1 files changed, 12 insertions, 4 deletions

diff --git a/src/lib/libcrypto/ecdh/ech_ossl.c b/src/lib/libcrypto/ecdh/ech_ossl.c
index f05db87f78..746eb12ea3 100644
--- a/src/lib/libcrypto/ecdh/ech_ossl.c
+++ b/src/lib/libcrypto/ecdh/ech_ossl.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ech_ossl.c,v 1.10 2015/09/13 10:46:20 jsing Exp $ */
+/* $OpenBSD: ech_ossl.c,v 1.11 2015/09/13 11:49:44 jsing Exp $ */
 /* ====================================================================
  * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.
  *
@@ -115,7 +115,8 @@ ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
         unsigned char *buf = NULL;
 
         if (outlen > INT_MAX) {
-                ECDHerr(ECDH_F_ECDH_COMPUTE_KEY,ERR_R_MALLOC_FAILURE); /* sort of, anyway */
+                /* Sort of, anyway. */
+                ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
                 return -1;
         }
 
@@ -171,6 +172,11 @@ ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
                 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_INTERNAL_ERROR);
                 goto err;
         }
+        if (outlen < buflen) {
+                /* The resulting key would be truncated. */
+                ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_KEY_TRUNCATION);
+                goto err;
+        }
         if ((buf = malloc(buflen)) == NULL) {
                 ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);
                 goto err;
@@ -189,9 +195,11 @@ ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,
                 }
                 ret = outlen;
         } else {
-                /* no KDF, just copy as much as we can */
-                if (outlen > buflen)
+                /* No KDF, just copy as much as we can and zero the rest. */
+                if (outlen > buflen) {
+                        memset(out + buflen, 0, outlen - buflen);
                         outlen = buflen;
+                }
                 memcpy(out, buf, outlen);
                 ret = outlen;
         }