1.\" $OpenBSD: SSL_set1_host.3,v 1.3 2021/01/27 17:57:40 tb Exp $ 2.\" selective merge up to: OpenSSL 6328d367 Jul 4 21:58:30 2020 +0200 3.\" 4.\" This file was written by Viktor Dukhovni <viktor@openssl.org> 5.\" Copyright (c) 2015 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. All advertising materials mentioning features or use of this 20.\" software must display the following acknowledgment: 21.\" "This product includes software developed by the OpenSSL Project 22.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 23.\" 24.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 25.\" endorse or promote products derived from this software without 26.\" prior written permission. For written permission, please contact 27.\" openssl-core@openssl.org. 28.\" 29.\" 5. Products derived from this software may not be called "OpenSSL" 30.\" nor may "OpenSSL" appear in their names without prior written 31.\" permission of the OpenSSL Project. 32.\" 33.\" 6. Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: January 27 2021 $ 52.Dt SSL_SET1_HOST 3 53.Os 54.Sh NAME 55.Nm SSL_set1_host 56.ig \" won't make Ox 6.8 but will appear in 6.9 57.Nm SSL_set_hostflags 58.Nm SSL_get0_peername 59.. 60.Nd SSL server verification parameters 61.Sh SYNOPSIS 62.In openssl/ssl.h 63.Ft int 64.Fo SSL_set1_host 65.Fa "SSL *ssl" 66.Fa "const char *hostname" 67.Fc 68.ig 69.Ft void 70.Fo SSL_set_hostflags 71.Fa "SSL *ssl" 72.Fa "unsigned int flags" 73.Fc 74.Ft const char * 75.Fo SSL_get0_peername 76.Fa "SSL *ssl" 77.Fc 78.. 79.Sh DESCRIPTION 80.Fn SSL_set1_host 81configures a server hostname check in the 82.Fa ssl 83client, setting the expected DNS hostname to 84.Fa hostname 85and clearing any previously specified hostname. 86If 87.Fa hostname 88is 89.Dv NULL 90or the empty string, name checks are not performed on the peer certificate. 91If a nonempty 92.Fa hostname 93is specified, certificate verification automatically checks the peer 94hostname via 95.Xr X509_check_host 3 96with 97.Fa flags 98set to 0. 99.Pp 100.ig 101.Fn SSL_set_hostflags 102sets the flags that will be passed to 103.Xr X509_check_host 3 104when name checks are applicable, 105by default the flags value is 0. 106See 107.Xr X509_check_host 3 108for the list of available flags and their meaning. 109.Pp 110.Fn SSL_get0_peername 111returns the DNS hostname or subject CommonName from the peer certificate 112that matched one of the reference identifiers. 113Unless wildcard matching is disabled, the name matched in the peer 114certificate may be a wildcard name. 115A reference identifier starting with 116.Sq \&. 117indicates a parent domain prefix rather than a fixed name. 118In this case, the matched peername may be a sub-domain 119of the reference identifier. 120The returned string is owned by the library and is no longer valid 121once the associated 122.Fa ssl 123object is cleared or freed, or if a renegotiation takes place. 124Applications must not free the return value. 125.Pp 126SSL clients are advised to use these functions in preference to 127.. 128SSL clients are advised to use this function in preference to 129explicitly calling 130.Xr X509_check_host 3 . 131.Sh RETURN VALUES 132.Fn SSL_set1_host 133returns 1 for success or 0 for failure. 134.ig 135.Pp 136.Fn SSL_get0_peername 137returns the matched peername or 138.Dv NULL 139if peername verification is not applicable 140or no trusted peername was matched. 141Use 142.Xr SSL_get_verify_result 3 143to determine whether verification succeeded. 144.Sh EXAMPLES 145The calls below check the hostname. 146Wildcards are supported, but they must match the entire label. 147The actual name matched in the certificate (which might be a wildcard) 148is retrieved, and must be copied by the application if it is to be 149retained beyond the lifetime of the SSL connection. 150.Bd -literal 151if (!SSL_set1_host(ssl, "smtp.example.com")) 152 /* error */ 153 154/* XXX: Perform SSL_connect() handshake and handle errors here */ 155 156if (SSL_get_verify_result(ssl) == X509_V_OK) { 157 const char *peername = SSL_get0_peername(ssl); 158 159 if (peername != NULL) 160 /* Name checks were in scope and matched the peername */ 161} 162.Ed 163.. 164.Sh SEE ALSO 165.Xr ssl 3 , 166.Xr SSL_CTX_set_verify 3 , 167.Xr SSL_get_peer_certificate 3 , 168.Xr SSL_get_verify_result 3 , 169.Xr X509_check_host 3 , 170.Xr X509_VERIFY_PARAM_set1_host 3 171.Sh HISTORY 172This function first appeared in OpenSSL 1.1.0 173and has been available since 174.Ox 6.5 . 175.ig 176All three functions first appeared in OpenSSL 1.1.0. 177.Fn SSL_set1_host 178has been available since 179.Ox 6.5 , 180and 181.Fn SSL_set_hostflags 182and 183.Fn SSL_get0_peername 184since 185.Ox 6.9 . 186.. 187