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Differential D1331 Diff 20498 usr.bin/elf2aout/elf2aout.c

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usr.bin/elf2aout/elf2aout.c

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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE. * SUCH DAMAGE.
*/ */
#include <sys/cdefs.h> #include <sys/cdefs.h>
__FBSDID("$FreeBSD$"); __FBSDID("$FreeBSD$");
#include <sys/types.h> #include <sys/types.h>
#include <sys/capsicum.h>
#include <sys/elf64.h> #include <sys/elf64.h>
#include <sys/endian.h> #include <sys/endian.h>
#include <sys/mman.h> #include <sys/mman.h>
#include <sys/stat.h> #include <sys/stat.h>
#include <err.h> #include <err.h>
#include <errno.h>
#include <fcntl.h> #include <fcntl.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
#include <string.h> #include <string.h>
#include <unistd.h> #include <unistd.h>
#define xe16toh(x) ((data == ELFDATA2MSB) ? be16toh(x) : le16toh(x)) #define xe16toh(x) ((data == ELFDATA2MSB) ? be16toh(x) : le16toh(x))
#define xe32toh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x)) #define xe32toh(x) ((data == ELFDATA2MSB) ? be32toh(x) : le32toh(x))
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static void usage(void); static void usage(void);
/* /*
* elf to a.out converter for freebsd/sparc64 bootblocks. * elf to a.out converter for freebsd/sparc64 bootblocks.
*/ */
int int
main(int ac, char **av) main(int ac, char **av)
{ {
cap_rights_t rights;
Elf64_Half phentsize; Elf64_Half phentsize;
Elf64_Half machine; Elf64_Half machine;
Elf64_Half phnum; Elf64_Half phnum;
Elf64_Xword filesz; Elf64_Xword filesz;
Elf64_Xword memsz; Elf64_Xword memsz;
Elf64_Addr entry; Elf64_Addr entry;
Elf64_Off offset; Elf64_Off offset;
Elf64_Off phoff; Elf64_Off phoff;
Elf64_Word type; Elf64_Word type;
unsigned char data; unsigned char data;
struct stat sb; struct stat sb;
struct exec a; struct exec a;
Elf64_Phdr *p; Elf64_Phdr *p;
Elf64_Ehdr *e; Elf64_Ehdr *e;
void *v; void *v;
int efd; int efd;
int fd; int fd;
int c; int c;
int i; int i;
fd = STDIN_FILENO; fd = STDOUT_FILENO;
cemAuthorUnsubmitted
Not Done
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This is the output fd. Did this program even work without -o?

cem: This is the output fd. Did this program even work without `-o`?
while ((c = getopt(ac, av, "o:")) != -1) while ((c = getopt(ac, av, "o:")) != -1)
switch (c) { switch (c) {
case 'o': case 'o':
if ((fd = open(optarg, O_CREAT|O_RDWR, 0644)) < 0) if ((fd = open(optarg, O_CREAT|O_RDWR, 0644)) < 0)
err(1, "%s", optarg); err(1, "%s", optarg);
cap_rights_init(&rights, CAP_WRITE);
rwatsonUnsubmitted
Not Done
Inline Actions

Below, for the output descriptor, only CAP_WRITE is required. I'm not sure the CAP_FSTAT here is needed here? Or might CAP_FSTAT be needed below?

rwatson: Below, for the output descriptor, only CAP_WRITE is required. I'm not sure the CAP_FSTAT here…
if (cap_rights_limit(fd, &rights) < 0 && errno != ENOSYS)
err(1, "unable to limit rights for %s", optarg);
break; break;
case '?': case '?':
default: default:
usage(); usage();
} }
ac -= optind; ac -= optind;
av += optind; av += optind;
if (ac == 0) if (ac == 0)
usage(); usage();
if ((efd = open(*av, O_RDONLY)) < 0 || fstat(efd, &sb) < 0) if ((efd = open(*av, O_RDONLY)) < 0 || fstat(efd, &sb) < 0)
err(1, NULL); err(1, NULL);
cap_rights_init(&rights, CAP_MMAP_R);
if (cap_rights_limit(efd, &rights) < 0 && errno != ENOSYS)
err(1, "unable to limit rights for %s", *av);
rwatsonUnsubmitted
Done
Inline Actions

Leaving {stdin, stdout, stderr} in a closed state always makes me nervous, as a later operation in libc might perform I/O. I wonder if it would be better to simply set capability rights on it to 0 and leave fd 0 open?

rwatson: Leaving {stdin, stdout, stderr} in a closed state always makes me nervous, as a later operation…
/* Restrict stdio streams. */
rwatsonUnsubmitted
Done
Inline Actions

I'm actually slightly surprised that err() and friends don't require CAP_FSTAT here, in fact .. but haven't checked. The stdio stack does like to fstat() its descriptors, I thought?

rwatson: I'm actually slightly surprised that err() and friends don't require CAP_FSTAT here, in fact ..
cemAuthorUnsubmitted
Not Done
Inline Actions

I expect stdout and stderr need CAP_FSTAT. Maybe even CAP_IOCTL + the isatty(3) ioctl, if you care about output line buffering.

cem: I expect stdout and stderr need CAP_FSTAT. Maybe even CAP_IOCTL + the `isatty(3)` ioctl, if…
CAP_NONE(&rights);
if (cap_rights_limit(STDIN_FILENO, &rights) < 0 && errno != ENOSYS)
err(1, "unable to limit rights for stdin");
cap_rights_init(&rights, CAP_FSTAT, CAP_WRITE);
if ((cap_rights_limit(STDOUT_FILENO, &rights) < 0 && errno != ENOSYS) ||
(cap_rights_limit(STDERR_FILENO, &rights) < 0 && errno != ENOSYS))
err(1, "unable to limit rights for stdout/stderr");
if (cap_enter() < 0 && errno != ENOSYS)
err(1, "unable to enter capability mode");
v = mmap(NULL, sb.st_size, PROT_READ, MAP_SHARED, efd, 0); v = mmap(NULL, sb.st_size, PROT_READ, MAP_SHARED, efd, 0);
if ((e = v) == MAP_FAILED) if ((e = v) == MAP_FAILED)
err(1, NULL); err(1, NULL);
if (!IS_ELF(*e)) if (!IS_ELF(*e))
errx(1, "not an elf file"); errx(1, "not an elf file");
if (e->e_ident[EI_CLASS] != ELFCLASS64) if (e->e_ident[EI_CLASS] != ELFCLASS64)
errx(1, "wrong class"); errx(1, "wrong class");
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