unzip: give better error message when presented with unsupported

 zip file. Add zip documentation and an example of file we cant
 (yet) unpack.

3 files changed, 6 insertions, 0 deletions

diff --git a/archival/unzip.c b/archival/unzip.c
index 7c92f5d..36490cb 100644
--- a/archival/unzip.c
+++ b/archival/unzip.c
@@ -99,6 +99,12 @@ static void unzip_create_leading_dirs(const char *fn)
 
 static void unzip_extract(zip_header_t *zip_header, int src_fd, int dst_fd)
 {
+	if (zip_header->formatted.flags & (0x0008|0x0001)) {
+		/* 0x0001 - encrypted */
+		/* 0x0008 - streaming. [u]cmpsize can be reliably gotten
+		 * only from Central Directory. See unzip_doc.txt */
+		bb_error_msg_and_die("zip flags 8 and 1 are not supported");
+	}
 	if (zip_header->formatted.method == 0) {
 		/* Method 0 - stored (not compressed) */
 		off_t size = zip_header->formatted.ucmpsize;
diff --git a/archival/unzip_cant_handle.odt b/archival/unzip_cant_handle.odt
new file mode 100644
index 0000000..715e4a9
--- /dev/null
+++ b/archival/unzip_cant_handle.odt
diff --git a/archival/unzip_doc.txt.bz2 b/archival/unzip_doc.txt.bz2
new file mode 100644
index 0000000..ab77d10
--- /dev/null
+++ b/archival/unzip_doc.txt.bz2