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/*
* SPDX-License-Identifier: ISC
*
* Copyright (c) 2020-2021 Todd C. Miller <Todd.Miller@sudo.ws>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This is an open source non-commercial project. Dear PVS-Studio, please check it.
* PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
*/
#include <config.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include "sudo.h"
#include "sudo_edit.h"
/*
* Extend the given fd to the specified size in bytes.
* We do this to allocate disk space up-front before overwriting
* the original file with the temporary. Otherwise, we could
* run out of disk space after truncating the original file.
*/
static int
sudo_extend_file(int fd, const char *name, off_t new_size)
{
off_t old_size, size;
ssize_t nwritten;
char zeroes[BUFSIZ] = { '\0' };
debug_decl(sudo_extend_file, SUDO_DEBUG_UTIL);
if ((old_size = lseek(fd, 0, SEEK_END)) == -1) {
sudo_warn("lseek");
debug_return_int(-1);
}
sudo_debug_printf(SUDO_DEBUG_INFO, "%s: extending %s from %lld to %lld",
__func__, name, (long long)old_size, (long long)new_size);
for (size = old_size; size < new_size; size += nwritten) {
size_t len = new_size - size;
if (len > sizeof(zeroes))
len = sizeof(zeroes);
nwritten = write(fd, zeroes, len);
if (nwritten == -1) {
int serrno = errno;
if (ftruncate(fd, old_size) == -1) {
sudo_debug_printf(
SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,
"unable to truncate %s to %lld", name, (long long)old_size);
}
errno = serrno;
debug_return_int(-1);
}
}
if (lseek(fd, 0, SEEK_SET) == -1) {
sudo_warn("lseek");
debug_return_int(-1);
}
debug_return_int(0);
}
/*
* Copy the contents of src_fd into dst_fd.
* Returns 0 on success or -1 on error.
*/
int
sudo_copy_file(const char *src, int src_fd, off_t src_len, const char *dst,
int dst_fd, off_t dst_len)
{
char buf[BUFSIZ];
ssize_t nwritten, nread;
debug_decl(sudo_copy_file, SUDO_DEBUG_UTIL);
/* Prompt the user before zeroing out an existing file. */
if (dst_len > 0 && src_len == 0) {
fprintf(stderr, U_("%s: truncate %s to zero bytes? (y/n) [n] "),
getprogname(), dst);
if (fgets(buf, sizeof(buf), stdin) == NULL ||
(buf[0] != 'y' && buf[0] != 'Y')) {
sudo_warnx(U_("not overwriting %s"), dst);
debug_return_int(0);
}
}
/* Extend the file to the new size if larger before copying. */
if (dst_len > 0 && src_len > dst_len) {
if (sudo_extend_file(dst_fd, dst, src_len) == -1)
goto write_error;
}
/* Overwrite the old file with the new contents. */
while ((nread = read(src_fd, buf, sizeof(buf))) > 0) {
ssize_t off = 0;
do {
nwritten = write(dst_fd, buf + off, nread - off);
if (nwritten == -1)
goto write_error;
off += nwritten;
} while (nread > off);
}
if (nread == -1) {
sudo_warn(U_("unable to read from %s"), src);
debug_return_int(-1);
}
/* Did the file shrink? */
if (src_len < dst_len) {
/* We don't open with O_TRUNC so must truncate manually. */
if (ftruncate(dst_fd, src_len) == -1) {
sudo_debug_printf(
SUDO_DEBUG_ERROR|SUDO_DEBUG_LINENO|SUDO_DEBUG_ERRNO,
"unable to truncate %s to %lld", dst, (long long)src_len);
goto write_error;
}
}
debug_return_int(0);
write_error:
sudo_warn(U_("unable to write to %s"), dst);
debug_return_int(-1);
}
bool
sudo_check_temp_file(int tfd, const char *tfile, uid_t uid, struct stat *sb)
{
struct stat sbuf;
debug_decl(sudo_check_temp_file, SUDO_DEBUG_UTIL);
if (sb == NULL)
sb = &sbuf;
if (fstat(tfd, sb) == -1) {
sudo_warn(U_("unable to stat %s"), tfile);
debug_return_bool(false);
}
if (!S_ISREG(sb->st_mode)) {
sudo_warnx(U_("%s: not a regular file"), tfile);
debug_return_bool(false);
}
if ((sb->st_mode & ALLPERMS) != (S_IRUSR|S_IWUSR)) {
sudo_warnx(U_("%s: bad file mode: 0%o"), tfile,
(unsigned int)(sb->st_mode & ALLPERMS));
debug_return_bool(false);
}
if (sb->st_uid != uid) {
sudo_warnx(U_("%s is owned by uid %u, should be %u"),
tfile, (unsigned int)sb->st_uid, (unsigned int)uid);
debug_return_bool(false);
}
debug_return_bool(true);
}
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