diff -Naur open-iscsi-2.1.0.old/usr/auth.c open-iscsi-2.1.0.new/usr/auth.c
--- open-iscsi-2.1.0.old/usr/auth.c	2019-11-14 21:34:15.000000000 +0100
+++ open-iscsi-2.1.0.new/usr/auth.c	2019-12-27 10:45:45.162415149 +0100
@@ -182,9 +182,11 @@
 	case AUTH_CHAP_ALG_SHA256:
 		digest = EVP_sha256();
 		break;
+#ifndef LIBRESSL_VERSION_NUMBER
 	case AUTH_CHAP_ALG_SHA3_256:
 		digest = EVP_sha3_256();
 		break;
+#endif
 	}
 
 	if (*context == NULL)
@@ -335,7 +337,9 @@
 acl_chk_chap_alg_optn(int chap_algorithm)
 {
 	if (chap_algorithm == AUTH_OPTION_NONE ||
+#ifndef LIBRESSL_VERSION_NUMBER
 	    chap_algorithm == AUTH_CHAP_ALG_SHA3_256 ||
+#endif
 	    chap_algorithm == AUTH_CHAP_ALG_SHA256 ||
 	    chap_algorithm == AUTH_CHAP_ALG_SHA1 ||
 	    chap_algorithm == AUTH_CHAP_ALG_MD5)
@@ -748,9 +752,11 @@
 				case AUTH_CHAP_ALG_SHA256:
 					client->chap_challenge_len = AUTH_CHAP_SHA256_RSP_LEN;
 					break;
+#ifndef LIBRESSL_VERSION_NUMBER
 				case AUTH_CHAP_ALG_SHA3_256:
 					client->chap_challenge_len = AUTH_CHAP_SHA3_256_RSP_LEN;
 					break;
+#endif
 				}
 				return;
 			}
@@ -899,7 +905,10 @@
 			client->local_state = AUTH_LOCAL_STATE_ERROR;
 			client->dbg_status = AUTH_DBG_STATUS_CHAP_ALG_REJECT;
 			break;
-		} else if ((client->negotiated_chap_alg != AUTH_CHAP_ALG_SHA3_256) &&
+		} else if (
+#ifndef LIBRESSL_VERSION_NUMBER
+			   (client->negotiated_chap_alg != AUTH_CHAP_ALG_SHA3_256) &&
+#endif
 			   (client->negotiated_chap_alg != AUTH_CHAP_ALG_SHA256) &&
 			   (client->negotiated_chap_alg != AUTH_CHAP_ALG_SHA1) &&
 			   (client->negotiated_chap_alg != AUTH_CHAP_ALG_MD5)) {
@@ -1823,9 +1832,11 @@
 	EVP_MD_CTX *context = EVP_MD_CTX_new();
 	int i = 0;
 
+#ifndef LIBRESSL_VERSION_NUMBER
 	if (EVP_DigestInit_ex(context, EVP_sha3_256(), NULL)) {
 		value_list[i++] = AUTH_CHAP_ALG_SHA3_256;
 	}
+#endif
 	if (EVP_DigestInit_ex(context, EVP_sha256(), NULL)) {
 		value_list[i++] = AUTH_CHAP_ALG_SHA256;
 	}
diff -Naur open-iscsi-2.1.0.old/usr/auth.h open-iscsi-2.1.0.new/usr/auth.h
--- open-iscsi-2.1.0.old/usr/auth.h	2019-11-14 21:34:15.000000000 +0100
+++ open-iscsi-2.1.0.new/usr/auth.h	2019-12-27 10:41:56.864598431 +0100
@@ -67,8 +67,12 @@
 	AUTH_CHAP_ALG_MD5 = 5,
 	AUTH_CHAP_ALG_SHA1 = 6,
 	AUTH_CHAP_ALG_SHA256 = 7,
+#ifdef LIBRESSL_VERSION_NUMBER
+	AUTH_CHAP_ALG_MAX_COUNT = 4
+#else
 	AUTH_CHAP_ALG_SHA3_256 = 8,
 	AUTH_CHAP_ALG_MAX_COUNT = 5
+#endif
 };
 
 enum auth_neg_role {