IBM 10 SP1 EAL4 5.16 Supporting functions, 5.16.1 TSF libraries

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5.16 Supporting functions

Trusted programs and trusted processes in an SLES system use libraries. Libraries do not form a subsystem

in the notation of the Common Criteria, but they provide supporting functions to trusted commands and

processes.

A library is an archive of link-edited objects and their export files. A shared library is an archive of objects

that has been bound as a module with imports and exports, and is marked as a shared object. When an object

exported by a shared library is referenced, the loader checks for the object in the calling process’s shared

library segment.

If the library is there, the links are resolved, and the program can call the shared library code. If the library

isn’t there, the loader pages the library into the shared memory segment, where it can subsequently be used by

other programs. This section briefly describes the library and system-call linking mechanism in user and

kernel space, and illustrates any security implications.

5.16.1 TSF libraries

The following table lists some of the libraries that are used by trusted programs and processes. The libraries

may also be used by untrusted programs, but are still part of the TSF. The libraries are protected from

modification by the file system DAC mechanism.

213

Models

10 SP1 EAL4

Contents

3Table of Contents
13 1 Introduction
- 1.1 Purpose of this document
- 1.2 Document overview
- 1.3 Conventions used in this document
- 1.4 Terminology
14 2 System Overview
- Figure 2-1: Series of TOE systems connected by a physically protected LAN
- 15 2.1 Product history
- 2.1.1 SUSE Linux Enterprise Server
- 2.1.2 eServer systems
- 2.2 High-level product overview
- 16 2.2.1 eServer host computer structure
  - Figure 2-2: Overall structure of the TOE
- 18 2.2.2 eServer system structure
- 2.2.3 TOE services
- 19 2.2.4 Security policy
  - Figure 2-3: Local and network services provided by SLES
- 20 2.2.5 Operation and administration
- 2.2.6 TSF interfaces
- 21 2.3 Approach to TSF identification
24 3 Hardware architecture
- 3.1 System x
- 3.1.1 System x hardware overview
- 3.1.2 System x hardware architecture
- 25 3.2 System p
- 3.2.1 System p hardware overview
- 3.2.2 System p hardware architecture
- 26 3.3 System z
- 3.3.1 System z hardware overview
- 3.3.2 System z hardware architecture
- 27 3.4 eServer 326
  - Figure 3-1: z/VM as hypervisor
- 3.4.1 eServer 326 hardware overview
- 3.4.2 eServer 326 hardware architecture
  - 28Figure 3-2: AMD x86-64 architecture in compatibility mode
30 4 Software architecture
- 4.1 Hardware and software privilege
- 4.1.1 Hardware privilege
  - 4.1.1.1 Privilege level
  - 31Figure 4-1: Levels of Privilege
- 32 4.1.2 Software privilege
  - 33 4.1.2.1 DAC
  - 4.1.2.1.1 Subjects and objects
  - 4.1.2.1.2 Attributes
  - 4.1.2.1.3 Access control rules
  - 4.1.2.1.4 Software privilege
  - 4.1.2.2 AppArmor
  - 4.1.2.3 Programs with software privilege
- 34 4.2 TOE Security Functions software structure
  - Figure 4-2: TSF and non-TSF software
- 35 4.2.1 Kernel TSF software
  - 4.2.1.1 Logical components
  - 36Figure 4-3: Logical kernel subsystems and their interactions
    - 4.2.1.2 Execution components
  - 37Figure 4-4: Kernel execution components
    - 4.2.1.2.1 Base kernel
    - 4.2.1.2.2 Kernel threads
    - 4.2.1.2.3 Kernel modules and device drivers
- 38 4.2.2 Non-kernel TSF software
- 40 4.3 TSF databases
- 4.4 Definition of subsystems for the CC evaluation
- 41 4.4.1 Hardware
- 4.4.2 Firmware
- 4.4.3 Kernel subsystems
- 4.4.4 Trusted process subsystems
- 42 4.4.5 User-level audit subsystem
44 5 Functional descriptions
- 5.1 File and I/O management
  - Figure 5-1: File and I/O subsystem and its interaction with other subsystems
- 45 5.1.1 Virtual File System
  - Figure 5-2: ext3 and CD-ROM file systems before mounting
  - 46Figure 5-3: ext3 and CD-ROM file systems after mounting
  - Figure 5-4: Virtual file system
    - 47 5.1.1.1 Pathname translation
    - 5.1.1.2 open()
  - 49Figure 5-6: VFS data structures and their relationships with each other
    - 50 5.1.1.3 write()
    - 5.1.1.4 mount()
    - 5.1.1.5 Shared subtrees
- 51 5.1.2 Disk-based file systems
  - 5.1.2.1 Ext3 file system
  - 5.1.2.1.1 Extended Attributes
  - 5.1.2.1.2 Data structures
  - 52Figure 5-7: Security attributes, extended security attributes, and data blocks for the ext3 inode
  - 55Figure 5-9: Access control on ext3 file system
    - 5.1.2.2 ISO 9660 file system for CD-ROM
    - 5.1.2.2.1 Data structures and algorithms
- 56 5.1.3 Pseudo file systems
  - Figure 5-10: File lookup on CD-ROM file system
    - 5.1.3.1 procfs
    - 5.1.3.2 tmpfs
    - 57 5.1.3.3 sysfs
    - 5.1.3.4 devpts
    - 5.1.3.5 rootfs
    - 5.1.3.6 binfmt_misc
    - 5.1.3.7 securityfs
    - 5.1.3.8 configfs
- 58 5.1.4 inotify
- 5.1.5 Discretionary Access Control (DAC)
  - 59 5.1.5.1 Permission bits
  - 60 5.1.5.2 Access Control Lists
  - 5.1.5.2.1 Types of ACL tags
  - 5.1.5.2.2 ACL qualifier
  - 61 5.1.5.2.3 ACL permissions
  - 5.1.5.2.4 Relationship to file permission bits
  - 5.1.5.2.5 ACL_MASK
  - 5.1.5.2.6 Default ACLs and ACL inheritance
  - 5.1.5.2.7 ACL representations and interfaces
  - 62 5.1.5.2.8 ACL enforcement
- 63 5.1.6 Asynchronous I/O
- 5.1.7 I/O scheduler
  - 64 5.1.7.1 Deadline I/O scheduler
  - 5.1.7.2 Anticipatory I/O scheduler
  - 5.1.7.3 Completely Fair Queuing scheduler
  - 5.1.7.4 Noop I/O scheduler
- 65 5.1.8 I/O interrupts
  - 5.1.8.1 Top halves
  - 5.1.8.2 Bottom halves
  - 5.1.8.3 Softirqs
  - 5.1.8.4 Tasklets
  - 5.1.8.5 Work queue
- 66 5.1.9 Processor interrupts
- 5.1.10 Machine check
- 67 5.2 Process control and management
  - Figure 5-11: Process subsystem and its interaction with other subsystems
- 5.2.1 Data structures
  - Figure 5-12: The task structure
- 69 5.2.2 Process creation and destruction
  - 5.2.2.1 Control of child processes
  - 5.2.2.2 DAC controls 5.2.2.2.1 setuid()and setgid()
  - 5.2.2.2.2 seteuid()and setegid()
  - 5.2.2.2.3 setreuid()and setregid()
  - 5.2.2.2.4 setresuid()and setresgid()
  - 5.2.2.3 execve()
  - 5.2.2.4 do_exit()
- 70 5.2.3 Process switch
- 5.2.4 Kernel threads
- 71 5.2.5 Scheduling
  - Figure 5-13: O(1) scheduling
- 72 5.2.6 Kernel preemption
  - Figure 5-14: Hyperthreaded scheduling
- 73 5.3 Inter-process communication
- 74 5.3.1 Pipes
  - Figure 5-15: Pipes Implementation
    - 5.3.1.1 Data structures and algorithms
- 75 5.3.2 First-In First-Out Named pipes
  - 5.3.2.1 FIFO creation
  - 5.3.2.2 FIFO open
- 76 5.3.3 System V IPC
  - 5.3.3.1 Common data structures
  - 77 5.3.3.2 Common functions
  - 5.3.3.2.1 ipc_alloc()
  - 5.3.3.2.2 ipcperms()
  - 5.3.3.3 Message queues
  - 5.3.3.3.1 msg_queue
  - 5.3.3.3.2 msg_msg
- 80 5.3.4 Signals
  - 5.3.4.1 Data structures
  - 5.3.4.2 Algorithms
- 5.3.5 Sockets
- 81 5.4 Network subsystem
  - Figure 5-16: Object reuse handling in socket allocation
- 82 5.4.1 Overview of the network protocol stack
  - Figure 5-17: Network subsystem and its interaction with other subsystems
  - 83Figure 5-18: How data travels through the Network protocol stack
- 84 5.4.2 Transport layer protocols
  - 5.4.2.1 TCP
  - 5.4.2.2 UDP
- 5.4.3 Network layer protocols
  - 5.4.3.1 Internet Protocol Version 4 (IPv4)
  - 5.4.3.2 Internet Protocol Version 6 (IPv6)
  - 85 5.4.3.2.1 Addressing
  - 5.4.3.2.2 IPv6 Header
  - 86 5.4.3.2.3 Flow Labels
  - 5.4.3.2.4 Security
  - 5.4.3.3 Transition between IPv4 and IPv6
  - 5.4.3.4 IP Security (IPsec)
  - 87 5.4.3.4.1 Functional Description of IPsec
- 90 5.4.4 Internet Control Message Protocol (ICMP)
  - 5.4.4.1 Link layer protocols
  - 5.4.4.1.1 Address Resolution Protocol (ARP)
- 91 5.4.5 Network services interface
  - Figure 5-19: Server and client operations using socket interface
    - 5.4.5.1 socket()
  - 92Figure 5-20: bind() function for internet domain TCP socket
    - 5.4.5.2 bind()
  - 93Figure 5-21: bind() function for UNIX domain TCP socket
    - 5.4.5.3 listen()
    - 5.4.5.4 accept()
    - 5.4.5.5 connect()
    - 5.4.5.6 Generic calls
    - 5.4.5.7 Access control
- 94 5.5 Memory management
  - Figure 5-22: Mapping read, write and close calls for sockets
  - 95Figure 5-23: Memory subsystem and its interaction with other subsystems
- 96 5.5.1 Four-Level Page Tables
  - Figure 5-24: Previous three-level page-tables architecture
- 97 5.5.2 Memory addressing
  - 5.5.2.1 System x
  - Figure 5-25: New page-table implementation: the four-level page-table architecture
  - 98Figure 5-26: System x virtual addressing space
  - Figure 5-27: Logical Address Translation
    - 5.5.2.1.1 Segmentation
  - 99Figure 5-28: Access control through segmentation
    - 5.5.2.1.2 Paging
  - 100Figure 5-29: Contiguous linear addresses map to contiguous physical addresses
  - 102Figure 5-32: Access control through paging
  - 104Figure 5-33: Paging data structures
    - 5.5.2.2 System p
  - 105Figure 5-34: Logical partitions
  - Figure 5-35: Machine state register
    - 108 5.5.2.2.1 Address Translation on LPARs
    - 5.5.2.2.2 Hypervisor
    - 5.5.2.2.3 Real mode addressing
    - 109 5.5.2.2.4 Virtual mode addressing
    - 5.5.2.2.5 Access to I/O address space
    - 5.5.2.2.6 Direct Memory Access addressing
  - 110Figure 5-38: DMA addressing
    - 5.5.2.2.7 Run-Time Abstraction Services
    - 5.5.2.2.8 Preventing denial of service
    - 5.5.2.3 System p native mode
  - 111Figure 5-39: Effective address
  - Figure 5-40: Virtual address
    - 5.5.2.3.1 Machine State Register
  - 112Figure 5-41: Block address
  - Figure 5-42: Machine state register
    - 5.5.2.3.2 Page descriptor
    - 5.5.2.3.3 Segment descriptor
    - 5.5.2.3.4 Block descriptor
  - 113Figure 5-43: Page table entry
  - Figure 5-44: Segment Table Entry
    - 5.5.2.3.5 Address translation mechanisms
  - 114Figure 5-46: Address translation method selection
  - Figure 5-45: Block Address Translation entry
  - 115Figure 5-47: Block Address Translation access control
    - 5.5.2.3.6 Page Address Translation and access control
    - 118 5.5.2.4 System z
    - 5.5.2.4.1 Native hardware mode
    - 5.5.2.4.2 LPAR mode
    - 5.5.2.4.3 z/VM Guest mode
    - 5.5.2.4.4 Address types
    - 119 5.5.2.4.5 Address sizes
    - 5.5.2.4.6 Address spaces
    - 5.5.2.4.7 Address translations
  - 121Figure 5-51: Address translation modes
    - 5.5.2.4.8 Memory protection mechanisms
  - 123Figure 5-53: Low-address protection on effective address
  - 127Figure 5-56: Key match logic for key-controlled protection
  - 128Figure 5-57: Fetch protection override for key-controlled
    - 5.5.2.5 eServer 326
    - 5.5.2.5.1 Logical address
    - 5.5.2.5.2 Effective address
  - 129Figure 5-58: eServer 326 address types and their conversion units
    - 5.5.2.5.3 Linear address
    - 5.5.2.5.4 Physical address
    - 5.5.2.5.5 Segmentation
  - 130Figure 5-59: Data access privilege checks
    - 131 5.5.2.5.6 Paging
    - 5.5.2.5.7 Translation Lookaside Buffers
- 135 5.5.3 Kernel memory management
  - 5.5.3.1 Support for NUMA servers
  - 136Figure 5-64: NUMA Design
    - 5.5.3.2 Reverse map Virtual Memory
  - 137Figure 5-65: Rmap VM
    - 5.5.3.3 Huge Translation Lookaside Buffers
  - 138Figure 5-66: TLB Operation
    - 5.5.3.4 Remap_file_pages
  - 139Figure 5-67: Remap_ file_ pages for database applications
    - 5.5.3.5 Page frame management
    - 5.5.3.6 Memory area management
    - 5.5.3.7 Noncontiguous memory area management
- 140 5.5.4 Process address space
  - 141Figure 5-68: Object reuse handling while allocating new linear address
- 142 5.5.5 Symmetric multiprocessing and synchronization
  - 5.5.5.1 Atomic operations
  - 5.5.5.2 Memory barriers
  - 5.5.5.3 Spin locks
  - 5.5.5.4 Kernel semaphores
- 143 5.6 Audit subsystem
- 5.6.1 Audit components
  - 144Figure 5-69: Audit framework components
    - 5.6.1.1 Audit kernel components
    - 5.6.1.1.1 Kernel-userspace interface
    - 5.6.1.1.2 Syscall auditing
  - 145Figure 5-70: Audit Kernel Components
    - 5.6.1.1.3 Filesystem watches
    - 5.6.1.1.4 Task structure
  - 146Figure 5-71: Task Structure
    - 5.6.1.1.5 Audit context fields
    - 147 5.6.1.2 File system audit components
    - 148 5.6.1.3 User space audit components
- 149 5.6.2 Audit operation and configuration options
  - Figure 5-72: Audit User Space Components
    - 5.6.2.1 Configuration
    - 151 5.6.2.2 Operation
- 152 5.6.3 Audit records
  - 5.6.3.1 Audit record generation
  - 5.6.3.1.1 Kernel record generation
  - 153Figure 5-73: Audit Record Generation
    - 5.6.3.1.2 Syscall audit record generation
  - 154Figure 5-74: Extension to system calls interface
    - 5.6.3.1.3 File system audit record generation
    - 5.6.3.1.4 Socket call and IPC audit record generation
  - 155Figure 5-75: User Space Record Generation
    - 5.6.3.1.5 Record generation by trusted programs
    - 5.6.3.2 Audit record format
- 158 5.6.4 Audit tools
  - 5.6.4.1 auditctl
  - 5.6.4.2 ausearch
- 5.6.5 Login uid association
- 5.7 Kernel modules
- 159 5.7.1 Linux Security Module framework
- 161 5.7.2 LSM capabilities module
  - Figure 5-76: LSM hook architecture
- 5.7.3 LSM AppArmor module
- 5.8 AppArmor
- 162 5.8.1 AppArmor administrative utilities
- 163 5.8.2 AppArmor access control functions
- 5.8.3 securityfs
- 164 5.9 Device drivers
- 5.9.1 I/O virtualization on System z
  - 5.9.1.1 Interpretive-execution facility
  - 165 5.9.1.2 State description
  - 5.9.1.3 Hardware virtualization and simulation
- 166 5.9.2 Character device driver
- 167 5.9.3 Block device driver
  - Figure 5-77: Setup of f_op for character device specific file operations
- 168 5.10 System initialization
  - Figure 5-78: Setup of f_op for block device specific file operations
- 5.10.1 init
- 169 5.10.2 System x
  - 170 5.10.2.1 Boot methods
  - 5.10.2.2 Boot loader
  - 5.10.2.3 Boot process
- 173 5.10.3 System p
  - 5.10.3.1 Boot methods
  - 5.10.3.2 Boot loader
  - 5.10.3.3 Boot process
  - 176 5.10.4.1 Boot process
- 178 5.10.5 System z
  - 5.10.5.1 Boot methods
  - 5.10.5.2 Control program
  - 5.10.5.3 Boot process
- 180 5.10.6 eServer 326
  - Figure 5-82: System z SLES boot sequence
    - 5.10.6.1 Boot methods
    - 181 5.10.6.2 Boot loader
    - 5.10.6.3 Boot process
- 183 5.11 Identification and authentication
  - Figure 5-83: eServer 326 SLES boot sequence
- 184 5.11.1 Pluggable Authentication Module
  - 5.11.1.1 Overview
  - 185 5.11.1.2 Configuration terminology
  - 5.11.1.3 Modules
- 187 5.11.2 Protected databases
  - 5.11.2.1 Access control rules 5.11.2.1.1 DAC
  - 5.11.2.1.2 Software privilege
- 188 5.11.3 Trusted commands and trusted processes
  - 5.11.3.1 agetty
  - 189 5.11.3.2 gpasswd
  - 5.11.3.3 login
  - 190 5.11.3.4 mingetty
  - 5.11.3.5 newgrp
  - 191 5.11.3.6 passwd
  - 5.11.3.7 su
- 192 5.11.4 Interaction with audit
- 5.12 Network applications
- 5.12.1 OpenSSL Secure socket-layer interface
  - 193Figure 5-84: SSL location in the network stack
    - 5.12.1.1 Concepts
    - 5.12.1.1.1 Encryption
  - 194Figure 5-86: Decryption
  - Figure 5-85: Encryption
  - 195Figure 5-87: Encryption Algorithm and Key
    - 197 5.12.1.1.2 Message digest
    - 5.12.1.1.3 Message Authentication Code (MAC)
    - 5.12.1.1.4 Digital certificates and certificate authority
    - 5.12.1.2 SSL architecture
  - 198Figure 5-90: SSL Protocol
    - 5.12.1.2.1 SSL handshake protocol
  - 200Figure 5-92: SSL protocol action
    - 5.12.1.3 OpenSSL algorithms
    - 5.12.1.4 Symmetric ciphers
    - 201 5.12.1.4.1 Asymmetric ciphers
    - 5.12.1.4.2 Certificates
    - 5.12.1.4.3 Hash functions
- 202 5.12.2 Secure Shell
  - 203 5.12.2.1 SSH client
  - 5.12.2.2 SSH server daemon
- 204 5.12.3 Very Secure File Transfer Protocol daemon
- 5.12.4 CUPS
  - 205 5.12.4.1 cupsd
  - 206 5.12.4.2 ping
  - 5.12.4.3 ping6
  - 5.12.4.4 openssl
  - 207 5.12.4.5 stunnel
  - 5.12.4.6 xinetd
- 208 5.13 System management 5.13.1 Account Management
  - 5.13.1.1 chage
  - 209 5.13.1.2 chfn
  - 5.13.1.3 chsh
- 210 5.13.2 User management
  - 5.13.2.1 useradd
  - 5.13.2.2 usermod
  - 211 5.13.2.3 userdel
- 212 5.13.3 Group management
  - 5.13.3.1 groupadd
  - 213 5.13.3.2 groupmod
  - 5.13.3.3 groupdel
- 215 5.13.4 System Time management
  - 5.13.4.1 date
  - 5.13.4.2 hwclock
- 5.13.5 Other System Management
  - 5.13.5.1 AMTU
  - 216 5.13.5.1.1 Memory
  - 5.13.5.1.2 Memory separation
  - 5.13.5.1.3 I/O controller and network
  - 5.13.5.1.4 I/O controller and disk
  - 5.13.5.1.5 Supervisor mode instructions
  - 218 5.13.5.1.6 AMTU output
  - 5.13.5.2 star
- 220 5.13.6 I&A support
  - 5.13.6.1 pam_tally
  - 5.13.6.2 unix_chkpwd
- 5.14 Batch processing
- 5.14.1 Batch processing user commands
  - 5.14.1.1 crontab
  - 221 5.14.1.2 at
- 222 5.14.2 Batch processing daemons
  - 5.14.2.1 cron
  - 5.14.2.2 atd
- 223 5.15 User-level audit subsystem
- 5.15.1 Audit daemon
- 5.15.2 Audit utilities
  - 5.15.2.1 aureport
  - 5.15.2.2 ausearch
  - 5.15.2.3 autrace
- 224 5.15.3 Audit configuration files
- 5.15.4 Audit logs
- 225 5.16 Supporting functions
- 5.16.1 TSF libraries
  - 226Library Description
- 227 5.16.2 Library linking mechanism
- 5.16.3 System call linking mechanism
  - 5.16.3.1 System x
  - 5.16.3.2 System p
  - 5.16.3.3 System z
  - 5.16.3.4 eServer 326
- 228 5.16.4 System call argument verification
230 6 Mapping the TOE summary specification to the High-Level Design
- 233 6.7.4 Trusted processes (TP.4)
- 6.7.5 TSF Databases (TP.5)
- 6.7.6 Internal TOE protection mechanisms (TP.6)
- 6.7.7 Testing the TOE protection mechanisms (TP.7)
- 6.8 Security enforcing interfaces between subsystems
- 234 6.8.1 Summary of kernel subsystem interfaces
  - 6.8.1.1 Kernel subsystem file and I/O
  - 6.8.1.1.1 External Interfaces
  - 235 6.8.1.1.2 Internal Interfaces 6.8.1.1.3
  - 236 6.8.1.1.4 Data Structures
  - 6.8.1.2 Kernel subsystem process control and management
  - 6.8.1.2.1 External interfaces (system calls)
  - 237 6.8.1.2.2 Internal Interfaces
  - 6.8.1.2.3 Data Structures
  - 6.8.1.3 Kernel subsystem inter-process communication
  - 238 6.8.1.3.1 External interfaces (system calls)
  - 6.8.1.3.2 Internal Interfaces
  - 6.8.1.3.3 Data Structures
  - 239 6.8.1.4 Kernel subsystem networking
  - 6.8.1.4.1 External interfaces (system calls)
  - 6.8.1.4.2 Internal interfaces
  - 6.8.1.4.3 Data Structures
  - 6.8.1.5 Kernel subsystem memory management
  - 6.8.1.5.1 External interfaces (system calls)
  - 240 6.8.1.5.2 Internal interfaces
  - 6.8.1.5.3 Data Structures
  - 6.8.1.6 Kernel subsystem audit
  - 6.8.1.6.1 External interfaces
  - 6.8.1.6.2 Internal interfaces
  - 241 6.8.1.6.3 Data structures
  - 6.8.1.7 Kernel subsystem device drivers 6.8.1.7.1 External interfaces (system calls)
  - 6.8.1.7.2 Internal interfaces
- 243 6.8.2 Summary of trusted processes interfaces
244 7 References