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ktrdump(8): Capsicumify

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We restrict the (optional) input file and output files. It would be
nice to restrict the KVM files, but that's up to libkvm.

We wait until after kvm_nlist() is invoked to cap_enter() because
kldsym() isn't supported in the Capsicum sandbox.

Feedback from:	emaste@ (earlier versions)
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D7921
This commit is contained in:
Conrad Meyer 2016-12-16 01:59:28 +00:00
parent 20502a13a0
commit 208a859459
1 changed files with 32 additions and 0 deletions
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32
usr.bin/ktrdump/ktrdump.c
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@ -29,11 +29,14 @@
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/capsicum.h>
#include <sys/ktr.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <capsicum_helpers.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <kvm.h>
#include <limits.h>
@ -70,6 +73,7 @@ static int hflag;
static char corefile[PATH_MAX];
static char execfile[PATH_MAX];
static char outfile[PATH_MAX] = "stdout";
static char desc[SBUFLEN];
static char errbuf[_POSIX2_LINE_MAX];
@ -87,6 +91,7 @@ main(int ac, char **av)
struct ktr_entry *buf;
uintmax_t tlast, tnow;
unsigned long bufptr;
cap_rights_t rights;
struct stat sb;
kvm_t *kd;
FILE *out;
@ -122,6 +127,11 @@ main(int ac, char **av)
iflag = 1;
if ((in = open(optarg, O_RDONLY)) == -1)
err(1, "%s", optarg);
cap_rights_init(&rights, CAP_FSTAT, CAP_MMAP_R);
if (cap_rights_limit(in, &rights) < 0 &&
errno != ENOSYS)
err(1, "unable to limit rights for %s",
optarg);
break;
case 'M':
case 'm':
@ -133,6 +143,7 @@ main(int ac, char **av)
case 'o':
if ((out = fopen(optarg, "w")) == NULL)
err(1, "%s", optarg);
strlcpy(outfile, optarg, sizeof(outfile));
break;
case 'q':
qflag++;
@ -155,6 +166,10 @@ main(int ac, char **av)
if (ac != 0)
usage();
cap_rights_init(&rights, CAP_FSTAT, CAP_WRITE);
if (cap_rights_limit(fileno(out), &rights) < 0 && errno != ENOSYS)
err(1, "unable to limit rights for %s", outfile);
/*
* Open our execfile and corefile, resolve needed symbols and read in
* the trace buffer.
@ -162,11 +177,28 @@ main(int ac, char **av)
if ((kd = kvm_openfiles(Nflag ? execfile : NULL,
Mflag ? corefile : NULL, NULL, O_RDONLY, errbuf)) == NULL)
errx(1, "%s", errbuf);
/*
* Cache NLS data, for strerror, for err(3), before entering capability
* mode.
*/
caph_cache_catpages();
if (kvm_nlist(kd, nl) != 0 ||
kvm_read(kd, nl[0].n_value, &version, sizeof(version)) == -1)
errx(1, "%s", kvm_geterr(kd));
if (version != KTR_VERSION)
errx(1, "ktr version mismatch");
/*
* Enter Capsicum sandbox.
*
* kvm_nlist() above uses kldsym(2) for native kernels, and that isn't
* allowed in the sandbox.
*/
if (cap_enter() < 0 && errno != ENOSYS)
err(1, "unable to enter capability mode");
if (iflag) {
if (fstat(in, &sb) == -1)
errx(1, "stat");