.\" $NetBSD: hmac.3,v 1.5 2016/07/02 16:04:47 wiz Exp $ .\" .\" Copyright (c) 2016 The NetBSD Foundation, Inc. .\" All rights reserved. .\" .\" This code is derived from software contributed to The NetBSD Foundation .\" by Christos Zoulas. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS .\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED .\"TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS .\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS .\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN .\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE .\" POSSIBILITY OF SUCH DAMAGE. .\" .Dd July 1, 2016 .Dt HMAC 3 .Os .Sh NAME .Nm hmac .Nd compute a key-Hash Message Authentication Code .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In stdlib.h .Ft ssize_t .Fn hmac "const char *hname" "const void *key" "size_t klen" "const void *text" "size_t tlen" "void *digest" "size_t dlen" .Sh DESCRIPTION The .Fn hmac function computes the key-Hash Message Authentication Code per .Tn RFC 2104 and places the result in .Fa digest writing up to .Fa dlen bytes. The actual number of bytes that would be written is returned. .Pp The hash functions supported are: md2, md4, md5, rmd160, sha1, sha224, sha256, sha384, and sha512. .Sh RETURN VALUES The .Fn hmac function returns .Dv \-1 if the .Fa hname is not found. Otherwise the actual length of the digest string is returned (which could be bigger or smaller than .Fa dlen ) . This length depends on the hashing function selected. .Sh SEE ALSO .Xr md2 3 , .Xr md4 3 , .Xr md5 3 , .Xr rmd160 3 , .Xr sha1 3 , .Xr sha2 3 .Sh STANDARDS .Rs .%R RFC 2104 .Re .Sh NOTES The maximum digest length has been extended from .Dv 64 to .Dv 128 bytes to handle SHA2. .Sh HISTORY The .Fn hmac function appeared in .Nx 8 .