236 lines
8.1 KiB
C
236 lines
8.1 KiB
C
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/*************************************************************************
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*
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* kernel_pipe.c
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*
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* LOMAC - Low Water-Mark Mandatory Access Control
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* Copyright (c) 1999-2001 Networks Associates, Inc. All rights reserved.
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*
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* Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* Neither the name of NAI Labs, Inc. nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*
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*
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* This file contains part of LOMAC's interface to the kernel. This
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* part allows LOMAC to monitor (unnamed) pipe read and write
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* operations by interposing control on the kernel's pipeops vector.
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*
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* The pipeops vector is defined in kern/sys_pipe.c.
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*
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* USAGE:
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*
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* The LOMAC LKM should call lomac_initialize_pipes() at LKM load time.
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* This function turns unnamed pipe interposition on by modifying
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* the function addresses in pipeops.
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*
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* Once the LOMAC LKM turns interposition on, all reads and writes
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* will pass through this file's monitoring functions.
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*
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* This file provides a lomac_uninitialize_pipes() function which
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* turns unnamed pipe interposition off by restoring pipeops to
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* its original unmodified state. Once the LOMAC LKM turns
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* interposition off, subsequent unnamed pipe reads and writes
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* will not pass through this file's monitoring functions.
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*
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* HOW LOMAC HANDLES PIPES:
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*
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* (This text describes how LOMAC handles (unnamed) pipes in terms of
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* abstract architecture-independent concepts.) LOMAC does not treat
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* pipes as objects, as it does files. When the kernel creates a new
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* pipe, LOMAC assigns it the highest level. Whenever a process
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* writes to the pipe, LOMAC reduces the pipe's level to match the
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* level of the writing process. Whenever a process reads from a
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* pipe, LOMAC reduces the level of the reading process to match the
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* pipe's level. As a result, if a high-level process reads the
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* output of a low-level process through a pipe, the reading process
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* will wind up at the low level.
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*
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* It takes two `struct pipe's to make a pipe. We set the level
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* information in both `struct pipes', and keep them synchronized.
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*
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* This code presently relies on the one-big-kernel-lock to
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* synchronize its access to the `pipe_state' field of each `struct
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* pipe'.
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*
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*/
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/malloc.h>
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#include <sys/file.h>
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#include <sys/selinfo.h>
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#include <sys/pipe.h>
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#include <sys/proc.h>
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#include <sys/uio.h>
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#include "lomac.h"
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#include "kernel_interface.h"
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#include "kernel_monitor.h"
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#include "kernel_pipe.h"
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/* `pipeops' is the kernel's pipe operations vector for the file *
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* structure. All reads and writes to pipes call through this vector. */
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extern struct fileops pipeops; /* defined in kern/sys_pipe.c */
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/* These vars store the original addresses of the pipeops read and *
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* write operations, so we can call them, and even restore them *
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* later if we want to. */
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static int (*pipe_read_orig)(struct file *, struct uio *, struct ucred *,
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int, struct thread *);
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static int (*pipe_write_orig)(struct file *, struct uio *, struct ucred *,
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int, struct thread *);
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/* declarations of functions private to this module: */
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static int lomac_pipe_read(struct file *, struct uio *, struct ucred *,
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int, struct thread *);
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static int lomac_pipe_write(struct file *, struct uio *, struct ucred *,
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int, struct thread *);
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/* -------------------- public functions ---------------------------- */
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/* lomac_initialize_pipes()
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*
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* in: nothing
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* out: nothing
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* return: 0
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*
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* Turns pipe interposition on by replacing the pipe_read() and pipe_write()
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* operations in the kernel's pipeops vector with lomac_pipe_read() and
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* lomac_pipe_write(). Saves the addresses of the original operations
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* so other functions can call them, and so pipe_interposition_off()
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* can restore the pipeops vector to its original unmodified state.
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*
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*/
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int
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lomac_initialize_pipes(void) {
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pipe_read_orig = pipeops.fo_read;
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pipeops.fo_read = lomac_pipe_read;
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pipe_write_orig = pipeops.fo_write;
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pipeops.fo_write = lomac_pipe_write;
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return (0);
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} /* lomac_initialize_pipes() */
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/* lomac_uninitialize_pipes()
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*
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* in: nothing
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* out: nothing
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* return: 0
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*
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* Turns pipe interposition off by restoring the pipeops vector to its
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* original unmodified state.
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*
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* See note at top of file regarding this function and unloading the
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* LOMAC LKM.
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*
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*/
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int
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lomac_uninitialize_pipes(void) {
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KASSERT(pipe_read_orig, ("LOMAC:pipe interpositon off before on"));
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KASSERT(pipe_write_orig, ("LOMAC:pipe interpositon off before on"));
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pipeops.fo_read = pipe_read_orig;
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pipeops.fo_write = pipe_write_orig;
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return (0);
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} /* lomac_uninitialize_pipes() */
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/* ------------------- private functions --------------------------- */
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#ifndef MIN
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#define MIN(lo, mac) ((lo) < (mac) ? (lo) : (mac))
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#endif
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/* lomac_pipe_read()
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*
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* Passes the read operation down to pipe_read_orig(). If
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* pipe_read_orig() returns success, examines the level of the pipe
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* and the reading process. If the reading process has a higher
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* level, reduces the level of the process to equal the pipe's level.
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*
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*/
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static int
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lomac_pipe_read(struct file *fp, struct uio *uio, struct ucred *cred,
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int flags, struct thread *td) {
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lomac_object_t read_pipe; /* attrs are in read end of pipe */
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struct uio kuio;
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struct iovec kiov;
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void *buf;
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int len;
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int ret_val; /* holds return values */
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len = MIN(uio->uio_resid, BIG_PIPE_SIZE);
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kiov.iov_base = buf = malloc(len, M_TEMP, M_WAITOK);
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kiov.iov_len = len;
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kuio.uio_iov = &kiov;
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kuio.uio_iovcnt = 1;
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kuio.uio_offset = 0;
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kuio.uio_resid = len;
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kuio.uio_segflg = UIO_SYSSPACE;
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kuio.uio_rw = UIO_READ;
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kuio.uio_td = td;
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ret_val = pipe_read_orig(fp, &kuio, cred, flags, td);
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if (ret_val == 0) {
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read_pipe.lo_type = LO_TYPE_PIPE;
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read_pipe.lo_object.pipe = (struct pipe *)fp->f_data;
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(void)monitor_read_object(td->td_proc, &read_pipe);
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ret_val = uiomove(buf, len - kuio.uio_resid, uio);
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}
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free(buf, M_TEMP);
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return (ret_val);
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} /* lomac_pipe_read() */
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/* lomac_pipe_write()
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*
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* Passes the write operation down to pipe_write_orig(). If
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* pipe_write_orig() returns success, examines the level of the pipe
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* and the writing process. If the pipe has a higher level than the
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* writing process, this function reduces the pipe's level to equal
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* the level of the writing process.
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*
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*/
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static int
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lomac_pipe_write(struct file *fp, struct uio *uio, struct ucred *cred,
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int flags, struct thread *td) {
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lomac_object_t pipe;
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int ret_val; /* holds return values */
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pipe.lo_type = LO_TYPE_PIPE;
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pipe.lo_object.pipe = (struct pipe *)fp->f_data;
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ret_val = monitor_pipe_write(td->td_proc, &pipe);
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if (ret_val == 0)
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ret_val = pipe_write_orig(fp, uio, cred, flags, td);
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return (ret_val);
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} /* lomac_pipe_write() */
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