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6.7 MAC Policy Entry Point Reference

6.7.1 General-Purpose Module Entry Points

6.7.1.1 mpo_init

void mpo_init(struct mac_policy_conf *conf);

Parameter Description Locking
conf MAC policy definition  

Policy load event. The policy list mutex is held, so sleep operations cannot be performed, and calls out to other kernel subsystems must be made with caution. If potentially sleeping memory allocations are required during policy initialization, they should be made using a separate module SYSINIT().

6.7.1.2 mpo_destroy

void mpo_destroy(struct mac_policy_conf *conf);

Parameter Description Locking
conf MAC policy definition  

Policy load event. The policy list mutex is held, so caution should be applied.

6.7.1.3 mpo_syscall

int mpo_syscall(struct thread *td, int call, void *arg);

Parameter Description Locking
td Calling thread  
call Policy-specific syscall number  
arg Pointer to syscall arguments  

This entry point provides a policy-multiplexed system call so that policies may provide additional services to user processes without registering specific system calls. The policy name provided during registration is used to demux calls from userland, and the arguments will be forwarded to this entry point. When implementing new services, security modules should be sure to invoke appropriate access control checks from the MAC framework as needed. For example, if a policy implements an augmented signal functionality, it should call the necessary signal access control checks to invoke the MAC framework and other registered policies.

Note: Modules must currently perform the copyin() of the syscall data on their own.

6.7.1.4 mpo_thread_userret

void mpo_thread_userret(struct thread *td);

Parameter Description Locking
td Returning thread  

This entry point permits policy modules to perform MAC-related events when a thread returns to user space, via a system call return, trap return, or otherwise. This is required for policies that have floating process labels, as it is not always possible to acquire the process lock at arbitrary points in the stack during system call processing; process labels might represent traditional authentication data, process history information, or other data. To employ this mechanism, intended changes to the process credential label may be stored in the p_label protected by a per-policy spin lock, and then set the per-thread TDF_ASTPENDING flag and per-process PS_MACPENDM flag to schedule a call to the userret entry point. From this entry point, the policy may create a replacement credential with less concern about the locking context. Policy writers are cautioned that event ordering relating to scheduling an AST and the AST being performed may be complex and interlaced in multithreaded applications.

6.7.2 Label Operations

6.7.2.1 mpo_init_bpfdesc_label

void mpo_init_bpfdesc_label(struct label *label);

Parameter Description Locking
label New label to apply  

Initialize the label on a newly instantiated bpfdesc (BPF descriptor). Sleeping is permitted.

6.7.2.2 mpo_init_cred_label

void mpo_init_cred_label(struct label *label);

Parameter Description Locking
label New label to initialize  

Initialize the label for a newly instantiated user credential. Sleeping is permitted.

6.7.2.3 mpo_init_devfsdirent_label

void mpo_init_devfsdirent_label(struct label *label);

Parameter Description Locking
label New label to apply  

Initialize the label on a newly instantiated devfs entry. Sleeping is permitted.

6.7.2.4 mpo_init_ifnet_label

void mpo_init_ifnet_label(struct label *label);

Parameter Description Locking
label New label to apply  

Initialize the label on a newly instantiated network interface. Sleeping is permitted.

6.7.2.5 mpo_init_ipq_label

void mpo_init_ipq_label(struct label *label, int flag);

Parameter Description Locking
label New label to apply  
flag Sleeping/non-sleeping malloc(9); see below  

Initialize the label on a newly instantiated IP fragment reassembly queue. The flag field may be one of M_WAITOK and M_NOWAIT, and should be employed to avoid performing a sleeping malloc(9) during this initialization call. IP fragment reassembly queue allocation frequently occurs in performance sensitive environments, and the implementation should be careful to avoid sleeping or long-lived operations. This entry point is permitted to fail resulting in the failure to allocate the IP fragment reassembly queue.

6.7.2.6 mpo_init_mbuf_label

void mpo_init_mbuf_label(int flag, struct label *label);

Parameter Description Locking
flag Sleeping/non-sleeping malloc(9); see below  
label Policy label to initialize  

Initialize the label on a newly instantiated mbuf packet header (mbuf). The flag field may be one of M_WAITOK and M_NOWAIT, and should be employed to avoid performing a sleeping malloc(9) during this initialization call. Mbuf allocation frequently occurs in performance sensitive environments, and the implementation should be careful to avoid sleeping or long-lived operations. This entry point is permitted to fail resulting in the failure to allocate the mbuf header.

6.7.2.7 mpo_init_mount_label

void mpo_init_mount_label(struct label *mntlabel, struct label *fslabel);

Parameter Description Locking
mntlabel Policy label to be initialized for the mount itself  
fslabel Policy label to be initialized for the file system  

Initialize the labels on a newly instantiated mount point. Sleeping is permitted.

6.7.2.8 mpo_init_mount_fs_label

void mpo_init_mount_fs_label(struct label *label);

Parameter Description Locking
label Label to be initialized  

Initialize the label on a newly mounted file system. Sleeping is permitted

6.7.2.9 mpo_init_pipe_label

void mpo_init_pipe_label(struct label*label);

Parameter Description Locking
label Label to be filled in  

Initialize a label for a newly instantiated pipe. Sleeping is permitted.

6.7.2.10 mpo_init_socket_label

void mpo_init_socket_label(struct label *label, int flag);

Parameter Description Locking
label New label to initialize  
flag malloc(9) flags  

Initialize a label for a newly instantiated socket. The flag field may be one of M_WAITOK and M_NOWAIT, and should be employed to avoid performing a sleeping malloc(9) during this initialization call.

6.7.2.11 mpo_init_socket_peer_label

void mpo_init_socket_peer_label(struct label *label, int flag);

Parameter Description Locking
label New label to initialize  
flag malloc(9) flags  

Initialize the peer label for a newly instantiated socket. The flag field may be one of M_WAITOK and M_NOWAIT, and should be employed to avoid performing a sleeping malloc(9) during this initialization call.

6.7.2.12 mpo_init_proc_label

void mpo_init_proc_label(struct label *label);

Parameter Description Locking
label New label to initialize  

Initialize the label for a newly instantiated process. Sleeping is permitted.

6.7.2.13 mpo_init_vnode_label

void mpo_init_vnode_label(struct label *label);

Parameter Description Locking
label New label to initialize  

Initialize the label on a newly instantiated vnode. Sleeping is permitted.

6.7.2.14 mpo_destroy_bpfdesc_label

void mpo_destroy_bpfdesc_label(struct label *label);

Parameter Description Locking
label bpfdesc label  

Destroy the label on a BPF descriptor. In this entry point a policy should free any internal storage associated with label so that it may be destroyed.

6.7.2.15 mpo_destroy_cred_label

void mpo_destroy_cred_label(struct label *label);

Parameter Description Locking
label Label being destroyed  

Destroy the label on a credential. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.16 mpo_destroy_devfsdirent_label

void mpo_destroy_devfsdirent_label(struct label *label);

Parameter Description Locking
label Label being destroyed  

Destroy the label on a devfs entry. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.17 mpo_destroy_ifnet_label

void mpo_destroy_ifnet_label(struct label *label);

Parameter Description Locking
label Label being destroyed  

Destroy the label on a removed interface. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.18 mpo_destroy_ipq_label

void mpo_destroy_ipq_label(struct label *label);

Parameter Description Locking
label Label being destroyed  

Destroy the label on an IP fragment queue. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.19 mpo_destroy_mbuf_label

void mpo_destroy_mbuf_label(struct label *label);

Parameter Description Locking
label Label being destroyed  

Destroy the label on an mbuf header. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.20 mpo_destroy_mount_label

void mpo_destroy_mount_label(struct label *label);

Parameter Description Locking
label Mount point label being destroyed  

Destroy the labels on a mount point. In this entry point, a policy module should free the internal storage associated with mntlabel so that they may be destroyed.

6.7.2.21 mpo_destroy_mount_label

void mpo_destroy_mount_label(struct label *mntlabel, struct label *fslabel);

Parameter Description Locking
mntlabel Mount point label being destroyed  
fslabel File system label being destroyed>  

Destroy the labels on a mount point. In this entry point, a policy module should free the internal storage associated with mntlabel and fslabel so that they may be destroyed.

6.7.2.22 mpo_destroy_socket_label

void mpo_destroy_socket_label(struct label *label);

Parameter Description Locking
label Socket label being destroyed  

Destroy the label on a socket. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.23 mpo_destroy_socket_peer_label

void mpo_destroy_socket_peer_label(struct label *peerlabel);

Parameter Description Locking
peerlabel Socket peer label being destroyed  

Destroy the peer label on a socket. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.24 mpo_destroy_pipe_label

void mpo_destroy_pipe_label(struct label *label);

Parameter Description Locking
label Pipe label  

Destroy the label on a pipe. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.25 mpo_destroy_proc_label

void mpo_destroy_proc_label(struct label *label);

Parameter Description Locking
label Process label  

Destroy the label on a process. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.26 mpo_destroy_vnode_label

void mpo_destroy_vnode_label(struct label *label);

Parameter Description Locking
label Process label  

Destroy the label on a vnode. In this entry point, a policy module should free any internal storage associated with label so that it may be destroyed.

6.7.2.27 mpo_copy_mbuf_label

void mpo_copy_mbuf_label(struct label *src, struct label *dest);

Parameter Description Locking
src Source label  
dest Destination label  

Copy the label information in src into dest.

6.7.2.28 mpo_copy_pipe_label

void mpo_copy_pipe_label(struct label *src, struct label *dest);

Parameter Description Locking
src Source label  
dest Destination label  

Copy the label information in src into dest.

6.7.2.29 mpo_copy_vnode_label

void mpo_copy_vnode_label(struct label *src, struct label *dest);

Parameter Description Locking
src Source label  
dest Destination label  

Copy the label information in src into dest.

6.7.2.30 mpo_externalize_cred_label

int mpo_externalize_cred_label(struct label *label, char *element_name, struct sbuf *sb, int *claimed);

Parameter Description Locking
label Label to be externalized  
element_name Name of the policy whose label should be externalized  
sb String buffer to be filled with a text representation of label  
claimed Should be incremented when element_data can be filled in.  

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' externalize entry points will be called, so the implementation should check the contents of element_name before attempting to fill in sb. If element_name does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in element_data, *claimed should be incremented.

6.7.2.31 mpo_externalize_ifnet_label

int mpo_externalize_ifnet_label(struct label *label, char *element_name, struct sbuf *sb, int *claimed);

Parameter Description Locking
label Label to be externalized  
element_name Name of the policy whose label should be externalized  
sb String buffer to be filled with a text representation of label  
claimed Should be incremented when element_data can be filled in.  

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' externalize entry points will be called, so the implementation should check the contents of element_name before attempting to fill in sb. If element_name does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in element_data, *claimed should be incremented.

6.7.2.32 mpo_externalize_pipe_label

int mpo_externalize_pipe_label(struct label *label, char *element_name, struct sbuf *sb, int *claimed);

Parameter Description Locking
label Label to be externalized  
element_name Name of the policy whose label should be externalized  
sb String buffer to be filled with a text representation of label  
claimed Should be incremented when element_data can be filled in.  

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' externalize entry points will be called, so the implementation should check the contents of element_name before attempting to fill in sb. If element_name does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in element_data, *claimed should be incremented.

6.7.2.33 mpo_externalize_socket_label

int mpo_externalize_socket_label(struct label *label, char *element_name, struct sbuf *sb, int *claimed);

Parameter Description Locking
label Label to be externalized  
element_name Name of the policy whose label should be externalized  
sb String buffer to be filled with a text representation of label  
claimed Should be incremented when element_data can be filled in.  

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' externalize entry points will be called, so the implementation should check the contents of element_name before attempting to fill in sb. If element_name does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in element_data, *claimed should be incremented.

6.7.2.34 mpo_externalize_socket_peer_label

int mpo_externalize_socket_peer_label(struct label *label, char *element_name, struct sbuf *sb, int *claimed);

Parameter Description Locking
label Label to be externalized  
element_name Name of the policy whose label should be externalized  
sb String buffer to be filled with a text representation of label  
claimed Should be incremented when element_data can be filled in.  

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' externalize entry points will be called, so the implementation should check the contents of element_name before attempting to fill in sb. If element_name does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in element_data, *claimed should be incremented.

6.7.2.35 mpo_externalize_vnode_label

int mpo_externalize_vnode_label(struct label *label, char *element_name, struct sbuf *sb, int *claimed);

Parameter Description Locking
label Label to be externalized  
element_name Name of the policy whose label should be externalized  
sb String buffer to be filled with a text representation of label  
claimed Should be incremented when element_data can be filled in.  

Produce an externalized label based on the label structure passed. An externalized label consists of a text representation of the label contents that can be used with userland applications and read by the user. Currently, all policies' externalize entry points will be called, so the implementation should check the contents of element_name before attempting to fill in sb. If element_name does not match the name of your policy, simply return 0. Only return nonzero if an error occurs while externalizing the label data. Once the policy fills in element_data, *claimed should be incremented.

6.7.2.36 mpo_internalize_cred_label

int mpo_internalize_cred_label(struct label *label, char *element_name, char *element_data, int *claimed);

Parameter Description Locking
label Label to be filled in  
element_name Name of the policy whose label should be internalized  
element_data Text data to be internalized  
claimed Should be incremented when data can be successfully internalized.  

Produce an internal label structure based on externalized label data in text format. Currently, all policies' internalize entry points are called when internalization is requested, so the implementation should compare the contents of element_name to its own name in order to be sure it should be internalizing the data in element_data. Just as in the externalize entry points, the entry point should return 0 if element_name does not match its own name, or when data can successfully be internalized, in which case *claimed should be incremented.

6.7.2.37 mpo_internalize_ifnet_label

int mpo_internalize_ifnet_label(struct label *label, char *element_name, char *element_data, int *claimed);

Parameter Description Locking
label Label to be filled in  
element_name Name of the policy whose label should be internalized  
element_data Text data to be internalized  
claimed Should be incremented when data can be successfully internalized.  

Produce an internal label structure based on externalized label data in text format. Currently, all policies' internalize entry points are called when internalization is requested, so the implementation should compare the contents of element_name to its own name in order to be sure it should be internalizing the data in element_data. Just as in the externalize entry points, the entry point should return 0 if element_name does not match its own name, or when data can successfully be internalized, in which case *claimed should be incremented.

6.7.2.38 mpo_internalize_pipe_label

int mpo_internalize_pipe_label(struct label *label, char *element_name, char *element_data, int *claimed);

Parameter Description Locking
label Label to be filled in  
element_name Name of the policy whose label should be internalized  
element_data Text data to be internalized  
claimed Should be incremented when data can be successfully internalized.  

Produce an internal label structure based on externalized label data in text format. Currently, all policies' internalize entry points are called when internalization is requested, so the implementation should compare the contents of element_name to its own name in order to be sure it should be internalizing the data in element_data. Just as in the externalize entry points, the entry point should return 0 if element_name does not match its own name, or when data can successfully be internalized, in which case *claimed should be incremented.

6.7.2.39 mpo_internalize_socket_label

int mpo_internalize_socket_label(struct label *label, char *element_name, char *element_data, int *claimed);

Parameter Description Locking
label Label to be filled in  
element_name Name of the policy whose label should be internalized  
element_data Text data to be internalized  
claimed Should be incremented when data can be successfully internalized.  

Produce an internal label structure based on externalized label data in text format. Currently, all policies' internalize entry points are called when internalization is requested, so the implementation should compare the contents of element_name to its own name in order to be sure it should be internalizing the data in element_data. Just as in the externalize entry points, the entry point should return 0 if element_name does not match its own name, or when data can successfully be internalized, in which case *claimed should be incremented.

6.7.2.40 mpo_internalize_vnode_label

int mpo_internalize_vnode_label(struct label *label, char *element_name, char *element_data, int *claimed);

Parameter Description Locking
label Label to be filled in  
element_name Name of the policy whose label should be internalized  
element_data Text data to be internalized  
claimed Should be incremented when data can be successfully internalized.  

Produce an internal label structure based on externalized label data in text format. Currently, all policies' internalize entry points are called when internalization is requested, so the implementation should compare the contents of element_name to its own name in order to be sure it should be internalizing the data in element_data. Just as in the externalize entry points, the entry point should return 0 if element_name does not match its own name, or when data can successfully be internalized, in which case *claimed should be incremented.

6.7.3 Label Events

This class of entry points is used by the MAC framework to permit policies to maintain label information on kernel objects. For each labeled kernel object of interest to a MAC policy, entry points may be registered for relevant life cycle events. All objects implement initialization, creation, and destruction hooks. Some objects will also implement relabeling, allowing user processes to change the labels on objects. Some objects will also implement object-specific events, such as label events associated with IP reassembly. A typical labeled object will have the following life cycle of entry points:

Label initialization          o
(object-specific wait)         \
Label creation                  o
                                 \
Relabel events,                   o--<--.
Various object-specific,          |     |
Access control events             ~-->--o
                                         \
Label destruction                         o

Label initialization permits policies to allocate memory and set initial values for labels without context for the use of the object. The label slot allocated to a policy will be zeroed by default, so some policies may not need to perform initialization.

Label creation occurs when the kernel structure is associated with an actual kernel object. For example, Mbufs may be allocated and remain unused in a pool until they are required. mbuf allocation causes label initialization on the mbuf to take place, but mbuf creation occurs when the mbuf is associated with a datagram. Typically, context will be provided for a creation event, including the circumstances of the creation, and labels of other relevant objects in the creation process. For example, when an mbuf is created from a socket, the socket and its label will be presented to registered policies in addition to the new mbuf and its label. Memory allocation in creation events is discouraged, as it may occur in performance sensitive ports of the kernel; in addition, creation calls are not permitted to fail so a failure to allocate memory cannot be reported.

Object specific events do not generally fall into the other broad classes of label events, but will generally provide an opportunity to modify or update the label on an object based on additional context. For example, the label on an IP fragment reassembly queue may be updated during the MAC_UPDATE_IPQ entry point as a result of the acceptance of an additional mbuf to that queue.

Access control events are discussed in detail in the following section.

Label destruction permits policies to release storage or state associated with a label during its association with an object so that the kernel data structures supporting the object may be reused or released.

In addition to labels associated with specific kernel objects, an additional class of labels exists: temporary labels. These labels are used to store update information submitted by user processes. These labels are initialized and destroyed as with other label types, but the creation event is MAC_INTERNALIZE, which accepts a user label to be converted to an in-kernel representation.

6.7.3.1 File System Object Labeling Event Operations

6.7.3.1.1 mpo_associate_vnode_devfs

void mpo_associate_vnode_devfs(struct mount *mp, struct label *fslabel, struct devfs_dirent *de, struct label *delabel, struct vnode *vp, struct label *vlabel);

Parameter Description Locking
mp Devfs mount point  
fslabel Devfs file system label (mp->mnt_fslabel)  
de Devfs directory entry  
delabel Policy label associated with de  
vp vnode associated with de  
vlabel Policy label associated with vp  

Fill in the label (vlabel) for a newly created devfs vnode based on the devfs directory entry passed in de and its label.

6.7.3.1.2 mpo_associate_vnode_extattr

int mpo_associate_vnode_extattr(struct mount *mp, struct label *fslabel, struct vnode *vp, struct label *vlabel);

Parameter Description Locking
mp File system mount point  
fslabel File system label  
vp Vnode to label  
vlabel Policy label associated with vp  

Attempt to retrieve the label for vp from the file system extended attributes. Upon success, the value 0 is returned. Should extended attribute retrieval not be supported, an accepted fallback is to copy fslabel into vlabel. In the event of an error, an appropriate value for errno should be returned.

6.7.3.1.3 mpo_associate_vnode_singlelabel

void mpo_associate_vnode_singlelabel(struct mount *mp, struct label *fslabel, struct vnode *vp, struct label *vlabel);

Parameter Description Locking
mp File system mount point  
fslabel File system label  
vp Vnode to label  
vlabel Policy label associated with vp  

On non-multilabel file systems, this entry point is called to set the policy label for vp based on the file system label, fslabel.

6.7.3.1.4 mpo_create_devfs_device

void mpo_create_devfs_device(dev_t dev, struct devfs_dirent *devfs_dirent, struct label *label);

Parameter Description Locking
dev Device corresponding with devfs_dirent  
devfs_dirent Devfs directory entry to be labeled.  
label Label for devfs_dirent to be filled in.  

Fill out the label on a devfs_dirent being created for the passed device. This call will be made when the device file system is mounted, regenerated, or a new device is made available.

6.7.3.1.5 mpo_create_devfs_directory

void mpo_create_devfs_directory(char *dirname, int dirnamelen, struct devfs_dirent *devfs_dirent, struct label *label);

Parameter Description Locking
dirname Name of directory being created  
namelen Length of string dirname  
devfs_dirent Devfs directory entry for directory being created.  

Fill out the label on a devfs_dirent being created for the passed directory. This call will be made when the device file system is mounted, regenerated, or a new device requiring a specific directory hierarchy is made available.

6.7.3.1.6 mpo_create_devfs_symlink

void mpo_create_devfs_symlink(struct ucred *cred, struct mount *mp, struct devfs_dirent *dd, struct label *ddlabel, struct devfs_dirent *de, struct label *delabel);

Parameter Description Locking
cred Subject credential  
mp Devfs mount point  
dd Link destination  
ddlabel Label associated with dd  
de Symlink entry  
delabel Label associated with de  

Fill in the label (delabel) for a newly created devfs(5) symbolic link entry.

6.7.3.1.7 mpo_create_vnode_extattr

int mpo_create_vnode_extattr(struct ucred *cred, struct mount *mp, struct label *fslabel, struct vnode *dvp, struct label *dlabel, struct vnode *vp, struct label *vlabel, struct componentname *cnp);

Parameter Description Locking
cred Subject credential  
mount File system mount point  
label File system label  
dvp Parent directory vnode  
dlabel Label associated with dvp  
vp Newly created vnode  
vlabel Policy label associated with vp  
cnp Component name for vp  

Write out the label for vp to the appropriate extended attribute. If the write succeeds, fill in vlabel with the label, and return 0. Otherwise, return an appropriate error.

6.7.3.1.8 mpo_create_mount

void mpo_create_mount(struct ucred *cred, struct mount *mp, struct label *mnt, struct label *fslabel);

Parameter Description Locking
cred Subject credential  
mp Object; file system being mounted  
mntlabel Policy label to be filled in for mp  
fslabel Policy label for the file system mp mounts.  

Fill out the labels on the mount point being created by the passed subject credential. This call will be made when a new file system is mounted.

6.7.3.1.9 mpo_create_root_mount

void mpo_create_root_mount(struct ucred *cred, struct mount *mp, struct label *mntlabel, struct label *fslabel);

Parameter Description Locking
See Section 6.7.3.1.8.

Fill out the labels on the mount point being created by the passed subject credential. This call will be made when the root file system is mounted, after mpo_create_mount;.

6.7.3.1.10 mpo_relabel_vnode

void mpo_relabel_vnode(struct ucred *cred, struct vnode *vp, struct label *vnodelabel, struct label *newlabel);

Parameter Description Locking
cred Subject credential  
vp vnode to relabel  
vnodelabel Existing policy label for vp  
newlabel New, possibly partial label to replace vnodelabel  

Update the label on the passed vnode given the passed update vnode label and the passed subject credential.

6.7.3.1.11 mpo_setlabel_vnode_extattr

int mpo_setlabel_vnode_extattr(struct ucred *cred, struct vnode *vp, struct label *vlabel, struct label *intlabel);

Parameter Description Locking
cred Subject credential  
vp Vnode for which the label is being written  
vlabel Policy label associated with vp  
intlabel Label to write out  

Write out the policy from intlabel to an extended attribute. This is called from vop_stdcreatevnode_ea.

6.7.3.1.12 mpo_update_devfsdirent

void mpo_update_devfsdirent(struct devfs_dirent *devfs_dirent, struct label *direntlabel, struct vnode *vp, struct label *vnodelabel);

Parameter Description Locking
devfs_dirent Object; devfs directory entry  
direntlabel Policy label for devfs_dirent to be updated.  
vp Parent vnode Locked
vnodelabel Policy label for vp  

Update the devfs_dirent label from the passed devfs vnode label. This call will be made when a devfs vnode has been successfully relabeled to commit the label change such that it lasts even if the vnode is recycled. It will also be made when when a symlink is created in devfs, following a call to mac_vnode_create_from_vnode to initialize the vnode label.

6.7.3.2 IPC Object Labeling Event Operations

6.7.3.2.1 mpo_create_mbuf_from_socket

void mpo_create_mbuf_from_socket(struct socket *so, struct label *socketlabel, struct mbuf *m, struct label *mbuflabel);

Parameter Description Locking
socket Socket Socket locking WIP
socketlabel Policy label for socket  
m Object; mbuf  
mbuflabel Policy label to fill in for m  

Set the label on a newly created mbuf header from the passed socket label. This call is made when a new datagram or message is generated by the socket and stored in the passed mbuf.

6.7.3.2.2 mpo_create_pipe

void mpo_create_pipe(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);

Parameter Description Locking
cred Subject credential  
pipe Pipe  
pipelabel Policy label associated with pipe  

Set the label on a newly created pipe from the passed subject credential. This call is made when a new pipe is created.

6.7.3.2.3 mpo_create_socket

void mpo_create_socket(struct ucred *cred, struct socket *so, struct label *socketlabel);

Parameter Description Locking
cred Subject credential Immutable
so Object; socket to label  
socketlabel Label to fill in for so  

Set the label on a newly created socket from the passed subject credential. This call is made when a socket is created.

6.7.3.2.4 mpo_create_socket_from_socket

void mpo_create_socket_from_socket(struct socket *oldsocket, struct label *oldsocketlabel, struct socket *newsocket, struct label *newsocketlabel);

Parameter Description Locking
oldsocket Listening socket  
oldsocketlabel Policy label associated with oldsocket  
newsocket New socket  
newsocketlabel Policy label associated with newsocketlabel  

Label a socket, newsocket, newly accept(2)ed, based on the listen(2) socket, oldsocket.

6.7.3.2.5 mpo_relabel_pipe

void mpo_relabel_pipe(struct ucred *cred, struct pipe *pipe, struct label *oldlabel, struct label *newlabel);

Parameter Description Locking
cred Subject credential  
pipe Pipe  
oldlabel Current policy label associated with pipe  
newlabel Policy label update to apply to pipe  

Apply a new label, newlabel, to pipe.

6.7.3.2.6 mpo_relabel_socket

void mpo_relabel_socket(struct ucred *cred, struct socket *so, struct label *oldlabel, struct label *newlabel);

Parameter Description Locking
cred Subject credential Immutable
so Object; socket  
oldlabel Current label for so  
newlabel Label update for so  

Update the label on a socket from the passed socket label update.

6.7.3.2.7 mpo_set_socket_peer_from_mbuf

void mpo_set_socket_peer_from_mbuf(struct mbuf *mbuf, struct label *mbuflabel, struct label *oldlabel, struct label *newlabel);

Parameter Description Locking
mbuf First datagram received over socket  
mbuflabel Label for mbuf  
oldlabel Current label for the socket  
newlabel Policy label to be filled out for the socket  

Set the peer label on a stream socket from the passed mbuf label. This call will be made when the first datagram is received by the stream socket, with the exception of Unix domain sockets.

6.7.3.2.8 mpo_set_socket_peer_from_socket

void mpo_set_socket_peer_from_socket(struct socket *oldsocket, struct label *oldsocketlabel, struct socket *newsocket, struct label *newsocketpeerlabel);

Parameter Description Locking
oldsocket Local socket  
oldsocketlabel Policy label for oldsocket  
newsocket Peer socket  
newsocketpeerlabel Policy label to fill in for newsocket  

Set the peer label on a stream UNIX domain socket from the passed remote socket endpoint. This call will be made when the socket pair is connected, and will be made for both endpoints.

6.7.3.3 Network Object Labeling Event Operations

6.7.3.3.1 mpo_create_bpfdesc

void mpo_create_bpfdesc(struct ucred *cred, struct bpf_d *bpf_d, struct label *bpflabel);

Parameter Description Locking
cred Subject credential Immutable
bpf_d Object; bpf descriptor  
bpf Policy label to be filled in for bpf_d  

Set the label on a newly created BPF descriptor from the passed subject credential. This call will be made when a BPF device node is opened by a process with the passed subject credential.

6.7.3.3.2 mpo_create_ifnet

void mpo_create_ifnet(struct ifnet *ifnet, struct label *ifnetlabel);

Parameter Description Locking
ifnet Network interface  
ifnetlabel Policy label to fill in for ifnet  

Set the label on a newly created interface. This call may be made when a new physical interface becomes available to the system, or when a pseudo-interface is instantiated during the boot or as a result of a user action.

6.7.3.3.3 mpo_create_ipq

void mpo_create_ipq(struct mbuf *fragment, struct label *fragmentlabel, struct ipq *ipq, struct label *ipqlabel);

Parameter Description Locking
fragment First received IP fragment  
fragmentlabel Policy label for fragment  
ipq IP reassembly queue to be labeled  
ipqlabel Policy label to be filled in for ipq  

Set the label on a newly created IP fragment reassembly queue from the mbuf header of the first received fragment.

6.7.3.3.4 mpo_create_datagram_from_ipq

void mpo_create_create_datagram_from_ipq(struct ipq *ipq, struct label *ipqlabel, struct mbuf *datagram, struct label *datagramlabel);

Parameter Description Locking
ipq IP reassembly queue  
ipqlabel Policy label for ipq  
datagram Datagram to be labeled  
datagramlabel Policy label to be filled in for datagramlabel  

Set the label on a newly reassembled IP datagram from the IP fragment reassembly queue from which it was generated.

6.7.3.3.5 mpo_create_fragment

void mpo_create_fragment(struct mbuf *datagram, struct label *datagramlabel, struct mbuf *fragment, struct label *fragmentlabel);

Parameter Description Locking
datagram Datagram  
datagramlabel Policy label for datagram  
fragment Fragment to be labeled  
fragmentlabel Policy label to be filled in for datagram  

Set the label on the mbuf header of a newly created IP fragment from the label on the mbuf header of the datagram it was generate from.

6.7.3.3.6 mpo_create_mbuf_from_mbuf

void mpo_create_mbuf_from_mbuf(struct mbuf *oldmbuf, struct label *oldmbuflabel, struct mbuf *newmbuf, struct label *newmbuflabel);

Parameter Description Locking
oldmbuf Existing (source) mbuf  
oldmbuflabel Policy label for oldmbuf  
newmbuf New mbuf to be labeled  
newmbuflabel Policy label to be filled in for newmbuf  

Set the label on the mbuf header of a newly created datagram from the mbuf header of an existing datagram. This call may be made in a number of situations, including when an mbuf is re-allocated for alignment purposes.

6.7.3.3.7 mpo_create_mbuf_linklayer

void mpo_create_mbuf_linklayer(struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *mbuf, struct label *mbuflabel);

Parameter Description Locking
ifnet Network interface  
ifnetlabel Policy label for ifnet  
mbuf mbuf header for new datagram  
mbuflabel Policy label to be filled in for mbuf  

Set the label on the mbuf header of a newly created datagram generated for the purposes of a link layer response for the passed interface. This call may be made in a number of situations, including for ARP or ND6 responses in the IPv4 and IPv6 stacks.

6.7.3.3.8 mpo_create_mbuf_from_bpfdesc

void mpo_create_mbuf_from_bpfdesc(struct bpf_d *bpf_d, struct label *bpflabel, struct mbuf *mbuf, struct label *mbuflabel);

Parameter Description Locking
bpf_d BPF descriptor  
bpflabel Policy label for bpflabel  
mbuf New mbuf to be labeled  
mbuflabel Policy label to fill in for mbuf  

Set the label on the mbuf header of a newly created datagram generated using the passed BPF descriptor. This call is made when a write is performed to the BPF device associated with the passed BPF descriptor.

6.7.3.3.9 mpo_create_mbuf_from_ifnet

void mpo_create_mbuf_from_ifnet(struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *mbuf, struct label *mbuflabel);

Parameter Description Locking
ifnet Network interface  
ifnetlabel Policy label for ifnetlabel  
mbuf mbuf header for new datagram  
mbuflabel Policy label to be filled in for mbuf  

Set the label on the mbuf header of a newly created datagram generated from the passed network interface.

6.7.3.3.10 mpo_create_mbuf_multicast_encap

void mpo_create_mbuf_multicast_encap(struct mbuf *oldmbuf, struct label *oldmbuflabel, struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *newmbuf, struct label *newmbuflabel);

Parameter Description Locking
oldmbuf mbuf header for existing datagram  
oldmbuflabel Policy label for oldmbuf  
ifnet Network interface  
ifnetlabel Policy label for ifnet  
newmbuf mbuf header to be labeled for new datagram  
newmbuflabel Policy label to be filled in for newmbuf  

Set the label on the mbuf header of a newly created datagram generated from the existing passed datagram when it is processed by the passed multicast encapsulation interface. This call is made when an mbuf is to be delivered using the virtual interface.

6.7.3.3.11 mpo_create_mbuf_netlayer

void mpo_create_mbuf_netlayer(struct mbuf *oldmbuf, struct label *oldmbuflabel, struct mbuf *newmbuf, struct label *newmbuflabel);

Parameter Description Locking
oldmbuf Received datagram  
oldmbuflabel Policy label for oldmbuf  
newmbuf Newly created datagram  
newmbuflabel Policy label for newmbuf  

Set the label on the mbuf header of a newly created datagram generated by the IP stack in response to an existing received datagram (oldmbuf). This call may be made in a number of situations, including when responding to ICMP request datagrams.

6.7.3.3.12 mpo_fragment_match

int mpo_fragment_match(struct mbuf *fragment, struct label *fragmentlabel, struct ipq *ipq, struct label *ipqlabel);

Parameter Description Locking
fragment IP datagram fragment  
fragmentlabel Policy label for fragment  
ipq IP fragment reassembly queue  
ipqlabel Policy label for ipq  

Determine whether an mbuf header containing an IP datagram (fragment) fragment matches the label of the passed IP fragment reassembly queue (ipq). Return (1) for a successful match, or (0) for no match. This call is made when the IP stack attempts to find an existing fragment reassembly queue for a newly received fragment; if this fails, a new fragment reassembly queue may be instantiated for the fragment. Policies may use this entry point to prevent the reassembly of otherwise matching IP fragments if policy does not permit them to be reassembled based on the label or other information.

6.7.3.3.13 mpo_relabel_ifnet

void mpo_relabel_ifnet(struct ucred *cred, struct ifnet *ifnet, struct label *ifnetlabel, struct label *newlabel);

Parameter Description Locking
cred Subject credential  
ifnet Object; Network interface  
ifnetlabel Policy label for ifnet  
newlabel Label update to apply to ifnet  

Update the label of network interface, ifnet, based on the passed update label, newlabel, and the passed subject credential, cred.

6.7.3.3.14 mpo_update_ipq

void mpo_update_ipq(struct mbuf *fragment, struct label *fragmentlabel, struct ipq *ipq, struct label *ipqlabel);

Parameter Description Locking
mbuf IP fragment  
mbuflabel Policy label for mbuf  
ipq IP fragment reassembly queue  
ipqlabel Policy label to be updated for ipq  

Update the label on an IP fragment reassembly queue (ipq) based on the acceptance of the passed IP fragment mbuf header (mbuf).

6.7.3.4 Process Labeling Event Operations

6.7.3.4.1 mpo_create_cred

void mpo_create_cred(struct ucred *parent_cred, struct ucred *child_cred);

Parameter Description Locking
parent_cred Parent subject credential  
child_cred Child subject credential  

Set the label of a newly created subject credential from the passed subject credential. This call will be made when crcopy(9) is invoked on a newly created struct ucred. This call should not be confused with a process forking or creation event.

6.7.3.4.2 mpo_execve_transition

void mpo_execve_transition(struct ucred *old, struct ucred *new, struct vnode *vp, struct label *vnodelabel);

Parameter Description Locking
old Existing subject credential Immutable
new New subject credential to be labeled  
vp File to execute Locked
vnodelabel Policy label for vp  

Update the label of a newly created subject credential (new) from the passed existing subject credential (old) based on a label transition caused by executing the passed vnode (vp). This call occurs when a process executes the passed vnode and one of the policies returns a success from the mpo_execve_will_transition entry point. Policies may choose to implement this call simply by invoking mpo_create_cred and passing the two subject credentials so as not to implement a transitioning event. Policies should not leave this entry point unimplemented if they implement mpo_create_cred, even if they do not implement mpo_execve_will_transition.

6.7.3.4.3 mpo_execve_will_transition

int mpo_execve_will_transition(struct ucred *old, struct vnode *vp, struct label *vnodelabel);

Parameter Description Locking
old Subject credential prior to execve(2) Immutable
vp File to execute  
vnodelabel Policy label for vp  

Determine whether the policy will want to perform a transition event as a result of the execution of the passed vnode by the passed subject credential. Return 1 if a transition is required, 0 if not. Even if a policy returns 0, it should behave correctly in the presence of an unexpected invocation of mpo_execve_transition, as that call may happen as a result of another policy requesting a transition.

6.7.3.4.4 mpo_create_proc0

void mpo_create_proc0(struct ucred *cred);

Parameter Description Locking
cred Subject credential to be filled in  

Create the subject credential of process 0, the parent of all kernel processes.

6.7.3.4.5 mpo_create_proc1

void mpo_create_proc1(struct ucred *cred);

Parameter Description Locking
cred Subject credential to be filled in  

Create the subject credential of process 1, the parent of all user processes.

6.7.3.4.6 mpo_relabel_cred

void mpo_relabel_cred(struct ucred *cred, struct label *newlabel);

Parameter Description Locking
cred Subject credential  
newlabel Label update to apply to cred  

Update the label on a subject credential from the passed update label.

6.7.4 Access Control Checks

Access control entry points permit policy modules to influence access control decisions made by the kernel. Generally, although not always, arguments to an access control entry point will include one or more authorizing credentials, information (possibly including a label) for any other objects involved in the operation. An access control entry point may return 0 to permit the operation, or an errno(2) error value. The results of invoking the entry point across various registered policy modules will be composed as follows: if all modules permit the operation to succeed, success will be returned. If one or modules returns a failure, a failure will be returned. If more than one module returns a failure, the errno value to return to the user will be selected using the following precedence, implemented by the error_select() function in kern_mac.c:

Most precedence EDEADLK
  EINVAL
  ESRCH
  EACCES
Least precedence EPERM

If none of the error values returned by all modules are listed in the precedence chart then an arbitrarily selected value from the set will be returned. In general, the rules provide precedence to errors in the following order: kernel failures, invalid arguments, object not present, access not permitted, other.

6.7.4.1 mpo_check_bpfdesc_receive

int mpo_check_bpfdesc_receive(struct bpf_d *bpf_d, struct label *bpflabel, struct ifnet *ifnet, struct label *ifnetlabel);

Parameter Description Locking
bpf_d Subject; BPF descriptor  
bpflabel Policy label for bpf_d  
ifnet Object; network interface  
ifnetlabel Policy label for ifnet  

Determine whether the MAC framework should permit datagrams from the passed interface to be delivered to the buffers of the passed BPF descriptor. Return (0) for success, or an errno value for failure Suggested failure: EACCES for label mismatches, EPERM for lack of privilege.

6.7.4.2 mpo_check_kenv_dump

int mpo_check_kenv_dump(struct ucred *cred);

Parameter Description Locking
cred Subject credential  

Determine whether the subject should be allowed to retrieve the kernel environment (see kenv(2)).

6.7.4.3 mpo_check_kenv_get

int mpo_check_kenv_get(struct ucred *cred, char *name);

Parameter Description Locking
cred Subject credential  
name Kernel environment variable name  

Determine whether the subject should be allowed to retrieve the value of the specified kernel environment variable.

6.7.4.4 mpo_check_kenv_set

int mpo_check_kenv_set(struct ucred *cred, char *name);

Parameter Description Locking
cred Subject credential  
name Kernel environment variable name  

Determine whether the subject should be allowed to set the specified kernel environment variable.

6.7.4.5 mpo_check_kenv_unset

int mpo_check_kenv_unset(struct ucred *cred, char *name);

Parameter Description Locking
cred Subject credential  
name Kernel environment variable name  

Determine whether the subject should be allowed to unset the specified kernel environment variable.

6.7.4.6 mpo_check_kld_load

int mpo_check_kld_load(struct ucred *cred, struct vnode *vp, struct label *vlabel);

Parameter Description Locking
cred Subject credential  
vp Kernel module vnode  
vlabel Label associated with vp  

Determine whether the subject should be allowed to load the specified module file.

6.7.4.7 mpo_check_kld_stat

int mpo_check_kld_stat(struct ucred *cred);

Parameter Description Locking
cred Subject credential  

Determine whether the subject should be allowed to retrieve a list of loaded kernel module files and associated statistics.

6.7.4.8 mpo_check_kld_unload

int mpo_check_kld_unload(struct ucred *cred);

Parameter Description Locking
cred Subject credential  

Determine whether the subject should be allowed to unload a kernel module.

6.7.4.9 mpo_check_pipe_ioctl

int mpo_check_pipe_ioctl(struct ucred *cred, struct pipe *pipe, struct label *pipelabel, unsigned long cmd, void *data);

Parameter Description Locking
cred Subject credential  
pipe Pipe  
pipelabel Policy label associated with pipe  
cmd ioctl(2) command  
data ioctl(2) data  

Determine whether the subject should be allowed to make the specified ioctl(2) call.

6.7.4.10 mpo_check_pipe_poll

int mpo_check_pipe_poll(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);

Parameter Description Locking
cred Subject credential  
pipe Pipe  
pipelabel Policy label associated with pipe  

Determine whether the subject should be allowed to poll pipe.

6.7.4.11 mpo_check_pipe_read

int mpo_check_pipe_read(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);

Parameter Description Locking
cred Subject credential  
pipe Pipe  
pipelabel Policy label associated with pipe  

Determine whether the subject should be allowed read access to pipe.

6.7.4.12 mpo_check_pipe_relabel

int mpo_check_pipe_relabel(struct ucred *cred, struct pipe *pipe, struct label *pipelabel, struct label *newlabel);

Parameter Description Locking
cred Subject credential  
pipe Pipe  
pipelabel Current policy label associated with pipe  
newlabel Label update to pipelabel  

Determine whether the subject should be allowed to relabel pipe.

6.7.4.13 mpo_check_pipe_stat

int mpo_check_pipe_stat(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);

Parameter Description Locking
cred Subject credential  
pipe Pipe  
pipelabel Policy label associated with pipe  

Determine whether the subject should be allowed to retrieve statistics related to pipe.

6.7.4.14 mpo_check_pipe_write

int mpo_check_pipe_write(struct ucred *cred, struct pipe *pipe, struct label *pipelabel);

Parameter Description Locking
cred Subject credential  
pipe Pipe  
pipelabel Policy label associated with pipe  

Determine whether the subject should be allowed to write to pipe.

6.7.4.15 mpo_check_socket_bind

int mpo_check_socket_bind(struct ucred *cred, struct socket *socket, struct label *socketlabel, struct sockaddr *sockaddr);

Parameter Description Locking
cred Subject credential  
socket Socket to be bound  
socketlabel Policy label for socket  
sockaddr Address of socket  

6.7.4.16 mpo_check_socket_connect

int mpo_check_socket_connect(struct ucred *cred, struct socket *socket, struct label *socketlabel, struct sockaddr *sockaddr);

Parameter Description Locking
cred Subject credential  
socket Socket to be connected  
socketlabel Policy label for socket  
sockaddr Address of socket  

Determine whether the subject credential (cred) can connect the passed socket (socket) to the passed socket address (sockaddr). Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege.

6.7.4.17 mpo_check_socket_receive

int mpo_check_socket_receive(struct ucred *cred, struct socket *so, struct label *socketlabel);

Parameter Description Locking
cred Subject credential  
so Socket  
socketlabel Policy label associated with so  

Determine whether the subject should be allowed to receive information from the socket so.

6.7.4.18 mpo_check_socket_send

int mpo_check_socket_send(struct ucred *cred, struct socket *so, struct label *socketlabel);

Parameter Description Locking
cred Subject credential  
so Socket  
socketlabel Policy label associated with so  

Determine whether the subject should be allowed to send information across the socket so.

6.7.4.19 mpo_check_cred_visible

int mpo_check_cred_visible(struct ucred *u1, struct ucred *u2);

Parameter Description Locking
u1 Subject credential  
u2 Object credential  

Determine whether the subject credential u1 can “see” other subjects with the passed subject credential u2. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege, or ESRCH to hide visibility. This call may be made in a number of situations, including inter-process status sysctls used by ps, and in procfs lookups.

6.7.4.20 mpo_check_socket_visible

int mpo_check_socket_visible(struct ucred *cred, struct socket *socket, struct label *socketlabel);

Parameter Description Locking
cred Subject credential  
socket Object; socket  
socketlabel Policy label for socket  

6.7.4.21 mpo_check_ifnet_relabel

int mpo_check_ifnet_relabel(struct ucred *cred, struct ifnet *ifnet, struct label *ifnetlabel, struct label *newlabel);

Parameter Description Locking
cred Subject credential  
ifnet Object; network interface  
ifnetlabel Existing policy label for ifnet  
newlabel Policy label update to later be applied to ifnet  

Determine whether the subject credential can relabel the passed network interface to the passed label update.

6.7.4.22 mpo_check_socket_relabel

int mpo_check_socket_relabel(struct ucred *cred, struct socket *socket, struct label *socketlabel, struct label *newlabel);

Parameter Description Locking
cred Subject credential  
socket Object; socket  
socketlabel Existing policy label for socket  
newlabel Label update to later be applied to socketlabel  

Determine whether the subject credential can relabel the passed socket to the passed label update.

6.7.4.23 mpo_check_cred_relabel

int mpo_check_cred_relabel(struct ucred *cred, struct label *newlabel);

Parameter Description Locking
cred Subject credential  
newlabel Label update to later be applied to cred  

Determine whether the subject credential can relabel itself to the passed label update.

6.7.4.24 mpo_check_vnode_relabel

int mpo_check_vnode_relabel(struct ucred *cred, struct vnode *vp, struct label *vnodelabel, struct label *newlabel);

Parameter Description Locking
cred Subject credential Immutable
vp Object; vnode Locked
vnodelabel Existing policy label for vp  
newlabel Policy label update to later be applied to vp  

Determine whether the subject credential can relabel the passed vnode to the passed label update.

6.7.4.25 mpo_check_mount_stat

int mpo_check_mount_stat(struct ucred *cred, struct mount *mp, struct label *mountlabel);

Parameter Description Locking
cred Subject credential  
mp Object; file system mount  
mountlabel Policy label for mp  

Determine whether the subject credential can see the results of a statfs performed on the file system. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches or EPERM for lack of privilege. This call may be made in a number of situations, including during invocations of statfs(2) and related calls, as well as to determine what file systems to exclude from listings of file systems, such as when getfsstat(2) is invoked.

6.7.4.26 mpo_check_proc_debug

int mpo_check_proc_debug(struct ucred *cred, struct proc *proc);

Parameter Description Locking
cred Subject credential Immutable
proc Object; process  

Determine whether the subject credential can debug the passed process. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to hide visibility of the target. This call may be made in a number of situations, including use of the ptrace(2) and ktrace(2) APIs, as well as for some types of procfs operations.

6.7.4.27 mpo_check_vnode_access

int mpo_check_vnode_access(struct ucred *cred, struct vnode *vp, struct label *label, int flags);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  
flags access(2) flags  

Determine how invocations of access(2) and related calls by the subject credential should return when performed on the passed vnode using the passed access flags. This should generally be implemented using the same semantics used in mpo_check_vnode_open. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches or EPERM for lack of privilege.

6.7.4.28 mpo_check_vnode_chdir

int mpo_check_vnode_chdir(struct ucred *cred, struct vnode *dvp, struct label *dlabel);

Parameter Description Locking
cred Subject credential  
dvp Object; vnode to chdir(2) into  
dlabel Policy label for dvp  

Determine whether the subject credential can change the process working directory to the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.29 mpo_check_vnode_chroot

int mpo_check_vnode_chroot(struct ucred *cred, struct vnode *dvp, struct label *dlabel);

Parameter Description Locking
cred Subject credential  
dvp Directory vnode  
dlabel Policy label associated with dvp  

Determine whether the subject should be allowed to chroot(2) into the specified directory (dvp).

6.7.4.30 mpo_check_vnode_create

int mpo_check_vnode_create(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct componentname *cnp, struct vattr *vap);

Parameter Description Locking
cred Subject credential  
dvp Object; vnode  
dlabel Policy label for dvp  
cnp Component name for dvp  
vap vnode attributes for vap  

Determine whether the subject credential can create a vnode with the passed parent directory, passed name information, and passed attribute information. Return 0 for success, or an errno value for failure. Suggested failure: EACCES. for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including as a result of calls to open(2) with O_CREAT, mknod(2), mkfifo(2), and others.

6.7.4.31 mpo_check_vnode_delete

int mpo_check_vnode_delete(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct vnode *vp, void *label, struct componentname *cnp);

Parameter Description Locking
cred Subject credential  
dvp Parent directory vnode  
dlabel Policy label for dvp  
vp Object; vnode to delete  
label Policy label for vp  
cnp Component name for vp  

Determine whether the subject credential can delete a vnode from the passed parent directory and passed name information. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including as a result of calls to unlink(2) and rmdir(2). Policies implementing this entry point should also implement mpo_check_rename_to to authorize deletion of objects as a result of being the target of a rename.

6.7.4.32 mpo_check_vnode_deleteacl

int mpo_check_vnode_deleteacl(struct ucred *cred, struct vnode *vp, struct label *label, acl_type_t type);

Parameter Description Locking
cred Subject credential Immutable
vp Object; vnode Locked
label Policy label for vp  
type ACL type  

Determine whether the subject credential can delete the ACL of passed type from the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.33 mpo_check_vnode_exec

int mpo_check_vnode_exec(struct ucred *cred, struct vnode *vp, struct label *label);

Parameter Description Locking
cred Subject credential  
vp Object; vnode to execute  
label Policy label for vp  

Determine whether the subject credential can execute the passed vnode. Determination of execute privilege is made separately from decisions about any transitioning event. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.34 mpo_check_vnode_getacl

int mpo_check_vnode_getacl(struct ucred *cred, struct vnode *vp, struct label *label, acl_type_t type);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  
type ACL type  

Determine whether the subject credential can retrieve the ACL of passed type from the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.35 mpo_check_vnode_getextattr

int mpo_check_vnode_getextattr(struct ucred *cred, struct vnode *vp, struct label *label, int attrnamespace, const char *name, struct uio *uio);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  
attrnamespace Extended attribute namespace  
name Extended attribute name  
uio I/O structure pointer; see uio(9)  

Determine whether the subject credential can retrieve the extended attribute with the passed namespace and name from the passed vnode. Policies implementing labeling using extended attributes may be interested in special handling of operations on those extended attributes. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.36 mpo_check_vnode_link

int mpo_check_vnode_link(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct vnode *vp, struct label *label, struct componentname *cnp);

Parameter Description Locking
cred Subject credential  
dvp Directory vnode  
dlabel Policy label associated with dvp  
vp Link destination vnode  
label Policy label associated with vp  
cnp Component name for the link being created  

Determine whether the subject should be allowed to create a link to the vnode vp with the name specified by cnp.

6.7.4.37 mpo_check_vnode_mmap

int mpo_check_vnode_mmap(struct ucred *cred, struct vnode *vp, struct label *label, int prot);

Parameter Description Locking
cred Subject credential  
vp Vnode to map  
label Policy label associated with vp  
prot Mmap protections (see mmap(2))  

Determine whether the subject should be allowed to map the vnode vp with the protections specified in prot.

6.7.4.38 mpo_check_vnode_mmap_downgrade

void mpo_check_vnode_mmap_downgrade(struct ucred *cred, struct vnode *vp, struct label *label, int *prot);

Parameter Description Locking
cred See Section 6.7.4.37.  
vp  
label  
prot Mmap protections to be downgraded  

Downgrade the mmap protections based on the subject and object labels.

6.7.4.39 mpo_check_vnode_mprotect

int mpo_check_vnode_mprotect(struct ucred *cred, struct vnode *vp, struct label *label, int prot);

Parameter Description Locking
cred Subject credential  
vp Mapped vnode  
prot Memory protections  

Determine whether the subject should be allowed to set the specified memory protections on memory mapped from the vnode vp.

6.7.4.40 mpo_check_vnode_poll

int mpo_check_vnode_poll(struct ucred *active_cred, struct ucred *file_cred, struct vnode *vp, struct label *label);

Parameter Description Locking
active_cred Subject credential  
file_cred Credential associated with the struct file  
vp Polled vnode  
label Policy label associated with vp  

Determine whether the subject should be allowed to poll the vnode vp.

6.7.4.41 mpo_check_vnode_rename_from

int mpo_vnode_rename_from(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct vnode *vp, struct label *label, struct componentname *cnp);

Parameter Description Locking
cred Subject credential  
dvp Directory vnode  
dlabel Policy label associated with dvp  
vp Vnode to be renamed  
label Policy label associated with vp  
cnp Component name for vp  

Determine whether the subject should be allowed to rename the vnode vp to something else.

6.7.4.42 mpo_check_vnode_rename_to

int mpo_check_vnode_rename_to(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct vnode *vp, struct label *label, int samedir, struct componentname *cnp);

Parameter Description Locking
cred Subject credential  
dvp Directory vnode  
dlabel Policy label associated with dvp  
vp Overwritten vnode  
label Policy label associated with vp  
samedir Boolean; 1 if the source and destination directories are the same  
cnp Destination component name  

Determine whether the subject should be allowed to rename to the vnode vp, into the directory dvp, or to the name represented by cnp. If there is no existing file to overwrite, vp and label will be NULL.

6.7.4.43 mpo_check_socket_listen

int mpo_check_socket_listen(struct ucred *cred, struct socket *socket, struct label *socketlabel);

Parameter Description Locking
cred Subject credential  
socket Object; socket  
socketlabel Policy label for socket  

Determine whether the subject credential can listen on the passed socket. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.44 mpo_check_vnode_lookup

int mpo_check_vnode_lookup(struct ucred *cred, struct vnode *dvp, struct label *dlabel, struct componentname *cnp);

Parameter Description Locking
cred Subject credential  
dvp Object; vnode  
dlabel Policy label for dvp  
cnp Component name being looked up  

Determine whether the subject credential can perform a lookup in the passed directory vnode for the passed name. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.45 mpo_check_vnode_open

int mpo_check_vnode_open(struct ucred *cred, struct vnode *vp, struct label *label, int acc_mode);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  
acc_mode open(2) access mode  

Determine whether the subject credential can perform an open operation on the passed vnode with the passed access mode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.46 mpo_check_vnode_readdir

int mpo_check_vnode_readdir(struct ucred *cred, struct vnode *dvp, struct label *dlabel);

Parameter Description Locking
cred Subject credential  
dvp Object; directory vnode  
dlabel Policy label for dvp  

Determine whether the subject credential can perform a readdir operation on the passed directory vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.47 mpo_check_vnode_readlink

int mpo_check_vnode_readlink(struct ucred *cred, struct vnode *vp, struct label *label);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  

Determine whether the subject credential can perform a readlink operation on the passed symlink vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege. This call may be made in a number of situations, including an explicit readlink call by the user process, or as a result of an implicit readlink during a name lookup by the process.

6.7.4.48 mpo_check_vnode_revoke

int mpo_check_vnode_revoke(struct ucred *cred, struct vnode *vp, struct label *label);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  

Determine whether the subject credential can revoke access to the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.49 mpo_check_vnode_setacl

int mpo_check_vnode_setacl(struct ucred *cred, struct vnode *vp, struct label *label, acl_type_t type, struct acl *acl);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  
type ACL type  
acl ACL  

Determine whether the subject credential can set the passed ACL of passed type on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.50 mpo_check_vnode_setextattr

int mpo_check_vnode_setextattr(struct ucred *cred, struct vnode *vp, struct label *label, int attrnamespace, const char *name, struct uio *uio);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  
attrnamespace Extended attribute namespace  
name Extended attribute name  
uio I/O structure pointer; see uio(9)  

Determine whether the subject credential can set the extended attribute of passed name and passed namespace on the passed vnode. Policies implementing security labels backed into extended attributes may want to provide additional protections for those attributes. Additionally, policies should avoid making decisions based on the data referenced from uio, as there is a potential race condition between this check and the actual operation. The uio may also be NULL if a delete operation is being performed. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.51 mpo_check_vnode_setflags

int mpo_check_vnode_setflags(struct ucred *cred, struct vnode *vp, struct label *label, u_long flags);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  
flags File flags; see chflags(2)  

Determine whether the subject credential can set the passed flags on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.52 mpo_check_vnode_setmode

int mpo_check_vnode_setmode(struct ucred *cred, struct vnode *vp, struct label *label, mode_t mode);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  
mode File mode; see chmod(2)  

Determine whether the subject credential can set the passed mode on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.53 mpo_check_vnode_setowner

int mpo_check_vnode_setowner(struct ucred *cred, struct vnode *vp, struct label *label, uid_t uid, gid_t gid);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  
uid User ID  
gid Group ID  

Determine whether the subject credential can set the passed uid and passed gid as file uid and file gid on the passed vnode. The IDs may be set to (-1) to request no update. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.54 mpo_check_vnode_setutimes

int mpo_check_vnode_setutimes(struct ucred *cred, struct vnode *vp, struct label *label, struct timespec atime, struct timespec mtime);

Parameter Description Locking
cred Subject credential  
vp Object; vp  
label Policy label for vp  
atime Access time; see utimes(2)  
mtime Modification time; see utimes(2)  

Determine whether the subject credential can set the passed access timestamps on the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.55 mpo_check_proc_sched

int mpo_check_proc_sched(struct ucred *ucred, struct proc *proc);

Parameter Description Locking
cred Subject credential  
proc Object; process  

Determine whether the subject credential can change the scheduling parameters of the passed process. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to limit visibility.

See setpriority(2) for more information.

6.7.4.56 mpo_check_proc_signal

int mpo_check_proc_signal(struct ucred *cred, struct proc *proc, int signal);

Parameter Description Locking
cred Subject credential  
proc Object; process  
signal Signal; see kill(2)  

Determine whether the subject credential can deliver the passed signal to the passed process. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, EPERM for lack of privilege, or ESRCH to limit visibility.

6.7.4.57 mpo_check_vnode_stat

int mpo_check_vnode_stat(struct ucred *cred, struct vnode *vp, struct label *label);

Parameter Description Locking
cred Subject credential  
vp Object; vnode  
label Policy label for vp  

Determine whether the subject credential can stat the passed vnode. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

See stat(2) for more information.

6.7.4.58 mpo_check_ifnet_transmit

int mpo_check_ifnet_transmit(struct ucred *cred, struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *mbuf, struct label *mbuflabel);

Parameter Description Locking
cred Subject credential  
ifnet Network interface  
ifnetlabel Policy label for ifnet  
mbuf Object; mbuf to be sent  
mbuflabel Policy label for mbuf  

Determine whether the network interface can transmit the passed mbuf. Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.59 mpo_check_socket_deliver

int mpo_check_socket_deliver(struct ucred *cred, struct ifnet *ifnet, struct label *ifnetlabel, struct mbuf *mbuf, struct label *mbuflabel);

Parameter Description Locking
cred Subject credential  
ifnet Network interface  
ifnetlabel Policy label for ifnet  
mbuf Object; mbuf to be delivered  
mbuflabel Policy label for mbuf  

Determine whether the socket may receive the datagram stored in the passed mbuf header. Return 0 for success, or an errno value for failure. Suggested failures: EACCES for label mismatch, or EPERM for lack of privilege.

6.7.4.60 mpo_check_socket_visible

int mpo_check_socket_visible(struct ucred *cred, struct socket *so, struct label *socketlabel);

Parameter Description Locking
cred Subject credential Immutable
so Object; socket  
socketlabel Policy label for so  

Determine whether the subject credential cred can "see" the passed socket (socket) using system monitoring functions, such as those employed by netstat(8) and sockstat(1). Return 0 for success, or an errno value for failure. Suggested failure: EACCES for label mismatches, EPERM for lack of privilege, or ESRCH to hide visibility.

6.7.4.61 mpo_check_system_acct

int mpo_check_system_acct(struct ucred *ucred, struct vnode *vp, struct label *vlabel);

Parameter Description Locking
ucred Subject credential  
vp Accounting file; acct(5)  
vlabel Label associated with vp  

Determine whether the subject should be allowed to enable accounting, based on its label and the label of the accounting log file.

6.7.4.62 mpo_check_system_nfsd

int mpo_check_system_nfsd(struct ucred *cred);

Parameter Description Locking
cred Subject credential  

Determine whether the subject should be allowed to call nfssvc(2).

6.7.4.63 mpo_check_system_reboot

int mpo_check_system_reboot(struct ucred *cred, int howto);

Parameter Description Locking
cred Subject credential  
howto howto parameter from reboot(2)  

Determine whether the subject should be allowed to reboot the system in the specified manner.

6.7.4.64 mpo_check_system_settime

int mpo_check_system_settime(struct ucred *cred);

Parameter Description Locking
cred Subject credential  

Determine whether the user should be allowed to set the system clock.

6.7.4.65 mpo_check_system_swapon

int mpo_check_system_swapon(struct ucred *cred, struct vnode *vp, struct label *vlabel);

Parameter Description Locking
cred Subject credential  
vp Swap device  
vlabel Label associated with vp  

Determine whether the subject should be allowed to add vp as a swap device.

6.7.4.66 mpo_check_system_sysctl

int mpo_check_system_sysctl(struct ucred *cred, int *name, u_int *namelen, void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen);

Parameter Description Locking
cred Subject credential  
name See sysctl(3)  
namelen  
old  
oldlenp  
inkernel Boolean; 1 if called from kernel  
new See sysctl(3)  
newlen  

Determine whether the subject should be allowed to make the specified sysctl(3) transaction.

6.7.5 Label Management Calls

Relabel events occur when a user process has requested that the label on an object be modified. A two-phase update occurs: first, an access control check will be performed to determine if the update is both valid and permitted, and then the update itself is performed via a separate entry point. Relabel entry points typically accept the object, object label reference, and an update label submitted by the process. Memory allocation during relabel is discouraged, as relabel calls are not permitted to fail (failure should be reported earlier in the relabel check).

This, and other documents, can be downloaded from ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/.

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