tar,unzip: postpone creation of symlinks with "suspicious" targets
This mostly reverts commit bc9bbeb2b8
"libarchive: do not extract unsafe symlinks unless $EXTRACT_UNSAFE_SYMLINKS=1"
Users report that it is somewhat too restrictive. See
https://bugs.busybox.net/show_bug.cgi?id=8411
In particular, this interferes with unpacking of busybox-based
filesystems with links like "sbin/applet" -> "../bin/busybox".
The change is made smaller by deleting ARCHIVE_EXTRACT_QUIET flag -
it is unused since 2010, and removing conditionals on it
allows commonalizing some error message codes.
function old new delta
create_or_remember_symlink - 94 +94
create_symlinks_from_list - 64 +64
tar_main 1002 1006 +4
unzip_main 2732 2724 -8
data_extract_all 984 891 -93
unsafe_symlink_target 147 - -147
------------------------------------------------------------------------------
(add/remove: 2/1 grow/shrink: 1/2 up/down: 162/-248) Total: -86 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
parent
95121d98e6
commit
a84db18fc7
@ -107,9 +107,7 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
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}
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}
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else if (existing_sb.st_mtime >= file_header->mtime) {
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if (!(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
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&& !S_ISDIR(file_header->mode)
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) {
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if (!S_ISDIR(file_header->mode)) {
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bb_error_msg("%s not created: newer or "
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"same age file exists", dst_name);
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}
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@ -125,7 +123,7 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
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/* Handle hard links separately */
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if (hard_link) {
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res = link(hard_link, dst_name);
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if (res != 0 && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)) {
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if (res != 0) {
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/* shared message */
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bb_perror_msg("can't create %slink '%s' to '%s'",
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"hard", dst_name, hard_link
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@ -165,10 +163,9 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
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}
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case S_IFDIR:
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res = mkdir(dst_name, file_header->mode);
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if ((res == -1)
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if ((res != 0)
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&& (errno != EISDIR) /* btw, Linux doesn't return this */
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&& (errno != EEXIST)
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&& !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
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) {
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bb_perror_msg("can't make dir %s", dst_name);
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}
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@ -198,27 +195,16 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
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*
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* Untarring bug.tar would otherwise place evil.py in '/tmp'.
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*/
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if (!unsafe_symlink_target(file_header->link_target)) {
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res = symlink(file_header->link_target, dst_name);
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if (res != 0
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&& !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
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) {
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/* shared message */
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bb_perror_msg("can't create %slink '%s' to '%s'",
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"sym",
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dst_name, file_header->link_target
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);
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}
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}
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create_or_remember_symlink(&archive_handle->symlink_placeholders,
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file_header->link_target,
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dst_name);
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break;
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case S_IFSOCK:
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case S_IFBLK:
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case S_IFCHR:
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case S_IFIFO:
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res = mknod(dst_name, file_header->mode, file_header->device);
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if ((res == -1)
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&& !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)
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) {
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if (res != 0) {
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bb_perror_msg("can't create node %s", dst_name);
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}
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break;
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@ -5,44 +5,37 @@
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#include "libbb.h"
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#include "bb_archive.h"
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int FAST_FUNC unsafe_symlink_target(const char *target)
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void FAST_FUNC create_or_remember_symlink(llist_t **symlink_placeholders,
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const char *target,
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const char *linkname)
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{
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const char *dot;
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if (target[0] == '/') {
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const char *var;
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unsafe:
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var = getenv("EXTRACT_UNSAFE_SYMLINKS");
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if (var) {
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if (LONE_CHAR(var, '1'))
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return 0; /* pretend it's safe */
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return 1; /* "UNSAFE!" */
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}
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bb_error_msg("skipping unsafe symlink to '%s' in archive,"
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" set %s=1 to extract",
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target,
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"EXTRACT_UNSAFE_SYMLINKS"
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if (target[0] == '/' || strstr(target, "..")) {
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llist_add_to(symlink_placeholders,
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xasprintf("%s%c%s", linkname, '\0', target)
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);
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/* Prevent further messages */
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setenv("EXTRACT_UNSAFE_SYMLINKS", "0", 0);
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return 1; /* "UNSAFE!" */
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return;
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}
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dot = target;
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for (;;) {
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dot = strchr(dot, '.');
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if (!dot)
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return 0; /* safe target */
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/* Is it a path component starting with ".."? */
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if ((dot[1] == '.')
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&& (dot == target || dot[-1] == '/')
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/* Is it exactly ".."? */
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&& (dot[2] == '/' || dot[2] == '\0')
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) {
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goto unsafe;
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}
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/* NB: it can even be trailing ".", should only add 1 */
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dot += 1;
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if (symlink(target, linkname) != 0) {
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/* shared message */
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bb_perror_msg_and_die("can't create %slink '%s' to '%s'",
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"sym", linkname, target
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);
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}
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}
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void FAST_FUNC create_symlinks_from_list(llist_t *list)
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{
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while (list) {
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char *target;
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target = list->data + strlen(list->data) + 1;
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if (symlink(target, list->data)) {
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/* shared message */
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bb_error_msg_and_die("can't create %slink '%s' to '%s'",
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"sym",
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list->data, target
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);
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}
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list = list->link;
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}
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}
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@ -1244,6 +1244,8 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
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while (get_header_tar(tar_handle) == EXIT_SUCCESS)
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bb_got_signal = EXIT_SUCCESS; /* saw at least one header, good */
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create_symlinks_from_list(tar_handle->symlink_placeholders);
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/* Check that every file that should have been extracted was */
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while (tar_handle->accept) {
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if (!find_list_entry(tar_handle->reject, tar_handle->accept->data)
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@ -345,7 +345,9 @@ static void unzip_create_leading_dirs(const char *fn)
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}
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#if ENABLE_FEATURE_UNZIP_CDF
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static void unzip_extract_symlink(zip_header_t *zip, const char *dst_fn)
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static void unzip_extract_symlink(llist_t **symlink_placeholders,
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zip_header_t *zip,
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const char *dst_fn)
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{
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char *target;
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@ -370,15 +372,9 @@ static void unzip_extract_symlink(zip_header_t *zip, const char *dst_fn)
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target[xstate.mem_output_size] = '\0';
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#endif
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}
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if (!unsafe_symlink_target(target)) {
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//TODO: libbb candidate
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if (symlink(target, dst_fn)) {
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/* shared message */
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bb_perror_msg_and_die("can't create %slink '%s' to '%s'",
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"sym", dst_fn, target
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);
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}
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}
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create_or_remember_symlink(symlink_placeholders,
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target,
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dst_fn);
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free(target);
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}
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#endif
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@ -490,6 +486,9 @@ int unzip_main(int argc, char **argv)
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llist_t *zaccept = NULL;
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llist_t *zreject = NULL;
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char *base_dir = NULL;
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#if ENABLE_FEATURE_UNZIP_CDF
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llist_t *symlink_placeholders = NULL;
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#endif
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int i;
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char key_buf[80]; /* must match size used by my_fgets80 */
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@ -954,7 +953,7 @@ int unzip_main(int argc, char **argv)
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#if ENABLE_FEATURE_UNZIP_CDF
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if (S_ISLNK(file_mode)) {
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if (dst_fd != STDOUT_FILENO) /* not -p? */
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unzip_extract_symlink(&zip, dst_fn);
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unzip_extract_symlink(&symlink_placeholders, &zip, dst_fn);
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} else
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#endif
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{
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@ -990,6 +989,10 @@ int unzip_main(int argc, char **argv)
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total_entries++;
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}
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#if ENABLE_FEATURE_UNZIP_CDF
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create_symlinks_from_list(symlink_placeholders);
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#endif
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if ((opts & OPT_l) && quiet <= 1) {
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if (!verbose) {
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// " Length Date Time Name\n"
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@ -64,6 +64,9 @@ typedef struct archive_handle_t {
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/* Currently processed file's header */
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file_header_t *file_header;
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/* List of symlink placeholders */
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llist_t *symlink_placeholders;
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/* Process the header component, e.g. tar -t */
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void FAST_FUNC (*action_header)(const file_header_t *);
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@ -119,15 +122,14 @@ typedef struct archive_handle_t {
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#define ARCHIVE_RESTORE_DATE (1 << 0)
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#define ARCHIVE_CREATE_LEADING_DIRS (1 << 1)
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#define ARCHIVE_UNLINK_OLD (1 << 2)
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#define ARCHIVE_EXTRACT_QUIET (1 << 3)
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#define ARCHIVE_EXTRACT_NEWER (1 << 4)
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#define ARCHIVE_DONT_RESTORE_OWNER (1 << 5)
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#define ARCHIVE_DONT_RESTORE_PERM (1 << 6)
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#define ARCHIVE_NUMERIC_OWNER (1 << 7)
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#define ARCHIVE_O_TRUNC (1 << 8)
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#define ARCHIVE_REMEMBER_NAMES (1 << 9)
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#define ARCHIVE_EXTRACT_NEWER (1 << 3)
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#define ARCHIVE_DONT_RESTORE_OWNER (1 << 4)
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#define ARCHIVE_DONT_RESTORE_PERM (1 << 5)
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#define ARCHIVE_NUMERIC_OWNER (1 << 6)
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#define ARCHIVE_O_TRUNC (1 << 7)
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#define ARCHIVE_REMEMBER_NAMES (1 << 8)
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#if ENABLE_RPM
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#define ARCHIVE_REPLACE_VIA_RENAME (1 << 10)
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#define ARCHIVE_REPLACE_VIA_RENAME (1 << 9)
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#endif
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@ -197,7 +199,10 @@ void seek_by_jump(int fd, off_t amount) FAST_FUNC;
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void seek_by_read(int fd, off_t amount) FAST_FUNC;
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const char *strip_unsafe_prefix(const char *str) FAST_FUNC;
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int unsafe_symlink_target(const char *target) FAST_FUNC;
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void create_or_remember_symlink(llist_t **symlink_placeholders,
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const char *target,
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const char *linkname) FAST_FUNC;
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void create_symlinks_from_list(llist_t *list) FAST_FUNC;
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void data_align(archive_handle_t *archive_handle, unsigned boundary) FAST_FUNC;
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const llist_t *find_list_entry(const llist_t *list, const char *filename) FAST_FUNC;
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@ -279,7 +279,7 @@ optional UUDECODE FEATURE_TAR_AUTODETECT FEATURE_SEAMLESS_BZ2
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testing "tar does not extract into symlinks" "\
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>>/tmp/passwd && uudecode -o input && tar xf input 2>&1 && rm passwd; cat /tmp/passwd; echo \$?
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" "\
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tar: skipping unsafe symlink to '/tmp/passwd' in archive, set EXTRACT_UNSAFE_SYMLINKS=1 to extract
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tar: can't create symlink 'passwd' to '/tmp/passwd'
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0
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" \
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"" "\
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@ -299,7 +299,7 @@ optional UUDECODE FEATURE_TAR_AUTODETECT FEATURE_SEAMLESS_BZ2
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testing "tar -k does not extract into symlinks" "\
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>>/tmp/passwd && uudecode -o input && tar xf input -k 2>&1 && rm passwd; cat /tmp/passwd; echo \$?
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" "\
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tar: skipping unsafe symlink to '/tmp/passwd' in archive, set EXTRACT_UNSAFE_SYMLINKS=1 to extract
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tar: can't create symlink 'passwd' to '/tmp/passwd'
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0
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" \
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"" "\
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@ -324,11 +324,11 @@ rm -rf etc usr
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' "\
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etc/ssl/certs/3b2716e5.0
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etc/ssl/certs/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.pem
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tar: skipping unsafe symlink to '/usr/share/ca-certificates/mozilla/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.crt' in archive, set EXTRACT_UNSAFE_SYMLINKS=1 to extract
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etc/ssl/certs/f80cc7f6.0
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usr/share/ca-certificates/mozilla/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.crt
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0
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etc/ssl/certs/3b2716e5.0 -> EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.pem
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etc/ssl/certs/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.pem -> /usr/share/ca-certificates/mozilla/EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.crt
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etc/ssl/certs/f80cc7f6.0 -> EBG_Elektronik_Sertifika_Hizmet_Sağlayıcısı.pem
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" \
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"" ""
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@ -346,9 +346,9 @@ ls symlink/bb_test_evilfile
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' "\
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anything.txt
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symlink
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tar: skipping unsafe symlink to '/tmp' in archive, set EXTRACT_UNSAFE_SYMLINKS=1 to extract
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symlink/bb_test_evilfile
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0
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tar: can't create symlink 'symlink' to '/tmp'
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1
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ls: /tmp/bb_test_evilfile: No such file or directory
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ls: bb_test_evilfile: No such file or directory
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symlink/bb_test_evilfile
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