svn commit: r352797 - head/tools/tools/controlelf
Ed Maste
emaste at FreeBSD.org
Fri Sep 27 16:27:54 UTC 2019
Author: emaste
Date: Fri Sep 27 16:27:52 2019
New Revision: 352797
URL: https://svnweb.freebsd.org/changeset/base/352797
Log:
Add tool to modify ELF binary feature control bits
This will allow feature control bits (e.g. for ASLR, PROT_MAX) to be
inspected or modified.
Some clean-up and additional work is likely still required, but we can
iterate on this in the tree.
Submitted by: Bora Özarslan <borako.ozarslan at gmail.com>
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D19290
Added:
head/tools/tools/controlelf/
head/tools/tools/controlelf/Makefile (contents, props changed)
head/tools/tools/controlelf/controlelf.1 (contents, props changed)
head/tools/tools/controlelf/controlelf.c (contents, props changed)
Added: head/tools/tools/controlelf/Makefile
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/tools/tools/controlelf/Makefile Fri Sep 27 16:27:52 2019 (r352797)
@@ -0,0 +1,14 @@
+# $FreeBSD$
+
+ELFTCDIR= ${SRCTOP}/contrib/elftoolchain
+
+PROG= controlelf
+SRCS= controlelf.c
+
+LIBADD= elftc elf
+
+CFLAGS+=-I${ELFTCDIR}/libelftc -I${ELFTCDIR}/common
+
+WARNS?= 6
+
+.include <bsd.prog.mk>
Added: head/tools/tools/controlelf/controlelf.1
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/tools/tools/controlelf/controlelf.1 Fri Sep 27 16:27:52 2019 (r352797)
@@ -0,0 +1,92 @@
+.\" Copyright 2019 The FreeBSD Foundation.
+.\"
+.\" This software was developed by Bora Ozarslan under sponsorship from
+.\" the FreeBSD Foundation.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS''
+.\" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd February 21, 2019
+.Dt CONTROLELF 1
+.Os
+.Sh NAME
+.Nm controlelf
+.Nd change an ELF binary's control features
+.Sh SYNOPSIS
+.Nm
+.Op Fl h | Fl -help
+.Op Fl l
+.Op Fl e Ar featurelist
+.Ar
+.Sh DESCRIPTION
+The
+.Nm
+utility modifies an ELF binary to change it's control features.
+.Pp
+The options are as follows:
+.Bl -tag -width indent
+.It Fl h | Fl -help
+Print a usage message and exit.
+.It Fl l
+Writes the list of all known ELF types to standard output.
+.It Fl e Ar featurelist
+Edit features from the given comma separated list
+.Ar featurelist .
+.Ar featurelist
+starts with one of the three modes:
+.Dq Li +
+to turn on the features,
+.Dq Li -
+to turn off the features,
+.Dq Li =
+to only turn on the given features.
+Followed by a comma separated features.
+.El
+.Pp
+If
+.Fl e ,
+option wasn't specified,
+.Nm
+will display the current control features for the files named by the arguments
+.Ar .
+.Sh EXIT STATUS
+Exit status is 0 on success, and 1 if the command
+fails if a file does not exist, is too short,
+or fails to find or edit features note.
+.Sh EXAMPLES
+The following is an example of a typical usage
+of the
+.Nm
+command:
+.Bd -literal -offset indent
+controlelf file
+controlelf -e +aslr file
+.Ed
+.Sh HISTORY
+The
+.Nm
+manual page first appeared in
+.Fx 13.0 .
+.Sh AUTHORS
+This manual page was written by
+.An Bora Ozarslan Mt borako.ozarslan at gmail.com .
Added: head/tools/tools/controlelf/controlelf.c
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/tools/tools/controlelf/controlelf.c Fri Sep 27 16:27:52 2019 (r352797)
@@ -0,0 +1,374 @@
+/*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 2019 The FreeBSD Foundation.
+ *
+ * This software was developed by Bora Ozarslan under sponsorship from
+ * the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer
+ * in this position and unchanged.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/param.h>
+#include <sys/elf_common.h>
+#include <sys/stat.h>
+
+#include <err.h>
+#include <fcntl.h>
+#include <gelf.h>
+#include <getopt.h>
+#include <libelf.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "_elftc.h"
+
+__FBSDID("$FreeBSD$");
+
+static bool convert_to_feature_val(char*, u_int32_t*);
+static bool edit_file_features(Elf *, int, int, char*);
+static bool get_file_features(Elf *, int, int, u_int32_t *, u_int64_t *);
+static void print_features(void);
+static bool print_file_features(Elf *, int, int, char*);
+static void usage(void);
+
+struct ControlFeatures {
+ const char *alias;
+ unsigned long featureVal;
+ const char *desc;
+};
+
+static struct ControlFeatures featurelist[] = {
+ { "aslr", NT_FREEBSD_FCTL_ASLR_DISABLE, "Disable ASLR" }
+};
+
+static struct option controlelf_longopts[] = {
+ { "help", no_argument, NULL, 'h' },
+ { NULL, 0, NULL, 0 }
+};
+
+int
+main(int argc, char **argv)
+{
+ GElf_Ehdr ehdr;
+ Elf *elf;
+ Elf_Kind kind;
+ int ch, fd, listed, editfeatures, retval;
+ char *features;
+
+ listed = 0;
+ editfeatures = 0;
+ retval = 0;
+
+ if (elf_version(EV_CURRENT) == EV_NONE)
+ errx(EXIT_FAILURE, "elf_version error");
+
+ while ((ch = getopt_long(argc, argv, "hle:", controlelf_longopts,
+ NULL)) != -1) {
+ switch (ch) {
+ case 'l':
+ print_features();
+ listed = 1;
+ break;
+ case 'e':
+ features = optarg;
+ editfeatures = 1;
+ break;
+ case 'h':
+ usage();
+ break;
+ default:
+ usage();
+ }
+ }
+ argc -= optind;
+ argv += optind;
+ if (!argc) {
+ if (listed)
+ exit(0);
+ else {
+ warnx("no file(s) specified");
+ usage();
+ }
+ }
+
+ while (argc) {
+ elf = NULL;
+
+ if ((fd = open(argv[0], editfeatures ? O_RDWR :
+ O_RDONLY, 0)) < 0) {
+ warn("error opening file %s", argv[0]);
+ retval = 1;
+ goto fail;
+ }
+
+ if ((elf = elf_begin(fd, ELF_C_READ, NULL)) == NULL) {
+ warnx("elf_begin failed: %s", elf_errmsg(-1));
+ retval = 1;
+ goto fail;
+ }
+
+ if ((kind = elf_kind(elf)) != ELF_K_ELF) {
+ if (kind == ELF_K_AR)
+ warnx("file '%s' is an archive.", argv[0]);
+ else
+ warnx("file '%s' is not an ELF file.",
+ argv[0]);
+ retval = 1;
+ goto fail;
+ }
+
+ if (gelf_getehdr(elf, &ehdr) == NULL) {
+ warnx("gelf_getehdr: %s", elf_errmsg(-1));
+ retval = 1;
+ goto fail;
+ }
+
+ if (!editfeatures) {
+ if (!print_file_features(elf, ehdr.e_phnum, fd, argv[0])) {
+ retval = 1;
+ goto fail;
+ }
+ } else if (!edit_file_features(elf, ehdr.e_phnum, fd, features)) {
+ retval = 1;
+ goto fail;
+ }
+fail:
+ if (elf != NULL)
+ elf_end(elf);
+
+ if (fd >= 0)
+ close(fd);
+
+ argc--;
+ argv++;
+ }
+
+ return (retval);
+}
+
+#define USAGE_MESSAGE "\
+Usage: %s [options] file...\n\
+ Set or display the control features for an ELF object.\n\n\
+ Supported options are:\n\
+ -l List known control features.\n\
+ -e [+-=]feature,list Edit features from a comma separated list.\n\
+ -h | --help Print a usage message and exit.\n"
+
+static void
+usage(void)
+{
+
+ fprintf(stderr, USAGE_MESSAGE, ELFTC_GETPROGNAME());
+ exit(1);
+}
+
+static bool
+convert_to_feature_val(char* feature_str, u_int32_t* feature_val)
+{
+ char *feature_input, *feature;
+ int i, len;
+ u_int32_t input;
+ bool add, set;
+
+ add = set = false;
+ input = 0;
+
+ if (feature_str[0] == '+')
+ add = true;
+ else if (feature_str[0] == '=')
+ set = true;
+ else if (feature_str[0] != '-') {
+ warnx("'%c' is not an operator. Use instead '+', '-', '='.",
+ feature_str[0]);
+ return (false);
+ }
+
+ feature_input = feature_str + 1;
+ len = nitems(featurelist);
+ while ((feature = strsep(&feature_input, ",")) != NULL) {
+ for (i = 0; i < len; ++i) {
+ if (strcmp(featurelist[i].alias, feature) == 0) {
+ input |= featurelist[i].featureVal;
+ break;
+ }
+ }
+ if (i == len) {
+ warnx("%s is not a valid feature.", feature);
+ return (false);
+ }
+ }
+
+ if (add) {
+ *feature_val |= input;
+ } else if (set) {
+ *feature_val = input;
+ } else {
+ *feature_val -= (*feature_val) & input;
+ }
+ return (true);
+}
+
+static bool
+edit_file_features(Elf *elf, int phcount, int fd, char *val)
+{
+ u_int32_t features;
+ u_int64_t off;
+
+ if (!get_file_features(elf, phcount, fd, &features, &off)) {
+ warnx("No control features note on the file.\n");
+ return (false);
+ }
+
+ if (!convert_to_feature_val(val, &features))
+ return (false);
+
+ lseek(fd, off, SEEK_SET);
+ write(fd, &features, sizeof(u_int32_t));
+ return (true);
+}
+
+static void
+print_features(void)
+{
+ size_t i;
+
+ printf("Known features are:\n");
+ for (i = 0; i < nitems(featurelist); ++i)
+ printf("%s\t\t %s\n", featurelist[i].alias,
+ featurelist[i].desc);
+}
+
+static bool
+print_file_features(Elf *elf, int phcount, int fd, char *filename) {
+ u_int32_t features;
+ unsigned long i;
+
+ if (!get_file_features(elf, phcount, fd, &features, NULL)) {
+ return (false);
+ }
+
+ printf("File '%s' features:\n", filename);
+ for (i = 0; i < nitems(featurelist); ++i) {
+ printf("%s\t\t'%s' is ", featurelist[i].alias,
+ featurelist[i].desc);
+
+ if ((featurelist[i].featureVal & features) == 0)
+ printf("un");
+
+ printf("set.\n");
+ }
+ return (true);
+}
+
+static bool
+get_file_features(Elf *elf, int phcount, int fd, u_int32_t *features, u_int64_t *off)
+{
+ GElf_Phdr phdr;
+ Elf_Note note;
+ unsigned long read_total;
+ int namesz, descsz, i;
+ char *name;
+ ssize_t size;
+
+ /*
+ * Go through each program header to find one that is of type PT_NOTE
+ * and has a note for feature control.
+ */
+ for (i = 0; i < phcount; ++i) {
+ if (gelf_getphdr(elf, i, &phdr) == NULL) {
+ warnx("gelf_getphdr failed: %s", elf_errmsg(-1));
+ return (false);
+ }
+
+ if (phdr.p_type != PT_NOTE)
+ continue;
+
+ if (lseek(fd, phdr.p_offset, SEEK_SET) < 0) {
+ warn("lseek() failed:");
+ return (false);
+ }
+
+ read_total = 0;
+ while (read_total < phdr.p_filesz) {
+ size = read(fd, ¬e, sizeof(note));
+ if (size < (ssize_t)sizeof(note)) {
+ warn("read() failed:");
+ return (false);
+ }
+ read_total += sizeof(note);
+
+ /*
+ * XXX: Name and descriptor are 4 byte aligned, however,
+ * the size given doesn't include the padding.
+ */
+ namesz = roundup2(note.n_namesz, 4);
+ name = malloc(namesz);
+ if (name == NULL) {
+ warn("malloc() failed.\n");
+ return (false);
+ }
+ descsz = roundup2(note.n_descsz, 4);
+ size = read(fd, name, namesz);
+ read_total += namesz;
+
+ if (note.n_namesz != 8 ||
+ strncmp("FreeBSD", name, 7) != 0 ||
+ note.n_type != NT_FREEBSD_FEATURE_CTL) {
+ /* Not the right note. Skip the description */
+ if (lseek(fd, descsz, SEEK_CUR) < 0) {
+ warn("lseek() failed.\n");
+ free(name);
+ return (false);
+ }
+ read_total += descsz;
+ free(name);
+ continue;
+ }
+
+ if (note.n_descsz < sizeof(u_int32_t)) {
+ warnx("Feature descriptor can't "
+ "be less than 4 bytes");
+ free(name);
+ return (false);
+ }
+
+ /*
+ * XXX: For now we look at only 4 bytes of the
+ * descriptor. This should respect descsz.
+ */
+ if (note.n_descsz > sizeof(u_int32_t))
+ warnx("Feature note is bigger than expected.");
+ read(fd, features, sizeof(u_int32_t));
+ if (off != NULL)
+ *off = phdr.p_offset + read_total;
+ free(name);
+ return (true);
+ }
+ }
+
+ warnx("Couldn't find a note header with control feature note.");
+ return (false);
+}
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