diff options
Diffstat (limited to 'src/copy_file.c')
| -rw-r--r-- | src/copy_file.c | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/src/copy_file.c b/src/copy_file.c new file mode 100644 index 0000000..6713338 --- /dev/null +++ b/src/copy_file.c @@ -0,0 +1,169 @@ +/* + * 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); +} |