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Fix handling of rights on stdio streams, take two.

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Split the rights-limiting code into two cases: if one of the input
files isn't a regular file, use caph_limit_stream(3) instead of
open-coding the same logic; if both input files are regular files,
and the initial attempts to map them succeed, we limit the rights on
those files to CAP_MMAP_R.

Add a regression test for PR 234885.

PR:		234885
Reviewed by:	delphij
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D19216
This commit is contained in:
Mark Johnston 2019-02-25 19:47:27 +00:00
parent 2b6010705c
commit 2528b7e2cb
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=344551
4 changed files with 38 additions and 43 deletions
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46
usr.bin/cmp/cmp.c
View File

@ -45,7 +45,6 @@ static char sccsid[] = "@(#)cmp.c 8.3 (Berkeley) 4/2/94";
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/capsicum.h>
#include <sys/stat.h>
#include <capsicum_helpers.h>
@ -80,8 +79,6 @@ main(int argc, char *argv[])
off_t skip1, skip2;
int ch, fd1, fd2, oflag, special;
const char *file1, *file2;
cap_rights_t rights;
uint32_t fcntls;
oflag = O_RDONLY;
while ((ch = getopt_long(argc, argv, "+hlsxz", long_opts, NULL)) != -1)
@ -116,14 +113,19 @@ main(int argc, char *argv[])
if (argc < 2 || argc > 4)
usage();
/* Don't limit rights on stdin since it may be one of the inputs. */
if (caph_limit_stream(STDOUT_FILENO, CAPH_WRITE | CAPH_IGNORE_EBADF))
err(ERR_EXIT, "unable to limit rights on stdout");
if (caph_limit_stream(STDERR_FILENO, CAPH_WRITE | CAPH_IGNORE_EBADF))
err(ERR_EXIT, "unable to limit rights on stderr");
/* Backward compatibility -- handle "-" meaning stdin. */
special = 0;
if (strcmp(file1 = argv[0], "-") == 0) {
special = 1;
fd1 = 0;
fd1 = STDIN_FILENO;
file1 = "stdin";
}
else if ((fd1 = open(file1, oflag, 0)) < 0 && errno != EMLINK) {
} else if ((fd1 = open(file1, oflag, 0)) < 0 && errno != EMLINK) {
if (!sflag)
err(ERR_EXIT, "%s", file1);
else
@ -134,10 +136,9 @@ main(int argc, char *argv[])
errx(ERR_EXIT,
"standard input may only be specified once");
special = 1;
fd2 = 0;
fd2 = STDIN_FILENO;
file2 = "stdin";
}
else if ((fd2 = open(file2, oflag, 0)) < 0 && errno != EMLINK) {
} else if ((fd2 = open(file2, oflag, 0)) < 0 && errno != EMLINK) {
if (!sflag)
err(ERR_EXIT, "%s", file2);
else
@ -162,34 +163,9 @@ main(int argc, char *argv[])
exit(ERR_EXIT);
}
cap_rights_init(&rights, CAP_FCNTL, CAP_FSTAT, CAP_MMAP_R);
if (caph_rights_limit(fd1, &rights) < 0)
err(ERR_EXIT, "unable to limit rights for %s", file1);
if (caph_rights_limit(fd2, &rights) < 0)
err(ERR_EXIT, "unable to limit rights for %s", file2);
/* Required for fdopen(3). */
fcntls = CAP_FCNTL_GETFL;
if (caph_fcntls_limit(fd1, fcntls) < 0)
err(ERR_EXIT, "unable to limit fcntls for %s", file1);
if (caph_fcntls_limit(fd2, fcntls) < 0)
err(ERR_EXIT, "unable to limit fcntls for %s", file2);
if (!special) {
cap_rights_init(&rights);
if (caph_rights_limit(STDIN_FILENO, &rights) < 0) {
err(ERR_EXIT, "unable to limit stdio");
}
}
if (caph_limit_stdout() == -1 || caph_limit_stderr() == -1)
err(ERR_EXIT, "unable to limit stdio");
/* FD rights are limited in c_special() and c_regular(). */
caph_cache_catpages();
if (caph_enter() < 0)
err(ERR_EXIT, "unable to enter capability mode");
if (!special) {
if (fstat(fd1, &sb1)) {
if (!sflag)

25
usr.bin/cmp/regular.c
View File

@ -42,6 +42,7 @@ __FBSDID("$FreeBSD$");
#include <sys/mman.h>
#include <sys/stat.h>
#include <capsicum_helpers.h>
#include <err.h>
#include <limits.h>
#include <signal.h>
@ -61,12 +62,13 @@ void
c_regular(int fd1, const char *file1, off_t skip1, off_t len1,
int fd2, const char *file2, off_t skip2, off_t len2)
{
struct sigaction act, oact;
cap_rights_t rights;
u_char ch, *p1, *p2, *m1, *m2, *e1, *e2;
off_t byte, length, line;
int dfound;
off_t pagemask, off1, off2;
size_t pagesize;
struct sigaction act, oact;
int dfound;
if (skip1 > len1)
eofmsg(file1);
@ -78,12 +80,6 @@ c_regular(int fd1, const char *file1, off_t skip1, off_t len1,
if (sflag && len1 != len2)
exit(DIFF_EXIT);
sigemptyset(&act.sa_mask);
act.sa_flags = SA_NODEFER;
act.sa_handler = segv_handler;
if (sigaction(SIGSEGV, &act, &oact))
err(ERR_EXIT, "sigaction()");
pagesize = getpagesize();
pagemask = (off_t)pagesize - 1;
off1 = ROUNDPAGE(skip1);
@ -102,6 +98,19 @@ c_regular(int fd1, const char *file1, off_t skip1, off_t len1,
return;
}
if (caph_rights_limit(fd1, cap_rights_init(&rights, CAP_MMAP_R)) < 0)
err(1, "unable to limit rights for %s", file1);
if (caph_rights_limit(fd2, cap_rights_init(&rights, CAP_MMAP_R)) < 0)
err(1, "unable to limit rights for %s", file2);
if (caph_enter() < 0)
err(ERR_EXIT, "unable to enter capability mode");
sigemptyset(&act.sa_mask);
act.sa_flags = SA_NODEFER;
act.sa_handler = segv_handler;
if (sigaction(SIGSEGV, &act, &oact))
err(ERR_EXIT, "sigaction()");
dfound = 0;
e1 = m1 + MMAP_CHUNK;
e2 = m2 + MMAP_CHUNK;

8
usr.bin/cmp/special.c
View File

@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <capsicum_helpers.h>
#include <err.h>
#include <stdlib.h>
#include <stdio.h>
@ -55,6 +56,13 @@ c_special(int fd1, const char *file1, off_t skip1,
FILE *fp1, *fp2;
int dfound;
if (caph_limit_stream(fd1, CAPH_READ) < 0)
err(ERR_EXIT, "caph_limit_stream(%s)", file1);
if (caph_limit_stream(fd2, CAPH_READ) < 0)
err(ERR_EXIT, "caph_limit_stream(%s)", file2);
if (caph_enter() < 0)
err(ERR_EXIT, "unable to enter capability mode");
if ((fp1 = fdopen(fd1, "r")) == NULL)
err(ERR_EXIT, "%s", file1);
if ((fp2 = fdopen(fd2, "r")) == NULL)

2
usr.bin/cmp/tests/cmp_test2.sh
View File

@ -35,6 +35,8 @@ special_body() {
atf_check -s exit:0 -o empty -e empty -x "cat a | cmp - a"
atf_check -s exit:1 -o not-empty -e empty -x "cat b | cmp a -"
atf_check -s exit:1 -o not-empty -e empty -x "cat b | cmp - a"
atf_check -s exit:0 -o empty -e empty -x "cmp a a <&-"
}
atf_test_case symlink