From 42acb69fd1fdab9099833c946171eefc9b86ecde Mon Sep 17 00:00:00 2001
From: Vitezslav Cizek <vcizek@suse.com>
Date: Thu, 25 Oct 2018 13:53:26 +0200
Subject: [PATCH] DSA: Check for sanity of input parameters

dsa_builtin_paramgen2 expects the L parameter to be greater than N,
otherwise the generation will get stuck in an infinite loop.

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>

(cherry picked from commit 3afd38b277a806b901e039c6ad281c5e5c97ef67)

(Merged from https://github.com/openssl/openssl/pull/7493)
---
 crypto/dsa/dsa_gen.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/crypto/dsa/dsa_gen.c b/crypto/dsa/dsa_gen.c
index 46f4f01ee0..383d853b6d 100644
--- a/crypto/dsa/dsa_gen.c
+++ b/crypto/dsa/dsa_gen.c
@@ -327,6 +327,12 @@ int dsa_builtin_paramgen2(DSA *ret, size_t L, size_t N,
     if (mctx == NULL)
         goto err;
 
+    /* make sure L > N, otherwise we'll get trapped in an infinite loop */
+    if (L <= N) {
+        DSAerr(DSA_F_DSA_BUILTIN_PARAMGEN2, DSA_R_INVALID_PARAMETERS);
+        goto err;
+    }
+
     if (evpmd == NULL) {
         if (N == 160)
             evpmd = EVP_sha1();
-- 
2.25.1