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tar,unzip: postpone creation of symlinks with "suspicious" targets

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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
2018-02-20 15:57:45 +01:00
parent 95121d98e6
commit a84db18fc7
6 changed files with 71 additions and 82 deletions
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25
archival/unzip.c
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@@ -345,7 +345,9 @@ static void unzip_create_leading_dirs(const char *fn)
}
#if ENABLE_FEATURE_UNZIP_CDF
static void unzip_extract_symlink(zip_header_t *zip, const char *dst_fn)
static void unzip_extract_symlink(llist_t **symlink_placeholders,
zip_header_t *zip,
const char *dst_fn)
{
char *target;
@@ -370,15 +372,9 @@ static void unzip_extract_symlink(zip_header_t *zip, const char *dst_fn)
target[xstate.mem_output_size] = '\0';
#endif
}
if (!unsafe_symlink_target(target)) {
//TODO: libbb candidate
if (symlink(target, dst_fn)) {
/* shared message */
bb_perror_msg_and_die("can't create %slink '%s' to '%s'",
"sym", dst_fn, target
);
}
}
create_or_remember_symlink(symlink_placeholders,
target,
dst_fn);
free(target);
}
#endif
@@ -490,6 +486,9 @@ int unzip_main(int argc, char **argv)
llist_t *zaccept = NULL;
llist_t *zreject = NULL;
char *base_dir = NULL;
#if ENABLE_FEATURE_UNZIP_CDF
llist_t *symlink_placeholders = NULL;
#endif
int i;
char key_buf[80]; /* must match size used by my_fgets80 */
@@ -954,7 +953,7 @@ int unzip_main(int argc, char **argv)
#if ENABLE_FEATURE_UNZIP_CDF
if (S_ISLNK(file_mode)) {
if (dst_fd != STDOUT_FILENO) /* not -p? */
unzip_extract_symlink(&zip, dst_fn);
unzip_extract_symlink(&symlink_placeholders, &zip, dst_fn);
} else
#endif
{
@@ -990,6 +989,10 @@ int unzip_main(int argc, char **argv)
total_entries++;
}
#if ENABLE_FEATURE_UNZIP_CDF
create_symlinks_from_list(symlink_placeholders);
#endif
if ((opts & OPT_l) && quiet <= 1) {
if (!verbose) {
// " Length Date Time Name\n"