367 lines
11 KiB
C
367 lines
11 KiB
C
/* $NetBSD: kern_verifiedexec.c,v 1.8 2004/09/17 14:11:25 skrll Exp $ */
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/*-
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* Copyright (c) 2001, 2002 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Brett Lymn and Jason R Fink
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. 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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* 2. 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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: kern_verifiedexec.c,v 1.8 2004/09/17 14:11:25 skrll Exp $");
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#include <sys/param.h>
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#include <sys/mount.h>
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#include <sys/malloc.h>
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#include <sys/vnode.h>
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#include <sys/exec.h>
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#include <sys/md5.h>
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#include <sys/sha1.h>
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#include <sys/verified_exec.h>
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/* Set the buffer to a single page for md5 and sha1 */
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#define BUF_SIZE PAGE_SIZE
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extern LIST_HEAD(veriexec_devhead, veriexec_dev_list) veriexec_dev_head;
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static int
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md5_fingerprint(struct vnode *vp, struct veriexec_inode_list *ip,
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struct proc *p, u_quad_t file_size, char *fingerprint);
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static int
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sha1_fingerprint(struct vnode *vp, struct veriexec_inode_list *ip,
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struct proc *p, u_quad_t file_size, char *fingerprint);
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/*
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* md5_fingerprint:
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* Evaluate the md5 fingerprint of the given file.
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*
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*/
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static int
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md5_fingerprint(struct vnode *vp, struct veriexec_inode_list *ip,
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struct proc *p, u_quad_t file_size, char *fingerprint)
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{
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u_quad_t j;
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MD5_CTX md5context;
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char *filebuf;
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size_t resid;
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int count, error;
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filebuf = malloc(BUF_SIZE, M_TEMP, M_WAITOK);
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MD5Init(&md5context);
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for (j = 0; j < file_size; j+= BUF_SIZE) {
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if ((j + BUF_SIZE) > file_size) {
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count = file_size - j;
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} else
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count = BUF_SIZE;
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error = vn_rdwr(UIO_READ, vp, filebuf, count, j,
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UIO_SYSSPACE, 0, p->p_ucred, &resid, NULL);
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if (error) {
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free(filebuf, M_TEMP);
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return error;
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}
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MD5Update(&md5context, filebuf, (unsigned int) count);
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}
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MD5Final(fingerprint, &md5context);
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free(filebuf, M_TEMP);
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return 0;
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}
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static int
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sha1_fingerprint(struct vnode *vp, struct veriexec_inode_list *ip,
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struct proc *p, u_quad_t file_size, char *fingerprint)
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{
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u_quad_t j;
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SHA1_CTX sha1context;
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char *filebuf;
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size_t resid;
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int count, error;
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filebuf = malloc(BUF_SIZE, M_TEMP, M_WAITOK);
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SHA1Init(&sha1context);
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for (j = 0; j < file_size; j+= BUF_SIZE) {
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if ((j + BUF_SIZE) > file_size) {
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count = file_size - j;
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} else
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count = BUF_SIZE;
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error = vn_rdwr(UIO_READ, vp, filebuf, count, j,
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UIO_SYSSPACE, 0, p->p_ucred, &resid, NULL);
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if (error) {
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free(filebuf, M_TEMP);
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return error;
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}
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SHA1Update(&sha1context, filebuf, (unsigned int) count);
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}
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SHA1Final(fingerprint, &sha1context);
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free(filebuf, M_TEMP);
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return 0;
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}
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/*
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* evaluate_fingerprint:
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* Check the fingerprint type for the given file and evaluate the
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* fingerprint for that file. It is assumed that fingerprint has sufficient
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* storage to hold the resulting fingerprint string.
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*
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*/
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int
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evaluate_fingerprint(struct vnode *vp, struct veriexec_inode_list *ip,
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struct proc *p, u_quad_t file_size, char *fingerprint)
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{
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int error;
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switch (ip->fp_type) {
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case FINGERPRINT_TYPE_MD5:
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error = md5_fingerprint(vp, ip, p, file_size, fingerprint);
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break;
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case FINGERPRINT_TYPE_SHA1:
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error = sha1_fingerprint(vp, ip, p, file_size, fingerprint);
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break;
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default:
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error = EINVAL;
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break;
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}
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return error;
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}
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/*
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* fingerprintcmp:
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* Compare the two given fingerprints to see if they are the same
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* Differing fingerprint methods may have differing lengths which
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* is handled by this routine. This function follows the convention
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* of other cmp functions and returns 0 if the fingerprints match and
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* 1 if they don't.
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*/
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int
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fingerprintcmp(struct veriexec_inode_list *ip, unsigned char *digest)
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{
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switch(ip->fp_type) {
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case FINGERPRINT_TYPE_MD5:
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return memcmp(ip->fingerprint, digest, MD5_FINGERPRINTLEN);
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break;
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case FINGERPRINT_TYPE_SHA1:
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return memcmp(ip->fingerprint, digest, SHA1_FINGERPRINTLEN);
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break;
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default:
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/* unknown fingerprint type, just fail it after whining */
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printf("fingerprintcmp: unknown fingerprint type\n");
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return 1;
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break;
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}
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}
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/*
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* get_veriexec_inode:
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* Search the given verified exec fingerprint list for the given
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* fileid. If it exists then return a pointer to the list entry,
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* otherwise return NULL. If found_dev is non-NULL set this to true
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* iff the given device has a fingerprint list.
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*
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*/
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struct veriexec_inode_list *
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get_veriexec_inode(struct veriexec_devhead *head, long fsid, long fileid,
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char *found_dev)
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{
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struct veriexec_dev_list *lp;
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struct veriexec_inode_list *ip;
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ip = NULL;
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if (found_dev != NULL)
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*found_dev = 0;
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#ifdef VERIFIED_EXEC_DEBUG
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printf("searching for file %lu on device %lu\n", fileid, fsid);
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#endif
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for (lp = LIST_FIRST(head); lp != NULL; lp = LIST_NEXT(lp, entries))
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if (lp->id == fsid)
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break;
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if (lp != NULL) {
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#ifdef VERIFIED_EXEC_DEBUG
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printf("found matching dev number %lu\n", lp->id);
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#endif
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if (found_dev != NULL)
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*found_dev = 1;
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for (ip = LIST_FIRST(&(lp->inode_head)); ip != NULL;
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ip = LIST_NEXT(ip, entries))
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if (ip->inode == fileid)
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break;
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}
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return ip;
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}
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/*
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* check veriexec:
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* check a file signature and return a status to check_exec.
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*/
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int
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check_veriexec(struct proc *p, struct vnode *vp, struct exec_package *epp,
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int direct_exec)
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{
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int error;
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char digest[MAXFINGERPRINTLEN], found_dev;
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struct veriexec_inode_list *ip;
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error = 0;
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found_dev = 0;
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if (vp->fp_status == FINGERPRINT_INVALID) {
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#ifdef VERIFIED_EXEC_DEBUG
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printf("looking for loaded signature\n");
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#endif
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ip = get_veriexec_inode(&veriexec_dev_head, epp->ep_vap->va_fsid,
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epp->ep_vap->va_fileid, &found_dev);
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if (found_dev == 0) {
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#ifdef VERIFIED_EXEC_DEBUG
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printf("No device entry found\n");
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#endif
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vp->fp_status = FINGERPRINT_NODEV;
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}
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if (ip != NULL) {
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#ifdef VERIFIED_EXEC_DEBUG
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printf("found matching inode number %lu\n", ip->inode);
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#endif
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error = evaluate_fingerprint(vp, ip, p,
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epp->ep_vap->va_size,
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digest);
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if (error)
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return error;
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if (fingerprintcmp(ip, digest) == 0) {
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if (ip->type == VERIEXEC_DIRECT) {
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#ifdef VERIFIED_EXEC_DEBUG
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printf("Evaluated fingerprint matches\n");
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#endif
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vp->fp_status = FINGERPRINT_VALID;
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} else {
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#ifdef VERIFIED_EXEC_DEBUG
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printf("Evaluated indirect fingerprint matches\n");
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#endif
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vp->fp_status = FINGERPRINT_INDIRECT;
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}
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} else {
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#ifdef VERIFIED_EXEC_DEBUG
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printf("Evaluated fingerprint match failed\n");
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#endif
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vp->fp_status = FINGERPRINT_NOMATCH;
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}
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} else {
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#ifdef VERIFIED_EXEC_DEBUG
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printf("No fingerprint entry found\n");
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#endif
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vp->fp_status = FINGERPRINT_NOENTRY;
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}
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}
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switch (vp->fp_status) {
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case FINGERPRINT_INVALID: /* should not happen */
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printf("Got unexpected FINGERPRINT_INVALID!!!\n");
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error = EPERM;
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break;
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case FINGERPRINT_VALID: /* is ok - report so if debug is on */
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#ifdef VERIFIED_EXEC_DEBUG
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printf("Fingerprint matches\n");
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#endif
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break;
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case FINGERPRINT_INDIRECT: /* fingerprint ok but need to check
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for direct execution */
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if (direct_exec == 1) {
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printf("Attempt to execute %s (dev %lu, inode %lu) "
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"directly by pid %u (ppid %u, gppid %u)\n",
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epp->ep_name, epp->ep_vap->va_fsid,
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epp->ep_vap->va_fileid, p->p_pid,
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p->p_pptr->p_pid, p->p_pptr->p_pptr->p_pid);
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if (securelevel > 1)
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error = EPERM;
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}
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break;
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case FINGERPRINT_NOMATCH: /* does not match - whine about it */
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printf("Fingerprint for %s (dev %lu, inode %lu) does not "
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"match loaded value\n",
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epp->ep_name, epp->ep_vap->va_fsid,
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epp->ep_vap->va_fileid);
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if (securelevel > 1)
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error = EPERM;
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break;
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case FINGERPRINT_NOENTRY: /* no entry in the list, complain */
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printf("No fingerprint for %s (dev %lu, inode %lu)\n",
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epp->ep_name, epp->ep_vap->va_fsid,
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epp->ep_vap->va_fileid);
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if (securelevel > 1)
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error = EPERM;
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break;
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case FINGERPRINT_NODEV: /* no signatures for the device, complain */
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#ifdef VERIFIED_EXEC_DEBUG
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printf("No signatures for device %lu\n",
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epp->ep_vap->va_fsid);
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#endif
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if (securelevel > 1)
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error = EPERM;
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break;
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default: /* this should never happen. */
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printf("Invalid fp_status field for vnode %p\n", vp);
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error = EPERM;
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}
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return error;
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}
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