Enforce a strict output length check in CRYPTO_ccm128_tag

guidovranken · mattcaswell · commit fc4c034ee823 · 2019-04-25T11:00:39.000+01:00
Return error if the output tag buffer size doesn't match the tag size exactly. This prevents the caller from using that portion of the tag buffer that remains uninitialized after an otherwise succesfull call to CRYPTO_ccm128_tag. Bug found by OSS-Fuzz. Fix suggested by Kurt Roeckx. Signed-off-by: Guido Vranken <guidovranken@gmail.com> Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com> Reviewed-by: Paul Dale <paul.dale@oracle.com> Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from #8810) (cherry picked from commit 514c9da)
diff --git a/crypto/modes/ccm128.c b/crypto/modes/ccm128.c
@@ -425,7 +425,7 @@ size_t CRYPTO_ccm128_tag(CCM128_CONTEXT *ctx, unsigned char *tag, size_t len)
 
     M *= 2;
     M += 2;
-    if (len < M)
+    if (len != M)
         return 0;
     memcpy(tag, ctx->cmac.c, M);
     return M;
