7c5d4b81ab
The current approach of injecting manifest into mac_veriexec is to verify the integrity of it in userspace (veriexec (8)) and pass its entries into kernel using a char device (/dev/veriexec). This requires verifying root partition integrity in loader, for example by using memory disk and checking its hash. Otherwise if rootfs is compromised an attacker could inject their own data. This patch introduces an option to parse manifest in kernel based on envs. The loader sets manifest path and digest. EVENTHANDLER is used to launch the module right after the rootfs is mounted. It has to be done this way, since one might want to verify integrity of the init file. This means that manifest is required to be present on the root partition. Note that the envs have to be set right before boot to make sure that no one can spoof them. Submitted by: Kornel Duleba <mindal@semihalf.com> Reviewed by: sjg Obtained from: Semihalf Sponsored by: Stormshield Differential Revision: https://reviews.freebsd.org/D19281
153 lines
3.8 KiB
C
153 lines
3.8 KiB
C
/*-
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* Copyright (c) 2019 Stormshield.
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* Copyright (c) 2019 Semihalf.
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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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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* 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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* $FreeBSD$
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/stat.h>
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#include "libsecureboot-priv.h"
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#include <verify_file.h>
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/*
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* Values to pass to kernel by envs.
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*/
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static char manifest_path[MAXPATHLEN];
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static char manifest_prefix[MAXPATHLEN];
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static char manifest_hash[2 * br_sha256_SIZE + 2];
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static int manifest_present = 0;
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/*
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* Verify and pass manifest path and digest to kernel through envs.
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* The paths in manifest can be either absolute,
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* or "prefix", if exists will be added to the ones that are not.
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*/
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int
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pass_manifest(const char *path, const char *prefix)
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{
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char *content;
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struct stat st;
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unsigned char digest[br_sha256_SIZE];
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const br_hash_class *md;
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br_hash_compat_context ctx;
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int rc;
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content = NULL;
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md = &br_sha256_vtable;
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if (strnlen(path, MAXPATHLEN) == MAXPATHLEN ||
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strnlen(prefix, MAXPATHLEN) == MAXPATHLEN)
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return (EINVAL);
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rc = stat(path, &st);
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if (rc != 0)
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goto out;
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if (!S_ISREG(st.st_mode)) {
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rc = EINVAL;
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goto out;
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}
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rc = is_verified(&st);
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if (rc != VE_NOT_CHECKED && rc != VE_VERIFIED) {
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rc = EPERM;
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goto out;
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}
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if (rc == VE_VERIFIED)
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content = read_file(path, NULL);
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else
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content = (char *)verify_signed(path, VEF_VERBOSE);
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if (content == NULL) {
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add_verify_status(&st, VE_FINGERPRINT_WRONG);
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rc = EIO;
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goto out;
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}
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add_verify_status(&st, VE_VERIFIED);
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md->init(&ctx.vtable);
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md->update(&ctx.vtable, content, st.st_size);
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md->out(&ctx.vtable, digest);
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if (prefix == NULL)
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manifest_prefix[0] = '\0';
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else
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strcpy(manifest_prefix, prefix);
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strcpy(manifest_path, path);
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hexdigest(manifest_hash, 2 * br_sha256_SIZE + 2,
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digest, br_sha256_SIZE);
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manifest_hash[2*br_sha256_SIZE] = '\0';
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manifest_present = 1;
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rc = 0;
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out:
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if (content != NULL)
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free(content);
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return (rc);
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}
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/*
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* Set appropriate envs to inform kernel about manifest location and digest.
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* This should be called right before boot so that envs can't be replaced.
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*/
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int
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pass_manifest_export_envs()
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{
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int rc;
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/* If we have nothing to pass make sure that envs are empty. */
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if (!manifest_present) {
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unsetenv("veriexec.manifest_path");
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unsetenv("veriexec.manifest_hash");
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unsetenv("veriexec.manifest_prefix");
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return (0);
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}
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rc = setenv("veriexec.manifest_path", manifest_path, 1);
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if (rc != 0)
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return (rc);
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rc = setenv("veriexec.manifest_hash", manifest_hash, 1);
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if (rc != 0) {
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unsetenv("veriexec.manifest_path");
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return (rc);
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}
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if (manifest_prefix[0] != '\0')
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rc = setenv("veriexec.manifest_prefix", manifest_prefix, 1);
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return (rc);
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}
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