From 33321b4c9e9307a6ec0f71e9fb2f391d4e7c5de2 Mon Sep 17 00:00:00 2001 From: Dru Lavigne Date: Thu, 7 Feb 2013 15:05:37 +0000 Subject: This patch addresses the following: - removes etc. and i.e. - fixes some title capitalization - fixes incorrect grammar and overuse of ; - fixes verb tense from future to active - fixes redundancy - general rewording to make a densely written dense subject slightly less dense - link added for trustedbsd website - spell out of acronyms introduced on first instance in section and used as acronym for all other instances - remove reference to trustedbsd mailing lists as these have only seen spam posts in past 6 years - reference to SEBSD was removed as does not exist - reference to deprecated lomac confusion removed - fix varname tags - note added that as of 8.x, MAC is in GENERIC Approved by: bcr (mentor) --- en_US.ISO8859-1/books/handbook/mac/chapter.xml | 1616 +++++++++++------------- 1 file changed, 725 insertions(+), 891 deletions(-) (limited to 'en_US.ISO8859-1/books/handbook/mac') diff --git a/en_US.ISO8859-1/books/handbook/mac/chapter.xml b/en_US.ISO8859-1/books/handbook/mac/chapter.xml index 6d95c5f8ca..38c622d0e3 100644 --- a/en_US.ISO8859-1/books/handbook/mac/chapter.xml +++ b/en_US.ISO8859-1/books/handbook/mac/chapter.xml @@ -27,44 +27,42 @@ &os; 5.X introduced new security extensions from the - TrustedBSD project based on the &posix;.1e draft. Two of the + TrustedBSD + Project based on the &posix;.1e draft. Two of the most significant new security mechanisms are file system Access Control Lists (ACLs) and Mandatory Access - Control (MAC) facilities. Mandatory Access - Control allows new access control modules to be loaded, - implementing new security policies. Some provide protections - of a narrow subset of the system, hardening a particular - service. Others provide comprehensive labeled security across - all subjects and objects. The mandatory part of the definition - comes from the fact that the enforcement of the controls is - done by administrators and the system, and is not left up to - the discretion of users as is done with discretionary access - control (DAC, the standard file and System - V IPC permissions on &os;). - - This chapter will focus on the - Mandatory Access Control Framework (MAC - Framework), and a set of pluggable security policy modules - enabling various security mechanisms. + Control (MAC) facilities. MAC allows new + access control modules to be loaded, implementing new security + policies. Some modules provide protections for a narrow subset + of the system, hardening a particular service. Others provide + comprehensive labeled security across all subjects and objects. + The mandatory part of the definition indicates that enforcement + of controls is performed by administrators and the operating + system. This is in contrast to the default security mechanism + of Discretionary Access Control (DAC where + enforcement is left to the discretion of users. + + This chapter focuses on the MAC framework + and the set of pluggable security policy modules &os; provides + for enabling various security mechanisms. After reading this chapter, you will know: - What MAC security policy modules - are currently included in &os; and their associated - mechanisms. + Which MAC security policy modules + are included in &os; and their associated mechanisms. - What MAC security policy modules - implement as well as the difference between a labeled and - non-labeled policy. + The capabilities of MAC security + policy modules as well as the difference between a labeled + and non-labeled policy. - How to efficiently configure a system to use - the MAC framework. + How to efficiently configure a system to use the + MAC framework. @@ -74,8 +72,7 @@ How to implement a more secure environment using the - MAC framework and the examples - shown. + MAC framework. @@ -93,12 +90,6 @@ (). - - Be familiar with - the basics of kernel configuration/compilation - (). - - Have some familiarity with security and how it pertains to &os; (). @@ -106,24 +97,21 @@ - The improper use of the - information contained herein may cause loss of system access, - aggravation of users, or inability to access the features - provided by X11. More importantly, MAC - should not be relied upon to completely secure a system. The - MAC framework only augments existing - security policy; without sound security practices and - regular security checks, the system will never be completely - secure. - - It should also be noted that the examples contained - within this chapter are just that, examples. It is not - recommended that these particular settings be rolled out - on a production system. Implementing the various security - policy modules takes a good deal of thought and testing. One - who does not fully understand exactly how everything works - may find him or herself going back through the entire system - and reconfiguring many files or directories. + Improper MAC configuration may cause + loss of system access, aggravation of users, or inability to + access the features provided by + Xorg. More importantly, + MAC should not be relied upon to completely + secure a system. The MAC framework only + augments an existing security policy. Without sound security + practices and regular security checks, the system will never + be completely secure. + + The examples contained within this chapter are for + demonstration purposes and the example settings should + not be implemented on a production + system. Implementing any security policy takes a good deal of + understanding, proper design, and thorough testing. @@ -135,10 +123,10 @@ modules will not be covered. A number of security policy modules included with the MAC framework have specific characteristics which are provided for both - testing and new module development. These include the + testing and new module development. These include &man.mac.test.4;, &man.mac.stub.4; and &man.mac.none.4;. For more information on these security policy modules and - the various mechanisms they provide, please review the manual + the various mechanisms they provide, refer to their manual pages. @@ -147,127 +135,117 @@ Key Terms in This Chapter Before reading this chapter, a few key terms must be - explained. This will hopefully clear up any confusion that - may occur and avoid the abrupt introduction of new terms - and information. + explained: - compartment: A compartment is a - set of programs and data to be partitioned or separated, - where users are given explicit access to specific components - of a system. Also, a compartment represents a grouping, - such as a work group, department, project, or topic. Using - compartments, it is possible to implement a need-to-know - security policy. + compartment: a set of programs and + data to be partitioned or separated, where users are given + explicit access to specific component of a system. A + compartment represents a grouping, such as a work group, + department, project, or topic. Compartments make it + possible to implement a need-to-know-basis security + policy. - high water mark: A high water mark - policy is one which permits the raising of security levels - for the purpose of accessing higher level information. In - most cases, the original level is restored after the process + high-watermark: this type of + policy permits the raising of security levels for the + purpose of accessing higher level information. In most + cases, the original level is restored after the process is complete. Currently, the &os; MAC - framework does not have a policy for this, but the - definition is included for completeness. + framework does not include this type of policy. - integrity: Integrity, as a key - concept, is the level of trust which can be placed on data. - As the integrity of the data is elevated, so does the - ability to trust that data. + integrity: the level of trust which + can be placed on data. As the integrity of the data is + elevated, so does the ability to trust that data. - label: A label is a security - attribute which can be applied to files, directories, or - other items in the system. It could be considered a - confidentiality stamp; when a label is placed on a file it - describes the security properties for that specific - file and will only permit access by files, users, resources, - etc. with a similar security setting. The meaning and - interpretation of label values depends on the policy - configuration: while some policies might treat a label as - representing the integrity or secrecy of an object, other - policies might use labels to hold rules for access. + label: a security attribute which + can be applied to files, directories, or other items in the + system. It could be considered a confidentiality stamp. + When a label is placed on a file, it describes the security + properties of that file and will only permit access by + files, users, and resources with a similar security setting. + The meaning and interpretation of label values depends on + the policy configuration. Some policies treat a label as + representing the integrity or secrecy of an object while + other policies might use labels to hold rules for + access. - level: The increased or decreased + level: the increased or decreased setting of a security attribute. As the level increases, its security is considered to elevate as well. - low water mark: A low water mark - policy is one which permits lowering of the security levels - for the purpose of accessing information which is less - secure. In most cases, the original security level of the - user is restored after the process is complete. The only - security policy module in &os; to use this is - &man.mac.lomac.4;. + low-watermark: this type of + policy permits lowering security levels for the purpose of + accessing information which is less secure. In most cases, + the original security level of the user is restored after + the process is complete. The only security policy module in + &os; to use this is &man.mac.lomac.4;. - multilabel: The - property is a file system option - which can be set in single user mode using the - &man.tunefs.8; utility, during the boot operation - using the &man.fstab.5; file, or during the creation of - a new file system. This option will permit an administrator - to apply different MAC labels on - different objects. This option only applies to security - policy modules which support labeling. + multilabel: this property is a file + system option which can be set in single user mode using + &man.tunefs.8;, during boot using &man.fstab.5;, or during + the creation of a new file system. This option permits + an administrator to apply different MAC + labels on different objects. This option only applies to + security policy modules which support labeling. - object: An object or system - object is an entity through which information flows - under the direction of a subject. - This includes directories, files, fields, screens, - keyboards, memory, magnetic storage, printers or any other - data storage/moving device. Basically, an object is a data - container or a system resource; access to an - object effectively means access to the - data. + object: an entity through which + information flows under the direction of a + subject. This includes directories, + files, fields, screens, keyboards, memory, magnetic storage, + printers or any other data storage or moving device. An + object is a data container or a system resource. Access to + an object effectively means access to + its data. - policy: A collection of rules + policy: a collection of rules which defines how objectives are to be achieved. A policy usually documents how certain - items are to be handled. This chapter will - consider the term policy in this - context as a security policy; i.e. - a collection of rules which will control the flow of data - and information and define whom will have access to that - data and information. + items are to be handled. This chapter considers the term + policy to be a security + policy, or a collection of rules which controls + the flow of data and information and defines who has access + to that data and information. - sensitivity: Usually used when - discussing MLS. A sensitivity level is - a term used to describe how important or secret the data + sensitivity: usually used when + discussing Multilevel Security MLS. A + sensitivity level describes how important or secret the data should be. As the sensitivity level increases, so does the - importance of the secrecy, or confidentiality of the + importance of the secrecy, or confidentiality, of the data. - single label: A single label is - when the entire file system uses one label to - enforce access control over the flow of data. When a file - system has this set, which is any time when the - option is not set, all - files will conform to the same label setting. + single label: a policy where the + entire file system uses one label to enforce access control + over the flow of data. Whenever + is not set, all files will conform to the same label + setting. - subject: a subject is any - active entity that causes information to flow between - objects; e.g., a user, user process, - system process, etc. On &os;, this is almost always a + subject: any active entity that + causes information to flow between + objects such as a user, user process, + or system process. On &os;, this is almost always a thread acting in a process on behalf of a user. @@ -280,99 +258,71 @@ MAC framework augments the security of the system as a whole. The various security policy modules provided by the MAC framework could be used - to protect the network and file systems, block users from - accessing certain ports and sockets, and more. Perhaps the - best use of the policy modules is to blend them together, by - loading several security policy modules at a time for a - multi-layered security environment. In a multi-layered security - environment, multiple policy modules are in effect to keep - security in check. This is different to a hardening policy, - which typically hardens elements of a system that is used only - for specific purposes. The only downside is administrative - overhead in cases of multiple file system labels, setting - network access control user by user, etc. - - These downsides are minimal when compared to the lasting - effect of the framework; for instance, the ability to pick - and choose which policies are required for a specific - configuration keeps performance overhead down. The reduction - of support for unneeded policies can increase the overall - performance of the system as well as offer flexibility of - choice. A good implementation would consider the overall - security requirements and effectively implement the various - security policy modules offered by the framework. - - Thus a system utilizing MAC features - should at least guarantee that a user will not be permitted - to change security attributes at will; all user utilities, - programs and scripts must work within the constraints of - the access rules provided by the selected security policy - modules; and that total control of the MAC - access rules are in the hands of the system - administrator. - - It is the sole duty of the system administrator to - carefully select the correct security policy modules. Some - environments may need to limit access control over the network; - in these cases, the &man.mac.portacl.4;, &man.mac.ifoff.4; and - even &man.mac.biba.4; policy modules might make good starting - points. In other cases, strict confidentiality of file system - objects might be required. Policy modules such as - &man.mac.bsdextended.4; and &man.mac.mls.4; exist for this - purpose. + to protect the network and file systems or to block users from + accessing certain ports and sockets. Perhaps the best use of + the policy modules is to load several security policy modules at + a time in order to provide a MLS environment. + This approach differs from a hardening policy, which typically + hardens elements of a system which are used only for specific + purposes. The downside to MLS is increased + administrative overhead. + + The overhead is minimal when compared to the lasting effect + of a framework which provides the ability to pick and choose + which policies are required for a specific configuration and + which keeps performance overhead down. The reduction of support + for unneeded policies can increase the overall performance of + the system as well as offer flexibility of choice. A good + implementation would consider the overall security requirements + and effectively implement the various security policy modules + offered by the framework. + + A system utilizing MAC guarantees that a + user will not be permitted to change security attributes at + will. All user utilities, programs, and scripts must work + within the constraints of the access rules provided by the + selected security policy modules and total control of the + MAC access rules are in the hands of the + system administrator. + + It is the duty of the system administrator to + carefully select the correct security policy modules. For an + environment that needs to limit access control over the network, + the &man.mac.portacl.4;, &man.mac.ifoff.4;, and &man.mac.biba.4; + policy modules make good starting points. For an environment + where strict confidentiality of file system objects is required, + consider the &man.mac.bsdextended.4; and &man.mac.mls.4; policy + modules. Policy decisions could be made based on network - configuration. Perhaps only certain users should be permitted - access to facilities provided by &man.ssh.1; to access the - network or the Internet. The &man.mac.portacl.4; would be - the policy module of choice for these situations. But what - should be done in the case of file systems? Should all access - to certain directories be severed from other groups or specific - users? Or should we limit user or utility access to specific - files by setting certain objects as classified? - - In the file system case, access to objects might be - considered confidential to some users, but not to others. - For an example, a large development team might be broken - off into smaller groups of individuals. Developers in - project A might not be permitted to access objects written - by developers in project B. Yet they might need to access - objects created by developers in project C; that is quite a - situation indeed. Using the different security policy modules - provided by the MAC framework; users could - be divided into these groups and then given access to the - appropriate areas without fear of information - leakage. - - Thus, each security policy module has a unique way of - dealing with the overall security of a system. Module selection - should be based on a well thought out security policy. In many - cases, the overall policy may need to be revised and - reimplemented on the system. Understanding the different + configuration. If only certain users should be permitted + access to &man.ssh.1;, the &man.mac.portacl.4; policy module is + a good choice. In the case of file systems, access to objects + might be considered confidential to some users, but not to + others. As an example, a large development team might be + broken off into smaller projects where developers in project A + might not be permitted to access objects written by developers + in project B. Yet both projects might need to access objects + created by developers in project C. Using the different + security policy modules provided by the MAC + framework, users could be divided into these groups and then + given access to the appropriate objects. + + Each security policy module has a unique way of dealing with + the overall security of a system. Module selection should be + based on a well thought out security policy which may require + revision and reimplementation. Understanding the different security policy modules offered by the MAC framework will help administrators choose the best policies for their situations. - The default &os; kernel does not include the option for - the MAC framework; thus the following - kernel option must be added before trying any of the examples or - information in this chapter: - - options MAC - - And the kernel will require a rebuild and a - reinstall. - - While the various manual pages for MAC - policy modules state that they may be built into the kernel, - it is possible to lock the system out of - the network and more. Implementing MAC - is much like implementing a firewall, care must be taken - to prevent being completely locked out of the system. The - ability to revert back to a previous configuration should be - considered while the implementation of MAC - remotely should be done with extreme caution. + Implementing MAC is much like + implementing a firewall, care must be taken to prevent being + completely locked out of the system. The ability to revert + back to a previous configuration should be considered and the + implementation of MAC remotely should be + done with extreme caution. @@ -383,65 +333,55 @@ which may be applied to subjects and objects throughout the system. - When setting a label, the user must be able to comprehend - what it is, exactly, that is being done. The attributes - available on an object depend on the policy module loaded, and - that policy modules interpret their attributes in different - ways. If improperly configured due to lack of comprehension, - or the inability to understand the implications, the result - will be the unexpected and perhaps, undesired, behavior of the - system. + When setting a label, the administrator must be able to + comprehend what exactly is being done and understand any + implications in order to prevent unexpected or undesired + behavior of the system. The attributes available on an object + depend on the loaded policy module as policy modules interpret + their attributes in different ways. The security label on an object is used as a part of a security access control decision by a policy. With some - policies, the label by itself contains all information necessary - to make a decision; in other models, the labels may be processed - as part of a larger rule set, etc. - - For instance, setting the label of - biba/low on a file will represent a label - maintained by the Biba security policy module, with a value - of low. + policies, the label contains all of the information necessary + to make a decision. In other policies, the labels may be + processed as part of a larger rule set. For instance, setting + the label of biba/low on a file will + represent a label maintained by the Biba security policy module, + with a value of low. A few policy modules which support the labeling feature - in &os; offer three specific predefined labels. These - are the low, high, and equal labels. Although they enforce - access control in a different manner with each policy module, - you can be sure that the low label will be the lowest setting, - the equal label will set the subject or object to be disabled - or unaffected, and the high label will enforce the highest - setting available in the Biba and MLS + in &os; offer three specific predefined labels: low, high, and + equal. Such policy modules enforce access control in a + different manner with each policy module, where the low label is + the lowest setting, the equal label sets the subject or object + to be disabled or unaffected, and the high label enforces the + highest setting available in the Biba and MLS policy modules. Within single label file system environments, only one - label may be used on objects. This will enforce one set of + label may be used on objects. This label enforces one set of access permissions across the entire system and in many environments may be all that is required. There are a few cases where multiple labels may be set on objects or subjects - in the file system. For those cases, the - option may be passed to + in the file system by passing to &man.tunefs.8;. In the case of Biba and MLS, a numeric label may be set to indicate the precise level of hierarchical control. This numeric level is used to partition or sort - information into different groups of say, classification only + information into different groups of classification only permitting access to that group or a higher group level. - In most cases the administrator will only be setting up a - single label to use throughout the file system. - - Hey wait, this is similar to - DAC! I thought MAC gave - control strictly to the administrator. That - statement still holds true, to some extent as + In most cases, the administrator will set up a single label + to use throughout the file system. This is similar to + DAC to some extent as root is the one in control and who configures the policies so that users are placed in the appropriate categories/access levels. Alas, many policy modules can restrict the root user as well. Basic control over objects will then be released to the group, but root may revoke or modify the settings - at any time. This is the hierarchal/clearance model covered + at any time. This is the hierarchical/clearance model covered by policies such as Biba and MLS. @@ -453,32 +393,29 @@ configuration or the manipulation and verification of the configuration. - All configuration may be done by use of the - &man.setfmac.8; and &man.setpmac.8; utilities. - The setfmac command is used to set - MAC labels on system objects while the - setpmac command is used to set the labels - on system subjects. Observe: + All configuration may be done using &man.setfmac.8; and + &man.setpmac.8;. setfmac is used to set + MAC labels on system objects while + setpmac is used to set the labels on system + subjects. Observe: &prompt.root; setfmac biba/high test - If no errors occurred with the command above, a prompt - will be returned. The only time these commands are not - quiescent is when an error occurred; similarly to the - &man.chmod.1; and &man.chown.8; commands. In some cases this - error may be a Permission denied and - is usually obtained when the label is being set or modified - on an object which is restricted.Other conditions - may produce different failures. For instance, the file may - not be owned by the user attempting to relabel the object, - the object may not exist or may be read only. A mandatory - policy will not allow the process to relabel the file, maybe + If the configuration is successful, the prompt will be + returned without error. A common error is + Permission denied which usually occurs + when the label is being set or modified on an object which is + restricted.Other conditions may produce different + failures. For instance, the file may not be owned by the + user attempting to relabel the object, the object may not + exist, or the object may be read only. A mandatory policy + will not allow the process to relabel the file, maybe because of a property of the file, a property of the process, or a property of the proposed new label value. For - example: a user running at low integrity tries to change the + example, a user running at low integrity tries to change the label of a high integrity file. Or perhaps a user running at low integrity tries to change the label of a low - integrity file to a high integrity label. The + integrity file to a high integrity label. The system administrator may use the following commands to overcome this: @@ -488,18 +425,16 @@ &prompt.root; getfmac test test: biba/high - As we see above, setpmac - can be used to override the policy module's settings by - assigning a different label to the invoked process. The - getpmac utility is usually used with - currently running processes, such as - sendmail: although it takes a - process ID in place of a command the logic is extremely - similar. If users attempt to manipulate a file not in their - access, subject to the rules of the loaded policy modules, - the Operation not permitted error - will be displayed by the mac_set_link - function. + setpmac can be used to override the + policy module's settings by assigning a different label to the + invoked process. getpmac is usually used + with currently running processes, such as + sendmail. It takes a process ID in + place of a command. If users attempt to manipulate a file not + in their access, subject to the rules of the loaded policy + modules, the Operation not permitted + error will be displayed by the + mac_set_link function. Common Label Types @@ -507,15 +442,14 @@ test: biba/high For the &man.mac.biba.4;, &man.mac.mls.4; and &man.mac.lomac.4; policy modules, the ability to assign simple labels is provided. These take the form of high, - equal and low, what follows is a brief description of - what these labels provide: + equal, and low, where: The low label is considered the lowest label setting an object or subject may have. - Setting this on objects or subjects will block their - access to objects or subjects marked high. + Setting this on objects or subjects blocks their access + to objects or subjects marked high. @@ -531,66 +465,62 @@ test: biba/high With respect to each policy module, each of those - settings will instate a different information flow - directive. Reading the proper manual pages will further - explain the traits of these generic label + settings will establish a different information flow + directive. Refer to the manual pages of the module to + determine the traits of these generic label configurations. Advanced Label Configuration Numeric grade labels are used for - comparison:compartment+compartment; - thus the following: + comparison:compartment+compartment. + For example: biba/10:2+3+6(5:2+3-20:2+3+4+5+6) - May be interpreted as: - - Biba Policy Label/Grade + may be interpreted as Biba Policy + Label/Grade 10:Compartments 2, 3 and 6: (grade 5 ...) In this example, the first grade would be considered the effective grade with effective compartments, the second grade - is the low grade and the last one is the high grade. - In most configurations these settings will not be used; - indeed, they offered for more advanced - configurations. + is the low grade, and the last one is the high grade. + In most configurations, these settings will not be used + as they are advanced configurations. - When applied to system objects, they will only have a - current grade/compartments as opposed to system subjects - as they reflect the range of available rights in the - system, and network interfaces, where they are used for - access control. + System objects only have a current grade/compartment. + System subjects reflect the range of available rights in + the system, and network interfaces, where they are used + for access control. The grade and compartments in a subject and object - pair are used to construct a relationship referred to as + pair are used to construct a relationship known as dominance, in which a subject dominates an object, the object dominates the subject, neither dominates the other, or both dominate each other. The both dominate case occurs when the two labels are equal. Due to the information flow nature of - Biba, you have rights to a set of compartments, - need to know, that might correspond to - projects, but objects also have a set of compartments. - Users may have to subset their rights using - su or setpmac in - order to access objects in a compartment from which they - are not restricted. + Biba, a user has rights to a set of compartments that + might correspond to projects, but objects also have a set + of compartments. Users may have to subset their rights + using su or setpmac + in order to access objects in a compartment from which + they are not restricted. Users and Label Settings - Users themselves are required to have labels so that - their files and processes may properly interact with the - security policy defined on the system. This is - configured through the login.conf file - by use of login classes. Every policy module that uses - labels will implement the user class setting. + Users are required to have labels so that their files + and processes properly interact with the security policy + defined on the system. This is configured in + login.conf using login classes. Every + policy module that uses labels will implement the user class + setting. An example entry containing every policy module setting is displayed below: @@ -619,49 +549,49 @@ test: biba/high :ignoretime@:\ :label=partition/13,mls/5,biba/10(5-15),lomac/10[2]: - The label option is used to set the + To set the user class default label which will be enforced by - MAC. Users will never be permitted to - modify this value, thus it can be considered not optional - in the user case. In a real configuration, however, the - administrator will never wish to enable every policy module. - It is recommended that the rest of this chapter be reviewed - before any of this configuration is implemented. + MAC, use . Users + are never permitted to modify this value. In a real + configuration, however, the administrator would never enable + every policy module. It is recommended that the rest of + this chapter be reviewed before any configuration is + implemented. - Users may change their label after the initial login; - however, this change is subject constraints of the policy. - The example above tells the Biba policy that a process's - minimum integrity is 5, its maximum is 15, but the default - effective label is 10. The process will run at 10 until - it chooses to change label, perhaps due to the user using - the setpmac command, which will be constrained by Biba to - the range set at login. + Users may change their label after they login, subject + to the constraints of the policy. The example above tells + the Biba policy that a process's minimum integrity is 5, + its maximum is 15, and the default effective label is 10. + The process will run at 10 until it chooses to change + label, perhaps due to the user using &man.setpmac.8;, + which will be constrained by Biba to the configured + range. - In all cases, after a change to + After any change to login.conf, the login class capability - database must be rebuilt using cap_mkdb - and this will be reflected throughout every forthcoming - example or discussion. - - It is useful to note that many sites may have a - particularly large number of users requiring several - different user classes. In depth planning is required - as this may get extremely difficult to manage. + database must be rebuilt using + cap_mkdb. + + Many sites have a large number of users requiring + several different user classes. In depth planning is + required as this may get extremely difficult to + manage. Network Interfaces and Label Settings - Labels may also be set on network interfaces to help - control the flow of data across the network. In all cases - they function in the same way the policies function with - respect to objects. Users at high settings in - biba, for example, will not be permitted - to access network interfaces with a label of low. + Labels may be set on network interfaces to help + control the flow of data across the network. Policies + using network interface labels function in the same way that + policies function with respect to objects. Users at high + settings in biba, for example, will not + be permitted to access network interfaces with a label of + low. - The may be passed to + may be passed to ifconfig when setting the MAC label on network interfaces. For example: @@ -671,51 +601,44 @@ test: biba/high will set the MAC label of biba/equal on the &man.bge.4; interface. When using a setting similar to - biba/high(low-high) the entire label - should be quoted; otherwise an error will be + biba/high(low-high), the entire label + should be quoted to prevent an error from being returned. Each policy module which supports labeling has a tunable which may be used to disable the MAC label on network interfaces. Setting the label to will have a similar effect. Review - the output from sysctl, the policy manual - pages, or even the information found later in this chapter - for those tunables. + the output of sysctl, the policy manual + pages, and the information in this chapter for more + information on those tunables. Singlelabel or Multilabel? - By default the system will use the - option. But what does this - mean to the administrator? There are several differences - which, in their own right, offer pros and cons to the - flexibility in the systems security model. - - The only permits for one - label, for instance biba/high to be used - for each subject or object. It provides for lower - administration overhead but decreases the flexibility of - policies which support labeling. Many administrators may - want to use the option in - their security policy. - - The option will permit each - subject or object to have its own independent - MAC label in - place of the standard option - which will allow only one label throughout the partition. - The and - label options are only required for the policies which - implement the labeling feature, including the Biba, Lomac, - MLS and SEBSD - policies. + By default, the system will use + . For the administrator, there + are several differences which offer pros and cons to the + flexibility in the system's security model. - In many cases, the may not - need to be set at all. Consider the following situation and - security model: + A security policy which uses + only permits one label, such as biba/high, + to be used for each subject or object. This provides lower + administration overhead, but decreases the flexibility of + policies which support labeling. + + permits each subject or object + to have its own independent MAC label. + The decision to use or + is only required for the policies + which implement the labeling feature, including the Biba, + Lomac, and MLS policies. + + In many cases, may not be + needed. Consider the following situation and security + model: @@ -726,49 +649,41 @@ test: biba/high This machine only requires one label, biba/high, for everything in the - system. Here the file system would not require the - option as a single label - will always be in effect. + system. This file system would not require + as a single label will always + be in effect. But, this machine will be a web server and should have the web server run at biba/low - to prevent write up capabilities. The Biba policy and - how it works will be discussed later, so if the previous - comment was difficult to interpret just continue reading - and return. The server could use a separate partition - set at biba/low for most if not all - of its runtime state. Much is lacking from this example, - for instance the restrictions on data, configuration and - user settings; however, this is just a quick example to - prove the aforementioned point. + to prevent write up capabilities. The server could + use a separate partition set at + biba/low for most if not all + of its runtime state. If any of the non-labeling policies are to be used, - then the option would never - be required. These include the - seeotheruids, portacl - and partition policies. - - It should also be noted that using - with a partition and establishing - a security model based on - functionality could open the doors for higher administrative - overhead as everything in the file system would have a label. - This includes directories, files, and even device + would not be required. These + include the seeotheruids, + portacl and partition + policies. + + Using with a partition and + establishing a security model based on + functionality could increase + administrative overhead as everything in the file system has a + label. This includes directories, files, and even device nodes. The following command will set on the file systems to have multiple labels. This may only be - done in single user mode: + done in single user mode and is not a requirement for the swap + file system: &prompt.root; tunefs -l enable / - This is not a requirement for the swap file - system. - Some users have experienced problems with setting the flag on the root partition. @@ -782,20 +697,9 @@ test: biba/high Planning the Security Configuration Whenever a new technology is implemented, a planning phase - is always a good idea. During the planning stages, an - administrator should in general look at the big - picture, trying to keep in view at least the - following: - - - - The implementation requirements; - - - - The implementation goals; - - + is recommended. During the planning stages, an administrator + should consider the implementation requirements and the + implementation goals. For MAC installations, these include: @@ -807,8 +711,8 @@ test: biba/high - What sorts of information or resources to restrict - access to along with the type of restrictions that should be + Which information or resources to restrict access to + along with the type of restrictions that should be applied. @@ -818,60 +722,54 @@ test: biba/high - It is always possible to reconfigure and change the - system resources and security settings, it is quite often very - inconvenient to search through the system and fix existing - files and user accounts. Planning helps to ensure a - trouble-free and efficient trusted system implementation. A - trial run of the trusted system, including the configuration, - is often vital and definitely beneficial + Good planning helps to ensure a trouble-free and efficient + trusted system implementation. A trial run of the trusted + system and its configuration should occur before a MAC implementation is used on production systems. The idea of just letting loose on a system with MAC is like setting up for failure. - Different environments may have explicit needs and + Different environments have different needs and requirements. Establishing an in depth and complete security profile will decrease the need of changes once the system - goes live. As such, the future sections will cover the - different modules available to administrators; describe their - use and configuration; and in some cases provide insight on - what situations they would be most suitable for. For instance, - a web server might roll out the &man.mac.biba.4; and - &man.mac.bsdextended.4; policies. In other cases, a machine - with very few local users, the &man.mac.partition.4; might - be a good choice. + goes live. The rest of this chapter covers the available + modules, describes their use and configuration, and in some + cases, provides insight on applicable situations. For instance, + a web server might use the &man.mac.biba.4; and + &man.mac.bsdextended.4; policies. In the case of a machine + with few local users, &man.mac.partition.4; might be a good + choice. Module Configuration - Every module included with the MAC - framework may be either compiled into the kernel as noted above - or loaded as a run-time kernel module. - The recommended method is to add the module name to the - /boot/loader.conf file so that it will load - during the initial boot operation. - - The following sections will discuss the various - MAC modules and cover their features. - Implementing them into a specific environment will also - be a consideration of this chapter. Some modules support - the use of labeling, which is controlling access by enforcing - a label such as this is allowed and this is not. - A label configuration file may control how files may be - accessed, network communication can be exchanged, and more. - The previous section showed how the - flag could be set on file systems to enable per-file or - per-partition access control. - - A single label configuration would enforce only one label + Beginning with &os; 8.0, the default &os; kernel + includes options MAC. This means that + every module included with the MAC + framework may be loaded as a run-time kernel module. The + recommended method is to add the module name to + /boot/loader.conf so that it will load + during boot. Each module also provides a kernel option + for those administrators who choose to compile their own + custom kernel. + + Some modules support the use of labeling, which is + controlling access by enforcing a label such as this is + allowed and this is not. A label configuration file may + control how files may be accessed, network communication can be + exchanged, and more. The previous section showed how the + flag could be set on file systems to + enable per-file or per-partition access control. + + A single label configuration enforces only one label across the system, that is why the tunefs option is called . - The MAC seeotheruids Module + The &man.mac.seeotheruids.4; Module MAC See Other UIDs Policy @@ -885,8 +783,8 @@ test: biba/high mac_seeotheruids_load="YES" The &man.mac.seeotheruids.4; module mimics and extends - the security.bsd.see_other_uids and - security.bsd.see_other_gids + the security.bsd.see_other_uids and + security.bsd.see_other_gids sysctl tunables. This option does not require any labels to be set before configuration and can operate transparently with the other modules. @@ -897,37 +795,36 @@ test: biba/high - security.mac.seeotheruids.enabled - will enable the module's features and use the default - settings. These default settings will deny users the - ability to view processes and sockets owned by other - users. + security.mac.seeotheruids.enabled + enables the module and uses the default settings which deny + users the ability to view processes and sockets owned by + other users. - security.mac.seeotheruids.specificgid_enabled - will allow a certain group to be exempt from this policy. - To exempt specific groups from this policy, use the - security.mac.seeotheruids.specificgid=XXX - sysctl tunable. In the above example, - the XXX should be replaced with - the numeric group ID to be exempted. + security.mac.seeotheruids.specificgid_enabled + allows certain groups to be exempt from this policy. To + exempt specific groups from this policy, use the + security.mac.seeotheruids.specificgid=XXX + sysctl tunable. Replace + XXX with the numeric group ID to + be exempted. - security.mac.seeotheruids.primarygroup_enabled + security.mac.seeotheruids.primarygroup_enabled is used to exempt specific primary groups from this policy. - When using this tunable, the - security.mac.seeotheruids.specificgid_enabled + When using this tunable, + security.mac.seeotheruids.specificgid_enabled may not be set. - The MAC bsdextended Module + The &man.mac.bsdextended.4; Module MAC @@ -950,18 +847,17 @@ test: biba/high rules is iterated until either a matching rule is located or the end is reached. This behavior may be changed by the use of a &man.sysctl.8; parameter, - security.mac.bsdextended.firstmatch_enabled. Similar to - other firewall modules in &os;, a file containing access - control rules can be created and read by the system at boot - time using an &man.rc.conf.5; variable. + security.mac.bsdextended.firstmatch_enabled. + Similar to other firewall modules in &os;, a file containing + the access control rules can be created and read by the system + at boot time using an &man.rc.conf.5; variable. - The rule list may be entered using a utility, - &man.ugidfw.8;, that has a syntax similar to that of - &man.ipfw.8;. More tools can be written by using the functions - in the &man.libugidfw.3; library. + The rule list may be entered using &man.ugidfw.8; which has + a syntax similar to &man.ipfw.8;. More tools can be written by + using the functions in the &man.libugidfw.3; library. Extreme caution should be taken when working with this - module; incorrect use could block access to certain parts of + module as incorrect use could block access to certain parts of the file system. @@ -974,48 +870,41 @@ test: biba/high &prompt.root; ugidfw list 0 slots, 0 rules - As expected, there are no rules defined. This means that - everything is still completely accessible. To create a rule - which will block all access by users but leave - root unaffected, simply run the - following command: + By default, no rules are defined and everything is + completely accessible. To create a rule which will block all + access by users but leave root + unaffected, run the following command: &prompt.root; ugidfw add subject not uid root new object not uid root mode n This is a very bad idea as it will block all users from issuing even the most simple commands, such as - ls. A more patriotic list of rules - might be: + ls. The next example will block + user1 any and all access, including + directory listings, to + user2's home + directory: &prompt.root; ugidfw set 2 subject uid user1 object uid user2 mode n &prompt.root; ugidfw set 3 subject uid user1 object gid user2 mode n - This will block any and all access, including directory - listings, to - user2's home - directory from the username user1. - - In place of user1, the + Instead of user1, - could be passed. This will enforce the same access - restrictions above for all users in place of just one - user. + could be used. This enforces the same access restrictions for + all users instead of just one user. - The root user will be unaffected - by these changes. + The root user is unaffected by + these changes. - This should provide a general idea of how the - &man.mac.bsdextended.4; module may be used to help fortify - a file system. For more information, see the - &man.mac.bsdextended.4; and the &man.ugidfw.8; manual - pages. + For more information, refer to &man.mac.bsdextended.4; and + &man.ugidfw.8; - The MAC ifoff Module + The &man.mac.ifoff.4; Module MAC Interface Silencing Policy @@ -1025,33 +914,34 @@ test: biba/high Kernel configuration line: options MAC_IFOFF - Boot option: mac_ifoff_load="YES" + Boot option: + mac_ifoff_load="YES" The &man.mac.ifoff.4; module exists solely to disable network interfaces on the fly and keep network interfaces from - being brought up during the initial system boot. It does not - require any labels to be set up on the system, nor does it have - a dependency on other MAC modules. + being brought up during system boot. It does not require any + labels to be set up on the system, nor does it depend on other + MAC modules. - Most of the control is done through the + Most of this module's control is performed through the sysctl tunables listed below. - security.mac.ifoff.lo_enabled will - enable/disable all traffic on the loopback (&man.lo.4;) + security.mac.ifoff.lo_enabled + enables or disables all traffic on the loopback (&man.lo.4;) interface. - security.mac.ifoff.bpfrecv_enabled - will enable/disable all traffic on the Berkeley Packet + security.mac.ifoff.bpfrecv_enabled + enables or disables all traffic on the Berkeley Packet Filter interface (&man.bpf.4;) - security.mac.ifoff.other_enabled will - enable/disable traffic on all other interfaces. + security.mac.ifoff.other_enabled + enables or disables traffic on all other interfaces. @@ -1065,7 +955,7 @@ test: biba/high - The MAC portacl Module + The &man.mac.portacl.4; Module MAC Port Access Control List Policy @@ -1080,119 +970,106 @@ test: biba/high The &man.mac.portacl.4; module is used to limit binding to local TCP and UDP ports - using a variety of sysctl variables. In - essence &man.mac.portacl.4; makes it possible to allow + using a variety of sysctl variables. + &man.mac.portacl.4; makes it possible to allow non-root users to bind to specified - privileged ports, i.e., ports below 1024. + privileged ports below 1024. - Once loaded, this module will enable the + Once loaded, this module enables the MAC policy on all sockets. The following tunables are available: - security.mac.portacl.enabled will - enable/disable the policy completely. + security.mac.portacl.enabled + enables or disables the policy completely. - security.mac.portacl.port_high will - set the highest port number that &man.mac.portacl.4; - will enable protection for. + security.mac.portacl.port_high + sets the highest port number that &man.mac.portacl.4; + protects. - security.mac.portacl.suser_exempt - will, when set to a non-zero value, exempt the + security.mac.portacl.suser_exempt, + when set to a non-zero value, exempts the root user from this policy. - security.mac.portacl.rules will - specify the actual mac_portacl policy; see below. + security.mac.portacl.rules + specifies the mac_portacl policy, which is a text string of + the form: rule[,rule,...] with as many + rules as needed. Each rule is of the form: + idtype:id:protocol:port. The + idtype parameter can be + uid or gid and is used + to interpret the id parameter as + either a user id or group id, respectively. The + protocol parameter is used to + determine if the rule should apply to TCP + or UDP by setting the parameter to + tcp or udp. The final + port parameter is the port number to + allow the specified user or group to bind to. - The actual mac_portacl policy, as - specified in the security.mac.portacl.rules - sysctl, is a text string of the form: - rule[,rule,...] with as many rules as - needed. Each rule is of the form: - idtype:id:protocol:port. The - idtype parameter can be - uid or gid and used to - interpret the id parameter as either a - user id or group id, respectively. The - protocol parameter is used to determine - if the rule should apply to TCP or - UDP by setting the parameter to - tcp or udp. The final - port parameter is the port number to - allow the specified user or group to bind to. - - Since the ruleset is interpreted directly by the kernel + Since the ruleset is interpreted directly by the kernel, only numeric values can be used for the user ID, group ID, - and port parameters. Names cannot be used for users, groups, - or services. + and port parameters. Names cannot be used for users, + groups, or services. - By default, on &unix;-like systems, ports below 1024 - can only be used by/bound to privileged processes, - i.e., those run as root. For - &man.mac.portacl.4; to allow non-privileged processes to bind - to ports below 1024 this standard &unix; restriction has to - be disabled. This can be accomplished by setting the - &man.sysctl.8; variables - net.inet.ip.portrange.reservedlow and - net.inet.ip.portrange.reservedhigh - to zero. + By default, ports below 1024 can only be used by or bound + to privileged processes, which run as + root. For &man.mac.portacl.4; to allow + non-privileged processes to bind to ports below 1024, this + restriction has to be disabled by setting the &man.sysctl.8; + variables + net.inet.ip.portrange.reservedlow and + net.inet.ip.portrange.reservedhigh to + zero: + + &prompt.root; sysctl security.mac.portacl.port_high=1023 +&prompt.root; sysctl net.inet.ip.portrange.reservedlow=0 +net.inet.ip.portrange.reservedhigh=0 - See the examples below or review the &man.mac.portacl.4; - manual page for further information. + See the examples below or refer to &man.mac.portacl.4; for + further information. Examples - The following examples should illuminate the above - discussion a little better: - - &prompt.root; sysctl security.mac.portacl.port_high=1023 -&prompt.root; sysctl net.inet.ip.portrange.reservedlow=0 net.inet.ip.portrange.reservedhigh=0 - - First we set &man.mac.portacl.4; to cover the standard - privileged ports and disable the normal &unix; bind - restrictions. + Since the root user should not be + crippled by this policy, this example starts by setting the + security.mac.portacl.suser_exempt to a + non-zero value. &prompt.root; sysctl security.mac.portacl.suser_exempt=1 - The root user should not be crippled - by this policy, thus set the - security.mac.portacl.suser_exempt to a - non-zero value. The &man.mac.portacl.4; module - has now been set up to behave the same way &unix;-like systems - behave by default. + Next, allow the user with UID 80 + to bind to port 80. This allows the www + user to run a web server without ever having + root privilege. &prompt.root; sysctl security.mac.portacl.rules=uid:80:tcp:80 - Allow the user with UID 80 (normally - the www user) to bind to port 80. - This can be used to allow the www - user to run a web server without ever having - root privilege. + The next example permits the user with the + UID of 1001 to bind to the + TCP ports 110 (pop3) and 995 + (pop3s). This permits this user to start a + server that accepts connections on ports 110 and 995. &prompt.root; sysctl security.mac.portacl.rules=uid:1001:tcp:110,uid:1001:tcp:995 - Permit the user with the UID of - 1001 to bind to the TCP ports 110 - (pop3) and 995 (pop3s). - This will permit this user to start a server that accepts - connections on ports 110 and 995. - The MAC partition Module + The &man.mac.partition.4; Module MAC Process Partition Policy @@ -1207,23 +1084,18 @@ test: biba/high The &man.mac.partition.4; policy will drop processes into specific partitions based on their - MAC label. Think of it as a special - type of &man.jail.8;, though that is hardly a worthy - comparison. - - This is one module that should be added to the - &man.loader.conf.5; file so that it loads - and enables the policy during the boot process. + MAC label. This module should be added to + &man.loader.conf.5; so that it loads and enables the policy + at system boot. Most configuration for this policy is done using - the &man.setpmac.8; utility which will be explained below. - The following sysctl tunable is + &man.setpmac.8;. One sysctl tunable is available for this policy: - security.mac.partition.enabled will - enable the enforcement of MAC process + security.mac.partition.enabled + enables the enforcement of MAC process partitions. @@ -1232,32 +1104,30 @@ test: biba/high to see their processes, and any others within their partition, but will not be permitted to work with utilities outside the scope of this partition. For instance, a user in the - insecure class above will not be permitted - to access the top command as well as many - other commands that must spawn a process. + insecure class will not be permitted to + access top as well as many other commands + that must spawn a process. To set or drop utilities into a partition label, use the setpmac utility: &prompt.root; setpmac partition/13 top - This will add the top command to the - label set on users in the insecure class. - Note that all processes spawned by users - in the insecure class will stay in the - partition/13 label. + This example adds top to the label set on + users in the insecure class. All processes + spawned by users in the insecure class will + stay in the partition/13 label. Examples - The following command will show you the partition label + The following command will display the partition label and the process list: &prompt.root; ps Zax - This next command will allow the viewing of another - user's process partition label and that user's currently - running processes: + This command will display another user's process partition + label and that user's currently running processes: &prompt.root; ps -ZU trhodes @@ -1299,13 +1169,13 @@ test: biba/high flow policy. In MLS environments, a - clearance level is set in each subject or objects - label, along with compartments. Since these clearance or - sensibility levels can reach numbers greater than six thousand; - it would be a daunting task for any system administrator to - thoroughly configure each subject or object. Thankfully, three - instant labels are already included in this - policy. + clearance level is set in the label of each + subject or object, along with compartments. Since these + clearance or sensibility levels can reach numbers greater than + several thousand; it would be a daunting task for any system + administrator to thoroughly configure each subject or object. + Thankfully, three instant labels are included in + this policy. These labels are mls/low, mls/equal and mls/high. @@ -1318,9 +1188,9 @@ test: biba/high configuration which permits it to be dominated by all other objects. Anything labeled with mls/low will have a low clearance level and not be permitted to - access information of a higher level. In addition, this - label will prevent objects of a higher clearance level from - writing or passing information on to them. + access information of a higher level. This label also + prevents objects of a higher clearance level from writing or + passing information on to them. @@ -1338,30 +1208,31 @@ test: biba/high - MLS provides for: + MLS provides: A hierarchical security level with a set of non - hierarchical categories; + hierarchical categories. - Fixed rules: no read up, no write down (a subject can - have read access to objects on its own level or below, but - not above. Similarly, a subject can have write access to - objects on its own level or above but not beneath.); + Fixed rules of no read up, no write + down. This means that a subject can have read + access to objects on its own level or below, but not above. + Similarly, a subject can have write access to objects on its + own level or above but not beneath. - Secrecy (preventing inappropriate disclosure - of data); + Secrecy, or the prevention of inappropriate disclosure + of data. - Basis for the design of systems that concurrently handle - data at multiple sensitivity levels (without leaking - information between secret and confidential). + A basis for the design of systems that concurrently + handle data at multiple sensitivity levels without leaking + information between secret and confidential. @@ -1371,77 +1242,71 @@ test: biba/high - security.mac.mls.enabled is used to - enable/disable the MLS policy. + security.mac.mls.enabled is used to + enable or disable the MLS policy. - security.mac.mls.ptys_equal will - label all &man.pty.4; devices as + security.mac.mls.ptys_equal + labels all &man.pty.4; devices as mls/equal during creation. - security.mac.mls.revocation_enabled - is used to revoke access to objects after their label - changes to a label of a lower grade. + security.mac.mls.revocation_enabled + revokes access to objects after their label changes to a + label of a lower grade. - security.mac.mls.max_compartments - is used to set the maximum number of compartment levels - with objects; basically the maximum compartment number - allowed on a system. + security.mac.mls.max_compartments + sets the maximum number of compartment levels allowed on a + system. - To manipulate the MLS labels, the - &man.setfmac.8; command has been provided. To assign a label - to an object, issue the following command: + To manipulate the MLS labels, use + &man.setfmac.8;. To assign a label to an object, issue the + following command: &prompt.root; setfmac mls/5 test To get the MLS label for the file - test issue the following command: + test, issue the following command: &prompt.root; getfmac test - This is a summary of the MLS - policy's features. Another approach is to create a master - policy file in /etc - which specifies the MLS policy information - and to feed that file into the setfmac - command. This method will be explained after all policies are - covered. + Another approach is to create a master policy file in + /etc/ which specifies the + MLS policy information and to feed that file + to setfmac. This method will be explained + after all policies are covered. Planning Mandatory Sensitivity - With the Multi-Level Security Policy Module, an - administrator plans for controlling the flow of sensitive - information. By default, with its block read up block write - down nature, the system defaults everything to a low state. - Everything is accessible and an administrator - slowly changes this during the configuration stage; augmenting - the confidentiality of the information. - - Beyond the three basic label options above, an - administrator may group users and groups as required to block - the information flow between them. It might be easier to - look at the information in clearance levels familiarized with - words, for instance classifications such as - Confidential, Secret, - and Top Secret. Some administrators might - just create different groups based on project levels. - Regardless of classification method, a well thought out plan - must exist before implementing such a restrictive - policy. - - Some example situations for this security policy module - could be an e-commerce web server, a file server holding + When using the MLS policy module, an administrator plans + to control the flow of sensitive information. The default + block read up block write down sets + everything to a low state. Everything is accessible and an + administrator slowly augments the confidentiality of the + information during the configuration stage;. + + Beyond the three basic label options, an administrator may + group users and groups as required to block the information + flow between them. It might be easier to look at the + information in clearance levels using descriptive words, such + as classifications of Confidential, + Secret, and Top Secret. + Some administrators instead create different groups based on + project levels. Regardless of the classification method, a + well thought out plan must exist before implementing such a + restrictive policy. + + Some example situations for the MLS policy module + include an e-commerce web server, a file server holding critical company information, and financial institution - environments. The most unlikely place would be a personal - workstation with only two or three users. + environments. @@ -1453,25 +1318,24 @@ test: biba/high Module name: mac_biba.ko - Kernel configuration line: - options MAC_BIBA + Kernel configuration line: options + MAC_BIBA Boot option: mac_biba_load="YES" The &man.mac.biba.4; module loads the MAC - Biba policy. This policy works much like that of the + Biba policy. This policy is similar to the MLS policy with the exception that the rules - for information flow - are slightly reversed. This is said to prevent the downward - flow of sensitive information whereas the MLS - policy prevents the upward flow of sensitive information; thus, - much of this section can apply to both policies. + for information flow are slightly reversed. This is to prevent + the downward flow of sensitive information whereas the + MLS policy prevents the upward flow of + sensitive information. Much of this section can apply to both + policies. In Biba environments, an integrity label is set on each subject or object. These labels are made up of - hierarchal grades, and non-hierarchal components. As an - object's or subject's grade ascends, so does its - integrity. + hierarchical grades and non-hierarchical components. As an + grade ascends, so does its integrity. Supported labels are biba/low, biba/equal, and biba/high; @@ -1501,59 +1365,60 @@ test: biba/high - Biba provides for: + Biba provides: Hierarchical integrity level with a set of non - hierarchical integrity categories; + hierarchical integrity categories. - Fixed rules: no write up, no read down (opposite of - MLS). A subject can have write access + Fixed rules are no write up, no read + down, the opposite of + MLS. A subject can have write access to objects on its own level or below, but not above. Similarly, a subject can have read access to objects on - its own level or above, but not below; + its own level or above, but not below. - Integrity (preventing inappropriate modification of - data); + Integrity by preventing inappropriate modification of + data. - Integrity levels (instead of MLS sensitivity - levels). + Integrity levels instead of MLS sensitivity + levels. The following sysctl tunables can - be used to manipulate the Biba policy. + be used to manipulate the Biba policy: - security.mac.biba.enabled may be used - to enable/disable enforcement of the Biba policy on the + security.mac.biba.enabled is used + to enable or disable enforcement of the Biba policy on the target machine. - security.mac.biba.ptys_equal may be + security.mac.biba.ptys_equal is used to disable the Biba policy on &man.pty.4; devices. - security.mac.biba.revocation_enabled - will force the revocation of access to objects if the label + security.mac.biba.revocation_enabled + forces the revocation of access to objects if the label is changed to dominate the subject. To access the Biba policy setting on system objects, use - the setfmac and getfmac - commands: + setfmac and + getfmac: &prompt.root; setfmac biba/low test &prompt.root; getfmac test @@ -1562,44 +1427,41 @@ test: biba/low Planning Mandatory Integrity - Integrity, different from sensitivity, guarantees that the - information will never be manipulated by untrusted parties. - This includes information passed between subjects, objects, - and both. It ensures that users will only be able to modify - and in some cases even access information they explicitly need - to. + Integrity, which is different from sensitivity, guarantees + that the information will never be manipulated by untrusted + parties. This includes information passed between subjects, + objects, and both. It ensures that users will only be able to + modify or access information they explicitly need to. The &man.mac.biba.4; security policy module permits an - administrator to address which files and programs a user or - users may see and invoke while assuring that the programs and - files are free from threats and trusted by the system for that - user, or group of users. + administrator to address which files and programs a user may + see and invoke while assuring that the programs and files are + free from threats and trusted by the system for that + user. During the initial planning phase, an administrator must be prepared to partition users into grades, levels, and areas. - Users will be blocked access not only to data but programs + Users will be blocked access not only to data but to programs and utilities both before and after they start. The system will default to a high label once this policy module is enabled, and it is up to the administrator to configure the different grades and levels for users. Instead of using - clearance levels as described above, a good planning method - could include topics. For instance, only allow developers - modification access to the source code repository, source - code compiler, and other development utilities. While other - users would be grouped into other categories such as testers, - designers, or just ordinary users and would only be permitted - read access. - - With its natural security control, a lower integrity - subject is unable to write to a higher integrity subject; a - higher integrity subject cannot observe or read a lower - integrity object. Setting a label at the lowest possible - grade could make it inaccessible to subjects. Some - prospective environments for this security policy module - would include a constrained web server, development and test - machine, and source code repository. A less useful - implementation would be a personal workstation, a machine - used as a router, or a network firewall. + clearance levels, a good planning method could include topics. + For instance, only allow developers modification access to the + source code repository, source code compiler, and other + development utilities. Other users would be grouped into + other categories such as testers, designers, or end users and + would only be permitted read access. + + A lower integrity subject is unable to write to a higher + integrity subject and a higher integrity subject cannot + observe or read a lower integrity object. Setting a label at + the lowest possible grade could make it inaccessible to + subjects. Some prospective environments for this security + policy module would include a constrained web server, a + development and test machine, and a source code repository. A + less useful implementation would be a personal workstation, a + machine used as a router, or a network firewall. @@ -1611,8 +1473,9 @@ test: biba/low Module name: mac_lomac.ko - Kernel configuration line: - options MAC_LOMAC + Kernel configuration line: options + MAC_LOMAC + Boot option: mac_lomac_load="YES" Unlike the MAC Biba policy, the @@ -1621,13 +1484,11 @@ test: biba/low any integrity rules. The MAC version of the Low-watermark - integrity policy, not to be confused with the older - &man.lomac.4; implementation, works almost identically to Biba, - but with the exception of using floating labels to support - subject demotion via an auxiliary grade compartment. This - secondary compartment takes the form of - [auxgrade]. When assigning a lomac policy - with an auxiliary grade, it should look a little bit like: + integrity policy works almost identically to Biba, but with the + exception of using floating labels to support subject demotion + via an auxiliary grade compartment. This secondary compartment + takes the form [auxgrade]. When assigning + a LOMAC policy with an auxiliary grade, use the syntax lomac/10[2] where the number two (2) is the auxiliary grade. @@ -1635,25 +1496,23 @@ test: biba/low ubiquitous labeling of all system objects with integrity labels, permitting subjects to read from low integrity objects and then downgrading the label on the subject to prevent future writes to - high integrity objects. This is the - [auxgrade] option discussed above, thus the + high integrity objects using [auxgrade]. The policy may provide for greater compatibility and require less initial configuration than Biba. Examples - Like the Biba and MLS policies; - the setfmac and setpmac - utilities may be used to place labels on system - objects: + Like the Biba and MLS policies, + setfmac and setpmac + are used to place labels on system objects: &prompt.root; setfmac /usr/home/trhodes lomac/high[low] &prompt.root; getfmac /usr/home/trhodes lomac/high[low] - Notice the auxiliary grade here is low, - this is a feature provided only by the MAC - LOMAC policy. + The auxiliary grade low is a feature + provided only by the MAC LOMAC + policy. @@ -1664,28 +1523,25 @@ test: biba/low Nagios in a MAC Jail - The following demonstration will implement a secure + The following demonstration implements a secure environment using various MAC modules - with properly configured policies. This is only a test and - should not be considered the complete answer to everyone's - security woes. Just implementing a policy and ignoring it - never works and could be disastrous in a production - environment. - - Before beginning this process, the - multilabel option must be set on each file - system as stated at the beginning of this chapter. Not doing - so will result in errors. While at it, ensure that the - net-mngt/nagios-plugins, + with properly configured policies. This is only a test as + implementing a policy and ignoring it could be disastrous in a + production environment. + + Before beginning this process, + must be set on each file system as not doing so will result in + errors. This example assumes that net-mngt/nagios-plugins, net-mngt/nagios, and - www/apache22 ports are all + www/apache22 are all installed, configured, and working correctly. - Create an insecure User Class + Create an Insecure User Class Begin the procedure by adding the following user class - to the /etc/login.conf file: + to /etc/login.conf: insecure:\ :copyright=/etc/COPYRIGHT:\ @@ -1711,13 +1567,12 @@ test: biba/low :ignoretime@:\ :label=biba/10(10-10): - And adding the following line to the default user - class: + Add the following line to the default user class: :label=biba/high: - Once this is completed, the following command must be - issued to rebuild the database: + Next, issue the following command to rebuild the + database: &prompt.root; cap_mkdb /etc/login.conf @@ -1725,9 +1580,8 @@ test: biba/low Boot Configuration - Do not reboot yet, just add the following lines to - /boot/loader.conf so the required - modules will load during system initialization: + Add the following lines to + /boot/loader.conf: mac_biba_load="YES" mac_seeotheruids_load="YES" @@ -1744,9 +1598,8 @@ mac_seeotheruids_load="YES" All user accounts that are not root or system users will now require a login class. The login class is required otherwise users will be refused access - to common commands such as &man.vi.1;. - The following sh script should do the - trick: + to common commands such as &man.vi.1;. The following + sh script should do the trick: &prompt.root; for x in `awk -F: '($3 >= 1001) && ($3 != 65534) { print $1 }' \ /etc/passwd`; do pw usermod $x -L default; done; @@ -1763,8 +1616,7 @@ mac_seeotheruids_load="YES" Create the Contexts File - A contexts file should now be created; the following - example file should be placed in + A contexts file should now be created as /etc/policy.contexts. # This is the default BIBA policy for this system. @@ -1802,28 +1654,28 @@ mac_seeotheruids_load="YES" /usr/local/etc/apache biba/10 /usr/local/etc/apache/* biba/10 - This policy will enforce security by setting restrictions + This policy enforces security by setting restrictions on the flow of information. In this specific configuration, - users, root and others, should never be + users, including root, should never be allowed to access Nagios. Configuration files and processes that are a part of Nagios will be completely self contained or jailed. - This file may now be read into our system by issuing the + This file will be read by the system by issuing the following command: &prompt.root; setfsmac -ef /etc/policy.contexts / &prompt.root; setfsmac -ef /etc/policy.contexts / - The above file system layout may be different depending - on environment; however, it must be run on every single file + The above file system layout will differ depending + upon the environment and must be run on every file system. - The /etc/mac.conf file requires - the following modifications in the main section: + /etc/mac.conf requires the following + modifications in the main section: default_labels file ?biba default_labels ifnet ?biba @@ -1855,45 +1707,43 @@ default_labels socket ?biba Ensure that the web server and - Nagios will not be started - on system initialization, and reboot. Ensure the + Nagios will not be started on + system initialization and reboot. Ensure the root user cannot access any of the files in the Nagios configuration directory. If root can issue an &man.ls.1; command on /var/spool/nagios, - then something is wrong. Otherwise a permission + something is wrong. Otherwise a permission denied error should be returned. If all seems well, Nagios, Apache, and - Sendmail can now be started in a - way fitting of the security policy. The following commands - will make this happen: + Sendmail can now be started: &prompt.root; cd /etc/mail && make stop && \ setpmac biba/equal make start && setpmac biba/10\(10-10\) apachectl start && \ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestart Double check to ensure that everything is working - properly. If not, check the log files or error messages. Use - the &man.sysctl.8; utility to disable the &man.mac.biba.4; - security policy module enforcement and try starting everything - again, like normal. + properly. If not, check the log files for error messages. + Use &man.sysctl.8; to disable the &man.mac.biba.4; security + policy module enforcement and try starting everything again as + usual. - The root user can change the - security enforcement and edit the configuration files - without fear. The following command will permit the - degradation of the security policy to a lower grade for a - newly spawned shell: + The root user can still change the + security enforcement and edit its configuration files. The + following command will permit the degradation of the + security policy to a lower grade for a newly spawned + shell: &prompt.root; setpmac biba/10 csh To block this from happening, force the user into a - range via &man.login.conf.5;. If &man.setpmac.8; attempts + range using &man.login.conf.5;. If &man.setpmac.8; attempts to run a command outside of the compartment's range, an error will be returned and the command will not be executed. - In this case, setting root to + In this case, set root to biba/high(high-high). @@ -1902,15 +1752,14 @@ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestart User Lock Down - This example considers a relatively small, fewer than fifty - users, storage system. Users would have login capabilities, - and be permitted to not only store data but access resources - as well. + This example considers a relatively small storage system + with fewer than fifty users. Users will have login + capabilities, and be permitted to store data and access + resources. - For this scenario, the &man.mac.bsdextended.4; mixed with - &man.mac.seeotheruids.4; could co-exist and block access not - only to system objects, but to hide user processes as - well. + For this scenario, the &man.mac.bsdextended.4; and + &man.mac.seeotheruids.4; policy modules could co-exist and block + access to system objects while hiding user processes. Begin by adding the following line to /boot/loader.conf: @@ -1918,25 +1767,24 @@ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestartmac_seeotheruids_load="YES" The &man.mac.bsdextended.4; security policy module may be - activated through the use of the following rc.conf - variable: + activated by adding this line to + /etc/rc.conf: ugidfw_enable="YES" Default rules stored in /etc/rc.bsdextended will be loaded at - system initialization; however, the default entries may need + system initialization. However, the default entries may need modification. Since this machine is expected only to service users, everything may be left commented out except the last - two. These will force the loading of user owned system objects - by default. + two lines in order to force the loading of user owned system + objects by default. Add the required users to this machine and reboot. For testing purposes, try logging in as a different user across - two consoles. Run the ps aux command to - see if processes of other users are visible. Try to run - &man.ls.1; on another users home directory, it should - fail. + two consoles. Run ps aux to see if processes + of other users are visible. Verify that running &man.ls.1; on + another user's home directory fails. Do not try to test with the root user unless the specific sysctls have been @@ -1945,9 +1793,8 @@ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestart When a new user is added, their &man.mac.bsdextended.4; rule will not be in the ruleset list. To update the ruleset - quickly, simply unload the security policy module and reload - it again using the &man.kldunload.8; and &man.kldload.8; - utilities. + quickly, unload the security policy module and reload it again + using &man.kldunload.8; and &man.kldload.8;. @@ -1958,30 +1805,23 @@ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestartMAC Troubleshooting - During the development stage, a few users reported problems - with normal configuration. Some of these problems - are listed below: + This section discusses common configuration issues. - The <option>multilabel</option> option cannot be enabled - on <filename>/</filename> + <option>multilabel</option> cannot be enabled on + <filename>/</filename> - The flag does not stay + The flag does not stay enabled on my root (/) partition! - It seems that one out of every fifty users has this - problem, indeed, we had this problem during our initial - configuration. Further observation of this so called - bug has lead me to believe that it is a - result of either incorrect documentation or misinterpretation - of the documentation. Regardless of why it happened, the - following steps may be taken to resolve it: + The following steps may resolve this transient + error: Edit /etc/fstab and set the root - partition at for read-only. + partition to for read-only. @@ -1995,7 +1835,7 @@ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestart - Reboot the system into normal mode. + Reboot the system. @@ -2007,7 +1847,7 @@ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestart - Double-check the output from the + Double-check the output from mount to ensure that has been properly set on the root file system. @@ -2016,12 +1856,12 @@ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestart - X11 Server Will Not Start After + <title>Xorg Server Will Not Start After <acronym>MAC</acronym> After establishing a secure environment with MAC, I am no longer able to start - X! + Xorg! This could be caused by the MAC partition policy or by a mislabeling in @@ -2035,25 +1875,21 @@ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestartpartition policy may be the culprit. Try setting the user's class back to the default class and rebuild the database - with the cap_mkdb command. If this - does not alleviate the problem, go to step two. + with cap_mkdb. If this does not + alleviate the problem, go to step two. Double-check the label policies. Ensure that the - policies are set correctly for the user in question, the - X11 application, and - the /dev - entries. + policies are set correctly for the user, the Xorg + application, and the /dev entries. If neither of these resolve the problem, send the - error message and a description of your environment to - the TrustedBSD discussion lists located at the - TrustedBSD - website or to the &a.questions; - mailing list. + error message and a description of the environment to + the &a.questions; mailing list. @@ -2062,52 +1898,50 @@ setpmac biba/10\(10-10\) /usr/local/etc/rc.d/nagios.sh forcestartError: &man..secure.path.3; cannot stat .login_conf - When I attempt to switch from the + When a user attempts to switch from the root user to another user in the system, the error message _secure_path: unable to state .login_conf appears. This message is usually shown when the user has a higher - label setting then that of the user whom they are attempting - to become. For instance a user on the system, - joe, has a default label of - . The root - user, who has a label of , cannot - view joe's home directory. This will - happen regardless if root has used the - su command to become - joe, or not. In this scenario, the Biba - integrity model will not permit root to - view objects set at a lower integrity level. + label setting than that of the user they are attempting to + become. For instance, joe has a default + label of . The + root user, who has a label of + , cannot view + joe's home directory. This will happen + whether or not root has used + su to become joe as + the Biba integrity model will not permit + root to view objects set at a lower + integrity level. The <username>root</username> username is broken! In normal or even single user mode, the - root is not recognized. The - whoami command returns 0 (zero) and + root is not recognized, + whoami returns 0 (zero), and su returns who are - you?. What could be going on? + you?. This can happen if a labeling policy has been disabled, either by a &man.sysctl.8; or the policy module was unloaded. - If the policy is being disabled or has been temporarily - disabled, then the login capabilities database needs to be - reconfigured with the option being - removed. Double check the login.conf - file to ensure that all options have - been removed and rebuild the database with the - cap_mkdb command. - - This may also happen if a policy restricts access to the - master.passwd file or database. Usually - caused by an administrator altering the file under a label - which conflicts with the general policy being used by the - system. In these cases, the user information would be read - by the system and access would be blocked as the file has - inherited the new label. Disable the policy via a - &man.sysctl.8; and everything should return to normal. + If the policy is disabled, the login capabilities database + needs to be reconfigured with removed. + Double check login.conf to ensure that + all options have been removed and + rebuild the database with cap_mkdb. + + This may also happen if a policy restricts access to + master.passwd. This is usually caused by + an administrator altering the file under a label which + conflicts with the general policy being used by the system. + In these cases, the user information would be read by the + system and access would be blocked as the file has inherited + the new label. Disable the policy using &man.sysctl.8; and + everything should return to normal. -- cgit v1.2.3