libarchive: do not extract unsafe symlinks unless $EXTRACT_UNSAFE_SYMLINKS=1
function old new delta unsafe_symlink_target - 147 +147 unzip_main 2711 2732 +21 copy_file 1657 1678 +21 tar_main 999 971 -28 data_extract_all 1038 984 -54 ------------------------------------------------------------------------------ (add/remove: 2/0 grow/shrink: 2/2 up/down: 189/-82) Total: 107 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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@@ -129,9 +129,7 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
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if (res != 0 && !(archive_handle->ah_flags & ARCHIVE_EXTRACT_QUIET)) {
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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",
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dst_name,
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hard_link
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"hard", dst_name, hard_link
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);
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}
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/* Hardlinks have no separate mode/ownership, skip chown/chmod */
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@@ -181,7 +179,9 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
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//TODO: what if file_header->link_target == NULL (say, corrupted tarball?)
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/* To avoid a directory traversal attack via symlinks,
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* for certain link targets postpone creation of symlinks.
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* do not restore symlinks with ".." components
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* or symlinks starting with "/", unless a magic
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* envvar is set.
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*
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* For example, consider a .tar created via:
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* $ tar cvf bug.tar anything.txt
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@@ -199,24 +199,17 @@ 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 (file_header->link_target[0] == '/'
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|| strstr(file_header->link_target, "..")
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) {
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llist_add_to(&archive_handle->symlink_placeholders,
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xasprintf("%s%c%s", file_header->name, '\0', file_header->link_target)
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);
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break;
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}
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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,
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file_header->link_target
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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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break;
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case S_IFSOCK:
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