Avoid overflow in MDC2_Update()

Thanks to Shi Lei for reporting this issue.

CVE-2016-6303

Reviewed-by: Matt Caswell <matt@openssl.org>
(cherry picked from commit 55d83bf7c10c7b205fffa23fa7c3977491e56c07)

diff --git a/crypto/mdc2/mdc2dgst.c b/crypto/mdc2/mdc2dgst.c
index 6615cf84d7d2a2f5607f810f41820db6bc745172..2dce4936337a03a4b6e06fbeb1fb4a8775ed7d9c 100644 (file)
--- a/crypto/mdc2/mdc2dgst.c
+++ b/crypto/mdc2/mdc2dgst.c
@@ -91,7 +91,7 @@ int MDC2_Update(MDC2_CTX *c, const unsigned char *in, size_t len)
 
     i = c->num;
     if (i != 0) {
-        if (i + len < MDC2_BLOCK) {
+        if (len < MDC2_BLOCK - i) {
             /* partial block */
             memcpy(&(c->data[i]), in, len);
             c->num += (int)len;