Subject: [PATCH] extract: prevent unsigned overflow on invalid input
From: Kamil Dudka <[email-masked]>
Date: Tue, 22 Sep 2015 18:52:23 +0200

Suggested-by: Stefan Cornelius
---
 extract.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/extract.c
+++ b/extract.c
@@ -1257,8 +1257,17 @@
         if (G.lrec.compression_method == STORED) {
             zusz_t csiz_decrypted = G.lrec.csize;
 
-            if (G.pInfo->encrypted)
+            if (G.pInfo->encrypted) {
+                if (csiz_decrypted < 12) {
+                    /* handle the error now to prevent unsigned overflow */
+                    Info(slide, 0x401, ((char *)slide,
+                      LoadFarStringSmall(ErrUnzipNoFile),
+                      LoadFarString(InvalidComprData),
+                      LoadFarStringSmall2(Inflate)));
+                    return PK_ERR;
+                }
                 csiz_decrypted -= 12;
+            }
             if (G.lrec.ucsize != csiz_decrypted) {
                 Info(slide, 0x401, ((char *)slide,
                   LoadFarStringSmall2(WrnStorUCSizCSizDiff),