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NAME

privileges - process privilege model
 

DESCRIPTION

Solaris software implements a set of privileges that provide fine-grained control over the actions of processes. The possession of a certain privilege allows a process to perform a specific set of restricted operations.

The change to a primarily privilege-based security model in the Solaris operating system gives developers an opportunity to restrict processes to those privileged operations actually needed instead of all (super-user) or no privileges (non-zero UIDs). Additionally, a set of previously unrestricted operations now requires a privilege; these privileges are dubbed the "basic" privileges and are by default given to all processes.

Taken together, all defined privileges with the exception of the "basic" privileges compose the set of privileges that are traditionally associated with the root user. The "basic" privileges are "privileges" unprivileged processes were accustomed to having.

The defined privileges are:

PRIV_CONTRACT_EVENT

Allow a process to request reliable delivery of events to an event endpoint.

Allow a process to include events in the critical event set term of a template which could be generated in volume by the user.

PRIV_CONTRACT_IDENTITY

Allows a process to set the service FMRI value of a process contract template.

PRIV_CONTRACT_OBSERVER

Allow a process to observe contract events generated by contracts created and owned by users other than the process's effective user ID.

Allow a process to open contract event endpoints belonging to contracts created and owned by users other than the process's effective user ID.

PRIV_CPC_CPU

Allow a process to access per-CPU hardware performance counters.

PRIV_DTRACE_KERNEL

Allow DTrace kernel-level tracing.

PRIV_DTRACE_PROC

Allow DTrace process-level tracing. Allow process-level tracing probes to be placed and enabled in processes to which the user has permissions.

PRIV_DTRACE_USER

Allow DTrace user-level tracing. Allow use of the syscall and profile DTrace providers to examine processes to which the user has permissions.

PRIV_FILE_CHOWN

Allow a process to change a file's owner user ID. Allow a process to change a file's group ID to one other than the process's effective group ID or one of the process's supplemental group IDs.

PRIV_FILE_CHOWN_SELF

Allow a process to give away its files. A process with this privilege will run as if {_POSIX_CHOWN_RESTRICTED} is not in effect.

PRIV_FILE_DAC_EXECUTE

Allow a process to execute an executable file whose permission bits or ACL would otherwise disallow the process execute permission.

PRIV_FILE_DAC_READ

Allow a process to read a file or directory whose permission bits or ACL would otherwise disallow the process read permission.

PRIV_FILE_DAC_SEARCH

Allow a process to search a directory whose permission bits or ACL would not otherwise allow the process search permission.

PRIV_FILE_DAC_WRITE

Allow a process to write a file or directory whose permission bits or ACL do not allow the process write permission. All privileges are required to write files owned by UID 0 in the absence of an effective UID of 0.

PRIV_FILE_DOWNGRADE_SL

Allow a process to set the sensitivity label of a file or directory to a sensitivity label that does not dominate the existing sensitivity label.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_FILE_LINK_ANY

Allow a process to create hardlinks to files owned by a UID different from the process's effective UID.

PRIV_FILE_OWNER

Allow a process that is not the owner of a file to modify that file's access and modification times. Allow a process that is not the owner of a directory to modify that directory's access and modification times. Allow a process that is not the owner of a file or directory to remove or rename a file or directory whose parent directory has the "save text image after execution" (sticky) bit set. Allow a process that is not the owner of a file to mount a namefs upon that file. Allow a process that is not the owner of a file or directory to modify that file's or directory's permission bits or ACL.

PRIV_FILE_SETID

Allow a process to change the ownership of a file or write to a file without the set-user-ID and set-group-ID bits being cleared. Allow a process to set the set-group-ID bit on a file or directory whose group is not the process's effective group or one of the process's supplemental groups. Allow a process to set the set-user-ID bit on a file with different ownership in the presence of PRIV_FILE_OWNER. Additional restrictions apply when creating or modifying a setuid 0 file.

PRIV_FILE_UPGRADE_SL

Allow a process to set the sensitivity label of a file or directory to a sensitivity label that dominates the existingsensitivity label.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_FILE_FLAG_SET

Allows a process to set immutable, nounlink or appendonly file attributes.

PRIV_GRAPHICS_ACCESS

Allow a process to make privileged ioctls to graphics devices. Typically only an xserver process needs to have this privilege. A process with this privilege is also allowed to perform privileged graphics device mappings.

PRIV_GRAPHICS_MAP

Allow a process to perform privileged mappings through a graphics device.

PRIV_IPC_DAC_READ

Allow a process to read a System V IPC Message Queue, Semaphore Set, or Shared Memory Segment whose permission bits would not otherwise allow the process read permission.

PRIV_IPC_DAC_WRITE

Allow a process to write a System V IPC Message Queue, Semaphore Set, or Shared Memory Segment whose permission bits would not otherwise allow the process write permission.

PRIV_IPC_OWNER

Allow a process that is not the owner of a System V IPC Message Queue, Semaphore Set, or Shared Memory Segment to remove, change ownership of, or change permission bits of the Message Queue, Semaphore Set, or Shared Memory Segment.

PRIV_NET_BINDMLP

Allow a process to bind to a port that is configured as a multi-level port (MLP) for the process's zone. This privilege applies to both shared address and zone-specific address MLPs. See tnzonecfg(4) from the Trusted Extensions manual pages for information on configuring MLP ports.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_NET_ICMPACCESS

Allow a process to send and receive ICMP packets.

PRIV_NET_MAC_AWARE

Allow a process to set the NET_MAC_AWARE process flag by using setpflags(2). This privilege also allows a process to set the SO_MAC_EXEMPT socket option by using setsockopt(3SOCKET). The NET_MAC_AWARE process flag and the SO_MAC_EXEMPT socket option both allow a local process to communicate with an unlabeled peer if the local process's label dominates the peer's default label, or if the local process runs in the global zone.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_NET_OBSERVABILITY

Allow a process to open a device for just receiving network traffic, sending traffic is disallowed.

PRIV_NET_PRIVADDR

Allow a process to bind to a privileged port number. The privilege port numbers are 1-1023 (the traditional UNIX privileged ports) as well as those ports marked as "udp/tcp_extra_priv_ports" with the exception of the ports reserved for use by NFS and SMB.

PRIV_NET_RAWACCESS

Allow a process to have direct access to the network layer.

PRIV_PROC_AUDIT

Allow a process to generate audit records. Allow a process to get its own audit pre-selection information.

PRIV_PROC_CHROOT

Allow a process to change its root directory.

PRIV_PROC_CLOCK_HIGHRES

Allow a process to use high resolution timers.

PRIV_PROC_EXEC

Allow a process to call exec(2).

PRIV_PROC_FORK

Allow a process to call fork(2), fork1(2), or vfork(2).

PRIV_PROC_INFO

Allow a process to examine the status of processes other than those to which it can send signals. Processes that cannot be examined cannot be seen in /proc and appear not to exist.

PRIV_PROC_LOCK_MEMORY

Allow a process to lock pages in physical memory.

PRIV_PROC_OWNER

Allow a process to send signals to other processes and inspect and modify the process state in other processes, regardless of ownership. When modifying another process, additional restrictions apply: the effective privilege set of the attaching process must be a superset of the target process's effective, permitted, and inheritable sets; the limit set must be a superset of the target's limit set; if the target process has any UID set to 0 all privilege must be asserted unless the effective UID is 0. Allow a process to bind arbitrary processes to CPUs.

PRIV_PROC_PRIOCNTL

Allow a process to elevate its priority above its current level. Allow a process to change its scheduling class to any scheduling class, including the RT class.

PRIV_PROC_SESSION

Allow a process to send signals or trace processes outside its session.

PRIV_PROC_SETID

Allow a process to set its UIDs at will, assuming UID 0 requires all privileges to be asserted.

PRIV_PROC_TASKID

Allow a process to assign a new task ID to the calling process.

PRIV_PROC_ZONE

Allow a process to trace or send signals to processes in other zones. See zones(5).

PRIV_SYS_ACCT

Allow a process to enable and disable and manage accounting through acct(2).

PRIV_SYS_ADMIN

Allow a process to perform system administration tasks such as setting node and domain name and specifying coreadm(1M) and nscd(1M) settings

PRIV_SYS_AUDIT

Allow a process to start the (kernel) audit daemon. Allow a process to view and set audit state (audit user ID, audit terminal ID, audit sessions ID, audit pre-selection mask). Allow a process to turn off and on auditing. Allow a process to configure the audit parameters (cache and queue sizes, event to class mappings, and policy options).

PRIV_SYS_CONFIG

Allow a process to perform various system configuration tasks. Allow filesystem-specific administrative procedures, such as filesystem configuration ioctls, quota calls, creation and deletion of snapshots, and manipulating the PCFS bootsector.

PRIV_SYS_DEVICES

Allow a process to create device special files. Allow a process to successfully call a kernel module that calls the kernel drv_priv(9F) function to check for allowed access. Allow a process to open the real console device directly. Allow a process to open devices that have been exclusively opened.

PRIV_SYS_DL_CONFIG

Allow a process to configure a system's datalink interfaces.

PRIV_SYS_IP_CONFIG

Allow a process to configure a system's IP interfaces and routes. Allow a process to configure network parameters for TCP/IP using ndd. Allow a process access to otherwise restricted TCP/IP information using ndd. Allow a process to configure IPsec. Allow a process to pop anchored STREAMs modules with matching zoneid.

PRIV_SYS_IPC_CONFIG

Allow a process to increase the size of a System V IPC Message Queue buffer.

PRIV_SYS_LINKDIR

Allow a process to unlink and link directories.

PRIV_SYS_MOUNT

Allow a process to mount and unmount filesystems that would otherwise be restricted (that is, most filesystems except namefs). Allow a process to add and remove swap devices.

PRIV_SYS_NET_CONFIG

Allow a process to do all that PRIV_SYS_IP_CONFIG and PRIV_SYS_DL_CONFIG allow, plus the following: push the rpcmod STREAMS module and INSERT/REMOVE STREAMS modules on locations other than the top of the module stack.

PRIV_SYS_NFS

Allow a process to provide NFS service: start NFS kernel threads, perform NFS locking operations, bind to NFS reserved ports: ports 2049 (nfs) and port 4045 (lockd).

PRIV_SYS_RES_CONFIG

Allow a process to create and delete processor sets, assign CPUs to processor sets and override the PSET_NOESCAPE property. Allow a process to change the operational status of CPUs in the system using p_online(2). Allow a process to configure filesystem quotas. Allow a process to configure resource pools and bind processes to pools.

PRIV_SYS_RESOURCE

Allow a process to exceed the resource limits imposed on it by setrlimit(2) and setrctl(2).

PRIV_SYS_SMB

Allow a process to provide NetBIOS or SMB services: start SMB kernel threads or bind to NetBIOS or SMB reserved ports: ports 137, 138, 139 (NetBIOS) and 445 (SMB).

PRIV_SYS_SUSER_COMPAT

Allow a process to successfully call a third party loadable module that calls the kernel suser() function to check for allowed access. This privilege exists only for third party loadable module compatibility and is not used by Solaris proper.

PRIV_SYS_TIME

Allow a process to manipulate system time using any of the appropriate system calls: stime(2), adjtime(2), and ntp_adjtime(2).

PRIV_SYS_TRANS_LABEL

Allow a process to translate labels that are not dominated by the process's sensitivity label to and from an external string form.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_VIRT_MANAGE

Allows a process to manage virtualized environments such as xVM(5).

PRIV_WIN_COLORMAP

Allow a process to override colormap restrictions.

Allow a process to install or remove colormaps.

Allow a process to retrieve colormap cell entries allocated by other processes.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_CONFIG

Allow a process to configure or destroy resources that are permanently retained by the X server.

Allow a process to use SetScreenSaver to set the screen saver timeout value

Allow a process to use ChangeHosts to modify the display access control list.

Allow a process to use GrabServer.

Allow a process to use the SetCloseDownMode request that can retain window, pixmap, colormap, property, cursor, font, or graphic context resources.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_DAC_READ

Allow a process to read from a window resource that it does not own (has a different user ID).

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_DAC_WRITE

Allow a process to write to or create a window resource that it does not own (has a different user ID). A newly created window property is created with the window's user ID.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_DEVICES

Allow a process to perform operations on window input devices.

Allow a process to get and set keyboard and pointer controls.

Allow a process to modify pointer button and key mappings.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_DGA

Allow a process to use the direct graphics access (DGA) X protocol extensions. Direct process access to the frame buffer is still required. Thus the process must have MAC and DAC privileges that allow access to the frame buffer, or the frame buffer must be allocated to the process.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_DOWNGRADE_SL

Allow a process to set the sensitivity label of a window resource to a sensitivity label that does not dominate the existing sensitivity label.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_FONTPATH

Allow a process to set a font path.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_MAC_READ

Allow a process to read from a window resource whose sensitivity label is not equal to the process sensitivity label.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_MAC_WRITE

Allow a process to create a window resource whose sensitivity label is not equal to the process sensitivity label. A newly created window property is created with the window's sensitivity label.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_SELECTION

Allow a process to request inter-window data moves without the intervention of the selection confirmer.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_WIN_UPGRADE_SL

Allow a process to set the sensitivity label of a window resource to a sensitivity label that dominates the existing sensitivity label.

This privilege is interpreted only if the system is configured with Trusted Extensions.

PRIV_XVM_CONTROL

Allows a process access to the xVM(5) control devices for managing guest domains and the hypervisor. This privilege is used only if booted into xVM on x86 platforms.

Of the privileges listed above, the privileges PRIV_FILE_LINK_ANY, PRIV_PROC_INFO, PRIV_PROC_SESSION, PRIV_PROC_FORK and PRIV_PROC_EXEC are considered "basic" privileges. These are privileges that used to be always available to unprivileged processes. By default, processes still have the basic privileges.

The privileges PRIV_PROC_SETID and PRIV_PROC_AUDIT must be present in the Limit set (see below) of a process in order for set-uid root execs to be successful, that is, get an effective UID of 0 and additional privileges.

The privilege implementation in Solaris extends the process credential with four privilege sets:

I, the inheritable set

The privileges inherited on exec.

P, the permitted set

The maximum set of privileges for the process.

E, the effective set

The privileges currently in effect.

L, the limit set

The upper bound of the privileges a process and its offspring can obtain. Changes to L take effect on the next exec.

The sets I, P and E are typically identical to the basic set of privileges for unprivileged processes. The limit set is typically the full set of privileges.

Each process has a Privilege Awareness State (PAS) that can take the value PA (privilege-aware) and NPA (not-PA). PAS is a transitional mechanism that allows a choice between full compatibility with the old superuser model and completely ignoring the effective UID.

To facilitate the discussion, we introduce the notion of "observed effective set" (oE) and "observed permitted set" (oP) and the implementation sets iE and iP.

A process becomes privilege-aware either by manipulating the effective, permitted, or limit privilege sets through setppriv(2) or by using setpflags(2). In all cases, oE and oP are invariant in the process of becoming privilege-aware. In the process of becoming privilege-aware, the following assignments take place:

iE = oE
iP = oP

When a process is privilege-aware, oE and oP are invariant under UID changes. When a process is not privilege-aware, oE and oP are observed as follows:

oE = euid == 0 ? L : iE
oP = (euid == 0 || ruid == 0 || suid == 0) ? L : iP

When a non-privilege-aware process has an effective UID of 0, it can exercise the privileges contained in its limit set, the upper bound of its privileges. If a non-privilege-aware process has any of the UIDs 0, it will appear to be capable of potentially exercising all privileges in L.

It is possible for a process to return to the non-privilege aware state using setpflags(). The kernel will always attempt this on exec(2). This operation is permitted only if the following conditions are met:

o If any of the UIDs is equal to 0, P must be equal to L.

o If the effective UID is equal to 0, E must be equal to L.

When a process gives up privilege awareness, the following assignments take place:

if (euid == 0) iE = L & I
if (any uid == 0) iP = L & I

The privileges obtained when not having a UID of 0 are the inheritable set of the process restricted by the limit set.

Only privileges in the process's (observed) effective privilege set allow the process to perform restricted operations. A process can use any of the privilege manipulation functions to add or remove privileges from the privilege sets. Privileges can be removed always. Only privileges found in the permitted set can be added to the effective and inheritable set. The limit set cannot grow. The inheritable set can be larger than the permitted set.

When a process performs an exec(2), the kernel will first try to relinquish privilege awareness before making the following privilege set modifications:

E' = P' = I' = L & I
L is unchanged

If a process has not manipulated its privileges, the privilege sets effectively remain the same, as E, P and I are already identical.

The limit set is enforced at exec time.

To run a non-privilege-aware application in a backward-compatible manner, a privilege-aware application should start the non-privilege-aware application with I=basic.

For most privileges, absence of the privilege simply results in a failure. In some instances, the absense of a privilege can cause system calls to behave differently. In other instances, the removal of a privilege can force a set-uid application to seriously malfunction. Privileges of this type are considered "unsafe". When a process is lacking any of the unsafe privileges from its limit set, the system will not honor the set-uid bit of set-uid root applications. The following unsafe privileges have been identified: proc_setid, sys_resource and proc_audit.  

Privilege Escalation

In certain circumstances, a single privilege could lead to a process gaining one or more additional privileges that were not explicitly granted to that process. To prevent such an escalation of privileges, the security policy will require explicit permission for those additional privileges.

Common examples of escalation are those mechanisms that allow modification of system resources through "raw'' interfaces; for example, changing kernel data structures through /dev/kmem or changing files through /dev/dsk/*. Escalation also occurs when a process controls processes with more privileges than the controlling process. A special case of this is manipulating or creating objects owned by UID 0 or trying to obtain UID 0 using setuid(2). The special treatment of UID 0 is needed because the UID 0 owns all system configuration files and ordinary file protection mechanisms allow processes with UID 0 to modify the system configuration. With appropriate file modifications, a given process running with an effective UID of 0 can gain all privileges.

In situations where a process might obtain UID 0, the security policy requires additional privileges, up to the full set of privileges. Such restrictions could be relaxed or removed at such time as additional mechanisms for protection of system files became available. There are no such mechanisms in the current Solaris release.

The use of UID 0 processes should be limited as much as possible. They should be replaced with programs running under a different UID but with exactly the privileges they need.

Daemons that never need to exec subprocesses should remove the PRIV_PROC_EXEC privilege from their permitted and limit sets.  

Assigned Privileges and Safeguards

When privileges are assigned to a user, the system administrator could give that user more powers than intended. The administrator should consider whether safeguards are needed. For example, if the PRIV_PROC_LOCK_MEMORY privilege is given to a user, the administrator should consider setting the project.max-locked-memory resource control as well, to prevent that user from locking all memory.  

Privilege Debugging

When a system call fails with a permission error, it is not always immediately obvious what caused the problem. To debug such a problem, you can use a tool called privilege debugging. When privilege debugging is enabled for a process, the kernel reports missing privileges on the controlling terminal of the process. (Enable debugging for a process with the -D option of ppriv(1).) Additionally, the administrator can enable system-wide privilege debugging by setting the system(4) variable priv_debug using:

set priv_debug = 1

On a running system, you can use mdb(1) to change this variable.  

Privilege Administration

The Solaris Management Console (see smc(1M)) is the preferred method of modifying privileges for a command. Use usermod(1M) or smrole(1M) to assign privileges to or modify privileges for, respectively, a user or a role. Use ppriv(1) to enumerate the privileges supported on a system and truss(1) to determine which privileges a program requires.  

SEE ALSO

mdb(1), ppriv(1), add_drv(1M), ifconfig(1M), lockd(1M), nfsd(1M), rem_drv(1M), smbd(1M), update_drv(1M), Intro(2), access(2), acct(2), acl(2), adjtime(2), audit(2), auditon(2), chmod(2), chown(2), chroot(2), creat(2), exec(2), fcntl(2), fork(2), fpathconf(2), getacct(2), getpflags(2), getppriv(2), getsid(2), kill(2), link(2), memcntl(2), mknod(2), mount(2), msgctl(2), nice(2), ntp_adjtime(2), open(2), p_online(2), priocntl(2), priocntlset(2), processor_bind(2), pset_bind(2), pset_create(2), readlink(2), resolvepath(2), rmdir(2), semctl(2), setauid(2), setegid(2), seteuid(2), setgid(2), setgroups(2), setpflags(2), setppriv(2), setrctl(2), setregid(2), setreuid(2), setrlimit(2), settaskid(2), setuid(2), shmctl(2), shmget(2), shmop(2), sigsend(2), stat(2), statvfs(2), stime(2), swapctl(2), sysinfo(2), uadmin(2), ulimit(2), umount(2), unlink(2), utime(2), utimes(2), bind(3SOCKET), door_ucred(3C), priv_addset(3C), priv_set(3C), priv_getbyname(3C), priv_getbynum(3C), priv_set_to_str(3C), priv_str_to_set(3C), socket(3SOCKET), t_bind(3NSL), timer_create(3C), ucred_get(3C), exec_attr(4), proc(4), system(4), user_attr(4), xVM(5), ddi_cred(9F), drv_priv(9F), priv_getbyname(9F), priv_policy(9F), priv_policy_choice(9F), priv_policy_only(9F)

System Administration Guide: Security Services

Index

NAME

DESCRIPTION

Privilege Escalation

Assigned Privileges and Safeguards

Privilege Debugging

Privilege Administration

SEE ALSO

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