From ab8d56d05b773e499c86be874fd3f11f5950213c Mon Sep 17 00:00:00 2001
From: Tomas Mraz <tomas@openssl.org>
Date: Mon, 11 Jul 2022 12:49:56 +0200
Subject: [PATCH] speed: Always reset the outlen when calling EVP_PKEY_derive

Fixes #18768

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18777)
---
 apps/speed.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/apps/speed.c b/apps/speed.c
index 65220d31f1..3d9e747900 100644
--- a/apps/speed.c
+++ b/apps/speed.c
@@ -880,11 +880,14 @@ static int FFDH_derive_key_loop(void *args)
     loopargs_t *tempargs = *(loopargs_t **) args;
     EVP_PKEY_CTX *ffdh_ctx = tempargs->ffdh_ctx[testnum];
     unsigned char *derived_secret = tempargs->secret_ff_a;
-    size_t outlen = MAX_FFDH_SIZE;
     int count;
 
-    for (count = 0; COND(ffdh_c[testnum][0]); count++)
+    for (count = 0; COND(ffdh_c[testnum][0]); count++) {
+        /* outlen can be overwritten with a too small value (no padding used) */
+        size_t outlen = MAX_FFDH_SIZE;
+
         EVP_PKEY_derive(ffdh_ctx, derived_secret, &outlen);
+    }
     return count;
 }
 #endif /* OPENSSL_NO_DH */