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

This mostly reverts commit bc9bbeb2b81001e8731cd2ae501c8fccc8d87cc7
"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>

1 files changed, 14 insertions, 11 deletions

diff --git a/archival/unzip.c b/archival/unzip.c
index da4b2a5..0d00d8d 100644
--- a/archival/unzip.c
+++ b/archival/unzip.c
@@ -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"