Author: jonathan
Date: Fri Jul 15 09:37:14 2011
New Revision: 224056
URL: http://svn.freebsd.org/changeset/base/224056
Log:
Add implementation for capabilities.
Code to actually implement Capsicum capabilities, including fileops and
kern_capwrap(), which creates a capability to wrap an existing file
descriptor.
We also modify kern_close() and closef() to handle capabilities.
Finally, remove cap_filelist from struct capability, since we don't
actually need it.
Approved by: mentor (rwatson), re (Capsicum blanket)
Sponsored by: Google Inc
Modified:
head/sys/kern/kern_descrip.c
head/sys/kern/sys_capability.c
head/sys/sys/capability.h
Modified: head/sys/kern/kern_descrip.c
==============================================================================
--- head/sys/kern/kern_descrip.c Fri Jul 15 06:54:21 2011
(r224055)
+++ head/sys/kern/kern_descrip.c Fri Jul 15 09:37:14 2011
(r224056)
@@ -1160,7 +1160,7 @@ kern_close(td, fd)
int fd;
{
struct filedesc *fdp;
- struct file *fp;
+ struct file *fp, *fp_object;
int error;
int holdleaders;
@@ -1195,8 +1195,14 @@ kern_close(td, fd)
* added, and deleteing a knote for the new fd.
*/
knote_fdclose(td, fd);
- if (fp->f_type == DTYPE_MQUEUE)
- mq_fdclose(td, fd, fp);
+
+ /*
+ * When we're closing an fd with a capability, we need to notify
+ * mqueue if the underlying object is of type mqueue.
+ */
+ (void)cap_funwrap(fp, 0, &fp_object);
+ if (fp_object->f_type == DTYPE_MQUEUE)
+ mq_fdclose(td, fd, fp_object);
FILEDESC_XUNLOCK(fdp);
error = closef(fp, td);
@@ -2146,6 +2152,7 @@ closef(struct file *fp, struct thread *t
struct flock lf;
struct filedesc_to_leader *fdtol;
struct filedesc *fdp;
+ struct file *fp_object;
/*
* POSIX record locking dictates that any close releases ALL
@@ -2158,11 +2165,15 @@ closef(struct file *fp, struct thread *t
* NULL thread pointer when there really is no owning
* context that might have locks, or the locks will be
* leaked.
+ *
+ * If this is a capability, we do lock processing under the underlying
+ * node, not the capability itself.
*/
- if (fp->f_type == DTYPE_VNODE && td != NULL) {
+ (void)cap_funwrap(fp, 0, &fp_object);
+ if ((fp_object->f_type == DTYPE_VNODE) && (td != NULL)) {
int vfslocked;
- vp = fp->f_vnode;
+ vp = fp_object->f_vnode;
vfslocked = VFS_LOCK_GIANT(vp->v_mount);
if ((td->td_proc->p_leader->p_flag & P_ADVLOCK) != 0) {
lf.l_whence = SEEK_SET;
@@ -2192,7 +2203,7 @@ closef(struct file *fp, struct thread *t
lf.l_start = 0;
lf.l_len = 0;
lf.l_type = F_UNLCK;
- vp = fp->f_vnode;
+ vp = fp_object->f_vnode;
(void) VOP_ADVLOCK(vp,
(caddr_t)fdtol->fdl_leader,
F_UNLCK, &lf, F_POSIX);
@@ -2497,6 +2508,9 @@ fputsock(struct socket *so)
/*
* Handle the last reference to a file being closed.
+ *
+ * No special capability handling here, as the capability's fo_close will run
+ * instead of the object here, and perform any necessary drop on the object.
*/
int
_fdrop(struct file *fp, struct thread *td)
Modified: head/sys/kern/sys_capability.c
==============================================================================
--- head/sys/kern/sys_capability.c Fri Jul 15 06:54:21 2011
(r224055)
+++ head/sys/kern/sys_capability.c Fri Jul 15 09:37:14 2011
(r224056)
@@ -123,18 +123,66 @@ cap_getmode(struct thread *td, struct ca
* struct capability describes a capability, and is hung off of its struct
* file f_data field. cap_file and cap_rightss are static once hooked up, as
* neither the object it references nor the rights it encapsulates are
- * permitted to change. cap_filelist may change when other capabilites are
- * added or removed from the same file, and is currently protected by the
- * pool mutex for the object file descriptor.
+ * permitted to change.
*/
struct capability {
struct file *cap_object; /* Underlying object's file. */
struct file *cap_file; /* Back-pointer to cap's file. */
cap_rights_t cap_rights; /* Mask of rights on object. */
- LIST_ENTRY(capability) cap_filelist; /* Object's cap list. */
};
/*
+ * Capabilities have a fileops vector, but in practice none should ever be
+ * called except for fo_close, as the capability will normally not be
+ * returned during a file descriptor lookup in the system call code.
+ */
+static fo_rdwr_t capability_read;
+static fo_rdwr_t capability_write;
+static fo_truncate_t capability_truncate;
+static fo_ioctl_t capability_ioctl;
+static fo_poll_t capability_poll;
+static fo_kqfilter_t capability_kqfilter;
+static fo_stat_t capability_stat;
+static fo_close_t capability_close;
+
+static struct fileops capability_ops = {
+ .fo_read = capability_read,
+ .fo_write = capability_write,
+ .fo_truncate = capability_truncate,
+ .fo_ioctl = capability_ioctl,
+ .fo_poll = capability_poll,
+ .fo_kqfilter = capability_kqfilter,
+ .fo_stat = capability_stat,
+ .fo_close = capability_close,
+ .fo_flags = DFLAG_PASSABLE,
+};
+
+static struct fileops capability_ops_unpassable = {
+ .fo_read = capability_read,
+ .fo_write = capability_write,
+ .fo_truncate = capability_truncate,
+ .fo_ioctl = capability_ioctl,
+ .fo_poll = capability_poll,
+ .fo_kqfilter = capability_kqfilter,
+ .fo_stat = capability_stat,
+ .fo_close = capability_close,
+ .fo_flags = 0,
+};
+
+static uma_zone_t capability_zone;
+
+static void
+capability_init(void *dummy __unused)
+{
+
+ capability_zone = uma_zcreate("capability", sizeof(struct capability),
+ NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
+ if (capability_zone == NULL)
+ panic("capability_init: capability_zone not initialized");
+}
+SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_ANY, capability_init, NULL);
+
+/*
* Test whether a capability grants the requested rights.
*/
static int
@@ -147,6 +195,85 @@ cap_check(struct capability *c, cap_righ
}
/*
+ * Extract rights from a capability for monitoring purposes -- not for use in
+ * any other way, as we want to keep all capability permission evaluation in
+ * this one file.
+ */
+cap_rights_t
+cap_rights(struct file *fp_cap)
+{
+ struct capability *c;
+
+ KASSERT(fp_cap->f_type == DTYPE_CAPABILITY,
+ ("cap_rights: !capability"));
+
+ c = fp_cap->f_data;
+ return (c->cap_rights);
+}
+
+/*
+ * Create a capability to wrap around an existing file.
+ */
+int
+kern_capwrap(struct thread *td, struct file *fp, cap_rights_t rights,
+ struct file **fcappp, int *capfdp)
+{
+ struct capability *cp, *cp_old;
+ struct file *fp_object;
+ int error;
+
+ if ((rights | CAP_MASK_VALID) != CAP_MASK_VALID)
+ return (EINVAL);
+
+ /*
+ * If a new capability is being derived from an existing capability,
+ * then the new capability rights must be a subset of the existing
+ * rights.
+ */
+ if (fp->f_type == DTYPE_CAPABILITY) {
+ cp_old = fp->f_data;
+ if ((cp_old->cap_rights | rights) != cp_old->cap_rights)
+ return (ENOTCAPABLE);
+ }
+
+ /*
+ * Allocate a new file descriptor to hang the capability off of.
+ */
+ error = falloc(td, fcappp, capfdp, fp->f_flag);
+ if (error)
+ return (error);
+
+ /*
+ * Rather than nesting capabilities, directly reference the object an
+ * existing capability references. There's nothing else interesting
+ * to preserve for future use, as we've incorporated the previous
+ * rights mask into the new one. This prevents us from having to
+ * deal with capability chains.
+ */
+ if (fp->f_type == DTYPE_CAPABILITY)
+ fp_object = ((struct capability *)fp->f_data)->cap_object;
+ else
+ fp_object = fp;
+ fhold(fp_object);
+ cp = uma_zalloc(capability_zone, M_WAITOK | M_ZERO);
+ cp->cap_rights = rights;
+ cp->cap_object = fp_object;
+ cp->cap_file = *fcappp;
+ if (fp->f_flag & DFLAG_PASSABLE)
+ finit(*fcappp, fp->f_flag, DTYPE_CAPABILITY, cp,
+ &capability_ops);
+ else
+ finit(*fcappp, fp->f_flag, DTYPE_CAPABILITY, cp,
+ &capability_ops_unpassable);
+
+ /*
+ * Release our private reference (the proc filedesc still has one).
+ */
+ fdrop(*fcappp, td);
+ return (0);
+}
+
+/*
* Given a file descriptor, test it against a capability rights mask and then
* return the file descriptor on which to actually perform the requested
* operation. As long as the reference to fp_cap remains valid, the returned
@@ -206,6 +333,89 @@ cap_funwrap_mmap(struct file *fp_cap, ca
return (0);
}
+/*
+ * When a capability is closed, simply drop the reference on the underlying
+ * object and free the capability. fdrop() will handle the case where the
+ * underlying object also needs to close, and the caller will have already
+ * performed any object-specific lock or mqueue handling.
+ */
+static int
+capability_close(struct file *fp, struct thread *td)
+{
+ struct capability *c;
+ struct file *fp_object;
+
+ KASSERT(fp->f_type == DTYPE_CAPABILITY,
+ ("capability_close: !capability"));
+
+ c = fp->f_data;
+ fp->f_ops = &badfileops;
+ fp->f_data = NULL;
+ fp_object = c->cap_object;
+ uma_zfree(capability_zone, c);
+ return (fdrop(fp_object, td));
+}
+
+/*
+ * In general, file descriptor operations should never make it to the
+ * capability, only the underlying file descriptor operation vector, so panic
+ * if we do turn up here.
+ */
+static int
+capability_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
+ int flags, struct thread *td)
+{
+
+ panic("capability_read");
+}
+
+static int
+capability_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
+ int flags, struct thread *td)
+{
+
+ panic("capability_write");
+}
+
+static int
+capability_truncate(struct file *fp, off_t length, struct ucred *active_cred,
+ struct thread *td)
+{
+
+ panic("capability_truncate");
+}
+
+static int
+capability_ioctl(struct file *fp, u_long com, void *data,
+ struct ucred *active_cred, struct thread *td)
+{
+
+ panic("capability_ioctl");
+}
+
+static int
+capability_poll(struct file *fp, int events, struct ucred *active_cred,
+ struct thread *td)
+{
+
+ panic("capability_poll");
+}
+
+static int
+capability_kqfilter(struct file *fp, struct knote *kn)
+{
+
+ panic("capability_kqfilter");
+}
+
+static int
+capability_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
+ struct thread *td)
+{
+
+ panic("capability_stat");
+}
+
#else /* !CAPABILITIES */
/*
Modified: head/sys/sys/capability.h
==============================================================================
--- head/sys/sys/capability.h Fri Jul 15 06:54:21 2011 (r224055)
+++ head/sys/sys/capability.h Fri Jul 15 09:37:14 2011 (r224056)
@@ -64,6 +64,12 @@
#define IN_CAPABILITY_MODE(td) (td->td_ucred->cr_flags & CRED_FLAG_CAPMODE)
/*
+ * Create a capability to wrap a file object.
+ */
+int kern_capwrap(struct thread *td, struct file *fp, cap_rights_t rights,
+ struct file **cap, int *capfd);
+
+/*
* Unwrap a capability if its rights mask is a superset of 'rights'.
*
* Unwrapping a non-capability is effectively a no-op; the value of fp_cap
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