQL Server Browser service to enumerate instances of the Database Engine installed on the computer. This enables client applications to browse for a server, and helps clients distinguish between multiple instances of the Database Engine on the same computer. This convenience also presents the possibility of unauthorized individuals gaining knowledge of the available SQL Server resources. Therefore, it is necessary to consider whether the SQL Server Browser is needed. Typically, if only a single instance is installed, using the default name (MSSQLSERVER) and port assignment (1433), the Browser is not adding any value. The more complex the installation, the more likely SQL Server Browser is to be helpful. This requirement is not intended to prohibit use of the Browser service in any circumstances. It calls for administrators and management to consider whether the benefits of its use outweigh the potential negative consequences of it being used by an attacker to browse the current infrastructure and retrieve a list of running SQL Server instances.

By default, Microsoft SQL Server enables participation in the customer experience improvement program (CEIP). This program collects information about how its customers are using the product. Specifically, SQL Server collects information about the installation experience, feature usage, and performance. This information helps Microsoft improve the product to better meet customer needs. The Local Audit component of SQL Server Usage Feedback collection writes data collected by the service to a designated folder, representing the data (logs) that will be sent to Microsoft. The purpose of the Local Audit is to allow customers to view all data Microsoft collects with this feature, for compliance, regulatory or privacy validation reasons.

By default, Microsoft SQL Server enables participation in the customer experience improvement program (CEIP). This program collects information about how its customers are using the product. Specifically, SQL Server collects information about the installation experience, feature usage, and performance. This information helps Microsoft improve the product to better meet customer needs.

Password-based authentication applies to passwords regardless of whether they are used in single-factor or multifactor authentication. Long passwords or passphrases are preferable over shorter passwords. Enforced composition rules provide marginal security benefits while decreasing usability. However, organizations may choose to establish certain rules for password generation (e.g., minimum character length for long passwords) under certain circumstances and can enforce this requirement in IA-5(1)(h). Account recovery can occur, for example, in situations when a password is forgotten. Cryptographically protected passwords include salted one-way cryptographic hashes of passwords. The list of commonly used, compromised, or expected passwords includes passwords obtained from previous breach corpuses, dictionary words, and repetitive or sequential characters. The list includes context-specific words, such as the name of the service, username, and derivatives thereof.

SQL Server's [sa] account has special privileges required to administer the database. The [sa] account is a well-known SQL Server account and is likely to be targeted by attackers and thus more prone to providing unauthorized access to the database. This [sa] default account is administrative and could lead to catastrophic consequences, including the complete loss of control over SQL Server. If the [sa] default account is not disabled, an attacker might be able to gain access through the account. SQL Server by default disables the [sa] account at installation. Some applications that run on SQL Server require the [sa] account to be enabled for the application to function properly. These applications that require the [sa] account to be enabled are usually legacy systems.

SQL Server's [sa] account has special privileges required to administer the database. The [sa] account is a well-known SQL Server account name and is likely to be targeted by attackers, and is thus more prone to providing unauthorized access to the database. Since the SQL Server [sa] is administrative in nature, the compromise of a default account can have catastrophic consequences, including the complete loss of control over SQL Server. Since SQL Server needs for this account to exist and it should not be removed, one way to mitigate this risk is to change the [sa] account name.

In certain situations, to provide required functionality, a DBMS needs to execute internal logic (stored procedures, functions, triggers, etc.) and/or external code modules with elevated privileges. However, if the privileges required for execution are at a higher level than the privileges assigned to organizational users invoking the functionality applications/programs, those users are indirectly provided with greater privileges than assigned by organizations. When "Scan for startup procs" is enabled, SQL Server scans for and runs all automatically run stored procedures defined on the server. The execution of start-up stored procedures will be done under a high privileged context; therefore, it is a commonly used post-exploitation vector.

Information can be unintentionally or maliciously disclosed or modified during preparation for transmission, including, for example, during aggregation, at protocol transformation points, and during packing/unpacking. These unauthorized disclosures or modifications compromise the confidentiality or integrity of the information. Use of this requirement will be limited to situations where the data owner has a strict requirement for ensuring data integrity and confidentiality is maintained at every step of the data transfer and handling process. SQL Mirroring endpoints support different encryption algorithms, including no-encryption. Using a weak encryption algorithm or plaintext in communication protocols can lead to data loss, data manipulation, and/or connection hijacking.

Information can be unintentionally or maliciously disclosed or modified during preparation for transmission, including, for example, during aggregation, at protocol transformation points, and during packing/unpacking. These unauthorized disclosures or modifications compromise the confidentiality or integrity of the information. Use of this requirement will be limited to situations where the data owner has a strict requirement for ensuring that data integrity and confidentiality is maintained at every step of the data transfer and handling process. SQL Server Service Broker endpoints support different encryption algorithms, including no-encryption. Using a weak encryption algorithm or plaintext in communication protocols can lead to data loss, data manipulation, and/or connection hijacking.

Information systems are capable of providing a wide variety of functions and services. Some of the functions and services, provided by default, may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different operating system security context than SQL Server and provide unauthorized access to the host system. The registry contains sensitive information, including password hashes and clear text passwords. Registry extended stored procedures allow Microsoft SQL Server to access the machine's registry. The sensitivity of these procedures is exacerbated if Microsoft SQL Server is run under the Windows account LocalSystem. LocalSystem can read and write nearly all values in the registry, even those not accessible by the administrator. Unlike the xp_cmdshell extended stored procedure, which runs under a separate context if executed by a login not in the sysadmin role, the registry extended stored procedures always execute under the security context of the MSSQLServer service. Because the sensitive information is stored in the registry, it is essential that access to that information be properly guarded.

Information systems are capable of providing a wide variety of functions and services. Some of the functions and services, provided by default, may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. The most significant potential for attacking an instance is through the use of features that expose an external interface or ad hoc execution capability. FILESTREAM integrates the SQL Server Database Engine with an NTFS file system by storing varbinary(max) binary large object (BLOB) data as files on the file system. Transact-SQL statements can insert, update, query, search, and back up FILESTREAM data.

Information systems are capable of providing a wide variety of functions and services. Some of the functions and services, provided by default, may not be necessary to support essential organizational operations (e.g., key missions, functions). It is detrimental for applications to provide, or install by default, functionality exceeding requirements or mission objectives. Applications must adhere to the principles of least functionality by providing only essential capabilities. SQL Server may spawn additional external processes to execute procedures that are defined in the SQL Server but stored in external host files (external procedures). The spawned process used to execute the external procedure may operate within a different operating system security context than SQL Server and provide unauthorized access to the host system. SQL Server is capable of providing a wide range of features and services. Some of the features and services, provided by default, may not be necessary, and enabling them could adversely affect system security. The "Ole Automation Procedures" option controls whether OLE Automation objects can be instantiated within Transact-SQL batches. These are extended stored procedures that allow SQL Server users to execute functions external to SQL Server in the security context of SQL Server. The "Ole Automation Procedures" extended stored procedure allows execution of host executables outside the controls of database access permissions. This access may be exploited by malicious users who have compromised the integrity of the SQL Server database process to control the host operating system to perpetrate additional malicious activity.

SQL Server is capable of providing a wide range of features and services. Some of the features and services, provided by default, may not be necessary, and enabling them could adversely affect system security. The "user options" option specifies global defaults for all users. A list of default query processing options is established for the duration of a user's work session. The "user options" option enables changing the default values of the SET options (if the server's default settings are not appropriate).

Nonrepudiation of actions taken is required to maintain data integrity. Examples of particular actions taken by individuals include creating information, sending a message, approving information (e.g., indicating concurrence or signing a contract), and receiving a message. Nonrepudiation protects against later claims by a user of not having created, modified, or deleted a particular data item or collection of data in the database. In designing a database, the organization must define the types of data and the user actions that must be protected from repudiation. The implementation must then include building audit features into the application data tables and configuring SQL Server’s audit tools to capture the necessary audit trail. Design and implementation also must ensure that applications pass individual user identification to SQL Server, even where the application connects to the DBMS with a standard, shared account. If the computer account of a remote computer is granted access to a SQL Server database, any service or scheduled task running as NT AUTHORITY\SYSTEM or NT AUTHORITY\NETWORK SERVICE can log into the instance and perform actions. These actions cannot be traced back to a specific user or process.